[Value and problems of magnetic resonance imaging in the diagnosis of aortic dissection].

Nuclear magnetic resonance imaging was performed for 14 patients with aortic dissection using a 0.15 T resistive magnetic imaging system (Toshiba MRT-15A). The diagnosis was confirmed by X-ray computed tomography. The scan time was 15 minutes, and five or 10 slices were obtained simultaneously. The imaging was made using spin echo method (repetition time: TR = 200-800 msec, and echo delay time: TE = 40 msec). The natural contrast between flowing blood and stationary material permits the clear demonstration of the intimal flap of aortic dissection. The intimal flap was demonstrated in seven cases as a curvilinear high intensity band within the dilated aorta in consecutive sections. The rapidly flowing blood in the narrow true lumen produced little or no signal, while eddy currents within the false lumen usually produced signals. The thrombi in the false lumen had high intensity. In seven cases, the false lumen was completely filled with thrombi and the intimal flap could not be observed on nuclear magnetic resonance images.