Radiation Dose Reduction in CT Torsion Measurement of the Lower Limb: Introduction of a New Ultra-Low Dose Protocol.

Gabriel Keller,Fabian Springer,Simon Götz,Saif Afat,Mareen Sarah Kraus,Leonard Grünwald

doi:10.3390/diagnostics11071209

Gabriel Keller, Fabian Springer + Show 4 more

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https://doi.org/10.3390/diagnostics11071209

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Abstract

This study analyzed the radiation exposure of a new ultra-low dose (ULD) protocol compared to a high-quality (HQ) protocol for CT-torsion measurement of the lower limb. The analyzed patients (n = 60) were examined in the period March to October 2019. In total, 30 consecutive patients were examined with the HQ and 30 consecutive patients with the new ULD protocol comprising automatic tube voltage selection, automatic exposure control, and iterative image reconstruction algorithms. Radiation dose parameters as well as the contrast-to-noise ratio (CNR) and diagnostic confidence (DC; rated by two radiologists) were analyzed and potential predictor variables, such as body mass index and body volume, were assessed. The new ULD protocol resulted in significantly lower radiation dose parameters, with a reduction of the median total dose equivalent to 0.17 mSv in the ULD protocol compared to 4.37 mSv in the HQ protocol (p < 0.001). Both groups showed no significant differences in regard to other parameters (p = 0.344–0.923). CNR was 12.2% lower using the new ULD protocol (p = 0.033). DC was rated best by both readers in every HQ CT and in every ULD CT. The new ULD protocol for CT-torsion measurement of the lower limb resulted in a 96% decrease of radiation exposure down to the level of a single pelvic radiograph while maintaining good image quality.

Highlights

Stated is the correlation w showed no significant difference in demographic parameters, such as age at time of Computed tomography (CT), lowest equational degree, respective of the lowest p-value, if there were no sig gender, and body mass index (BMI)
Our results show that by applying the new ultra-low dose (ULD) CT protocol, a significant dose reduction to 0.17 mSv can be achieved at an acceptable contrast-to-noise ratio (CNR) level whilst maintaining diagnostic confidence (DC)
Protocol with approximately 100 kV/20 mAs and 80 kV/10 mAs in CT torsion measurement of the lower limb results in an approximately 96% decrease in effective radiation exposure compared to our high-quality CT (HQ CT) protocol

Summary

Introduction

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Torsional malalignment is a common lower limb abnormality in children and adults. Causes of torsional malalignment are multifactorial and may originate from overuse, trauma, muscular imbalance, or congenital disorders [1,2,3,4,5]. It is known that torsional malalignment is a risk factor for the development of osteoarthritis and related disorders [6,7,8,9,10,11]. Measurement of lower limb torsion is recommended as a crucial part of the clinical workup, e.g., after recurrent patellar dislocations [12,13,14]

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