Daniel E. Wessol

Computational dosimetry and treatment planning for Boron Neutron Capture Therapy

The technology for computational dosimetry and treatment planning for Boron Neutron Capture Therapy (BNCT) has advanced significantly over the past few years. Because of the more complex nature of the problem, the computational methods that work well for treatment planning in photon radiotherapy are not applicable to BNCT. The necessary methods have, however, been developed and have been successfully employed both for research applications as well as human trials, although further improvements in speed are needed for routine clinical applications. Computational geometry for BNCT applications can be constructed directly from tomographic medical imagery and computed radiation dose distributions can be readily displayed in formats that are familiar to the radiotherapy community.

Monte Carlo Treatment Planning for Molecular Targeted Radiotherapy within the MINERVA System

The aim of this project is to extend accurate and patient-specific treatment planning to new treatment modalities, such as molecular targeted radiation therapy, incorporating previously crafted and proven Monte Carlo and deterministic computation methods. A flexible software environment is being created that allows planning radiation treatment for these new modalities and combining different forms of radiation treatment with consideration of biological effects. The system uses common input interfaces, medical image sets for definition of patient geometry and dose reporting protocols. Previously, the Idaho National Engineering and Environmental Laboratory (INEEL), Montana State University (MSU) and Lawrence Livermore National Laboratory (LLNL) had accrued experience in the development and application of Monte Carlo based, three-dimensional, computational dosimetry and treatment planning tools for radiotherapy in several specialized areas. In particular, INEEL and MSU have developed computational dosimetry systems for neutron radiotherapy and neutron capture therapy, while LLNL has developed the PEREGRINE computational system for external beam photon-electron therapy. Building on that experience, the INEEL and MSU are developing the MINERVA (modality inclusive environment for radiotherapeutic variable analysis) software system as a general framework for computational dosimetry and treatment planning for a variety of emerging forms of radiotherapy. In collaboration with this development, LLNL has extended its PEREGRINE code to accommodate internal sources for molecular targeted radiotherapy (MTR), and has interfaced it with the plugin architecture of MINERVA. Results from the extended PEREGRINE code have been compared to published data from other codes, and found to be in general agreement (EGS4-2%, MCNP-10%) (Descalle et al 2003 Cancer Biother. Radiopharm. 18 71-9). The code is currently being benchmarked against experimental data. The interpatient variability of the drug pharmacokinetics in MTR can only be properly accounted for by image-based, patient-specific treatment planning, as has been common in external beam radiation therapy for many years. MINERVA offers 3D Monte Carlo-based MTR treatment planning as its first integrated operational capability. The new MINERVA system will ultimately incorporate capabilities for a comprehensive list of radiation therapies. In progress are modules for external beam photon-electron therapy and boron neutron capture therapy (BNCT). Brachytherapy and proton therapy are planned. Through the open application programming interface (API), other groups can add their own modules and share them with the community.

Physics Design for the Brookhaven Medical Research Reactor Epithermal Neutron Source

A collaborative effort by researchers at the Idaho National Engineering Laboratory and the Brookhaven National Laboratory has resulted in the design and implementation of an epithermal-neutron source at the Brookhaven Medical Research Reactor (BMRR). Large aluminum containers, filled with aluminum oxide tiles and aluminum spacers, were tailored to pre-existing compartments on the animal side of the reactor facility. A layer of cadmium was used to minimize the thermal-neutron component. Additional bismuth was added to the pre-existing bismuth shield to minimize the gamma component of the beam. Lead was also added to reduce gamma streaming around the bismuth. The physics design methods are outlined in this paper. Information available to date shows close agreement between calculated and measured beam parameters. The neutron spectrum is predominantly in the intermediate energy range (0.5 eV - 10 keV). The peak flux intensity is 6.4E + 12 n/(m2.s.MW) at the center of the beam on the outer surface of the final gamma shield. The corresponding neutron current is 3.8E + 12 n/(m2.s.MW). Presently, the core operates at a maximum of 3 MW. The fast-neutron KERMA is 3.6E-15 cGy/(n/m2) and the gamma KERMA is 5.0E-16 cGY/(n/m2) for the unperturbed beam. The neutron intensity falls off rapidly with distance from the outer shield and the thermal flux realized in phantom or tissue is strongly dependent on the beam-delimiter and target geometry.

A stochastic model for high-let response for boron neutron capture therapy (BNCT)

There is evidence showing that there is a significant variation in tumor-boron and blood-boron concentrations for individual patients. There also is a wide variation in the size and location of the tumor. This diversity creates a situation in which treatment must be carefully tailored to the specific needs of each patient. Patient treatment planning will require computer modeling of the various radiation transport and interaction processes expected to occur, coupled with a display of the results in easily interpretable form. Such an analytical evaluation will allow the radiation oncologist to select the beam configuration, specify the irradiation field and positions of local thermal neutron shields, establish the optimum time after boron administration to begin irradiation, and specify the duration of irradiation.

Beyond the Epithermal-Neutron Beam: The Analytical Physicist’s Role

Just four years ago, the epithermal-neutron beam, even a beam of marginal intensity and purity, was just a hope. Today, epithermal-neutron research beams of varying characteristics exist at the Joint Research Center (JRC) near Petten, The Netherlands (Europe), Brookhaven National Laboratory (BNL) (Upton, NY), and Massachusetts Institute of Technology (MIT) (Cambridge, MA). Concepts for modification of existing facilities, or construction of new facilities, exist at several sites worldwide. The challenge for the physicist, at least in the case of reactors, is no longer in providing the neutron source. The challenge now is to support the clinician, the biologist, and the chemist in effective implementation of Neutron Capture Therapy (NCT).

Improvements in Patient Treatment Planning Systems

The Boron Neutron Capture Therapy, Radiation treatment planning environment (BNCT_Rtpe) software system is used to develop treatment planning information’. In typical use BNCT_Rtpe consists of three main components: (1) Semiautomated geometric modeling of objects (brain, target, eyes, sinus) derived from MRI, CT, and other medical imaging modalities, (2) Dose computations for these geometric models with rtt_MC, the INEL Monte Carlo radiation transport computer code, and (3) Dose contouring overlaid on medical images as well as generation of other dose displays. We continue to develop a planning system based on three-dimensional image-based reconstructions using Bspline surfaces. Even though this software is in an experimental state, it has been applied for large animal research and for an isolated case of treatment for a human glioma. Radiation transport is based on Monte Carlo, however there will be implementations of faster methods (e.g. diffusion theory) in the future. The important thing for treatment planning is the output which must convey, to the radiologist, the deposition of dose to healthy and target tissue. Many edits are available such that one can obtain contours registered to medical image, dose/volume histograms and most information required for treatment planning and response assessment. Recent work has been to make the process more automatic and easier to use. The interface, now implemented for contouring and reconstruction, utilizes the Xwindowing system and the MOTIF graphical users interface for effective interaction with the planner. Much work still remains before the tool can be applied in a routine clinical setting.

Dose Calculations Based on Image Reconstructions

Before initiation of human clinical trials of Boron Neutron Capture Therapy (BNCT), there must be a significant amount of confidence in dose prediction. While there is a considerable amount of experience in conventional photon irradiations, as well as a growing base in fast-neutron and charged-particle irradiations, procedures and methods are just being developed and no standards exist for BNCT dose predictions.

SERA: Simulation Environment for Radiotherapy Applications - Users Manual Version 1CO

This document is the user manual for the Simulation Environment for Radiotherapy Applications (SERA) software program developed for boron-neutron capture therapy (BNCT) patient treatment planning by researchers at the Idaho National Engineering and Environmental Laboratory (INEEL) and students and faculty at Montana State University (MSU) Computer Science Department. This manual corresponds to the final release of the program, Version 1C0, developed to run under the RedHat Linux Operating System (version 7.2 or newer) or the Solaris™ Operating System (version 2.6 or newer). SERA is a suite of command line or interactively launched software modules, including graphical, geometric reconstruction, and execution interface modules for developing BNCT treatment plans. The program allows the user to develop geometric models of the patient as derived from Computed Tomography (CT) and Magnetic Resonance Imaging (MRI) images, perform dose computation for these geometric models, and display the computed doses on overlays of the original images as three dimensional representations. This manual provides a guide to the practical use of SERA, but is not an exhaustive treatment of each feature of the code.

The Idaho Power Burst Facility/Boron Neutron Capture Therapy (PBF/BNCT) Program Overview

The Power Burst Facility/Boron Neutron Capture Therapy (PBF/BNCT) Program has been funded since 1988 to evaluate brain treatment using Na2B12H11SH (borocaptate sodium or BSH) and epithermal neutrons. The PBF/BNCT Program pursues this goal as a comprehensive, multidisciplinary, multiorganizational endeavor applying modern program management techniques. The initial focus was to: (1) establish a representative large animal model and (2) develop the generic analytical and measurement capabilities required to control treatment repeatability and determine critical treatment parameters independent of tumor type and body location. This paper will identify the PBF/BNCT Program elements and summarize the status of some of the developed capabilities.