PT  - JOURNAL ARTICLE
AU  - Ruoqiao Zhang
AU  - Dženan Zukić
AU  - Darrin Byrd
AU  - Andinet Enquobahrie
AU  - Adam Alessio
AU  - Filip Banovac
AU  - Kevin Cleary
AU  - Paul Kinahan
TI  - A deformable registration workflow for motion correction in PET-CT guided biopsy
DP  - 2017 May 01
TA  - Journal of Nuclear Medicine
PG  - 1311--1311
VI  - 58
IP  - supplement 1
4099  - http://jnm.snmjournals.org/content/58/supplement_1/1311.short
4100  - http://jnm.snmjournals.org/content/58/supplement_1/1311.full
SO  - J Nucl Med2017 May 01; 58
AB  - 1311Objectives: Biopsy is commonly used to confirm cancer diagnosis when radiologically indicated. Given the ability of PET to localize malignancies in heterogeneous tumors and tumors that do not have a CT correlate, PET/CT guided biopsy may improve the diagnostic yield of biopsies. However, due to the physics of image acquisition, PET-CT images are susceptible to problems due to respiratory motion, leading to inaccurate tumor localization, shape distortion, and incorrect attenuation correction. Due to the wide variability of intra-patient respiratory motion patterns, traditional short-duration cine CT used in respiratory gated PET/CT may be insufficient to match the PET scan data, resulting in suboptimal attenuation correction that eventually compromises the PET quantitative accuracy.Methods: To facilitate PET/CT guided needle biopsy, we developed a workflow that allows us to bring PET image guidance into the interventional CT suite while accounting for respiratory motion. This method relies on respiratory gated CT images aligned using deformable registration that are then applied to the phase-matched attenuation-corrected PET images. We evaluated two deformable registration algorithms and two optimization approaches for registering respiratory gated CT-only images obtained from 7 patients with 10 CT images over the respiratory cycle. Metrics used were RMSE and Dice coefficients. Preliminary testing of the chosen approach was done on an anthropomorphic phantom with respiratory motion using a biopsy needle with an electromagnetically tracked sensor in its tip. The phantom contained a FDG-filled circular vial as a target. These methods are then applied to hybrid simulated respiratory gated CT and PET images using respiratory tracking information from 11 additional clinical PET/CT scans to evaluate the benefit of extended-duration CT to improve the phase-matching for PET attenuation-correction. We evaluate the performance of different methods by calculating the root-mean-square-error values between phase-gated cine CT images and corresponding phase-gated PET attenuation image.Results: Our results show that overall the BSpline registration algorithm with the reference optimization approach gave the best results for deformable registration of respiratory-gated CT images. With the phantom study the image registration (CT to interventional CT) had an RMSE of 1.72 mm. The hybrid simulation-experimental results show that the long-duration cine CT reduces the error of mismatch between PET and CT images compared to the standard short-duration cine CT.Conclusion: The entire workflow has been tested using simulations, phantoms with respiratory motion, and retrospective respiratory gated CT images. The improvement on motion matching between PET and CT by extending the cine duration depends on the patient, with potentially greater benefits for patients with irregular breathing patterns or larger diaphragm movements. A software framework for operation using open source software libraries was also developed and tested. Research Support: R42CA153488, R01CA160253