Radiation Dose Depends on Where Patient Has CT Angiography Procedures: Presented at ACC

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Title: Radiation Dose Depends on Where Patient Has CT Angiography Procedures: Presented at ACC
URL: http://www.pslgroup.com/dg/21F1B2.htm
Doctor's Guide
April 4, 2008

By Ed Susman

CHICAGO -- April 4, 2008 -- A study of angiography centres found there is a wide-ranging difference among institutions in the dose of ionising radiation that each patient receives during a cardiac computed tomography (CT) angiography scan.

"The exposure to ionising radiation associated with cardiac CT angiography has raised serious concerns," said Jörg Hausleiter, MD, Associate Professor of Medicine, German Heart Centre, Munich, Germany.

"The development and evaluation of additional dose-saving algorithms are needed for the widespread use of this promising cardiac CT methodology," he said.

In this study, Dr. Hausleiter said the mean dose of radiation used overall was 17 mSv, but the range was from 9 to 44 mSv.

In an oral presentation here at the 57th Annual Meeting of the American College of Cardiology (ACC 2008), Dr. Hausleiter reported the findings from the Prospective Multicenter Study on Radiation Dose Estimates of Cardiac CT Angiography in Daily Practice (PROTECTION I), a prospective, international, industry-independent, multicentre study that investigated the dose estimates and the efficacy of dose-saving algorithms in daily practice.

The researchers received reports from 44 institutions that provided imaging data and information on scanning protocols of all consecutive cardiac CT angiographies performed during 1 month. The analysis Dr. Hausleiter reported included 1,729 cardiac CT angiographies compiled through December 2007.

For all scans, dose estimates and efficacy of dose-saving algorithms, qualitative and quantitative data on image quality, as well as future potentials for dose reduction were determined by a central core lab. Radiation dose was estimated from the dose length product multiplied by a conversion coefficient.

"In this study, we found that the main indication for cardiac CT angiography was the assessment of coronary arteries," Dr. Hausleiter said. About 84% of the scans were undertaken to determine the condition of those arteries.

The mean scan length was 144 mm with a CT dose index (DI_vol) of 65.9 mGy. However, the range of that mean was plus or minus 69.3 mGy. The mean estimated radiation dose was 17.1 mSv, but again, that parameter was plus or minus 9.5 mSv.

Radiation dose estimates differed significantly between study sites, with the range of mean doses from 8.5 to 43.8 mSv and different types of 64-slice systems (P < .0001) The mean minimum dose was about 11.8 mSv; the mean maximum dose was 25.2 mSv for different systems.

"ECG-correlated tube current modulation was used in 82% of cardiac CT angiographies and on average resulted in a significant 21% reduction of dose estimates," Dr. Hausleiter said.

As compared with 120 kV, the use of 100 kV tube current resulted in a significant 51% reduction in dose estimates, and as compared with spiral data acquisition, the use of sequential scan algorithms resulted in a significant 67% reduction in dose estimates, but both were used infrequently (6% and 2% of all cardiac CT angiographies, respectively).

"Although cardiac CT is a very promising technology, educational efforts, and further technical developments are needed to keep the radiation exposure as low as reasonably achievable," said Dr. Hausleiter.

"This study will increase the awareness of the radiation exposure of cardiac CTs. In addition, we think that this study will result in an increased use of already available dose-saving algorithms, which will lower the radiation exposure of patients substantially. Finally, this study strengthens the need for further education of cardiologists and radiologists about CT technology to ensure low radiation exposure to the patient," he said.

[Presentation title: International Prospective Multicenter Study on Radiation Dose Estimates of Cardiac CT Angiography in Daily Practice. Abstract 409-6]

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