Vol 25, No 1 (2020)
Original research articles
Published online: 2020-01-01

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Comparison of CT artifacts and image recognition of various fiducial markers including two types of thinner fiducial markers for CyberKnife treatment

Toshihiro Suzuki1, Masahide Saito2, Hiroshi Onishi2, Koji Mochizuki1, Kenichiro Satani1, Akihiro Yamazaki3, Kenichi Miura3, Shinji Taka4, Naoki Sano2, Takafumi Komiyama2, Hiroshi Takahashi1
DOI: 10.1016/j.rpor.2019.12.005
Rep Pract Oncol Radiother 2020;25(1):117-124.



The aim of the study was to evaluate computed tomography (CT) artifacts and image recognition of the CyberKnife system. Regarding fiducial markers, VISICOIL of 0.5mm×5.0mm and 0.75mm×5.0mm, ball-shaped Gold Anchor (GA) of 0.28mm×10mm and 0.28mm×20mm, were compared with the standard cylinder marker of 0.9mm×3.0mm (ACCULOC).


Recently, various kinds of commercial fiducial markers have been available in CyberKnife treatment.

Materials and methods

The CT images of a water equivalent gel with each fiducial marker were acquired for the evaluation of CT artifacts. The evaluation was performed using the standard deviation of Hounsfield Unit (HU) value for a rectangle region near the fiducial marker. Then, to evaluate the image recognition, each fiducial marker was located to overlap in the target locating system (TLS) for the two sites; the vertebral bone and the pubic bone.


For CT artifacts, the standard deviations of the VISICOIL of 0.5mm×5.0mm was the smallest. The image recognition of four fiducial markers had a value close to the standard cylinder marker and was feasible for common use, but was slightly poorer when using GA of 0.28mm×10mm in the dynamic conditions.


Our results indicated that VISICOIL 0.5×5.0mm and the GAs can be used nearly always for CyberKnife treatment in spite of their much thinner needles than those of cylinder types.

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Reports of Practical Oncology and Radiotherapy