Impact of gonad shielding for AP pelvis on dose and image quality on different female sizes: A phantom study

C Buissink,M Alrowily,C Dougoud,J Linneman,M Lirot,N Mzobe,A.K Tootell,A Van Der Heij-Meijer

doi:10.1016/j.radi.2020.06.013

Abstract

IntroductionIn clinical practice AP pelvis standard protocols are suitable for average size patients. However, as the average body size has increased over the past decades, radiographers have had to improve their practice in order to ensure that adequate image quality with minimal radiation dose to the patient is achieved. Gonad shielding has been found to be an effective way to reduce the radiation dose to the ovaries. However, the effect of increased body size, or fat thickness, in combination with gonad shielding is unclear.The goal of the study was to investigate the impact of gonad shielding in a phantom of adult female stature with increasing fat thicknesses on SNR (as a measure for image quality) and dose for AP pelvis examination. MethodsAn adult Alderson female pelvis phantom was imaged with a variety of fat thickness categories as a representation of increasing BMI. 72 images were acquired using both AEC and manual exposure with and without gonad shielding. The radiation dose to the ovaries was measured using a MOSFET system. The relationship between fat thickness, SNR and dose when the AP pelvis was performed with and without shielding was investigated using the Wilcoxon signed rank test. P-values < 0.05 were considered to be statistically significant. ResultsOvary dose and SNR remained constant despite the use of gonad shielding while introducing fat layers. ConclusionThe ovary dose did not increase with an increase of fat thickness and the image quality was not altered. Implications for practiceBased on this phantom study it can be suggested that obese patients can expect the same image quality as average patients while respecting ALARA principle when using adequate protocols.

Highlights

In clinical practice AP pelvis standard protocols are suitable for average size patients
The aim of this study is to investigate the impact of gonad shielding in a phantom of adult female stature with increasing fat thicknesses on signal-noise ratio (SNR) and dose for AP pelvis examination
Our study shows that shielding is useful to reduce ovary dose for Automatic Exposure Control (AEC) and manual exposures

Summary

Introduction

In clinical practice AP pelvis standard protocols are suitable for average size patients. As the average body size has increased over the past decades, radiographers have had to improve their practice in order to ensure that adequate image quality with minimal radiation dose to the patient is achieved. The goal of the study was to investigate the impact of gonad shielding in a phantom of adult female stature with increasing fat thicknesses on SNR (as a measure for image quality) and dose for AP pelvis examination. In clinical practice AP pelvis standard protocols are based on optimisation studies for average size patients.[1,2] as the average body size of the western population has increased over the past decades, radiographers have had to adapt radiographic technique including exposure factors in order to produce optimal images with adequate image quality and minimized radiation dose to the patient.[3] Imaging overweight patients requires an increase in exposure factors, which results in scatter radiation that overall decreases image quality.[4 ] S72. Male gonads are overall easier to protect with gonad shielding as they are outside the body.[6]

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