High correlation between radiation dose estimates for 256‐slice CT obtained by highly parallelized hybrid Monte Carlo computation and solid‐state metal‐oxide semiconductor field‐effect transistor measurements in physical anthropomorphic phantoms

Abstract

Purpose: Accurate, patient-specific radiation dosimetry for CT scanning is critical to optimize radiation doses and balance dose against image quality. While Monte Carlo (MC) simulation is often used to estimate doses from CT, comparison of estimates to experimentally measured values is lacking for advanced CT scanners incorporating novel design features. We aimed to compare radiation dose estimates from MC simulation to doses measured in physical anthropomorphic phantoms using metaloxide semiconductor field-effect transistors (MOSFETs) in a 256-slice CT scanner. Methods: Fifty MOSFETs were placed in organs within tissue-equivalent anthropomorphic adult and pediatric radiographic phantoms, which were scanned using a variety of chest, cardiac, abdomen, brain, and whole-body protocols on a 256-slice system. MC computations were performed on voxelized CT reconstructions of the phantoms using a highly parallel MC tool developed specifically for diagnostic X-ray energies and rapid computation. Doses were compared between MC estimates and physical measurements. Results: The average ratio of MOSFET to MC dose in the in-field region was close to 1 (range, 0.96-1.12; mean AE SD, 1.01 AE 0.04), indicating outstanding agreement between measured and simulated doses. The difference between measured and simulated doses tended to increase with distance from the in-field region. The error in the MC simulations due to the limited number of simulated 5216 photons was less than 1%. The errors in the MOSFET dose determinations in the in-field region for a single scan were mainly due to the calibration method and were typically about 6% (8% if the error in the reading of the ionization chamber that was used for the MOSFET calibration was included). Conclusions: Radiation dose estimation using a highly parallelized MC method is strongly correlated with experimental measurements in physical adult and infant anthropomorphic phantoms for a wide range of scans performed on a 256-slice CT scanner. Incorporation into CT scanners of radiation-dose distribution estimation, employing the scanner's reconstructed images of the patient, may offer the potential for accurate patient-specific CT dosimetry.

Cardiac-Specific Conversion Factors to Estimate Radiation Effective Dose From Dose-Length Product in Computed Tomography

“…Our motivation was to avoid the need to make assumptions regarding proprietary aspects of scanner design and protocols, which would have been required for Monte Carlo simulation. Even so, for a single scanner we have compared MOSFET to Monte Carlo estimation of effective dose and found outstanding agreement (24).…”

Recent Advances in Hydrogel-Based Sensors Responding to Ionizing Radiation

“…The sensors that are applied to accurately measure radiation doses are often called dosimeters. They include metal-oxide-semiconductor field-effect transistors (MOSFETs), silicon diodes, films, ionization chambers and thermoluminescence dosimeters (TLDs), as well as many others (Figure 1) [4][5][6][7][8][9][10]. MOSFETs are expensive and operate at high voltages, which makes them unsuitable for in situ dose measurements.…”

“…In addition, the above-mentioned dosimeters often require sophisticated preparation technologies and operation conditions, which restrict their applications. [4] with permission from John Wiley and Sons, (b) a finger TLD, adapted from ref. [5] with permission from Elsevier, (c) flexible film dosimeter, adapted from ref.…”

“…We expect more experts from different fields of science such as materials science, chemistry, cancer therapy, radiobiology and nuclear science to work together to achieve clinical applications of gel dosimeters. [4] with permission from John Wiley and Sons, (b) a finger TLD, adapted from ref. [5] with permission from Elsevier, (c) flexible film dosimeter, adapted from ref.…”

Otimização de doses em procedimentos de tomografia computadorizada pediátrica

“…As estimativas de doses em tomografia computadorizada pediátrica têm sido uma área de grande interesse por causa da maior conscientização dos riscos de radiação associados à exposição desta modalidade na infância (VASSILEVA; REHANI; KOSTOVA-LEFTEROVA; AL-NAEMI et al, 2015). A preocupação com a exposição à radiação tem sido acompanhada pelo interesse em reduzir as doses de radiação mantendo a qualidade da imagem para o diagnóstico (PRINSEN; TRATTNER; WIEGERT;GERLAND et al, 2019). Atualmente existem campanhas de proteção radiológicas como Latin Safe (LATIN SAFE, 2015), EuroSafe (EUROSAFE, 2014), Image Wisely (IMAGE WISELY, 2010-20) e Image Gently (IMAGE GENTLY, 2014) (para pacientes pediátricos) que promovem boas práticas e fornecem diretrizes e orientações para o uso consciente da radiação ionizante para imagens médicas.…”