Comparison of rigid and deformable coregistration between mpMRI and CT images in radiotherapy of prostate bed cancer recurrence

Marica Masi; Valeria Landoni; Adriana Faiella; Alessia Farneti; Simona Marzi; Maria Guerrisi; Giuseppe Sanguineti

doi:10.1016/j.ejmp.2021.11.010

Comparison of rigid and deformable coregistration between mpMRI and CT images in radiotherapy of prostate bed cancer recurrence

Phys Med. 2021 Nov 27:92:32-39. doi: 10.1016/j.ejmp.2021.11.010. Online ahead of print.

Authors

Marica Masi¹, Valeria Landoni², Adriana Faiella³, Alessia Farneti³, Simona Marzi⁴, Maria Guerrisi⁵, Giuseppe Sanguineti³

Affiliations

¹ Department of Medical Physics, IRCSS Regina Elena National Cancer Institute, Rome, Italy; Department of Biomedicine and Prevention, University of Rome "Tor Vergata", Rome, Italy.
² Department of Medical Physics, IRCSS Regina Elena National Cancer Institute, Rome, Italy. Electronic address: valeria.landoni@ifo.gov.it.
³ Department of Radiation Oncology, IRCSS Regina Elena National Cancer Institute, Rome, Italy.
⁴ Department of Medical Physics, IRCSS Regina Elena National Cancer Institute, Rome, Italy.
⁵ Department of Biomedicine and Prevention, University of Rome "Tor Vergata", Rome, Italy.

PMID: 34847400
DOI: 10.1016/j.ejmp.2021.11.010

Abstract

Purpose: To evaluate the accuracy of rigid coregistration between multiparametric magnetic resonance (mpMR) and computed tomography (CT) images for radiotherapy of prostate bed cancer recurrence.

Materials and method: Fifty-three patients (59 nodules) accrued in a prospective study on salvage radiotherapy for prostatic bed recurrence were suitable for the analysis. Patients underwent a pre radiotherapy mpMR exam and a planning CT in the same treatment position and with control of organ filling. The site of recurrence was delineated on mpMR images and contours transferred on planning CT images using both rigid and deformable registrations. Coregistrations were evaluated by mathematical operators that quantify deformation (Jacobian determinant and vector curl) and similarity indices (Dice and Jaccard coefficients). Dose coverage was evaluated.

Results: Deformable registration did not change volumes, (p = 0.92 MW test). The Jacobian coefficient and the vector curl revealed no important image deformations. Dice and Jaccard coefficients indicated dislocation of the nodule volumes. Dislocation magnitude was d = (5.6 ± 3.1) mm. Organ filling was not correlated with deformation or dislocation. Volumes were covered by the 95% isodose in 96% of cases when rigid registration was performed versus 75% of cases when deformed.

Conclusions: Rigid image coregistration is sufficiently accurate in this setting. The results indicate that the deformable registration tends to shrink the voxels and to dislocate the ROI, the adopted expansion for the recurrence volume adequately accounts for the observed deformation and dislocation, provided that organ filling is controlled.

Keywords: Deformable registration; Personalized treatment; Prostate cancer recurrence; Rigid registration; Salvage radiotherapy.