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Migration Test of Various Fiducial Markers in Tissue

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K Jo

K Jo1*, D Ki2, D Shin3, S Lee4, Y Lim5, (1) National Cancer Center, Goyang-si, Gyeonggi,(2) Hanyang Univ., Ansan, Pyeongchon,

SU-E-J-28 Sunday 3:00PM - 6:00PM Room: Exhibit Hall

Purpose: For guaranteeing the fidelity of patients registration, we measure the migration of various markers and present a criterion to determine the validity of position information of each fiducial marker.

Methods: The migration was tested for various fiducial markers; cylindrical gold marker (35 mg, φ0.9x3 mm), spherical gold marker (φ1.5 mm) and gold particle-based-polymer (GPP) marker (5 mg, φ0.9x3 mm). In order to see the migration effects in tissue, they were inserted into the pork meat by a metallic needle and the meat was fixed in an acrylic box (6x6x8 cm) which is covered with a cup of paraffin. The migration distance of each marker was measured using X-ray radiographs taken before and after rotating the acrylic box.

Results: GPP marker was the lightest among three markers under test, and cylindrical gold marker had the same weight but the larger surface area than spherical gold marker. In the measurement, GPP marker showed the lowest migration (< 0.5 mm). Cylindrical gold marker was migrated more than 2 mm, and spherical gold marker was migrated more than 5mm. The migration distance seems to be related to the ratio of marker mass (centrifugal force) to its surface area (frictional force). In addition, we proposed an index of migration, Dmci to evaluate the amount of marker migration. Dmci is the ratio of i-th marker registration error to total margin. Therefore, marker registration with Dmci<1 is valid for patient setup and guarantees the proper beam delivery.

Conclusion: We compared the migration of various fiducial markers. GPP marker has the smallest amount of migration. The mass and shape of each fiducial marker affects the amount of migration. Also, we proposed an index of migration, Dmci representing which marker was valid for patient setup or not.

Funding Support, Disclosures, and Conflict of Interest: This research was supported by Nuclear Energy Research Infrastructure Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (Grant No. 2012-0005840).

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