Inverse-direction scanning improves the image quality of whole carotid CT angiography with 64-MDCT

The purpose of this prospective study was to clarify whether reducing the incidence of perivenous artifacts through craniocaudal scanning improves the quality of 64-multidetecter computed tomography (MDCT) angiography images of the whole carotid artery.

Forty patients underwent MDCT angiography in the caudocranial (n=20) or craniocaudal (n=20) direction in 2007. All patients were injected with 75 ml of contrast media followed by a 35-ml saline chaser bolus at 4.0 ml/s in the right antecubital vein. Maximum intensity projection (MIP) images were scored according to image quality on a scale of 1-5. Bilateral arterial and venous attenuation was measured on 10 separated slices. We compared the mean image quality score of the two groups (i.e. those scanned caudocranially and those scanned craniocaudally). We analyzed the correlation between vascular attenuation and mean image quality.

Compared with the caudocranial group, the craniocaudal group had higher image quality scores (median, 3.70 vs. 3.40; 95% CI, 3.50-3.96 vs. 3.06-3.60; p<0.05), higher arterial attenuation (median, 550 HU vs. 489 HU; range, 270-686 vs. 302-574; p<0.05), and lower maximum venous attenuation (median, 436 vs. 1452 HU; range, 250-617 vs. 377-2044; p<0.01). Multiple regression analysis revealed that the most significant correlation factor with image quality was minimum arterial attenuation (R2=0.42, p<0.001) measured near the brachiocephalic artery. In the caudocranial group only, there was a negative correlation between right brachiocephalic venous attenuation and minimum arterial attenuation.

Compared with conventional caudocranial scanning, craniocaudal scanning improves the image quality of 64-MDCT angiography images of the whole carotid artery.