Purpose: To evaluate the influences of Gd-DTPA on 3D time-of-flight (TOF) MR angiography (MRA). Material and Methods: In an experimental study using a flow phantom, contrast 3D TOF MRA was performed at varying Gd-DTPA concentrations, flow rates, TRs and flip angles. In a clinical study, cranial 3D TOF MR angiograms using Gd-DTPA were obtained in 38 patients to evaluate the efficacy of Gd-DTPA in enhancing the diagnosis of intracranial vascular lesions. Visualization of the venous system and distal arterial branches on contrast MRA was compared with those of noncontrast MRA. Results: In the experimental study, progressive signal loss of inflowing spins due to saturation was smaller with higher concentration of Gd-DTPA. The influences of Gd-DTPA on the saturation effect were more pronounced with a slower flow rate, shorter TR and larger flip angles. In the clinical study, i.v. administration of Gd-DTPA improved the visualization of the venous system and distal arterial branches on 3D TOF MRA. The diagnostic value of MRA was enhanced by Gd-DTPA in patients with intracranial vascular lesions such as vascular malformations and large aneurysms. Conclusion: The T1-shortening effect of Gd-DTPA reduced the signal loss of vessels with slow flow rate, and contrast MRA was particularly useful for evaluation of venous abnormalities. Compared with conventional MRA, shorter TRs and larger flip angles were considered beneficial in contrast MRA.
MR angiography and dynamic flow evaluation of the portal venous system
