Near-field coded-mask technique and its potential for proton therapy monitoring.

Objective.Prompt-gamma imaging encompasses several approaches to the online monitoring of the beam range or deposited dose distribution in proton therapy. We test one of the imaging techniques - a coded mask approach - both experimentally and via simulations.Approach.Two imaging setups have been investigated experimentally. Each of them comprised a structured tungsten collimator in the form of a modified uniformly redundant array mask and a LYSO:Ce scintillation detector of fine granularity. The setups differed in detector dimensions and operation mode (1D or 2D imaging). A series of measurements with radioactive sources have been conducted, testing the performance of the setups for near-field gamma imaging. Additionally, Monte Carlo simulations of a larger setup of the same type were conducted, investigating its performance with a realistic gamma source distribution occurring during proton therapy.Main results.The images of point-like sources reconstructed from two small-scale prototypes' data using the maximum-likelihood expectation maximisation algorithm constitute the experimental proof of principle for the near-field coded-mask imaging modality, both in the 1D and the 2D mode. Their precision allowed us to calibrate out certain systematic offsets appearing due to the limited alignment accuracy of setup elements. The simulation of the full-scale setup yielded a mean distal falloff retrieval precision of 0.72 mm in the studies for beam energy range 89.5-107.9 MeV and with 1 × 108protons (a typical number for distal spots). The implemented algorithm of image reconstruction is relatively fast-a typical procedure needs several seconds.Significance.Coded-mask imaging appears a valid option for proton therapy monitoring. The results of simulations let us conclude that the proposed full-scale setup is competitive with the knife-edge-shaped and the multi-parallel slit cameras investigated by other groups.

Machine learning-based event recognition in SiFi Compton camera imaging for proton therapy monitoring.

Objective.Online monitoring of dose distribution in proton therapy is currently being investigated with the detection of prompt gamma (PG) radiation emitted from a patient during irradiation. The SiPM and scintillation Fiber based Compton Camera (SiFi-CC) setup is being developed for this aim.Approach.A machine learning approach to recognize Compton events is proposed, reconstructing the PG emission profile during proton therapy. The proposed method was verified on pseudo-data generated by aGeant4 simulation for a single proton beam impinging on a polymethyl methacrylate (PMMA) phantom. Three different models including the boosted decision tree (BDT), multilayer perception (MLP) neural network, and k-nearest neighbour (k-NN) were trained using 10-fold cross-validation and then their performances were assessed using the receiver operating characteristic (ROI) curves. Subsequently, after event selection by the most robust model, a software based on the List-Mode Maximum Likelihood Estimation Maximization (LM-MLEM) algorithm was applied for the reconstruction of the PG emission distribution profile.Main results.It was demonstrated that the BDT model excels in signal/background separation compared to the other two. Furthermore, the reconstructed PG vertex distribution after event selection showed a significant improvement in distal falloff position determination.Significance.A highly satisfactory agreement between the reconstructed distal edge position and that of the simulated Compton events was achieved. It was also shown that a position resolution of 3.5 mm full width at half maximum (FWHM) in distal edge position determination is feasible with the proposed setup.

Prompt-gamma emission in GEANT4 revisited and confronted with experiment.

PURPOSE: The field of online monitoring of the beam range is one of the most researched topics in proton therapy over the last decade. The development of detectors that can be used for beam range verification under clinical conditions is a challenging task. One promising possible solution are modalities that record prompt-gamma radiation produced by the interactions of the proton beam with the target tissue. A good understanding of the energy spectra of the prompt gammas and the yields in certain energy regions is crucial for a successful design of a prompt-gamma detector. Monte-Carlo simulations are an important tool in development and testing of detector concepts, thus the proper modelling of the prompt-gamma emission in those simulations are of vital importance. In this paper, we confront a number of GEANT4 simulations of prompt-gamma emission, performed with different versions of the package and different physics lists, with experimental data obtained from a phantom irradiation with proton beams of four different energies in the range 70-230 MeV. METHODS: The comparison is made on different levels: features of the prompt-gamma energy spectrum, gamma emission depth profiles for discrete transitions and the width of the distal fall-off in those profiles. RESULTS: The best agreement between the measurements and the simulations is found for the GEANT4 version 10.4.2 and the reference physics list QGSP_BIC_HP. CONCLUSIONS: Modifications to prompt-gamma emission modelling in higher versions of the software increase the discrepancy between the simulation results and the experimental data.

Environmental noise, its types and effects on health.

Noise can be defined as an undesirable sound that pollutes the environment. If noise is continuous and exceeds certain levels, negative effects on health can be observed. In recent years, the impact of environmental noise (road traffic noise, railway traffic noise, air traffic noise and industrial noise) on human health has come under increasingly intense scrutiny. Noise can cause a number of negative effects on health that directly or indirectly affect humans. The occurrence of some certain and harmful health effects drives the onset of others and may contribute to the development of various diseases. Health is not only a state of physical well-being, but also mental well-being. Mental health primarily depends on the quality of life, which can be affected by various environmental factors, such as noise. An important aspect of fighting noise is the most effective protection of the population by avoiding sources of noise and reducing it. This can be achieved by introducing new technical solutions and new technologies, including devices that generate less noise. Another important measure is educating the society and influencing the change of individual and collective behavior, which may contribute to reducing the harmful factor, which is noise in human life, and minimize the resulting negative effects on health.

Radiofrequency electromagnetic radiation from Wi-fi and its effects on human health, in particular children and adolescents. Review.

Radiofrequency electromagnetic radiation emitted from Wi-Fi devices is nonionizing radiation. The frequencies used in wireless technology are similar to those applied in mobile telephony. Due to the much lower output power of devices using Wi-Fi compared to mobile phones, the degree of exposure to radiation is also lower. Most of the research on Wi-Fi has been carried out in less favorable or adverse conditions, involving higher power values of devices (peak values instead of average values) and smaller distances of working devices from measuring points. None of the studies conducted so far have indicated that there were the exceedances of the permissible values of radiofrequency electromagnetic radiation contained in the Polish and global legal regulations. Similar to the research related to the impact of mobile telephony on human health, the studies conducted until now focusing on exposure to Wi-Fi are considered ambiguous as they do not give a definitive answer on the possible negative (including carcinogenic) effects on human health. Because of the continuous development of wireless networks, there is a need for further research on this topic. Moreover, due to the high popularity of devices using Wi-Fi among children and adolescents, whose period of exposure to electromagnetic radiation is longer compared to adults, it is necessary to continuously observe these populations and subject them to careful analysis.

The SiFi-CC project - Feasibility study of a scintillation-fiber-based Compton camera for proton therapy monitoring.

One of the big challenges for proton therapy is the development of tools for online monitoring of the beam range, which are suited to operate in clinical conditions and can be included in the clinical practice. A Compton camera based on stacks of heavy scintillating fibers used for prompt-gamma imaging is a promising approach for this task. It provides full, three-dimensional information on the deposited dose distribution while showing a high detection efficiency and rate capability due to its high granularity. The investigation of the rate capability and detection efficiency of such a camera under clinical conditions by means of Geant4 simulations is presented along with the event construction algorithm. The results hint towards a very low pile-up rate in the detector and a relatively high detection efficiency, so that imaging of a single proton beam spot appears to be an achievable goal.

Mobile telephony and its effects on human health

In recent years, there has been a rapid increase in the number of electromagnetic radiation sources such as mobile phones and base stations of mobile telephony. This radiation has been classified by the International Agency for Research on Cancer as a possible human carcinogen (group 2B). For this reason, many studies have been carried out on the impact of mobile telephony on human health. The largest of the experiments were carried out on animals. Due to the divergent results of many studies, there was no clear answer on the possible carcinogenic effects of this type of radiation on health. Detection of cancer shortly after an exposure is the most difficult task in analyzing the results. Some of the studies require repetition and verification of the results. In the case of negative effects of electromagnetic fields on brain activity, sleep, heart rate, cognitive function and blood pressure, no consistent evidence has been obtained either. In view of the increasing popularity of mobile phones, their location at short distances from the body (mainly the head) and the development of mobile phone technologies (which entails an increase in the number of base stations), further research, especially among young people, is needed. The duration of human exposure to electromagnetic radiation is subject to an increase and only further research can provide an answer on the possible negative effects of mobile phones and base stations.

Long-term effects of premature birth on somatic development in women through adolescence and adulthood.

Objectives To evaluate the long-term consequences of preterm birth on anthropometric parameters in women in adolescence and into adulthood. Methods Seventy girls born preterm (age 12.22 ± 1.52 years) and 48 born at term participated in the first stage. Eighteen years later, 13 of the same women participated in a follow-up and were compared with a control group of 27 women. We compared anthropometric results across the two examinations, and in the second stage, also assessed body composition using bioelectrical impedance analysis. Results No significant differences were found in anthropometric parameters or the content of individual components of the body between the preterm-born and control groups. However, the preterm-born group showed a tendency for higher average fat mass and lower fat-free and soft lean mass compared with the control group, and had a significantly higher mean waist-hip ratio. Conclusions Preterm birth does not adversely affect somatic development in girls during adolescence, but shows a correlation with an elevated waist-hip ratio in adulthood.

Are preterm-born survivors at risk of long-term respiratory disease?

BACKGROUND: To evaluate the long-term impact of preterm birth on respiratory function in female patients born preterm, we undertook spirometric examinations twice, as they reached the age of puberty, then follow-up examinations of part of the same cohort in adulthood. We sought evidence that preterm birth is correlated with poorer spirometric results into adulthood. METHODS: A total of 70 girls (aged 12.2 ± 1.5 years in 1997) who had been born preterm (at 34.7 ± 1.86 weeks, none having experienced bronchopulmonary dysplasia) took part in spriometric examinations in 1997 and again in 1998. Of those, after a gap of 17 years, a group of 12 were successfully recontacted and participated in the 2015 examination as adults (then aged 27.6 ± 2.6 years, born at 34.5 ± 1.92 weeks). We compared spirometric results across the adolescent and adult examinations, and compared the adult results with an adult reference group. RESULTS: The percentage values of FEV1 (forced expiratory volume in 1 s), FVC (forced vital capacity) and MVV (maximal voluntary ventilation) showed significant improvement between the two examinations in the early adolescent period. In adulthood, FEV1%pred (percentage predicted forced expiratory volume in 1 s) showed no statistically significant difference. The mean values of both FVC and FVC%pred (percentage predicted forced vital capacity) for the preterm-born group were lower than for the reference group, but this was not statistically significant. The preterm-born group showed lower values of such parameters as forced expiratory flow at 25-75% of FVC, MEF25 (maximal expiratory flow at 25% of forced vital capacity) and FEV1/FVC as compared with the reference group, but again without statistical significance. CONCLUSIONS: (1) A somewhat below-norm level of respiratory parameters among preterm-born girls entering pubescence may attest to continued negative impact on their respiratory system. (2) A significant improvement in their spirometric results 1 year later may indicate that pubescence helps compensate for the earlier negative effect of preterm birth. (3) No significant differences were seen in lung function in preterm-born adults as compared with a reference group of adults, although the preterm-born group did exhibit lower values of all parameters studied and more frequent obstructive disorders.

Spectroscopic study of prompt-gamma emission for range verification in proton therapy.

We present the results of an investigation of the prompt-gamma emission from an interaction of a proton beam with phantom materials. Measurements were conducted with a novel setup allowing the precise selection of the investigated depth in the phantom, featuring three different materials composed of carbon, oxygen and hydrogen. We studied two beam energies of 70.54 and 130.87MeV and two detection angles: 90° and 120°. The results are presented in form of profiles of the prompt-gamma yield as a function of depth. In the analysis we focused on the transitions with the largest cross sections: 12C4.44→g.s. and 16O6.13→g.s.. We compare the profiles obtained under various irradiation conditions, with emphasis on the shape of the distal fall-off. The results are also compared to calculations including different cross-section models. They are in agreement with the model exploiting published cross-section data, but the comparison with the Talys model shows discrepancies.

Dosages of ionizing radiation during limb diagnostic X-ray examinations.

BACKGROUND: X-ray examination is associated with the patient's exposure to ionizing radiation. The dose values depend on the type of the medical procedure used, the X-ray unit technical condition and exposure conditions selected by X-ray technicians. The aim of this study has been to assess the entrance surface dose (ESD) values received by patients during the limb X-ray examination. The results should help doctors in making the decision about sending patients for X-ray examination. At the same time the X-ray unit condition and examination method performance are important for the radiological protection of the medical staff. MATERIAL AND METHODS: The study covered the total number of 118 X-ray units located in 56 public healthcare entities and private medical centers in the Masovian Voivodeship. The measurement of the radiation dose rate received by patients was based on our own research procedures. RESULTS: The research has found that there are even more than 10-fold differences in the dose values received by adult patients with several-fold differences in the case of children patients. The broadest dose value range for adult patients was related to femur radiography. The ESD values for this procedure ranged 70.9-765.2 µGy (with the average value of 319.7 µGy). The broadest dose value range for children was related to the knee radiography. The range for children aged 5 years old was 11.8-95.8 µGy (with the average value of 48.9 µGy). CONCLUSIONS: It is essential to immediately implement X-ray room working procedures for the purpose of performing diagnostic examinations based on the existing model procedures. Med Pr 2016;67(3):321-326.

Assessing the dose values received by patients during conventional radiography X-ray examinations and the technical condition of the equipment used for this purpose.

BACKGROUND: X-ray examination is associated with patient exposure to ionizing radiation. Dose values depend on the type of medical procedure used, the X-ray unit technical condition and exposure conditions selected. The aim of this study was to determine the dose value received by patients during certain conventional radiography X-ray examinations and to assess the technical condition of medical equipment used for this purpose. MATERIAL AND METHODS: The study covered the total number of 118 conventional diagnostic X-ray units located in the Masovian Voivodeship. The methodology used to assess the conventional diagnostic X-ray unit technical condition and the measurement of the radiation dose rate received by patients are based on test procedures developed by the Department of Radiation Protection and Radiobiology of the National Institute of Public Health - National Institute of Hygiene (Warszawa, Poland) accredited for compliance with PN-EN 17025 standard by the Polish Centre for Accreditation. RESULTS: It was found that 84.7% of X-ray units fully meet the criteria set out in the Polish legislation regarding the safe use of ionizing radiation in medicine, while 15.3% of the units do not meet some of them. The broadest dose value range was recorded for adult patients. Particularly, during lateral (LATl) lumbar spine radiography the recorded entrance surface dose (ESD) values ranged from 283.5 to 7827 µGy (mean: 2183.3 µGy). CONCLUSIONS: It is absolutely necessary to constantly monitor the technical condition of all X-ray units, because it affects population exposure to ionizing radiation. Furthermore, it is essential to raise radiographers' awareness of the effects that ionizing radiation exposure can have on the human body.