UW CT Effective Dose and Risk Estimator

IMPORTANT STATEMENT ON CONTEXT OF RISK ESTIMATES

Instructions:
1. To estimate dose and risk from a CT procedure: enter the scan dose length product (DLP), scan region, patient age, and gender then press "Estimate Dose and Risk." Or, press DLP label to select CT procedure from list.
2. To estimate risk from a known whole-body effective dose: enter the patient age, effective dose, and gender then press "Estimate Risk." Or, press effective dose label to select diagnostic procedure from list.
3. To receive dose estimates in context of Pearce at al, "Radiation exposure from CT scans in childhood and subsequent risk of leukaemia and brain tumours: a retrospective cohort study." Lancet 2012.
Select scan regions with * in title (Head*, Chest*, ...), use pediatric patient age (0-22 yrs old), and refer to popup summary

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Scope of Educational Tool

This is an educational tool for radiologists and technologists, providing broad estimates of radiation dose and risk to empower imaging professionals with information consistent with recent published reports on radiation dose and risk. The reported values should be considered as broad estimates because they are based on approximate dosimetry estimates and the current, limited understanding of risk from ionizing radiation. Due to these approximations and uncertainty, the estimates are presented with subjective uncertainty of ± 100% for dose estimates and ± 300% for risk estimates. In addition, this tool does not offer:

  1. Discussion of how to reduce dose from CT procedures. Interested readers are directed to other resources to learn about dose reduction in CT imaging [5, 6].
  2. Patient specific dose or risk estimates. Thorough dosimetry evaluation for a specific patient should be performed under consultation of a qualified medical physicist.
  3. Discussion of the benefits of CT. It is beyond the scope of this tool to properly present the important benefits of CT imaging. This work presents conservative estimates of cancer risk, which are potentially higher than true values. Even with conservative estimates, the benefit of appropriate use of diagnostic procedures generally far outweigh potential risks.

Please refer to our article for a detailed description of this tool:
Adam M. Alessio and Grace S. Phillips, "A pediatric CT dose and risk estimator," Pediatric Radiology, Published online 11 July 2010.

[1] The DLP (mGy cm) to whole body effective dose (mSv) conversion factors were derived from the interpolation of factors for simulations of average Adult, 10, 5,1,0 year old models. These whole body effective dose estimates are only approximate for an "average" sized patient and should not be viewed as accurate for a specific patient. Current CT scanners report DLP as measured in 16cm or 32cm diameter acrylic phantoms; This tool assumes a factor of 2 change between the 16cm and 32cm conversion factors.

Shrimpton PC, Hillier MC, Lewis MA, Dunn M (2005) Doses from computed tomography examinations in the UK - 2003 review. NRPB - W67, NRPB Publications.

The American Association of Physicists in Medicine (AAPM) Report 96. Measurement,Reporting,and Management of Radiation Dose in CT. College Park, MD: AAPM, 2008.

Huda W, Ogden KM, Khorasani MR. Converting dose-length product to effective dose at CT. Radiology. 2008; 248: 995-1003.

[2] Lifetime attributable risk of cancer mortality and incidence from all forms of cancer in the USA from the Surveillance Epidemiology and End Results (SEER) , National Cancer Institute (http://seer.cancer.gov/).

Surveillance, Epidemiology, and End Results (SEER) Program (www.seer.cancer.gov) DevCan database: "SEER 17 Incidence and Mortality, 2000-2006, with Kaposi Sarcoma and Mesothelioma". National Cancer Institute, DCCPS, Surveillance Research Program, Cancer Statistics Branch, released April 2009, based on the November 2008 submission. Underlying mortality data provided by NCHS (www.cdc.gov/nchs). Lifetime risk statistics available here.

[3] The estimates of cancer risk are derived from interpolation of factors reported in the BEIR VII report. These estimates are very rough based on the numerous assumptions in the BEIR VII Report, including the linear no-threshold model. For a thorough discussion of the limitation of these factors, please review the original doument:

Health Risks from Exposure to Low Levels of Ionizing Radiation: BEIR VII – Phase 2. BEIR VII, National Research Council of the National Academies, 2006. http://www.nap.edu/catalog/11340.html

[4] Mettler FAJ, Huda W, Yoshizumi TT, Mahesh M. Effective doses in radiology and diagnostic nuclear medicine: a catalog. Radiology. 2008; 248: 254-263.

[5] McCollough CH, Bruesewitz MR, Kofler JMJ. CT dose reduction and dose management tools: overview of available options. Radiographics. 2006;26:503-512.

[6] McNitt-Gray MF. AAPM/RSNA Physics Tutorial for Residents: Topics in CT. Radiation dose in CT. Radiographics. 2002;22:1541-1553.

UW Dose Risk Tool, © Adam Alessio, University of Washington, 2008