64-slice CT cuts radiation dose in pediatric cases

November 1, 2005

Increased concern about radiation exposure from routine CT scans has prompted vendors to incorporate dose-lowering strategies into the latest generation of scanners. Those dose savings have been quantified in pediatric patients, according to several groups of researchers presenting work at the RSNA meeting. They found that use of the automatic exposure control (AEC) tool results in a considerable dose reduction without compromising image quality.

Dr. Kristen Thomas and colleagues from the Mayo Clinic in Minnesota retrospectively compared image quality and radiation dose between a 64-slice and an electron-beam CT scanner, and between the 64-slice and four-, eight-, and 16-slice CT scanners. The 64-slice scanner proved consistently superior to the EBCT in terms of better spatial resolution, fewer motion artifacts, and higher image quality in pediatric chest and abdominal/pelvic exams. The team found no significant differences in image quality between 64-slice CT and the other CTs in abdominal/pelvic exams.

Regarding dose, EBCT and the other CT scanners delivered 75% higher dose on the abdominal/pelvic exams and 111% and 43% higher for chest exams, respectively, compared with 64-slice CT.

Besides better image quality and dose reduction, 64-slice CT scanners offer an improved prescan workflow because of the AEC technique, according to Dr. Holger Greess and colleagues from the University of Erlangen in Germany.

Using the AEC on a 64-slice scanner in 60 pediatric chest and abdominal exams, researchers found it was no longer necessary to query patients about weight, length, and age or to measure distances in the scout view or provide weight-adapted scan protocols. This saved considerable time, Greess said, and it reduced the average radiation dose by 20% to 60% compared with standard protocols used on 16-slice machines.

A retrospective analysis of 30 consecutive cardiovascular 64-slice CT scans in children by Dr. Giancarlo Savino and colleagues at the Medical University of South Carolina in Charleston showed significant dose reduction with the use of AEC. The average CT dose index and dose length product with AEC was 2.64 mGy and 76.52 mGy, respectively, compared with 6.10 mGy and 169.06 mGy, respectively, if AEC had not been used.