KEYWORDS: Magnetic resonance imaging, Ultrasonography, Tissues, Image segmentation, Reliability, 3D acquisition, Prototyping, Inflammation, 3D metrology
Synovial inflammation is increasingly appreciated as a key feature in osteoarthritis pathogenesis and pain, but the gold standard method of measuring synovitis (MRI) is inaccessible in routine clinical care. 3-dimensional ultrasound could present a potential solution if it demonstrates good measurement properties in suprapatellar recess synovitis. We recruited five knee osteoarthritis patients awaiting knee replacement, who received both MRI and 3DUS imaging of the knee on the same day. By manually segmenting synovitis on 3DUS and MRI images, we found that 3DUS has excellent intra/inter-rater reliability for synovitis volume and differs from MRI segmentations by approximately 26.73%.
Osteoarthritis (OA) is the most common chronic health condition and a leading cause of disability and pain in the United States and Canada. Current methods for monitoring the development of knee OA (KOA) involve x-ray radiography and magnetic resonance imaging (MRI) to assess femoral articular cartilage (FAC) degradation and synovial membrane inflammation. However, x-ray radiography cannot be used to quantify FAC loss or synovial membrane inflammation due to a lack of soft tissue contrast, and MRI is associated with high costs, long waitlists, long scan times, and is inaccessible to many patients. We have developed a counterbalanced point-of-care (POC) system to track multiple three-dimensional (3D) ultrasound (US) acquisitions and register them for visualizing the entire suprapatellar synovium. This work aims to validate the tracking accuracy of the POC system against an external optical tracking system. Validation was conducted using optical tracking as a reference by mounting a custom optical tracking stylus in place of the 3D US scanner on the POC system. The stylus was manipulated in 3D space and Euclidean distances were calculated using the initial and final positions of the stylus and were compared between systems to quantify POC tracking system error. Results indicated that the overall mean absolute tracking error of the POC system was 3.08 ± 2.01 mm with no statistically significant difference between the POC and optical systems (p = 0.965). The POC system has the potential to enable clinicians and researchers to obtain additional information without added complexity or discomfort to patients.
KEYWORDS: Image segmentation, 3D metrology, 3D image processing, 3D acquisition, Magnetic resonance imaging, Scanners, Cartilage, 3D scanning, Arthritis, Rheumatology
The most common chronic inflammatory and chronic joint diseases in Canada are rheumatoid arthritis (RA) and osteoarthritis (OA) respectively. The current methods for monitoring the development of these diseases and their response to treatment involve acquiring x-ray and magnetic resonance imaging (MRI) images and comparing the results to the patient’s symptoms during examination. However, x-ray imaging is associated with difficulties when trying to interpret 3D anatomy, and MRI is associated with high operating costs, long waitlists, long scan times, and is inaccessible to mobility-impaired patients. Our solution to these limitations is the use of three-dimensional ultrasound (3D US) imaging for providing bedside monitoring of RA and OA progression and their response to treatment. This project validates two 3D US acquisition devices: tilt acquisition and linear acquisition scanning methods. The linear and volumetric measurement capabilities were validated through scanning phantoms and segmenting resulting images at repeated time points. A proof-of-concept volunteer scan was conducted to compare the capabilities of 3D US against MRI for measuring articular cartilage volumes. Results indicated that the linear measurement errors for both the tilt and linear scanners were <5% of the known phantom dimensions. The volumetric measurement errors were <5% for the linear scanner and >10% (29.84%) for the tilt scanner. The percent difference between the volumes of the articular cartilage measured using 3D US and MRI of a healthy volunteer’s knee was 6.46%. The linear scanner is therefore better suited for clinical scanning than the tilt scanner due to its smaller linear and volumetric errors.
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