Tetsuro Sekine1,2, Edwin E G W Ter Voert3, Geoffrey Warnock3,4,5, Alfred Buck3, Martin Huellner3,6, Patrick Veit-Haibach3,7, Gaspar Delso8. 1. Department of Nuclear Medicine, University Hospital Zurich, Zurich, Switzerland tetsuro.sekine@gmail.com. 2. Department of Radiology, Nippon Medical School, Tokyo, Japan. 3. Department of Nuclear Medicine, University Hospital Zurich, Zurich, Switzerland. 4. Institute of Pharmacology & Toxicology, University of Zurich, Zurich, Switzerland. 5. PMOD Technologies Ltd., Zurich, Switzerland. 6. Department of Neuroradiology, University Hospital Zurich, Zurich, Switzerland. 7. Division of Diagnostic and Interventional Radiology, Department of Medical Radiology, University Hospital Zurich, Zurich, Switzerland; and. 8. GE Healthcare Waukesha, Wisconsin.
Abstract
Accurate attenuation correction (AC) on PET/MR is still challenging. The purpose of this study was to evaluate the clinical feasibility of AC based on fast zero-echo-time (ZTE) MRI by comparing it with the default atlas-based AC on a clinical PET/MR scanner. METHODS: We recruited 10 patients with malignant diseases not located on the brain. In all patients, a clinically indicated whole-body 18F-FDG PET/CT scan was acquired. In addition, a head PET/MR scan was obtained voluntarily. For each patient, 2 AC maps were generated from the MR images. One was atlas-AC, derived from T1-weighted liver acquisition with volume acceleration flex images (clinical standard). The other was ZTE-AC, derived from proton-density-weighted ZTE images by applying tissue segmentation and assigning continuous attenuation values to the bone. The AC map generated by PET/CT was used as a silver standard. On the basis of each AC map, PET images were reconstructed from identical raw data on the PET/MR scanner. All PET images were normalized to the SPM5 PET template. After that, these images were qualified visually and quantified in 67 volumes of interest (VOIs; automated anatomic labeling, atlas). Relative differences and absolute relative differences between PET images based on each AC were calculated. 18F-FDG uptake in all 670 VOIs and generalized merged VOIs were compared using a paired t test. RESULTS: Qualitative analysis shows that ZTE-AC was robust to patient variability. Nevertheless, misclassification of air and bone in mastoid and nasal areas led to the overestimation of PET in the temporal lobe and cerebellum (%diff of ZTE-AC, 2.46% ± 1.19% and 3.31% ± 1.70%, respectively). The |%diff| of all 670 VOIs on ZTE was improved by approximately 25% compared with atlas-AC (ZTE-AC vs. atlas-AC, 1.77% ± 1.41% vs. 2.44% ± 1.63%, P < 0.01). In 2 of 7 generalized VOIs, |%diff| on ZTE-AC was significantly smaller than atlas-AC (ZTE-AC vs. atlas-AC: insula and cingulate, 1.06% ± 0.67% vs. 2.22% ± 1.10%, P < 0.01; central structure, 1.03% ± 0.99% vs. 2.54% ± 1.20%, P < 0.05). CONCLUSION: The ZTE-AC could provide more accurate AC than clinical atlas-AC by improving the estimation of head-skull attenuation. The misclassification in mastoid and nasal areas must be addressed to prevent the overestimation of PET in regions near the skull base.
Accurate attenuation correction (AC) on PET/MR is still challenging. The purpose of this study was to evaluate the clinical feasibility of AC based on fast zero-echo-time (ZTE) MRI by comparing it with the default atlas-based AC on a clinical PET/MR scanner. METHODS: We recruited 10 patients with malignant diseases not located on the brain. In all patients, a clinically indicated whole-body 18F-FDG PET/CT scan was acquired. In addition, a head PET/MR scan was obtained voluntarily. For each patient, 2 AC maps were generated from the MR images. One was atlas-AC, derived from T1-weighted liver acquisition with volume acceleration flex images (clinical standard). The other was ZTE-AC, derived from proton-density-weighted ZTE images by applying tissue segmentation and assigning continuous attenuation values to the bone. The AC map generated by PET/CT was used as a silver standard. On the basis of each AC map, PET images were reconstructed from identical raw data on the PET/MR scanner. All PET images were normalized to the SPM5 PET template. After that, these images were qualified visually and quantified in 67 volumes of interest (VOIs; automated anatomic labeling, atlas). Relative differences and absolute relative differences between PET images based on each AC were calculated. 18F-FDG uptake in all 670 VOIs and generalized merged VOIs were compared using a paired t test. RESULTS: Qualitative analysis shows that ZTE-AC was robust to patient variability. Nevertheless, misclassification of air and bone in mastoid and nasal areas led to the overestimation of PET in the temporal lobe and cerebellum (%diff of ZTE-AC, 2.46% ± 1.19% and 3.31% ± 1.70%, respectively). The |%diff| of all 670 VOIs on ZTE was improved by approximately 25% compared with atlas-AC (ZTE-AC vs. atlas-AC, 1.77% ± 1.41% vs. 2.44% ± 1.63%, P < 0.01). In 2 of 7 generalized VOIs, |%diff| on ZTE-AC was significantly smaller than atlas-AC (ZTE-AC vs. atlas-AC: insula and cingulate, 1.06% ± 0.67% vs. 2.22% ± 1.10%, P < 0.01; central structure, 1.03% ± 0.99% vs. 2.54% ± 1.20%, P < 0.05). CONCLUSION: The ZTE-AC could provide more accurate AC than clinical atlas-AC by improving the estimation of head-skull attenuation. The misclassification in mastoid and nasal areas must be addressed to prevent the overestimation of PET in regions near the skull base.
Authors: Andrew P Leynes; Jaewon Yang; Florian Wiesinger; Sandeep S Kaushik; Dattesh D Shanbhag; Youngho Seo; Thomas A Hope; Peder E Z Larson Journal: J Nucl Med Date: 2017-10-30 Impact factor: 10.057
Authors: Pengjiang Qian; Yangyang Chen; Jung-Wen Kuo; Yu-Dong Zhang; Yizhang Jiang; Kaifa Zhao; Rose Al Helo; Harry Friel; Atallah Baydoun; Feifei Zhou; Jin Uk Heo; Norbert Avril; Karin Herrmann; Rodney Ellis; Bryan Traughber; Robert S Jones; Shitong Wang; Kuan-Hao Su; Raymond F Muzic Journal: IEEE Trans Med Imaging Date: 2019-08-16 Impact factor: 10.048
Authors: Jaewon Yang; Florian Wiesinger; Sandeep Kaushik; Dattesh Shanbhag; Thomas A Hope; Peder E Z Larson; Youngho Seo Journal: J Nucl Med Date: 2017-05-04 Impact factor: 10.057
Authors: Ahmadreza Rezaei; Georg Schramm; Stefanie M A Willekens; Gaspar Delso; Koen Van Laere; Johan Nuyts Journal: J Nucl Med Date: 2019-04-12 Impact factor: 10.057
Authors: Edwin E G W Ter Voert; Patrick Veit-Haibach; Sangtae Ahn; Florian Wiesinger; M Mehdi Khalighi; Craig S Levin; Andrei H Iagaru; Greg Zaharchuk; Martin Huellner; Gaspar Delso Journal: Eur J Nucl Med Mol Imaging Date: 2017-01-26 Impact factor: 9.236