Feasibility and potential clinical benefit of dose de-escalation in stereotactic ablative radiotherapy for lung cancer lesions with ground glass opacities.

Introduction: Treatment of neoplasic lung nodules with ground glass opacities (GGO) faces two primary challenges. First, the standard practice of treating GGOs as solid nodules, which effectively controls the tumor locally, but might increase associated toxicities. The second is the potential for dose calculation errors related to increased heterogeneity.

ESTRO-EPTN radiation dosimetry guidelines for the acquisition of proton pencil beam modelling data.

Proton therapy (PT) is an advancing radiotherapy modality increasingly integrated into clinical settings, transitioning from research facilities to hospital environments. A critical aspect of the commissioning of a proton pencil beam scanning delivery system is the acquisition of experimental beam data for accurate beam modelling within the treatment planning system (TPS). These guidelines describe in detail the acquisition of proton pencil beam modelling data.

Monte Carlo calculated ionization chamber correction factors in clinical proton beams - deriving uncertainties from published data.

For the update of the IAEA TRS-398 Code of Practice (CoP), global ionization chamber factors (f) and beam quality correction factors (k) for air-filled ionization chambers in clinical proton beams have been calculated with different Monte Carlo codes. In this study, average Monte Carlo calculated f and k factors are provided and the uncertainty of these factors is estimated. Average f factors in monoenergetic proton beams with energies between 60 MeV and 250 MeV were derived from Monte Carlo calculated f factors published in the literature.

Consensus guide on CT-based prediction of stopping-power ratio using a Hounsfield look-up table for proton therapy.

Background And Purpose: Studies have shown large variations in stopping-power ratio (SPR) prediction from computed tomography (CT) across European proton centres. To standardise this process, a step-by-step guide on specifying a Hounsfield look-up table (HLUT) is presented here.

Materials And Methods: The HLUT specification process is divided into six steps: Phantom setup, CT acquisition, CT number extraction, SPR determination, HLUT specification, and HLUT validation.

Biological equivalent dose is associated with radiological toxicity after lung stereotactic ablative radiation therapy.

Introduction: Stereotactic ablative radiation therapy (SABR) is the standard of care for inoperable early-stage non-small-cell lung cancer. Although the probability of grade ≥ II toxicities is low, many patients present radiological subclinical toxicities usually associated with long-term patient management challenges. We evaluated radiological changes and correlated them with the received Biological Equivalent Dose (BED).

Comment on 'Lateral response heterogeneity of Bragg peak ionization chambers for narrow-beam photon and proton dosimetry'.

Kuess(2017206-27) irradiated several PTW 34070 ionization chambers with a narrow x-ray beam impinging at different positions of the detector entrance window and they observed that the reading of the ionization chambers decreased as the impact point of the beam approached the edge of the sensitive volume. They concluded that the radial response of the detector decreased with increasing radius and they proposed a correction factor to correct for that effect. This work shows, by means of a simple Monte Carlo simulation, that the conclusions of Kuess and co-workers do not seem to be supported by their experimental findings-quite the opposite, their experimental results seem to be compatible with a rather homogeneous radial response of the PTW 34070.

Experimental assessment of inter-centre variation in stopping-power and range prediction in particle therapy.

Purpose: Experimental assessment of inter-centre variation and absolute accuracy of stopping-power-ratio (SPR) prediction within 17 particle therapy centres of the European Particle Therapy Network.

Material And Methods: A head and body phantom with seventeen tissue-equivalent materials were scanned consecutively at the participating centres using their individual clinical CT scan protocol and translated into SPR with their in-house CT-number-to-SPR conversion. Inter-centre variation and absolute accuracy in SPR prediction were quantified for three tissue groups: lung, soft tissues and bones.

Monte Carlo calculation of beam quality correction factors in proton beams using PENH.

This work calculates beam quality correction factors ([Formula: see text]) in both modulated and unmodulated proton beams using the Monte Carlo (MC) code [Formula: see text]. The latest ICRU 90 recommendations on key data for ionizing-radiation dosimetry were adopted to calculate the electronic stopping powers and to select the mean energy to create an ion pair in dry air ([Formula: see text]). For modulated proton beams, [Formula: see text] factors were calculated in the middle of a spread-out Bragg peak, while for monoenergetic proton beams they were calculated at the entrance region.

Comparison of penh, fluka, and Geant4/topas for absorbed dose calculations in air cavities representing ionization chambers in high-energy photon and proton beams.

Purpose: The purpose of this work is to analyze whether the Monte Carlo codes penh, fluka, and geant4/topas are suitable to calculate absorbed doses and ratios in therapeutic high-energy photon and proton beams.

Methods: We used penh, fluka, geant4/topas, and egsnrc to calculate the absorbed dose to water in a reference water cavity and the absorbed dose to air in two air cavities representative of a plane-parallel and a cylindrical ionization chamber in a 1.25 MeV photon beam and a 150 MeV proton beam - egsnrc was only used for the photon beam calculations.

Revisiting the single-energy CT calibration for proton therapy treatment planning: a critical look at the stoichiometric method.

Despite extensive research in dual-energy computed tomography (CT), single-energy CT (SECT) is still the standard imaging modality in proton therapy treatment planning and, in this context, the stoichiometric calibration method is considered to be the most accurate to establish a relationship between CT numbers and proton stopping power. This work revisits the SECT calibration for proton therapy treatment planning, with special emphasis on the stoichiometric method. Three different sets of tissue-substitutes of known elemental composition (Gammex, CIRS and Catphan) were scanned with the same scanning protocol.

Reference dosimetry of proton pencil beams based on dose-area product: a proof of concept.

This paper describes a novel approach to the reference dosimetry of proton pencil beams based on dose-area product ([Formula: see text]). It depicts the calibration of a large-diameter plane-parallel ionization chamber in terms of dose-area product in a Co beam, the Monte Carlo calculation of beam quality correction factors-in terms of dose-area product-in proton beams, the Monte Carlo calculation of nuclear halo correction factors, and the experimental determination of [Formula: see text] of a single proton pencil beam. This new approach to reference dosimetry proves to be feasible, as it yields [Formula: see text] values in agreement with the standard and well-established approach of determining the absorbed dose to water at the centre of a broad homogeneous field generated by the superposition of regularly-spaced proton pencil beams.

Reply to comment on 'Proton beam monitor chamber calibration'.

This reply shows that the discrepancy of about 3% between Faraday cup dosimetry and reference dosimetry using a cylindrical ionization chamber found in Gomà (2014 Phys. Med. Biol.

Monte Carlo calculation of beam quality correction factors in proton beams using detailed simulation of ionization chambers.

This work calculates beam quality correction factors (kQ) in monoenergetic proton beams using detailed Monte Carlo simulation of ionization chambers. It uses the Monte Carlo code penh and the electronic stopping powers resulting from the adoption of two different sets of mean excitation energy values for water and graphite: (i) the currently ICRU 37 and ICRU 49 recommended Iw = 75 eV and Ig = 78 eV and (ii) the recently proposed Iw = 78 eV and Ig = 81.1 eV.

The role of a microDiamond detector in the dosimetry of proton pencil beams.

In this work, the performance of a microDiamond detector in a scanned proton beam is studied and its potential role in the dosimetric characterization of proton pencil beams is assessed. The linearity of the detector response with the absorbed dose and the dependence on the dose-rate were tested. The depth-dose curve and the lateral dose profiles of a proton pencil beam were measured and compared to reference data.

Experimental validation of beam quality correction factors for proton beams.

This paper presents a method to experimentally validate the beam quality correction factors (kQ) tabulated in IAEA TRS-398 for proton beams and to determine the kQ of non-tabulated ionization chambers (based on the already tabulated values). The method is based exclusively on ionometry and it consists in comparing the reading of two ionization chambers under the same reference conditions in a proton beam quality Q and a reference beam quality (60)Co. This allows one to experimentally determine the ratio between the kQ of the two ionization chambers.

Intensity modulated proton therapy for postmastectomy radiation of bilateral implant reconstructed breasts: a treatment planning study.

Background And Purpose: Delivery of post-mastectomy radiation (PMRT) in women with bilateral implants represents a technical challenge, particularly when attempting to cover regional lymph nodes. Intensity modulated proton therapy (IMPT) holds the potential to improve dose delivery and spare non-target tissues. The purpose of this study was to compare IMPT to three-dimensional (3D) conformal radiation following bilateral mastectomy and reconstruction.

Golden beam data for proton pencil-beam scanning.

Proton, as well as other ion, beams applied by electro-magnetic deflection in pencil-beam scanning (PBS) are minimally perturbed and thus can be quantified a priori by their fundamental interactions in a medium. This a priori quantification permits an optimal reduction of characterizing measurements on a particular PBS delivery system. The combination of a priori quantification and measurements will then suffice to fully describe the physical interactions necessary for treatment planning purposes.

Radiation dose assessment in a 320-detector-row CT scanner used in cardiac imaging.

Purpose: In the present era of cone-beam CT scanners, the use of the standardized CTDI100 as a surrogate of the idealized CTDI is strongly discouraged and, consequently, so should be the use of the dose-length product (DLP) as an estimate of the total energy imparted to the patient. However, the DLP is still widely used as a reference quantity to normalize the effective dose for a given scan protocol mainly because the CTDI100 is an easy-to-measure quantity. The aim of this article is therefore to describe a method for radiation dose assessment in large cone-beam single axial scans, which leads to a straightforward estimation of the total energy imparted to the patient.