Quantification of shoulder muscle intramuscular fatty infiltration on T1-weighted MRI: a viable alternative to the Goutallier classification system.

BACKGROUND: Quantification of rotator cuff intramuscular fatty infiltration is important for clinical decision-making in patients with rotator cuff tear. The semi-quantitative Goutallier classification system is the most commonly used method, but has limited reliability. Therefore, we sought to test a freely available fuzzy C-means segmentation software program for reliability of the quantification of shoulder intramuscular fatty infiltration on T1-weighted MR images and for correlation with fat fraction by six-point Dixon MRI. MATERIALS AND METHODS: We performed a prospective cross-sectional study to measure visible intramuscular fat area percentage on oblique sagittal T1 MR images by fuzzy C-means segmentation and fat fraction maps by six-point Dixon MRI for 42 shoulder muscles. Intra- and inter-observer reliability were determined. Correlative analysis for fuzzy C-means and six-point Dixon intramuscular fatty infiltration measures was also performed. RESULTS: We found that inter-observer reliability for the quantification of visible intramuscular fat area percentage by fuzzy C-means segmentation and fat fraction by six-point Dixon MRI was 0.947 and 0.951 respectively. The intra-observer reliability for the quantification of visible intramuscular fat area percentage by fuzzy C-means segmentation and fat fraction by six-point Dixon MRI was 0.871 and 0.979 respectively. We found a strong correlation between fuzzy C-means segmentation and six-point Dixon techniques; r = 0.850, p < 0.001 by individual muscle; and r = 0.977, p < 0.002 by study subject. CONCLUSION: Quantification of intramuscular fatty infiltration by fuzzy C-means segmentation on T1-weighted sequences demonstrates excellent reliability and strong correlation with fat fraction by six-point Dixon MRI. Quantitative fuzzy C-means segmentation is a viable alternative to the semi-quantitative Goutallier classification system.

Virtual Journal Club Beyond the Pandemic: An Enduring and Fluid Educational Forum.

OBJECTIVE: Since its inception, journal club has been a cornerstone to the life-long process of medical education. The virtual journal club (VJC), initiated as a robust solution to many educational challenges encountered during COVID-19 pandemic-related distance learning, provides an enduring and fluid forum for multilevel teaching and learning. MATERIALS AND METHODS: In this manuscript we share our institutions' reasoning and methods to implement a VJC for multi-level learners. A standardized format applicable to all VJC sessions was adopted to ensure reproducibility from presenter to presenter. Sessions were held via video conference platforms. Pedagogy regularly emphasized in undergraduate medical education was adopted. Informal assessment of each session's strengths and areas for improvement was performed. RESULTS: A total of 30 sessions were held prior to manuscript submission, including discussion of 36 refereed journal articles from March 26, 2020, to April 20, 2021. The virtual journal club was very well received by all participants. The medical students and residents found the information current and engaging. The fellows stated that the journal club strengthened their knowledge base and enhanced communication and teaching skills. The attendings learned from its encouraged frank discussion of differing practice patterns. The format of these sessions offers an ideal setting to teach medical students and residents how to evaluate and employ evidence-based medicine and meets multiple LCME and ACGME requirements. CONCLUSIONS: This VJC forum allows for development of essential nonclinical skills including lifelong active learning and analysis, peer collaboration, and technology adaptation and usage.

Chronic hindlimb ischemia impairs functional vasodilation and vascular reactivity in mouse feed arteries.

Vasodilation of lower leg arterioles is impaired in animal models of chronic peripheral ischemia. In addition to arterioles, feed arteries are a critical component of the vascular resistance network, accounting for as much as 50% of the pressure drop across the arterial circulation. Despite the critical importance of feed arteries in blood flow control, the impact of ischemia on feed artery vascular reactivity is unknown. At 14 days following unilateral resection of the femoral-saphenous artery-vein pair, functional vasodilation of the profunda femoris artery was severely impaired, 11 ± 9 versus 152 ± 22%. Although endothelial and smooth muscle-dependent vasodilation were both impaired in ischemic arteries compared to control arteries (Ach: 40 ± 14 versus 81 ± 11%, SNP: 43 ± 12 versus and 85 ± 11%), the responses to acetylcholine and sodium nitroprusside were similar, implicating impaired smooth muscle-dependent vasodilation. Conversely, vasoconstriction responses to norepinephrine were not different between ischemic and control arteries, -68 ± 3 versus -66 ± 3%, indicating that smooth muscle cells were functional following the ischemic insult. Finally, maximal dilation responses to acetylcholine, ex vivo, were significantly impaired in the ischemic artery compared to control, 71 ± 9 versus 97 ± 2%, despite a similar generation of myogenic tone to the same intravascular pressure (80 mmHg). These data indicate that ischemia impairs feed artery vasodilation by impairing the responsiveness of the vascular wall to vasodilating stimuli. Future studies to examine the mechanistic basis for the impact of ischemia on vascular reactivity or treatment strategies to improve vascular reactivity following ischemia could provide the foundation for an alternative therapeutic paradigm for peripheral arterial occlusive disease.