Patient doses from X-ray computed tomography examinations by a single-array detector unit: Axial versus spiral mode

Background: X-ray computed tomography (CT) examinations deliver a significant amount of radiation doses to patients comparing to conventional radiography examinations. The objective of the current study was to analyze and investigate the average patient received dose from axial and spiral CT exams in a medical imaging center. Material and Methods: In this study, the patient imaging technique, weight and height were recorded. The patients’ doses provided by CT unit in terms of CTDIw were also recorded. Then, other dosimetric quantities including dose-length product (DLP) and effective dose were calculated for each patient using the recorded data. The average values were obtained for all the studied dosimetric quantities. Also, their distribution in terms of examined regions and imaging mode ie, axial and spiral CT were analyzed by SPSS software. Results: For all patients, the mean effective dose of 4.4 mGy with the standard deviation of 9.2 was found. The CTDIw for axial group was two times higher than spiral ones. Conversely, the effective dose of axial group was less than spiral group. Additionally, the effective doses of 2.3 and 5.2 mSv were found for axial and spiral, receptively. For both quantities of CTDIw and effective dose, the observed difference between axial and spiral modes were significant (P<0.001). Conclusion: Our results showed that although the patient doses in the current study was comparable with the reported values by similar studies in other countries, it was higher than the reported values of a similar study in Iran. Exposure technique’s optimaization and further review in routine CT examinations were recommended. Iran. J. Radiat. Res., 2012 10(2): 89‐94