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Radiation Exposure Risk Statements

Learn about radiation exposure risk statement requirements for research protocols involving human subjects and how to use the UC San Diego Radiation Risk Statement Calculator to generate the statement.


Principal investigators (PIs) submitting research protocols to the Human Subjects Institutional Review Board that expose human subjects to ionizing radiation must:

  • Include an explanation of the risks of radiation exposure
  • Inform study participants of the degree of risk involved

These are requirements of UC San Diego's Human Research Protections Program (HRPP) and Human Exposure Review Committee (HERC).

Prepare and review

Before calculating radiation risk, review the following information:

  • All radiation exposure is dealt with cumulatively.
  • When calculating exposure, no distinction is made between routine studies and studies done specifically for the research protocol.
  • Research protocols requiring exposure to radiation from imaging studies considered standard of care, including those that would be done even if the participant were not taking part in a research protocol, must be accounted for, and exposure estimates and risks must be explained.

Calculate your project's radiation risk

Use the UC San Diego Radiation Risk Statement Calculator to generate a risk statement and risk category for your project. By appropriately cutting and pasting the risk statement into the correct sections of your research plan, radiation exposure risk requirements can be met.

Follow the steps below.

Enter data into the calculator.

  1. Go to My Research Safety.
  2. Click the Radiation Risk Statement Calculator tab.
  3. Follow instructions to enter your data. The calculator guides you through the process of accounting for the studies in your protocol.
    • Account for:
      • Only the first 12 months in your calculations and explanations of risk if a study runs longer than 12 months or for multiple years
      • Exposure to radiation from imaging studies considered standard of care, including those that would be done even if the participant were not taking part in a research protocol
  4. Click Create Statement and the calculator will generate:
    • Total exposure for the mix of studies entered
    • A risk statement explaining that exposure

Important: A generic risk statement is generated which you may or may not need to modify to clarify the situation being described. In order to assist with this process, certain parts will be emphasized in bold text to draw your attention to where your personal input will be necessary. The generic risk statement should not be directly cut and pasted into your research plan without appropriate adjustments being made.

Use the calculator's risk statement on your application forms.

When submitting a project application, explanations of radiation exposure must appear in 2 places. Copy and paste appropriate portions of the risk statement generated by the calculator into the correct sections as follows:

  1. UC San Diego Human Research Protections Program (HRPP) New Biological Application Research Plan - Place risk information in Section 14 - Risks of Participation. If using an older form, this may be Section 13 - Potential Risks.

    • Include a summation of the examinations to be used, noting the exposure in millisieverts (mSv) that is calculated.

    • Note: If there is the possibility of other required studies based on clinical situations that arise, summarize and include an explanation of why they may be needed.

    • For complicated protocols with many imaging studies, it is useful to display this information in a spreadsheet. (See the example below.)

    • Submit documentation with your dose calculations describing how you derived your numbers.

      • Note: Best practice is to submit documentation from the UC San Diego Radiation Risk Statement Calculator. If Radiation Risk Statement Calculator documentation is not used, please identify the source of your numbers.

  2. Insert the Consent to Act as a Research Subject - The University of California, San Diego Consent to Act as a Research Subject is where you insert the consent statement generated by the Radiation Risk Statement Calculator. This is a concise statement showing only the total exposure with the proper supporting explanations. This section should not be as detailed as #1 above.

Example of spreadsheet format:

This study involves radiation exposure from diagnostic procedures that are according to standard of care and for research purposes.

The scans planned at screening are necessary per usual course of diagnostic workup and follow up per standard of care.

The intervention tested in this study does not involve additional radiation exposure.

IV contrast may be used with MRI or CT, unless contraindicated. If contrast is contraindicated, a non-contrast scan will be performed.

Note: CT scans of affected lymph node chain will only be performed if lymphadenopathy is detected by palpation.

The principal radiation exposures according to standard of care
The principal radiation exposures that are according to standard of care are:
 •  Chest x-ray at screening: 0.4 mSv
 •  CT Scan (Chest/Abdomen/Pelvis) IF done at screening: 13.0 mSv
The principal radiation exposures that are according to research purposes in this study are:
 •  Chest x-ray at follow up: 0.4 mSv
 •  CT Scan (Chest/Abdomen/Pelvis) IF done at the following points:
      • Cycle 2 / Day 1: 13.0 mSv
      • Cycle 4 / Day 1: 13.0 mSv
      • Cycle 6 / Day 1: 13.0 mSv
      • Follow up: 13.0 mSv

The best-case scenario would be:

Chest x-ray at screening: 0.4 mSv

NO CT Scans

This would total 0.4 mSv

The worst-case scenario would be:

Chest x-ray at screening and at follow up: 0.8 mSv

CT Scans at all points for a total of 4 CT Scans: 65 mSv

This would total: 65.8 mSv

For unique situations, write your own explanation.

Deriving an explanation of exposure and risk is not always easy. For example, a protocol may call for an imaging study based on the clinical judgment of the investigator or attending physician, so the study may or may not be performed.

For unique situations:

  • Write your own explanation of the risks of radiation exposure.
  • Read examples that demonstrate how to handle 3 situations other researchers have encountered, ranging from an uncomplicated protocol to a more complex situation.
  • Follow the guidelines below:
    • Keep it simple, using wording and comparisons customary at UC San Diego.
    • Reference all exposure statements to typical yearly background radiation in San Diego, which is given as 1.6 mSv.
      • Do not make statements comparing the amount of radiation to some percentage of background or a number of cross-country plane flights.
    • Calculate your radiation exposure estimates for both "typical" and "worst-case" scenarios when computing exposure from studies to be performed where the actual number of studies is not definite.
Questions? Contact EH&S Radiation Safety, (858) 822-2494.

Acknowledgment: The Radiation Risk Statement Calculator was made possible by the generous contribution of Robert E. Reiman, MSPH MD, Assistant Clinical Professor (Radiology) Faculty, Medical Physics Graduate Program, Radiation Safety Division, Duke University Medical Center.

This information and the UC San Diego Radiation Risk Statement Calculator are intended exclusively for UC San Diego employees and affiliates.