Low-dose spiral computed tomography for measuring abdominal fat volume and distribution in a clinical setting

Abstract

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 de®ned 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 coef®cient 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 signi®cant differences in BMI and total measured volume existed between female and male patients, but percent fat and percent subcutaneous fat were signi®cantly 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.

Optimal CT Number Range for Adipose Tissue When Determining Lean Body Mass in Whole-Body F-18 FDG PET/CT Studies

“…This difference in the CT number distribution for VAT compared with the other two AT compartments could be attributable to the effect of partial volume averaging, which is partly due to blood vessels within pixels, and differences in biological properties between AT compartment, including differences in the fat fraction of AT, blood flow, and glucose metabolism [14,23,24]. This observation agreed with a previous report [25].…”

“…Theoretically, X-ray tube voltage by different scanner type may affect the CT number for particular tissues owing to different linear attenuation coefficients, but tube current does not affect CT number for particular tissue, although low-dose scanning used in the current study increases image noise as described in a previous phantom study [25]. The clinical significance of using slightly different tube voltage in measuring total AT volume is questionable.…”

“…They found that the mean percentage difference (difference relative to the mean) ranged from −12 to 23 %. Some investigators have proposed flexible CT number ranges for AT using the mean CT number ± 2 SD, or the minimum/maximum CT numbers for each patient [18,25,29]. However, the CT number distributions for VAT differ from other AT compartment and the mean CT number ± 2 SD or the minimum/maximum CT numbers would have to be determined for each patient, which makes the application of such a method highly inconvenient in clinical settings.…”

A novel method of measuring intra-abdominal fat volume using helical computed tomography

“…In 1998, it was clarified by using low-dose helical CT technique in 24 post-gastrectomy subjects comprising nine women and 15 men with a mean age of 60 y, that percentage fat and percentage subcutaneous fat were significantly greater in women than was percentage intra-abdominal fat in men. 5 However, they did not study the correlation between fat volumes by helical CT vs those respective areas measured using conventional methods.…”

“…Until recently, however, there had been no study that applied this technique to the measurement of body fat mass. Rogalla et al 5 reported with low-dose helical CT in 24 post-gastrectomy patients that percentage fat and percentage subcutaneous fat were significantly larger in women, as were percentage intra-abdominal and mediastinal fat in men.…”