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-enhanced magnetic resonance angiography (MRA) of the thoracic aorta with a standard-dose application. Ninety-three patients with a total of 118 examinations underwent MRA of the thoracic aorta at 1.5 T. There were three injection protocols: in 24 cases, no test bolus was performed and contrast was injected manually; in 14 cases, contrast was injected manually after a test bolus; and in 80 cases, a MR-compatible injector was used after a timing examination. All patients received 20 ml of Gd-DTPA. Quantitative signal-to-noise (SNR) measurements were obtained at different locations in the thoracic aorta, the pulmonary arteries, and the superior vena cava. Two readers in conference retrospectively evaluated each examination with respect to overall image quality and quality of bolus timing. Bolus timing was considered optimal in 70 cases, and either too early or too late in 11 cases. In 37 examinations the bolus was broadened. The SNR measurements of the thoracic aorta revealed that examinations after bolus testing were significantly superior to examinations without a test bolus (p<0.001). Signal intensity ratios of the aorta and the pulmonary trunk were significantly higher in examinations with an optimal contrast timing (p<0.001). Magnetic resonance angiograms of the thoracic aorta with a timing run are significantly superior to non-timed examinations with respect to image quality and SNRs. The administration of 20 ml of Gd-DTPA is sufficient for adult patients. (orig.)