Individualized evaluation of the total dose received by radiotherapy patients: Integrating in-field, out-of-field, and imaging doses.

Purpose: To propose a methodology for integrating the out-of-field and imaging doses to the in-field dose received by radiotherapy (RT) patients. In addition, the impact of considering the total dose in planning and radiation-induced second malignancies (RISM) risk assessment will be evaluated in several scenarios comprising photon and proton treatments.

Methods: The total dose is the voxel-wise sum of the doses from the different radiation sources (accounting for the radiobiological effectiveness) produced during the whole RT chain.

ISaR, a computational tool to transform voxelized reference phantoms into patient-specific whole-body virtual CTs for peripheral dose estimation.

Background: The risk of radiogenic cancer induction due to radiotherapy depends on the dose received by the patient's organs. Knowing the position of all organs is needed to assess this dose in a personalized way. However, radiotherapy planning computed tomography (pCT) scans contain truncated patient anatomy, limiting personalized dose evaluation.

A simple analytical model for a fast 3D assessment of peripheral photon dose during coplanar isocentric photon radiotherapy.

Considering that cancer survival rates have been growing and that nearly two-thirds of those survivors were exposed to clinical radiation during its treatment, the study of long-term radiation effects, especially secondary cancer induction, has become increasingly important. To correctly assess this risk, knowing the dose to out-of-field organs is essential. As it has been reported, commercial treatment planning systems do not accurately calculate the dose far away from the border of the field; analytical dose estimation models may help this purpose.

Peripheral Organ Equivalent Dose Estimation Procedure in Proton Therapy.

The aim of this work is to present a reproducible methodology for the evaluation of total equivalent doses in organs during proton therapy facilities. The methodology is based on measuring the dose equivalent in representative locations inside an anthropomorphic phantom where photon and neutron dosimeters were inserted. The Monte Carlo simulation was needed for obtaining neutron energy distribution inside the phantom.

Low dose radiation therapy for COVID-19: Effective dose and estimation of cancer risk.

Background And Purpose: The objective of this work is to evaluate the risk of carcinogenesis of low dose ionizing radiation therapy (LDRT), for treatment of immune-related pneumonia following COVID-19 infection, through the estimation of effective dose and the lifetime attributable risk of cancer (LAR).

Material And Methods: LDRT treatment was planned in male and female computational phantoms. Equivalent doses in organs were estimated using both treatment planning system calculations and a peripheral dose model (based on ionization chamber measurements).

PERIPHERAL SURFACE DOSE FROM A LINEAR ACCELERATOR: RADIOCHROMIC FILM EXPERIMENTAL MEASUREMENTS OF FLATTENING FILTER FREE VERSUS FLATTENED BEAMS.

There is a growing interest in the use of flattening filter free (FFF) beams due to the shorter treatment times. The reduction of head scatter suggests a better radiation protection to radiotherapy patients, considering the expected decrease in peripheral surface dose (PSD). In this work, PSD of flattened (FF) and FFF-photon beams was compared.

Incorporation of Dosimetric Gradients and Parotid Gland Migration Into Xerostomia Prediction.

Due to the sharp gradients of intensity-modulated radiotherapy (IMRT) dose distributions, treatment uncertainties may induce substantial deviations from the planned dose during irradiation. Here, we investigate if the planned mean dose to parotid glands in combination with the dose gradient and information about anatomical changes during the treatment improves xerostomia prediction in head and neck cancer patients. Eighty eight patients were retrospectively analyzed.

Intensity-modulated radiation therapy and volumetric modulated arc therapy versus conventional conformal techniques at high energy: Dose assessment and impact on second primary cancer in the out-of-field region.

The aim of this work was to estimate peripheral neutron and photon doses associated with the conventional 3D conformal radiotherapy techniques in comparison to modern ones such as Intensity modulated radiation therapy and volumetric modulated arc therapy. Assessment in terms of second cancer incidence ought to peripheral doses was also considered. For that, a dosimetric methodology proposed by the authors has been applied beyond the region where there is no CT information and, thus, treatment planning systems do not calculate and where, nonetheless, about one third of second primary cancers occurs.

Impact of different biologically-adapted radiotherapy strategies on tumor control evaluated with a tumor response model.

Motivated by the capabilities of modern radiotherapy techniques and by the recent developments of functional imaging techniques, dose painting by numbers (DPBN) was proposed to treat tumors with heterogeneous biological characteristics. This work studies different DPBN optimization techniques for virtual head and neck tumors assessing tumor response in terms of cell survival and tumor control probability with a previously published tumor response model (TRM). Uniform doses of 2 Gy are redistributed according to the microscopic oxygen distribution and the density distribution of tumor cells in four virtual tumors with different biological characteristics.

Uncomplicated and Cancer-Free Control Probability (UCFCP): A new integral approach to treatment plan optimization in photon radiation therapy.

Purpose: Biological treatment plan evaluation does not currently consider second cancer induction from peripheral doses associated to photon radiotherapy. The aim is to propose a methodology to characterize the therapeutic window by means of an integral radiobiological approach, which considers not only Tumour Control Probability (TCP) and Normal Tissue Complication Probability (NTCP) but also Secondary Cancer Probability (SCP).

Methods: Uncomplicated and Cancer-Free Control Probability (UCFCP) function has been proposed assuming a statistically uncorrelated response for tumour and normal tissues.

Modelling radiation-induced cell death and tumour re-oxygenation: local versus global and instant versus delayed cell death.

The resistance of hypoxic cells to radiation, due to the oxygen dependence of radiosensitivity, is well known and must be taken into account to accurately calculate the radiation induced cell death. A proper modelling of the response of tumours to radiation requires deriving the distribution of oxygen at a microscopic scale. This usually involves solving the reaction-diffusion equation in tumour voxels using a vascularization distribution model.

Dosimetric characterization and optimization of a customized Stanford total skin electron irradiation (TSEI) technique.

Total skin electron irradiation (TSEI) has been used as a treatment for mycosis fungoides. Our center has implemented a modified Stanford technique with six pairs of 6 MeV adjacent electron beams, incident perpendicularly on the patient who remains lying on a translational platform, at 200 cm from the source. The purpose of this study is to perform a dosimetric characterization of this technique and to investigate its optimization in terms of energy characteristics, extension, and uniformity of the treatment field.

Neutron contamination in radiotherapy: estimation of second cancers based on measurements in 1377 patients.

Purpose: Second cancer, as a consequence of a curative intent radiotherapy (RT), represents a growing concern nowadays. The unwanted neutron exposure is an important contributor to this risk in patients irradiated with high energy photon beams. The design and development by our group of a neutron digital detector, together with the methodology to estimate, from the detector readings, the neutron equivalent dose in organs, made possible the unprecedented clinical implementation of an online and systematic neutron dosimetry system.

Effects of heating rate and dose on trapping parameters of TLD-100 crystals.

The characteristics of the thermoluminescence glow curve and dosimetric peak of LiF:Mg,Ti (TLD-100) crystals are studied, with emphasis on the evaluation of the influence of the irradiation dose and heating rate on the dosimetric peak (peak 5) trapping parameters. These parameters were obtained using a computerized deconvolution routine that assumed first-order kinetics for each peak composing the glow curve. This routine was able to fit accurately (1.

Predictive models for pulmonary function changes after radiotherapy for breast cancer and lymphoma.

Purpose: To propose multivariate predictive models for changes in pulmonary function tests (ΔPFTs) with respect to preradiotherapy (pre-RT) values in patients undergoing RT for breast cancer and lymphoma.

Methods And Materials: A prospective study was designed to measure ΔPFTs of patients undergoing RT. Sixty-six patients were included.

Dose-volume constraints to reduce rectal side effects from prostate radiotherapy: evidence from MRC RT01 Trial ISRCTN 47772397.

Purpose: Radical radiotherapy for prostate cancer is effective but dose limited because of the proximity of normal tissues. Comprehensive dose-volume analysis of the incidence of clinically relevant late rectal toxicities could indicate how the dose to the rectum should be constrained. Previous emphasis has been on constraining the mid-to-high dose range (>/=50 Gy).