Ravi K. Kaza MD, Presenter: Speaker, General Electric Company

Mahmoud Mouhamad Al-Hawary MD, Abstract Co-Author: Research funded, General Electric Company

Joel Franklin Platt MD, Abstract Co-Author: Nothing to Disclose

To evaluate the image quality and diagnostic adequacy of CT Enterography (CTE) done at 80 kVp in comparison to CTE done at 120 kVp and to assess dose reduction achieved with 80 kVp CTE.

23 cases of 80 kVp CTE and 25 controls of 120 kVp CTE were reviewed by two experienced abdominal radiologists in a blinded fashion. Patients weighing less than 160 lbs were selected for 80 kVp CTE and controls were matched for weight and body mass index (BMI). On a scale of 1 to 5 (1=poor, 2=acceptable, 3=good, 4=very good, 5=excellent), the examinations were scored for adequacy of evaluation of bowel wall, mesenteric vessels, hepatic parenchyma and for overall image quality. Examinations with score of 1 & 2 were considered not adequate and examinations with score of 3 to 5 were considered adequate for diagnostic interpretation. The window width and level used to evaluate bowel was recorded. The effective radiation dose was calculated by multiplying the dose length product generated by the scanner with a conversion factor of 0.015.

All 80 kVp CTE examinations were overall scored as being adequate for interpretation by both readers. Except for one case where evaluation of liver was graded as 2 by one reader, none of the other image categories in 80 kVp CTE examinations were given a score of < 3 by either reader. The combined mean score of both readers for 120 kVp and 80 kVp CTE were as follows: Bowel wall 3.92, 3.48; Mesenteric vessels 3.76, 3.98; Liver 3.74, 3.17; overall image quality 3.88, 3.5 respectively. For 80 kVp CTE, there was a statistically significant decrease in the scores for evaluation of bowel wall, liver and overall image quality and a statistically significant increase in score for evaluation of mesenteric vessels. The average of window width and level used for bowel interpretation were statistically different at 580/117 for 120 kVp CTE and 770/218 for 80 kVp CTE. The mean effective radiation dose was 15.51 mSv for 120 kVp CTE and 4.84 mSv for 80 kVp CTE.

In patients weighing under160 lbs, 80 kVp CTE is an alternative to 120 kVp CTE with mild decrease in image quality and has diagnostically acceptable image quality. This protocol change results in a significant dose reduction of 69 %.

In patients with average or lower BMI substantial radiation dose reduction can be realized for CTE by utilizing an 80 kVp scan protocol while still maintaining diagnostic adequacy.

Kaza, R, Al-Hawary, M, Platt, J, CT Enterography at 80 kVp: Assessment of Diagnostic Adequacy, Image Quality, and Dose Reduction.  Radiological Society of North America 2010 Scientific Assembly and Annual Meeting, November 28 - December 3, 2010 ,Chicago IL. http://archive.rsna.org/2010/9004895.html