Predictive value of regional left ventricular circumferential shortening in jeopardized myocardium. A two-dimensional SPAMM cine-MRI study in a canine model.

OBJECTIVE: To determine whether myocardial circumferential shortening assessed in the different myocardial layers by SPAMM cine-MRI may help to discriminate between various degrees of myocardial injury in reperfused myocardium. METHODS: Dogs underwent 90 minutes of coronary occlusion and 24 hours of reperfusion. Using a 1.5 T whole-body MR scanner, SPAMM cine-MRI images were acquired before and 24 hours after surgery on the short axis plan of the left ventricle and analyzed to evaluate the mean myocardial circumferential shortening (% MCS) in the different layers. Based on the residual blood flow, animals were assigned to group I (residual flow < 22.5%) or group II (residual flow > 22.5%). RESULTS: Dogs in group I developed larger infarctions (25.3% +/- 14.6 of the area at risk, n = 5) compared with those in group II (5.81% +/- 1.1, n = 7, P < 0.05). In the jeopardized zone, the % MCS of the subendocardium decreased more significantly in group I (-0.03% +/- 3.7 to 2.2% +/- 5.2) compared with group II (14.7% +/- 1.5 to 18.4% +/- 1.4). CONCLUSIONS: SPAMM cine-MRI is a fast and noninvasive means of measuring % MCS. The MR measurement of this parameter in the subendocardial layer appears quite accurate in describing the degree of damage in reperfused myocardium.

Diagnostic approach to mediastinal masses.

Mediastinal masses represent a vast group of tumours and pseudo-tumours which can involve the various compartments of the mediastinum. The authors propose a radiologic diagnostic approach starting from the plain thoracic radiograph with study of the mediastinal lines and oesophageal transit and going on to the classifications made possible by modern CT and MR imaging. The proposed diagnostic procedure is based on nine mediastinal lines and two 'threads of Ariadne' which are the compartments where the masses are located and their behaviour at CT (densitometry before and after administration of an iodinated bolus) and at MRI (T1, T2, gadolinium-enhanced T1-weighted sequences). The definitive aetiological diagnosis may be established by surgery, but also in certain cases by percutaneous needle biopsy.