전신 PET/CT 검사에서 환자의 팔 위치에 따른 CT 유효선량의 비교 연구

A Comparative Study on the CT Effective Dose by the Position of Patient’s Arm

Purpose: In the whole body PET/CT scan, it is natural to lift the patient’s arm for its quality improvement. However, when the lesion is located in head and neck, the arms should be located lower. This study was designed to compare the CT effective dose for each arm position applying Automatic Exposure Control (AEC). Materials and Methods: 45 patients who had ¹⁸F-FDG whole body PET/CT scan were studied with Biograph Truepoint 40 (SIEMENS, GERMANY), Biograph Sensation 16 (SIEMENS, GERMANY), Discovery STe 8 (GE healthcare, USA). The CT effective dose of 15 patients for each equipment was measured and comparatively analyzed in both arm-lifted position and lower-arm position. ImPACT v1.0 program was used as the method of measurement for CT effective dose. For the statistics analysis, Paired t-test which paired with SPSS 18.0 statistic program was applied. Results: In the case of arm-lifted, it was measured as 6.33±0.93 mSv for Biograph Sensation 16, 8.01±1.34 mSv for Biograph Truepoint 40, and 9.69±2.32 mSv for Discovery STe 8. When arms are located lower position, it was measure as 6.97±0.76 mSv, 8.95±1.85 mSv, 13.07±2.87 mSv for each. CT effective dose according to the arm position was 9.2% for Biograph Truepoint 40, 10.5% for Biograph Sensation 16, and 25.9% for Discovery Ste 8. The statistics analysis showed the meaningful difference (p<0.05). Conclusion: For the whole body PET/CT case, CT effective dose applying AEC was decreased the radiation exposure of the patients when the arm was lifted for 15.2% of average value. The patient who has no lesion in head and neck would decrease the artifact occurrence in objective part and lower the CT effective dose. Also, for the patient who had lesion in head and neck, the artifact in objective part can be lower by putting the arms down, the fact that CT effective dose increases should be concerned in its whole body PET/CT scan.