Determination of the effect of metal artifact reduction and hybrid dose reduction reconstruction techniques on effective radiation dose and image quality in the orbital cavity

The orbita is a complex anatomical area consisting of many structures, such as the bulb of the eye and has important functions. Eyeball and especially the lens are affected by exposure to the deterministic effect of radiation. Therefore, in the evaluation of the orbital area with computed tomography, the most optimal image quality should be achieved at the lowest possible radiation dose within the scope of the 'ALARA (as low as reasonably achievable)' principle. This study aimed to investigate the effect and importance of the combined use of adaptive-iterative dose reduction (AIDR) and single-energy metal artefact reduction (SEMAR) computed tomography imaging techniques in the evaluation of the contrast difference in phantom material caused by different densities in the orbital area in the presence of intracranial operative material. In solid phantom material, contrast materials that were hypodense and hyperdense in relation to the phantom ground were placed in the orbital area, and materials that caused metal artifacts were placed in the intracranial area. Images were obtained at 80, 100, 120, and 135 kVp and at the tube current values of 0.6, 1.3, 2.6, 6, 12, and 24.2 mAs, with AIDR and SEMAR in the 'off' mode. Then, the obtained images were reconstructed by turning AIDR and SEMAR on. In addition to dose parameters, such as the dose-length product (DLP), the signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and subjective image quality parameters were evaluated. Subjective evaluation had a significant correlation with the signal data in the 'on' and 'off' AIDR and SEMAR groups. It was determined that the AIDR and SEMAR techniques provided a significant increase in CNR, SNR, and subjective evaluation of hypodense and hyperdense areas. In image evaluation, when AIDR and SEMAR were on, the lowest optimal dose parameters were determined as 100 kVp and 2.6 mAs for the detection of hypodense and hyperdense areas. In conclusion, AIDR and SEMAR were shown to be important techniques that increase image quality and reduce the radiation dose applied to patients during the evaluation of the orbital area in the presence of metal artifacts.