Volume rendering compared with maximum intensity projection for magnetic resonance angiography measurements of the abdominal aorta

Purpose: To compare the volume rendering technique (VRT) with maximum intensity projection (MIP) for aortic diameter measurements in MR angiography (MRA) data sets. Material and Methods: Existing contrast-enhanced 3-dimensional MRA and digital subtraction angiography (DSA) data sets from 20 patients were analyzed. In each MRA data set, two aortic diameters were measured using MIP and VRT. Agreement with DSA measurements, dependence on rendering parameters, and interobserver agreement were assessed. Results: Diameters measured on MIP with fixed parameters showed no significant difference compared with DSA and with freely selected parameters a slight overestimation relative to DSA. Diameters measured on VRT were larger than on DSA. For both MIP and VRT, the measurements depended on the chosen parameters. The error relative to DSA was larger for VRT than for MIP with fixed parameters but not with freely chosen parameters. Interobserver agreement did not differ significantly. Conclusions: VRT is not suitable for diameter measurements of the abdominal aorta with fixed parameter settings but may be useful with User-selected settings