gms | German Medical Science

48th Meeting of the Particle Therapy Co-Operative Group

Particle Therapy Co-Operative Group (PTCOG)

28.09. - 03.10.2009, Heidelberg

Risk Assessment of Ionizing Radiation in Cardiac Imaging: Estimated Radiation Dose

Meeting Abstract

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  • F. Torrens - Institut Universitari de Ciencia Molecular, Valencia, Spain
  • G. Castellano - Instituto Universitario de Medio Ambiente y Ciencias Marinas, Valencia, Spain

PTCOG 48. Meeting of the Particle Therapy Co-Operative Group. Heidelberg, 28.09.-03.10.2009. Düsseldorf: German Medical Science GMS Publishing House; 2009. Doc09ptcog206

DOI: 10.3205/09ptcog206, URN: urn:nbn:de:0183-09ptcog2065

Published: September 24, 2009

© 2009 Torrens et al.
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Outline

Text

Background: Cardiac computed tomography (CT) angiography (CCTA) emerges as a useful diagnostic imaging modality in the assessment of coronary artery disease. However the potential risks because of exposure to ionizing radiation associated with CCTA raise concerns. The objectives are to estimate the radiation dose of CCTA in routine clinical practice and the association of currently available strategies with dose reduction, and to identify the independent factors contributing to radiation dose.

Material and methods: It is carried out a cross-sectional, international, multicentre, observational study (50 study sites: 21 university and 29 community hospitals) of estimated radiation dose in 1965 patients undergoing CCTA between February and December 2007. Linear regression analysis is used to identify independent predictors associated with dose.

Results: The main outcome measure is the dose-length product (DLP) of CCTA. The median DLP of 1965 CCTA examinations performed at 50 study sites was 885mGy·cm (interquartile range, 568–1259mGy·cm), which corresponds to an estimated radiation dose of 12mSv (or 1.2 ¥ the dose of an abdominal CT study or 600 chest X-rays). A high variability in DLP is observed between study sites (range of median DLPs per site, 331–2146mGy·cm). Independent factors associated with radiation dose are patient weight [relative effect on DLP, 5%; 95% confidence interval (CI), 4–6%], absence of stable sinus rhythm (10%; 95% CI, 2–19%), scan length (5%; 95% CI, 4–6%), electrocardiographically controlled tube current modulation [–25%; 95% CI, -23–(-28)%; applied in 73% of patients], 100kV tube voltage [–46%; 95% CI, -42–(-51)%; applied in 5% of patients], sequential scanning [–78%; 95% CI, -77–(-79)%; applied in 6% of patients], experience in cardiac CT (–1%; 95% CI, -1–0%), number of CCTAs per month (0%; 95% CI, 0–1%) and type of 64-slice CT system (for highest vs. lowest dose system, 97%; 95% CI, 88–106%). Algorithms for dose reduction are not associated with deteriorated diagnostic image quality in this observational study.

Conclusion: Median doses of CCTA differ significantly between study sites and CT systems. Effective strategies to reduce radiation dose are available but some strategies are not frequently used. The comparable diagnostic image quality may support an increased use of dose-saving strategies in adequately selected patients. Recommendations: (1) Medical imaging is the largest controllable source of radiation exposure. (2) Routine surveillance radionucleotide stress tests or cardiac CTs in asymptomatic patients at low risk for ischemic heart disease are not recommended. (3) Once it has been established that a cardiac imaging study that uses ionising radiation is needed, effort should be made to reduce patient dose. (4) Longitudinal tracking of individual cumulative lifetime dose for patients is not practical. (5) Imaging experts–manufacturers should continue working on developing consistent radiation output metrics.