An evaluation of the effect of tube potential on clinical image quality using direct digital detectors for pelvis and lumbar spine radiographs

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

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, FOMSNR, CNR, FOMCNR 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.

How does a non-optimal tube potential influence radiation dose to the patient in lumbar spine radiography?

INTRODUCTION

When comparing the radiation dose to the patient, the lumbar spine has one of the highest dose values in general radiography, therefore the procedure needs to be optimised. The aim of this study was to investigate the effect of a non-optimal tube potential (66 kV) during anteroposterior (AP) lumbar spine radiography on the radiation dose received by the patient compared with the radiation dose when an optimal tube potential (79 kV) is used, in accordance with European guidelines.

METHODS

This retrospective study involved 100 patients referred for lumbar radiography in two different diagnostic departments. Half of the patients were admitted to a department which used optimal tube potential and the other half to the department which used non-optimal tube potential for AP lumbar spine radiography protocols. The height and weight of the patients were collected to calculate the body mass index (BMI) of the patients. The image field size and dose area product (DAP) values were collected after each imaging session. The effective dose and selected organ dose were calculated using the PCXMC 2.0 program.

RESULTS

The results showed that a non-optimal tube potential resulted in a significant increase in the DAP value by 360% (p < 0.001) and a significant increase in the effective dose by 160% (p < 0.001). Dose to selected organs due to non-optimal tube potential increased from 107% (breasts) up to 631% (prostate) (p < 0.001). The images were not assessed using visual grading characteristics (VGC) analysis, but the radiologists evaluated all the images appropriate for diagnostic reading.

CONCLUSION

Based on our study's stated results, we can conclude that optimal tube potential use is essential to achieve the ALARA principle.

IMPLICATIONS FOR PRACTICE

The study shows the effect of a non-optimal tube potential on the radiation dose received by the patient during radiography of the lumbar spine. This could influence possible diagnostic departments to consider protocol optimisation due to the high radiation dose received by the patient.

Contemporary research in digital radiography

Whilst digital radiography (DR) is often seen as the "bread and butter" of medical imaging, there have been considerable advances in technology in the last two decades. Research and education need to move with these new technologies to recognise and take advantage of evolving technologies and optimisation methods that are not constrained by film/screen limitations. Now is an excellent time for radiographers, physicists and students to embark on original and contemporary research into DR.