Image artifacts caused by incorrect bowtie filters in cone-beam CT image-guided radiotherapy.

Image artifacts caused by incorrect bowtie filters in cone-beam CT image-guided radiotherapy.
J Appl Clin Med Phys. 2020 May 08;:
Authors: Cao Y, Ma T, de Boer SF, Wang IZ
Abstract
Certain models of cone beam computed tomography (CBCT) image-guided radiotherapy (IGRT) systems require manually placing the appropriate bowtie filter according to the relevant imaging protocol. Inadvertently using a wrong bowtie filter or no bowtie filter could cause unexpected image artifacts. In this work, CBCT image artifact patterns caused by different bowtie filter placement were evaluated. CBCT images of CT phantoms, that is, a Body Norm phantom, a Catphan® phantom and an anthropomorphic RANDO® phantom, were acquired at a Varian Trilogy® unit with an On-Board Imager® (OBI) system. Three image acquisition protocols were evaluated. For Standard Head protocol, half-fan bowtie and no bowtie filter were studied for comparison with the correct full-fan bowtie acquisition. For Pelvis and Low-Dose Thorax protocols, full-fan bowtie and no bowtie were studied for comparison with the correct half-fan bowtie acquisition. In addition, the possibility of reversed direction half-fan bowtie was also discussed. All possible scenarios of bowtie filter misplacement caused distinct artifacts regardless of protocols. These artifact patterns are different from the characteristic crescent artifact when correct bowtie filter was placed. Based on the artifact patterns d...

Source: Journal of Applied Clinical Medical Physics - May 7, 2020 Category: Physics Authors: Cao Y, Ma T, de Boer SF, Wang IZ Tags: J Appl Clin Med Phys Source Type: research