August 30th, 2013

Will New Scanner Technology Reduce Radiation from CT Angiography?

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CardioExchange’s John Ryan interviews Kavitha Chinnaiyan and Gilbert L. Raff about their study group’s nonrandomized investigation of using new scanner technology to reduce radiation from coronary CT angiography in the context of an ongoing quality-improvement program. The study is published in Circulation: Cardiovascular Imaging.


Investigators prospectively followed 11,901 patients at 15 Michigan centers participating in the Advanced Cardiovascular Imaging Consortium (ACIC). CT angiography (CTA) radiation doses and image quality were compared between a baseline control period and two follow-up periods, both of which involved continuous education, feedback, and mandatory participation in the initiative. The median radiation dose remained unchanged from the control period to the first follow-up period, suggesting that ongoing application of a best-practice algorithm simply sustained previously achieved dose targets. Newer scanning technology was introduced during the first follow-up period, and a significant 31% incremental reduction in the radiation dose was documented during the second follow-up period. The percentage of diagnostic quality scans did not change significantly between the two follow-up periods.


Ryan: You studied how radiation-reduction strategies are lowering the radiation dose received by patients undergoing coronary CTA. Can you provide some information about the intervention?

Chinnaiyan and Raff: This study was a follow-up to a previously published analysis of data from 15 sites participating in ACIC, a statewide quality initiative sponsored by Blue Cross Blue Shield Blue Care Network of Michigan. In that study, the implementation of a best-practice algorithm for performing coronary CTA resulted in 53% reduction in radiation dose.

In the present study, we found that continued implementation of the best-practice algorithm via a monitoring-feedback loop allowed the lower dose to be sustained; adoption of newer scanner technology was then associated with incremental reduction of the dose by 31%. The educational interventions (best-practice algorithm) included adequate pre-scan heart-rate control, decreased scan length, EKG-dose modulation (when applicable), and most important, lower tube voltage in appropriate patients. In the second study, the educational intervention included implementation of new scanner technology that had become available or had improved since the first study. Newer scanner technologies associated with incremental dose reductions were prospective gating, high-pitch helical or single-heartbeat volumetric scanning, and adaptive statistical iterative reconstruction (ASIR).

Ryan: It is often difficult to attribute improvements to a particular program in an observational study because many things are changing simultaneously when the program is implemented. How confident are you that the intervention caused the improvement?

Chinnaiyan and Raff: We agree that this is a limitation of a study such as ours. Multiple extraneous factors could have influenced the results, but throughout the study period, we had real-time observation of a temporal relation between the median radiation dose at each site and the status of the educational program at that site. Monitoring of doses occurred on a quarterly basis; when a site was found to have higher median doses, this was reported back with assistance to uncover and correct specific practices.

Ryan: Can you characterize the magnitude of the improvement?

Chinnaiyan and Raff: Although coronary CTA is an excellent noninvasive tool with growing data on diagnostic and prognostic utility, exposure to ionizing radiation is a significant limitation of this technology. The enthusiasm for the potential cost savings and convenience of coronary CTA has been tempered by significant concerns about the doses of radiation received by patients. At ACIC’s inception, the median radiation dose across the 15 sites was 21 mSv. At the end of the present study, the median dose was 4.9 mSv. Thus, within 4 years, there was a 77% dose reduction through education and adoption of new scanner technology. This study — performed in a collaborative setting of a network of physicians, allied healthcare personnel, and third-party payers — shows that thoughtful interventions can significantly improve the safety profile of diagnostic imaging.

Ryan: Much of the improvement is due to new scanner technology. Should patients be asking about the scanner — and how should they interpret the result?

Chinnaiyan and Raff: It is important for patients to be aware of their cumulative radiation doses from all diagnostic procedures. To this end, inquiring about the average dose would provide them with information about the expected dose from a coronary CTA scan. However, multiple individual factors contribute to a patient’s dose exposure, such as heart rate, body-mass index, arrhythmias during the scan, inability to receive heart rate–lowering medications, and so on. Thus, even if the average radiation dose at a given center is comparatively low, it does not guarantee that every patient’s exposure to radiation will be low. In addition, discussing the merits of a particular scanner may not be feasible when a hospital or center uses several different scanners for coronary CTA. Ideally, providing accurate dose information to patients would require a collaborative approach whereby referring physicians, appointment centers, patient-preparation personnel, CT technologists, and reading physicians are well versed in the expected dose nuances of a given scanner.


What are your thoughts about the promise for newer scanning technology to reduce radiation doses from diagnostic scans? Does this study influence your opinion?

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