Correcting for respiratory motion in liver PET/MRI: preliminary evaluation of the utility of bellows and navigated hepatobiliary phase imaging.
BACKGROUND
The purpose of this study was to evaluate the utility of bellows-based respiratory compensation and navigated hepatobiliary phase imaging to correct for respiratory motion in the setting of dedicated liver PET/MRI.


METHODS
Institutional review board approval and informed consent were obtained. Six patients with metastatic neuroendocrine tumor were imaged using Ga-68 DOTA-TOC PET/MRI. Whole body imaging and a dedicated 15-min liver PET acquisition was performed, in addition to navigated and breath-held hepatobiliary phase (HBP) MRI. Liver PET data was reconstructed three ways: the entire data set (liver PET), gated using respiratory bellows (RC-liver PET), and a non-gated data set reconstructed using the same amount of data used in the RC-liver PET (shortened liver PET). Liver lesions were evaluated using SUVmax, SUVpeak, SUVmean, and Volisocontour. Additionally, the displacement of each lesion between the RC-liver PET images and the navigated and breath-held HBP images was calculated.


RESULTS
Respiratory compensation resulted in a 43 % increase in SUVs compared to ungated data (liver vs RC-liver PET SUVmax 26.0 vs 37.3, p < 0.001) and a 25 % increase compared to a non-gated reconstruction using the same amount of data (RC-liver vs shortened liver PET SUVmax 26.0 vs 32.6, p < 0.001). Lesion displacement was minimized using navigated HBP MRI (1.3 ± 1.0 mm) compared to breath-held HBP MRI (23.3 ± 1.0 mm).


CONCLUSIONS
Respiratory bellows can provide accurate respiratory compensation when imaging liver lesions using PET/MRI, and results in increased SUVs due to a combination of increased image noise and reduced respiratory blurring. Additionally, navigated HBP MRI accurately aligns with respiratory compensated PET data.
Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, CA, USA. thomas.hope@ucsf.edu.|Department of Radiology, San Francisco VA Medical Center, San Francisco, CA, USA. thomas.hope@ucsf.edu.
Thomas A
TA
Hope
Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, CA, USA.
Emily F
EF
Verdin
Division of Hematology/Oncology, Department of Medicine, University of California, San Francisco, San Francisco, CA, USA.
Emily K
EK
Bergsland
Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, CA, USA.|Department of Radiology, San Francisco General Hospital, San Francisco, CA, USA.
Michael A
MA
Ohliger
Division of Surgical Oncology, Department of Surgery, University of California, San Francisco, San Francisco, CA, USA.
Carlos U
CU
Corvera
Division of Surgical Oncology, Department of Surgery, University of California, San Francisco, San Francisco, CA, USA.
Eric K
EK
Nakakura