Evaluation of Sinus/Edge-Corrected Zero-Echo-Time–Based Attenuation Correction in Brain PET/MRI

• Published in: Journal of Nuclear Medicine Vol. 58; no. 11; pp. 1873 - 1879
• Main Authors: Yang, Jaewon, Wiesinger, Florian, Kaushik, Sandeep, Shanbhag, Dattesh, Hope, Thomas A., Larson, Peder E.Z., Seo, Youngho
• Format: Journal Article
• Language: English
• Published: United States Society of Nuclear Medicine 01.11.2017
• Subjects: Adult; Aged; Algorithms; Attenuation; Bone and Bones - diagnostic imaging; Brain; Brain - diagnostic imaging; Cerebellum; Computed tomography; Data acquisition; Edge detection; Female; Fluorodeoxyglucose F18; Humans; Image Processing, Computer-Assisted - methods; Instrumentation; Magnetic resonance imaging; Magnetic Resonance Imaging - methods; Male; Medical imaging; Middle Aged; Multimodal Imaging - methods; Neurology; NMR; Nuclear magnetic resonance; Positron emission; Positron emission tomography; Positron Emission Tomography Computed Tomography - methods; Quantitative analysis; Radiopharmaceuticals; Sinus; Tomography; ZTE; PET/MRI; attenuation correction; brain; PET; neurology
• ISSN: 0161-5505; 1535-5667; 2159-662X; 2159-662X; 1535-5667
• DOI: 10.2967/jnumed.116.188268

In brain PET/MRI, the major challenge of zero-echo-time (ZTE)-based attenuation correction (ZTAC) is the misclassification of air/tissue/bone mixtures or their boundaries. Our study aimed to evaluate a sinus/edge-corrected (SEC) ZTAC (ZTAC ), relative to an uncorrected (UC) ZTAC (ZTAC ) and a CT atlas-based attenuation correction (ATAC). Whole-body F-FDG PET/MRI scans were obtained for 12 patients after PET/CT scans. Only data acquired at a bed station that included the head were used for this study. Using PET data from PET/MRI, we applied ZTAC , ZTAC , ATAC, and reference CT-based attenuation correction (CTAC) to PET attenuation correction. For ZTAC , the bias-corrected and normalized ZTE was converted to pseudo-CT with air (-1,000 HU for ZTE < 0.2), soft-tissue (42 HU for ZTE > 0.75), and bone (-2,000 × [ZTE - 1] + 42 HU for 0.2 ≤ ZTE ≤ 0.75). Afterward, in the pseudo-CT, sinus/edges were automatically estimated as a binary mask through morphologic processing and edge detection. In the binary mask, the overestimated values were rescaled below 42 HU for ZTAC For ATAC, the atlas deformed to MR in-phase was segmented to air, inner air, soft tissue, and continuous bone. For the quantitative evaluation, PET mean uptake values were measured in twenty 1-mL volumes of interest distributed throughout brain tissues. The PET uptake was compared using a paired test. An error histogram was used to show the distribution of voxel-based PET uptake differences. Compared with CTAC, ZTAC achieved the overall PET quantification accuracy (0.2% ± 2.4%, = 0.23) similar to CTAC, in comparison with ZTAC (5.6% ± 3.5%, < 0.01) and ATAC (-0.9% ± 5.0%, = 0.03). Specifically, a substantial improvement with ZTAC (0.6% ± 2.7%, < 0.01) was found in the cerebellum, in comparison with ZTAC (8.1% ± 3.5%, < 0.01) and ATAC (-4.1% ± 4.3%, < 0.01). The histogram of voxel-based uptake differences demonstrated that ZTAC reduced the magnitude and variation of errors substantially, compared with ZTAC and ATAC. ZTAC can provide an accurate PET quantification in brain PET/MRI, comparable to the accuracy achieved by CTAC, particularly in the cerebellum.