Potential Defects and Improvements of Equivalent Uniform Dose Prediction Model Based on the Analysis of Radiation-Induced Brain Injury

PurposeTo study the impact of dose distribution on volume-effect parameter and predictive ability of equivalent uniform dose (EUD) model, and to explore the improvements.Methods and MaterialsThe brains of 103 nasopharyngeal carcinoma patients treated with IMRT were segmented according to dose distribution (brain and left/right half-brain for similar distributions but different sizes; VD with different D for different distributions). Predictive ability of EUDVD (EUD of VD) for radiation-induced brain injury was assessed by receiver operating characteristics curve (ROC) and area under the curve (AUC). The optimal volume-effect parameter a of EUD was selected when AUC was maximal (mAUC). Correlations between mAUC, a and D were analyzed by Pearson correlation analysis. Both mAUC and a in brain and half-brain were compared by using paired samples t-tests. The optimal DV and VD points were selected for a simple comparison.ResultsThe mAUC of brain/half-brain EUD was 0.819/0.821 and the optimal a value was 21.5/22. When D increased, mAUC of EUDVD increased, while a decreased. The mAUC reached the maximum value when D was 50–55 Gy, and a was always 1 when D ≥55 Gy. The difference of mAUC/a between brain and half-brain was not significant. If a was in range of 1 to 22, AUC of brain/half-brain EUDV55 Gy (0.857–0.830/0.845–0.830) was always larger than that of brain/half-brain EUD (0.681–0.819/0.691–0.821). The AUCs of optimal dose/volume points were 0.801 (brain D2.5 cc), 0.823 (brain V70 Gy), 0.818 (half-brain D1 cc), and 0.827 (half-brain V69 Gy), respectively. Mean dose (equal to EUDVD with a = 1) of high-dose volume (V50 Gy–V60 Gy) was superior to traditional EUD and dose/volume points.ConclusionVolume-effect parameter of EUD is variable and related to dose distribution. EUD with large low-dose volume may not be better than simple dose/volume points. Critical-dose-volume EUD could improve the predictive ability and has an invariant volume-effect parameter. Mean dose may be the case in which critical-dose-volume EUD has the best predictive ability.

A Pilot Study of Safer Radiation Dosage to the Heart and Its Subregions

Background and Objectives: The real impact of ionizing radiation on the heart and poorer overall survival for patients with non small cell lung cancer (NSCLC) remains unclear. This study aims to determine the safe dose constraints to the heart’s subregions that could prevent patients’ early non-cancerous death and improve their quality of life. Methods and Materials: A retrospective cohort study was performed containing 51 consecutive patients diagnosed with stage III NSCLC and treated using 3D, Intensity-modulated radiation therapy (IMRT), and Volumetric modulated arc therapy (VMAT) radiotherapy. For a dosimetric analysis, these structures were chosen: heart, heart base (HB), and region of great blood vessels (GBV). Dose–volume histograms (DVH) were recorded for all mentioned structures. Maximum and mean doses to the heart, HB, the muscle mass of the HB, and GBV were obtained. V10–V60 (%) parameters were calculated from the DVH. After performed statistical analysis, logistic regression models were created, and critical doses calculated. Results: The critical dose for developing a fatal endpoint for HB was 30.5 Gy, while for GBV, it was 46.3 Gy. Increasing the average dose to the HB or GBV by 1 Gy from the critical dose further increases the possibility of early death by 22.0% and 15.8%, respectively. Conclusions: We suggest that the non-canonical sub-regions of the heart (HB and GBV) should be considered during the planning stage. Additional constraints of the heart subregions should be chosen accordingly, and we propose that the mean doses to these regions be 30.5 Gy and 46.3 Gy, respectively, or less. Extrapolated DVH curves for both regions may be used during the planning stage with care.

Species effect on decay resistance of wood exposed to exterior conditions above the ground in Spain

The objective of this study is to evaluate the effect of the species on the biological resistance of wood against decay and to propose corrective values of the critical dose. To evaluate the species effect, the evolution of the number of days per year with moisture content exceeding 18% was assessed in flat sawn 20x100x750 mm3 test samples of Laricio, Scots and Radiata pines and also of Norway spruce, Eucalypt (globulus) and sweet chestnut during the years 2016, 2017 and 2018, exposed at seven locations in Spain with the most representative Spanish climates. A value of 1.0 is proposed for the four conifers, 2.51 for the Eucalypt and 1.84 for the Sweet chestnut. As regards the species effect it was not possible to separate that corresponding to the different wetting/releasing ability of each species and that of their crack susceptibility, both aspects having to be evaluated together as “species factor”.

Improving data quality and expanding BioSAXS experiments to low-molecular-weight and low-concentration protein samples

The addition of compounds to scavenge the radical species produced during biological small-angle X-ray scattering (BioSAXS) experiments is a common strategy to reduce the effects of radiation damage and produce better quality data. As almost half of the experiments leading to structures deposited in the SASBDB database used scavengers, finding potent scavengers would be advantageous for many experiments. Here, four compounds, three nucleosides and one nitrogenous base, are presented which can act as very effective radical-scavenging additives and increase the critical dose by up to 20 times without altering the stability or reducing the contrast of the tested protein solutions. The efficacy of these scavengers is higher than those commonly used in the field to date, as verified for lysozyme solutions at various concentrations from 7.0 to 0.5 mg ml−1. The compounds are also very efficient at mitigating radiation damage to four proteins with molecular weights ranging from 7 to 240 kDa and pH values from 3 to 8, with the extreme case being catalase at 6.7 mg ml−1, with a scavenging factor exceeding 100. These scavengers can therefore be instrumental in expanding BioSAXS to low-molecular-weight and low-concentration protein samples that were previously inaccessible owing to poor data quality. It is also demonstrated that an increase in the critical dose in standard BioSAXS experiments leads to an increment in the retrieved information, in particular at higher angles, and thus to higher resolution of the model.

Radiation pneumonitis (RP) after stereotactic body radiation therapy (SBRT) for early-stage non-small cell lung cancer (NSCLC): A prospective, observational study.

e21065 Background: RP is a clinically challenging side effect following SBRT. The reported incidence of RP varies from 2.2% to 46.8%, depending on study design and different grading systems. We evaluated the grading systems for RP and identified possible predictive tests for RP. Furthermore, we estimated the correlation between RP and dosimetric measurements from the radiation therapy. Methods: Medically inoperable patients, n = 44, with peripherally located NSCLC stage I-II, were treated with SBRT, with a total dose of 45–56 Gy in 3–8 fractions. Median age was 75 years, 43.2% were female and 60% had moderate to very severe COPD. Follow up included physical examination by pulmonologist, spirometry and single-breath lung diffusing capacity (DLCO) and CT evaluation at baseline and 1.5, 3, 6, 9 and 12 months after SBRT. Results: We constructed three groups for grading RP based on CTCAE version 5.0 and imaging changes according to EORTC (LENT-SOMA) Non-RP (asymptomatic or mild symptoms and slight imaging changes, n = 19, 43%), Asymptomatic, radiology-only RP (asymptomatic or mild symptoms, increased density imaging changes, n = 17, 39%) and Symptomatic and radiology-detected RP (moderate and severe symptoms and increased density imaging changes, n = 8, 18%). Active smokers and patients with emphysema were overrepresented in non-RP group. In the symptomatic RP group, DLCO and FEV1 dropped almost 5% 4-6 weeks after SBRT, before symptoms and imaging changes, and DLCO, FVC and FEV1 dropped significantly at 3 months (table). Development of RP was associated with critical dose-volume parameter 1000ccm and 1500ccm. Several dosimetric parameters significantly negative correlate with FVC-drop at 1 and 3 months only in symptomatic RP. Conclusions: Active smokers and patients with emphysema have less propensity of RP. Symptomatic RP is seen with a presymptomatic drop in FEV1 and DLCO occurring 4-6 weeks after SBRT. Critical dose-volume parameter is important parameters for RP. Correlation between dosimetric parameters and FVC-drop in symptomatic RP. Clinical trial information: NCT02428049 . [Table: see text]

Radiation damage of thin films of YBa2Cu3O7 superconductors

The effect of ion-beam irradiation of YBa2Cu3O7 superconductors has been studied by Raman spectroscopy. The ion beams 4He, 16O and 127I have been used eat energies 4, 25 and 200 MeV, respectively, in an attempt to investigate the radi- ation damage with respect to the mass of the bombarding ions, further, different doses of irradiation have been tried for each ion beam in order to investigate at which critical dose the phase transition from crystalline to amorphous and the loss of superconductivity occur.