Background and purpose:
Understanding the cellular and molecular effect of proton radiation, particularly the increased DNA damage complexity at the distal end of the Bragg curve, is current topic of investigation. This work aims to study in vitro clonogenic survival and DNA damage foci kinetics of a head and neck squamous cell carcinoma cell line at various positions along a double passively scattered Bragg curve. Complementary in silico studies are conducted to gain insights into the link between cell survival variations, experimentally yielded foci and the number and complexity of double strand breaks (DSBs).

Materials and methods:
Proton irradiations are performed at the HollandPTC R&D proton beamline, using a double passively scattered setup. A custom water phantom setup is employed to accurately position the samples within the Bragg curve. FaDu cells are irradiated at the proximal 36 % point of the Bragg peak, (P36), proximal 80 % point of the Bragg peak (P80) and distal 20 % point of the Bragg peak (D20), with dose-averaged mean lineal energies (yD¯) of 1.10 keV/μm, 1.80 keV/μm and 7.25 keV/μm, respectively.

Results:
Clonogenic survival correlates strongly with yD¯, showing similar survival for P36 (D37%=3.0 Gy) and P80 (D37%=2.9 Gy), but decreased survival for D20 (D37% = 1.6 Gy). D20 irradiated samples exhibit increased 53BP1 foci shortly after irradiation, slower resolution of the foci, and larger residual 53BP1 foci after 24 h, indicating unrepaired complex breaks. These experimental observations are supported by the in silico study which demonstrates that irradiation at D20 leads to a 1.7-fold increase in complex DSBs with respect to the total number of strand breaks compared to P36 and P80.

Conclusions:
This combined approach provides valuable insights into the cellular and molecular effect of proton radiation, emphasizing the increased DNA damage complexity at the distal end of the Bragg curve, and has the potential to enhance the efficacy of proton therapy.@en

Objective. Bragg peak measurements play a key role in the beam quality assurance in proton therapy. Used as base data for the treatment planning softwares, the accuracy of the data is crucial when defining the range of the protons in the patient. Approach. In this paper a protocol to reconstruct a Pristine Bragg Peak exploring the direct correlation between the particle flux and the dose deposited by particles is presented. Proton flux measurements at the HollandPTC and FLUKA Monte Carlo simulations are used for this purpose. This new protocol is applicable to plastic scintillator detectors developed for Quality Assurance applications. In order to obtain the Bragg curve using a plastic fiber detector, a PMMA phantom with a decoupled and moveable stepper was designed. The step phantom allows to change the depth of material in front of the fiber detector during irradiations. The Pristine Bragg Peak reconstruction protocol uses the measured flux of particles at each position and multiplies it by the average dose obtained from the Monte Carlo simulation at each position. Main results. The results show that with this protocol it is possible to reconstruct the Bragg Peak with an accuracy of about 470 µm, which is in accordance with the tolerances set by the AAPM. Significance. It has the advantage to be able to overcome the quenching problem of scintillators in the high ionization density region of the Bragg peak.@en

The so-called Sale Price Appraisol Ratio (SPAR) method has been applied in a number of countries to construct house price indexes. The method, which uses ratios of transaction prices and previous appraised values to build up an index, has been applied in New Zealand, Sweden and Denmark. This paper discusses the statistical properties of the SPAR price indexes and compares the SPAR with Repeat Sales Index created from the same transactions data. Preliminary empirical results for the Netherlands covering a period of over ten years are presented. As SPAR appears to have more to offer than the more traditional methods, government agencies elsewhere would be well advised to consider it when developing indexes for price movements in the housing stock.@en

SPAR (Sale Price Appraisal Ratio) is a model for constructing House Price Indexes on the basis of the ratios of transaction prices and previous Appraisal Values. It has been applied in New Zealand, Sweden and Denmark. This paper assesses the reliability of Appraisal Value and compares the SPAR Index with the Repeat Sales Index and the Hedonic Index based on the same transaction data. It presents preliminary empirical results for the Netherlands over a ten-year period. As SPAR appears to have more to offer than the more traditional methods, government agencies elsewhere would be well advised to consider it when developing indexes for price movements in the housing stock.@en