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Farshad-Amacker N.A.,MRI Research Laboratory | Koff M.F.,MRI Research Laboratory | Dyke J.P.,New York Medical College | Lazaro L.E.,Hospital of Special Surgery | And 3 more authors.
HSS Journal | Year: 2016

Background: Evaluating postoperative femoral neck facture (FNF) with metal fixation hardware is commonly performed using radiographs. MRI has greater sensitivity and specificity to evaluate osteonecrosis (ON) but is often challenging due to the image distortion caused by metallic hardware. Questions/Purposes: The aim of this study is to compare fast spin-echo (FSE) and multi-acquisition variable-resonance image combination (MAVRIC) sequences in assessing ON following metallic fixation of FNF and determining feasibility of semi-quantitative perfusion using MAVRIC. Methods: Radiography and MRI were performed at 3 and 12 months postoperatively, using FSE and pre- and post-gadolinium contrast MAVRIC sequences in 21 FNF patients. The presence and volume of ON were recorded. Signal intensity (SI) enhancement was measured on the MAVRIC sequences within the center and rim of ON; with the ilium and femoral diaphysis as controls. The detection rate of ON between MAVRIC and FSE images was evaluated as the difference of percent enhancement across the defined regions of interest. Results: ON was detected in 0% of radiographs, in 67% of FSE, and in 76% of MAVRIC images at 3 months follow-up, with similar results at 12 months. MAVRIC images had larger ON volume than FSE images at both time points. A significant percentage SI enhancement was only detected in the ON rim. Conclusion: Radiographs could not detect ON following metallic fixation of FNF. MAVRIC is more sensitive than FSE for determining the volume of ON. SI measurements using MAVRIC may provide an indirect assessment of perfusion. © 2015, Hospital for Special Surgery.

Farshad-Amacker N.A.,MRI Research Laboratory | Potter H.G.,MRI Research Laboratory
Journal of Magnetic Resonance Imaging | Year: 2013

Knee ligament instability may lead to meniscal and chondral damage, resulting in early osteoarthritis. Due to its superior soft tissue contrast and avoidance of harmful ionizing radiation, MRI has become the most important imaging modality for early recognition of structural defects of the knee joint. This review aims to the understanding of MRI appearances of knee ligament structures associated with knee instability, and to review the common patterns of altered knee mechanics that lead to ligament failure. Normal anatomy of the knee ligaments, pathologic conditions, and postsurgical appearances of the anterior cruciate ligament, posterior cruciate ligament, medial collateral ligament, and posterolateral corner are described. Copyright © 2013 Wiley Periodicals, Inc.

Koff M.F.,MRI Research Laboratory | Shah P.,MRI Research Laboratory | Pownder S.,MRI Research Laboratory | Romero B.,Cornell University | And 6 more authors.
Osteoarthritis and Cartilage | Year: 2013

Objective: To correlate meniscal T2* relaxation times using ultra-short echo time (UTE) magnetic resonance imaging (MRI) with quantitative microscopic methods, and to determine the effect of meniscal repair on post-operative cartilage T2 values. Design: A medial meniscal tear was created and repaired in the anterior horn of one limb of 28 crossbred mature ewes. MR scans for morphological evaluation, meniscal T2* values, and cartilage T2 values were acquired at 0, 4 and 8 months post-operatively for the Tear and Non-Op limb. Samples of menisci from both limbs were analyzed using multiphoton microscopy (MPM) analysis and biomechanical testing. Results: Significantly prolonged meniscal T2* values were found in repaired limbs than in control limbs, P<0.0001. No regional differences of T2* were detected for either the repaired or control limbs in the anterior horn. Repaired limbs had prolonged cartilage T2 values, primarily anteriorly, and tended to have lower biomechanical force to failure at 8 months than Non-Op limbs. MPM autofluorescence and second harmonic generation data correlated with T2* values at 8 months (ρ=-0.48, P=0.06). Conclusions: T2*mapping is sensitive to detecting temporal and zonal differences of meniscal structure and composition. Meniscal MPM and cartilage T2 values indicate changes in tissue integrity in the presence of meniscal repair. © 2013 Osteoarthritis Research Society International.

Sneag D.B.,Hospital for Special Surgery | Shah P.,MRI Research Laboratory | Koff M.F.,MRI Research Laboratory | Lim W.Y.,MRI Research Laboratory | And 3 more authors.
HSS Journal | Year: 2015

Background: Magnetic resonance imaging (MRI) visualization of meniscal signal is particularly challenging as the highly organized ultrastructure of meniscal fibrocartilage yields very short T2 values (∼6 ms) and a paucity of signal intensity during conventional image acquisition. Question/Purpose: The purpose of this study was to evaluate the feasibility of imaging postoperative menisci using an experimental, quantitative ultrashort echo time (UTE) MRI pulse sequence. This sequence acquires short echo images (echo time (TE) ∼0.3 ms) to produce multi-echo images for quantitative T2* calculations that provide an objective measure of collagen organization. Patients and Methods: MRI scans of the knee were acquired at 6- and 12-month intervals on a clinical 3.0 T scanner following meniscal surgery in eight patients (ages 13–41), four of whom underwent repair and the other four partial meniscectomy. Conventional MRI sequences were qualitatively evaluated for meniscal morphology and signal and correlated with quantitative UTE results. Results: A wide range of mean T2* values for both postsurgical groups was measured, and these values changed for each patient between the 6- and 12-month intervals. In many instances, the UTE sequence demonstrated quantitative differences between the two time intervals that were not detected with conventional sequences. Conclusions: This pilot study presents preliminary, observational data to be used as a baseline for future studies. Although the T2* values did not reveal a trend in either group or correlate with expected signal changes on conventional MRI, we speculate that the UTE sequence may detect ultrastructural alterations in meniscal composition that are otherwise not perceived with routine fast spin echo (FSE) sequences. © 2014, Hospital for Special Surgery.

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