High-frequency Quantitative Ultrasound Imaging of Human Rotator Cuff Muscles: Assessment of Repeatability and Reproducibility.

This study evaluated the repeatability and reproducibility of using high-frequency quantitative ultrasound (QUS) measurement of backscatter coefficient (BSC), grayscale analysis, and gray-level co-occurrence matrix (GLCM) textural analysis, to characterize human rotator cuff muscles. The effects of varying scanner settings across two different operators and two US systems were investigated in a healthy volunteer with normal rotator cuff muscles and a patient with chronic massive rotator cuff injury and substantial muscle degeneration. The results suggest that BSC is a promising method for assessing rotator cuff muscles in both control and pathological subjects, even when operators were free to adjust system settings (depth, level of focus, and time-gain compensation). Measurements were repeatable and reproducible across the different operators and ultrasound imaging platforms. In contrast, grayscale and GLCM analyses were found to be less reliable in this setting, with significant measurement variability. Overall, the repeatability and reproducibility measurements of BSC indicate its potential as a diagnostic tool for rotator cuff muscle evaluation.

Skeletal Muscle Assessment Using Quantitative Ultrasound: A Narrative Review.

Ultrasound (US) is an important imaging tool for skeletal muscle analysis. The advantages of US include point-of-care access, real-time imaging, cost-effectiveness, and absence of ionizing radiation. However, US can be highly dependent on the operator and/or US system, and a portion of the potentially useful information carried by raw sonographic data is discarded in image formation for routine qualitative US. Quantitative ultrasound (QUS) methods provide analysis of the raw or post-processed data, revealing additional information about normal tissue structure and disease status. There are four QUS categories that can be used on muscle and are important to review. First, quantitative data derived from B-mode images can help determine the macrostructural anatomy and microstructural morphology of muscle tissues. Second, US elastography can provide information about muscle elasticity or stiffness through strain elastography or shear wave elastography (SWE). Strain elastography measures the induced tissue strain caused either by internal or external compression by tracking tissue displacement with detectable speckle in B-mode images of the examined tissue. SWE measures the speed of induced shear waves traveling through the tissue to estimate the tissue elasticity. These shear waves may be produced using external mechanical vibrations or internal "push pulse" ultrasound stimuli. Third, raw radiofrequency signal analyses provide estimates of fundamental tissue parameters, such as the speed of sound, attenuation coefficient, and backscatter coefficient, which correspond to information about muscle tissue microstructure and composition. Lastly, envelope statistical analyses apply various probability distributions to estimate the number density of scatterers and quantify coherent to incoherent signals, thus providing information about microstructural properties of muscle tissue. This review will examine these QUS techniques, published results on QUS evaluation of skeletal muscles, and the strengths and limitations of QUS in skeletal muscle analysis.

Magnetic resonance imaging of the shoulder.

The aim of this article is to review the use of magnetic resonance imaging (MRI) for the evaluation of shoulder pain, which is a common clinical complaint of the musculoskeletal system. MRI is an essential auxiliary tool to evaluate these patients because of its high resolution and high sensitivity in depicting the soft tissues. This article will review the imaging technique, normal imaging anatomy, and most common imaging findings of disorders of tendons, labrum, and ligaments of the shoulder. It will also discuss common systemic diseases that manifest in the shoulder as well as disorders of the acromioclavicular joint and bursae. New advances and research in MRI have provided additional potential uses for evaluating shoulder derangements.

Magnetic resonance imaging of the elbow.

Elbow pain can cause disability, especially in athletes, and is a common clinical complaint for both the general practitioner and the orthopaedic surgeon. Magnetic resonance imaging (MRI) is an excellent tool for the evaluation of joint pathology due to its high sensitivity as a result of high contrast resolution for soft tissues. This article aims to describe the normal imaging anatomy and biomechanics of the elbow, the most commonly used MRI protocols and techniques, and common MRI findings related to tendinopathy, ligamentous and osteochondral injuries, and instability of the elbow.

Three-Dimensional Zero Echo Time Magnetic Resonance Imaging Versus 3-Dimensional Computed Tomography for Glenoid Bone Assessment.

PURPOSE: To evaluate the 3-dimensional (3D) zero echo time (ZTE) magnetic resonance imaging (MRI) technique and compare it with 3D computed tomography (CT) for the assessment of the glenoid bone. METHODS: ZTE MRI using multiple resolutions and multislice CT were performed in 6 shoulder specimens before and after creation of glenoid defects and in 10 glenohumeral instability patients. Two musculoskeletal radiologists independently generated 3D volume-rendered images of the glenoid en face. Post-processing times and glenoid widths were measured. Inter-modality and inter-rater agreement was assessed. RESULTS: Intraclass correlation coefficients (ICCs) for inter-modality assessment showed almost perfect agreement for both readers, ranging from 0.949 to 0.991 for the ex vivo study and from 0.955 to 0.987 for the in vivo patients. Excellent interobserver agreement was found for both the ex vivo (ICCs ≥ 0.98) and in vivo (ICCs ≥ 0.92) studies. For the ex vivo study, Bland-Altman analyses for CT versus MRI showed a mean difference of 0.6 to 1 mm at 1.0-mm3 MRI resolution, 0.3 to 0.6 mm at 0.8-mm3 MRI resolution, and 0.3 to 0.6 mm at 0.6-mm3 MRI resolution for both readers. For the in vivo study, Bland-Altman analyses for CT versus MRI showed a mean difference of 0.6 to 0.8 mm at 1.0-mm3 MRI resolution, 0.5 to 0.6 mm at 0.8-mm3 MRI resolution, and 0.4 to 0.8 mm at 0.7-mm3 MRI resolution for both readers. Mean post-processing times to generate 3D images of the glenoid ranged from 32 to 46 seconds for CT and from 33 to 64 seconds for ZTE MRI. CONCLUSIONS: Three-dimensional ZTE MRI can potentially be considered as a technique to determine glenoid width and can be readily incorporated into the clinical workflow. LEVEL OF EVIDENCE: Level II, development of diagnostic criteria (consecutive patients with consistently applied reference standard and blinding).

Rotator Cuff Tendon Assessment in Symptomatic and Control Groups Using Quantitative MRI.

BACKGROUND: Relatively weak correlations between patient symptoms and rotator cuff tendon (RCT) tearing have been reported; however, the relationship between symptoms and tendinosis has been less well-studied. PURPOSE/HYPOTHESIS: To use quantitative MRI to assess the bilateral RCTs in shoulders of both patients with unilateral symptomatic tendinopathy and control subjects. We hypothesized that quantitative MRI measures would differ between symptomatic patients and controls. STUDY TYPE: Prospective imaging study. POPULATION/SUBJECTS: In all, 48 shoulders from 24 subjects (mean age, 32.8 years), including 14 patients with unilateral symptomatic tendinopathy and 10 asymptomatic controls. FIELD STRENGTH/SEQUENCE: 3T/3D ultrashort echo time Cones sequence with magnetization transfer preparation (UTE-Cones-MT) and Carr-Purcell-Meiboom-Gill. ASSESSMENT: Macromolecular fraction (MMF) and T2 relaxation were measured in four regions of the superior RCT, including all-segments, and lateral-third, bursal-sided, and articular-sided segments. The Western Ontario Rotator Cuff (WORC) index and visual analog scale were assessed. STATISTICAL TESTS: Three shoulder groups were evaluated, including symptomatic shoulders, contralateral asymptomatic shoulders in patients, and asymptomatic controls. MMF and T2 values were compared between groups using a bootstrap-based comparison of means. RESULTS: Significant differences were found in both MMF and T2 values between symptomatic and control RCTs when analyzing all-segments (P = 0.027 and P = 0.006, respectively) and articular-sided segments (both P = 0.001). Significant differences between asymptomatic RCTs in patients and control RCTs were also found, including MMF in all four anatomic regions analyzed (P = 0.024-0.044), as well as T2 in all-segments (P = 0.003), bursal-sided segments (P = 0.021), and articular-sided segments (P = 0.002). No significant differences in MMF (P = 0.420-0.950) or T2 (P = 0.380-0.910) were seen between ipsilateral symptomatic and contralateral asymptomatic RCTs in patients. DATA CONCLUSION: Symptomatic RCTs showed significantly lower MMF values and higher T2 values compared with control RCTs. In patients with unilateral symptomatic tendinopathy, the contralateral shoulder can demonstrate asymptomatic tendinopathy, which can be quantified using MMF or T2 . EVIDENCE LEVEL: 2 TECHNICAL EFFICACY: Stage 2. J. Magn. Reson. Imaging 2020;52:864-872.

Intraligamentous synovial chondromatosis of the anterior cruciate ligament.

Synovial chondromatosis is a rare disease that causes disability and dysfunction of the involved synovial joint. We describe the second case in the literature of intraligamentous synovial chondromatosis involving the anterior cruciate ligament, confirmed by pathology after arthroscopic removal of the chondral bodies. We also describe associated magnetic resonance imaging findings which may be helpful for diagnosis of this very rare entity.

Age-related decrease in collagen proton fraction in tibial tendons estimated by magnetization transfer modeling of ultrashort echo time magnetic resonance imaging (UTE-MRI).

Clinical magnetic resonance imaging (MRI) sequences are not often capable of directly visualizing tendons. Ultrashort echo time (UTE) MRI can acquire high signal from tendons thus enabling quantitative assessments. Magnetization transfer (MT) modeling combined with UTE-MRI-UTE-MT-modeling-can indirectly assess macromolecular protons in the tendon. This study aimed to determine if UTE-MT-modeling is a quantitative technique sensitive to the age-related changes of tendons. The legs of 26 young healthy (29 ± 6 years old) and 22 elderly (75 ± 8 years old) female subjects were imaged using UTE sequences on a 3T MRI scanner. Institutional review board approval was obtained, and all recruited subjects provided written informed consent. T1 and UTE-MT-modeling were performed on anterior tibialis tendons (ATT) and posterior tibialis tendons (PTT) as two representative human leg tendons. A series of MT pulse saturation powers (500-1500°) and frequency offsets (2-50 kHz) were used to measure the macromolecular fraction (MMF) and macromolecular T2 (T2MM). All measurements were repeated by three independent readers for a reproducibility study. MMF demonstrated significantly lower values on average in the elderly cohort compared with the younger cohort for both ATT (decreased by 16.8%, p = 0.03) and PTT (decreased by 23.0%, p < 0.01). T2MM and T1 did not show a significant nor a consistent difference between the young and elderly cohorts. For all MRI parameters, intraclass correlation coefficient (ICC) was higher than 0.98, indicating excellent consistency between measurements performed by independent readers. MMF serving as a surrogate measure for collagen content, showed a significant decrease in elderly leg tendons. This study highlighted UTE-MRI-MT techniques as a useful quantitative method to assess the impact of aging on human tendons.

Quantification of Retinal Nonperfusion Associated With Posterior Segment Neovascularization in Diabetic Retinopathy Using Ultra-Widefield Fluorescein Angiography.

BACKGROUND AND OBJECTIVE: To quantify the size and location of nonperfusion associated with posterior segment neovascularization (NV) in proliferative diabetic retinopathy (PDR) using ultra-widefield fluorescein angiography. PATIENTS AND METHODS: Cross-sectional study of 18 eyes with PDR. The total image area, areas of nonperfusion, buds of posterior segment neovascularization (either neovascularization of the disc or elsewhere), and the distances from each bud to the nearest area of nonperfusion and to the disc were measured. RESULTS: Nonperfused areas with associated neovascularization were significantly larger than areas without neovascularization (32.0% ± 5.24% of the retinal image vs. 3.3% ± 0.92%; P < .001) and were more likely to be posteriorly located. Nonperfusion encompassing greater than 23% of the total angiographic image had more associated neovascular buds (9.64 ± 2.16 vs. 0.86 ± 0.29; P < .0001), which were closer to the disc (7.53 mm ± 0.27 mm vs. 9.24 mm ± 0.64 mm; P = .014). CONCLUSION: A threshold size of nonperfusion greater than 23% of the retinal image is associated with posterior segment neovascularization and may serve as an indicator of risk for the development of PDR. [Ophthalmic Surg Lasers Imaging Retina. 2019;50:86-92.].