Objectives: Computed tomography (CT) has been used to measure body composition, however, a technique with reduced radiation exposure has not yet been introduced. This study tested a low-dose spiral CT technique on a phantom to determine its validity and reproducibility. The method was then applied for volume and distribution measurements in patients.
Design: Construction and measurement of a phantom followed by measurement of patients referred to CT for clinical indications.
Setting: Radiology Department, University Hospital.
Subjects: Twenty-four post-gastrectomy patients.
Intervention: A 22 cm phantom with a known amount of water and fat was scanned using high- and low-dose technique, standard and double table speed during a volumetric scan. The low-dose technique was implemented in the patient group. Total volume, total fat and four defined compartmental fat volumes in the truncal area were measured.
Results: The mean fat volume measured using the low-dose CT technique in the phantom was 0.2% above the actual fat content. The coefficient of variation for this method was 5%. By using low-dose, double speed instead of standard-dose technique, radiation exposure to the skin was decreased by more than 90% (equivalent to 4 mGy) of what is used in diagnostic imaging. The patient scans showed that no significant differences in BMI and total measured volume existed between female and male patients, but percent fat and percent subcutaneous fat were significantly larger in women (P = 0.006 and 0.002, respectively), as were percent intraabdominal and mediastinal fat in men (P = 0.002 and 0.003 respectively).
Conclusions: Low-dose spiral CT accurately measures fat volume in vitro, and can be used in vivo for compartmental fat measurements.