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Proton Grid Therapy: A Proof-of-Concept Study
Stockholm University, Faculty of Science, Department of Physics.
Stockholm University, Faculty of Science, Department of Physics.ORCID iD: 0000-0002-1099-733X
Stockholm University, Faculty of Science, Department of Physics.
Number of Authors: 42017 (English)In: Technology in Cancer Research and Treatment (Online), ISSN 1533-0346, E-ISSN 1533-0338, Vol. 16, no 6, p. 749-757Article in journal (Refereed) Published
Abstract [en]

In this work, we studied the possibility of merging proton therapy with grid therapy. We hypothesized that patients with larger targets containing solid tumor growth could benefit from being treated with this method, proton grid therapy. We performed treatment planning for 2 patients with abdominal cancer with the suggested proton grid therapy technique. The proton beam arrays were cross-fired over the target volume. Circular or rectangular beam element shapes (building up the beam grids) were evaluated in the planning. An optimization was performed to calculate the fluence from each beam grid element. The optimization objectives were set to create a homogeneous dose inside the target volume with the constraint of maintaining the grid structure of the dose distribution in the surrounding tissue. The proton beam elements constituting the grid remained narrow and parallel down to large depths in the tissue. The calculation results showed that it is possible to produce target doses ranging between 100% and 130% of the prescribed dose by cross-firing beam grids, incident from 4 directions. A sensitivity test showed that a small rotation or translation of one of the used grids, due to setup errors, had only a limited influence on the dose distribution produced in the target, if 4 beam arrays were used for the irradiation. Proton grid therapy is technically feasible at proton therapy centers equipped with spot scanning systems using existing tools. By cross-firing the proton beam grids, a low tissue dose in between the paths of the elemental beams can be maintained down to the vicinity of a deep-seated target. With proton grid therapy, it is possible to produce a dose distribution inside the target volume of similar uniformity as can be created with current clinical methods.

Place, publisher, year, edition, pages
2017. Vol. 16, no 6, p. 749-757
Keywords [en]
proton therapy, grid therapy, proton grid therapy, spatially fractionated beams, treatment planning, new treatment method
National Category
Cancer and Oncology Physical Sciences
Research subject
Medical Radiation Physics
Identifiers
URN: urn:nbn:se:su:diva-152518DOI: 10.1177/1533034616681670ISI: 000418867900011OAI: oai:DiVA.org:su-152518DiVA, id: diva2:1180472
Available from: 2018-02-05 Created: 2018-02-05 Last updated: 2018-09-24Bibliographically approved
In thesis
1. Interlaced proton grid therapy: development of an innovative radiation treatment technique
Open this publication in new window or tab >>Interlaced proton grid therapy: development of an innovative radiation treatment technique
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Spatially fractionated radiotherapy, also known as grid therapy (GRID), has been used for more than a century to try to treat several kinds of lesions. Yet, the grid technique remains a relatively unknown and uncommon treatment modality nowadays. Spatially fractionated beams, instead of conventional homogeneous fields, have been used to exploit the experimental finding that normal tissue can tolerate higher doses when smaller tissue volumes are irradiated. This increase in tolerance with reducing beam size is known as the dose-volume effect. Despite the fact that targets were given inhomogeneous dose distribution, sometimes with some volumes receiving close to no dose, good results in the form of shrinking of bulky tumors have been observed in palliative treatments. The biological processes responsible for this effect are still under discussion, with several possible causes. However, numerous experiments on mice, rats and pigs have confirmed the existence of such effect, which in turn motivates the present development of grid therapy.While mainly photons have been used in grid therapy, proton and ion grid therapies are also emerging as potential alternatives. In this work, an innovative form of grid therapy was proposed. Grids of proton beamlets were interlaced over a target volume with the intention of achieving two main objectives: (1) to keep the grid pattern (made of adjacent high and low doses) from the skin up to the vicinity of the target while (2) delivering nearly homogeneous dose to the target volume. This interlaced proton grid therapy was explored with the use of different beam sizes, from conventional sizes deliverable at modern proton facilities, down to millimeter sized beams. Other considerations that would prevent its clinical use, such as the variable relative biological effectiveness of protons or the use of cone beam computed tomography, were also evaluated. The overall aim was to assess if, and how, such treatment modality could be applied clinically, from a physics and dosimetry point of view. While it presented several theoretical advantages, its potential issues of concern and limitations were also evaluated.

Place, publisher, year, edition, pages
Stockholm: Department of Physics, Stockholm University, 2018. p. 65
Keywords
proton therapy, grid therapy, spatially fractionated therapy, interlacing
National Category
Cancer and Oncology
Research subject
Medical Radiation Physics
Identifiers
urn:nbn:se:su:diva-160427 (URN)978-91-7797-442-0 (ISBN)978-91-7797-443-7 (ISBN)
Public defence
2018-11-09, CCK Lecture Hall, Building R8, Karolinska University Hospital, Solna, Stockholm, 09:00 (English)
Opponent
Supervisors
Available from: 2018-10-17 Created: 2018-09-24 Last updated: 2018-10-16Bibliographically approved

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