Estimation of Organ and Effective Doses in CT Examinations Performed Using Automatic Exposure Control and Fixed Tube Current Techniques: A Phantom Case Study.

Document Type: Original Paper

Authors

1 Department of Medical Physics, University of Ghana, Accra, Ghana

2 Radiation Protection Institute, Ghana Atomic Energy Commission and Department of Medical Physics, University of Ghana.

3 Radio logical and Medical Sciences Research Institute, Ghana Atomic Energy Commission and Department of Medical Physics.

4 Department of Medical Physics Graduate School of Nuclear and Allied Sciences, University of Ghana.

Abstract

Introduction: The present study aimed to assess organ absorbed and effective doses in CT examinations performed with automatic exposure control (AEC) and fixed tube current (FTC).
Materials/Methods: Scanning parameters were obtained for routine adult CT examinations and used to estimate the organ absorbed and effective doses using CT – Expo dosimetry software. The estimated effective doses were based on the International Commission on Radiological Protection publication 103 recommendation.
Results: For scans performed with AEC, doses to head, chest, abdomen and pelvic organs ranged from 19.7 - 41.8 mGy; 6.4 - 17.4 mGy; 19.2 - 20.9 mGy and 10.5 - 24.9 mGy respectively, and the effective doses were; 1.6, 6.1, 6.4 and 5.4 mSv respectively. For FTC acquisitions, doses to organs ranged from 16.7 – 75.5 mGy (head CT), 4.1 – 52.2 mGy (chest CT), and 10.6 – 33.2 mGy (abdomen CT) and 5.2 – 38.7 mGy (pelvis CT) respectively, and the mean effective doses were; 2.1, 6.9, 9.4 and 6.1 mSv respectively. Comparatively, examinations performed with AEC activated induced a dose reduction of 9 and 34% for head organs; 52, 62 and 25% for chest organs; 16 and 14% for abdomen organs; and 11 and 10% for pelvic organs than the FTC acquisitions. A dose increase of 3% was observed for testes. The mean effective doses for scans with AEC activated were 13 – 46% lower compared to FTC scans.
Conclusion: The study results shows, estimated doses for CT scans with AEC activated were lesser compared with FTC techniques. Thus, its usage is recommended for CT examinations in ensuring optimal dose reduction to radiosensitive organs.

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Articles in Press, Accepted Manuscript
Available Online from 15 March 2019
  • Receive Date: 24 January 2019
  • Revise Date: 13 March 2019
  • Accept Date: 15 March 2019