Faculty Bibliography

Currently, clinical determination of pathologic fracture risk in the hip is conducted using measures of defect size and shape in the stance loading condition. However, these measures often do not consider how changing lesion locations or how various loading conditions impact bone strength. The goal of this study was to determine the impact of defect location on bone strength parameters in both the sideways fall and stance-loading conditions. We recruited 20 female subjects aged 48-77 years for this study and performed MRI of the proximal femur. Using these images, we simulated 10-mm pathologic defects in greater trochanter, superior, middle, and inferior femoral head, superior, middle, and inferior femoral neck, and lateral, middle, and medial proximal diaphysis to determine the effect of defect location on change in bone strength by performing finite element analysis. We compared the effect of each osteolytic lesion on bone stiffness, strength, resilience, and toughness. For the sideways fall loading, defects in the inferior femoral head (12.21%) and in the greater trochanter (6.43%) resulted in the greatest overall reduction in bone strength. For the stance loading, defects in the mid femoral head (-7.91%) and superior femoral head (-7.82%) resulted in the greatest overall reduction in bone strength. Changes in stiffness, yield force, ultimate force, resilience, and toughness were not found to be significantly correlated between the sideways fall and stance-loading for the majority of defect locations, suggesting that calculations based on the stance-loading condition are not predictive of the change in bone strength experienced in the sideways fall condition. While stiffness was significantly related to yield force (R²â€¯> 0.82), overall force (R²â€¯> 0.59), and resilience (R²â€¯> 0.55), in both, the stance-loading and sideways fall conditions for most defect locations, stiffness was not significantly related to toughness. Therefore, structure-dependent measure such as stiffness may not fully explain the post-yield measures, which depend on material failure properties. The data showed that MRI-based models have the sensitivity to determine the effect of pathologic lesions on bone strength.

MR imaging is an indispensable instrument for the diagnosis of musculoskeletal diseases. In vivo MR imaging at 7T offers many advantages, including increased signal-to-noise ratio, higher spatial resolution, improved spectral resolution for spectroscopy, improved sensitivity for X-nucleus imaging, and decreased image acquisition times. There are also however technical challenges of imaging at a higher field strength compared with 1.5 and 3T MR imaging systems. We discuss the many potential opportunities as well as the challenges presented by 7T MR imaging systems and highlight recent developments in in vivo research imaging of musculoskeletal applications in general and cartilage, skeletal muscle, and bone in particular.

Idiopathic granulomatous mastitis (IGM) is a rare benign inflammatory breast entity characterized by lobulocentric granulomas. IGM has a persistent or recurrent disease course and affects parous premenopausal women with a history of lactation. It has also been associated with hyperprolactinemia. The most common clinical sign is a palpable tender mass. However, the nonspecific manifestations and varied demographic features of this condition, as well as the other similar-appearing and superimposed breast entities, pose substantial diagnostic challenges. Entities with similar manifestations include inflammatory breast cancer (IBC), infective mastitis, foreign body injection granulomas, mammary duct ectasia, diabetic fibrous mastopathy, and systemic granulomatous processes. The strategy for imaging IGM depends on patient age, clinical manifestations, and risk factors. Targeted ultrasonography, mammography, and less commonly, magnetic resonance imaging have proven to be useful for imaging evaluation. Core-needle biopsy, with or without fine-needle aspiration for cytopathologic examination, and culture analysis are usually required to exclude IBC and other benign inflammatory breast processes. Patients with IGM have an excellent prognosis when they are appropriately treated with oral steroids or second-line immunosuppressive and prolactin-lowering medications. However, surgical excision may be an option for patients in whom medication therapy is unsuccessful. Imaging surveillance can be offered to patients with incidentally encountered IGM or mild symptoms. Clinical suspicion for this rare disease and the breast imager's prompt diagnosis can lead to an improved patient outcome. The purpose of this article is to review the imaging manifestations of IGM in a multimodality case-based format and to describe relevant clinical and imaging-based differential diagnoses. The associated pitfalls, epidemiologic and histopathologic factors, clinical manifestations, natural course, and management of IGM also are discussed. ^©RSNA, 2018.

Cartilage injuries are common, especially in athletes. Because these injuries frequently affect young patients, and they have the potential to progress to osteoarthritis, treatment to alleviate symptoms and delay joint degeneration is warranted. A number of surgical techniques are available to treat focal chondral defects, including marrow stimulation, osteochondral auto- and allografting, and autologous chondrocyte implantation. Although arthroscopy is considered the standard of reference for the evaluation of cartilage before and after repair, it is invasive with associated morbidity and cannot adequately depict the deep cartilage layer and underlying bone. Magnetic resonance (MR) imaging provides unparalleled noninvasive assessment of the repair site and all other joint tissues. MR observation of cartilage repair tissue is a well-established semiquantitative scoring system for repair tissue that has primarily been used in clinical research studies. The cartilage repair osteoarthritis knee score (CROAKS) optimizes comprehensive morphologic assessment of the knee joint after cartilage repair. Furthermore, quantitative, compositional MR imaging measurements (eg, T2, T2*, T1ρ), delayed gadolinium-enhanced MR imaging of cartilage (dGEMRIC), and sodium imaging are available for biochemical assessment. These quantitative MR imaging techniques help assess collagen content and orientation, water content, and glycosaminoglycan and/or proteoglycan content both in the repair tissue as it matures and in the "native" cartilage. In this review, the authors discuss the principles of state-of-the-art morphologic and compositional MR imaging techniques for imaging of cartilage repair and their application to longitudinal studies.

Arthroscopy-based semiquantitative scoring systems such as Outerbridge and Noyes' scores were the first to be developed for the purpose of grading cartilage defects. As magnetic resonance imaging (MRI) became available for evaluation of the osteoarthritic knee joint, these systems were adapted for use with MRI. Later on, grading methods such as the Whole Organ Magnetic Resonance Score, the Boston-Leeds Osteoarthritis Knee Score and the MRI Osteoarthritis Knee Score were designed specifically for performing whole-organ assessment of the knee joint structures, including cartilage. Cartilage grades on MRI obtained with these scoring systems represent optimal outcome measures for longitudinal studies, and are designed to enhance understanding of the knee osteoarthritis disease process. The purpose of this narrative review is to describe cartilage assessment in knee osteoarthritis using currently available MRI-based semiquantitative whole-organ scoring systems, and to provide an update on the risk factors for cartilage loss in knee osteoarthritis as assessed with these scoring systems.

PURPOSE/OBJECTIVE:To describe a scoring system for quantification of cartilage lesions (Cartilage Lesion Score [CaLS]), to determine its reproducibility, to examine the association of CaLS-detected longitudinal change with known risk factors for osteoarthritis (OA) progression by comparing a group of subjects with OA risk factors with a group of subjects without OA risk factors, and to compare the CaLS system with the established semiquantitative Whole-Organ Magnetic Resonance Imaging Score (WORMS) and Boston-Leeds Osteoarthritis Knee Score (BLOKS) systems in terms of detection of cartilage defect progression. MATERIALS AND METHODS/METHODS:All subjects provided written informed consent, and the local institutional review board approved this HIPAA-compliant study. Fifty-two subjects with and 25 subjects without risk factors for knee OA were randomly selected from the Osteoarthritis Initiative. Inclusion criteria were age of 45-60 years, body mass index of 19-27 kg/m(2), and no knee pain or OA on radiographs at baseline. Baseline and 24-month follow-up right knee 3-T magnetic resonance images were analyzed with WORMS, BLOKS, and CaLS systems. Progression of cartilage lesions with each scoring system was compared by using multilevel mixed-effects linear-regression models. κ values were calculated to determine reliability. RESULTS:Intraclass coefficient values for inter- and intraobserver reliability of the CaLS system were 0.86 and 0.91, respectively. Interobserver κ value range for individual features was 0.81-0.94. The CaLS system enabled significantly higher detection of cartilage lesion progression than did WORMS or BLOKS systems (P < .001); 51.8% (56 of 108), 17.6% (19 of 108), and 13.0% (14 of 108) of the lesions progressed when analyzed with the CaLS, WORMS, and BLOKS systems, respectively. With the CaLS system, subjects with OA risk factors had significantly higher odds of progression than did subjects without risk factors (odds ratio, 2.78; P = .005). CONCLUSION/CONCLUSIONS:The CaLS system is a reproducible scoring system for cartilage lesions that yields an improved detection rate for monitoring progression when compared with detection rates of semiquantitative WORMS and BLOKS systems.

PURPOSE/OBJECTIVE:To study the natural evolution of cartilage T2 relaxation times in knees with various extents of morphological cartilage abnormalities, assessed with 3 Tesla MRI from the Osteoarthritis Initiative. MATERIALS AND METHODS/METHODS:Right knee MRIs of 245, 45- to 60-year-old individuals without radiographic osteoarthritis (OA) were included. Cartilage was segmented and T2 maps were generated in five compartments (patella, medial and lateral femoral condyle, medial, and lateral tibia) at baseline and 2-year follow-up. We examined the association of T2 values and 2-year change of T2 values with various Whole-Organ MR Imaging Scores (WORMS). Statistical analysis was performed with analysis of variance and Students t-tests. RESULTS:Higher baseline T2 was associated with more severe cartilage defects at baseline and subsequent cartilage loss (P < 0.001). However, longitudinal T2 change was inversely associated with both baseline (P = 0.038) and follow-up (P = 0.002) severity of cartilage defects. Knees that developed new cartilage defects had smaller increases in T2 than subjects without defects (P = 0.045). Individuals with higher baseline T2 showed smaller T2 increases over time (P < 0.001). CONCLUSION/CONCLUSIONS:An inverse correlation of longitudinal T2 changes versus baseline T2 values and morphological cartilage abnormalities suggests that once morphological cartilage defects occur, T2 values may be limited for evaluating further cartilage degradation.

OBJECTIVE:To evaluate the association of baseline frequent knee bending activities with the prevalence and progression of cartilage and meniscal abnormalities over 3 years and to assess the effect of frequent knee bending on the different knee compartments with 3T magnetic resonance imaging (MRI). METHODS:We studied 115 subjects without radiographic knee osteoarthritis (OA) but with risk factors for OA from the Osteoarthritis Initiative database. The inclusion criteria at baseline were age 45-55 years, body mass index of 19-27 kg/m(2) , Western Ontario and McMaster Universities Osteoarthritis Index pain score of 0, and Kellgren/Lawrence grade <2. Knee bending activities (kneeling, squatting, stair climbing, and weight lifting) were assessed by questionnaire at the baseline clinic visit. Cartilage and meniscal abnormalities were graded using the Whole-Organ MRI Score. Logistic regression was used to determine the association of frequent knee bending with cartilage and meniscal abnormalities. RESULTS:Frequent knee bending activities were associated with an increased risk of prevalent cartilage lesions (odds ratio [OR] 3.63, 95% confidence interval [95% CI] 1.39-9.52), in particular in the patellofemoral compartment (OR 3.09, 95% CI 1.22-7.79). The increase in risk was higher in subjects involved in ≥2 knee bending activities. At 3-year followup, individuals reporting frequent knee bending were more likely to show progression of cartilage damage (OR 4.12, 95% CI 1.27-13.36) and meniscal abnormalities (OR 4.34, 95% CI 1.16-16.32). CONCLUSION/CONCLUSIONS:Frequent knee bending activities were associated with a higher prevalence of knee cartilage lesions (particularly in the patellofemoral compartment) and with an increased risk of progression of cartilage and meniscal lesions in asymptomatic middle-aged subjects.

PURPOSE/OBJECTIVE:To introduce and validate an automated unsupervised multi-parametric method for segmentation of the subcutaneous fat and muscle regions to determine subcutaneous adipose tissue (SAT) and intermuscular adipose tissue (IMAT) areas based on data from a quantitative chemical shift-based water-fat separation approach. MATERIALS AND METHODS/METHODS:Unsupervised standard k-means clustering was used to define sets of similar features (k = 2) within the whole multi-modal image after the water-fat separation. The automated image processing chain was composed of three primary stages: tissue, muscle, and bone region segmentation. The algorithm was applied on calf and thigh datasets to compute SAT and IMAT areas and was compared with a manual segmentation. RESULTS:The IMAT area using the automatic segmentation had excellent agreement with the IMAT area using the manual segmentation for all the cases in the thigh (R(2): 0.96) and for cases with up to moderate IMAT area in the calf (R(2): 0.92). The group with the highest grade of muscle fat infiltration in the calf had the highest error in the inner SAT contour calculation. CONCLUSION/CONCLUSIONS:The proposed multi-parametric segmentation approach combined with quantitative water-fat imaging provides an accurate and reliable method for an automated calculation of the SAT and IMAT areas reducing considerably the total postprocessing time.

OBJECTIVE:To compare magnetic resonance imaging (MRI)-based knee cartilage T2 measurements and focal knee lesions and 36-month changes in these parameters among knees of normal controls and knees of normal weight, overweight, and obese subjects with risk factors for knee osteoarthritis (OA). METHODS:A total of 267 subjects ages 45-55 years from the Osteoarthritis Initiative database were analyzed in this study. Two hundred thirty-one subjects had risk factors for knee OA, but no radiographic OA (Kellgren/Lawrence score ≤1) at baseline. Thirty-six subjects were normal controls. Subjects with OA risk factors were stratified in 3 groups: normal weight (n = 78), overweight (n = 84), and obese (n = 69). All subjects underwent 3T MRI of the right knee at baseline and after 36 months. Focal knee lesions were assessed and cartilage T2 measurements (mean T2 and T2 texture analysis) were performed. RESULTS:The baseline prevalence and severity of meniscal and cartilage lesions were highest in obese subjects and lowest in normal controls (P < 0.05). Obese subjects had the highest mean T2 values and the most heterogeneous cartilage (as assessed by T2 texture analysis), while normal controls had the lowest mean T2 values and the most homogeneous cartilage at baseline (P < 0.05). Increased body mass index (BMI) was significantly (P < 0.05) associated with greater progression of cartilage lesions and constantly elevated cartilage T2 entropy over 36 months. CONCLUSION/CONCLUSIONS:In preclinical OA, increased BMI is associated with more severe cartilage degeneration as assessed by both morphologic and quantitative MRI measurements.