Dose Comparison of Obese and Non-Obese Patients During CT Abdomen Scan: Review Study

Abstract

Introduction: Dose is the matter of concern as the role of CT imaging is increasing day by day due to its rapid scanning and 3 D cross section imaging. CT represents approximately 10% of X-ray based examination which accounts for almost 50% radiation dose associated with total medical imaging. Amount of dose also depend on patient size. Patients having more body fat are assumed to have more radiation dose due to attenuation and scattering.

Objectives: Purpose of the study is to find out the radiation dose variation on the basis of Body Mass index and patient dimensions (Anteroposterior & Lateral diameter of abdomen).

Methods: All of the original research articles were explored to find the relation of patient size with dose during CT abdomen scan. The articles were differentiated on the basis of Prisma technique. The patients which are clinically referred for CT abdomen were included and some studies were anthropomorphic phantom based. Patient’s data include height, weight, age, sex is collected. The following parameters were included: Body mass index (BMI), Anteroposterior & Lateral diameters, subcutaneous fat thickness, cross sectional area Scan is performed and CT dose index (CTDI), dose length product (DLP), were recorded and effective dose, size specific effective dose (SSDE) is calculated by using size specific conversion factor.

Results: Before calculating the radiation dose of patient, the patient’s size, weight, BMI, adipose tissue thickness & circumference are some major factors that interferes the amount of dose. It is found that oversized patients receive significantly higher doses than small size patients. It is an interesting fact that during CT abdomen scan of obese patients, there is no significant increase in organ doses because somewhere extra subcutaneous and visceral fat layers in obese patients. To balance the amount of dose and image quality, modified protocols using low kV techniques or ATCM (automated tube current modulation) were used.

Conclusions: Patient size, BMI, cross section area all parameters should be used to calculate effective dose. Increased cross section area, directly increase the exposure parameters and large dose to thick patients.