Radiation dose reduction and image quality evaluation for lateral lumbar spine projection

Abstract

Purpose: Optimization studies in digital radiology help to reduce the radiological risk to patients and maximize the benefits associated with their clinical purpose. The aim of this study was to assess the optimization of lateral lumbar spine projection via a combination of exposure parameters adjustments and additional filtration using a sectional anthropomorphic phantom.

Materials and methods: We evaluated the effects of peak voltage, tube loading, and low-cost filters made of copper, titanium, brass, and nickel on both the perceived and physical quality of 125 radiographs obtained in a computer radiography system. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) with their Figure of Merit (FOM), based on the entrance surface air kerma with backscatter (ESAK), was used to assess physical image quality.

Results: The standard image had a perceived image quality, SNR, FOM_SNR, CNR, FOM_CNR and ESAK of 3.4, 22.3, 386.4, 23.6, 433.7 and 1.28 mGy, respectively. Copper (90.3% purity) and titanium (95.0% purity) filters reduced ESAK by an average of 60% without compromising diagnostic quality, while brass and nickel filters increased dose under the conditions of the study.

Conclusions: Our findings show that optimizing lumbar spine projection can reduce radiation dose without compromising image quality. Low-cost copper and titanium filters can be valuable in resource-limited settings. Further research can explore additional strategies for radiological optimization.

Keywords: Digital radiology; Dosimetry; Image quality; Optimization.

Fig. 1

Radiograph of the lateral projection of the lumbar spine. (A) Experimental setup for obtaining radiographs of the lateral lumbar spine. (B) Anatomical points considered in the perceived image quality (1, spinous process; 2, pedicles and transverse processes; 3, upper and lower vertebral plates; and 4, intervertebral disks). (C) Regions of interest (ROI) used to assess the physical image quality using ImageJ software.

Fig. 2

Characterization of the filter materials used to optimize the lateral projection of the lumbar spine: copper (A, B, C), titanium (D, E, F), brass (G, H, I) and nickel (J, K, L)). (A, D, G, J) Scanning electron micrograph of surface topography (1000 × magnification). (B, E, H, K) Energy-dispersive X-ray spectroscopy pattern of the elemental composition of the filter. (C, F, I, L) Mass attenuation coefficient versus effective energy for each material. R², coefficient of determination.

Fig. 3

Perceived image quality in terms of entrance surface air kerma (ESAK) for lateral lumbar spine projection (A) without additional filtration, and with additional filters of (B) copper, (C) titanium, (D) brass and (E) nickel. r, Pearson correlation coefficient (95% confidence interval); ICC, intraclass coefficient correlation between observers (95% confidence interval). (F) Mean value ± standard deviation of the perceived image quality for each filter condition. * p < 0.05; ****p < 0.0001.

Fig. 4

Physical image quality in terms of entrance surface air kerma (ESAK) for the lateral lumbar spine (A) without additional filtration and with additional filters of (B) copper, (C) titanium, (D) brass and (E) nickel. (F) Signal-to-noise ratio (SNR) for each condition, (G) Figure of Merit of SNR (FOM_SNR), (H) Contrast-to-noise ratio (CNR) and (I) Figure of Merit of CNR (FOM_CNR). Data are expressed as mean ± standard deviation. ****p < 0.0001.