Uncertainties in ocular proton planning and their impact on required margins.

Wulff, J ; Koska, B ; et al.

In: Physica medica : PM : an international journal devoted to the applications of physics to medicine and biology : official journal of the Italian Association of Biomedical Physics (AIFB), Jg. 121 (2024-05-01), S. 103358

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Purpose: To review required margins in ocular proton therapy (OPT) based on an uncertainty estimation and to compare them with widely used values. Further, uncertainties when using registered funduscopy images in the 3D model is investigated.

Methods: An uncertainty budget in planning and delivery was defined to determine required aperture and range margins. Setup uncertainties were considered for a cohort of treated patients and tested in a worst-case estimation. Other uncertainties were based on a best-guess and knowledge of institutional specifics, e.g. range reproducibility. Margins for funduscopy registration were defined resulting from scaling, rotation and translation of the image. Image formation for a wide-field fundus camera was reviewed and compared to the projection employed in treatment planning systems.

Results: Values for aperture and range with margins of 2.5 mm as reported in literature could be determined. Aperture margins appear appropriate for setup uncertainties below 0.5 mm, but depend on lateral penumbra. Range margins depend on depth and associated density uncertainty in tissue. Registration of funduscopy images may require margins of >2 mm, increasing towards the equator. Difference in the projection may lead to discrepancies of several mm.

Conclusions: The commonly used 2.5 mm aperture margin was validated as an appropriate choice, while range margins could be reduced for lower ranges. Margins may however not include uncertainties in contouring and possible microscopic spread. If a target base is contoured on registered funduscopy images care must be taken as they are subject to larger uncertainties. Multimodal imaging approach in OPT remains advisable.

Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Titel:	Uncertainties in ocular proton planning and their impact on required margins.
Autor/in / Beteiligte Person:	Wulff, J ; Koska, B ; Ahmad Khalil, D ; Richter, R ; Maximilian Bäcker, C ; Bäumer, C ; Foerster, A ; Bechrakis, NE ; Timmermann, B
Zeitschrift:	Physica medica : PM : an international journal devoted to the applications of physics to medicine and biology : official journal of the Italian Association of Biomedical Physics (AIFB), Jg. 121 (2024-05-01), S. 103358
Veröffentlichung:	Pisa : Istituti Editoriali e Poligrafici Internazionali ; <i>Original Publication</i>: Lugano, Switzerland : Giardini editori S.A.,, 2024
Medientyp:	academicJournal
ISSN:	1724-191X (electronic)
DOI:	10.1016/j.ejmp.2024.103358
Schlagwort:	Uncertainty Humans Eye Neoplasms radiotherapy Eye Neoplasms diagnostic imaging Proton Therapy Radiotherapy Planning, Computer-Assisted methods
Sonstiges:	Nachgewiesen in: MEDLINE Sprachen: English Publication Type: Journal Article Language: English [Phys Med] 2024 May; Vol. 121, pp. 103358. <i>Date of Electronic Publication: </i>2024 Apr 20. MeSH Terms: Proton Therapy* ; Radiotherapy Planning, Computer-Assisted* / methods ; Uncertainty ; Humans ; Eye Neoplasms / radiotherapy ; Eye Neoplasms / diagnostic imaging Contributed Indexing: Keywords: Funduscopy; Margins; Proton Therapy Entry Date(s): Date Created: 20240421 Date Completed: 20240510 Latest Revision: 20240510 Update Code: 20240511

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