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KMID : 0861420120160020068
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Korean Journal of Nuclear Medicine Technology
2012 Volume.16 No. 2 p.68 ~ p.80
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Quantitative Comparisons in 18F-FDG PET Images: PET/MR VS PET/CT
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Lee Mu-Seok
Im Young-Hyun
Kim Jae-Hwan
Choe Gyu-O
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Abstract
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Purpose:More recently, combined PET/MR scanners have been developed in which the MR data can be used for
both anatometabolic image formation and attenuation correction of the PET data. For quantitative PET
information, correction of tissue photon attenuation is mandatory. The attenuation map is obtained from the CT
scan in the PET/CT. In the case of PET/MR, the attenuation map can be calculated from the MR image. The
purpose of this study was to assess the quantitative differences between MR-based and CT-based attenuation
corrected PET images.
Materials and Methods:Using the uniform cylinder phantom of distilled water which has
199.8 MBq of 18F-FDG put into the phantom, we studied the effect of MR-based and CT-based attenuation
corrected PET images, of the PET-CT using time of flight (TOF) and non-TOF iterative reconstruction. The
images were acquired from 60 minutes at 15-minute intervals. Region of interests were drawn over 70% from the
center of the image, and the Scanners’ analysis software tools calculated both maximum and mean SUV. These
data were analyzed by one way-anova test and Bland-Altman analysis. MR images are segmented into three
classes(not including bone), and each class is assigned to each region based on the expected average attenuation
of each region. For clinical diagnostic purpose, PET/MR and PET/CT images were acquired in 23 patients
(Ingenuity TF PET/MR, Gemini TF64). PET/CT scans were performed approximately 33.8 minutes after the
beginnig of the PET/MR scans. Region of interests were drawn over 9 regions of interest(lung, liver, spleen,
bone), and the Scanners’ analysis software tools calculated both maximum and mean SUV. The SUVs from 9
regions of interest in MR-based PET images and in CT-based PET images were compared. These data were
analyzed by paired t test and Bland-Altman analysis.
Results: In phantom study, MR-based attenuation corrected PET images generally showed slightly lower -0.36~-0.15 SUVs than CT-based attenuation corrected PET images (p <0.05). In clinical study, MR-based attenuation corrected PET images generally showed slightly lower SUVs than CT-based attenuation corrected PET images (excepting left middle lung and transverse Lumbar) (p<0.05). And percent differences were -8.0~1.79% lower for the PET/MR images than for the PET/CT images. (excepting lung) Based on the Bland-Altman method, the agreement between the two methods was considered good.
Conclusion: PET/MR confirms generally lower SUVs than PET/CT. But, there were no
difference in the clinical interpretations made by the quantitative comparisons with both type of attenuation map.
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KEYWORD
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PET/MR, PET/CT, SUVs
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FullTexts / Linksout information
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