Abstract
ObjectivesRigid image registration (RIR) and deformable image registration (DIR) are widely used in radiotherapy. This project aims to capture current international approaches to image registration.MethodsA survey was designed to identify variations in use, resources, implementation, and decision‐making criteria for clinical image registration. This was distributed to radiotherapy centers internationally in 2018.ResultsThere were 57 responses internationally, from the Americas (46%), Australia/New Zealand (32%), Europe (12%), and Asia (10%). Rigid image registration and DIR were used clinically for computed tomography (CT)‐CT registration (96% and 51%, respectively), followed by CT‐PET (81% and 47%), CT‐CBCT (84% and 19%), CT‐MR (93% and 19%), MR‐MR (49% and 5%), and CT‐US (9% and 0%). Respondent centers performed DIR using dedicated software (75%) and treatment planning systems (29%), with 84% having some form of DIR software. Centers have clinically implemented DIR for atlas‐based segmentation (47%), multi‐modality treatment planning (65%), and dose deformation (63%). The clinical use of DIR for multi‐modality treatment planning and accounting for retreatments was considered to have the highest benefit‐to‐risk ratio (69% and 67%, respectively).ConclusionsThis survey data provides useful insights on where, when, and how image registration has been implemented in radiotherapy centers around the world. DIR is mainly in clinical use for CT‐CT (51%) and CT‐PET (47%) for the head and neck (43–57% over all use cases) region. The highest benefit‐risk ratio for clinical use of DIR was for multi‐modality treatment planning and accounting for retreatments, which also had higher clinical use than for adaptive radiotherapy and atlas‐based segmentation.
Highlights
Medical image registration (IR) enables a user to combine and compare information from multiple images and has applications in radiology,[1] nuclear medicine,[2,3] and radiotherapy.[4,5,6,7] The use of images is increasing in healthcare,[1] and applications of IR can benefit patients in diagnosis, planning, treatment, and response assessment.[1]
On the April 19, 2018, the Australia/New Zealand (ANZ) survey was distributed through emails to Medical Physics Directors, while the INTL survey was distributed through the MEDPHYS email list hosted by Wayne State University.[16]
Results on the number of datasets (xvi), the number of datasets used for commissioning by application (xvii), and patient‐specific QA (xviii) were excluded as there was no ability for respondents to skip questions that were not applicable to them and they were forced to input nominal values to questions
Summary
Medical image registration (IR) enables a user to combine and compare information from multiple images and has applications in radiology,[1] nuclear medicine,[2,3] and radiotherapy.[4,5,6,7] The use of images is increasing in healthcare,[1] and applications of IR can benefit patients in diagnosis, planning, treatment, and response assessment.[1] Almost every software system that uses images in radiotherapy has rigid image registration (RIR) functionalities[4] that involves translational and rotational corrections with up to 6 degrees of freedom. More complex is deformable image registration (DIR) which has 3 degrees of freedom for every voxel in the image.[4] Validation and clinical translation of IR have been considered challenging for over 20 yr,[8] with DIR validation considered an unresolved subject.[5,6]. This report increased awareness in the need for formal quality management to better understand, communicate, and manage the uncertainty of both rigid and deformable image registration. As a single IR technique (RIR or DIR) may not be robust for all circumstances,[10] there is value in data to help select an appropriate IR technique, and data to help decide on a per‐patient IR quality assurance.[4]
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