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

Abstract

The effective dose (HE) and organ or tissue equivalent dose (HT) for use in brain computed tomography (CT) examinations with various body weights were evaluated. Thermoluminescent dosimeters (TLD-100H) were inserted into Rando and five anthropomorphic phantoms. These phantoms were made of polymethylmethacrylate (PMMA), according to the specifications of ICRU 48, with masses from 10 to 90 kg. Brain CT examinations were conducted, scanning the maxillae from the external auditory meatus to the parietal bone using a 128-slice multi-detector CT (MDCT) scanner. To reduce errors, three independent trials were conducted. Calculated HE,TLD, based on the weighting factor recommended by ICRP 103, was 1.72 ± 0.28 mSv, which slightly exceeds the HE,DLP of 1.70 mSv, that was calculated from the dose–length product (DLP) of the Rando phantom. This experiment yielded HE,TLD values of ICRP 103 from the highest 1.85 ± 0.28 (90 kg) to the lowest 1.47 ± 0.22 (10 kg) mSv. HE,TLD (mSv) = 5.45×10−3 W(kg) + 1.361, with an R2 of 0.87667. Using the DLP protocol, HE,DLP was estimated from CTDIvol that was recorded directly from the console display of the CT unit and multiplied by the conversion coefficient (k) recommended by the ICRP 103. Finally, the experimental results obtained herein are compared with those in the literature. Physicians should choose and adjust protocols to prevent the exposure of patients to unnecessary radiation, satisfying the as low as reasonably achievable (ALARA) principle. These findings will be valuable to patients, physicians, radiologists and the public.

Evaluating dose distributions of normal organs for patients undergoing VMAT therapy of nasopharyngeal carcinoma using Rando phantom and TLD-100H

“…The Rando was embedded in the anthropomorphic material. The densities (g cm −3 ) of the components were 0.32 for the lungs, 0.98 for the soft tissue, and 2.70 for the skeleton [3,4,6,10].…”

“…The volumetric modulated arc therapy (VMAT) of an Axesse (Elekta 2538) linear accelerator (linac) is a novel effective treatment for many cancers [2,3]. However, the Axesse generates high-energy up to 6 MV radiations during NPC treatment [4][5][6][7][8]. Patients may be exposed to undesirable high energy x-ray primarily due to out-of-field radiations.…”

“…Patients may be exposed to undesirable high energy x-ray primarily due to out-of-field radiations. However, the peripheral dose (PD) is an important issue [4]. Patients always ask physicians as well as radiologist can tell how much extra radiations exposured to normal tissues or organs.…”

“…In order to reduce experimental errors. Quantitatively measured E and D T of patients can provide data for revising plans for treating NPC and determining radiation safety [2][3][4]9]. Thermoluminescent dosimers (TLD-100H, 3.0 × 3.0 × 1.0 mm 3 ) were made by Harshaw, solon, OH, USA.…”

Development of a method to create uniform phantoms for task‐based assessment of CT image quality

“…The contrast results from the difference of these materials’ linear attenuation coefficients and can be calculated, if the chemical composition and the physical density of the materials are known. Polymethyl methacrylate (PMMA) is a uniform material frequently used for phantom bodies 7,8 . A second material to generate a signal can be a homogeneous fructose solution, which has the advantage that the contrast can be adjusted by the concentration of the solution.…”