Reach out to us to discuss all your radiation safety needs.
RESEARCH
CT scatter spectra transmission data of 80, 100, 120 and 140 kVp primary beams for various shielding materials
Abstract: The shielding of computed tomography (CT) suites has commonly relied on the assumption that the primary beam has the same beam quality and thus penetrability as the scattered radiation. This report expands on a preliminary work that showed scattered radiation from patients having an overall reduced beam quality, with published transmission data for 120 kVp and 140 kVp through lead. Beam quality data of patient scatter spectra for 80 kVp and 100 kVp are uniquely provided herein using the same methodology, expanding the diagnostic energy range. The mean energy of scatter radiation spectra across this 80–140 kVp diagnostic range was found to have a reduction of 13.4–17.9% compared to a primary beam with a defined 9.8 mm Al added filtration. A DOSXYZnrc Monte Carlo program using the EGSnrc photon and electron transport code was subsequently used to simulate the transmission of scattered spectra of all 80, 100, 120 and 140 kVp beams through various commonly used shielding materials, including lead, concrete, steel, plate glass and gypsum wallboard. Transmission data and Archer fitting coefficients for this scattered radiation were calculated and show a reduction in transmission over the range of practical shielding thicknesses for these materials. Transmission through lead was significantly reduced in comparison to the National Council of Radiological Protection (NCRP) and British Institute of Radiology (BIR) methodologies using primary beam spectra, with transmissions reduced between 40.4 and 63.9% for 120 kVp and between 38.1 and 42% for 140 kVp beams over a 0.44–2.64 mm thickness range. The use of CT scatter spectra and their resultant transmission data is recommended for optimal shielding design.
https://link.springer.com/article/10.1007/s13246-024-01494-x
Comparative analysis of patient scatter to phantom scatter for computed tomography systems
Abstract: Current computed tomography (CT) shielding practices are largely based on calculations of scattered radiation emitted from an acrylic head or body phantom, such as the Computed Tomography Dose Index (CTDI) phantom, or anthropomorphic phantoms of these two anatomical categories. This report considers the difference in scattered air kerma or dose from phantom models, to actual patient scatter under a variety of clinical scan conditions. Empirical patient scatter measurements recorded at different positions around the gantry, for 3 different CT scanners, resulted in average patient scatter fractions per unit Dose Length Product (DLP: mGy cm) at 1 m from the isocentre of 0.09 ± 0.03 and 0.17 ± 0.04 µGy (mGy cm)−1 for head and body scans respectively. For the purposes of shielding design and scattered dose estimates to staff it is recommended that a single standard deviation be applied to these averages in the continued interest of conservatism. These values are reasonably comparative to the widely published scatter fractions by the National Council of Radiological Protection using the CTDI phantom, and the British Institute of Radiology using head and body anthropomorphic phantoms.
https://link.springer.com/article/10.1007/s13246-022-01158-8
Monte Carlo Modeling of Computed Tomography Ceiling Scatter for Shielding Calculations
Abstract: Radiation protection for clinical staff and members of the public is of paramount importance, particularly in occupied areas adjacent to computed tomography scanner suites. Increased patient workloads and the adoption of multi-slice scanning systems may make unshielded secondary scatter from ceiling surfaces a significant contributor to dose. The present paper expands upon an existing analytical model for calculating ceiling scatter accounting for variable room geometries and provides calibration data for a range of clinical beam qualities. The practical effect of gantry, false ceiling, and wall attenuation in limiting ceiling scatter is also explored and incorporated into the model. Monte Carlo simulations were used to calibrate the model for scatter from both concrete and lead surfaces. Gantry attenuation experimental data showed an effective blocking of scatter directed toward the ceiling at angles up to 20-30° from the vertical for the scanners examined. The contribution of ceiling scatter from computed tomography operation to the effective dose of individuals in areas surrounding the scanner suite could be significant and therefore should be considered in shielding design according to the proposed analytical model.
Ready To Engage With SPS?
Menu
Providing comprehensive radiation safety and protection services throughout Mauritius.
Based in Grand Baie, Mauritius
Available 9am – 5pm Mon – Fri
Copyright © 2025 Spectra Protection Services – All rights reserved.