Search

Radioresistant tumours remain complex to manage with current radiotherapy (RT) techniques. Heavy ion beams were proposed for their treatment given their advantageous radiobiological properties. However, previous studies with patients resulted in serious adverse effects in the surrounding healthy tissues. Heavy ion RT could therefore benefit from the tissue-sparing effects of minibeam radiation therapy (MBRT). To investigate the potential of this combination, here we assessed the biochemical response to neon MBRT (NeMBRT) through synchrotron-based Fourier transform infrared microspectroscopy (SR-FTIRM). Healthy (BJ) and tumour (B16-F10) cell lines were subjected to seamless (broad beam) neon RT (NeBB) and NeMBRT at HIMAC. SR-FTIRM measurements were conducted at the MIRAS beamline of ALBA Synchrotron. Principal component analysis (PCA) permitted to assess the biochemical effects after the irradiations and 24 hours post-irradiation for the different RT modalities and doses. For the healthy cells, NeMBRT resulted in the most dissimilar spectral signatures from non-irradiated cells early after irradiations, mainly due to protein conformational modifications. Nevertheless, most of the damage appeared to recover one day post-RT; conversely, protein- and nucleic acid-related IR bands were strongly affected by NeBB 24 hours after treatment, suggesting superior oxidative damage and nucleic acid degradation. Tumour cells appeared to be less sensitive to NeBB than to NeMBRT shortly after RT. Still, after one day, both NeBB and the high-dose NeMBRT regions yielded important spectral modifications, suggestive of cell death processes, protein oxidation or oxidative stress. Lipid-associated spectral changes, especially due to the NeBB and NeMBRT peak groups for the tumour cell line, were consistent with reactive oxygen species attacks. [ABSTRACT FROM AUTHOR]

Microdosimetry is a particularly powerful method to estimate the relative biological effectiveness (RBE) of any mixed radiation field. This is particularly convenient for therapeutic heavy ion therapy (HIT) beams, referring to ions larger than protons, where the RBE of the beam can vary significantly along the Bragg curve. Additionally, due to the sharp dose gradients at the end of the Bragg peak (BP), or spread out BP, to make accurate measurements and estimations of the biological properties of a beam a high spatial resolution is required, less than a millimetre. This requirement makes silicon microdosimetry particularly attractive due to the thicknesses of the sensitive volumes commonly being ∼10 m or less. Monte Carlo (MC) codes are widely used to study the complex mixed HIT radiation field as well as to model the response of novel microdosimeter detectors when irradiated with HIT beams. Therefore it is essential to validate MC codes against experimental measurements. This work compares measurements performed with a silicon microdosimeter in mono-energetic , and ion beams of therapeutic energies, against simulation results calculated with the Geant4 toolkit. Experimental and simulation results were compared in terms of microdosimetric spectra (dose lineal energy,), the dose mean lineal energy, y D and the RBE10, as estimated by the microdosimetric kinetic model (MKM). Overall Geant4 showed reasonable agreement with experimental measurements. Before the distal edge of the BP, simulation and experiment agreed within ∼10% for y D and ∼2% for RBE10. Downstream of the BP less agreement was observed between simulation and experiment, particularly for the and beams. Simulation results downstream of the BP had lower values of y D and RBE10 compared to the experiment due to a higher contribution from lighter fragments compared to heavier fragments. [ABSTRACT FROM AUTHOR]

This article presents a study of the response of the silicon on insulator (SOI) microdosimeter with 3-D sensitive volumes (SVs) to 400 MeV/u 16O and 500 MeV/u 56Fe ions mimicking galactic cosmic rays outside and inside the International Space Station (ISS). An average quality factor (Q) and the dose equivalent (H) of the radiation field were obtained experimentally, and the results were compared with GEANT4 simulations. [ABSTRACT FROM AUTHOR]

Purpose: Skin toxicity caused by radiotherapy has been visually classified into discrete grades. The present study proposes an objective and continuous assessment method of skin erythema in digital images taken under arbitrary lighting conditions, which is the case for most clinical environments. The purpose of this paper is to show the feasibility of the proposed method. Methods: Clinical data were gathered from six patients who received carbon beam therapy for lung cancer. Skin condition was recorded using an ordinary compact digital camera under unfixed lighting conditions; a laser Doppler flowmeter was used to measure blood flow in the skin. The photos and measurements were taken at 3 h, 30, and 90 days after irradiation. Images were decomposed into hemoglobin and melanin colors using independent component analysis. Pixel values in hemoglobin color images were compared with skin dose and skin blood flow. The uncertainty of the practical photographic method was also studied in nonclinical experiments. Results: The clinical data showed good linearity between skin dose, skin blood flow, and pixel value in the hemoglobin color images; their correlation coefficients were larger than 0.7. It was deduced from the nonclinical that the uncertainty due to the proposed method with photography was 15%; such an uncertainty was not critical for assessment of skin erythema in practical use. Conclusions: Feasibility of the proposed method for assessment of skin erythema using digital images was demonstrated. The numerical relationship obtained helped to predict skin erythema by artificial processing of skin images. Although the proposed method using photographs taken under unfixed lighting conditions increased the uncertainty of skin information in the images, it was shown to be powerful for the assessment of skin conditions because of its flexibility and adaptability. [ABSTRACT FROM AUTHOR]

A new measurement method to determine ac losses in superconducting coils has been proposed, and its validity confirmed experimentally. In this method, the ac losses in the coil can be obtained from measured Poynting's vectors around the coil windings. The Poynting's vectors can be obtained by local magnetic fields and electric fields around the coil. Local magnetic fields and electric fields are measured by pick-up coils and potential leads, which are mounted around the sample coil. These pick-up coil and potential lead pairs are arranged on the inner side, outer side, top, and bottom of the coil windings to cover the entire coil windings. This measurement method has the benefit that ac losses in a coil in a superconducting coil system consisting of multiple coils can be measured. Not only ac losses in the coils but also information on local electromagnetic phenomena in the coils can be obtained from profiles of the Poynting's vectors. In this paper, the details of the measuring method are described, and experiments using a coil wound with Bi-2223 multifilamentary tapes were carried out in liquid nitrogen to confirm the validity of the measurement method. [ABSTRACT FROM PUBLISHER]

The authors have investigated the dependency of radiation quality and absorbed dose on radiation field size in therapeutic carbon beams. The field size of the broad beam, formed using the passive technique, was controlled from 20 to 100 mm per side with a multileaf collimator. The absorbed dose and radiation quality on the beam center were evaluated at several depths in a water phantom using microdosimetric technique in experiments and Monte Carlo simulations. With an increase in the field size, the radiation quality was reduced, although the absorbed dose grew at the center of the field. This indicates that the dose and radiation quality at the center of the broad beam are influenced by particles from the off-center region via large-angle scattering and that such particles have relatively low radiation quality and mainly consist of fragment particles. Because such a tendency appeared to be more remarkable in the deeper region of the water phantom, it is likely that fragment particles that are born in a water phantom have a marked role in determining the field size effect. [ABSTRACT FROM AUTHOR]

The radiation-dose monitor, DARWIN, needs a set of response functions of the liquid organic scintillator to assess a neutron dose. SCINFUL-QMD is a Monte Carlo based computer code to evaluate the response functions. In order to improve the accuracy of the code, a new light-output function based on the experimental data was developed for the production and transport of protons deuterons, tritons, 3He nuclei and alpha particles, and incorporated into the code. The applicable energy of DARWIN was extended to 1 GeV using the response functions calculated by the modified SCINFUL-QMD code. [ABSTRACT FROM PUBLISHER]

The treatment planning approach used within the heavy ion tumour therapy project at GSI Darmstadt includes a biological optimisation, which is based on a biophysical model, the Local Effect Model (LEM). Here we show that the predictions of the LEM are in good agreement with clinical data obtained at the HIMAC in Chiba for the treatment of non-small-cell lung cancer, and the steep dose response for carbon ions is reproduced correctly. This steeper increase corresponds to an increasing RBE with increasing dose, which apparently is in contradiction to the systematics observed in general for in vitro measurements. A possible explanation of this discrepancy is based on the interindividual variation of photon sensitivity. [ABSTRACT FROM PUBLISHER]