Magnetic resonance imaging (MRI) is well suited for Solid renal masses (SRMs) characterization (e.g., benign vs. malignant) due to its superior soft tissue contrast. Though renal mass detection and characterization using deep-learning (DL) methods have been extensively studied for computed tomography (CT) images, those same tasks are yet to be investigated on MRI images. SRMs need active surveillance as they consist of biologically diverse heterogeneous groups of benign or malignant masses. Among them, malignant clear cell renal carcinoma (ccRCC) is frequently aggressive. There are inter-observer and intra-observer differences in the assessment of SRMs by expert clinicians because of their experience and expertise. Therefore, it is essential to develop a machine learningbased noninvasive imaging diagnosis to distinguish SRMs as benign and malignant. Our retrospective study consisted of malignant (renal cell carcinoma- clear cell, papillary, and chromophobe) and benign (fat-poor angiomyolipoma-fpAML, oncocytomas) SRMs. We extracted first and second-order radiomics features from SRMs on T2W and T1W-CM MRI to train different machine learning (ML) models using the 5-fold cross-validation for benign vs malignant classification. The support vector machine (SVM) algorithm generated benign vs malignant classification accuracy of 90.00% with ROC-AUC of 76.19% on T2W MRI and the custom-designed multilayer perceptron model (MLP) model produced accuracy of 80.00% with ROC-AUC of 75.47% on T1W-CM MRI. Thus, ML-based radiomics features classification of SRMs extracted on MRI may be an alternative to biopsy using a non-invasive assessment of SRMs.
KEYWORDS: Image quality, Magnetic resonance imaging, Image segmentation, Diffusion weighted imaging, Prostate, Analog to digital converters, Rectum, Radiomics, Machine learning, Education and training
PurposeDiagnostic performance of prostate MRI depends on high-quality imaging. Prostate MRI quality is inversely proportional to the amount of rectal gas and distention. Early detection of poor-quality MRI may enable intervention to remove gas or exam rescheduling, saving time. We developed a machine learning based quality prediction of yet-to-be acquired MRI images solely based on MRI rapid localizer sequence, which can be acquired in a few seconds.ApproachThe dataset consists of 213 (147 for training and 64 for testing) prostate sagittal T2-weighted (T2W) MRI localizer images and rectal content, manually labeled by an expert radiologist. Each MRI localizer contains seven two-dimensional (2D) slices of the patient, accompanied by manual segmentations of rectum for each slice. Cascaded and end-to-end deep learning models were used to predict the quality of yet-to-be T2W, DWI, and apparent diffusion coefficient (ADC) MRI images. Predictions were compared to quality scores determined by the experts using area under the receiver operator characteristic curve and intra-class correlation coefficient.ResultsIn the test set of 64 patients, optimal versus suboptimal exams occurred in 95.3% (61/64) versus 4.7% (3/64) for T2W, 90.6% (58/64) versus 9.4% (6/64) for DWI, and 89.1% (57/64) versus 10.9% (7/64) for ADC. The best performing segmentation model was 2D U-Net with ResNet-34 encoder and ImageNet weights. The best performing classifier was the radiomics based classifier.ConclusionsA radiomics based classifier applied to localizer images achieves accurate diagnosis of subsequent image quality for T2W, DWI, and ADC prostate MRI sequences.
KEYWORDS: Kidney, Magnetic resonance imaging, Image segmentation, Cancer detection, Performance modeling, Tumor growth modeling, Data modeling, Deep learning
Due to the superior soft tissue contrast in magnetic resonance imaging (MRI), MRI may be well suited for renal mass characterization (e.g., benign vs. malignant). Though renal mass detection and characterization using deeplearning (DL) methods have been extensively studied for CT images, those same tasks are yet to be investigated on MR images. Existing algorithms for renal mass characterization require manual segmentation, therefore development of algorithms to localize and detect renal masses is important fully automatically. In this study, we developed a DL-based fully automated renal mass detection model on T2- weighted (T2W) images. In a cascaded approach, we initially segmented kidneys as a region-of-interest (ROI) using 2D U-Net model, then renal masses were detected on segmented kidneys using 2D U-Net convolutional neural network (CNN) model. We trained our model on randomly selected 80% of dataset using 5-fold cross-validation technique and evaluated on remaining 20% test cases for renal mass detection. Our T2W MRI dataset contained 108 patients with malignant (renal cell carcinoma- clear cell, papillary and chromophobe) and benign (fat poor angiomyolipoma-fpAML, oncocytomas) renal masses. The U-Net model for renal mass detection generated Dice similarity coefficient (DSC) of 90.00 ± 6.00 % (mean ± standard deviation). When localized kidneys evaluated on U-Net renal mass detection model yielded a sensitivity/recall, and specificity of 76.49% and 86.55%, respectively. Thus, our proposed fully automated cascaded approach has potential to be used as the first step in renal mass characterization study on T2W MRI images.
KEYWORDS: Kidney, Image segmentation, Data modeling, Magnetic resonance imaging, 3D modeling, Performance modeling, Statistical modeling, 3D image processing, Tumor growth modeling, 3D acquisition
Purpose: Multiparametric magnetic resonance imaging (mp-MRI) is being investigated for kidney cancer because of better soft tissue contrast ability. The necessity of manual labels makes the development of supervised kidney segmentation algorithms challenging for each mp-MRI protocol. Here, we developed a transfer learning-based approach to improve kidney segmentation on a small dataset of five other mp-MRI sequences.
Approach: We proposed a fully automated two-dimensional (2D) attention U-Net model for kidney segmentation on T1 weighted-nephrographic phase contrast enhanced (CE)-MRI (T1W-NG) dataset (N = 108). The pretrained weights of T1W-NG kidney segmentation model transferred to five other distinct mp-MRI sequences model (T2W, T1W-in-phase (T1W-IP), T1W-out-of-phase (T1W-OP), T1W precontrast (T1W-PRE), and T1W-corticomedullary-CE (T1W-CM), N = 50) and fine-tuned by unfreezing the layers. The individual model performances were evaluated with and without transfer-learning fivefold cross-validation on average Dice similarity coefficient (DSC), absolute volume difference, Hausdorff distance (HD), and center-of-mass distance (CD) between algorithm generated and manually segmented kidneys.
Results: The developed 2D attention U-Net model for T1W-NG produced kidney segmentation DSC of 89.34 ± 5.31 % . Compared with randomly initialized weight models, the transfer learning-based models of five mp-MRI sequences showed average increase of 2.96% in DSC of kidney segmentation (p = 0.001 to 0.006). Specifically, the transfer-learning approach increased average DSC on T2W from 87.19% to 89.90%, T1W-IP from 83.64% to 85.42%, T1W-OP from 79.35% to 83.66%, T1W-PRE from 82.05% to 85.94%, and T1W-CM from 85.65% to 87.64%.
Conclusions: We demonstrate that a pretrained model for automated kidney segmentation of one mp-MRI sequence improved automated kidney segmentation on five other additional sequences.
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