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. 2019 Dec 26;14(1):237.
doi: 10.1186/s13014-019-1447-1.

Fiducial markers visibility and artefacts in prostate cancer radiotherapy multi-modality imaging

Sarah O S Osman  1   2 , Emily Russell  3 , Raymond B King  4 , Karen Crowther  5 , Suneil Jain  3   6 , Cormac McGrath  7 , Alan R Hounsell  3   4 , Kevin M Prise  3 , Conor K McGarry  3   4
Affiliations

Fiducial markers visibility and artefacts in prostate cancer radiotherapy multi-modality imaging

Sarah O S Osman et al. Radiat Oncol. .

Abstract

Background: In this study, a novel pelvic phantom was developed and used to assess the visibility and presence of artefacts from different types of commercial fiducial markers (FMs) on multi-modality imaging relevant to prostate cancer.

Methods and materials: The phantom was designed with 3D printed hollow cubes in the centre. These cubes were filled with gel to mimic the prostate gland and two parallel PVC rods were used to mimic bones in the pelvic region. Each cube was filled with gelatine and three unique FMs were positioned with a clinically-relevant spatial distribution. The FMs investigated were; Gold Marker (GM) CIVCO, GM RiverPoint, GM Gold Anchor (GA) line and ball shape, and polymer marker (PM) from CIVCO. The phantom was scanned using several imaging modalities typically used to image prostate cancer patients; MRI, CT, CBCT, planar kV-pair, ExacTrac, 6MV, 2.5MV and integrated EPID imaging. The visibility of the markers and any observed artefacts in the phantom were compared to in-vivo scans of prostate cancer patients with FMs.

Results: All GMs were visible in volumetric scans, however, they also had the most visible artefacts on CT and CBCT scans, with the magnitude of artefacts increasing with FM size. PM FMs had the least visible artefacts in volumetric scans but they were not visible on portal images and had poor visibility on lateral kV images. The smallest diameter GMs (GA) were the most difficult GMs to identify on lateral kV images.

Conclusion: The choice between different FMs is also dependent on the adopted IGRT strategy. PM was found to be superior to investigated gold markers in the most commonly used modalities in the management of prostate cancer; CT, CBCT and MRI imaging.

Keywords: Artefacts; Fiducial markers; IGRT; Multi-modality imaging; Pelvic phantom; Prostate Cancer.

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Conflict of interest statement

The authors declare that they have no competing interest.

Figures

Fig. 1
Fig. 1
a 3D printed boxes used to house the gel with or without FMs (b) the complete pelvic phantom being filled with water and setup for scanning on a Varian TrueBeam (c) Pelvic phantom setup on a Siemens Aera 1.5 T MRI scanner. Panels d--f show CT scans of the pelvic phantom (d) transverse view, (e) coronal view showing boxes 1–6 and Head (H) and feet (F) boxes with no FMs, and (f) 3D view of the structures outlined on Varian Eclipse treatment planning system)
Fig. 2
Fig. 2
Transverse CT slice of a representative (a) prostate cancer patient’s pelvis (b) phantom with no FM, (c) and (d) corresponding lateral line profiles for (a) and (b) respectively. e A line profile from a patient with CIVCO GM. f Phantom line profile with CIVCO FM
Fig. 3
Fig. 3
Cross-sectional/planar images of boxes with different FM acquired using different imaging modalities. a–b Volumetric X-ray scans, c MRI scans, and e–i Planar X-ray images. d Different fiducial markers used in this study, diameter x length
Fig. 4
Fig. 4
Prostate gland of three FM on three different patients as they appear on axial slices of CT/CBCT and T2w-MRI. Each patient had 3 fiducial markers. Patient 1 (a) GM CIVCO; routinely used in our institute for IGRT, patient 2 had GM GA (implanted as a ball shape) (b) and patient 3 had a PM polymer markers (c). FM indicated with red arrows on MRI and the orange arrows point to natural calcifications
See this image and copyright information in PMC

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