Dental panoramic radiographs are often obtained at dental clinic visits for diagnosis and recording purposes. Automated filing of dental charts can help dentists in reducing their workload and improving diagnostic efficiency. The purpose of this study is to develop a system that prerecords a dental chart by recognizing teeth with their numbers and restoration history on dental panoramic radiographs. The proposed system uses YOLO which detects 16 types of teeth and restoration conditions simultaneously. Based on the detected tooth types, they were further classified into 32 types and combined with the tooth conditions by post-processing. We tested our method on 870 panoramic images obtained at 10 different facilities by 5-fold cross validation. The proposed method obtained 0.99 recall and precision for recognition of 32 tooth types and 0.90 recall and 0.90 precision on determining the tooth condition. It has the potential to assist prefiling the dental charts for efficient dental care.
Purpose: The purpose of our study was to analyze dental panoramic radiographs and contribute to dentists’ diagnosis by automatically extracting the information necessary for reading them. As the initial step, we detected teeth and classified their tooth types in this study.
Approach: We propose single-shot multibox detector (SSD) networks with a side branch for 1-class detection without distinguishing the tooth type and for 16-class detection (i.e., the central incisor, lateral incisor, canine, first premolar, second premolar, first molar, second molar, and third molar, distinguished by the upper and lower jaws). In addition, post-processing was conducted to integrate the results of the two networks and categorize them into 32 classes, differentiating between the left and right teeth. The proposed method was applied to 950 dental panoramic radiographs obtained at multiple facilities, including a university hospital and dental clinics.
Results: The recognition performance of the SSD with a side branch was better than that of the original SSD. In addition, the detection rate was improved by the integration process. As a result, the detection rate was 99.03%, the number of false detections was 0.29 per image, and the classification rate was 96.79% for 32 tooth types.
Conclusions: We propose a method for tooth recognition using object detection and post-processing. The results show the effectiveness of network branching on the recognition performance and the usefulness of post-processing for neural network output.
The body cavity region contains organs and is an essential region for skeletal muscle segmentation. This study proposes a method to segment body cavity regions using U-Net with focus on the oblique abdominal muscles. The proposed method comprises two steps. First, the body cavity is segmented using U-Net. Subsequently, the abdominal muscles are identified using recognition techniques. This is achieved by removing the segmented body cavity region from the original computerized tomography (CT) images to obtain a simplified CT image for training. In this image, the visceral organ regions are masked by the body cavity; ensuring that the organs therein are excluded from the segmentation target in advance which has been a primary concern in the conventional method of skeletal muscle segmentation. The segmentation accuracies of the body cavity and oblique abdominal muscle in 16 cases were 98.50% and 84.89%, respectively, in terms of the average dice value. Furthermore, it was observed that body cavity information reduced the number of over-extracted pixels by 36.21% in the segmentation of the oblique abdominal muscles adjacent to the body cavity, improving the segmentation accuracy. In future studies, it could be beneficial to examine whether the proposed simplification of CT images by segmentation of body cavities is also effective for abdominal musculoskeletal muscles adjacent to body cavities divided by tendon ends, such as the rectus abdominis.
The diagnosis using a time-intensity curve (TIC) is considered to be useful in the differentiation of pancreatic tumors. TIC is a graph that shows a contrast intensity of contrast-enhanced endoscopic ultrasonography over time. We propose a method to classify pancreatic tumors, which generates and uses two types of images representing a contrast effect from ultrasound endoscopic images. The first type is a two-dimensional histogram that adds information about a distribution of luminance values per frame to TIC which features a contrast effect over time. The second type is a frame with the highest average luminance value among all frames of each case. The frame featured a contrast enhancement pattern of the tumor. The features of the two images were extracted using deep learning. The two extracted features were combined by a concatenate layer. The combined feature outputs by a fully connected layer as the probability of pancreatic cancer. In this study, 131 cases with pancreatic tumors (pancreatic cancer: 86 cases, non-pancreatic cancer: 45 cases) were used. As a result of receiver operating characteristic analysis of the output probability, the area under the curve was 0.82, the sensitivity was 80.2%, and the specificity was 71.1%.
The purpose of this study is to analyze dental panoramic radiographs for completing dental files to contribute to the diagnosis by dentists. In this study, we recognized 32 tooth types and classified four tooth attributes (tooth, remaining root, pontic, and implant) using 925 dental panoramic radiographs. YOLOv4 and post-processing were used for the recognition of 32 tooth types. As a result, the tooth detection recall was 99.65%, the number of false positives was 0.10 per image, and the 32-type recognition recall was 98.55%. For the classification of the four tooth attributes, two methods were compared. In Method 1, image classification was performed using a clipped image based on the tooth detection result. In Method 2, the labels of tooth attributes were added to the labels of tooth types in object detection. By providing two labels for the same bounding box, we performed multi-label object detection. The accuracy of Method 1 was 0.995 and that of Method 2 was 0.990. Method 2 uses a simple and robust model yet has comparable accuracy as Method 1. In addition, Method 2 did not require additional CNN models. This suggested the usefulness of multi-label detection.
Supervised learning for image segmentation requires annotated images. However, image annotation has the problem that it is time-consuming. This problem is particularly significant in the erector spinae muscle segmentation due to the large size of the muscle. Therefore, this study considers the relationship between the number of annotated images used for training and segmentation accuracy of the erector spinae muscle in torso CT images. We use Bayesian U-Net, which has shown high accuracy in thigh muscle segmentation, for the segmentation of the erector spinae muscle. In the network training, we limit the number of slices for each case and the number of cases to 100%, 50%, 25%, and 10%. In the experiment, we use 30 torso CT images, including 6 cases for the test dataset. Experimental results are evaluated by the mean Dice value of the test dataset. Using 100% of the slices per case, the segmentation accuracy with 100%, 50%, 25%, and 10% of the cases was 0.934, 0.927, 0.926, and 0.890, respectively. On the other hand, using 100% of the cases, the segmentation accuracy with 100%, 50%, 25%, and 10% of the slices per case was 0.934, 0.934, 0.933, and 0.931, respectively. Furthermore, the segmentation accuracy with 100% of the cases and 10% of the slices per case was higher than that of the previous method. We showed that it is feasible to achieve high segmentation accuracy with a limited number of annotated images by selecting several slices from a limited number of cases for training.
The purpose of this study is to analyze dental panoramic radiographs for completing dental files to contribute to the diagnosis by dentists. As the initial stage, we detected each tooth and classified its tooth type. Since the final goal of this study includes multiple tasks, such as determination of dental conditions and recognition of lesions, we proposed a multitask training based on a Single Shot Multibox Detector (SSD) with a branch to predict the presence or absence of a tooth. The results showed that the proposed model improved the detection rate by 1.0%, the number of false positives per image by 0.03, and the detection rate by tooth type (total number of successfully detected and classified teeth/total number of teeth) by 1.6% compared with the original SSD, suggesting the effectiveness of the multi-task learning in dental panoramic radiographs. In addition, we integrated results of single-class detection without distinguishing the tooth type and 16-class (central incisor, lateral incisor, canine, first premolar, second premolar, first molar, second molar, third molar, distinguished by upper and lower jaws) detection for improving the detection rate and included post-processing for classification of teeth into 32 types and correction of tooth numbering. As a result, the detection rate of 98.8%, 0.33 false positives per image, and classification rate of 92.4% for 32 tooth types were archived.
We propose an approach for the automatic segmentation of mammary gland regions on 3D CT images, aiming to accomplish breast cancer risk assessment through CT scans acquired in clinical medicine for various diagnostic purposes. The proposed approach uses a hybrid method that embeds a deep-learning-based attention mechanism as a module into a conventional framework, which originally uses a probabilistic atlas to accomplish Bayesian inference to estimate the pixelwise probability of mammary gland regions on CT images. In this work, we replace both the construction and application of a probabilistic atlas, which is time-consuming and complicated to realize, by a visual explanation from the attention mechanism of a classifier learned through weak supervision. In the experiments, we applied the proposed approach to the segmentation of mammary gland regions based on 174 torso CT scans and evaluated its performance by comparing the segmentation results to human sketches on 14 CT cases. The experimental results showed that the attention maps of the classifier successfully focused on the mammary gland regions on the CT images and could replace the atlas for supporting mammary gland segmentation. The preliminary results on 14 test CT scans showed that the mammary gland regions were segmented successfully with a mean value of 50.6% on the Dice similarity coefficient against the human sketches. We confirmed that the proposed approach, combining deep learning and conventional methods, shows a higher computing efficiency, much better robustness, and easier implementation than our previous approach based on a probabilistic atlas.
Dental record plays an important role in dental diagnosis and personal identification. Automatic image preinterpretation can help reducing dentists’ workload and improving diagnostic efficiency. Systematic dental record filing enables effective utilization of accumulated records at dental clinics for forensic identification. We have been investigating a tooth labeling method on dental cone-beam CT images for the purpose of automatic filing of dental charts. In our previous method, two separate networks were employed for detection and classification of teeth. Although detection accuracy was promising, classification performance had a room of improvement. The purpose of this study was to investigate the use of the relation network to utilize information of positional relationship between teeth for the detection and classification. Using the proposed method, both detection and classification performance improved. Especially, the tooth type classification accuracy improved. The proposed method can be useful in automatic filing of the dental chart.
In the dopamine nerves of the nigrostriatal body in the brain, 123I-FP-CIT binds to dopamine transporter (DAT), the distribution of which can be visualized on a single photon-emission computed tomography (SPECT) image. The Tossici-Bolt method is generally used to analyze SPECT images. However, since the Tossici-Bolt method uses a fixed region of interest, it is susceptible to the influence of non-accumulated parts. Magnetic resonance (MR) images are effective for recognizing the shape of the striatal region. Here we used MR images generated by deep learning from low-dose CT images taken with SPECT/CT devices. The purpose of this study was to perform a quantitative analysis with high repeatability using the striatal region extracted from automatically generated MR images. First, an MR image was generated from a CT image by pix2pix. After that, a striatal region was extracted from the generated MR image by PSPNet[3]. A quantitative analysis using specific binding ratio was performed using this region. For the experiments, 60 clinical cases of SPECT/CT and MR images were used. The specific binding ratios calculated by this method and the Tossici-Bolt method were compared. As a result, better results than with the Tossici-Bolt method were calculated in 12 cases. Therefore, generating MR images from low-dose CT images and segmentation by deep learning may contribute to quantitative analysis with high reproducibility of DAT imaging.
The skeletal muscle exists in the whole body and can be observed in many cross sections in various tomographic images. Skeletal muscle atrophy is due to aging and disease, and the abnormality is difficult to distinguish visually. In addition, although skeletal muscle analysis requires a technique for accurate site-specific measurement of skeletal muscle, it is only realized in a limited region. We realized automatic site-specific recognition of skeletal muscle from whole-body CT images using model-based methods. Three-dimensional texture analysis revealed imaging features with statistically significant differences between amyotrophic lateral sclerosis (ALS) and other muscular diseases accompanied by atrophy. In recent years, deep learning technique is also used in the field of computer-aided diagnosis. Therefore, in this initial study, we performed automatic classification of amyotrophic diseases using deep learning for the upper extremity and lower limb regions. The classification accuracy was highest in the right forearm, which was 0.960 at the maximum (0.903 on average). In the future, methods for differentiating more kinds of muscular atrophy and clinical application of ALS detection by analyzing muscular regions must be considered.
This paper proposes a novel method to learn a 3D non-rigid deformation for automatic image registration between Positron Emission Tomography (PET) and Computed Tomography (CT) scans obtained from the same patient. There are two modules in the proposed scheme including (1) low-resolution displacement vector field (LR-DVF) estimator, which uses a 3D deep convolutional network (ConvNet) to directly estimate the voxel-wise displacement (a 3D vector field) between PET/CT images, and (2) 3D spatial transformer and re-sampler, which warps the PET images to match the anatomical structures in the CT images using the estimated 3D vector field. The parameters of the ConvNet are learned from a number of PET/CT image pairs via an unsupervised learning method. The Normalized Cross Correlation (NCC) between PET/CT images is used as the similarity metric to guide an end-to-end learning process with a constraint (regular term) to preserve the smoothness of the 3D deformations. A dataset with 170 PET/CT scans is used in experiments based on 10-fold cross-validation, where a total of 22,338 3D patches are sampled from the dataset. In each fold, 3D patches from 153 patients (90%) are used for training the parameters, while the remaining whole-body voxels from 17 patients (10%) are used for testing the performance of the image registration. The experimental results demonstrate that the image registration accuracy (the mean value of NCCs) is increased from 0.402 (the initial situation) to 0.567 on PET/CT scans using the proposed scheme. We also compare the performance of our scheme with previous work (DIRNet) and the advantage of our scheme is confirmed via the promising results.
We propose an automatic approach to anatomy partitioning on three-dimensional (3D) computed tomography (CT) images that divides the human torso into several volumes of interest (VOIs) according to anatomical definition. In the proposed approach, a deep convolutional neural network (CNN) is trained to automatically detect the bounding boxes of organs on two-dimensional (2D) sections of CT images. The coordinates of those boxes are then grouped so that a vote on a 3D VOI (called localization) for each organ can be obtained separately. We applied this approach to localize the 3D VOIs of 17 types of organs in the human torso and then evaluated the performance of the approach by conducting a four-fold crossvalidation using a dataset consisting of 240 3D CT scans with the human-annotated ground truth for each organ region. The preliminary results showed that 86.7% of the 3D VOIs of the 3177 organs in the 240 test CT images were localized with acceptable accuracy (mean of Jaccard indexes was 72.8%) compared to that of the human annotations. This performance was better than that of the state-of-the-art method reported recently. The experimental results demonstrated that using a deep CNN for anatomy partitioning on 3D CT images was more efficient and useful compared to the method used in our previous work.
The purpose of this study is to evaluate and compare the performance of modern deep learning techniques for automatically recognizing and segmenting multiple organ regions on 3D CT images. CT image segmentation is one of the important task in medical image analysis and is still very challenging. Deep learning approaches have demonstrated the capability of scene recognition and semantic segmentation on nature images and have been used to address segmentation problems of medical images. Although several works showed promising results of CT image segmentation by using deep learning approaches, there is no comprehensive evaluation of segmentation performance of the deep learning on segmenting multiple organs on different portions of CT scans. In this paper, we evaluated and compared the segmentation performance of two different deep learning approaches that used 2D- and 3D deep convolutional neural networks (CNN) without- and with a pre-processing step. A conventional approach that presents the state-of-the-art performance of CT image segmentation without deep learning was also used for comparison. A dataset that includes 240 CT images scanned on different portions of human bodies was used for performance evaluation. The maximum number of 17 types of organ regions in each CT scan were segmented automatically and compared to the human annotations by using ratio of intersection over union (IU) as the criterion. The experimental results demonstrated the IUs of the segmentation results had a mean value of 79% and 67% by averaging 17 types of organs that segmented by a 3D- and 2D deep CNN, respectively. All the results of the deep learning approaches showed a better accuracy and robustness than the conventional segmentation method that used probabilistic atlas and graph-cut methods. The effectiveness and the usefulness of deep learning approaches were demonstrated for solving multiple organs segmentation problem on 3D CT images.
This paper describes a novel approach for the automatic assessment of breast density in non-contrast three-dimensional computed tomography (3D CT) images. The proposed approach trains and uses a deep convolutional neural network (CNN) from scratch to classify breast tissue density directly from CT images without segmenting the anatomical structures, which creates a bottleneck in conventional approaches. Our scheme determines breast density in a 3D breast region by decomposing the 3D region into several radial 2D-sections from the nipple, and measuring the distribution of breast tissue densities on each 2D section from different orientations. The whole scheme is designed as a compact network without the need for post-processing and provides high robustness and computational efficiency in clinical settings. We applied this scheme to a dataset of 463 non-contrast CT scans obtained from 30- to 45-year-old-women in Japan. The density of breast tissue in each CT scan was assigned to one of four categories (glandular tissue within the breast <25%, 25%–50%, 50%–75%, and >75%) by a radiologist as ground truth. We used 405 CT scans for training a deep CNN and the remaining 58 CT scans for testing the performance. The experimental results demonstrated that the findings of the proposed approach and those of the radiologist were the same in 72% of the CT scans among the training samples and 76% among the testing samples. These results demonstrate the potential use of deep CNN for assessing breast tissue density in non-contrast 3D CT images.
In large disasters, dental record plays an important role in forensic identification. However, filing dental charts for corpses is not an easy task for general dentists. Moreover, it is laborious and time-consuming work in cases of large scale disasters. We have been investigating a tooth labeling method on dental cone-beam CT images for the purpose of automatic filing of dental charts. In our method, individual tooth in CT images are detected and classified into seven tooth types using deep convolutional neural network. We employed the fully convolutional network using AlexNet architecture for detecting each tooth and applied our previous method using regular AlexNet for classifying the detected teeth into 7 tooth types. From 52 CT volumes obtained by two imaging systems, five images each were randomly selected as test data, and the remaining 42 cases were used as training data. The result showed the tooth detection accuracy of 77.4% with the average false detection of 5.8 per image. The result indicates the potential utility of the proposed method for automatic recording of dental information.
Amyotrophic lateral sclerosis (ALS) causes functional disorders such as difficulty in breathing and swallowing through the atrophy of voluntary muscles. ALS in its early stages is difficult to diagnose because of the difficulty in differentiating it from other muscular diseases. In addition, image inspection methods for aggressive diagnosis for ALS have not yet been established. The purpose of this study is to develop an automatic analysis system of the whole skeletal muscle to support the early differential diagnosis of ALS using whole-body CT images. In this study, the muscular atrophy parts including ALS patients are automatically identified by recognizing and segmenting whole skeletal muscle in the preliminary steps. First, the skeleton is identified by its gray value information. Second, the initial area of the body cavity is recognized by the deformation of the thoracic cavity based on the anatomical segmented skeleton. Third, the abdominal cavity boundary is recognized using ABM for precisely recognizing the body cavity. The body cavity is precisely recognized by non-rigid registration method based on the reference points of the abdominal cavity boundary. Fourth, the whole skeletal muscle is recognized by excluding the skeleton, the body cavity, and the subcutaneous fat. Additionally, the areas of muscular atrophy including ALS patients are automatically identified by comparison of the muscle mass. The experiments were carried out for ten cases with abnormality in the skeletal muscle. Global recognition and segmentation of the whole skeletal muscle were well realized in eight cases. Moreover, the areas of muscular atrophy including ALS patients were well identified in the lower limbs. As a result, this study indicated the basic technology to detect the muscle atrophy including ALS. In the future, it will be necessary to consider methods to differentiate other kinds of muscular atrophy as well as the clinical application of this detection method for early ALS detection and examine a large number of cases with stage and disease type.
We have proposed an end-to-end learning approach that trained a deep convolutional neural network (CNN) for
automatic CT image segmentation, which accomplished a voxel-wised multiple classification to directly map each voxel
on 3D CT images to an anatomical label automatically. The novelties of our proposed method were (1) transforming the
anatomical structures segmentation on 3D CT images into a majority voting of the results of 2D semantic image
segmentation on a number of 2D-slices from different image orientations, and (2) using “convolution” and “deconvolution”
networks to achieve the conventional “coarse recognition” and “fine extraction” functions which were
integrated into a compact all-in-one deep CNN for CT image segmentation. The advantage comparing to previous works
was its capability to accomplish real-time image segmentations on 2D slices of arbitrary CT-scan-range (e.g. body, chest,
abdomen) and produced correspondingly-sized output. In this paper, we propose an improvement of our proposed
approach by adding an organ localization module to limit CT image range for training and testing deep CNNs. A
database consisting of 240 3D CT scans and a human annotated ground truth was used for training (228 cases) and
testing (the remaining 12 cases). We applied the improved method to segment pancreas and left kidney regions,
respectively. The preliminary results showed that the accuracies of the segmentation results were improved significantly
(pancreas was 34% and kidney was 8% increased in Jaccard index from our previous results). The effectiveness and
usefulness of proposed improvement for CT image segmentations were confirmed.
Important features in Parkinson's disease (PD) are degenerations and losses of dopamine neurons in corpus striatum. 123I-FP-CIT can visualize activities of the dopamine neurons. The activity radio of background to corpus striatum is used for diagnosis of PD and Dementia with Lewy Bodies (DLB). The specific activity can be observed in the corpus striatum on SPECT images, but the location and the shape of the corpus striatum on SPECT images only are often lost because of the low uptake. In contrast, MR images can visualize the locations of the corpus striatum. The purpose of this study was to realize a quantitative image analysis for the SPECT images by using image registration technique with brain MR images that can determine the region of corpus striatum. In this study, the image fusion technique was used to fuse SPECT and MR images by intervening CT image taken by SPECT/CT. The mutual information (MI) for image registration between CT and MR images was used for the registration. Six SPECT/CT and four MR scans of phantom materials are taken by changing the direction. As the results of the image registrations, 16 of 24 combinations were registered within 1.3mm. By applying the approach to 32 clinical SPECT/CT and MR cases, all of the cases were registered within 0.86mm. In conclusions, our registration method has a potential in superimposing MR images on SPECT images.
The iliac muscle is an important skeletal muscle related to ambulatory function. The muscles related to ambulatory function are the psoas major and iliac muscles, collectively defined as the iliopsoas muscle. We have proposed an automated recognition method of the iliac muscle. Muscle fibers of the iliac muscle have a characteristic running pattern. Therefore, we used 20 cases from a training database to model the movement of the muscle fibers of the iliac muscle. In the recognition process, the existing position of the iliac muscle was estimated by applying the muscle fiber model. To generate an approximation mask by using a muscle fiber model, a candidate region of the iliac muscle was obtained. Finally, the muscle region was identified by using values from the gray value and boundary information. The experiments were performed by using the 20 cases without abnormalities in the skeletal muscle for modeling. The recognition result in five cases obtained a 76.9% average concordance rate. In the visual evaluation, overextraction of other organs was not observed in 85% of the cases. Therefore, the proposed method is considered to be effective in the recognition of the initial region of the iliac muscle. In the future, we will integrate the recognition method of the psoas major muscle in developing an analytical technique for the iliopsoas area. Furthermore, development of a sophisticated muscle function analysis method is necessary.
This paper describes a brand new automatic segmentation method for quantifying volume and density of mammary gland regions on non-contrast CT images. The proposed method uses two processing steps: (1) breast region localization, and (2) breast region decomposition to accomplish a robust mammary gland segmentation task on CT images. The first step detects two minimum bounding boxes of left and right breast regions, respectively, based on a machine-learning approach that adapts to a large variance of the breast appearances on different age levels. The second step divides the whole breast region in each side into mammary gland, fat tissue, and other regions by using spectral clustering technique that focuses on intra-region similarities of each patient and aims to overcome the image variance caused by different scan-parameters. The whole approach is designed as a simple structure with very minimum number of parameters to gain a superior robustness and computational efficiency for real clinical setting. We applied this approach to a dataset of 300 CT scans, which are sampled with the equal number from 30 to 50 years-old-women. Comparing to human annotations, the proposed approach can measure volume and quantify distributions of the CT numbers of mammary gland regions successfully. The experimental results demonstrated that the proposed approach achieves results consistent with manual annotations. Through our proposed framework, an efficient and effective low cost clinical screening scheme may be easily implemented to predict breast cancer risk, especially on those already acquired scans.
This paper describes an automatic approach for anatomy partitioning on three-dimensional (3D) computedtomography (CT) images that divide the human torso into several volume-of-interesting (VOI) images based on anatomical definition. The proposed approach combines several individual detections of organ-location with a groupwise organ-location calibration and correction to achieve an automatic and robust multiple-organ localization task. The essence of the proposed method is to jointly detect the 3D minimum bounding box for each type of organ shown on CT images based on intra-organ-image-textures and inter-organ-spatial-relationship in the anatomy. Machine-learning-based template matching and generalized Hough transform-based point-distribution estimation are used in the detection and calibration processes. We apply this approach to the automatic partitioning of a torso region on CT images, which are divided into 35 VOIs presenting major organ regions and tissues required by routine diagnosis in clinical medicine. A database containing 4,300 patient cases of high-resolution 3D torso CT images is used for training and performance evaluations. We confirmed that the proposed method was successful in target organ localization on more than 95% of CT cases. Only two organs (gallbladder and pancreas) showed a lower success rate: 71 and 78% respectively. In addition, we applied this approach to another database that included 287 patient cases of whole-body CT images scanned for positron emission tomography (PET) studies and used for additional performance evaluation. The experimental results showed that no significant difference between the anatomy partitioning results from those two databases except regarding the spleen. All experimental results showed that the proposed approach was efficient and useful in accomplishing localization tasks for major organs and tissues on CT images scanned using different protocols.
MIBG (iodine-123-meta-iodobenzylguanidine) is a radioactive medicine that is used to help diagnose not only myocardial diseases but also Parkinson’s diseases (PD) and dementia with Lewy Bodies (DLB). The difficulty of the segmentation around the myocardium often reduces the consistency of measurement results. One of the most common measurement methods is the ratio of the uptake values of the heart to mediastinum (H/M). This ratio will be a stable independent of the operators when the uptake value in the myocardium region is clearly higher than that in background, however, it will be unreliable indices when the myocardium region is unclear because of the low uptake values. This study aims to develop a new measurement method by using the image fusion of three modalities of MIBG scintigrams, 201-Tl scintigrams, and chest radiograms, to increase the reliability of the H/M measurement results. Our automated method consists of the following steps: (1) construct left ventricular (LV) map from 201-Tl myocardium image database, (2) determine heart region in chest radiograms, (3) determine mediastinum region in chest radiograms, (4) perform image fusion of chest radiograms and MIBG scintigrams, and 5) perform H/M measurements on MIBG scintigrams by using the locations of heart and mediastinum determined on the chest radiograms. We collected 165 cases with 201-Tl scintigrams and chest radiograms to construct the LV map. Another 65 cases with MIBG scintigrams and chest radiograms were also collected for the measurements. Four radiological technologists (RTs) manually measured the H/M in the MIBG images. We compared the four RTs’ results with our computer outputs by using Pearson’s correlation, the Bland-Altman method, and the equivalency test method. As a result, the correlations of the H/M between four the RTs and the computer were 0.85 to 0.88. We confirmed systematic errors between the four RTs and the computer as well as among the four RTs. The variation range of the H/M among the four RTs was obtained as 0.22 based on the equivalency test method. The computer outputs were existed within this range. We concluded that our image fusion method could measure equivalent values between the system and the RTs.
Several studies have reported the presence of carotid artery calcifications (CACs) on dental panoramic radiographs (DPRs) as a possible sign of arteriosclerotic diseases. However, CACs are not easily visible at the common window level for dental examinations, and dentists, in general, are not looking for CACs. Computerized detection of CACs may help dentists in referring patients with a risk of arteriosclerotic diseases to have a detailed examination at a medical clinic. Downside of our previous method was a relatively large number of false positives (FPs). In this study, we attempted to reduce FPs by including an additional feature and selecting effective features for the classifier. A hundred DPRs including 34 cases with calcifications were included. Initial candidates were detected by thresholding the output of top-hat operation. For each candidate, 10 features and a new feature characterizing the relative position of a CAC with reference to the lower mandible edge were determined. After the rule-based FP reduction, candidates were classified into CACs and FPs by a support vector machine. Based on the leave-one-out cross-validation evaluations, an average number of FPs was 3.1 per image at 90.4% sensitivity using seven features selected. Compared to our previous method, the number of FPs was reduced by 38% at the same sensitivity level. The proposed method has a potential in identifying patients with a risk of arteriosclerosis early via general dental examinations.
This paper describes a universal approach to automatic segmentation of different internal organ and tissue regions in three-dimensional (3D) computerized tomography (CT) scans. The proposed approach combines object localization, a probabilistic atlas, and 3D GrabCut techniques to achieve automatic and quick segmentation. The proposed method first detects a tight 3D bounding box that contains the target organ region in CT images and then estimates the prior of each pixel inside the bounding box belonging to the organ region or background based on a dynamically generated probabilistic atlas. Finally, the target organ region is separated from the background by using an improved 3D GrabCut algorithm. A machine-learning method is used to train a detector to localize the 3D bounding box of the target organ using template matching on a selected feature space. A content-based image retrieval method is used for online generation of a patient-specific probabilistic atlas for the target organ based on a database. A 3D GrabCut algorithm is used for final organ segmentation by iteratively estimating the CT number distributions of the target organ and backgrounds using a graph-cuts algorithm. We applied this approach to localize and segment twelve major organ and tissue regions independently based on a database that includes 1300 torso CT scans. In our experiments, we randomly selected numerous CT scans and manually input nine principal types of inner organ regions for performance evaluation. Preliminary results showed the feasibility and efficiency of the proposed approach for addressing automatic organ segmentation issues on CT images.
In this paper, we present a texture classification method based on texton learned via sparse representation (SR) with new feature histogram maps in the classification of emphysema. First, an overcomplete dictionary of textons is learned via KSVD learning on every class image patches in the training dataset. In this stage, high-pass filter is introduced to exclude patches in smooth area to speed up the dictionary learning process. Second, 3D joint-SR coefficients and intensity histograms of the test images are used for characterizing regions of interest (ROIs) instead of conventional feature histograms constructed from SR coefficients of the test images over the dictionary. Classification is then performed using a classifier with distance as a histogram dissimilarity measure. Four hundreds and seventy annotated ROIs extracted from 14 test subjects, including 6 paraseptal emphysema (PSE) subjects, 5 centrilobular emphysema (CLE)
subjects and 3 panlobular emphysema (PLE) subjects, are used to evaluate the effectiveness and robustness of the
proposed method. The proposed method is tested on 167 PSE, 240 CLE and 63 PLE ROIs consisting of mild, moderate
and severe pulmonary emphysema. The accuracy of the proposed system is around 74%, 88% and 89% for PSE, CLE
and PLE, respectively.
This paper describes an approach to accomplish the fast and automatic localization of the different inner organ regions on 3D CT scans. The proposed approach combines object detections and the majority voting technique to achieve the robust and quick organ localization. The basic idea of proposed method is to detect a number of 2D partial appearances of a 3D target region on CT images from multiple body directions, on multiple image scales, by using multiple feature spaces, and vote all the 2D detecting results back to the 3D image space to statistically decide one 3D bounding rectangle of the target organ. Ensemble learning was used to train the multiple 2D detectors based on template matching on local binary patterns and Haar-like feature spaces. A collaborative voting was used to decide the corner coordinates of the 3D bounding rectangle of the target organ region based on the coordinate histograms from detection results in three body directions. Since the architecture of the proposed method (multiple independent detections connected to a majority voting) naturally fits the parallel computing paradigm and multi-core CPU hardware, the proposed algorithm was easy to achieve a high computational efficiently for the organ localizations on a whole body CT scan by using general-purpose computers. We applied this approach to localization of 12 kinds of major organ regions independently on 1,300 torso CT scans. In our experiments, we randomly selected 300 CT scans (with human indicated organ and tissue locations) for training, and then, applied the proposed approach with the training results to localize each of the target regions on the other 1,000 CT scans for the performance testing. The experimental results showed the possibility of the proposed approach to automatically locate different kinds of organs on the whole body CT scans.
Diagnostic imaging on FDG-PET scans was often used to evaluate chemotherapy results of cancer patients. Radiologists compare the changes of lesions' activities between previous and current examinations for the evaluation. The purpose of this study was to develop a new computer-aided detection (CAD) system with temporal subtraction technique for FDGPET scans and to show the fundamental usefulness based on an observer performance study. Z-score mapping based on statistical image analysis was newly applied to the temporal subtraction technique. The subtraction images can be obtained based on the anatomical standardization results because all of the patients' scans were deformed into standard body shape. An observer study was performed without and with computer outputs to evaluate the usefulness of the scheme by ROC (receiver operating characteristics) analysis. Readers responded as confidence levels on a continuous scale from absolutely no change to definitely change between two examinations. The recognition performance of the computer outputs for the 43 pairs was 96% sensitivity with 31.1 false-positive marks per scan. The average of area-under-the-ROC-curve (AUC) from 4 readers in the observer performance study was increased from 0.85 without computer outputs to 0.90 with computer outputs (p=0.0389, DBM-MRMC). The average of interpretation time was slightly decreased from 42.11 to 40.04 seconds per case (p=0.625, Wilcoxon test). We concluded that the CAD system for torso FDG-PET scans with temporal subtraction technique might improve the diagnostic accuracy of radiologist in cancer therapy evaluation.
Measurement of visual quality is of fundamental importance for numerous image and video processing applications. This
paper presented a novel and concise reduced reference (RR) image quality assessment method. Statistics of local binary
pattern (LBP) is introduced as a similarity measure to form a novel RR image quality assessment (IQA) method for the
first time. With this method, first, the test image is decomposed with a multi-scale transform. Second, LBP encoding
maps are extracted for each of subband images. Third, the histograms are extracted from the LBP encoding map to form
the RR features. In this way, image structure primitive information for RR features extraction can be reduced greatly.
Hence, new RR IQA method is formed with only at most 56 RR features. The experimental results on two large scale
IQA databases show that the statistic of LBPs is fairly robust and reliable to RR IQA task. The proposed methods show
strong correlations with subjective quality evaluations.
ROC studies require complex procedures to select cases from many data samples, and to set confidence levels in
each selected case to generate ROC curves. In some observer performance studies, researchers have to develop software
with specific graphical user interface (GUI) to obtain confidence levels from readers. Because ROC studies could be
designed for various clinical situations, it is difficult task for preparing software corresponding to every ROC studies. In
this work, we have developed software for recording confidence levels during observer studies on tiny personal handheld
devices such as iPhone, iPod touch, and iPad. To confirm the functions of our software, three radiologists performed
observer studies to detect lung nodules by using public database of chest radiograms published by Japan Society of
Radiological Technology. The output in text format conformed to the format for the famous ROC kit from the University
of Chicago. Times required for the reading each case was recorded very precisely.
To identify asymptomatic patients is the challenging task and the essential first step in diagnosis. Findings of dental
panoramic radiographs include not only dental conditions but also radiographic signs that are suggestive of possible
systemic diseases such as osteoporosis, arteriosclerosis, and maxillary sinusitis. Detection of such signs on panoramic
radiographs has a potential to provide supplemental benefits for patients. However, it is not easy for general dental
practitioners to pay careful attention to such signs. We addressed the development of a computer-aided detection (CAD)
system that detects radiographic signs of pathology on panoramic images, and the design of the framework of new
screening pathway by cooperation of dentists and our CAD system. The performance evaluation of our CAD system
showed the sensitivity and specificity in the identification of osteoporotic patients were 92.6 % and 100 %, respectively,
and those of the maxillary sinus abnormality were 89.6 % and 73.6 %, respectively. The detection rate of carotid artery
calcifications that suggests the need for further medical evaluation was approximately 93.6 % with 4.4 false-positives per
image. To validate the utility of the new screening pathway, preliminary clinical trials by using our CAD system were
conducted. To date, 223 panoramic images were processed and 4 asymptomatic patients with suspected osteoporosis, 7
asymptomatic patients with suspected calcifications, and 40 asymptomatic patients with suspected maxillary sinusitis
were detected in our initial trial. It was suggested that our new screening pathway could be useful to identify
asymptomatic patients with systemic diseases.
We aim at using a new texton based texture classification method in the classification of pulmonary emphysema in
computed tomography (CT) images of the lungs. Different from conventional computer-aided diagnosis (CAD)
pulmonary emphysema classification methods, in this paper, firstly, the dictionary of texton is learned via applying
sparse representation(SR) to image patches in the training dataset. Then the SR coefficients of the test images over the
dictionary are used to construct the histograms for texture presentations. Finally, classification is performed by using a
nearest neighbor classifier with a histogram dissimilarity measure as distance. The proposed approach is tested on 3840
annotated regions of interest consisting of normal tissue and mild, moderate and severe pulmonary emphysema of three
subtypes. The performance of the proposed system, with an accuracy of about 88%, is comparably higher than state of
the art method based on the basic rotation invariant local binary pattern histograms and the texture classification method
based on texton learning by k-means, which performs almost the best among other approaches in the literature.
Findings of dental panoramic radiographs (DPRs) have shown that the mandibular cortical thickness (MCT) was
significantly correlated with osteoporosis. Identifying asymptomatic patients with osteoporosis through dental
examinations may bring a supplemental benefit for the patients. However, most of the DPRs are used for only diagnosing
dental conditions by dentists in their routine clinical work. The aim of this study was to develop a computeraided
diagnosis scheme that automatically measures MCT to assist dentists in screening osteoporosis. First, the inferior
border of mandibular bone was detected by use of an active contour method. Second, the locations of mental foramina
were estimated on the basis of the inferior border of mandibular bone. Finally, MCT was measured on the basis of the
grayscale profile analysis. One hundred DPRs were used to evaluate our proposed scheme. Experimental results showed
that the sensitivity and specificity for identifying osteoporotic patients were 92.6 % and 100 %, respectively. We
conducted multiclinic trials, in which 223 cases have been obtained and processed in about a month. Our scheme
succeeded in detecting all cases of suspected osteoporosis. Therefore, our scheme may have a potential to identify
osteoporotic patients at an early stage.
This paper presents a fast and robust segmentation scheme that automatically identifies and extracts a massive-organ
region on torso CT images. In contrast to the conventional algorithms that are designed empirically for segmenting a
specific organ based on traditional image processing techniques, the proposed scheme uses a fully data-driven approach
to accomplish a universal solution for segmenting the different massive-organ regions on CT images. Our scheme
includes three processing steps: machine-learning-based organ localization, content-based image (reference) retrieval,
and atlas-based organ segmentation techniques. We applied this scheme to automatic segmentations of heart, liver,
spleen, left and right kidney regions on non-contrast CT images respectively, which are still difficult tasks for traditional
segmentation algorithms. The segmentation results of these organs are compared with the ground truth that manually
identified by a medical expert. The Jaccard similarity coefficient between the ground truth and automated segmentation
result centered on 67% for heart, 81% for liver, 78% for spleen, 75% for left kidney, and 77% for right kidney. The
usefulness of our proposed scheme was confirmed.
For gaining a better understanding of bone quality, a great deal of attention has been paid to vertebral geometry in
anatomy. The aim of this study was to design a decision support scheme for vertebral geometries. The proposed scheme
consists of four parts: (1) automated extraction of bone, (2) generation of median plane image of spine, (3) detection of
vertebrae, (4) quantification of vertebral body width, depth, cross-sectional area (CSA), and trabecular bone mineral
density (BMD). The proposed scheme was applied to 10 CT cases and compared with manual tracking performed by an
anatomy expert. Mean differences in the width, depth, CSA, and trabecular BMD were 3.1 mm, 1.4 mm, 88.7 mm2, and
7.3 mg/cm3, respectively. We found moderate or high correlations in vertebral geometry between our scheme and
manual tracking (r > 0.72). In contrast, measurements obtained by using our scheme were slightly smaller than those
acquired from manual tracking. However, the outputs of the proposed scheme in most CT cases were regarded to be
appropriate on the basis of the subjective assessment of an anatomy expert. Therefore, if the appropriate outputs from the
proposed scheme are selected in advance by an anatomy expert, the results can potentially be used for an analysis of
vertebral body geometries.
The multidetector row computed tomography (MDCT) method has the potential to be used for quantitative analysis
of osteoporosis with higher accuracy and precision than that provided by conventional two-dimensional methods. It is
desirable to develop a computer-assisted scheme for analyzing vertebral geometry using body CT images. The aim of
this study was to design a computerized scheme for the localization of vertebral bodies on body CT images. Our new
scheme involves the following steps: (i) Re-formation of CT images on the basis of the center line of the spinal canal to
visually remove the spinal curvature, (ii) use of information on the position of the ribs relative to the vertebral bodies,
(iii) the construction of a simple model on the basis of the contour of the vertebral bodies on CT sections, and (iv) the
localization of individual vertebral bodies by using a template matching technique. The proposed scheme was applied to
104 CT cases, and its performance was assessed using the Hausdorff distance. The average Hausdorff distance of T2-L5
was 4.3 mm when learning models with 100 samples were used. On the other hand, the average Hausdorff distance with
10 samples was 5.1 mm. The results of our assessments confirmed that the proposed scheme could provide the location
of individual vertebral bodies. Therefore, the proposed scheme may be useful in designing a computer-based application
that analyzes vertebral geometry on body CT images.
To detect the metastatic liver tumor on CT scans, two liver edge maps on unenhanced and portal venous phase images
are firstly extracted and registered using phase-only correlation (POC) method, by which rotation and shift parameters
are detected on two log-polar transformed power spectrum images. Then the liver gray map is obtained on non-contrast
phase images by calculating the gray value within the region of edge map. The initial tumors are derived from the
subtraction of edge and gray maps as well as referring to the score from the spherical gray-level differentiation searching
(SGDS) filter. Finally the FPs are eliminated by shape and texture features. 12 normal cases and 25 cases with 44
metastatic liver tumors are used to test the performance of our algorithm, 86.7% of TPs are successfully extracted by our
CAD system with 2.5 FPs per case. The result demonstrates that the POC is a robust method for the liver registration,
and our proposed SGDS filter is effective to detect spherical shape tumor on CT images. It is expected that our CAD
system could useful for quantitative assessment of metastatic liver tumor in clinical practice.
X-ray CT images have been widely used in clinical routine in recent years. CT images scanned by a modern CT
scanner can show the details of various organs and tissues. This means various organs and tissues can be simultaneously
interpreted on CT images. However, CT image interpretation requires a lot of time and energy. Therefore, support for
interpreting CT images based on image-processing techniques is expected. The interpretation of the spinal curvature is
important for clinicians because spinal curvature is associated with various spinal disorders. We propose a quantification
scheme of the spinal curvature based on the center line of spinal canal on CT images. The proposed scheme consists of
four steps: (1) Automated extraction of the skeletal region based on CT number thresholding. (2) Automated extraction
of the center line of spinal canal. (3) Generation of the median plane image of spine, which is reformatted based on the
spinal canal. (4) Quantification of the spinal curvature. The proposed scheme was applied to 10 cases, and compared
with the Cobb angle that is commonly used by clinicians. We found that a high-correlation (for the 95% confidence
interval, lumbar lordosis: 0.81-0.99) between values obtained by the proposed (vector) method and Cobb angle. Also, the
proposed method can provide the reproducible result (inter- and intra-observer variability: within 2°). These
experimental results suggested a possibility that the proposed method was efficient for quantifying the spinal curvature
on CT images.
In aging societies, it is important to analyze age-related hypokinesia. A psoas major muscle has many important
functional capabilities such as capacity of balance and posture control. These functions can be measured by its cross
sectional area (CSA), volume, and thickness. However, these values are calculated manually in the clinical situation. The
purpose of our study is to propose an automated recognition method of psoas major muscles in X-ray torso CT images.
The proposed recognition process involves three steps: 1) determination of anatomical points such as the origin and
insertion of the psoas major muscle, 2) generation of a shape model for the psoas major muscle, and 3) recognition of the
psoas major muscles by use of the shape model. The model was built using quadratic function, and was fit to the
anatomical center line of psoas major muscle. The shape model was generated using 20 CT cases and tested by 20 other
CT cases. The applied database consisted of 12 male and 8 female cases from the ages of 40's to 80's. The average value
of Jaccard similarity coefficient (JSC) values employed in the evaluation was 0.7. Our experimental results indicated that
the proposed method was effective for a volumetric analysis and could be possible to be used for a quantitative
measurement of psoas major muscles in CT images.
X-ray CT images have been widely used in clinical diagnosis in recent years. A modern CT scanner can generate
about 1000 CT slices to show the details of all the human organs within 30 seconds. However, CT image interpretations
(viewing 500-1000 slices of CT images manually in front of a screen or films for each patient) require a lot of time and
energy. Therefore, computer-aided diagnosis (CAD) systems that can support CT image interpretations are strongly
anticipated. Automated recognition of the anatomical structures in CT images is a basic pre-processing of the CAD
system. The bone structure is a part of anatomical structures and very useful to act as the landmarks for predictions of the
other different organ positions. However, the automated recognition of the bone structure is still a challenging issue. This
research proposes an automated scheme for segmenting the bone regions and recognizing the bone structure in noncontrast
torso CT images. The proposed scheme was applied to 48 torso CT cases and a subjective evaluation for the
experimental results was carried out by an anatomical expert following the anatomical definition. The experimental
results showed that the bone structure in 90% CT cases have been recognized correctly. For quantitative evaluation,
automated recognition results were compared to manual inputs of bones of lower limb created by an anatomical expert
on 10 randomly selected CT cases. The error (maximum distance in 3D) between the recognition results and manual
inputs distributed from 3-8 mm in different parts of the bone regions.
The purpose of this work was to develop an automated method to calculate the score of SUV for torso region on FDG-PET scans. The three dimensional distributions for the mean and the standard deviation values of SUV were stored in each volume to score the SUV in corresponding pixel position within unknown scans. The modeling methods is based on SPM approach using correction technique of Euler characteristic and Resel (Resolution element). We employed 197 nor-mal cases (male: 143, female: 54) to assemble the normal metabolism distribution of FDG. The physique were registered each other in a rectangular parallelepiped shape using affine transformation and Thin-Plate-Spline technique. The regions of the three organs were determined based on semi-automated procedure. Seventy-three abnormal spots were used to estimate the effectiveness of the scoring methods. As a result, the score images correctly represented that the scores for normal cases were between zeros to plus/minus 2 SD. Most of the scores of abnormal spots associated with cancer were lager than the upper of the SUV interval of normal organs.
Cirrhosis of the liver is a chronic disease. It is characterized by the presence of widespread nodules and fibrosis in
the liver which results in characteristic texture patterns. Computerized analysis of hepatic texture patterns is usually
based on regions-of-interest (ROIs). However, not all ROIs are typical representatives of the disease stage of the
liver from which the ROIs originated. This leads to uncertainties in the ROI labels (diseased or non-diseased). On
the other hand, supervised classifiers are commonly used in determining the assignment rule. This presents a
problem as the training of a supervised classifier requires the correct labels of the ROIs. The main purpose of this
paper is to investigate the use of an unsupervised classifier, the k-means clustering, in classifying ROI based data.
In addition, a procedure for generating a receiver operating characteristic (ROC) curve depicting the classification
performance of k-means clustering is also reported. Hepatic MRI images of 44 patients (16 cirrhotic; 28 non-cirrhotic)
are used in this study. The MRI data are derived from gadolinium-enhanced equilibrium phase images.
For each patient, 10 ROIs selected by an experienced radiologist and 7 texture features measured on each ROI are
included in the MRI data. Results of the k-means classifier are depicted using an ROC curve. The area under the
curve (AUC) has a value of 0.704. This is slightly lower than but comparable to that of LDA and ANN classifiers
which have values 0.781 and 0.801, respectively. Methods in constructing ROC curve in relation to k-means
clustering have not been previously reported in the literature.
In order to support the diagnosis of hepatic diseases, understanding the anatomical structures of hepatic lobes and
hepatic vessels is necessary. Although viewing and understanding the hepatic vessels in contrast media-enhanced CT
images is easy, the observation of the hepatic vessels in non-contrast X-ray CT images that are widely used for the
screening purpose is difficult. We are developing a computer-aided diagnosis (CAD) system to support the liver
diagnosis based on non-contrast X-ray CT images. This paper proposes a new approach to segment the middle hepatic
vein (MHV), a key structure (landmark) for separating the liver region into left and right lobes. Extraction and
classification of hepatic vessels are difficult in non-contrast X-ray CT images because the contrast between hepatic
vessels and other liver tissues is low. Our approach uses an atlas-driven method by the following three stages. (1)
Construction of liver atlases of left and right hepatic lobes using a learning datasets. (2) Fully-automated enhancement
and extraction of hepatic vessels in liver regions. (3) Extraction of MHV based on the results of (1) and (2). The
proposed approach was applied to 22 normal liver cases of non-contrast X-ray CT images. The preliminary results show
that the proposed approach achieves the success in 14 cases for MHV extraction.
Cirrhosis of the liver is characterized by the presence of widespread nodules and fibrosis in the liver. The fibrosis
and nodules formation causes distortion of the normal liver architecture, resulting in characteristic texture patterns.
Texture patterns are commonly analyzed with the use of co-occurrence matrix based features measured on regions-of-interest (ROIs). A classifier is subsequently used for the classification of cirrhotic or non-cirrhotic livers.
Problem arises if the classifier employed falls into the category of supervised classifier which is a popular choice.
This is because the 'true disease states' of the ROIs are required for the training of the classifier but is, generally, not
available. A common approach is to adopt the 'true disease state' of the liver as the 'true disease state' of all ROIs in
that liver. This paper investigates the use of a nonsupervised classifier, the k-means clustering method in classifying
livers as cirrhotic or non-cirrhotic using unlabelled ROI data. A preliminary result with a sensitivity and specificity
of 72% and 60%, respectively, demonstrates the feasibility of using the k-means non-supervised clustering method
in generating a characteristic cluster structure that could facilitate the classification of cirrhotic and non-cirrhotic
livers.
We have been developing the CAD scheme for head and abdominal injuries for emergency medical care. In this work, we
have developed an automated method to detect typical head injuries, rupture or strokes of brain. Extradural and subdural
hematoma region were detected by comparing technique after the brain areas were registered using warping. We employ
5 normal and 15 stroke cases to estimate the performance after creating the brain model with 50 normal cases. Some of
the hematoma regions were detected correctly in all of the stroke cases with no false positive findings on normal cases.
Primary malignant liver tumor, including hepatocellular carcinoma (HCC), caused 1.25 million deaths per year
worldwide. Multiphase CT images offer clinicians important information about hepatic cancer. The presence of HCC is
indicated by high-intensity regions in arterial phase images and low-intensity regions in equilibrium phase images
following enhancement with contrast material. We propose an automatic method for detecting HCC based on edge
detection and subtraction processing. Within a liver area segmented according to our scheme, black regions are selected
by subtracting the equilibrium phase images to the corresponding registrated arterial phase images. From these black
regions, the HCC candidates are extracted as the areas without edges by using Sobel and LoG edge detection filters. The
false-positive (FP) candidates are eliminated by using six features extracted from the cancer and liver regions. Other FPs
are further eliminated by opening processing. Finally, an expansion process is applied to acquire the 3D shape of the
HCC. The cases used in this experiment were from the CT images of 44 patients, which included 44 HCCs. We extracted
97.7% (43/44) HCCs successfully by our proposed method, with an average number of 2.1 FPs per case. The result
demonstrates that our edge-detection-based method is effective in locating the cancer region by using the information
obtained from different phase images.
The identification of mammary gland regions is a necessary processing step during the anatomical structure
recognition of human body and can be expected to provide the useful information for breast tumor diagnosis. This paper
proposes a fully-automated scheme for segmenting the mammary gland regions in non-contrast torso CT images. This
scheme calculates the probability for each voxel belonging to the mammary gland or other regions (for example
pectoralis major muscles) in CT images and decides the mammary gland regions automatically. The probability is
estimated from the location of the mammary gland and pectoralis major muscles in CT images. The location (named as a
probabilistic atlas) is investigated from the pre-segmentation results in a number of different CT scans and the CT
number distribution is approximated using a Gaussian function. We applied this scheme to 66 patient cases (female, age:
40-80) and evaluated the accuracy by using the coincidence rate between the segmented result and gold standard that is
generated manually by a radiologist for each CT case. The mean value of the coincidence rate was 0.82 with the standard
deviation of 0.09 for 66 CT cases.
Hepatic vessel trees are the key structures in the liver. Knowledge of the hepatic vessel trees is important for liver surgery
planning and hepatic disease diagnosis such as portal hypertension. However, hepatic vessels cannot be easily distinguished
from other liver tissues in non-contrast CT images. Automated segmentation of hepatic vessels in non-contrast CT images
is a challenging issue. In this paper, an approach for automated segmentation of hepatic vessels trees in non-contrast X-ray
CT images is proposed. Enhancement of hepatic vessels is performed using two techniques: (1) histogram transformation
based on a Gaussian window function; (2) multi-scale line filtering based on eigenvalues of Hessian matrix. After the
enhancement of hepatic vessels, candidate of hepatic vessels are extracted by thresholding. Small connected regions of
size less than 100 voxels are considered as false-positives and are removed from the process. This approach is applied to
20 cases of non-contrast CT images. Hepatic vessel trees segmented from the contrast-enhanced CT images of the same
patient are used as the ground truth in evaluating the performance of the proposed segmentation method. Results show that
the proposed method can enhance and segment the hepatic vessel regions in non-contrast CT images correctly.
Segmentation of an abnormal liver region based on CT or MR images is a crucial step in surgical planning. However,
precisely carrying out this step remains a challenge due to either connectivities of the liver to other organs or the shape,
internal texture, and homogeneity of liver that maybe extensively affected in case of liver diseases. Here, we propose a
non-density based method for extracting the liver region containing tumor tissues by edge detection processing. False
extracted regions are eliminated by a shape analysis method and thresholding processing. If the multi-phased images are
available then the overall outcome of segmentation can be improved by subtracting two phase images, and the
connectivities can be further eliminated by referring to the intensity on another phase image. Within an edge liver map,
tumor candidates are identified by their different gray values relative to the liver. After elimination of the small and nonspherical
over-extracted regions, the final liver region integrates the tumor region with the liver tissue. In our experiment,
40 cases of MDCT images were used and the result showed that our fully automatic method for the segmentation of liver
region is effective and robust despite the presence of hepatic tumors within the liver.
An automatic extraction of pulmonary emphysema area on 3-D chest CT images was performed using an adaptive thresholding technique. We proposed a method to estimate the ratio of the emphysema area to the whole lung volume. We employed 32 cases (15 normal and 17 abnormal) which had been already diagnosed by radiologists prior to the study. The ratio in all the normal cases was less than 0.02, and in abnormal cases, it ranged from 0.01 to 0.26. The effectiveness of our approach was confirmed through the results of the present study.
Computer-aided diagnosis (CAD) has been expected to help radiologists to improve the accuracy of abnormality detection and reduce the burden during CT image interpretations. In order to realize such functions, automated segmentations of the target organ regions are always required by CAD systems. This paper describes a fully automatic processing procedure, which is designed to identify inter-lobe fissures and divide lung into five lobe regions. The lung fissures are disappeared very fuzzy and indefinite in CT images, so that it is very difficult to extract fissures directly based on its CT values. We propose a method to solve this problem using the anatomy knowledge of human lung. We extract lung region firstly and then recognize the structures of lung vessels and bronchus. Based on anatomy knowledge, we classify the vessels and bronchus on a lobe-by-lobe basis and estimate the boundary of each lobe region as the initial fissure locations. Within those locations, we extract lung fissures precisely based on an edge detection method and divide lung regions into five lung lobes lastly. The performance of the proposed method was evaluated using 9 patient cases of high-resolution multi-slice chest CT images; the improvement has been confirmed with the reliable recognition results.
We have been developing a computer-aided diagnosis (CAD) scheme for automatically recognizing human tissue and organ regions from high-resolution torso CT images. We show some initial results for extracting skin, soft-tissue and skeleton regions. 139 patient cases of torso CT images (male 92, female 47; age: 12-88) were used in this study. Each case was imaged with a common protocol (120kV/320mA) and covered the whole torso with isotopic spatial resolution of about 0.63 mm and density resolution of 12 bits. A gray-level thresholding based procedure was applied to separate the human body from background. The density and distance features to body surface were used to determine the skin, and separate soft-tissue from the others. A 3-D region growing based method was used to extract the skeleton. We applied this system to the 139 cases and found that the skin, soft-tissue and skeleton regions were recognized correctly for 93% of the patient cases. The accuracy of segmentation results was acceptable by evaluating the results slice by slice. This scheme will be included in CAD systems for detecting and diagnosing the abnormal lesions in multi-slice torso CT images.
We have developed an algorithm that can be used to distinguish the central part of the vertebral body from an
abdominal X-ray CT image and to automatically calculate three measures to diagnose the degree of osteoporosis in a
patient. In addition, we examined whether it is possible to use these CT images as an aid in diagnosing osteoporosis.
Three measures that were automatically extracted from the central part of a vertebral body in the CT images were
compared with the bone mineral density (BMD) values that were obtained from the same vertebral body. We calculated
the mean CT number, coefficient of variation, and the first moment of power spectrum in the recognized vertebral body.
We judged whether a patient had osteoporosis using the diagnostic criteria for primary osteoporosis (Year 2000
revision, published by the Japanese Society for Bone and Mineral Research). We classified three measures for normal
and abnormal groups using the principal component analysis, and the two groups were compared with the results
obtained from the diagnostic criteria. As a result, it was found that the algorithm could be used to distinguish the central
part of the vertebral body in the CT images and to calculate these measures automatically. When distinguishing whether
a patient was osteoporotic or not with the three measures obtained from the CT images, the ratio (sensitivity) usable for
diagnosing a patient as osteoporotic was 0.93 (14/15), and the ratio (specificity) usable for diagnosing a patient as
normal was 0.64 (7/11). Based on these results, we believe that it is possible to utilize the measures obtained from these
CT images to aid in diagnosing osteoporosis.
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