Tag Archives: radiation dose

Studies Offer Hope for Future CT Protocol Comparisons

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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.

New Research Further Dispels Fear of Over Diagnosis in CT Screening

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According to a new study based on the International Early Lung Cancer Action Program (I-ELCAP), lung cancers identified in low-dose CT screening programs are similar to those identified by non- screening means. The research results, which were released on March 27 in Radiology, further alleviate concerns that cancers detected through low- dose CT screening are less aggressive than those found through other means, and therefore demand less attention and resources.  In fact, the frequency of small-cell carcinoma and adenocarcinoma were similar for cancers detected through screening programs and outside the screening setting.

This study is another brick in the wall of evidence building for the value of low radiation dose CT lung cancer screening in high risk asymptomatic smokers. Regardless of whether nodules are solid or “ground glass” (non-solid), growth occurs that is similar in the screened populations and in those detected of having lung cancer due to symptoms.

While it is true we do not yet have a data-based analysis of costs versus quality life years saved, the evidence that screening is worthwhile continues to become stronger. “The CT scanners we have now are really phenomenal,” with resolution that continues to improve as the radiation dose falls, “so that the amount of information you can get out of them for emphysema, for coronary artery risks, and so on, continues to increase,” says Dr. Claudia Henschke, lead author of this study.

She goes on to point out that cancers detected via low dose CT screening “are real cancers that would kill you if they weren’t discovered early, so it kind of underscores again the data that we had shown in ELCAP and that NLST (National Lung Screening Trial) has shown — that screening for lung cancer saves lives.” And that is the key takeaway.