A study on correlation between thyroid CT radiation dose, image quality and female body composition

Background and purpose: With the increasing use of medical imaging examinations, Computed tomography (CT) scans have become one of the primary sources of effective dose. This study analyzed the correlation between radiation dose, image quality and body composition in thyroid CT to provide a data foundation for better control of radiation dose and image quality in the future. Methods: A retrospective analysis was conducted on patients who underwent thyroid CT scans at Fudan University Shanghai Cancer Center from January 2015 to December 2019. CT values and standard deviations (SD) of the homogeneous parenchyma of the thyroid were collected, and CT values and SD values of adjacent subcutaneous fat tissue were measured with the same region of interest (ROI) size. All data were measured three times to obtain the average value, and the volume CT dose index (CTDIvol) and dose-length product (DLP) were recorded. Effective dose values and signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) for various parts were calculated. All patients underwent bone density examinations, and patient height, weight, body mass index (BMI), body surface area (BSA), and the percentage of muscle and fat in the spine and thighs were recorded. Results: A total of 104 patients were enrolled in this study. The SNR of thyroid CT images and the percentage of spinal muscle (r=0.284, P=0.004), CNR of thyroid CT images and the percentage of spinal fat (r=0.197, P=0.045), and the effective dose of thyroid CT images and age, weight, BMI, thigh fat percentage, and body surface area (r=0.221, 0.247, 0.260, 0.262, and 0.222; P=0.024, 0.011, 0.008, 0.007 and 0.024) were positively correlated. While, SNR and age, weight, BMI, and the percentage of spinal fat (r=-0.292, -0.198, -0.207, and -0.284; P=0.003, 0.044, 0.035, 0.004), CNR and the percentage of spinal muscle (r=-0.197, P=0.045), and the effective dose and the percentage of thigh muscle (r=-0.262, P=0.007) were negatively correlated. Conclusion: The radiation dose in thyroid CT is correlated with female body composition. The image quality is related to female body composition, providing a data foundation for better control of radiation dose and image quality in the future.