SU-E-T-271: Direct Measurement of Tenth Value Layer Thicknesses for High Density Concretes with a Clinical Machine
Abstract
Purpose: Use of high density concrete for radiation shielding is increasing, trading cost for space savings associated with the reduced tenth value layer (TVL). Precise information on the attenuation properties of high-density concretes is not readily present in the literature. A simple approximation is to scale the TVLs from NCRP 151 according relative increase in density. Here we present measured TVLs for heavy concretes of various densities using a built-in shielding test port. Methods: Concrete densities tested range from 2.35 g cc−1 (147 pcf) to 5.6 g cc−1 (350 pcf). Measurements were taken using 6MV, 6FFF, and 10FFF on a Varian Truebeam linear accelerator. Field sizes of 4x4, 9x9 and 30x30 cm2 were measured. A PTW 31013 Farmer chamber with a buildup cap was positioned 5.5 m from isocenter along the beam CAX. Concrete thicknesses were incremented in 5 cm intervals. Comparison TVLs were determined by scaling the NCRP 151 TVLs by the density ratio between the sample and standard density. Results: The trend from the first to equilibrium TVL was an increase in thickness, compared with MC modeling, which predicted a decrease. Measured TVLs for 6 MV were reduced by as much as 8.9 cm for TVL₁ and 3.4 cm for TVLE compared to values scaled from NCRP 151. There was 1–3 mm difference in TVL between measurements done at 4x4 versus 30x30 cm2. TVL₁ for 6FFF was 1.1 cm smaller than TVL₁ for 6MV, but TVLE was consistent to within 4 mm. TVL₁ and TVLE for 10FFF were reduced by 8.8 and…
Read the paper
Related studies
- Global, regional, and national burden of hepatitis B, 1990–2019: a systematic analysis for the Global Burden of Disease Study 2019
- A meta‐analysis of anal cancer incidence by risk group: Toward a unified anal cancer risk scale
- Global fertility in 204 countries and territories, 1950–2021, with forecasts to 2100: a comprehensive demographic analysis for the Global Burden of Disease Study 2021
- Exercise interventions in Alzheimer's disease: A systematic review and meta-analysis of randomized controlled trials
- Prognostic Significance of Carbonic Anhydrase IX Expression in Cancer Patients: A Meta-Analysis
- Glucocorticoid Resistance: Is It a Requisite for Increased Cytokine Production in Depression? A Systematic Review and Meta-Analysis
Go deeper in Evidence Hub
Evidence Hub adds a study data sheet (design, sample size, evidence level, key numbers), an AI summary and a chat grounded in the paper's text.