Impact of low-kVp scan technique on oral contrast density at abdominopelvic CT

Abstract

Oral contrast density is strongly influenced by kVp, supporting use of more dilute oral contrast when using lower-kVp techniques.

Low-keV and Low-kVp CT for Positive Oral Contrast Media in Patients with Cancer: A Randomized Clinical Trial

“…Recently, in a phantom setup, Patino et al (17) confirmed 28%-200% higher attenuation on low-kVp/low-keV images obtained with OCM solutions of different concentrations, and Sheafor et al (18) reproduced these results on low-kVp images. These investigators suggested the use of OCM solutions of 6 mg I/mL to maintain the desirable attenuation values achieved using a standard OCM concentration at 120 kVp (18). Our clinical trial confirms the outcome of the published phantom experiments, and, despite a 25% reduction in ICM concentration, higher bowel attenuation was achieved with 100 kVp and 50-65 keV images compared with BCM/120 kVp images, with preference.…”

“…The attenuation of diluted water-soluble OCMs like iohexol increases during enteral transit as water is absorbed from the intestine, rendering higher CT attenuation distally (13,18). Compared with the standard dose, rICM exhibited a lesser difference in attenuation between distal and proximal segments compared with sICM at 100 kVp.…”

“…Similarly, for rICM, each cup contained 6 mL iohexol (total, 18 mL iohexol; 5.4 g of iodine; 6 mg I/mL). A 25%-reduced concentration was chosen as suggested by results of prior phantom studies (17,18). No flavoring agent was added to the ICM.…”

“…may necessitate alterations of standard window widths and levels (17)(18)(19). Reduction of the concentration of positive OCM at low-kVp and low-keV CT has not been clinically validated, despite the similar attenuation profiles of the two commonly used OCM bases, iodine and barium.…”

Low-Voltage Abdominal CT: Is It Time to Reduce the Dose of Oral Contrast Medium?

“…With the advent of new CT scanners and imaging protocols, including a low-peak-kilovoltage technique with an iterative reconstruction algorithm and monochromatic low kiloelectron volts as in dual-energy/spectral CT imaging, the dose of the oral contrast medium can potentially be reduced (3,4). This is exactly the same as for intravenously injected iodinated contrast media: When tube voltage is reduced, the attenuation of iodine is increased by two-to fourfold, and thus the contrast medium dose can be consequently reduced (5).…”