Consideration of the usefulness of a size-specific dose estimate in pediatric CT examination

Abstract

Computed tomography (CT) has recently been utilized in various medical settings, and technological advances have resulted in its widespread use. However, medical radiation exposure associated with CT scans accounts for the largest share of examinations using radiation; thus, it is important to understand the organ dose and effective dose in detail. The CT dose index and dose–length product are used to evaluate the organ dose. However, evaluations using these indicators fail to consider the age and body type of patients. In this study, we evaluated the effective dose based on the CT examination data of 753 patients examined at our hospital using the size-specific dose estimate (SSDE) method, which can calculate the exposure dose with consideration of the physique of a patient. The results showed a large correlation between the SSDE conversion factor and physique, with a larger exposure dose in patients with a small physique when a single scan is considered. Especially for children, the SSDE conversion factor was found to be 2 or more. In addition, the patient exposed to the largest dose in this study was a 10-year-old, who received 40.4 mSv (five series/examination). In the future, for estimating exposure using the SSDE method and in cohort studies, the diagnostic reference level of SSDE should be determined and a low-exposure imaging protocol should be developed to predict the risk of CT exposure and to maintain the quality of diagnosis with better radiation protection of patients.

Radiation doses with various body weights of phantoms in brain 128-slice MDCT examination

“…The DLP denotes the total energy absorbed during (and therefore the potential biological effect attributable to) the complete scan [18, 19]. normalHnormalEprefix,normalDLPtrue(mSvtrue)≒normalk×normalDLPwhere k (mSv mGy −1 cm −1 ) is the conversion factor of H E,DLP /DLP for the CT scan.…”

“…ICRP 103 states that, using this methodology, H E,DLP can be estimated from DLP, which is obtained by most CT systems; k values for the Rando and various body weight phantoms are Rando, 0.0019; 10 kg, 0.0053; 30 kg, 0.0027; 50 kg, 0.0019; 70 kg, 0.0019; and 90 kg, 0.0019 mSv mGy −1 cm −1 [18, 19, 28]. In addition, the protocol of H E,DLP calculation is most commonly used in a clinical setting.…”

“…A simple equation can be used to estimate H E,TLD for brain CT examinations of phantoms with various body weights [16, 17]. H E,DLP values were calculated herein using the computed tomography dose index (CTDI vol ) and the dose–length product (DLP), displayed on the console monitor of the 128-slice CT scanner; these values were then multiplied by the conversion coefficient ( k ) recommended by ICRP 103 [18, 19]. The DLP conversion method is commonly used in clinical practice owing to its simplicity and the ready accessibility of H E,DLP .…”

Simplified approach to estimation of organ absorbed doses for patients undergoing abdomen and pelvis CT examination

“…D w can be calculated using attenuation values from axial images at each position along the longitudinal direction, but calculation of D w requires sophisticated computer software. Studies calculating mean absorbed doses for organs covered by the primary beam, such as the liver, stomach, and kidney, show strong relationships between SSDE and calculated organ doses [6,[12][13][14]. Therefore, it would be useful to be able to calculate values for the SSDE for sections of the trunk including these organs in order to provide assessments of the organ doses, which can give better indications of risk than the effective dose [15].…”

Patient-specific organ dose calculated by dose tracking software based on monte carlo simulation in pediatric abdominal CT

“…Tsujiguchi T, et al (18) (2018) investigated the effective dose for CT examinations with consideration of patients' body type using SSDE in pediatric CT. They collected data from 753 patients who underwent CT examination of trunk region.…”