Nevertheless, using the lowest possible dose is desirable, which has been a point of controversy raised by the U.S. Centers for Medicare and Medicaid Services in denying reimbursement for screening CTC in the Medicare population.
The study, to be presented by Philips Healthcare's Sunny Virmani, incorporated CTC studies from a database of asymptomatic and symptomatic individuals scanned on a 256-slice CT scanner (Brilliance iCT, Philips Healthcare, Andover, MA). Images were acquired at 120 kV, pitch 0.66, slice thickness 1.25 mm, and 0.75-mm increments, while the effective mAs varied from 15 mAs (n = 25) and 30 mAs (n = 30) -- lower than levels typically used in clinical practice.
The data were processed and interpreted using a 3D workstation by one radiologist. Effective dose (mSv) for each case and also each orientation individually was calculated as the product of dose-length product (DLP) values and the standard weighting factors (k) for CTC studies. Overall, a mean effective dose of 2.02 mSv per patient was recorded.
"Using a Philips Brilliance iCT scanner at the two of the low-dose settings currently available has produced quality 2D and 3D images in our CTC studies with a significant reduction in patient dose," Virmani's co-investigator Dr. Abraham Dachman told AuntMinnie.com. "Using lower doses may help reduce patient concerns and the concerns of various organizations about CTC. Additionally, there is also an active discussion regarding whether a possible decrease in hypoattenuating lesion conspicuity in the solid organs will benefit patients by reducing unnecessary workup of unimportant extracolonic findings."
As a next step, use of even lower mAs will be evaluated in combination with denoising filters to evaluate the feasibility of ultralow-dose CTC.
