Visual grading characteristics and ordinal regression analysis during optimisation of CT head examinations.

Francis Zarb,Louise Rainford,Mark F Mcentee

doi:10.1007/s13244-014-0374-9

Francis Zarb, Louise Rainford + Show 1 more

Open Access

https://doi.org/10.1007/s13244-014-0374-9

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Abstract

ObjectivesTo evaluate visual grading characteristics (VGC) and ordinal regression analysis during head CT optimisation as a potential alternative to visual grading assessment (VGA), traditionally employed to score anatomical visualisation.MethodsPatient images (n = 66) were obtained using current and optimised imaging protocols from two CT suites: a 16-slice scanner at the national Maltese centre for trauma and a 64-slice scanner in a private centre. Local resident radiologists (n = 6) performed VGA followed by VGC and ordinal regression analysis.ResultsVGC alone indicated that optimised protocols had similar image quality as current protocols. Ordinal logistic regression analysis provided an in-depth evaluation, criterion by criterion allowing the selective implementation of the protocols. The local radiology review panel supported the implementation of optimised protocols for brain CT examinations (including trauma) in one centre, achieving radiation dose reductions ranging from 24 % to 36 %. In the second centre a 29 % reduction in radiation dose was achieved for follow-up cases.ConclusionsThe combined use of VGC and ordinal logistic regression analysis led to clinical decisions being taken on the implementation of the optimised protocols. This improved method of image quality analysis provided the evidence to support imaging protocol optimisation, resulting in significant radiation dose savings.Main Messages• There is need for scientifically based image quality evaluation during CT optimisation.• VGC and ordinal regression analysis in combination led to better informed clinical decisions.• VGC and ordinal regression analysis led to dose reductions without compromising diagnostic efficacy.

Highlights

Producing high-quality images in computerised tomography (CT) is important for image interpretation to ensure that the maximum diagnostic information is available to facilitate the visualisation of discrete changes in anatomy indicating early pathological processes [1,2,3]
The standard of image quality mainly depends on the preferences of radiologists and their willingness to balance low-noise, high-quality CT images with the impact upon radiation levels administered
Noise is a major factor in determining acceptable image quality and often dictates the radiation dose for a particular CT protocol

Summary

Introduction

Producing high-quality images in computerised tomography (CT) is important for image interpretation to ensure that the maximum diagnostic information is available to facilitate the visualisation of discrete changes in anatomy indicating early pathological processes [1,2,3]. Higher quality CT images, normally imply a higher radiation dose to the patient since changes in scan parameters are required to facilitate high resolution [4]. The standard of image quality mainly depends on the preferences of radiologists and their willingness to balance low-noise, high-quality CT images with the impact upon radiation levels administered. Noise is a major factor in determining acceptable image quality and often dictates the radiation dose for a particular CT protocol. Increases in noise degrade both low-contrast resolution and spatial resolution and influence the radiologists’ perception of the image [5,6,7,8]. An increase in noise up to certain levels may not necessarily impair the image diagnosis [9, 10]

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