Abstract
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Objectives: Respiratory motion producing image blurring degrades the image quality and reduces the quantitative accuracy of PET image. Small animal like mouse or rat has relatively higher breathing rate. The aim of this study was to develop and evaluate a respiratory monitoring system with list-mode acquisition of lung metastasis tumor model. Methods: After an intravenous injection of 18F-FDG through tail vain and 60 min delay for uptake, mouse was placed on an acryl plate with fiducial markers that were made for fusion between small animal PET (microPET R4, Concorde Microsystems, Knoxville TN) and Discovery LS CT images. The duration time of gated scan was 20 min. During acquisition of gated emission scan, respiratory motion was monitored using a commercially available laser optical sensor and trigger-generating device built in-house. The acquired emission list-mode data was sorted to temporally framed sinograms using monitored gating information and reconstructed to four gated images using FORE rebining and 2D-OSEM algorithms without correction of attenuation and scatter. After PET imaging, CT images were acquired by mean of a clinical PET/CT with high-resolution mode (9.6 FOV, 1.25 mm thickness, 80 kV, and 60 mA). All mice were under anesthesia by 2% isofluorane gas and ketamine during PET and CT imaging, respectively. The microPET and CT images were co-registered using the fiducial markers were manually identified in both data sets to perform a point-based rigid co-registration using AMIDE and ASIPro. Results: The observed average breathing rate of mouse was 58.8 ± 23 breaths/min in 2% isofluorane anesthesia. The gated images show the better image quality, compared to that with no gating. Non-gating and gating tumor size were 4.85 and 3.58 mm, respectively. Non-gating and gating tumor mean standard uptake value were 1.62 and 1.77, respectively. This improvement of PET image enhanced the detect ability of small lung metastasis tumor. Conclusions: We developed a monitoring system of small animal respiratory motion and to obtain the information for respiratory motion correction in microPET imaging. This system improves the quantitative accuracy of the tracer, which is distorted by the respiratory motion.
- Society of Nuclear Medicine, Inc.