Abstract
The objective of this study was to evaluate the effect of kilovoltage cone‐beam computed tomography (CBCT) on registration accuracy and image qualities with a reduced number of planar projections used in volumetric imaging reconstruction. The ultimate goal is to evaluate the possibility of reducing the patient dose while maintaining registration accuracy under different projection‐number schemes for various clinical sites. An Elekta Synergy Linear accelerator with an onboard CBCT system was used in this study. The quality of the Elekta XVI cone‐beam three‐dimensional volumetric images reconstructed with a decreasing number of projections was quantitatively evaluated by a Catphan phantom. Subsequently, we tested the registration accuracy of imaging data sets on three rigid anthropomorphic phantoms and three real patient sites under the reduced projection‐number (as low as 1/6th) reconstruction of CBCT data with different rectilinear shifts and rotations. CBCT scan results of the Catphan phantom indicated the CBCT images got noisier when the number of projections was reduced, but their spatial resolution and uniformity were hardly affected. The maximum registration errors under the small amount transformation of the reference CT images were found to be within 0.7 mm translation and 0.3° rotation. However, when the projection number was lower than one‐fourth of the full set with a large amount of transformation of reference CT images, the registration could easily be trapped into local minima solutions for a nonrigid anatomy. We concluded, by using projection‐number reduction strategy under conscientious care, imaging‐guided localization procedure could achieve a lower patient dose without losing the registration accuracy for various clinical sites and situations. A faster scanning time is the main advantage compared to the mA decrease‐based, dose‐reduction method.PACS numbers: 87.57.C‐, 87.57.cf, 87.57.cj, 87.57.cm, 87.57.cp, 87.57.N‐, 87.57.nf, 87.57.nj
Highlights
Advances in three-dimensional (3D) radiation therapy technologies have led to the safe delivery of escalated doses to tumors, improving local control and sparing dose to healthy tissues for improving quality of life.[1]
The availability of large area flat-panel detectors has facilitated the development of integrated cone-beam computed tomography (CBCT) systems on linear accelerators.[4,5,6,7] Until now, kilovoltage CBCT systems integrated into the gantries of linear accelerators have been widely used as an advanced image-guided radiotherapy (IGRT) modality to acquire high-resolution volumetric images of patients for treatment localization purposes
X-ray volume imaging (XVI)-1/6 reconstruction procedures lasted an average of 4.8 seconds over all patients and phantoms, which is about 1/6th of the average time spent for all XVI-full reconstructions
Summary
Advances in three-dimensional (3D) radiation therapy technologies have led to the safe delivery of escalated doses to tumors, improving local control and sparing dose to healthy tissues for improving quality of life.[1] the full potential of these technologies in radiation treatment can be achieved only if the patient can be positioned accurately and reproducibly during every session of the entire course of treatment delivery.[2] Mega-voltage (MV) portal imaging has been widely implemented for the past two decades as patient treatment-positioning tools. Due to the inherent low-contrast and two-dimensional nature of the projection images, the precision of MV portal imaging is limited so far as accurately defining the patient’s position.[3] The need for more precise patient positioning has increased the interest in developing 3D imaging techniques that can verify the patient setup immediately before and after treatment. We wanted to focus on the impact of image information resulting from dose-reduction strategies
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