RT Journal Article
SR Electronic
T1 Evaluation of Sinus/Edge-Corrected Zero-Echo-Time–Based Attenuation Correction in Brain PET/MRI
JF Journal of Nuclear Medicine
JO J Nucl Med
FD Society of Nuclear Medicine
SP 1873
OP 1879
DO 10.2967/jnumed.116.188268
VO 58
IS 11
A1 Yang, Jaewon
A1 Wiesinger, Florian
A1 Kaushik, Sandeep
A1 Shanbhag, Dattesh
A1 Hope, Thomas A.
A1 Larson, Peder E.Z.
A1 Seo, Youngho
YR 2017
UL http://jnm.snmjournals.org/content/58/11/1873.abstract
AB 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 (ZTACSEC), relative to an uncorrected (UC) ZTAC (ZTACUC) and a CT atlas-based attenuation correction (ATAC). Methods: Whole-body 18F-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 ZTACUC, ZTACSEC, ATAC, and reference CT-based attenuation correction (CTAC) to PET attenuation correction. For ZTACUC, 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 ZTACSEC. 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 t test. An error histogram was used to show the distribution of voxel-based PET uptake differences. Results: Compared with CTAC, ZTACSEC achieved the overall PET quantification accuracy (0.2% ± 2.4%, P = 0.23) similar to CTAC, in comparison with ZTACUC (5.6% ± 3.5%, P < 0.01) and ATAC (−0.9% ± 5.0%, P = 0.03). Specifically, a substantial improvement with ZTACSEC (0.6% ± 2.7%, P < 0.01) was found in the cerebellum, in comparison with ZTACUC (8.1% ± 3.5%, P < 0.01) and ATAC (−4.1% ± 4.3%, P < 0.01). The histogram of voxel-based uptake differences demonstrated that ZTACSEC reduced the magnitude and variation of errors substantially, compared with ZTACUC and ATAC. Conclusion: ZTACSEC can provide an accurate PET quantification in brain PET/MRI, comparable to the accuracy achieved by CTAC, particularly in the cerebellum.