Effective dose and image optimisation of lateral lumbar spine radiography: a phantom study

Zer Hau Lai,Zhonghua Sun,Cláudia Sá Dos Reis

doi:10.1186/s41747-019-0132-3

Abstract

BackgroundTo investigate lateral lumbar spine radiography technical parameters for reduction of effective dose whilst maintaining image quality (IQ).MethodsThirty-six radiograms of an anthropomorphic phantom were acquired using different exposure parameters: source-to-detector distance (SDD) (100, 130 or 150 cm), tube potential (75, 85 or 95 kVp), tube current × exposure time product (4.5, 9, 18 mAs) and additional copper (Cu) filter (no filter, 0.1-, 0.2-, or 0.3-mm thickness. IQ was assessed using an objective approach (contrast-to-noise-ratio [CNR] calculation and magnification measurement) and a perceptual approach (six observers); ED was estimated using the PCXMC 2.0 software. Descriptive statistics, paired t test, and intraclass correlation coefficient (ICC) were used.ResultsThe highest ED (0.022 mSv) was found with 100 cm SSD, 75 kVp, 18 mAs, and without Cu filter, whilst the highest CNR (7.23) was achieved at 130 cm SSD, 75 kVp, 18 mAs, and without Cu filter. The lowest ED and CNR were generated at 150 cm SDD, 95 kVp, 4.5 mAs, and 0.3-mm Cu filter. All observers identified the relevant anatomical structures on all images with the lowest ED and IQ. The intra-observer (0.61–0.79) and inter-observer (0.55–0.82) ICC ranged from moderate to excellent.ConclusionAll relevant anatomical structures were identified on the lateral lumbar spine radiographs despite using low-dose protocols. The lowest ED (0.002 mSv) was obtained with 150 cm SDD, 95 kVp, 4.5 mAs, and 0.3-mm Cu filter. Further technical and clinical studies are needed to verify these preliminary findings.

Highlights

To investigate lateral lumbar spine radiography technical parameters for reduction of effective dose whilst maintaining image quality (IQ)
The highest reported effective dose (ED) for this examination was 1.5 mSv [2,3,4], which is considered a high-radiation exposure, when compared to the average annual background radiation dose of 2 mSv received by the Australian population [5]. This high dose level is mainly related to the exposure settings, considering that examination is performed in one of the body areas that has the highest x-ray attenuation, requiring higher beam energy to penetrate the pelvic bones [3]. The imaging of this anatomical area involves the exposure of radiosensitive reproductive organs [2, 6] and, for that reason, optimisation is critical since there is a potential risk of developing radiation-induced biological
The published literature that identified optimisation in radiography merely analysed the impact of a single-exposure parameter instead of taking into account all of them

Summary

Introduction

To investigate lateral lumbar spine radiography technical parameters for reduction of effective dose whilst maintaining image quality (IQ). The most widely studied exposure parameters identified in the literature were the source-to-detector distance (SDD) [7,8,9], tube voltage (kVp), tube current × exposure time product (mAs) [9, 10], additional beam filtrations [11,12,13], and type of projection (anterior-posterior, posterior-anterior, horizontal beam lateral) [2, 14,15,16,17] These studies showed that a posterior-anterior lumbar spine radiogram was associated with a 65% ED reduction when compared to the anterior-posterior due to the attenuation of primary beam by the iliac bones [15, 16]. Dose optimisation techniques for the routine lateral lumbar spine projection have not been fully explored in the current literature

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