Nade Sritanyaratana, Presenter: Nothing to Disclose

Pouria Mossahebi MS, Abstract Co-Author: Nothing to Disclose

John Wilson MD, MS, Abstract Co-Author: Nothing to Disclose

Alexey A. Samsonov PhD, Abstract Co-Author: Nothing to Disclose

Walter F. Block PhD, Abstract Co-Author: Research support, General Electric Company

Richard Kijowski MD, Abstract Co-Author: Nothing to Disclose

Quantitative magnetization transfer (qMT) imaging utilizes the magnetization transfer effect to probe macromolecular tissue composition typically inaccessible by conventional magnetic resonance (MR) techniques. qMT can be used to measure the fraction of protons bound to macromolecules (f), the exchange rate between mobile protons and macromolecular bound protons (k), and the T2 relaxation time of macromolecular bound protons (T2b). This study was performed to compare qMT parameters of patellar cartilage in young asymptomatic volunteers and patients with early patellofemoral osteoarthritis (OA).

An MRI examination through the patellofemoral joint was performed in the axial plane at 3.0T on 14 young asymptomatic volunteers and 11 patients with Kellgren-Lawrence grade 1 (N=6) and grade 2 (N=5) patellofemoral OA. Nine spoiled gradient recall-echo (SPGR) volumes were acquired with different MT offset frequencies and MT powers, 2 SPGR volumes were acquired for B1 error correction using actual flip angle imaging (AFI), and 4 SPGR volumes were acquired for T1 mapping using variable flip angle imaging (VFI). Total scan time was 25 minutes. The qMT parameters f, k, and T2b were iteratively fitted in MATLAB using a previously described model and then measured in regions of interest placed around the entire patellar cartilage. Mann-Whitney-Wilcoxon tests were used to compare qMT parameters between groups of subjects.

Mean f, k, and T2b within patellar cartilage for asymptomatic volunteers were 14.00±0.71%, 6.51±0.71sec-1, and 6.53±0.15µs respectively. Mean f, k, and T2b within patellar cartilage for patients with OA were 14.30±0.85%, 5.63±0.80 sec-1, and 6.83±0.14µs respectively. Patients with OA had similar f (p=0.26), significantly lower k (p=0.006), and significantly higher T2b (p=0.00006) within patellar cartilage than asymptomatic volunteers.

Patients with early patellofemoral OA have lower k and higher T2b within patellar cartilage than young asymptomatic volunteers. Additional studies are needed to investigate the mechanisms behind the observed changes in k and T2b with early cartilage degeneration.

qMT imaging is a new quantitative MR technique which has high sensitivity for detecting changes in macromolecular tissue composition associated with early cartilage degeneration.

Sritanyaratana, N, Mossahebi, P, Wilson, J, Samsonov, A, Block, W, Kijowski, R, Comparison of Quantitative Magnetization Transfer Parameters of Patellar Cartilage in Asymptomatic Volunteers and Patients with Early Osteoarthritis .  Radiological Society of North America 2013 Scientific Assembly and Annual Meeting, December 1 - December 6, 2013 ,Chicago IL. http://archive.rsna.org/2013/13020825.html