Critical shoulder angle: what do radiologists need to know?

The critical shoulder angle (CSA) constitutes a straightforward and highly reproducible tool. Degenerative rotator cuff tears (RCT) are associated with a significantly larger CSA. In this review, the most relevant features of the CSA are summarized: (1) the relationship between the CSA and RCT pathophysiology, (2) accurate measurement of the CSA according to various imaging modalities, (3) the contribution of the CSA in predicting the occurrence of RCT, and (4) RCT recurrence after surgical repair.

Electromagnetic navigation system combined with High-Frequency-Jet-Ventilation for CT-guided hepatic ablation of small US-Undetectable and difficult to access lesions.

Objectives: To report the feasibility and efficacy of percutaneous ablation of small hepatic malignant tumors that are invisible on ultrasound and inaccessible using in-plane CT guidance, using a combination of high-frequency jet-ventilation (HFJV) and electromagnetic (EM) needle tracking. Methods: This study reviewed 27 percutaneous ablations of small hepatic tumors (<2 cm) performed using EM navigation-based probe placement and HFJV. All lesions were invisible on ultrasound and difficult to reach on CT requiring a double-oblique approach. The primary outcome was technical efficacy, defined as complete lesion coverage, and evaluated on contrast enhanced MRI after 3 and 6 months. Needle placement accuracy, the number of control CT acquisitions, procedure time, complications and radiation doses were assessed. Results: Twenty-one patients with 27 treated lesions (14 hepatocellular carcinomas and 13 metastases) were included in this study. Mean tumor size was 12 ± 5.7 mm. Thirty-three percent of the lesions were located on the hepatic dome. Complete ablation was obtained in 100% at the 3- and 6-month MRI follow-up. The ablation probe was correctly placed on the first pass in 96%, with a mean path-to-tumor angle of 7 ± 4 degrees and a mean tip-to-tumor distance of 22 ± 19mm. A readjustment for additional overlapping application resulted in complete treatment in 4 patients. Needle placement took a mean 23 ± 12 min with mean radiation doses of 558 mGy*cm. No major complications were reported. Conclusion: Percutaneous liver ablation of lesions that cannot be seen on US and requiring out-of-plane CT access can be successfully and safely treated using electromagnetic-based navigation and jet-ventilation.

Hepatocellular carcinoma abutting large vessels: comparison of four percutaneous ablation systems.

PURPOSE: To compare overall local tumour progression (OLTP), defined as the failure of primary ablation or local tumour progression, with single applicator monopolar radiofrequency ablation (RFA), microwave ablation (MWA), cluster-RFA and multi-bipolar radiofrequency (mbpRFA) in the treatment of hepatocellular carcinoma (HCC) ≤ 5 cm abutting large vessels (≥3 mm). MATERIALS AND METHODS: This multicenter, retrospective, per-nodule study was performed from 2007 to 2015. The study was approved by the ethics review board, and informed consent was waived. A total of 160/914 HCC nodules treated by thermal ablation and abutting large vessels (40 per treatment group) treated by monopolar RFA, MWA, cluster-RFA or mbpRFA were matched for tumour size, alpha-feto-protein level and vessel size. OLTP rates were compared by the log-rank test and the multivariate Cox model after matching. RESULTS: No differences were observed in tumour size, vessel size or alpha-feto-protein levels among the three groups (p = 1). The cumulative 4-year OLTP rates following monopolar RFA, cluster-RFA, multi-bipolar RFA and MWA were 50.5%, 16.3%, 16.3% and 44.2%, respectively (p = 0.036). On multivariate Cox regression, vessel size ≥10 mm, monopolar RFA and MWA were independent risk factors of OLTP compared to cluster-RFA or mbpRFA. CONCLUSION: Multi-applicator RFA provides better local tumour control in HCC abutting large vessels than single-applicator techniques (monopolar RFA or MWA).