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.

Comparison between MRI with spin-echo echo-planar diffusion-weighted sequence (DWI) and histology in the diagnosis of soft-tissue tumours.

PURPOSE: Our aim was to assess the usefulness of magnetic resonance imaging (MRI) with spin-echo echo-planar diffusion-weighted sequences (SE-EPI-DWI) in the study of primary and secondary soft-tissue tumours by correlating the results of imaging and histology. MATERIAL AND METHODS: We retrospectively studied 23 patients (14 men, 9 women; age range 25-87 years) affected by soft-tissue lesions. The MRI study was performed with baseline and contrast-enhanced SE-T1, proton density/T2-weighted (PD/T2), fat-saturated (FATSAT) DP/T2 and single-shot SE-EPI-DWI (b value 50-400- 800s/mm2) sequences. RESULTS: We identified 7/23 benign lesions (three myxoid, four nonmyxoid) and 16/23 malignant tumours (four myxoid, 12 nonmyxoid) with a mean diameter between 21 mm and 20 cm. Qualitative analysis of DWI showed persistence of high signal intensity for increasing b-values in all malignant tumours. Quantitative DWI analysis of the apparent diffusion coefficient (ADC) maps showed a statistical difference between benign and malignant lesions. CONCLUSIONS: In our experience, DWI with qualitative and quantitative analysis correlated well with histology.

Follow-up of collagen meniscus implants by MRI.

PURPOSE: The purpose of our study was to evaluate the usefulness of magnetic resonance imaging (MRI) in the follow-up of patients treated with collagen meniscus implant (CMI) and to identify MRI patterns suitable for defining its evolution. MATERIALS AND METHODS: Between March 2001 and June 2003, CMI was performed on 40 patients (27 men and 13 women, age 23-58 years, median 41 years) affected by irreparable medial meniscal lesions. All patients underwent MRI follow-up at 6 months and 1 year and 16 patients 2 years after the operation; 12 patients underwent second-look arthroscopy with implant biopsy. All MRI examinations were performed with a 1.5-T unit using GE T2*, spin-echo (SE) T1, and FatSat fast spin-echo (FSE) DP and T2-weighted sequences, with different orientations. At 24 months, MR arthrography was also performed. Implant evolution was assessed on the basis of MRI direct and indirect criteria. Direct criteria were morphology and signal intensity of the collagen meniscus/residual meniscus complex. Based on these characteristics, three pattern were identified and classified from 1 to 3, where a higher score corresponded to characteristics approaching those of the normal meniscus. Indirect criteria were chondral surface and subchondral bone marrow oedema at implant site and associated synovial pathology. RESULTS: MRI follow-up at 6 months showed CMI shape and size to be normal (type 3) in 35/40 patients and type 2 in 5/40 patients. CMI signal intensity was type 1 in 32/40 patients and type 2 in 8/40. An interface between prosthetic and native meniscus was identified in 27/40 patients. Chondral lesions were present in 3/40 cases and subchondral bone marrow oedema in 8/40 cases. Reactive synovial effusion was seen in 2/40 patients. MRI follow-up at 12 months showed CMI shape and size to be normal (type 3) in 33/40 patients and type 2 in 7/40. Signal intensity was type 1 in 14/40 patients and type 2 in 26/40 patients. The interface was seen in 19/40 patients. The associated chondral lesions were unchanged, whereas subchondral bone marrow oedema was present in 3/40 patients. No synovial reaction was detected. At 24 months, CMI size was type 3 in 9/16 patients, type 2 in 6/16, and type 1 in one patient in whom the implant could not be identified, as it had been totally resorbed. CMI signal intensity was type 2 in 11/15 and type 3 in 4/16. The interface was identified in seven patients. MR arthrography depicted two additional chondral lesions and enabled correct grading of all lesions. Subchondral bone marrow oedema was present in two patients only. CONCLUSIONS: MRI enables morphological and structural changes of CMI to be monitored over time. Follow-up can be extended beyond 2 years, until the CMI has stabilised and subchondral bone marrow oedema has completely resolved. In the single case with a poor CMI outcome, no related direct or indirect signs were identified.

Contrast enhanced ultrasound with second generation contrast agent for the follow-up of lower-extremity muscle-strain-repairing processes in professional athletes.

PURPOSE: In literature, ultrasonographic potentials in traumatic muscle lesions have been codified, whereas the data about this method utility in follow-up are dissonant. The purpose of this work is to evaluate a second-generation ultrasound (US) contrast agent rule for the professional athletes' distractive lesions. MATERIALS AND METHODS: Twenty professional athletes (18 men and two women, aged between 18 and 34 years) affected by different muscle lesions were examined. All the patients were evaluated within 48 h of the trauma by US device Esaote Technos MPX with a high-frequency linear probe. The examinations were carried out with and without contrast agent after 20, 40 and 60 days after the trauma; second-generation contrast agent was used (SonoVue). RESULTS: In all athletes (nine first-grade lesions, 11 second-grade lesions), by using contrast agent intravenous injection done after 20 days, the appearance of contrast spots affecting part or all the lesioned area were observed. During the follow-up, after 40 days. the contrast spots widened to include the entire scar area, with haemorrhagic residual in three cases. After 60 days, in no case was a liquid haemorrhagic collection still present, and we found an important reduction of extension of vascular spots and US intensity and their total disappearance in seven cases. CONCLUSIONS: US with a second-generation contrast agent, thanks to the neoangiogenesis identification, allows recognition, individuation and monitoring the repair processes in the muscle lesion and allows estimation of when athletes can return to competitive activity. This fact obviously reduces both relapses and complications.