npsm 새물리 New Physics : Sae Mulli

pISSN 0374-4914 eISSN 2289-0041
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Research Paper

New Phys.: Sae Mulli 2020; 70: 846-850

Published online October 30, 2020 https://doi.org/10.3938/NPSM.70.846

Copyright © New Physics: Sae Mulli.

Performance Evaluation of a Diverging Collimator in a Small Gamma Camera by Hole Type and Arrangement

Dong-Hee HAN1, Jong-Hun WON1, Cheol-Ha BAEK2*

1Department of Health Medical Science, Graduate School, Kangwon National University, Samcheok 25949, Korea

2Department of Radiological Science, Kangwon National University, Samcheok 25949, Korea

Correspondence to:baekch100@gmail.com

Received: July 27, 2020; Revised: August 12, 2020; Accepted: August 15, 2020

Abstract

For overcoming the drawbacks of pinhole collimators, which are used to detect a wide field of view, compact diverging collimators using metal-based precision machining have recently been drawing attention in the 3D printer field. Thus, we evaluated the performances of diverging collimators among the square, circular and hexagonal holes, as well as the arrangements of the GAGG crystals. The GATE code and the STL file were used, as was a $^{99m}$Tc point source. The total area and the height of the collimator were set at 25.8 × 25.8 $mm^2$ and 15 mm respectively. While the spatial resolution for all holes was relatively constant within a low error, the sensitivity for the square holes was 37.3% better than that for circular boles and 52.2% better than that for hexagonal holes, Similar results were obtained when the source was moved to the X-axis. Also, if the arrangement of crystals matched the type of the holes in the collimator, the spatial resolution was slightly better, confirming that the higher the degree of matching the hole, the better the performance.

Keywords: Diverging collimator, GATE, Performance evaluation, 3D printer

최근 3D 프린터에서 금속 재질의 정밀 가공기술을 이용한 소형 확산형 조준기에 대한 연구가 활발히 진행되고 있다. 이에 본 연구에서는 확산형 조준기의 구멍 형태가 사각형, 원형, 육각형일 때와 섬광체의 배열 형태에 따른 민감도와 공간분해능의 차이를 평가하고자 하였다. 이를 위해 몬테카를로 시뮬레이션 도구인 GATE와 STL 파일을 이용하였고, 점선원 $^{99m}$Tc(140 keV)과 조준기의 전체 면적, 높이는 각각 25.8 × 25.8 $mm^2$, 15 mm로 동일하게 설계하였다. 모든 구멍에서 공간분해능은 작은 오차 내 범위로 비교적 일정했던 반면 민감도는 사각형이 원형 대비 37.3%, 육각형 대비 52.2% 우수했으며, 이는 선원이 가장자리로 이동했을 때도 유사하였다. 또한, 섬광체의 배열이 조준기의 구멍 형태와 일치했을 경우 공간분해능은 개선되었고, 이를 통해 조준기의 구멍과 일치되는 정도가 높을수록 성능이 개선됨을 확인하였다.

Keywords: 확산형 조준기, GATE, 성능평가, 3D 프린터

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