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Interpolated CT for attenuation correction on respiratory gating cardiac SPECT / CT — A simulation study
Author(s) -
Zhang Duo,
Ghaly Michael,
Mok Greta S. P.
Publication year - 2019
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1002/mp.13513
Subject(s) - nuclear medicine , correction for attenuation , imaging phantom , single photon emission computed tomography , attenuation , physics , medicine , positron emission tomography , optics
Purpose Respiratory gated four‐dimensional (4D) single photon emission computed tomography ( SPECT ) with phase‐matched CT reduces respiratory blurring and attenuation correction ( AC ) artifacts in cardiac SPECT . This study aims to develop and investigate the effectiveness of an interpolated CT ( ICT ) method for improved cardiac SPECT AC using simulations. Methods We used the 4D XCAT phantom to simulate a population of ten patients varied in gender, anatomy, 99m Tc‐sestamibi distribution, respiratory patterns, and disease states. Simulated 120 SPECT projection data were rebinned into six equal count gates. Activity and attenuation maps in each gate were averaged as gated SPECT and CT ( GCT ). Three helical CT s were simulated at end‐inspiration ( HCT ‐ IN ), end‐expiration ( HCT ‐ EX ), and mid‐respiration ( HCT ‐ MID ). The ICT s were obtained from HCT ‐ EX and HCT ‐ IN using the motion vector field generated between them from affine plus b‐spline registration. Projections were reconstructed by OS ‐ EM method, using GCT , ICT , and three HCT s for AC . Reconstructed images of each gate were registered to end‐expiration and averaged to generate the polar plots. Relative difference for each segment and relative defect size were computed using images of GCT AC as reference. Results The average of maximum relative difference through ten phantoms was 7.93 ± 4.71%, 2.50 ± 0.98%, 3.58 ± 0.74%, and 2.14 ± 0.56% for noisy HCT ‐ IN , HCT ‐ MID , HCT ‐ EX , and ICT AC data, respectively. The ICT showed closest defect size to GCT while the differences from HCT s can be over 40%. Conclusion We conclude that the performance of ICT is similar to GCT . It improves the image quality and quantitative accuracy for respiratory‐gated cardiac SPECT as compared to conventional HCT , while it can potentially further reduce the radiation dose of GCT .