A recent study featured in the Journal of Computer Assisted Tomography touches on the perennial issue for radiology researchers studying and evaluating the effectiveness of different low-dose protocols. The topic brings the need for accurate CT dose reporting to the forefront, as researchers use different techniques to compare dose levels without relying on unnecessary CT scans in the same patient.
At the Mayo Clinic, researchers have used iterative reconstruction to acquire half-dose virtual colonoscopy exams to compare with full-dose exams. Previously, radiological researchers have relied on phantom studies to approximate dose differences among different protocols, or on patient division, in which patient groups (that are similar but never match precisely) undergo different scan protocols to approximate dose differences.
The issue, however, is that radiation dose and image quality must be compared in every patient, not just groups, because discrepancies in patient shape, cardiac output, lesion pathology, and other factors are highly individualized. The study continues, “matched-cohort research studies can’t evaluate the impact of noise reduction on reader performance for identifying findings, and even back-to-back full- and half-dose studies cannot control for the effect of phase enhancement on lesion conspicuity.”
Both of these points are valid. But, there is hope in the form of positive scientific studies on the way. Research from the University of Washington will soon be published in the American Journal of Roentgenology involving patients with cirrhosis and hypervascular liver tumors. This research offers valuable information for the future of low-dose CT reconstructed with multiple techniques from the same data set when comparing lesion detection.
Additionally, research involving the challenge of scanning the same patient twice with two different dose levels is ongoing. The Institutional Research Board has approved this study at a number of institutions, which analyzes patients who are scanned with ASIR and then full-iterative techniques. Stay tuned for full data available next year.
While these challenges do indeed exist, these ongoing studies offer hope for the effectiveness of low-dose protocols and understanding which protocols work most effectively.