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A Preliminary Method Correlating Patient-Specific Parameters with Direct Measurements to Estimate Organ Doses in CT


L Sinclair

L Sinclair1*, A Mench1, T Griglock2, B Cormack1, S Bidari1, M Arreola1, (1) University of Florida, Gainesville, FL, (2) Oregon Health & Science Univ, Portland, OR,

MO-D-134-6 Monday 2:00PM - 3:50PM Room: 134

Purpose: In the field of Computed Tomography (CT) dosimetry, there remains a need to accurately measure organ doses. Such measurements are only meaningful if they are performed under actual clinical scanning conditions, for this purpose, a cadaver can serve as the measurement subject that most closely mimics a living patient. Organ doses were measured in 7 adult female cadaveric subjects with varying body mass indices (BMIs) and for various CT protocols.
Methods:A tube placement system allowed external access to internal organs, in which optically-stimulated luminescent dosimeters (OSLDs) were placed and used to measure dose. Dosimeter placement and location was based on organ size and distribution. In order to determine organ doses of real patients, a correlation between various patient size parameters and the measured organ doses was explored. Only measurements that could be performed on a CT image or subject-specific parameters or data which could otherwise be obtained for an actual patient were considered for this correlation. The size parameters that were examined included: body mass index (BMI), the AP and lateral dimensions of the patient, and patient perimeter.
Results:The BMIs for the 7 subjects ranged from 16.6-43.9, spanning from underweight to extreme obesity. Overall average organ doses from a CAP exam for all subjects ranged from 11.8-24.4 mGy. Generally, organ doses were shown to increase with all size parameters examined.
Conclusion:For the purpose of accuracy, the estimation of patient dose in CT must be based on actual physical measurements. A complete set of direct organ dose measurements for 7 adult female cadavers has been accomplished for common CT exams with this research. It has been shown before that patient size parameters can be indicative of patient dose. This work has shown further validation of this concept.

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