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Comparison of two methods for assessing patient dose from computed tomography
J Geleijns1, J G Van Unnik, J Zoetelief
1Department of Clinical Oncology, University Hospital Leiden, The Netherlands.
The British Journal of Radiology
|April 1, 1994
Summary
This study measured patient radiation doses during computed tomography (CT) scans. Results show effective doses vary by examination type, with thorax and abdomen scans yielding higher values than head scans.
Area of Science:
- Medical Physics
- Radiological Protection
Background:
- Computed tomography (CT) examinations are associated with significant patient radiation exposure.
- Accurate assessment of organ and effective doses is crucial for radiological protection.
Purpose of the Study:
- To determine organ doses and calculate effective doses for routine CT examinations using two distinct methodologies.
- To compare the determined effective doses with existing literature values.
Main Methods:
- Organ doses were measured using thermoluminescence dosemeters (TLDs) in an anthropomorphic Rando Alderson phantom.
- Organ doses were also calculated from the computed tomography dose index (CTDI) and published conversion factors.
- Effective doses were computed for CT head, thorax, and abdomen examinations.
Main Results:
- Effective doses for CT head scans were 1-2 mSv using both methods.
- For CT thorax and abdomen scans, the Rando phantom yielded 18 and 24 mSv, respectively.
- CTDI-based calculations resulted in lower effective doses for thorax (11-15 mSv) and abdomen (15-20 mSv) compared to the Rando phantom.
Conclusions:
- Effective dose values obtained in this study, particularly for thorax and abdomen CT, were higher than those reported by other investigators.
- Discrepancies may stem from variations in CT protocols and phantoms used.
- Calculating organ doses from CTDI and conversion factors is a more practical method for future dose intercomparisons, despite potentially underestimating effective dose by up to 40%.