Scanner model matters when evaluating reconstruction, dose reduction technique

If iterative reconstruction techniques are to help reduce CT radiation dose while improving visualization, imagers must take into account not only the reconstruction technique they choose but also the scanner model they use.

That’s the key conclusion of a study lead-authored by Kristin Jensen, MSc, of the Institute of Physics at the University of Oslo in Norway and published online Dec. 15 in Current Problems in Diagnostic Radiology.

Jensen and colleagues set out to evaluate the feasibility of dose reduction and improved conspicuity of, specifically, lesions in a liver phantom for different iterative reconstruction algorithms.

They scanned an anthropomorphic upper abdomen phantom, specially designed for receiver operating characteristic analysis, with two different CT models from GE—the CT750 HD and the Lightspeed VCT.

The researchers obtained images at dose levels of 5, 10 and 15 mGy, then reconstructed with filtered back projection (FBP) and two different iterative reconstruction algorithms.

Using the CT750 HD, they improved lesion conspicuity with iterative reconstruction at the 10 mGy dose level compared with FBP at the 15 mGy dose level.

A similar dose reduction with maintained conspicuity proved undoable for the Lightspeed VCT.

The authors noted that the difference owed to the imaging systems’ respective detectors, as the CT 750 HD uses GE’s Gemstone detector while the Lightspeed VCT uses the HiLight detector.

In their study discussion, Jensen et al. write that their results “indicate that it is possible to reduce the radiation dose by 33 percent with the same or better lesion conspicuity for this lower dose level with the combination of the Gemstone detector and iterative reconstruction techniques (CT750 HD).”

They further note that dose reductions used in combination with iterative image reconstruction “should be thoroughly tested beforehand.”