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Journal Details
Format
Journal
eISSN
1898-0309
First Published
30 Dec 2008
Publication timeframe
4 times per year
Languages
English

Search

Volume 25 (2019): Issue 4 (December 2019)

Journal Details
Format
Journal
eISSN
1898-0309
First Published
30 Dec 2008
Publication timeframe
4 times per year
Languages
English

Search

6 Articles
Open Access

Nuclear reaction applied to fluorine depth profiles in human dental tissues

Published Online: 26 Dec 2019
Page range: 193 - 199

Abstract

Abstract

The nuclear reaction 19F(p, αγ)16O is presented as a valid method to measure the fluorine content in the first superficial layers of teeth. The analysis is performed in-vitro in extracted teeth, both healthy, fluorotic and decayed. It is performed irradiating the tooth with an energetic proton beam and analyzing the emitted high energy alpha particles. The quantitative analysis is performed comparing results with that of a standard sample at a known concentration. The depth profile of fluorine has a maximum content in the first superficial layers. The average concentrations in healthy enamel are of the order of 2 mg/g; it is of about 10 mg/g in fluorotic teeth, and below 0.1 mg/g in decayed teeth. The concentration in the dentine is about 50% lower than in the enamel and the concentrations decrease going from incisors to premolar and to molar teeth. Many results and a literature comparison are presented and discussed.

Keywords

  • nuclear reaction
  • fluorine
  • tooth
  • fluorine concentration in teeth
  • dental tissue
Open Access

Measurement of 238U, 232Th and 222Rn concentrations in different table oils samples. Determination of committed effective doses received by consumers following the ingestion of table oil.

Published Online: 26 Dec 2019
Page range: 201 - 209

Abstract

Abstract

The main objective of our work is to measure 238U, 232Th, 222Rn and 220Rn in different table oil samples using a method based on the use of two types of solid nuclear track detectors: CR- 39 and LR-115 II in order to determine the doses of radiation received by the individuals following ingestion of the samples of table oil studied. Indeed, we have developed an original method based on the determination of the detection efficiencies of CR-39 and LR-115 II solid nuclear track detectors for alpha particles emitted from the uranium 238 and thorium 232 series to evaluate 238U, 232Th, 222Rn and 220Rn concentrations in different table oil samples. We were able to determine doses of radiation due to 238U, 232Th and 222Rn received by individuals of the Moroccan, French, Italy, Spain and Tunisia populations following the ingestion of table oil.

The effective doses committed due to 238U, 232Th, and 222Rn following the ingestion of the table oil by the consumers were determined. The maximum total committed effective dose was found equal to (10±0.7) µSv·y−1 of the Moroccan population, (11.6±0.7) µSv·y−1 of the French population, (10.3±0.7) µSv.y−1 of the Italian population, (10.4±0.5) µSv·y−1 of the Spanish population and (10.5±0.7) µSv·y−1 of the Tunisian population is much lower than the average dose given by the United Nations Scientific Committee on the Effects of Atomic Radiation [1] for ingestion (0.2 to 0.8 mSv·y−1). The results obtained using our method are in very good agreement with those obtained using the model of the International Commission on Radiological Protection

Keywords

  • Table oil
  • radioactivity
  • nuclear track detectors
  • effective dose
  • health effects
Open Access

Investigation of fast neutron shielding properties of new polyurethane-based composites loaded with B4C, BeO, WO3, ZnO, and Gd2O3 micro-and nanoparticles

Published Online: 26 Dec 2019
Page range: 211 - 219

Abstract

Abstract

The aim of the current research was to study the radiation shielding properties of polyurethane-based shielding materials filled with B4C, BeO, WO3, ZnO, and Gd2O3 particles against fast neutrons. The macroscopic cross sections of composites containing micro- and nanoparticles with a diameter of 10 µm and 50 nm were calculated using MCNPX (2.6.0) Monte Carlo code. The results showed that adding nano-scaled fillers to polyurethane matrix increases attenuation properties of neutron shields compared to micro-scaled fillers for intermediate and fast neutrons. Among the studied composites, WO3 and Gd2O3 nano-composites presented higher neutron cross section compared to others.

Keywords

  • nanoparticles
  • shielding
  • fast neutrons
  • Monte Carlo method
Open Access

EPID – a useful interfraction QC tool

Published Online: 26 Dec 2019
Page range: 221 - 228

Abstract

Abstract

Biomedical accelerators used in radiotherapy are equipped with detector arrays which are commonly used to obtain the image of patient position during the treatment session. These devices use both kilovolt and megavolt x-ray beams. The advantage of EPID (Electronic Portal Imaging Device) megavolt panels is the correlation of the measured signal with the calibrated dose. The EPID gives a possibility to verify delivered dose. The aim of the study is to answer the question whether EPID can be useful as a tool for interfraction QC (quality control) of dose and geometry repeatability.

The EPID system has been calibrated according to the manufacturer’s recommendations to obtain a signal and dose values correlation. Initially, the uncertainty of the EPID matrix measurement was estimated. According to that, the detecting sensitivity of two parameters was checked: discrepancies between the planned and measured dose and field geometry variance. Moreover, the linearity of measured signal-dose function was evaluated.

In the second part of the work, an analysis of several dose distributions was performed. In this study, the analysis of clinical cases was limited to stereotactic dynamic radiotherapy. Fluence maps were obtained as a result of the dose distribution measurements with the EPID during treatment sessions. The compatibility of fluence maps was analyzed using the gamma index. The fluence map acquired during the first fraction was the reference one. The obtained results show that EPID system can be used for interfraction control of dose and geometry repeatability.

Keywords

  • EPID
  • gamma index
  • fluence map
Open Access

Correlation between age and head diameters in the paediatric patients during CT examination of the head

Published Online: 26 Dec 2019
Page range: 229 - 235

Abstract

Abstract

An estimate of patient dose, patient size should be used to normalise the output dose of CT machine in the terms of volume CT dose index, CTDIvol. There are two metrics to characterise the patient size, i.e. the effective diameter (Deff) and the water-equivalent diameter (Dw). These two metrics could be estimated by patient age. However, to date, relationships between the age and head patient size (Deff and Dw) have not been established for the pediatric patients. The aim of this study was to establish the relationships between the age and head patient size (Deff and the Dw) as the basis for calculating the size-specific dose estimate (SSDE) for paediatric head CT examination. The data were retrospectively collected from serial images of the CT head in the DICOM file from one hundred and thirteen paediatric patients aged 0-17 years (63 male and 50 female patients) underwent head CT examinations. The patient’s sizes (Deff and Dw) were calculated from the patient’s images using the IndoseCT version 15a software. The Deff and Dw values were correlated with age of patients using regression analysis. It was found that patient size (Deff and Dw) correlated well with the age of the patient with R2 more than 0.8. The size of the Dw is bigger than the Deff. The Deff values for male patients are 12.38 to 16.21 cm, and Dw values are 11.96 to 18.16 cm, respectively. For female patients, the values of Deff are from 11.54 to 16.87 cm, and the values of Dw are from 11.60 to 17.86 cm, respectively.

Keywords

  • effective diameter
  • water-equivalent diameter
  • paediatric head
  • SSDE
Open Access

Conductivity change with needle electrode during high frequency irreversible electroporation: a finite element study

Published Online: 26 Dec 2019
Page range: 237 - 242

Abstract

Abstract

Irreversible electroporation (IRE) is a process in which the cell membrane is damaged and leads to cell death. IRE has been used as a minimally invasive ablation tool. This process is affected by some factors. The most important factor is the electric field distribution inside the tissue. The electric field distribution depends on the electric pulse parameters and tissue properties, such as the electrical conductivity of tissue. The present study focuses on evaluating the tissue conductivity change due to high-frequency and low-voltage (HFLV) as well as low-frequency and high-voltage (LFHV) pulses during irreversible electroporation. We were used finite element analysis software, COMSOL Multiphysics 5.0, to calculate the conductivity change of the liver tissue. The HFLV pulses in this study involved 4000 bipolar and monopolar pulses with a frequency of 5 kHz, pulse width of 100 µs, and electric field intensity from 100 to 300 V/cm. On the other hand, the LFHV pulses, which we were used, included 8 bipolar and monopolar pulses with a frequency of 1 Hz, the pulse width of 2 ms and electric field intensity of 2500 V/cm. The results demonstrate that the conductivity change for LFHV pulses due to the greater electric field intensity was higher than for HFLV pulses. The most significant conclusion is the HFLV pulses can change tissue conductivity only in the vicinity of the tip of electrodes. While LFHV pulses change the electrical conductivity significantly in the tissue of between electrodes.

Keywords

  • irreversible electroporation
  • electric conductivity
  • high frequency
  • low voltage
  • finite element
6 Articles
Open Access

Nuclear reaction applied to fluorine depth profiles in human dental tissues

Published Online: 26 Dec 2019
Page range: 193 - 199

Abstract

Abstract

The nuclear reaction 19F(p, αγ)16O is presented as a valid method to measure the fluorine content in the first superficial layers of teeth. The analysis is performed in-vitro in extracted teeth, both healthy, fluorotic and decayed. It is performed irradiating the tooth with an energetic proton beam and analyzing the emitted high energy alpha particles. The quantitative analysis is performed comparing results with that of a standard sample at a known concentration. The depth profile of fluorine has a maximum content in the first superficial layers. The average concentrations in healthy enamel are of the order of 2 mg/g; it is of about 10 mg/g in fluorotic teeth, and below 0.1 mg/g in decayed teeth. The concentration in the dentine is about 50% lower than in the enamel and the concentrations decrease going from incisors to premolar and to molar teeth. Many results and a literature comparison are presented and discussed.

Keywords

  • nuclear reaction
  • fluorine
  • tooth
  • fluorine concentration in teeth
  • dental tissue
Open Access

Measurement of 238U, 232Th and 222Rn concentrations in different table oils samples. Determination of committed effective doses received by consumers following the ingestion of table oil.

Published Online: 26 Dec 2019
Page range: 201 - 209

Abstract

Abstract

The main objective of our work is to measure 238U, 232Th, 222Rn and 220Rn in different table oil samples using a method based on the use of two types of solid nuclear track detectors: CR- 39 and LR-115 II in order to determine the doses of radiation received by the individuals following ingestion of the samples of table oil studied. Indeed, we have developed an original method based on the determination of the detection efficiencies of CR-39 and LR-115 II solid nuclear track detectors for alpha particles emitted from the uranium 238 and thorium 232 series to evaluate 238U, 232Th, 222Rn and 220Rn concentrations in different table oil samples. We were able to determine doses of radiation due to 238U, 232Th and 222Rn received by individuals of the Moroccan, French, Italy, Spain and Tunisia populations following the ingestion of table oil.

The effective doses committed due to 238U, 232Th, and 222Rn following the ingestion of the table oil by the consumers were determined. The maximum total committed effective dose was found equal to (10±0.7) µSv·y−1 of the Moroccan population, (11.6±0.7) µSv·y−1 of the French population, (10.3±0.7) µSv.y−1 of the Italian population, (10.4±0.5) µSv·y−1 of the Spanish population and (10.5±0.7) µSv·y−1 of the Tunisian population is much lower than the average dose given by the United Nations Scientific Committee on the Effects of Atomic Radiation [1] for ingestion (0.2 to 0.8 mSv·y−1). The results obtained using our method are in very good agreement with those obtained using the model of the International Commission on Radiological Protection

Keywords

  • Table oil
  • radioactivity
  • nuclear track detectors
  • effective dose
  • health effects
Open Access

Investigation of fast neutron shielding properties of new polyurethane-based composites loaded with B4C, BeO, WO3, ZnO, and Gd2O3 micro-and nanoparticles

Published Online: 26 Dec 2019
Page range: 211 - 219

Abstract

Abstract

The aim of the current research was to study the radiation shielding properties of polyurethane-based shielding materials filled with B4C, BeO, WO3, ZnO, and Gd2O3 particles against fast neutrons. The macroscopic cross sections of composites containing micro- and nanoparticles with a diameter of 10 µm and 50 nm were calculated using MCNPX (2.6.0) Monte Carlo code. The results showed that adding nano-scaled fillers to polyurethane matrix increases attenuation properties of neutron shields compared to micro-scaled fillers for intermediate and fast neutrons. Among the studied composites, WO3 and Gd2O3 nano-composites presented higher neutron cross section compared to others.

Keywords

  • nanoparticles
  • shielding
  • fast neutrons
  • Monte Carlo method
Open Access

EPID – a useful interfraction QC tool

Published Online: 26 Dec 2019
Page range: 221 - 228

Abstract

Abstract

Biomedical accelerators used in radiotherapy are equipped with detector arrays which are commonly used to obtain the image of patient position during the treatment session. These devices use both kilovolt and megavolt x-ray beams. The advantage of EPID (Electronic Portal Imaging Device) megavolt panels is the correlation of the measured signal with the calibrated dose. The EPID gives a possibility to verify delivered dose. The aim of the study is to answer the question whether EPID can be useful as a tool for interfraction QC (quality control) of dose and geometry repeatability.

The EPID system has been calibrated according to the manufacturer’s recommendations to obtain a signal and dose values correlation. Initially, the uncertainty of the EPID matrix measurement was estimated. According to that, the detecting sensitivity of two parameters was checked: discrepancies between the planned and measured dose and field geometry variance. Moreover, the linearity of measured signal-dose function was evaluated.

In the second part of the work, an analysis of several dose distributions was performed. In this study, the analysis of clinical cases was limited to stereotactic dynamic radiotherapy. Fluence maps were obtained as a result of the dose distribution measurements with the EPID during treatment sessions. The compatibility of fluence maps was analyzed using the gamma index. The fluence map acquired during the first fraction was the reference one. The obtained results show that EPID system can be used for interfraction control of dose and geometry repeatability.

Keywords

  • EPID
  • gamma index
  • fluence map
Open Access

Correlation between age and head diameters in the paediatric patients during CT examination of the head

Published Online: 26 Dec 2019
Page range: 229 - 235

Abstract

Abstract

An estimate of patient dose, patient size should be used to normalise the output dose of CT machine in the terms of volume CT dose index, CTDIvol. There are two metrics to characterise the patient size, i.e. the effective diameter (Deff) and the water-equivalent diameter (Dw). These two metrics could be estimated by patient age. However, to date, relationships between the age and head patient size (Deff and Dw) have not been established for the pediatric patients. The aim of this study was to establish the relationships between the age and head patient size (Deff and the Dw) as the basis for calculating the size-specific dose estimate (SSDE) for paediatric head CT examination. The data were retrospectively collected from serial images of the CT head in the DICOM file from one hundred and thirteen paediatric patients aged 0-17 years (63 male and 50 female patients) underwent head CT examinations. The patient’s sizes (Deff and Dw) were calculated from the patient’s images using the IndoseCT version 15a software. The Deff and Dw values were correlated with age of patients using regression analysis. It was found that patient size (Deff and Dw) correlated well with the age of the patient with R2 more than 0.8. The size of the Dw is bigger than the Deff. The Deff values for male patients are 12.38 to 16.21 cm, and Dw values are 11.96 to 18.16 cm, respectively. For female patients, the values of Deff are from 11.54 to 16.87 cm, and the values of Dw are from 11.60 to 17.86 cm, respectively.

Keywords

  • effective diameter
  • water-equivalent diameter
  • paediatric head
  • SSDE
Open Access

Conductivity change with needle electrode during high frequency irreversible electroporation: a finite element study

Published Online: 26 Dec 2019
Page range: 237 - 242

Abstract

Abstract

Irreversible electroporation (IRE) is a process in which the cell membrane is damaged and leads to cell death. IRE has been used as a minimally invasive ablation tool. This process is affected by some factors. The most important factor is the electric field distribution inside the tissue. The electric field distribution depends on the electric pulse parameters and tissue properties, such as the electrical conductivity of tissue. The present study focuses on evaluating the tissue conductivity change due to high-frequency and low-voltage (HFLV) as well as low-frequency and high-voltage (LFHV) pulses during irreversible electroporation. We were used finite element analysis software, COMSOL Multiphysics 5.0, to calculate the conductivity change of the liver tissue. The HFLV pulses in this study involved 4000 bipolar and monopolar pulses with a frequency of 5 kHz, pulse width of 100 µs, and electric field intensity from 100 to 300 V/cm. On the other hand, the LFHV pulses, which we were used, included 8 bipolar and monopolar pulses with a frequency of 1 Hz, the pulse width of 2 ms and electric field intensity of 2500 V/cm. The results demonstrate that the conductivity change for LFHV pulses due to the greater electric field intensity was higher than for HFLV pulses. The most significant conclusion is the HFLV pulses can change tissue conductivity only in the vicinity of the tip of electrodes. While LFHV pulses change the electrical conductivity significantly in the tissue of between electrodes.

Keywords

  • irreversible electroporation
  • electric conductivity
  • high frequency
  • low voltage
  • finite element

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