PET/CT 검사에서 냉소 인공물 발생 시 산란 제한 보정 알고리즘 적용에 따른 영상 평가

• 영문명: A study on evaluation of the image with washed-out artifact after applying scatter limitation correction algorithm in PET/CT exam
• 발행기관: 대한핵의학기술학회
• 저자명: 고현수(Hyun-Soo Ko) 류재광(Jae-kwang Ryu)
• 간행물 정보: 『핵의학기술』Vol.22 No.1, 55~66쪽, 전체 12쪽
• 주제분류: 의약학 > 방사선과학
• 파일형태: PDF
• 발행일자: 2018.05.30

영문 초록

Purpose In PET/CT exam, washed-out artifact could occur due to severe motion of the patient and high specific activity, it results in lowering not only qualitative reading but also quantitative analysis. Scatter limitation correction by GE is an algorism to correct washed-out artifact and recover the images in PET scan. The purpose of this study is to measure the threshold of specific activity which can recovers to original uptake values on the image shown with washed-out artifact from phantom experiment and to compare the quantitative analysis of the clinical patient’s data before and after correction. Materials and Methods PET and CT images were acquired in having no misalignment(D0) and in 1, 2, 3, 4 cm distance of misalignment(D1, D2, D3, D4) respectively, with 20 steps of each specific activity from 20 to 20,000 kBq/ml on ⁶⁸Ge cylinder phantom. Also, we measured the distance of misalignment of foley catheter line between CT and PET images, the specific activity which makes washed-out artifact, SUVₘₑₐₙ of muscle in artifact slice and SUVₘₐₓ of lesion in artifact slice and SUVₘₐₓ of the other lesion out of artifact slice before and after correction respectively from 34 patients who underwent ¹⁸F-FDG Fusion Whole Body PET/CT exam. SPSS 21 was used to analyze the difference in the SUV between before and after scatter limitation correction by paired t-test. Results In phantom experiment, SUVₘₑₐₙ of ⁶⁸Ge cylinder decreased as specific activity of 18F increased. SUVₘₑₐₙ more and more decreased as the distance of misalignment between CT and PET more increased. On the other hand, the effect of correction increased as the distance more increased. From phantom experiments, there was no washed-out artifact below 50 kBq/ml and SUVₘₑₐₙ was same from origin. On D0 and D1, SUVₘₑₐₙ recovered to origin(0.95) below 120 kBq/ml when applying scatter limitation correction. On D2 and D3, SUVₘₑₐₙ recovered to origin below 100 kBq/ml. On D4, SUVₘₑₐₙ recovered to origin below 80 kBq/ml. From 34 clinical patient’s data, the average distance of misalignment was 2.02 cm and the average specific activity which makes washed-out artifact was 490.15 kBq/ml. The average SUVₘₑₐₙ of muscles and the average SUVₘₐₓ of lesions in artifact slice before and after the correction show a significant difference according to a paired t-test respectively(t=-13.805, p=0.000)(t=-2.851, p=0.012), but the average SUVₘₐₓ of lesions out of artifact slice show a no significant difference (t=-1.173, p=0.250). Conclusion Scatter limitation correction algorism by GE PET/CT scanner helps to correct washed-out artifact from motion of a patient or high specific activity and to recover the PET images. When we read the image occurred with washed-out artifact by measuring the distance of misalignment between CT and PET image, specific activity after applying scatter limitation algorism, we can analyze the images more accurately without repeating scan.

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실험 대상 및 방법

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키워드

PET/CT High specific activity Washed-out artifact Scatter limitation algorism