Effects of image distortion and Hounsfield unit variations on radiation treatment plans: An extended field-of-view reconstruction in a large bore CT scanner

Yong-Ki Bae,Semie Hong,Jeong-Woo Lee

doi:10.1038/s41598-020-57422-y

Yong-Ki Bae, Semie Hong + Show 1 more

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https://doi.org/10.1038/s41598-020-57422-y

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Abstract

This study aimed to evaluate the effect of image distortion and Hounsfield unit (HU) variation due to the extended field-of-view (eFOV) of the large-bore (LB) computed tomography (CT) on dose distribution. Both home-made inhomogeneity and breast phantoms were scanned at the geometric center position and four different offset positions. We also performed dose optimizations based on different breast phantom CT sets for evaluating the effects of image artifacts on the intensity-modulated radiation techniques. The volume changes were 0.0% to 0.5% in the air, −0.5% to 3.0% in the water, and 4.0% to 5.0% in the high-density material of the inhomogeneity phantom. Both phantoms scanning results indicate that more distortions occurred in the eFOV area due to the biased scanning center. The gamma index differences ranged from 0.87% to 4.87% for the FIF plan and from 0.52% to 6.26% for the VMAT plan. This resulted in decrease of the minimum (7.3–13.1%), maximum (−0.8–2.2%), and mean doses (−0.2–4.4%). We recommend that it should be evaluated whether the applied CT would have an appropriate eFOV range for clinical radiation treatment planning for patients.

Highlights

This study aimed to evaluate the effect of image distortion and Hounsfield unit (HU) variation due to the extended field-of-view of the large-bore (LB) computed tomography (CT) on dose distribution
There were greater differences in the high-density material than in the air and water and in the Off-30 cm than in the Off-20 cm. These results indicate that the reconstructed volumes could be affected by its locations and densities in the vicinity of the range between an scan field-of-view (sFOV) of 75 cm and an extended field-of-view (eFOV) of 85 cm diameters
Al. showed similar results regarding the dosimetric impacts of image artifacts from wide-bore CT, but there were some differences between 3D conformal radiation therapy (3D-CRT) and Volumetric Modulated Arc Therapy (VMAT) plans

Summary

Introduction

This study aimed to evaluate the effect of image distortion and Hounsfield unit (HU) variation due to the extended field-of-view (eFOV) of the large-bore (LB) computed tomography (CT) on dose distribution. Both home-made inhomogeneity and breast phantoms were scanned at the geometric center position and four different offset positions. If the treated lesions are located laterally with respect to the center of the body, such as breast cancer lesions, the treatment area could be close to the edge of or outside the sFOV In such cases, the eFOV algorithm could make image distortion and HU errors due to the partial sampling of the scanning data between the diameter of the sFOV and that of the eFOV7. Within the range of the sFOV, incomplete data provided by the eFOV could result in image distortion or undesirable HU variation[8,9]

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