Objective: The objective of our study was to compare the effect of a caudocranial scan direction versus a craniocaudal scan direction on arterial enhancement and perivenous artifacts in 16-MDCT angiography of the supraaortic arteries.
Subjects and methods: Eighty consecutive patients (51 men; mean age, 62 years; age range, 28-89 years) underwent scanning in the caudocranial direction (group 1; n = 40) or the craniocaudal direction (group 2; n = 40). All patients received 80 mL of contrast material followed by a 40-mL saline chaser bolus, both administered IV at 4 mL/sec. Bolus tracking was used. Attenuation inside the arterial lumen was measured at intervals of 1 sec throughout the data set. Attenuation in the superior vena cava (SVC) was measured. Contrast material-related perivenous artifacts were graded on a scale of 0-3 (none to extensive).
Results: Attenuation in the ascending aorta, carotid bifurcation, and intracranial arteries was slightly lower in group 2 versus group 1 (231 +/- 64 H, 348 +/- 52 H, and 258 +/- 48 H vs 282 +/- 43 H, 381 +/- 73 H, and 291 +/- 77 H, respectively; p < 0.05). Maximum and mean arterial attenuations were slightly lower in group 2 versus group 1 (369 +/- 58 H and 303 +/- 48 H vs 401 +/- 71 H and 334 +/- 58 H; p < 0.05). Attenuation in the SVC was much lower in group 2 versus group 1 (169 +/- 39 H vs 783 +/- 330 H; p < 0.001). Mean streak artifact score was much lower in group 2 versus group 1 (1.3 +/- 0.9 vs 2.5 +/- 0.6; p < 0.001).
Conclusion: Use of a craniocaudal scan direction results in slightly lower attenuation of the carotid artery and much lower attenuation of the SVC. Streak artifacts are significantly reduced. This technique allows better evaluation of the ascending aorta and supraaortic arteries.