Table of Contents
What are the two most commonly used units used for measuring CT doses ?
- CTDI volume = CTDI weighted / pitch (measured in mGy units) represents a dose through a slice of a phantom that is independent of the total scan length
- Dose Length Product = CTDI volume x scan length in cm (measured in mGy.cm units) represents the overall radiation exposure of the CT scan by factoring in the length of the scan.
Additional Information:
- CTDI vol and DLP do not represent the actual absorbed or effective dose to the patient. They are only used as an index of radiation output by the system for comparison purposes (such as to calculate the National Diagnostic Reference Levels (DRLs))
- Size-specific dose estimate (SSDE) is a method to convert CTDI volume and DLP into a patient’s absorbed dose. The radiation exposures are the same for all scans, however, it is the scanned patient’s size that determines the patient-specific absorbed dose. SSDE requires the anterior-posterior and lateral dimensions of the patient.
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