Non-enhanced MR angiography of renal arteries: comparison with contrast-enhanced MR angiography.

BACKGROUND: The main causes of renal artery stenosis (RAS) are atherosclerosis and fibromuscular dysplasia. Despite contrast-enhanced magnetic resonance angiography (CE-MRA) being a safe and reliable method for diagnosis of RAS especially in young individuals, recently it has been possible to adopt innovative technologies that do not require paramagnetic contrast agents. PURPOSE: To assess the accuracy of steady-state free-precession (SSFP) non-contrast-enhanced magnetic resonance angiography (NC-MRA) by using a 1.5 T MR scanner for the detection of renal artery stenosis, in comparison with breath-hold CE-MRA as the reference standard. MATERIAL AND METHODS: Sixty-three patients (33 men, 30 women) with suspected renovascular hypertension (RVHT) were examined by a 1.5T MR scanner; NC-MRA with an electrocardiography (ECG)-gated SSFP sequence was performed in 58.7% (37/63) of patients; in 41.3% (26/63) of patients a respiratory trigger was used in addition to cardiac gating. CE-MRA, with a three-dimensional gradient echo (3D-GRE) T1-weighted sequence, was performed in all patients within the same session. Maximum intensity projection (MIP) image quality, number of renal arteries, and the presence of stenosis were assessed by two observers (independently for NC-MRA and together for CE-MRA). The agreement between NC-MRA and CE-MRA as well as the inter-observer reproducibility were calculated with Bland-Altman plots. RESULTS: MIP image quality was considered better for NC-MRA. NC-MRA identified 143 of 144 (99.3%) arteries detected by CE-MRA (an accessory artery was not identified). Fourteen stenoses were detected by CE-MRA (11 atherosclerotic, 3 dysplastic) with four of 14 (28.5%) significant stenosis. Bland-Altman plot demonstrated an excellent concordance between NC-MRA and CE-MRA; particularly, the reader A evaluated correctly all investigated arteries, while over-estimation of two stenoses occurred for reader B. Regarding NC-MRA, inter-observer agreement was excellent. CONCLUSION: NC-MRA is a valid alternative to CE-MRA for the assessment of renal arteries.

Complications of microwave and radiofrequency lung ablation: personal experience and review of the literature.

PURPOSE: Complications correlated with percutaneous radiofrequency ablation (RFA) and microwave ablation (MWA) of lung tumours were retrospectively reviewed to compare them with data from the literature and to assess risk factors related with the procedures. MATERIALS AND METHODS: From January 2003 to January 2009, 29 patients (36 lung lesions) were treated with RFA; from January 2007 to January 2009, 16 patients (17 lung lesions) were treated with MWA. Complications recorded at our institution are reported following the Society of Interventional Radiology guidelines. A systematic review of the literature was performed. RESULTS: Any major complication of RFA or MWA was recorded. In agreement with the literature, pneumothorax was the most frequent complication, even though the incidence in our series was lower than reported in the literature (3.5% vs. 4.3-18%). Other complications of RFA were pleural effusion and subcutaneous emphysema. No massive haemorrhages, haemoptysis, abscesses, pneumonia, infections or tumour seeding were recorded in our series. The most common complication of MWA was pneumothorax (25% vs. 39% reported in the literature). Pleural effusion was a common reaction, but therapeutic drainage was never required. CONCLUSIONS: Pneumothorax is the most common complication of both techniques. RFA and MWA are both excellent choices in terms of safety and tolerance.