Superior protocol found for CT angiography of the neck

At 64-detector row spiral CT, the low-tube-voltage/high-tube-current with low-dose contrast medium protocol was found to be superior to the conventional protocol for CT angiography of the neck regarding radiation dose, venous streak artifacts, and image quality, according to a study published in the April issue of Clinical Radiology.

As concerns about radiation dose in medical imaging heighten, utilizing low tube voltage has shown to reduce dose without detrimentally influencing image quality. Low tube voltage also has the ability to eradicate contrast medium when conducting CT angiography of the neck. This technology is often problematic, as venous streak artifacts also pose a technical issue. However, lead author Wei Xia, of the Subei People's Hospital of Jiangsu Province in Yangzhou, China, and colleagues investigated the effect of a protocol using a low volume of contrast medium and a low-tube voltage/high-tube-current product technique on radiation dose and image quality of neck CT angiography using a 64-detctor row spiral CT.

The researchers performed both a phantom and clinical study to investigate their aim. During the phantom study, a 64-detector row spiral CT was used at multiple tube voltage and current settings. The best contrast medium-to-noise ratio was found by acquiring and processing iodine contrast medium attenuation curves.

The prospective clinical study was then performed by gathering 84 patients who required CT angiography of the neck and dividing them into two even groups. The first group (group A) was examined with the conventional imaging protocol, and the second group (group B) was examined at 80 kV and 600 mAs along with a 50 percent reduction in contrast medium dose.

After statistical analysis, results revealed that the CT dose index-volume decreased in group B by 54 percent in comparison with group A. The contrast medium-to-noise ratio, however, increased by 50 percent in group B when compared with group A. Caused by venous streak artifacts, the mean attenuation was significantly lower in group B than group A. The qualitative analysis revealed that all criteria were significantly better for group B than for group A.

“The present study revealed that the radiation dose could be significantly reduced by using a tube voltage of 80 kV for neck CTA,” wrote Xia and colleagues. “When conducting CTA of the neck using 64-detector row spiral CT, a tube voltage of 80 kV, a current of 600 mAs, a contrast medium concentration of 175 mg iodine/kg body weight, and 50 ml saline flush are recommended,” they concluded.