Radiation dose reduction and image quality enhancement for patients unable to elevate their arms in chest CT: A comparative study

Abstract

Purpose

To propose a method to effectively reduce radiation dose while enhancing image quality in chest CT for patients unable to elevate their arms utilizing the air–gap technique.

Methods

Chest CT images were acquired in three positions: arms raised (control group, position A), arms lowered with the air–gap technique utilizing an in-house device (position B), and arms lowered without the device (position C). Data were categorized by body weight. Radiation dose was assessed using dose-length product (DLP) values, with quantitative analyses of image noise, contrast-to-noise ratio (CNR), and CNR-to-dose ratio (CNRDR). Qualitative assessment utilized a Likert scale.

Results

Average DLP was 473.7 ± 142.9 mGy × cm in position C, with the lowest in position A at 267.3 ± 93.3 mGy × cm. Position B had a DLP of 317.2 ± 121.4 mGy × cm, 18.7 % higher than position A but 33.0 % lower than position C. In patients over 70 kg, all positions exceeded the thoracic CT diagnostic reference level (DRL) (324.2 mGy × cm). For those under 70 kg (i.e., <50 kg, 50–70 kg), position B showed lower DLPs compared to the above DRL. Quantitative analysis indicated that position B maintained image quality similar to position A, with CNRDR of 30.2 ± 11.1 versus 26.6 ± 10.9 in position A, showing marginal significance (p = 0.046). The qualitative evaluation indicated that position A had the highest rating at 4.96, followed by position B at 4.51, and position C at 3.47.

Conclusion

The air–gap device with lowered arms during chest CT for patients unable to elevate their arms can reduce radiation dose while maintaining image quality. A custom-designed device facilitates safe and efficient procedures, especially for patients with higher body weight.