Ramon Ortiz

Ramon Ortiz
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Ramon verified their affiliation via an institutional email.
Verified
Ramon verified their affiliation via an institutional email.
University of California, San Francisco | UCSF · Department of Radiation Oncology

Doctor of Philosophy

About

28
Publications
2,539
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178
Citations
Introduction
Postdoctoral researcher at UCSF working on computational nanodosimetry and Monte Carlo simulation codes.

Publications

Publications (28)
Article
Full-text available
The radiobiological mechanisms behind the favorable response of tissues to microbeam radiation therapy (MRT) are not fully described yet. Among other factors, the differential action to tumor and normal tissue vasculature is considered to contribute to MRT efficacy. This computational study evaluates the relevance of tumor growth stage and associat...
Article
Full-text available
Objective. To develop a computational tool that converts biological images into geometries compatible with computational software dedicated to the Monte Carlo simulation of radiation transport (TOPAS), and subsequent biological tissue responses (CompuCell3D). The depiction of individual biological entities from segmentation images is essential in c...
Preprint
Full-text available
Objective: To propose a mathematical model for applying Ionization Detail (ID), the detailed spatial distribution of ionization along a particle track, to proton and ion beam radiotherapy treatment planning (RTP). Approach: Our model provides for selection of preferred ID parameters (I_p) for RTP, that associate closest to biological effects. Clust...
Article
Full-text available
This work aims to develop and validate a framework for the multiscale simulation of the biological response to ionizing radiation in a population of cells forming a tissue. We present TOPAS-Tissue, a framework to allow coupling two Monte Carlo (MC) codes: TOPAS with the TOPAS-nBio extension, capable of handling the track-structure simulation and su...
Article
Purpose The Monte Carlo (MC) method, the gold standard method for radiotherapy dose calculations, is underused in clinical research applications mainly due to computational speed limitations. Another reason is the time-consuming and error prone conversion of treatment plan specifications into MC parameters. To address this issue, we developed an in...
Article
Full-text available
Objective. To present a new set of lithium-ion cross-sections for (i) ionization and excitation processes down to 700 eV, and (ii) charge-exchange processes down to 1 keV u⁻¹. To evaluate the impact of the use of these cross-sections on micro a nano dosimetric quantities in the context of boron neutron capture (BNC) applications/techniques. Approac...
Article
Full-text available
The biology underlying proton minibeam radiation therapy (pMBRT) is not fully understood. Here we aim to elucidate the biological effects of pMBRT using Fourier Transform Infrared Microspectroscopy (FTIRM). In vitro (CTX-TNA2 astrocytes and F98 glioma rat cell lines) and in vivo (healthy and F98-bearing Fischer rats) irradiations were conducted, wi...
Article
Full-text available
Objective. We provide optimal particle split numbers for speeding up TOPAS Monte Carlo simulations of linear accelerator (linac) treatment heads while maintaining accuracy. In addition, we provide a new TOPAS physics module for simulating photoneutron production and transport. Approach. TOPAS simulation of a Siemens Oncor linac was used to determin...
Article
Full-text available
Spatially fractionated radiation therapy (SFRT) is a therapeutic approach with the potential to disrupt the classical paradigms of conventional radiation therapy. The high spatial dose modulation in SFRT activates distinct radiobiological mechanisms which lead to a remarkable increase in normal tissue tolerances. Several decades of clinical use and...
Article
Full-text available
Background Preliminary data have shown a close association of the generalized ionization cluster size dose (in short, cluster dose) with cell survival, independent of particle type, and energy, when cluster dose is derived from an ionization detail parameter preferred for its association with cell survival. Such results suggest cluster dose has the...
Article
Full-text available
Objective: To propose a mathematical model for applying Ionization Detail (ID), the detailed spatial distribution of ionization along a particle track, to proton and ion beam radiotherapy treatment planning (RTP). Approach: Our model provides for selection of preferred ID parameters (Ip) for RTP, that associate closest to biological effects. Clu...
Article
Full-text available
Background: Stereotactic ablative radiotherapy (SABR) and stereotactic radiosurgery (SRS) with conventional photon radiotherapy (XRT) are well-established treatment options for selected patients with oligometastatic/oligorecurrent disease. The use of PBT for SABR-SRS is attractive given the property of a lack of exit dose. The aim of this review i...
Article
Full-text available
Performing accurate and reliable dosimetry in spatially fractionated beams remains a significant challenge due to the steep dose gradients and microscopic scale of features. This results in many conventional detectors and instrumentation being unsuitable for online dosimetry, necessitating frequent offline validation using radiochromic film. In thi...
Article
Full-text available
Background Proton minibeam radiation therapy (pMBRT) is a new radiotherapy approach that has shown a significant increase in the therapeutic window in glioma‐bearing rats compared to conventional proton therapy. Such preclinical results encourage the preparation of clinical trials. Purpose In this study, the potential of pMBRT for treating clinica...
Thesis
Full-text available
In the last decades, radiotherapy has profited from numerous advances allowing a very high dose conformation to the tumor and a reduction in the dose delivered to normal tissues. However, the radio-induced toxicity in normal tissues remains one of the main limiting factors in radiotherapy, compromising the treatment of radioresistant tumors (e.g.,...
Article
Full-text available
Purpose Minibeam radiation therapy (MBRT) is an innovative technique that uses a spatial dose modulation. The dose distribution consists of high doses (peaks) in the path of the minibeam and low doses (valleys). The underlying biological mechanism associated with MBRT efficacy remains currently unclear and thus, we investigated the potential role o...
Article
Full-text available
Purpose Proton minibeam radiation therapy (pMBRT) is a new radiotherapy approach that has shown a significant increase in the therapeutic window in glioma‐bearing rats compared to conventional proton therapy. The dosimetry of pMBRT is challenging and error prone due to the submillimetric beamlet sizes used. The aim of this study was to perform a ro...
Article
Full-text available
Simple Summary Normal tissue’s morbidity continues to limit the increase in the therapeutic index in radiation therapy. This study explores the potential advantages of combining proton arc therapy and proton minibeam radiation therapy, which have already individually shown a significant normal tissue’s sparing. This alliance aims to integrate the b...
Article
Full-text available
(1) Background: Proton minibeam radiation therapy (pMBRT) is a new radiotherapy technique using spatially modulated narrow proton beams. pMBRT results in a significantly reduced local tissue toxicity while maintaining or even increasing the tumor control efficacy as compared to conventional radiotherapy in small animal experiments. In all the exper...

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