Abstract
BackgroundThe 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.MethodsInstitutional 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.ResultsRespiratory 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).ConclusionsRespiratory 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.
Highlights
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
We evaluated the use of respiratory bellows-compensated PET and navigated hepatobiliary phase imaging in order to address the issues with respiratory motion in liver imaging
Qualitative motion artifact was significantly less in the liver PET compared to the three other PET reconstructions (Table 1, p values ranging from
Summary
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. One of the difficult aspects of simultaneous imaging is how to appropriately leverage prolonged single bed position MR imaging into a whole body PET protocol [1,2,3]. This issue is fairly straightforward for brain and pelvis applications as there is minimal motion associated with the imaging and boils down to MR sequence selection. Unlike conventional PET/CT acquisitions, patients perform numerous breath-holds throughout dedicated liver MR imaging markedly displacing the anatomy throughout the acquisition (Fig. 1) This can result in motion artifacts and errors in quantification. MR sequences are often acquired during inspiratory breathholds, while PET data is predominantly acquired during end expiration
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