The Journal of Korean Society for Radiation Therapy (대한방사선치료학회지)

Korean Society for Radiation Therapy (대한방사선치료학회)
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CT and MRI image fusion reproducibility and dose assessment on Treatment planning system

치료계획시스템에서 전산화단층촬영과 자기공명영상의 영상융합 재현성 및 선량평가

  • Ahn, Byeong Hyeok (Department of Proton Therapy Center, National Cancer Center) ;
  • Choi, Jae Hyeok (Department of Proton Therapy Center, National Cancer Center) ;
  • Hwang, Jae ung (Department of Proton Therapy Center, National Cancer Center) ;
  • Bak, Ji yeon (Department of Proton Therapy Center, National Cancer Center) ;
  • Lee, Du hyeon (Department of Proton Therapy Center, National Cancer Center)
  • 안병혁 (국립암센터 양성자치료센터) ;
  • 최재혁 (국립암센터 양성자치료센터) ;
  • 황재웅 (국립암센터 양성자치료센터) ;
  • 박지연 (국립암센터 양성자치료센터) ;
  • 이두현 (국립암센터 양성자치료센터)
  • Published : 2017.12.29
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Abstract

Objectives: The aim of this study is to evaluate the reproducibility and usefulness of the images through the fusion of CT(Computed tomography) and MRI(Magnetic resonance imaging) using a self-manufactured phantom. We will also compare and analyze the target dose from acquired images. Materials and Methods: Using a self-manufactured phantom, CT images and MRI images are acquired by 1.5T and 3.0T of different magnetic fields. The reproducibility of the size and volume of the small holes present in the phantom is compared through the image from CT and 1.5T and 3.0T MRI, and dose changes are compared and analyzed on any target. Results: 13 small hole diameters were a maximum 31 mm and a minimum 27.54 mm in the CT scan and the were measured within an average of 29.28 mm 1 % compared to actual size. 1.5 T MRI images showed a maximum 31.65 mm and a minimum 24.3 mm, the average is 28.8 mm, which is within 1 %. 3.0T MRI images showed a maximum 30.2 mm and a minimum 27.92 mm, the average is 29.41 mm, which is within 1.3 %. The dose changes in the target were 95.9-102.1 % in CT images, 93.1-101.4 % in CT-1.5T MRI fusion images, and 96-102 % in CT-3.0T MRI fusion images. Conclusion: CT and MRI are applied with different algorithms for image acquisition. Also, since the organs of the human body have different densities, image distortion may occur during image acquisition. Because these inaccurate images description affects the volume range and dose of the target, accurate volume and location of the target can prevent unnecessary doses from being exposed and errors in treatment planning. Therefore, it should be applied to the treatment plan by taking advantage of the image display algorithm possessed by CT and MRI.

목 적: 종양에는 최대한의 선량을 부여하고 주변의 정상조직에는 최소한의 선량이 조사되도록 부작용을 줄이는 목적으로 방사선 치료기술이 발전함에 따라 다양한 치료계획 및 치료 방법이 개발되고 있다. 방사선 치료 시 CT(Computed tomography)와 MRI(Magnetic resonance imaging)영상의 융합은 종양에 선량을 전달하는데 커다란 역할을 한다. 본 연구의 목적은 치료계획 시 자체 제작한 팬톰을 이용하여 CT와 MRI영상들의 융합을 통해 영상의 재현성 및 유용성을 평가하고 획득한 영상에서 타겟 선량을 비교, 분석해보고자 한다. 대상 및 방법: 자체 제작한 팬톰을 이용하여 CT 촬영을 하고, 자장의 세기가 다른 1.5T 와 3.0T의 MRI 촬영을 하여 영상을 획득한다. CT 촬영을 한 팬톰의 영상과 각기 다른 자장의 세기로 촬영한 팬톰의 MRI영상에서 팬톰 내에 존재하는 작은 홀의 크기 및 용적의 재현성을 비교하고, 임의의 타겟에서 선량 변화를 비교, 분석한다. 결 과: 13개의 작은 홀 직경은 CT 촬영에서 최대 31 mm, 최소 27.54 mm를 나타냈으며, 실제 제작한 것과 비교하여 평균 29.28 mm 1 % 이내로 측정되었다. 1.5T MRI 퓨전 영상에서는 최대 31.65 mm, 최소 24.3 mm를 나타냈으며, 평균 28.8 mm 1 % 이내로 측정되었다. 3.0T MRI 퓨전 영상에서는 최대 30.2 mm, 최소 27.92 mm를 나타냈으며, 평균 29.41 mm 1.3 % 이내로 측정되었다. 타겟의 조사된 선량변화는 CT에서 95.9-102.1 %, CT-1.5T MRI 퓨전영상에서 93.1-101.4 %, CT-3.0T MRI 퓨전영상에서는 96-102 %의 선량변화를 보였다. 결 론: CT 및 MRI는 영상획득 시 다른 알고리즘이 적용된다. 또한 인체의 장기는 각기 다른 밀도를 가지고 있으므로 영상 획득 시 이미지 왜곡이 발생할 수 있다. 이러한 부정확한 영상의 묘사는 타겟의 용적범위 및 선량에 영향을 주기 때문에 정확한 타겟의 용적과 위치는 불필요한 선량이 조사되는 것을 방지하며, 치료계획 시 오차를 방지할 수 있다. 즉 CT와 MRI 영상이 가지고 있는 영상 표출 알고리즘의 장점을 이용하여 치료계획에 적용해야 할 것이다.

Keywords

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