Dosimetry for quantitative analysis of low dose ionizing radiation effects on humans in radiation therapy patients

We have successfully developed a practical approach to predicting the location of skin surface dose at potential biopsy sites that receive 1 cGy and 10 cGy, respectively, in support of in vivo biologic dosimetry in humans. This represents a significant technical challenge as the sites lie on the patient surface out side the radiation fields. The PEREGRINE Monte Carlo simulation system was used to model radiation dose delivery and TLDs were used for validation on a phantom and confirmation during patient treatment. In the developmental studies the Monte Carlo simulations consistently underestimated the dose at the biopsy site by approximately 15% for a realistic treatment configuration, most likely due to lack of detail in the simulation of the linear accelerator outside the main beam line. Using a single, thickness-independent correction factor for the clinical calculations, the average of 36 measurements for the predicted 1 cGy point was 0.985 cGy (standard deviation: 0.110 cGy) despite patient breathing motion and other real world challenges. Since the 10 cGy point is situated in the region of high dose gradient at the edge of the field, patient motion had a greater effect and the six measured points averaged 5.90 cGy (standard deviation: 1.01 cGy), a difference that is equivalent to approximately a 6 mm shift on the patient's surface

Description and dosimetric verification of the PEREGRINE Monte Carlo dose calculation system for photon beams incident on a water phantom

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/134919/1/mp1551.pd

Source description and sampling techniques in PEREGRINE Monte Carlo calculations of dose distributions for radiation oncology

We outline the techniques used within PEREGRINE, a 3D Monte Carlo code calculation system, to model the photon output from medical accelerators. We discuss the methods used to reduce the phase-space data to a form that is accurately and efficiently sampled

DPM, a fast, accurate Monte Carlo code optimized for photon and electron radiotherapy treatment planning dose calculations

A new Monte Carlo (MC) algorithm, the `dose planning method' (DPM), and its associated computer program for simulating the transport of electrons and photons in radiotherapy class problems employing primary electron beams, is presented. DPM is intended to be a high-accuracy MC alternative to the current generation of treatment planning codes which rely on analytical algorithms based on an approximate solution of the photon/electron Boltzmann transport equation. For primary electron beams, DPM is capable of computing 3D dose distributions (in 1 mm3 voxels) which agree to within 1% in dose maximum with widely used and exhaustively benchmarked general-purpose public-domain MC codes in only a fraction of the CPU time. A representative problem, the simulation of 1 million 10 MeV electrons impinging upon a water phantom of 1283 voxels of 1 mm on a side, can be performed by DPM in roughly 3 min on a modern desktop workstation. DPM achieves this performance by employing transport mechanics and electron multiple scattering distribution functions which have been derived to permit long transport steps (of the order of 5 mm) which can cross heterogeneity boundaries. The underlying algorithm is a `mixed' class simulation scheme, with differential cross sections for hard inelastic collisions and bremsstrahlung events described in an approximate manner to simplify their sampling. The continuous energy loss approximation is employed for energy losses below some predefined thresholds, and photon transport (including Compton, photoelectric absorption and pair production) is simulated in an analogue manner. The δ-scattering method (Woodcock tracking) is adopted to minimize the computational costs of transporting photons across voxels.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/48969/2/m00815.pd

Lawrence Livermore National Laboratory`s PEREGRINE project

PEREGRINE is an all-particle, first-principles 3D Monte Carlo dose calculation system designed to serve as a dose calculation engine for clinical radiation therapy treatment planning (RTP) systems. By taking advantage of recent advances in low cost computer commodity hardware, modern symmetric multiprocessor architectures and state-of- the-art Monte Carlo transport algorithms., PEREGRINE performs high resolution, high accuracy, Monte Carlo RTP calculation in times that are reasonable for clinical use. Because of its speed and simple interface with conventional treatment planning systems, PEREGRINE brings Monte Carlo radiation transport calculations to the clinical RTP desktop environment. Although PEREGRINE is designed to calculate doe distributions for photon, electron, fast neutron and proton therapy, this paper focuses on photon teletherapy

Applying Science and Technology to Combat WMD Terrorism

Lawrence Livermore National Laboratory (LLNL) is developing and fielding advanced strategies that dramatically improve the nation's capabilities to prevent, prepare for, detect, and respond to terrorist use of chemical, biological, radiological, nuclear, and explosive (CBRNE) weapons. The science, technology, and integrated systems we provide are informed by and developed with key partners and end users. LLNL's long-standing role as one of the two principle U.S. nuclear weapons design laboratories has led to significant resident expertise for health effects of exposure to radiation, radiation detection technologies, characterization of radioisotopes, and assessment and response capabilities for terrorist nuclear weapons use. This paper provides brief overviews of a number of technologies developed at LLNL that are being used to address national security needs to confront the growing threats of CBRNE terrorism

PEREGRINE: An all-particle Monte Carlo code for radiation therapy

The goal of radiation therapy is to deliver a lethal dose to the tumor while minimizing the dose to normal tissues. To carry out this task, it is critical to calculate correctly the distribution of dose delivered. Monte Carlo transport methods have the potential to provide more accurate prediction of dose distributions than currently-used methods. PEREGRINE is a new Monte Carlo transport code developed at Lawrence Livermore National Laboratory for the specific purpose of modeling the effects of radiation therapy. PEREGRINE transports neutrons, photons, electrons, positrons, and heavy charged-particles, including protons, deuterons, tritons, helium-3, and alpha particles. This paper describes the PEREGRINE transport code and some preliminary results for clinically relevant materials and radiation sources

Fast Monte Carlo for radiation therapy: the PEREGRINE Project

The purpose of the PEREGRINE program is to bring high-speed, high- accuracy, high-resolution Monte Carlo dose calculations to the desktop in the radiation therapy clinic. PEREGRINE is a three- dimensional Monte Carlo dose calculation system designed specifically for radiation therapy planning. It provides dose distributions from external beams of photons, electrons, neutrons, and protons as well as from brachytherapy sources. Each external radiation source particle passes through collimator jaws and beam modifiers such as blocks, compensators, and wedges that are used to customize the treatment to maximize the dose to the tumor. Absorbed dose is tallied in the patient or phantom as Monte Carlo simulation particles are followed through a Cartesian transport mesh that has been manually specified or determined from a CT scan of the patient. This paper describes PEREGRINE capabilities, results of benchmark comparisons, calculation times and performance, and the significance of Monte Carlo calculations for photon teletherapy. PEREGRINE results show excellent agreement with a comprehensive set of measurements for a wide variety of clinical photon beam geometries, on both homogeneous and heterogeneous test samples or phantoms. PEREGRINE is capable of calculating >350 million histories per hour for a standard clinical treatment plan. This results in a dose distribution with voxel standard deviations of <2% of the maximum dose on 4 million voxels with 1 mm resolution in the CT-slice plane in under 20 minutes. Calculation times include tracking particles through all patient specific beam delivery components as well as the patient. Most importantly, comparison of Monte Carlo dose calculations with currently-used algorithms reveal significantly different dose distributions for a wide variety of treatment sites, due to the complex 3-D effects of missing tissue, tissue heterogeneities, and accurate modeling of the radiation source

SPLENIC VOLUME CHANGE AND THERAPUETIC RESPONSE IN PATIENTS TREATED WITH RADIOMMUNOCONJUGATES SPLENIC VOLUME CHANGE AND THERAPUETIC RESPONSE IN PATIENTS TREATED WITH RADIOIMMUNOCONJUGATES

ABSTRACT Splenomegaly is frequently found in non-Hodgkin&apos;s lymphoma (NHL) patients. This study evaluated the implications of splenic volume change in response to radioimmunotherapy (RIT). Methods: Twenty-nine NHL patients treated with radiolabeled-Lym-1 and 9 breast cancer patients (reference group) treated with radiolabeled-ChL6, BrE-3 or m170 were analyzed using CT splenic images obtained before and after RIT. Patient-specific radiation doses to spleen were determined using actual splenic volume determined by CT and body weight. Results: In 13 of 29 NHL patients who had splenic volume ≤310 ml, there was no or small change (-23 to 15 mL) in splenic volume, despite splenic doses as high as 14.4 Gy. Similarly, in a reference group of 9 breast cancer patients, there was no or small change (-5 to 13 mL), despite splenic doses as high as 11.4 Gy. In contrast, 13 of 29 NHL patients who had splenic volume 380-1400 mL, splenic volume decreased by 68 to 548 mL despite splenic doses as low as 1.40 Gy. Ten of 29 NHL patients with greater than a 15% decrease in splenic volume after RIT had nodal tumor regression (5 CR, 5 PR). In the remaining 19 NHL patients with less than a 15% decrease in splenic volume after RIT, there were 7 non-responders (5 CR and 7 PR). Conclusion: Splenic volume changes were found in NHL patients with splenomegaly. These splenic volume changes is likely due to therapeutic effect on malignant lymphocytes associated with splenomegaly. Nodal tumor response was more likely when splenomegaly decreased after RIT