Could posterior-anterior projection cervical spine radiographs improve image quality and dose reduction

Introduction: Anterior-posterior (AP) cervical spine X-rays are routine examinations to assess degenerative change, persistent pain and traumatic injuries. Multiple radiosensitive organs lie anteriorly within this anatomical region, increasing the stochastic risk of cancer. If a posterior-anterior (PA) projection was utilised, the radiation dose could potentially be reduced. The hypothesis of this study is to evaluate the change in radiation dose and image quality between AP and PA positions.

Materials and Methods: An anthropomorphic phantom was positioned AP erect against a digital radiography (DR) detector with 30 thermoluminescent dosimeters (TLDs) inserted to record the thyroid, breast, ovaries, and testes absorbed radiation dose at an exposure of 66 kV and 8 mAs. The phantom was repositioned PA erect and repeated. Images were assessed against an image quality criteria Likert scale by qualified radiographers. The mean and standard deviations were calculated for dose and image quality and compared using a t-test and Wilcoxon Signed Ranks Test.

Results: The PA erect cervical spine reduced radiation dose to the right thyroid by 92% (44.7 µGy; p=0.00) and the left thyroid by 89% (43.7 µGy; p=0.00), with further reductions in scatter dose to the breasts (0.35-0.45 µGy; p=0.85), ovaries (0.41 µGy; p=0.57), and testes (0.04 µGy; p=0.98). Image quality scores for the end plates, pedicles, joint spaces, spinous and transverse processes, cortical and trabecular bone patterns, and soft tissues were near equivalent (p=0.32).

Conclusion: Data analysis suggests that PA cervical spine positioning for X-rays in the laboratory adheres to as low as reasonably practicable (ALARP) guidance on X-ray examinations to reduce radiation dose to male and female internal organs (thyroid, breast, ovaries) without a reduction in image quality compared to AP positioning. Further research in clinical practice is advised.

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