Contrast-enhanced three-dimensional MR angiography of the thoracic aorta: experiences after 118 examinations with a standard dose contrast administration and different injection protocols

The aim of this study was to test three injection protocols for contrast-en hanced magnetic resonance angiography (MRA) of the thoracic aorta with a st andard-dose application. Ninety-three patients with a total of 118 examinat ions underwent MRA of the thoracic aorta at 1.5 T. There were three injecti on protocols: in 24 cases, no test bolus was performed and contrast was inj ected manually; in 14 cases, contrast was injected manually after a test bo lus; and in 80 cases, a MR-compatible injector was used after a timing exam ination. All patients received 20 ml of Gd-DTPA. Quantitative signal-to-noi se (SNR) measurements were obtained at different locations in the thoracic aorta, the pulmonary arteries, and the superior vena cava. Two readers in c onference retrospectively evaluated each examination with respect to overal l image quality and quality of bolus timing. Bolus timing was considered op timal in 70 cases, and either too early or too late in 11 cases. In 37 exam inations the bolus was broadened. The SNR measurements of the thoracic aort a revealed that examinations after bolus testing were significantly superio r to examinations without a test bolus (p < 0.001). Signal intensity ratios of the aorta and the pulmonary trunk were significantly higher in examinat ions with an optimal contrast timing (p < 0.001). Magnetic resonance angiog rams of the thoracic aorta with a timing run are significantly superior to non-timed examinations with respect to image quality and SNRs. The administ ration of 20 ml of Gd-DTPA is sufficient for adult patients.