MRI and FUNDUS image fusion for improved ocular biometry in Ocular Proton Therapy

Riccardo Via; Alessia Pica; Luca Antonioli; Chiara Paganelli; Giovanni Fattori; Chiara Spaccapaniccia; Antony Lomax; Damien Charles Weber; Ann Schalenbourg; Guido Baroni; Jan Hrbacek

doi:10.1016/j.radonc.2022.06.021

MRI and FUNDUS image fusion for improved ocular biometry in Ocular Proton Therapy

Radiother Oncol. 2022 Sep:174:16-22. doi: 10.1016/j.radonc.2022.06.021. Epub 2022 Jul 3.

Affiliations

¹ Paul Scherrer Institut (PSI), Center for Proton Therapy, 5232 Villigen PSI, Switzerland. Electronic address: riccardo.via@psi.ch.
² Paul Scherrer Institut (PSI), Center for Proton Therapy, 5232 Villigen PSI, Switzerland.
³ Dipartimento di Elettronica Informazione e Bioingegneria, Politecnico di Milano, Milano 20133, Italy.
⁴ Paul Scherrer Institut (PSI), Center for Proton Therapy, 5232 Villigen PSI, Switzerland; Department of Radiation Oncology, University Hospital Zurich, Rämistrasse 100, 8091 Zurich, Switzerland; Department of Radiation Oncology, University Hospital Bern, Freiburgstrasse 18, 3010, Bern, Switzerland.
⁵ Department of Ophthalmology, University of Lausanne, Jules-Gonin Eye Hospital, FAA, Lausanne, Switzerland.
⁶ Department of Radiation Oncology, University Hospital Bern, Freiburgstrasse 18, 3010, Bern, Switzerland.

PMID: 35788353
DOI: 10.1016/j.radonc.2022.06.021

Abstract

Introduction: Ocular biometry in Ocular Proton Therapy (OPT) currently relies on a generic geometrical eye model built by referencing surgically implanted markers. An alternative approach based on image fusion of volumetric Magnetic Resonance Imaging (MRI) and panoramic fundus photography was investigated.

Materials and methods: Eighteen non-consecutive uveal melanoma (UM) patients, who consented for an MRI and had their tumour base visible on panoramic fundus photography, were included in this comparative analysis. Through generating digitally-reconstructed projections from MRI images using the Lambert azimuthal equal-area projection, 2D-3D image fusion between fundus photography and an eye model delineated on MRI scans was achieved and allowed for a novel definition of the target base (MRI + F_CTV). MRI + F_CTV was compared with MRI-only delineation (MRI_GTV) and the conventional (EyePlan) target definition (EP_CTV).

Results: The combined use of fundus photography and MRI to define tumour volumes reduced the average discrepancies by almost 65% with respect to the MRI only tumour definitions when comparing with the conventionally planned EP_CTV. With the proposed method, shallow sub-retinal tumour infiltration, otherwise invisible on MRI, can be included in the target volume definition. Moreover, a novel definition of the fovea location improves the accuracy and personalisation of the 3D eye model.

Conclusion: MRI and fundus image fusion overcomes some of the limitations of ophthalmological MRI for tumour volume definition in OPT. This novel eye tumour modelling method might improve treatment planning personalisation, allowing to better anticipate which patients could benefit from prophylactic treatment protocols for radiation induced maculopathy.

Keywords: Magnetic resonance imaging; Multi-modality Image Fusion; Ocular Proton Therapy; Panoramic Fundus Photography; Target Volume Definition.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Biometry
Humans
Imaging, Three-Dimensional / methods
Magnetic Resonance Imaging / methods
Proton Therapy*
Uveal Neoplasms* / diagnostic imaging
Uveal Neoplasms* / radiotherapy