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Quantitative 4D-PET Reconstruction for Small Animal Using 4D-CBCT

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Y Zhong

Y Zhong*, F Kalantari , Y Zhang , J Wang , UT Southwestern Medical Center, Dallas, TX


TH-AB-708-9 (Thursday, August 3, 2017) 7:30 AM - 9:30 AM Room: 708

Purpose: Animal respiratory motion during data acquisition cause artifacts and loss of tempo information in the reconstruction. The purpose of this work is to enhance image quality of small animal 4D-PET using simultaneously reconstructed 4D-CBCT for accurate motion modeling and attenuation correction.

Methods: 4D-CBCT is first reconstructed by a simultaneous motion estimation and image reconstruction (SMEIR) method. SMEIR performs motion-compensated iterative image reconstruction using projections from all respiration phases using the motion model estimated from projections directly using a 2D/3D deformable registration technique. Interphase displacement vector fields (DVF) obtained during SMEIR is used for motion compensated image reconstruction for 4D-PET by MLEM while a matched phase of 4D-CBCT is used for attenuation correction. A digital rat phantom with a tumor insertion was used to generate 3D attenuation and activity images. The respiratory cycle was 10 phases over 1.0 second and the motions were simulated with a diaphragm motion of 2.4mm and an anterior-posterior expansion of 1.6 mm. The PET simulations were conducted using Monte Carlo package GATE and list-mode data were acquired of each respiratory phase. A small animal CBCT imaging system was also simulated and the projections were simulated in the same respiratory phases.

Results: 4D-PET reconstruction reproduced the activity images of tumor and the body. Using motion and attenuation information from 4D-CBCT, the proposed strategy substantially enhanced the quantification of small animal 4D-PET. For the tumor diameters of 4.5, 6.0 and 7.5 mm, the tumor volume errors were 31%, 22% and 20% respectively; they were 51%, 39% and 22% respectively without motion compensation.

Conclusion: 4D-PET quality is enhanced by using the motion model and attenuation map from SMEIR-reconstructed 4D-CBCT, which provides quantitative uptake information for preclinical research.

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