Determination of optimal fiducial marker across image‐guided radiation therapy (IGRT) modalities: visibility and artifact analysis of gold, carbon, and polymer fiducial markers

Abstract

The purpose of this study was to evaluate the visibility and artifact created by gold, carbon, and polymer fiducial markers in a simple phantom across computed tomography (CT), kilovoltage (kV), and megavoltage (MV) linear accelerator imaging and MV tomotherapy imaging. Three types of fiducial markers (gold, carbon, and polymer) were investigated for their visibility and artifacts in images acquired with various modalities and with different imaging parameters (kV, mAs, slice thickness). The imaging modalities include kV CT, 2D linac‐based kilovoltage and megavoltage X‐ray imaging systems, kV cone‐beam CT, and normal and fine tomotherapy imaging. The images were acquired on a phantom constructed using Superflab bolus in which markers of each type were inserted into the center layer. The visibility and artifacts produced by each marker were assessed qualitatively and quantitatively. All tested markers could be identified clearly on the acquired CT and linac‐based kV images; gold markers demonstrated the highest contrast. On the CT images, gold markers produced a significant artifact, while no artifacts were observed with polymer markers. Only gold markers were visible when using linac‐based MV and tomotherapy imaging. For linac‐based kV images, the contrast increased with kV and mAs values for all the markers, with the gold being the most pronounced. On CT images, the contrast increased with kV for the gold markers, while decreasing for the polymer and carbon marker. With the bolus phantom used, we found that when kV imaging‐based treatment verification equipment is available, polymer and carbon markers may be the preferred choice for target localization and patient treatment positioning verification due to less image artifacts. If MV imaging will be the sole modality for positioning verification, it may be necessary to use gold markers despite the artifacts they create on the simulation CT images.PACS number: 87

Qualitative Evaluation of Fiducial Markers for Radiotherapy Imaging

“…Handsfield et al 15 evaluated the visibility and artifacts created by gold, carbon, and polymer fiducial markers across CT, Linac-based kV/MV, and tomotherapy. They suggested polymer and carbon markers for target localization and patient treatment verification for kV imaging-based treatment because of less image artifacts and to use gold markers for position verification for MV imaging, despite the artifacts created on the simulation CT images.…”

AAPM task group 224: Comprehensive proton therapy machine quality assurance

“…67 Appropriate image guidance for routine patient set-up is an essential clinical tool and, as such, the imaging devices must function as expected. 68 Often, fiducial markers are implanted into the target [69][70][71][72][73][74][75][76][77][78] or into structures related to the target position, such as the skull for brain treatment, to assist in alignment.…”

Preclinical investigation for developing injectable fiducial markers using a mixture of BaSO4 and biodegradable polymer for proton therapy

“…Artifacts in the images hinder an accurate delineation of the target, the nearby critical organs, or the marker position itself. 3 In addition, a change in the CT number due to the artifact causes an error in measuring the target and regions of interest density, which reduces the accuracy of the dose calculation in the treatment plan. The shadow caused by the metallic markers in the dose distribution 2 was reported to be of up to 20% in xray therapy 4,5 and of up to 82% in proton therapy, depending on the size and relative location of the gold marker to the beam path.…”