Ultrashort Time to Echo Magnetic Resonance Evaluation of Calcium Pyrophosphate Crystal Deposition in Human Menisci

Objectives In human menisci, we aimed to investigate whether calcium pyrophosphate crystal deposition (CPPD) affects biomechanical and quantitative MR properties, and their zonal distribution. Materials and Methods From 9 cadaveric knees, sectioned triangular meniscus pieces were harvested. Samples were classified into "normal" or "CPPD" groups based upon visual inspection. Micro computed tomography scan verified CPPD. Using magnetic resonance imaging, ultrashort echo time (UTE) T2* and spin echo (SE) T2, quantitative values in 3 zones (red, red-white, and white) were determined. Using biomechanical test, indentation forces in the same zones were determined. Effects of CPPD and meniscal zone on indentation force and quantitative MR values were compared. Results On UTE MRI scans, CPPD-affected menisci exhibited punctate dark regions, found mostly (92%) in avascular white and red-white zones. Indentation forces were significantly higher for CPPD samples in the red-white (all P 0.2). Similarly, UTE T2* red zone values were similar between both groups (~6.6 milliseconds, P = 0.8), whereas in the red-white and white zones, CPPD samples had significantly lower values (~5.1 milliseconds, P = 0.005 to 0.007). In contrast, SE T2 values showed no difference with CPPD (P = 0.12 to 0.16). UTE T2*, but not SE T2, correlated significantly with indentation force (R = −0.29, P = 0.009). Conclusions Dark CPP deposits were detectable on UTE images featuring high signal intensity from surrounding meniscal tissue. Preliminary results indicate that CPP deposits were almost exclusively found in the avascular zones. Compared with normal, CPPD menisci featured higher indentation stiffness and lower UTE T2* values in the affected zones. Received for publication November 6, 2018; and accepted for publication, after revision, December 18, 2018. Conflicts of interest and sources of funding: The study was funded by grants from VA (I01 CX000625) and NIH NIAMS (R01 AR064321) in support of Prof C.B. Chung, and NIH NIAMS (R01 AR066622). Furthermore, this work was supported by grant funding from RSNA Research Fellow Grant (RF1730), Swiss National Science Foundation (P2SKP3_168412), and Swiss Society of Radiology in support of Dr Finkenstaedt. We disclose any financial support or author involvement with organization(s) with financial interest in the subject matter. Its contents are solely the responsibility of the authors and do not necessarily represent the official views of the National Institutes of Health. Correspondence to: Christine B. Chung, MD, Department of Radiology, VA San Diego Healthcare System, 3350 La Jolla Village Dr, MC-114, San Diego, CA 92161. E-mail: cbchung@ucsd.edu. Copyright © 2019 Wolters Kluwer Health, Inc. All rights reserved.

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