Page 94 - Imaging of Osteoarthritis and Rheumatoid Arthritis in Hand Joints
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                                Chapter 5
wrist coil will not be able to acquire comparable high resolution scans of finger joints. Our coil was designed to image 4 joints within one image session, without the need to adjust coil placement between image acquisitions. Single small loop coils, which are standard available from most MRI vendors could be used, but they need to be repositioned between series acquisition when more than a single joint is scanned. We used relatively long scan times to test the imaging possibilities, and future studies should explore whether it is possible to reduce the scan time. The PD sequence that was used for scoring the inter- bone distance on all 4 joints was acquired in 4:30 min (excluding pre-scans, set up time, etc), and this scan time can be reduced to make lower resolution, but still adequate coronal images. For the hrMRI cartilage images, each joint was scanned separately resulting in very thin 0.4mm slices without a gap and a total scan time of 14min for 4 joints. The size of the imaged 3D area for the PIP joints was in hindsight quite large, and further reducing the FOV in the IP joints, can decrease this scan time. Furthermore, faster and newer pulse sequences might also be used, if they can be adjusted to the small field of view.
A limitation of our study is the absence of a true gold standard. Comparison with histology is hard to obtain in our study population of healthy persons and patients with hand OA. In a previous study we found that in pre-operative obtained MRI of the CMC 1 joint in patients scheduled for trapeziectomy comparable hrMRI could detect cartilage damage with high sensitivity in comparison with histology, but might underestimate the amount of full- thickness loss when present19.The systematical difference between MRI and histology in that study was identified and only present in area’s with severe cartilage loss. As no patients with severe cartilage loss were present in our study, we expect our currents results of the MCP joints and PIP joints to be comparable with real cartilage loss. Another limitation is the inclusion of the second and third MCP and PIP joints only, as the used MRI coil was built specifically for imaging 2 MCP and 2 PIP joints. The second and third digits were chosen as these are the most affected in hand OA. However, hand OA is more often occurring in the DIP joints, than in PIP and MCP joints. We expect hrMRI to also be better than joint space narrowing detection in DIP joints, despite the smaller size of these joints.
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