Comprehensive Cardiovascular Magnetic Resonance Tissue Characterization and Cardiotoxicity in Women With Breast Cancer.

Importance: There is a growing interest in understanding whether cardiovascular magnetic resonance (CMR) myocardial tissue characterization helps identify risk of cancer therapy-related cardiac dysfunction (CTRCD). Objective: To describe changes in CMR tissue biomarkers during breast cancer therapy and their association with CTRCD. Design, Setting, and Participants: This was a prospective, multicenter, cohort study of women with ERBB2 (formerly HER2)-positive breast cancer (stages I-III) who were scheduled to receive anthracycline and trastuzumab therapy with/without adjuvant radiotherapy and surgery. From November 7, 2013, to January 16, 2019, participants were recruited from 3 University of Toronto-affiliated hospitals. Data were analyzed from July 2021 to June 2022. Exposures: Sequential therapy with anthracyclines, trastuzumab, and radiation. Main Outcomes and Measures: CMR, high-sensitivity cardiac troponin I (hs-cTnI), and B-type natriuretic peptide (BNP) measurements were performed before anthracycline treatment, after anthracycline and before trastuzumab treatment, and at 3-month intervals during trastuzumab therapy. CMR included left ventricular (LV) volumes, LV ejection fraction (EF), myocardial strain, early gadolinium enhancement imaging to assess hyperemia (inflammation marker), native/postcontrast T1 mapping (with extracellular volume fraction [ECV]) to assess edema and/or fibrosis, T2 mapping to assess edema, and late gadolinium enhancement (LGE) to assess replacement fibrosis. CTRCD was defined using the Cardiac Review and Evaluation Committee criteria. Fixed-effects models or generalized estimating equations were used in analyses. Results: Of 136 women (mean [SD] age, 51.1 [9.2] years) recruited from 2013 to 2019, 37 (27%) developed CTRCD. Compared with baseline, tissue biomarkers of myocardial hyperemia and edema peaked after anthracycline therapy or 3 months after trastuzumab initiation as demonstrated by an increase in mean (SD) relative myocardial enhancement (baseline, 46.3% [16.8%] to peak, 56.2% [18.6%]), native T1 (1012 [26] milliseconds to 1035 [28] milliseconds), T2 (51.4 [2.2] milliseconds to 52.6 [2.2] milliseconds), and ECV (25.2% [2.4%] to 26.8% [2.7%]), with P <.001 for the entire follow-up. The observed values were mostly within the normal range, and the changes were small and recovered during follow-up. No new replacement fibrosis developed. Increase in T1, T2, and/or ECV was associated with increased ventricular volumes and BNP but not hs-cTnI level. None of the CMR tissue biomarkers were associated with changes in LVEF or myocardial strain. Change in ECV was associated with concurrent and subsequent CTRCD, but there was significant overlap between patients with and without CTRCD. Conclusions and Relevance: In women with ERBB2-positive breast cancer receiving sequential anthracycline and trastuzumab therapy, CMR tissue biomarkers suggest inflammation and edema peaking early during therapy and were associated with ventricular remodeling and BNP elevation. However, the increases in CMR biomarkers were transient, were not associated with LVEF or myocardial strain, and were not useful in identifying traditional CTRCD risk.

Impact of MRI technique on clinical decision-making in patients with liver iron overload: comparison of FerriScan- versus R2*-derived liver iron concentration.

OBJECTIVES: The purpose of this study was to compare clinical decision-making in iron overload patients using FerriScan and an R2*-based approach. METHODS: One-hundred and six patients were imaged at two consecutive timepoints (454 ± 158 days) on a 1.5-T Siemens MAGNETOM Avanto Fit scanner. For both timepoints, patients underwent the standard FerriScan MRI protocol. During the second exam, each patient additionally underwent R2*-MRI mapping. For each patient, a retrospective (simulated) decision was made to increase, decrease, or maintain chelator levels. Two different decision models were considered: The fixed threshold model assumed that chelator adjustments are based strictly on fixed liver iron concentration (LIC) thresholds. Decisions made with this model depend only on the most recent LIC value and do not require any clinician input. The second model utilized decisions made by two hematologists retrospectively based on trends between two consecutive LIC values. Agreement (κA) between hematologists (i.e., interobserver variability) was compared with the agreement (κB) between a single hematologist using the two different LIC techniques. RESULTS: Good agreement between R2*- and FerriScan-derived decisions was achieved for the fixed threshold model. True positive/negative rates were greater than 80%, and false positive/negative rates were less than 10%. ROC analysis yielded areas under the curve greater than 0.95. In the second model, the agreement in clinical decision-making for the two scenarios (κA vs. κB) was equal at the 95% confidence level. CONCLUSIONS: Switching to R2*-based LIC estimation from FerriScan has the same level of agreement in patient management decisions as does switching from one hematologist to another. KEY POINTS: • Good agreement between R2*- and FerriScan-derived decisions in liver iron overload patient management • Switching to R2*-based LIC estimation from FerriScan has the same level of agreement in patient management decisions as does switching from one hematologist to another.

Can Quantitative CMR Tissue Characterization Adequately Identify Cardiotoxicity During Chemotherapy?: Impact of Temporal and Observer Variability.

OBJECTIVES: The purpose of this study was to investigate the effect of the temporal and observer variability of cardiac magnetic resonance (CMR)-measured native T1, T2, and extracellular volume fraction (ECV) and serum biomarkers for the detection of cancer-therapeutics-related cardiac dysfunction (CTRCD). BACKGROUND: Biomarkers and serial quantitative CMR tissue characterization may help identify early myocardial changes of CTRCD, but these parameters require both accuracy and reliability. METHODS: A total of 50 participants (age 48.9 ± 12.1 years) underwent 3 CMR studies (1.5-T) and biomarker measurements (high-sensitivity troponin-I and B-type natriuretic peptide) at 3-month intervals: 20 with HER2-positive breast cancer (10 with and 10 without CTRCD), and 30 prospectively recruited healthy participants. T1 and T2 maps were obtained at 3 left ventricular short-axis locations. Temporal and observer variability were calculated as the coefficient of variation and as the standard error of the measurement (SEM) using repeated measures and 2-way analysis of variance. Minimal detected difference was defined as 2 × SEM. RESULTS: Compared with the patients without CTRCD, those with CTRCD had larger temporal change in native T1 (27.2 ms [95% confidence interval (CI): 20.8 to 39.3 ms] vs. 12.4 ms [95% CI: 9.5 to 17.9 ms]), T2 (2.0 ms [95% CI: 1.5 to 2.9 ms] vs. 1.0 ms [95% CI: 0.74 to 1.4 ms]), and ECV (2.1% [95% CI: 1.5% to 3.1%] vs. 1.0% [95% CI: 0.8% to 1.5%]). However, the temporal changes in biomarkers overlapped. The minimal detected difference for T1 (29 ms), T2 (3.0 ms), and ECV (2.2%) in healthy participants approached the mean temporal changes in patients with CTRCD. For individual patients with CTRCD, there was overlap in the temporal changes of all 3 parameters, and the variability in healthy participants with the least overlap for native T1. The interobserver/intraobserver variabilities for the CMR parameters were low (coefficient of variation 0.5% to 4.3%). CONCLUSIONS: The temporal changes in both biomarkers and tissue characterization measures in individual patients overlap with the temporal variability in healthy participants and approach the minimal detectable temporal differences. While the accuracy of the parameters awaits further study, the temporal variability of these methods may pose challenges to routine clinical application in individual patients receiving cancer therapy.

Bone Marrow Mesenchymal Stromal Cell Treatment in Patients with Osteoarthritis Results in Overall Improvement in Pain and Symptoms and Reduces Synovial Inflammation.

Patients with late-stage Kellgren-Lawrence knee osteoarthritis received a single intra-articular injection of 1, 10, or 50 million bone marrow mesenchymal stromal cells (BM-MSCs) in a phase I/IIa trial to assess safety and efficacy using a broad toolset of analytical methods. Besides safety, outcomes included patient-reported outcome measures (PROMs): Knee Injury and Osteoarthritis Outcome Score (KOOS) and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC); contrast-enhanced magnetic resonance imaging (MRI) for cartilage morphology (Whole Organ MRI Scores [WORMS]), collagen content (T2 scores), and synovitis; and inflammation and cartilage turnover biomarkers, all over 12 months. BM-MSCs were characterized by a panel of anti-inflammatory markers to predict clinical efficacy. There were no serious adverse events, although four patients had minor, transient adverse events. There were significant overall improvements in KOOS pain, symptoms, quality of life, and WOMAC stiffness relative to baseline; the 50 million dose achieved clinically relevant improvements across most PROMs. WORMS and T2 scores did not change relative to baseline. However, cartilage catabolic biomarkers and MRI synovitis were significantly lower at higher doses. Pro-inflammatory monocytes/macrophages and interleukin 12 levels decreased in the synovial fluid after MSC injection. The panel of BM-MSC anti-inflammatory markers was strongly predictive of PROMs over 12 months. Autologous BM-MSCs are safe and result in significant improvements in PROMs at 12 months. Our analytical tools provide important insights into BM-MSC dosing and BM-MSC reduction of synovial inflammation and cartilage degradation and provide a highly predictive donor selection criterion that will be critical in translating MSC therapy for osteoarthritis. Stem Cells Translational Medicine 2019;8:746&757.

Prospective Evaluation of an R2* Method for Assessing Liver Iron Concentration (LIC) Against FerriScan: Derivation of the Calibration Curve and Characterization of the Nature and Source of Uncertainty in the Relationship.

BACKGROUND: FerriScan is the method-of-choice for noninvasive liver iron concentration (LIC) quantification. However, it has a number of drawbacks including cost and expediency. PURPOSE/HYPOTHESIS: To characterize an R2*-based MRI technique that may potentially be used as an alternative to FerriScan. This was accomplished through the derivation of a calibration curve that characterized the relationship between FerriScan-derived LIC and R2*. The nature and source of uncertainty in this curve were investigated. It was hypothesized that the source of uncertainty is heterogeneity of LIC across the liver. STUDY TYPE: Prospective. SUBJECTS: In all, 125 patients (69 women, 56 men) undergoing chelation treatment for iron overload prospectively underwent FerriScan and R2* MRI during the same exam. FIELD STRENGTH/SEQUENCE: Pulse sequences included 2D multislice spin-echo pulse for FerriScan, and a prototype 3D 6-echo gradient echo acquisition for R2* mapping at 1.5T. ASSESSMENT: A linear calibration curve was derived from the relationship between FerriScan-derived LIC estimates and R2* through least-squares fitting. STATISTICAL TESTS: The nature of the uncertainty in the curve was characterized through tests of normality and homoscedasticity. The source of uncertainty was tested by comparing the magnitude of LIC variation over the FerriScan ROI to the observed uncertainty in the R2*-derived LIC estimates. RESULTS: A linear relationship between logarithmically transformed FerriScan-derived LIC and R2* (log{FerriScan-derived LIC} = 1.029 log{R2*} - 3.822) was confirmed. Uncertainty was random, with a behaviour that was normal and homoscedastic. The source of uncertainty was confirmed as iron heterogeneity across the liver. The nontransformed calibration curve was: FerriScan-derived LIC = 0.0266⋅R2*, with a constant coefficient-of-variation of 0.32. DATA CONCLUSION: FerriScan and R2* techniques were found to provide equivalent quantification of LIC in this study. Any difference in accuracy or precision was at a level lower than the uncertainty caused by variation in LIC over the liver. LEVEL OF EVIDENCE: 1 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2019;49:1467-1474.

Accuracy of magnetic resonance imaging for measuring maturing cartilage: A phantom study

OBJECTIVES: To evaluate the accuracy of magnetic resonance imaging measurements of cartilage tissue-mimicking phantoms and to determine a combination of magnetic resonance imaging parameters to optimize accuracy while minimizing scan time. METHOD: Edge dimensions from 4 rectangular agar phantoms ranging from 10.5 to 14.5 mm in length and 1.25 to 5.5 mm in width were independently measured by two readers using a steel ruler. Coronal T1 spin echo (T1 SE), fast spoiled gradient-recalled echo (FSPGR) and multiplanar gradient-recalled echo (GRE MPGR) sequences were used to obtain phantom images on a 1.5-T scanner. RESULTS: Inter- and intra-reader reliability were high for both direct measurements and for magnetic resonance imaging measurements of phantoms. Statistically significant differences were noted between the mean direct measurements and the mean magnetic resonance imaging measurements for phantom 1 when using a GRE MPGR sequence (512x512 pixels, 1.5-mm slice thickness, 5:49 min scan time), while borderline differences were noted for T1 SE sequences with the following parameters: 320x320 pixels, 1.5-mm slice thickness, 6:11 min scan time; 320x320 pixels, 4-mm slice thickness, 6:11 min scan time; and 512x512 pixels, 1.5-mm slice thickness, 9:48 min scan time. Borderline differences were also noted when using a FSPGR sequence with 512x512 pixels, a 1.5-mm slice thickness and a 3:36 min scan time. CONCLUSIONS: FSPGR sequences, regardless of the magnetic resonance imaging parameter combination used, provided accurate measurements. The GRE MPGR sequence using 512x512 pixels, a 1.5-mm slice thickness and a 5:49 min scan time and, to a lesser degree, all tested T1 SE sequences produced suboptimal accuracy when measuring the widest phantom.

Magnetic resonance imaging assessment of spinal cord and cauda equina motion in supine patients with spinal metastases planned for spine stereotactic body radiation therapy.

PURPOSE: To assess motion of the spinal cord and cauda equina, which are critical neural tissues (CNT), which is important when evaluating the planning organ-at-risk margin required for stereotactic body radiation therapy. METHODS AND MATERIALS: We analyzed CNT motion in 65 patients with spinal metastases (11 cervical, 39 thoracic, and 24 lumbar spinal segments) in the supine position using dynamic axial and sagittal magnetic resonance imaging (dMRI, 3T Verio, Siemens) over a 137-second interval. Motion was segregated according to physiologic cardiorespiratory oscillatory motion (characterized by the average root mean square deviation) and random bulk shifts associated with gross patient motion (characterized by the range). Displacement was evaluated in the anteroposterior (AP), lateral (LR), and superior-inferior (SI) directions by use of a correlation coefficient template matching algorithm, with quantification of random motion measure error over 3 separate trials. Statistical significance was defined according to P<.05. RESULTS: In the AP, LR, and SI directions, significant oscillatory motion was observed in 39.2%, 35.1%, and 10.8% of spinal segments, respectively, and significant bulk motions in all cases. The median oscillatory CNT motions in the AP, LR, and SI directions were 0.16 mm, 0.17 mm, and 0.44 mm, respectively, and the maximal statistically significant oscillatory motions were 0.39 mm, 0.41 mm, and 0.77 mm, respectively. The median bulk displacements in the AP, LR, and SI directions were 0.51 mm, 0.59 mm, and 0.66 mm, and the maximal statistically significant displacements were 2.21 mm, 2.87 mm, and 3.90 mm, respectively. In the AP, LR, and SI directions, bulk displacements were greater than 1.5 mm in 5.4%, 9.0%, and 14.9% of spinal segments, respectively. No significant differences in axial motion were observed according to cord level or cauda equina. CONCLUSIONS: Oscillatory CNT motion was observed to be relatively minor. Our results support the importance of controlling bulk patient motion and the practice of applying a planning organ-at-risk margin.

Mechatronic system for in-bore MRI-guided insertion of needles to the prostate: An in vivo needle guidance accuracy study.

BACKGROUND: To present our experiences in initial clinical evaluation of a novel mechatronic system for in-bore guidance of needles to the prostate for MRI-guided prostate interventions in 10 patients. We report accuracy of this device in the context of focal laser ablation therapy for localized prostate cancer. METHODS: An MRI-compatible needle guidance device was developed for transperineal prostate interventions. Ten patients underwent MRI-guided focal laser ablation therapy with device-mediated laser fiber delivery. We recorded needle guidance error and needle delivery time. RESULTS: A total of 37 needle insertions were evaluated. Median needle guidance error was 3.5 mm (interquartile range, 2.1-5.4 mm), and median needle delivery time was 9 min (interquartile range, 6.5-12 min). CONCLUSION: This system provides a reliable method of accurately aligning needle guides for in-bore transperineal needle delivery to the prostate.

Construction and evaluation of an anatomically correct multi-image modality compatible phantom for prostate cancer focal ablation.

PURPOSE: Focal therapy using lasers is emerging as an alternative strategy for prostate cancer treatment. However, to our knowledge no anatomically correct models are available to test imaging and ablation techniques. Animal models present ethical, anatomical and cost challenges. We designed and validated an inexpensive but anatomically correct prostate phantom incorporating tumor, rectum and urethra that can be used for simulated and experimental magnetic resonance guided focal intervention. Our secondary aim was to asses the phantom using other imaging modalities. MATERIALS AND METHODS: The phantom, which was constructed of ballistic gel, includes an 80 gm prostate with urethra, tumor, perineum and rectum. Gadolinium was added to make the gel visible to magnetic resonance imaging. To recreate a tumor an irregularly shaped 5 cc volume of coagulable gel was inserted into the prostate phantom. The phantom was evaluated using magnetic resonance, computerized tomography and transrectal ultrasound. Thermal ablation was delivered via interstitial placement of laser fibers. Magnetic resonance thermometry was done to record real-time tissue temperatures during thermal ablation. RESULTS: With all modalities tested the phantom emulated human prostate anatomy. The coagulable gel tumor allowed us to generate focal thermal lesions. The phantom had magnetic resonance imaging properties comparable to in vivo properties, allowing ablative zones to be accurately assessed and magnetic resonance thermometry to be done. CONCLUSIONS: The phantom is a useful tool to test different aspects of thermal focal ablation for prostate cancer using multiple imaging modalities, particularly magnetic resonance. It is inexpensive and easily constructed, and may be considered a valuable model to train on and teach focal therapy.

Synthetic-echo time postprocessing technique for generating images with variable T2-weighted contrast: diagnosis of meniscal and cartilage abnormalities of the knee.

PURPOSE: To assess the feasibility and accuracy of a synthetic-echo time (TE) magnetic resonance (MR) postprocessing technique for the diagnostic evaluation of abnormalities of menisci and articular cartilage in the knee. MATERIALS AND METHODS: This study was approved by the institutional review board. Twenty-four patients (three women, 21 men; mean age, 44.8 years) gave informed written consent to prospectively undergo evaluation of their knees (10 left and 14 right knees) with standard sagittal intermediate-weighted (repetition time msec/TE msec, 2200/17) and fat-saturated T2-weighted (3600/88) fast spin-echo sequences. In addition, sagittal multiecho fast gradient-echo sequences were performed for the generation of synthetic-TE images with variable T2- or T2(*)-weighted contrast by using a newly developed synthetic-TE analysis tool that was incorporated directly into the picture archiving and communication system. Sensitivity, specificity, and accuracy values for detection of lesions in menisci and articular cartilage were calculated by using findings at surgery as reference standard. RESULTS: The standard intermediate-weighted and fat-suppressed T2-weighted MR sequences had overall sensitivity, specificity, and accuracy values of 100% and 100%, 88% and 93%, and 95% and 95% for the diagnosis of tears of medial and lateral menisci, respectively, as well as sensitivity, specificity, and accuracy values of 82%, 97%, and 95%, respectively, for articular cartilage defects. Corresponding sensitivity, specificity, and accuracy values for multiecho MR imaging with synthetic-TE MR image generation were 92% and 100%, 88% and 87%, and 90% and 90% for the diagnosis of tears of medial and lateral menisci, respectively, as well as sensitivity, specificity, and accuracy values of 70%, 99%, and 95%, respectively, for articular cartilage defects. CONCLUSION: For the evaluation of menisci and articular cartilage, images generated with the synthetic-TE technique are a potentially viable alternative to standard T2-weighted images obtained at different TEs. Furthermore, the synthetic-TE approach allowed assessment of abnormalities of menisci and articular cartilage with high sensitivity and specificity.

Quantitative assessment of myocardial T2 relaxation times in cardiac amyloidosis.

PURPOSE: To evaluate cardiac MRI (CMR) in the diagnosis of cardiac amyloidosis by comparing the T2 relaxation times of left ventricular myocardium in a pilot patient group to a normal range established in healthy controls. MATERIALS AND METHODS: Forty-nine patients with suspected amyloidosis-related cardiomyopathy underwent comprehensive CMR examination, which included assessment of myocardial T2 relaxation times, ventricular function, resting myocardial perfusion, and late gadolinium enhancement (LGE) imaging. T2-weighted basal, mid, and apical left ventricular slices were acquired in each patient using a multislice T2 magnetization preparation spiral sequence. Slice averaged T2 relaxation times were subsequently calculated offline and compared to the previously established normal range. RESULTS: Twelve of the 49 patients were confirmed to have cardiac amyloidosis by biopsy. There was no difference in mean T2 relaxation times between the amyloid cases and normal controls (51.3 +/- 8.1 vs. 52.1 +/- 3.1 msec, P = 0.63). Eleven of the 12 amyloid patients had abnormal findings by CMR, eight having LGE involving either ventricles or atria and four demonstrating resting subendocardial perfusion defects. CONCLUSION: CMR is a potentially valuable tool in the diagnosis of cardiac amyloidosis. However, calculation of myocardial T2 relaxation times does not appear useful in distinguishing areas of amyloid deposition from normal myocardium.

Validation of supervised automated algorithm for fast quantitative evaluation of organ motion on magnetic resonance imaging.

PURPOSE: To validate a correlation coefficient template-matching algorithm applied to the supervised automated quantification of abdominal-pelvic organ motion captured on time-resolved magnetic resonance imaging. METHODS AND MATERIALS: Magnetic resonance images of 21 patients across four anatomic sites were analyzed. Representative anatomic points of interest were chosen as surrogates for organ motion. The point of interest displacements across each image frame relative to baseline were quantified manually and through the use of a template-matching software tool, termed "Motiontrack." Automated and manually acquired displacement measures, as well as the standard deviation of intrafraction motion, were compared for each image frame and for each patient. RESULTS: Discrepancies between the automated and manual displacements of > or =2 mm were uncommon, ranging in frequency of 0-9.7% (liver and prostate, respectively). The standard deviations of intrafraction motion measured with each method correlated highly (r = 0.99). Considerable interpatient variability in organ motion was demonstrated by a wide range of standard deviations in the liver (1.4-7.5 mm), uterus (1.1-8.4 mm), and prostate gland (0.8-2.7 mm). The automated algorithm performed successfully in all patients but 1 and substantially improved efficiency compared with manual quantification techniques (5 min vs. 60-90 min). CONCLUSION: Supervised automated quantification of organ motion captured on magnetic resonance imaging using a correlation coefficient template-matching algorithm was efficient, accurate, and may play an important role in off-line adaptive approaches to intrafraction motion management.

Free-breathing motion compensation using template matching: a technique allowing for tracer kinetic modeling of liver metastases.

Modeling tracer kinetics from dynamic magnetic resonance imaging (dMRI) to understand microvascular characteristics typically requires acquisitions longer than 1 breath-hold. This has limited the application of dMRI in assessment of the upper abdomen. Here we present a template-based motion correction strategy for dMRI of liver metastases based on the correlation coefficient (CC), originally developed for tracking coronary arteries. This postprocessing method allows patient free breathing during sagittal dMRI acquisition and allows a more precise parametric mapping using tracer kinetic models. In a study of 6 subjects, a 64 x 64 template was accurately tracked retrospectively with mean CC = 0.72 +/- 0.07. Mean superior-inferior displacement tracked was 1.82 +/- 1.20 pixels, whereas mean anterior-posterior displacement was 7.72 +/- 4.58 pixels. Application of the CC method significantly improved the global fit (chi2) of a tracer kinetic model throughout tumor regions. Therefore, use of the CC postprocessing method for dMRI scans can improve the precision of dMRI tracer kinetic models.

Cartilage T2 assessment: differentiation of normal hyaline cartilage and reparative tissue after arthroscopic cartilage repair in equine subjects.

PURPOSE: To prospectively assess T2 mapping characteristics of normal articular cartilage and of cartilage at sites of arthroscopic repair, including comparison with histologic results and collagen organization assessed at polarized light microscopy (PLM). MATERIALS AND METHODS: Study protocol was compliant with the Canadian Council on Animal Care Guidelines and approved by the institutional animal care committee. Arthroscopic osteochondral autograft transplantation (OAT) and microfracture arthroplasty (MFx) were performed in knees of 10 equine subjects (seven female, three male; age range, 3-5 years). A site of arthroscopically normal cartilage was documented in each joint as a control site. Joints were harvested at 12 (n = 5) and 24 (n = 5) weeks postoperatively and were imaged at 1.5-T magnetic resonance (MR) with a 10-echo sagittal fast spin-echo acquisition. T2 maps of each site (21 OAT harvest, 10 MFx, 12 OAT plug, and 10 control sites) were calculated with linear least-squares curve fitting. Cartilage T2 maps were qualitatively graded as "organized" (normal transition of low-to-high T2 signal from deep to superficial cartilage zones) or "disorganized." Quantitative mean T2 values were calculated for deep, middle, and superficial cartilage at each location. Results were compared with histologic and PLM assessments by using kappa analysis. RESULTS: T2 maps were qualitatively graded as organized at 20 of 53 sites and as disorganized at 33 sites. Perfect agreement was seen between organized T2 and histologic findings of hyaline cartilage and between disorganized T2 and histologic findings of fibrous reparative tissue (kappa = 1.0). Strong agreement was seen between organized T2 and normal PLM findings and between disorganized T2 and abnormal PLM findings (kappa = .92). Quantitative assessment of the deep, middle, and superficial cartilage, respectively, showed mean T2 values of 53.3, 58.6, and 54.9 msec at reparative fibrous tissue sites and 40.7, 53.6, and 61.6 msec at hyaline cartilage sites. A significant trend of increasing T2 values (from deep to superficial) was found in hyaline cartilage (P < .01). Fibrous tissue sites had no significant change with depth (P > .59). CONCLUSION: Qualitative and quantitative T2 mapping helped differentiate hyaline cartilage from reparative fibrocartilage after cartilage repair at 1.5-T MR imaging.