A patient-specific hybrid phantom for calculating radiation dose and equivalent dose to the whole body

Objective: As cancer survivorship increases, there is growing interest in minimizing the late effects of radiation therapy such as radiogenic second cancer, which may occur anywhere in the body. Assessing the risk of late effects requires knowledge of the dose distribution throughout the whole body, including regions far from the treatment field, beyond the typical anatomical extent of clinical CT scans. Approach: A hybrid phantom was developed which consists of in-field patient CT images extracted from ground truth whole-body CT (WBCT) scans, out-of-field mesh phantoms scaled to basic patient measurements, and a blended transition region. Four of these hybrid phantoms were created, representing male and female patients receiving proton therapy treatment in pelvic and cranial sites. To assess the performance of the hybrid approach, we simulated treatments using the hybrid phantoms, the scaled and unscaled mesh phantoms, and the ground truth whole-body CTs. We calculated absorbed dose and equivalent dose in and outside of the treatment field, with a focus on neutrons induced in the patient by proton therapy. Proton and neutron dose was calculated using a general purpose Monte Carlo code. Main Results: The hybrid phantom provided equal or superior accuracy in calculated organ dose and equivalent dose values relative to those obtained using the mesh phantoms in 78% in all selected organs and calculated dose quantities. Comparatively the default mesh and scaled mesh were equal or superior to the other phantoms in 21% and 28% of cases respectively. Significance: The proposed methodology for hybrid synthesis provides a tool for whole-body organ dose estimation for individual patients without requiring CT scans of their entire body. Such a capability would be useful for personalized assessment of late effects and risk-optimization of treatment plans.

Comparison of Surface Equivalent Dose in CBCT, Digital Panoramic and Intra-Oral X-Ray Generators Using InstadoseTM Device: An In-Vitro Study

Background: Radiation protection in the dental examination is often overlooked because the doses delivered are negligible. However, the volume of dental radiological examinations will constitute almost 15% of all the radiological examinations carried out in the medical field. Aim: This study aims to evaluate and compare the surface equivalent dose on various target organs from various radiology devices on the RINN phantom, and the effect of numerous scanning protocols on said dose using dosimetry badge (Instadose). Objectives: The main objective is to study surface equivalent doses delivered in various critical organ regions in the facial region with the help of an Instadose device and to compare the doses delivered between 2D programs against 3D programs. Materials and Methods: RINN phantom was mounted on a dental chair for use against Planmeca ProMax 3D Classic and Planmeca intraoral ProX. Models. An Instadose badge was placed on various anatomical landmarks, and radiographic exposure protocols were applied to vary the parameters. The equivalent dose was calculated by connecting the dosimeter to a laptop and performing an instant reading output on the Instadose software. Results: The Thyroid showed a mean of 0.350, 0.0000, 0.0133, and 0.0000 in response to exposure by intraoral machine ProX, Panoramic, CBCT, and CBCT in ULD mode respectively. The dose absorbed by the left salivary glands was found to be significantly lower than the right salivary glands in panoramic exposures. Conclusion: It was revealed that a significant reduction in the dose when applying the Ultra-Low Dose protocol was noticed, and it reached up to 100% in the thyroid. It was also noted that there is no need for a thyroid collar in CBCT and Panoramic exposures. Maintaining the KVp at a constant and the exposure time as a variant caused a change in the dose equivalent received by the floor of the mouth and the right salivary gland.

85 Diuretics trajectories in dilated cardiomyopathy

Aims Diuretics in heart failure (HF) are commended to relieve symptoms at lowest dosage effective. Dilated cardiomyopathy (DCM) is a particular HF setting with several variables that may influence disease trajectory. We aimed to assess the long-term use of diuretics in DCM, the possibility of withdrawal and to explore the prognostic correlations. Methods and results All consecutive DCM patients enrolled from 1990 to 2018 were considered eligible. All the patients had available the information about the furosemide-equivalent dose at baseline and at follow-up evaluation within 24 months. Patients were categorized in stable (diuretic dose variation <50%), increasers (diuretics dose increase ≥50% or initiation of diuretic therapy), and decreasers (diuretics dose decrease ≥50% or never prescribed diuretics in the 24-months observation period). The prognostic role of the diuretics trajectory group was assessed with Kaplan Meier analysis and with a time-dependent multivariable model. The outcome measure was a composite of all-cause death/heart transplantation/HF hospitalization (ACD/HTx/HFH). 908 patients were included [mean age 50 ± 16, 70% male sex, 24% NYHA class III or IV, mean left ventricular ejection fraction (LVEF) 31 ± 9%, 66% treated with diuretics at baseline]. The furosemide-equivalent dose at enrolment had a linear association with the risk of outcome. Compared to other groups, decreaser patients were younger, had less HF symptoms, higher LVEF and more dilated left atrium. Decreasers had a lower prescription rate of diuretics and less frequent indication to renin-angiotensin inhibitors and mineralocorticoid receptors antagonists. Over a median follow-up of 122 (62–195) months decreasers had the lowest incidence of outcome, followed by stable, while increasers had the worst outcome (P < 0.001). After adjustment for other prognosticators, compared to stable patients, decreasers had a reduced risk of ACD/HTx/HFH [HR: 0.497 (95% CI: 0.337–0.731)] while increasers had the highest risk of adverse outcome [HR: 2.027 (95% CI: 1.254–3.276)]. Similarly, amongst patients taking diuretics at baseline, the diuretics withdrawal was in independent outcome predictor. The only multivariable predictors of diuretics withdrawal were younger age and lower furosemide-equivalent dose at enrolment. Conclusions In DCM patients the diuretics dose at baseline is a strong prognosticator. Diuretics dose reduction or its withdrawal provides a prognostic benefit on hard outcome. Diuretics tapering in selected patients should be considered in the short-term follow-up to improve DCM prognosis.

Luminescence age calculation through Bayesian convolution of equivalent dose and dose-rate distributions: the D_e_D_r model

In nature, any mineral grain (quartz or feldspar) receives a dose-rate (Dr) specific to its environment. The dose-rate distributions, therefore, reflect the micro-dosimetric context of grains of similar size. If all the grains have been well bleached at deposition, this distribution corresponds, within uncertainties, to the distribution of equivalent doses (De). Their combination (convolution of the De and Dr distributions in the De_Dr model proposed here) allows the calculation of the true depositional age. If grains whose De values are not representative of this age (hereafter called "outliers") are present in the De distribution, the model allows them to be identified before the age is calculated. As the De_Dr approach relies only on the Dr distribution, the model avoids any assumption representing the De distribution, which is usually difficult to justify. Herein, we outline the mathematical concepts of the De_Dr approach (more details are given in Galharret et al., accepted) and the exploitation of this Bayesian modelling based on an R code available in the R package 'Luminescence'. We also present a series of tests using simulated Dr and De distributions with and without outliers and show that the De_Dr approach can be an alternative to available models for interpreting De distributions.

Quantitative assessments of late radiation-induced skin and soft tissue toxicity and correlation with RTOG scales and biological equivalent dose in breast cancer

Purpose Radiation-induced toxicity (RIT) is usually assessed by inspection and palpation. Due to their subjective and unquantitative nature, objective methods are required. This study aimed to determine whether a quantitative tool is able to assess RIT and establish an underlying BED-response relationship in breast cancer. Methods Patients following seven different breast radiation protocols were recruited to this study for RIT assessment with qualitative and quantitative examination. The biologically equivalent dose (BED) was used to directly compare different radiation regimens. RIT was subjectively evaluated by physicians using the Radiation Therapy Oncology Group (RTOG) late toxicity scores. Simultaneously an objective multiprobe device was also used to quantitatively assess late RIT in terms of erythema, hyperpigmentation, elasticity and skin hydration. Results In 194 patients, in terms of the objective measurements, treated breasts showed higher erythema and hyperpigmentation and lower elasticity and hydration than untreated breasts (p < 0.001, p < 0.001, p < 0.001, p = 0.019, respectively). As the BED increased, Δerythema and Δpigmentation gradually increased as well (p = 0.006 and p = 0.002, respectively). Regarding the clinical assessment, the increase in BED resulted in a higher RTOG toxicity grade (p < 0.001). Quantitative assessments were consistent with RTOG scores. As the RTOG toxicity grade increased, the erythema and pigmentation values increased, and the elasticity index decreased (p < 0.001, p = 0.016, p = 0.005, respectively). Conclusions The multiprobe device can be a sensitive and simple tool for research purpose and quantitatively assessing RIT in patients undergoing radiotherapy for breast cancer. Physician-assessed toxicity scores and objective measurements revealed that the BED was positively associated with the severity of RIT.