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Clinical evaluation of ZTE attenuation correction for brain FDG-PET/MR imaging-comparison with atlas attenuation correction


Sekine, Tetsuro; Ter Voert, Edwin E G W; Warnock, Geoffrey; Buck, Alfred; Huellner, Martin W; Veit-Haibach, Patrick; Delso, Gaspar (2016). Clinical evaluation of ZTE attenuation correction for brain FDG-PET/MR imaging-comparison with atlas attenuation correction. Journal of Nuclear Medicine, 57(12):1927-1932.

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) MR imaging by comparing it 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 (18)F-FDG-PET/CT was acquired. In addition, a head PET/MR scan (GE SIGNA TOF-PET/MR) was performed voluntarily. For each patient, two AC maps were generated from the MR images. One was Atlas-AC, derived from T1-weighted LAVA-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 silver standard. Based on 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 anatomical labeling (AAL), atlas). Relative differences (%diff) and absolute relative differences (|%diff|) between PET images based on each AC were calculated. FDG uptake in all 670 VOIs and generalized merged VOIs were compared using 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 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 to Atlas-AC (ZTE-AC vs. Atlas-AC; 1.77±1.41% vs. 2.44±1.63%, P < 0.01). In two out of seven generalized VOIs, |%diff| on ZTE-AC were 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.

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) MR imaging by comparing it 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 (18)F-FDG-PET/CT was acquired. In addition, a head PET/MR scan (GE SIGNA TOF-PET/MR) was performed voluntarily. For each patient, two AC maps were generated from the MR images. One was Atlas-AC, derived from T1-weighted LAVA-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 silver standard. Based on 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 anatomical labeling (AAL), atlas). Relative differences (%diff) and absolute relative differences (|%diff|) between PET images based on each AC were calculated. FDG uptake in all 670 VOIs and generalized merged VOIs were compared using 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 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 to Atlas-AC (ZTE-AC vs. Atlas-AC; 1.77±1.41% vs. 2.44±1.63%, P < 0.01). In two out of seven generalized VOIs, |%diff| on ZTE-AC were 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.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:04 Faculty of Medicine > University Hospital Zurich > Clinic for Nuclear Medicine
Dewey Decimal Classification:610 Medicine & health
Language:English
Date:23 June 2016
Deposited On:01 Sep 2016 08:51
Last Modified:02 Dec 2016 02:01
Publisher:Society of Nuclear Medicine
ISSN:0161-5505
Free access at:Publisher DOI. An embargo period may apply.
Publisher DOI:https://doi.org/10.2967/jnumed.116.175398
PubMed ID:27339875

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