Jonathan B Farr

• Ph.D. D.Sc.
• Managing Director at Applications of Detectors and Accelerators to Medicine

Proton therapy is an expanding radiotherapy modality in the United States and worldwide. With the number of proton therapy centers treating patients increasing, so does the need for consistent, high‐quality clinical commissioning practices. Clinical commissioning encompasses the entire proton therapy system's multiple components, including the trea...

Purpose: Pelvic target dose from intensity-modulated proton therapy (IMPT) is sensitive to patient bowel motion. Robustly optimized plans in regard to bowel filling may improve the dose coverage in the treatment course. Our purpose is to investigate the effect of air volume in large and small bowel and rectum on target dose from IMPT plans. Methods...

Purpose The goal was to develop and test a large diameter parallel plate ionization chamber capable of intercepting at least 98% of the proton beamlets tested with the system. Methods A commercial synchrotron proton therapy system was used for the study (Hitachi, Ltd, Hitachi City, Japan; Model: Probeat‐V). The energies investigated were in the ra...

Purpose: Task Group (TG) 224 was established by the American Association of Physicists in Medicine's Science Council under the Radiation Therapy Committee and Work Group on Particle Beams. The group was charged with developing comprehensive quality assurance (QA) guidelines and recommendations for the three commonly employed proton therapy techniqu...

Particle therapy is rapidly expanding and claiming its position as the treatment modality of choice in teletherapy. However, the rate of expansion continues to be restricted by the size and cost of the associated particle therapy systems and their operation. Additional technical limitations such as dose delivery rate, treatment process efficiency,...

Purpose: To invent, design, construct, and commission an intensity modulated minibeam proton therapy system (IMMPT) without the need for physical collimation and to compare its resulting conformity to a conventional IMPT system. Methods: A proton therapy system (Hitachi, Ltd, Hitachi City, Japan; Model: Probeat-V) was specially modified to produ...

Our recently proposed simplified analytical random walk model (SaRWM) dose calculation algorithm without the nuclear interaction component gives an analytical solution of the proton dose by treating each medium voxel as a proton source. It was validated against Monte Carlo simulation. In this work, we included the nuclear interactions into SaRWM an...

(Abstracted from J Clin Endocrinol Metab 2017;102:2242–2250) Survivors of childhood cancer are at an increased risk of premature ovarian insufficiency (POI) because of the vulnerability of the ovaries to pelvic radiotherapy, alkylating agent chemotherapy, and other gonadotoxic treatment modalities. Although POI can occur early, during, or immediate...

Purpose: Proton dose coverage is sensitive to proton beam range. The current practice of CT number-based registration for patient positioning focuses on matching the target and is not sufficient for proton therapy because the proton range depends on the medium traversed by the beam. Patient body deformations and anatomical changes result in range...

Context: Long-term follow-up data on premature ovarian insufficiency (POI) in childhood cancer survivors are limited. Context: To describe the prevalence of POI, its risk factors and associated long-term adverse health outcomes. Design: Cross-sectional. Setting: The St. Jude Lifetime Cohort Study - established cohort in a tertiary care cente...

The lateral homogeneity assumption is used in most analytical algorithms for proton dose, such as the pencil-beam algorithms and our simplified analytical random walk model. To improve the dose calculation in the distal fall-off region in heterogeneous media, we analyzed primary proton fluence near heterogeneous media and propose to calculate the l...

We propose an analytical random walk model for proton dose calculation in a laterally homogeneous medium. A formula for the spatial fluence distribution of primary protons is derived. The variance of the spatial distribution is in the form of a distance-squared law of the angular distribution. To improve the accuracy of dose calculation in the Brag...

Purpose:To examine the suitability of a Catphan™ 700 phantom for image quality QA of a cone beam computed tomography (CBCT) system deployed for proton therapy. Methods:Catphan phantoms, particularly Catphan™ 504, are commonly used in image quality QA for CBCT. As a newer product, Catphan™ 700 offers more tissue equivalent inserts which may be usefu...

Purpose:Semi-empirical modeling is a powerful computational method in radiation dosimetry. A set of approximations exist for proton ion depth dose distribution (DDD) in water. However, the modeling is more complicated for carbon ions due to fragmentation. This study addresses this by providing and evaluating a new methodology for DDD modeling of ca...

Purpose:This study provides an overview of the design and commissioning of the Monte Carlo (MC) model of the spot-scanning proton therapy nozzle and its implementation for the patient plan simulation. Methods:The Hitachi PROBEAT V scanning nozzle was simulated based on vendor specifications using the TOPAS extension of Geant4 code. FLUKA MC simulat...

Purpose:Dose-weighted linear energy transfer (dLET) has been shown to be useful for the analysis of late effects in proton therapy. This study presents the results of the testing of the dLET concept for intensity modulated proton therapy (IMPT) with a discrete spot scanning beam system without use of an aperture or compensator (AC). Methods:IMPT (n...

Purpose:To describe the design and performance of a ceiling-mounted robotic C-arm CBCT system for image-guided proton therapy. Methods:Uniquely different from traditional C-arm CBCT used in interventional radiology, the imaging system was designed to provide volumetric image guidance for patients treated on a 190-degree proton gantry system and a 6...

Purpose:To study the effect of total-variation based noise reduction algorithms to improve the image registration of low-dose CBCT for patient positioning in radiation therapy. Methods:In low-dose CBCT, the reconstructed image is degraded by excessive quantum noise. In this study, we developed a total-variation based noise reduction algorithm and s...

A new micro-beam scanned proton therapy option and example CNS germ cell tumor treatment planning exercise with improved cognitive sparing Purpose/Objectives To compare potential cognitive and dose sparing using new intensity modulated micro-beam proton therapy (IMμPT) versus intensity-modulated x-ray therapy (IMXT) and conventional intensity modu...

The Poisson or compound Poisson process governs the randomness of photon fluence in cone beam computed tomography (CBCT) imaging systems. The probability density function depends on the mean (noiseless) of the fluence at a certain detector. This dependence indicates the natural requirement of multiscale filters to smooth noise while preserving stru...

Individual QA for IMRT/VMAT plans is required by protocols. Sometimes plans cannot pass the institute's QA criteria. For the Eclipse treatment planning system (TPS) with rounded leaf‐end multileaf collimator (MLC), one practical way to improve the agreement of planned and delivered doses is to tune the value of dosimetric leaf gap (DLG) in the TPS...

One of the more critical initiating events for reproductive cell death is the creation of a DNA double strand break (DSB). In this study, we present a computationally efficient way to determine spatial variations in the relative biological effectiveness (RBE) of proton therapy beams within the FLUKA Monte Carlo (MC) code. We used the independently...

Dose weighted Linear Energy Transfer (LETd) analysis of critical structures may be useful in understanding the side effects of the proton therapy. The objective is to analyze the differences between LETd and dose distributions in brain tumor patients receiving double scattering proton therapy, to quantify LETd variation in critical organs, and to i...

The number of proton therapy centers has increased dramatically over the past decade. Currently, there is no comprehensive set of guidelines that addresses quality assurance (QA) procedures for the different technologies used for proton therapy. The AAPM has charged task group 224 (TG-224) to provide recommendations for QA required for accurate and...

To conduct a failure mode and effects analysis (FMEA) as per AAPM Task Group 100 on clinical processes associated with teletherapy, and the development of mitigations for processes with identified high risk. A FMEA was conducted on clinical processes relating to teletherapy treatment plan development and delivery. Nine major processes were identifi...

To develop a random walk model algorithm for calculating proton dose with balanced computation burden and accuracy. Random walk (RW) model is sometimes referred to as a density Monte Carlo (MC) simulation. In MC proton dose calculation, the use of Gaussian angular distribution of protons due to multiple Coulomb scatter (MCS) is convenient, but in R...

Optimize intensity modulated proton therapy (IMPT) treatment planning guidelines with regard to skin dose reduction in pediatric patients. Phantom and patient CTs were used to evaluate skin dose using a pre-clinical proton beam modeled using Monte Carlo (TOPAS) in a commercial radiotherapy planning system (RTP). Single-spot and single-beam doses we...

To reconstruct phase-space information upstream of patient specific collimators for Monte Carlo simulations using only radiotherapy planning system data. The proton energies are calculated based on residual ranges, e.g., sum of prescribed ranges in a patient and SSD. The Kapchinskij and Vladimirskij (KV) distribution was applied to sample proton's...

The purpose of the current study was to characterize and evaluate intensity-modulated proton grid therapy (IMgPT) using a clinical proton beam. A TOPAS MC model of a new developmental mode (pre-clinical) of the Hitachi proton therapy system (PROBEAT) was used for simulation and characterization of proton grid therapy. TOPAS simulations of different...

External-beam radiation therapy mostly uses high-energy photons (x-rays) produced by medical accelerators, but many facilities now use proton beams, and a few use fast-neutron beams. High-energy photons offer several advantages over lower-energy photons in terms of better dose distributions for deep-seated tumors, lower skin dose, less sensitivity...

This paper describes the design and fabrication of the mouthpiece used for high-dose-rate (HDR) brachytherapy of a cancerous lesion in the soft palate of a pediatric patient. A custom mouth guard made with Thermo-forming material (Clear - Mouthguard) similar to those used by athletes, with a bite section, alveolar sulcus, hard and soft palate secti...

Purpose: To improve image quality of low dose cone beam CT for patient positioning in radiation therapy. Methods: In low dose cone beam CT (CBCT) imaging systems, Poisson process governs the randomness of photon fluence at x-ray source and the detector because of the independent binomial process of photon absorption in medium. On a CBCT projection,...

Purpose: To evaluate the efficiency of multithreaded Geant4 (Geant4-MT, version 10.0) for proton Monte Carlo dose calculations using a high performance computing facility.

Purpose: To characterize with physical measurements the out-of-field dose for flattening filter free (FFF) and IMRT flattened FFF photon beams less than 10 MV from a Siemens Artiste LINAC, field size dependence, thereof, and comparison with the Pinnacle planning system calculation. Methods: Single field plans were developed for 5×5cm^2 and 20×20cm^...

Purpose Here, we report the feasibility and long-term efficacy of a granulomatous slack skin disease (GSSD) treatment with combined high-energy photon and proton beams. Patient and methods A GSSD patient with abdominal disease volume 25×15×2–4 cm deep was recommended for treatment at this institution. In addition to photons and electrons, high-ene...

Newer methods and advances in radiation therapy promise to reduce the risk of complications in children who require irradiation. They have secured the role of radiation therapy in the treatment of a variety of pediatric central nervous system and solid tumors and for young patients enrolled on clinical trials. Proton therapy is the latest advanceme...

Purpose: The purpose of this investigation was to compare and contrast the measured fundamental properties of two new types of modulated proton scanning systems. This provides a basis for clinical expectations based on the scanned beam quality and a benchmark for computational models. Because the relatively small beam and fast scanning gave challe...

Background In a previous report, we compared the conformity of robust intensity-modulated proton therapy (IMPT) plans with that of helical tomotherapy plans for re-irradiations of head and neck carcinomas using a fixed set-up error of 2 mm. Here, we varied the maximum set-up errors between 0 and 5 mm and compared the robust IMPT-plans with planning...

Purpose: The purpose of this investigation was to compare and contrast the fundamental properties of two new types of modulated proton scanning systems. A secondary purpose was to develop and apply new characterization approaches where necessary to do so. Methods: The following performances of the proton scanning systems were investigated: beaml...

Purpose: The purpose of the investigation is two‐fold. To determine clinical use sensitivity of the high and low dose rate modes of flattening filter free (FFF) inverse modulation radiotherapy (IMRT) treatment plans compared to flattened beam plans. Secondly, do the FFF plans have a conformity advantage? Methods: Planning comparisons were performed...

Background To test the hypothesis that the therapeutic ratio of intensity-modulated photon therapy using helical tomotherapy (HT) for retreatment of head and neck carcinomas can be improved by robust intensity-modulated proton therapy (IMPT). Methods Comparative dose planning with robust IMPT was performed for 7 patients retreated with HT. Result...

Solar proton events (SPEs) pose substantial risk for crewmembers on deep space missions. It has been shown that low gravity and ionizing radiation both produce transient anemia and immunodeficiencies. We utilized the C57Bl/6 based hindlimb suspension model to investigate the consequences of hindlimb-unloading induced immune suppression on the sensi...

Double Scattering and Uniform Scanning • Not possible to modulate the dose at the field junction • Hot and cold spots occur even when no setup uncertainties are considered • Multiple plans need to be created to feather the dose at the field junction • Plans are work intensive due to the lack of automatic planning tools to create an acceptable dose...

Proton radiotherapy of the prostate basal or whole seminal vesicles using scattering delivery systems is an effective treatment of prostate cancer that has been evaluated in prospective trials. Meanwhile, the use of pencil beam scanning (PBS) can further reduce the dose in the beam entrance channels and reduce the dose to the normal tissues. Howeve...

The potentials of lung sparing, dose escalation, and the robustness of intensity modulated proton plans (IMPT(robust)), obtained by minimax optimization on multiple scenarios, were studied. IMPT(robust) optimization as described by Fredriksson et al. [23] was evaluated by means of comparative treatment planning using breath hold CT data from 6 non-...

To compare clinically relevant dosimetric characteristics of proton therapy fields produced by two uniform scanning systems that have a number of similar hardware components but employ different techniques of beam spreading. This work compares two technologically distinct systems implementing a method of uniform scanning and layer stacking that has...

This work presents microdosimetric measurements performed at the Midwest Proton Radiotherapy Institute in Bloomington, Indiana, USA. The measurements were done simulating clinical setups with a water phantom and for a variety of stopping targets. The water phantom was irradiated by a proton spread out Bragg peak (SOBP) and by a proton pencil beam....

Natural gadolinium possesses a very high thermal neutron capture (n,γ) cross section whereas, carbon doped aluminium oxide thermoluminescence dosimeters (Al2O3:C), commercially available as TLD-500 are extremely sensitive to gamma rays. Hence, by combining those two unique phenomena we have developed a highly sensitive passive neutron detector. The...

The detector and sensor group of the West German Proton Therapy Centre (WPE) has developed a novel real-time neutron fluence monitor based on tiny, inexpensive, commercially available GaAs-LEDs. The linear detection range for d(14)+Be neutrons was evaluated to be 5.0 × 108–2.0 × 1011 neutron.cm−2. However, this monitor can be used universally for n...

Displacement damage produced by high-energy neutrons in gallium arsenide (GaAs) light emitting diodes (LED) results in the reduction of light output. Based on this principle we have developed a simple, cost effective, neutron detector using commercial off the shelf (COTS) GaAs-LED for the assessment of neutron fluence and KERMA at critical location...

Natural gadolinium possesses a very high thermal neutron capture (n,γ) cross-section on the other hand, carbon-doped aluminium oxide thermoluminescence dosimeters (α-Al2O3:C), available as TLD 500 are extremely responsive to gamma rays. Hence, by combining those two unique phenomena we have developed a highly sensitive passive neutron detector. The...

In light-ion beam dose delivery with the scanning technique the spacing between adjacent spots is an important parameter during treatment planning. In order to study the effect of spot spacing on dose conformity and robustness for single field uniform dose configurations, fundamental geometrical properties of placement of Gaussian beamlets are expl...

Purpose: This study reports on the basic physics acceptance testing results of a pre‐clinical proton discrete pencil beam scanning (PBS) system (sometimes also known as modulated scanning). Methods: The PBS system tested consists of a 230 MeV cyclotron, a continuous range selector and a dedicated scanning nozzle mounted on two instances of a rotati...

International Symposium on Standards, Applications and Quality Assurance in Medical Radiation Dosimetry (IDOS), Vienna, Austria, 9-12 November 2010 Conclusion The out-of-field radiation dose equivalent per proton dose (H/D) evaluated at WPE was compared with the work of other recent investigators in Figure 8 and are summarised in Table 1. H/D was e...

Purpose: To describe the design and initial testing of a large diameter multilayerionization chamber (MLIC) system for water equivalent range measurements of pristine proton fields. Method and Materials: The MLIC uses a large 120 mm physical diameter collecting cross‐section in a stacked vented parallel plate geometry of 180 layers spaced 0.8 mm ap...

Fast neutrons interact with semiconductor materials (electron/hole pairs) dislodging the lattice atoms from their original stable positions, thereby creating vacancies. The combinations of vacancies and interstitials (displaced ion) are known as "Frenkel-pairs" and results in a reduction of light output of an LED (Figures 2a and 2b). The neutron en...

Large area, shallow fields are well suited to proton therapy. However, due to beam production limitations, such volumes typically require multiple matched fields. This is problematic due to the relatively narrow beam penumbra at shallow depths compared to electron and photon beams. Therefore, highly accurate dose planning and delivery is required....

Proton Therapy University Hospital Essen (UHE) and West German Proton Therapy Centre Essen (WPE) located on the UHE campus are among the few hospitals worldwide operating three medical cyclotrons. IBA Cyclone 18/9 p 20 MeV d 10 MeV IBA Proteus 235 p 230 MeV Radio Nuclide & Fast Neutron Beam Production Gantries 1-3 230 MeV Cyclotron Fixed Horizontal...

In proton therapy delivered with range modulated beams, the energy spectrum of protons entering the delivery nozzle can affect the dose uniformity within the target region and the dose gradient around its periphery. For a cyclotron with a fixed extraction energy, a rangeshifter is used to change the energy but this produces increasing energy spread...

Purpose: Clinical proton pencil beam scanning (PBS) systems are now commercially available. These systems can provide beam delivery that results in uniform field dose or intensity modulated proton therapy (IMPT). This study considers the effects of varying PBS transverse dimensions (beam σ using the Gaussian profile) and number of fields on a serie...

Purpose: Locally advanced prostate cancers show a strong dose‐response relation. Intensity modulated proton therapy (IMPT). Small spot size proton pencil beam scanning, has the potential of excellent dose conformality to the target volumes with good normal tissue sparing. However, the effect of patient and organ motion on the dose distribution is m...

Radiation shielding efficacy of West German Proton Therapy Centre Essen (WPE) was validated using deterministic shielding calculation methods.

Calculations of dose per monitor unit (D∕MU) are required in addition to measurements to increase patient safety in the clinical practice of proton radiotherapy. As in conventional photon and electron therapy, the D∕MU depends on several factors. This study focused on obtaining range and modulation dependence factors used in D∕MU calculations for t...

A proton beam delivery system on a gantry with continuous uniform scanning and dose layer stacking at the Midwest Proton Radiotherapy Institute has been commissioned and accepted for clinical use. This paper was motivated by a lack of guidance on the testing and characterization for clinical uniform scanning systems. As such, it describes how these...

Compensator-based proton therapy of lung cancer using an un-gated treatment while allowing the patient to breathe freely requires a compensator design that ensures tumor coverage throughout respiration. Our investigation had two purposes: one is to investigate the dosimetric impact when a composite compensator correction is applied, or is not, and...

The treatment of moving targets is a primary challenge of radiotherapy. Internal margin has been widely used to account for the geometric displacement of moving targets. However, it has not been fully addressed if internal margin is beam specific, rather than purely geometric. A tissue equivalent thorax phantom with a tumor placed in the right lung...