A phantom study on influence of tube voltage on CT dose and CT image quality in PET/CT

Objective: To examine how to decrease of radiation dose caused by CT in PET/CT while ensuring quality of CT image. Methods: CT dose phantom(DCT 10) and CT performance phantom(Catphan?500) were scanned in the tube voltage 80 kV, 100 kV, 120 kV and 140 kV with PET/CT(GE Discovery ST16). The image quality was evaluated by high contrast resolution,low contrast resolution, uniformity and noise. CTDIw and CTDIvol were calculated. The relationship between CT image quantity and CT dose was analyzed. Results: CT dose increased linearly with the tube voltage. The high contrast resolution of CT image was independent of the tube voltage. The performances of CT image, low contrast resolution, uniformity and noise, improved with increasing tube voltage, and it was nolinear. Conclusion: The performances of CT image improved with increasing CT dose. It improved more slowly when the CT dose reach to a certain value. The radiation dose by CT in PET/CT could be decreased appropriately under the guarantee of the quality of the CT image.