Issues

Journal & Issues

Volume 28 (2022): Issue 4 (December 2022)

Volume 28 (2022): Issue 3 (September 2022)

Volume 28 (2022): Issue 2 (June 2022)

Volume 28 (2022): Issue 1 (March 2022)

Volume 27 (2021): Issue 4 (December 2021)

Volume 27 (2021): Issue 3 (September 2021)

Volume 27 (2021): Issue 2 (June 2021)

Volume 27 (2021): Issue 1 (March 2021)

Volume 26 (2020): Issue 4 (December 2020)

Volume 26 (2020): Issue 3 (September 2020)

Volume 26 (2020): Issue 2 (June 2020)

Volume 26 (2020): Issue 1 (March 2020)

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

Volume 25 (2019): Issue 3 (September 2019)

Volume 25 (2019): Issue 2 (June 2019)

Volume 25 (2019): Issue 1 (March 2019)

Volume 24 (2018): Issue 4 (December 2018)

Volume 24 (2018): Issue 3 (September 2018)

Volume 24 (2018): Issue 2 (June 2018)

Volume 24 (2018): Issue 1 (March 2018)

Volume 23 (2017): Issue 4 (December 2017)

Volume 23 (2017): Issue 3 (September 2017)

Volume 23 (2017): Issue 2 (June 2017)

Volume 23 (2017): Issue 1 (March 2017)

Volume 22 (2016): Issue 4 (December 2016)

Volume 22 (2016): Issue 3 (September 2016)

Volume 22 (2016): Issue 2 (June 2016)

Volume 22 (2016): Issue 1 (March 2016)

Volume 21 (2015): Issue 1 (December 2015)

Volume 20 (2014): Issue 1 (March 2014)

Volume 19 (2013): Issue 2 (December 2013)

Volume 19 (2013): Issue 1 (March 2013)

Volume 18 (2012): Issue 2 (June 2012)

Volume 18 (2012): Issue 1 (March 2012)

Volume 17 (2011): Issue 4 (December 2011)

Volume 17 (2011): Issue 3 (September 2011)

Volume 17 (2011): Issue 2 (June 2011)

Volume 17 (2011): Issue 1 (March 2011)

Volume 16 (2010): Issue 2 (June 2010)

Volume 16 (2010): Issue 1 (March 2010)

Volume 15 (2009): Issue 4 (December 2009)

Volume 15 (2009): Issue 3 (September 2009)

Volume 15 (2009): Issue 2 (June 2009)

Volume 15 (2009): Issue 1 (March 2009)

Volume 14 (2008): Issue 4 (December 2008)

Volume 14 (2008): Issue 3 (September 2008)

Volume 14 (2008): Issue 2 (June 2008)

Volume 14 (2008): Issue 1 (March 2008)

Volume 13 (2007): Issue 4 (December 2007)

Volume 13 (2007): Issue 3 (September 2007)

Volume 13 (2007): Issue 2 (June 2007)

Volume 13 (2007): Issue 1 (March 2007)

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

Search

Volume 27 (2021): Issue 1 (March 2021)

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

Search

14 Articles
Open Access

Uncertainties in the measurement of relative doses in radiotherapy

Published Online: 18 Mar 2021
Page range: 1 - 9

Abstract

Abstract

Both the measurement of the dose and the measurement of its distribution, like any other measurements, are subject to measurement uncertainties. These uncertainties affect all dose calculations and dose distributions in a patient’s body during treatment planning in radiotherapy. Measurement uncertainty is not a medical physicist’s error, but an inevitable element of their work. Planning the dose distribution in a patient’s body, we often try to reduce it in the volume of critical organs (OaR - Organ at Risk) or increase the minimum dose in the PTV region by a few percent. It is believed that the measurement uncertainty should be taken into account in these calculations at the stage of treatment planning. The paper presents the method of calculating the measurement uncertainty for different physical quantities in radiotherapy as percentage depth dose, profile function and output factor, due to the fact that these quantities have a particular impact on the calculated dose distributions in a patient’s body. The uncertainties that must be taken into account in planning treatment the planned dose per fraction and real in PTV, maybe different up to 4%.

Keywords

  • measurement uncertainty
  • standard dose
  • depth dose
  • beam profile
  • output factor
Open Access

Evaluation of dosimetric implications of Pareto and constrained mode of optimization for Monaco TPS generated VMAT plans in post operated carcinoma of the left breast

Published Online: 18 Mar 2021
Page range: 11 - 18

Abstract

Abstract

Intensity-modulated radiotherapy (IMRT) is being practiced for the last several years with a special approach for radiation therapy in post-mastectomy breast cancer patients. Meeting the cardiac dose constraints has always been a challenge during radiotherapy planning by both IMRT and VMAT (volumetric modulated arc therapy) of post-mastectomy left breast patients. With the advancement in IMRT planning techniques, it has been modified to VMAT with more degrees of freedom for modulation and is being utilised more frequently. This helps in obtaining a suitable plan for achieving both the dose homogeneity in target volume and dose constraints to Organ at Risk (OAR). 10 Patients with carcinoma of the left breast (post-mastectomy) were selected for this study. VMAT treatment plans for these patients were generated for 6 MV photons on the Monaco treatment planning system (TPS) using two types of optimization modes i.e. Pareto and Constrained mode available in Monaco TPS. For comparative dosimetric evaluation of the efficacy of these two types of optimization modes similar calculation algorithms, calculation grids, arcs, and beam sequencing parameters were used for generating treatment plans. The dosimetric quantities such as volume receiving more than 95% of the prescribed dose (V95), volume receiving more than 107% of the prescribed dose (V107) and Maximum dose (Dmax) for target volume, mean dose (Dmean) for heart, volume receiving more than 30 Gy (V30) volume receiving more than 20 Gy (V20) volume receiving more than 5 Gy (V5) for ipsilateral lung and total monitor units delivered were analysed for both optimization modes. A judicious mix of multiple planning parameters and variables using these two modes of optimization was applied and recorded. Both optimization modes yielded similar outcomes. However, Pareto mode has shown better coverage for planning target volume (PTV) with comparable doses to OARs.

Keywords

  • VMAT
  • optimization
  • constrained
  • Pareto
  • Monte-Carlo
Open Access

Evaluation of clinical implications in the use of dose to water versus dose to medium by using NTCP and TCP models for urinary bladder tumours

Published Online: 18 Mar 2021
Page range: 19 - 24

Abstract

Abstract

Purpose: To analyze the dosimetric and radiobiological differences between dose to water versus dose to medium for patients with carcinoma of the urinary bladder.

Materials and Methods: 15 patients with cancer of urinary bladder were selected for the study. VMAT plans were generated for each patient. The dose distributions were calculated in the modes dose to water and to medium with the Monaco treatment planning system. A dosimetric comparative analysis has been made between the two modes of planning in this study. Subsequently, NTCP and TCP were determined for OARs and targets respectively.

Results: The mean dose to 2 cc of the rectum, small bowel, left and right femoral heads respectively was higher by 0.8, 1.2, 2.7, and 2.2% for the dose to water calculation. Similarly, the mean dose to D2, D50, and D98 for PTV was higher by 0.4, 0.3, and 0.3% for dose to water calculation. Such small dose differences had little effect on the values of TCP and NTCP.

Conclusion: For patients with the urinary bladder there were very small differences between results between calculations carried out in dose to medium and dose to water modes.

Keywords

  • NTCP
  • TCP
  • radiobiological
  • toxicity
  • dosimetry
  • dose to water
  • dose to medium
Open Access

Applications and benefits of using gradient percentage depth dose instead of percentage depth dose for electron and photon beams in radiotherapy

Published Online: 18 Mar 2021
Page range: 25 - 29

Abstract

Abstract

Introduction: The aim of this study is to analyze the gradient of percentage depth dose for photon and electron beams of LINACs and to simplify the data set.

Materials and Methods: Dosimetry measurements were performed in accordance with Technical Reports Series No. 398 IAEA.

Results and discussion: The gradient of percentage depth dose was calculated and compared with the available published data.

Conclusion: Instead of percentage depth dose for increasing and decreasing parts, the findings suggest using only two numbers for specific gradient of dose, separately. In this way, they can replace the whole set of the percentage depth dose (PDD).

Keywords

  • beam
  • energy gradient
  • linear accelerator
Open Access

A tool for precise calculation of organ doses in voxelised geometries using GAMOS/Geant4 with a graphical user interface

Published Online: 18 Mar 2021
Page range: 31 - 40

Abstract

Abstract

Introduction: The limit of the method of calculating organ doses using voxelised phantoms with a Monte Carlo simulation code is that dose calculation errors in the boundaries of the organs are especially relevant for thin, small or complex geometries. In this report, we describe a tool that helps overcome this problem, accurately calculating organ doses by applying the “parallel geometry” utility feature of Geant4 through the GAMOS framework.

Methods and methods: We have tried to simplify the use of this tool by automatically processing the different DICOM image modalities (CT, PT, ST, NM), and by including the automatic conversion of the structures found in a DICOM RTSTRUCT file into Geant4 volumes that build the parallel geometry. For Nuclear Medicine applications, the DICOM PT, ST or NM images are converted into probabilities of generation of primary particles in each voxel, and the DICOM CT images into materials and material densities. For radiotherapy treatments, the DICOM RTPlan or RTIonPlan may also be used, hence the user only needs to describe the accelerator geometry. We also provide a Graphical User Interface for ease of use by for inexperienced users in Monte Carlo.

Results: We have tested the functionality of the tool with an I-131 thyroid cancer treatment, and obtained the expected energy deposition and dose differences, given that the particle source, geometry and structures are defined.

Conclusions: In summary, we provide an easy-to-use tool to calculate, with high accuracy, organ doses, taking into account their exact geometry as painted by the medical personnel on a voxelised phantom.

Keywords

  • organ dose
  • voxel phantom
  • Geant4
  • GAMOS
  • parallel geometry
Open Access

Evaluation of glandular dose in mammography in presence of breast cysts using Monte Carlo simulation

Published Online: 18 Mar 2021
Page range: 41 - 50

Abstract

Abstract

Background: Normalized glandular dose (DgN) is an important dosimetric quantity in mammography.

Aim: In this study, the effect of the presence of breast cysts and their size, number and location on DgN is evaluated.

Materials and methods: The effect of the presence of cysts in breast was examined using MCNPX code. This was performed by taking homogeneous breast phantoms containing spheroid breast cysts into account. The radius of the cysts, numbers of the cysts, and depth of the cysts, and their location were variable. Various electron energies were also considered. Finally, these results were compared with the results of a cyst-less breast phantom.

Results: The results show that the effect of the presence of cysts in the breast depends on the size, number and location of cysts. The presence of cysts at lower depths leads to a decrease in the DgN values, compared to the breast phantom without cysts. The presence of cysts in the breast phantom has an effect of -7 to +14 percent on the DgN values under the conditions considered in this modeling. This effect is independent of the X-ray tube voltage, the breast phantom thickness, and glandular ratio, and depends only on the number and size and location of the cysts. The bigger radius and number of cysts, the greater effect on DgN value.

Keywords

  • mammography
  • Monte Carlo simulation
  • normalized glandular dose
  • cysts
  • dosimetry
Open Access

Application of DQE for quantitative assessment of detectors to estimate AEC efficiency in digital mammography

Published Online: 18 Mar 2021
Page range: 51 - 56

Abstract

Abstract

Optimisation of the detector’s exposure parameters settings for image quality and patient dose is an important task in digital mammography. Assessment of a digital detector’s performance can be done objectively and without operator bias by determining the Detective Quantum Efficiency (DQE). The authors of this article aim to prove that the performance of the AEC system can be objectively portrayed through DQE. The results were examined for influence of KAD changes on DQE values and to determine if it was possible to obtain similar DQE values for different exposures. While analysing the effect of the operation of the AEC system described with DQE, the doses received by women during mammography examinations were considered, as well.

The AEC system’s exposure control mechanism cannot guarantee the same DQE value for different object thicknesses. When the object thickness increases, the AEC system should increase the KAD value to obtain the same DQE value. The result of increasing KAD would be the increase of mean glandular dose for some women. However, assuming that DQE is a good indicator of image quality, introducing the proposed changes to the AEC system’s operation would result in the same image quality for all breast thicknesses.

This approach to DQE use for AEC system evaluation is independent of the image processing procedure and can be the basis for changes to system calibration done by the manufacturer’s technical support team.

Keywords

  • DQE
  • AEC
  • mammography
Open Access

Automatic validation of the gantry tilt in a computed tomography scanner using a head polymethyl methacrylate phantom

Published Online: 18 Mar 2021
Page range: 57 - 62

Abstract

Abstract

The purpose of this study was to develop an automatic method for validating the computed tomography gantry tilt. A head polymethyl methacrylate phantom with a diameter of 16 cm was used. Gantry tilt angles were measured both manually and automatically. Manual measurements were performed by measuring the length of the anteroposterior and lateral diameters from acquired images using electronic calipers. Automatic measurements consisted of a number of steps: phantom segmentation, determination of the center of the phantom, measurement of the anteroposterior and lateral diameters, and computation of the gantry tilt angle. The method was implemented on the gantry angles from 0° to 15°. The proposed method of measuring gantry angles produced accurate gantry tilt angles. The differences with the angles displayed on the gantry were less than 1°. The results of the automatic method were the same as those of the manual method (R2 > 0.98).

Keywords

  • computed tomography
  • gantry tilt
  • polymethyl methacrylate phantom
  • automated method
  • quality control
Open Access

Study of the impact of clicks and murmurs on cardiac sounds S1 and S2 through bispectral analysis

Published Online: 18 Mar 2021
Page range: 63 - 72

Abstract

Abstract

This paper presents a study of the impact of clicks, and murmurs on cardiac sound S1, and S2, and the measure of severity degree through synchronization degree between frequencies, using bispectral analysis. The algorithm is applied on three groups of Phonocardiogram (PCG) signal: group A represents PCG signals having a morphology similar to that of the normal PCG signal without click or murmur, group B represents PCG signals with a click (reduced murmur), and group C represent PCG signals with murmurs.

The proposed algorithm permits us to evaluate and quantify the relationship between the two sounds S1 and S2 on one hand and between the two sounds, click and murmur on the other hand. The obtained results show that the clicks and murmurs can affect both the heart sounds, and vice versa. This study shows that the heart works in perfect harmony and that the frequencies of sounds S1, S2, clicks, and murmurs are not accidentally generated; but they are generated by the same generator system. It might also suggest that one of the obtained frequencies causes the others.

The proposed algorithm permits us also to determine the synchronization degree. It shows high values in group C; indicating high severity degrees, low values for group B, and zero in group A.

The algorithm is compared to Short-Time Fourier Transform (STFT) and continuous wavelet transform (CWT) analysis. Although the STFT can provide correctly the time, it can’t distinguish between the internal components of sounds S1 and S2, which are successfully determined by CWT, which, in turn, cannot find the relationship between them.

The algorithm was also evaluated and compared to the energetic ratio. the obtained results show very satisfactory results and very good discrimination between the three groups.

We can conclude that the three algorithms (STFT, CWT, and bispectral analysis) are complementary to facilitate a good approach and to better understand the cardiac sounds

Keywords

  • sound S1
  • sound S2
  • click
  • murmur
  • impact
  • bispectral
  • analysis
  • pathology
  • severity
Open Access

Preliminary study in the analysis of the severity of cardiac pathologies using the higher-order spectra on the heart-beats signals

Published Online: 18 Mar 2021
Page range: 73 - 85

Abstract

Abstract

Phonocardiography is a technique for recording and interpreting the mechanical activity of the heart. The recordings generated by such a technique are called phonocardiograms (PCG). The PCG signals are acoustic waves revealing a wealth of clinical information about cardiac health. They enable doctors to better understand heart sounds when presented visually. Hence, multiple approaches have been proposed to analyze heart sounds based on PCG recordings. Due to the complexity and the high nonlinear nature of these signals, a computer-aided technique based on higher-order statistics (HOS) is employed, it is known to be an important tool since it takes into account the non-linearity of the PCG signals. This method also known as the bispectrum technique, can provide significant information to enhance the diagnosis for an accurate and objective interpretation of heart condition.

The objective expected by this paper is to test in a preliminary way the parameters which can make it possible to establish a discrimination between the various signals of different pathologies and to characterize the cardiac abnormalities.

This preliminary study will be done on a reduced sample (nine signals) before applying it subsequently to a larger sample. This work examines the effectiveness of using the bispectrum technique in the analysis of the pathological severity of different PCG signals. The presented approach showed that HOS technique has a good potential for pathological discrimination of various PCG signals.

Keywords

  • phonocardiography
  • non-linearity
  • recordings
  • higher-order statistics
  • bispectrum
Open Access

Effects of detection system parameters on cross-correlations between MUAPs generated from parallel and inclined muscle fibres

Published Online: 18 Mar 2021
Page range: 87 - 97

Abstract

Abstract

The aim of this study was to investigate the effects of inter-electrode distance (IED), electrode radius (ER) and electrodes configurations on cross-correlation coefficient (CC) between motor unit action potentials (MUAPs) generated in a motor unit (MU) of parallel fibres and in a MU of inclined fibres with respect to the detection system. The fibres inclination angle (FIA) varied from 0° to 180° by a step of 5°. Six spatial filters (the longitudinal single differential (LSD), longitudinal double differential (LDD), bi-transversal double differential (BiTDD), normal double differential (NDD), an inverse binomial filter of order two (IB2) and maximum kurtosis filter (MKF)), three values of IED and three values of ER were considered.

A cylindrical multilayer volume conductor constituted by bone, muscle, fat and skin layers was used to simulate the MUAPs.

The cross-correlation coefficient analysis showed that with the increase of the FIA, the pairs of MUAPs detected by the IB2 system were more correlated than those detected by the five other systems. For each FIA, the findings also showed that the MUAPs pairs detected by BiTDD, NDD, IB2 and MKF systems were more correlated with smaller IEDs than with larger ones, while inverse results were found with the LSD and LDD systems. In addition, the pairs of MUAPs detected by the LDD, BiTDD, IB2 and MKF systems were more correlated with large ERs than with smaller ones. However, inverse results were found with the LSD and NDD systems.

Keywords

  • cross-correlation
  • electrodes
  • electromyography
  • fibres
  • inclination
Open Access

Optical investigation of bovine grey and white matters in visible and near-infrared ranges

Published Online: 18 Mar 2021
Page range: 99 - 107

Abstract

Abstract

Introduction: Due to enormous interests for laser in medicine and biology, optical properties characterization of different tissue have be affecting in development processes. In addition, the optical properties of biological tissues could be influenced by storage methods. Thus, optical properties of bovine white and grey tissues preserved by formalin have been characterized over a wide wavelength spectrum varied between 440 nm and 1000 nm.

Materials and Methods: To that end, a single integrating sphere system was assembled for spectroscopic characterization and an inverse adding-doubling algorithm was used to retrieve optical coefficients, i.e. reduced scattering and absorption coefficients.

Results: White matter has shown a strong scattering property in comparison to grey matter. On the other hand, the grey matter has absorbed light extensively. In comparison, the reduced scattering profile for both tissue types turned out to be consistent with prior works that characterized optical coefficients in vivo. On the contrary, absorption coefficient behavior has a different feature.

Conclusion: Formalin could change the tissue’s optical properties because of the alteration of tissue’s structure and components. The absence of hemoglobin that seeps out due to the use of a formalin could reduce the absorption coefficient over the visible range. Both the water replacement by formalin could reduce the refractive index of a stored tissue and the absence of hemoglobin that scatters light over the presented wavelength range should diminish the reduced scattering coefficients over that wavelength range.

Keywords

  • white matter
  • grey matter
  • reduced scattering
  • absorption
  • reduced albedo
Open Access

Evaluation of the performance of designed coaxial antennas for hyperthermia using simulation and experimental methods

Published Online: 18 Mar 2021
Page range: 109 - 117

Abstract

Abstract

Introduction: Antenna geometries and tissue properties affect microwave energy distributions during microwave ablation procedures. There is paucity information on the potential of antenna fabricated from a thick semi-rigid coaxial cable in the field of microwave thermal therapy. This study aimed at comparing the performance of two dual-slot antennas designed from different semi-rigid coaxial cables for the ablation of a liver tumour using numerical simulation and experimental validation methods.

Materials and Methods: COMSOL Multiphysics software was used for designing dual-slot antennas and as well as to evaluate microwave energy deposition and heat distribution in the liver tissue. Experimental validations were conducted on the ex-vivo bovine livers to validate the simulation results.

Results: Thick antenna developed in this study produced a higher sphericity index, larger ablation diameter and reduced backward heating along the antenna shaft than the existing one. The experimental validation results also indicate significant differences between the two antennas in terms of ablation diameters (p = 0.04), ablation lengths (p = 0.02) and aspect ratios (p = 0.02).

Conclusion: Based on the findings in this study, antenna fabricated from a thick coaxial cable has a higher potential of localizing microwave energy in the liver than conventional antennas.

Keywords

  • liver tumour
  • coaxial dual-slot antenna
  • microwave ablation
  • hyperthermia
Open Access

Reactor Laboratory for Biomedical Research in National Centre for Nuclear Research in Poland

Published Online: 18 Mar 2021
Page range: 119 - 122

Abstract

Abstract

National Centre for Nuclear Research, NCBJ is one of the biggest research institutes in Poland, in which scientists deal with basic research in the various fields of subatomic physics, development of nuclear technologies and practical applications of nuclear physics methods, including those for nuclear medicine and radiotherapy. NCBJ operates the only Polish nuclear research reactor MARIA, around which a Reactor Laboratory for Biomedical Research, RLBR has been built in the last 4 years.

One of the main aims of the RLBR team is to adapt the H2 channel, one of the eight MARIA’s horizontal channels, to a specific irradiation facility delivering a high flux thermal/epithermal neutron beam. The beam derived from the channel will be a tool for biological, physical and material studies for Boron Neutron Capture Therapy, BNCT.

While NCBJ is focused on building a neutron research facility, the Polish scientific community expressed its interest in BNCT development and implementation as an alternative therapy for cancer treatment. Through the working group meetings organized in the form of regular scientific workshops since 2015, it led to the establishment of a national scientific consortium dedicated to BNCT.

Polish Consortium for Boron Neutron Capture Therapy agreement was initially signed by twelve institutions including scientific institutes, universities and oncological centres in October 2019. National Centre for Nuclear Research was appointed the leader of the consortium. A year later the consortium was enlarged by two more institutions.

Keywords

  • BNCT
  • radiobiology
  • radiochemistry
  • neutron beam
  • research reactor
14 Articles
Open Access

Uncertainties in the measurement of relative doses in radiotherapy

Published Online: 18 Mar 2021
Page range: 1 - 9

Abstract

Abstract

Both the measurement of the dose and the measurement of its distribution, like any other measurements, are subject to measurement uncertainties. These uncertainties affect all dose calculations and dose distributions in a patient’s body during treatment planning in radiotherapy. Measurement uncertainty is not a medical physicist’s error, but an inevitable element of their work. Planning the dose distribution in a patient’s body, we often try to reduce it in the volume of critical organs (OaR - Organ at Risk) or increase the minimum dose in the PTV region by a few percent. It is believed that the measurement uncertainty should be taken into account in these calculations at the stage of treatment planning. The paper presents the method of calculating the measurement uncertainty for different physical quantities in radiotherapy as percentage depth dose, profile function and output factor, due to the fact that these quantities have a particular impact on the calculated dose distributions in a patient’s body. The uncertainties that must be taken into account in planning treatment the planned dose per fraction and real in PTV, maybe different up to 4%.

Keywords

  • measurement uncertainty
  • standard dose
  • depth dose
  • beam profile
  • output factor
Open Access

Evaluation of dosimetric implications of Pareto and constrained mode of optimization for Monaco TPS generated VMAT plans in post operated carcinoma of the left breast

Published Online: 18 Mar 2021
Page range: 11 - 18

Abstract

Abstract

Intensity-modulated radiotherapy (IMRT) is being practiced for the last several years with a special approach for radiation therapy in post-mastectomy breast cancer patients. Meeting the cardiac dose constraints has always been a challenge during radiotherapy planning by both IMRT and VMAT (volumetric modulated arc therapy) of post-mastectomy left breast patients. With the advancement in IMRT planning techniques, it has been modified to VMAT with more degrees of freedom for modulation and is being utilised more frequently. This helps in obtaining a suitable plan for achieving both the dose homogeneity in target volume and dose constraints to Organ at Risk (OAR). 10 Patients with carcinoma of the left breast (post-mastectomy) were selected for this study. VMAT treatment plans for these patients were generated for 6 MV photons on the Monaco treatment planning system (TPS) using two types of optimization modes i.e. Pareto and Constrained mode available in Monaco TPS. For comparative dosimetric evaluation of the efficacy of these two types of optimization modes similar calculation algorithms, calculation grids, arcs, and beam sequencing parameters were used for generating treatment plans. The dosimetric quantities such as volume receiving more than 95% of the prescribed dose (V95), volume receiving more than 107% of the prescribed dose (V107) and Maximum dose (Dmax) for target volume, mean dose (Dmean) for heart, volume receiving more than 30 Gy (V30) volume receiving more than 20 Gy (V20) volume receiving more than 5 Gy (V5) for ipsilateral lung and total monitor units delivered were analysed for both optimization modes. A judicious mix of multiple planning parameters and variables using these two modes of optimization was applied and recorded. Both optimization modes yielded similar outcomes. However, Pareto mode has shown better coverage for planning target volume (PTV) with comparable doses to OARs.

Keywords

  • VMAT
  • optimization
  • constrained
  • Pareto
  • Monte-Carlo
Open Access

Evaluation of clinical implications in the use of dose to water versus dose to medium by using NTCP and TCP models for urinary bladder tumours

Published Online: 18 Mar 2021
Page range: 19 - 24

Abstract

Abstract

Purpose: To analyze the dosimetric and radiobiological differences between dose to water versus dose to medium for patients with carcinoma of the urinary bladder.

Materials and Methods: 15 patients with cancer of urinary bladder were selected for the study. VMAT plans were generated for each patient. The dose distributions were calculated in the modes dose to water and to medium with the Monaco treatment planning system. A dosimetric comparative analysis has been made between the two modes of planning in this study. Subsequently, NTCP and TCP were determined for OARs and targets respectively.

Results: The mean dose to 2 cc of the rectum, small bowel, left and right femoral heads respectively was higher by 0.8, 1.2, 2.7, and 2.2% for the dose to water calculation. Similarly, the mean dose to D2, D50, and D98 for PTV was higher by 0.4, 0.3, and 0.3% for dose to water calculation. Such small dose differences had little effect on the values of TCP and NTCP.

Conclusion: For patients with the urinary bladder there were very small differences between results between calculations carried out in dose to medium and dose to water modes.

Keywords

  • NTCP
  • TCP
  • radiobiological
  • toxicity
  • dosimetry
  • dose to water
  • dose to medium
Open Access

Applications and benefits of using gradient percentage depth dose instead of percentage depth dose for electron and photon beams in radiotherapy

Published Online: 18 Mar 2021
Page range: 25 - 29

Abstract

Abstract

Introduction: The aim of this study is to analyze the gradient of percentage depth dose for photon and electron beams of LINACs and to simplify the data set.

Materials and Methods: Dosimetry measurements were performed in accordance with Technical Reports Series No. 398 IAEA.

Results and discussion: The gradient of percentage depth dose was calculated and compared with the available published data.

Conclusion: Instead of percentage depth dose for increasing and decreasing parts, the findings suggest using only two numbers for specific gradient of dose, separately. In this way, they can replace the whole set of the percentage depth dose (PDD).

Keywords

  • beam
  • energy gradient
  • linear accelerator
Open Access

A tool for precise calculation of organ doses in voxelised geometries using GAMOS/Geant4 with a graphical user interface

Published Online: 18 Mar 2021
Page range: 31 - 40

Abstract

Abstract

Introduction: The limit of the method of calculating organ doses using voxelised phantoms with a Monte Carlo simulation code is that dose calculation errors in the boundaries of the organs are especially relevant for thin, small or complex geometries. In this report, we describe a tool that helps overcome this problem, accurately calculating organ doses by applying the “parallel geometry” utility feature of Geant4 through the GAMOS framework.

Methods and methods: We have tried to simplify the use of this tool by automatically processing the different DICOM image modalities (CT, PT, ST, NM), and by including the automatic conversion of the structures found in a DICOM RTSTRUCT file into Geant4 volumes that build the parallel geometry. For Nuclear Medicine applications, the DICOM PT, ST or NM images are converted into probabilities of generation of primary particles in each voxel, and the DICOM CT images into materials and material densities. For radiotherapy treatments, the DICOM RTPlan or RTIonPlan may also be used, hence the user only needs to describe the accelerator geometry. We also provide a Graphical User Interface for ease of use by for inexperienced users in Monte Carlo.

Results: We have tested the functionality of the tool with an I-131 thyroid cancer treatment, and obtained the expected energy deposition and dose differences, given that the particle source, geometry and structures are defined.

Conclusions: In summary, we provide an easy-to-use tool to calculate, with high accuracy, organ doses, taking into account their exact geometry as painted by the medical personnel on a voxelised phantom.

Keywords

  • organ dose
  • voxel phantom
  • Geant4
  • GAMOS
  • parallel geometry
Open Access

Evaluation of glandular dose in mammography in presence of breast cysts using Monte Carlo simulation

Published Online: 18 Mar 2021
Page range: 41 - 50

Abstract

Abstract

Background: Normalized glandular dose (DgN) is an important dosimetric quantity in mammography.

Aim: In this study, the effect of the presence of breast cysts and their size, number and location on DgN is evaluated.

Materials and methods: The effect of the presence of cysts in breast was examined using MCNPX code. This was performed by taking homogeneous breast phantoms containing spheroid breast cysts into account. The radius of the cysts, numbers of the cysts, and depth of the cysts, and their location were variable. Various electron energies were also considered. Finally, these results were compared with the results of a cyst-less breast phantom.

Results: The results show that the effect of the presence of cysts in the breast depends on the size, number and location of cysts. The presence of cysts at lower depths leads to a decrease in the DgN values, compared to the breast phantom without cysts. The presence of cysts in the breast phantom has an effect of -7 to +14 percent on the DgN values under the conditions considered in this modeling. This effect is independent of the X-ray tube voltage, the breast phantom thickness, and glandular ratio, and depends only on the number and size and location of the cysts. The bigger radius and number of cysts, the greater effect on DgN value.

Keywords

  • mammography
  • Monte Carlo simulation
  • normalized glandular dose
  • cysts
  • dosimetry
Open Access

Application of DQE for quantitative assessment of detectors to estimate AEC efficiency in digital mammography

Published Online: 18 Mar 2021
Page range: 51 - 56

Abstract

Abstract

Optimisation of the detector’s exposure parameters settings for image quality and patient dose is an important task in digital mammography. Assessment of a digital detector’s performance can be done objectively and without operator bias by determining the Detective Quantum Efficiency (DQE). The authors of this article aim to prove that the performance of the AEC system can be objectively portrayed through DQE. The results were examined for influence of KAD changes on DQE values and to determine if it was possible to obtain similar DQE values for different exposures. While analysing the effect of the operation of the AEC system described with DQE, the doses received by women during mammography examinations were considered, as well.

The AEC system’s exposure control mechanism cannot guarantee the same DQE value for different object thicknesses. When the object thickness increases, the AEC system should increase the KAD value to obtain the same DQE value. The result of increasing KAD would be the increase of mean glandular dose for some women. However, assuming that DQE is a good indicator of image quality, introducing the proposed changes to the AEC system’s operation would result in the same image quality for all breast thicknesses.

This approach to DQE use for AEC system evaluation is independent of the image processing procedure and can be the basis for changes to system calibration done by the manufacturer’s technical support team.

Keywords

  • DQE
  • AEC
  • mammography
Open Access

Automatic validation of the gantry tilt in a computed tomography scanner using a head polymethyl methacrylate phantom

Published Online: 18 Mar 2021
Page range: 57 - 62

Abstract

Abstract

The purpose of this study was to develop an automatic method for validating the computed tomography gantry tilt. A head polymethyl methacrylate phantom with a diameter of 16 cm was used. Gantry tilt angles were measured both manually and automatically. Manual measurements were performed by measuring the length of the anteroposterior and lateral diameters from acquired images using electronic calipers. Automatic measurements consisted of a number of steps: phantom segmentation, determination of the center of the phantom, measurement of the anteroposterior and lateral diameters, and computation of the gantry tilt angle. The method was implemented on the gantry angles from 0° to 15°. The proposed method of measuring gantry angles produced accurate gantry tilt angles. The differences with the angles displayed on the gantry were less than 1°. The results of the automatic method were the same as those of the manual method (R2 > 0.98).

Keywords

  • computed tomography
  • gantry tilt
  • polymethyl methacrylate phantom
  • automated method
  • quality control
Open Access

Study of the impact of clicks and murmurs on cardiac sounds S1 and S2 through bispectral analysis

Published Online: 18 Mar 2021
Page range: 63 - 72

Abstract

Abstract

This paper presents a study of the impact of clicks, and murmurs on cardiac sound S1, and S2, and the measure of severity degree through synchronization degree between frequencies, using bispectral analysis. The algorithm is applied on three groups of Phonocardiogram (PCG) signal: group A represents PCG signals having a morphology similar to that of the normal PCG signal without click or murmur, group B represents PCG signals with a click (reduced murmur), and group C represent PCG signals with murmurs.

The proposed algorithm permits us to evaluate and quantify the relationship between the two sounds S1 and S2 on one hand and between the two sounds, click and murmur on the other hand. The obtained results show that the clicks and murmurs can affect both the heart sounds, and vice versa. This study shows that the heart works in perfect harmony and that the frequencies of sounds S1, S2, clicks, and murmurs are not accidentally generated; but they are generated by the same generator system. It might also suggest that one of the obtained frequencies causes the others.

The proposed algorithm permits us also to determine the synchronization degree. It shows high values in group C; indicating high severity degrees, low values for group B, and zero in group A.

The algorithm is compared to Short-Time Fourier Transform (STFT) and continuous wavelet transform (CWT) analysis. Although the STFT can provide correctly the time, it can’t distinguish between the internal components of sounds S1 and S2, which are successfully determined by CWT, which, in turn, cannot find the relationship between them.

The algorithm was also evaluated and compared to the energetic ratio. the obtained results show very satisfactory results and very good discrimination between the three groups.

We can conclude that the three algorithms (STFT, CWT, and bispectral analysis) are complementary to facilitate a good approach and to better understand the cardiac sounds

Keywords

  • sound S1
  • sound S2
  • click
  • murmur
  • impact
  • bispectral
  • analysis
  • pathology
  • severity
Open Access

Preliminary study in the analysis of the severity of cardiac pathologies using the higher-order spectra on the heart-beats signals

Published Online: 18 Mar 2021
Page range: 73 - 85

Abstract

Abstract

Phonocardiography is a technique for recording and interpreting the mechanical activity of the heart. The recordings generated by such a technique are called phonocardiograms (PCG). The PCG signals are acoustic waves revealing a wealth of clinical information about cardiac health. They enable doctors to better understand heart sounds when presented visually. Hence, multiple approaches have been proposed to analyze heart sounds based on PCG recordings. Due to the complexity and the high nonlinear nature of these signals, a computer-aided technique based on higher-order statistics (HOS) is employed, it is known to be an important tool since it takes into account the non-linearity of the PCG signals. This method also known as the bispectrum technique, can provide significant information to enhance the diagnosis for an accurate and objective interpretation of heart condition.

The objective expected by this paper is to test in a preliminary way the parameters which can make it possible to establish a discrimination between the various signals of different pathologies and to characterize the cardiac abnormalities.

This preliminary study will be done on a reduced sample (nine signals) before applying it subsequently to a larger sample. This work examines the effectiveness of using the bispectrum technique in the analysis of the pathological severity of different PCG signals. The presented approach showed that HOS technique has a good potential for pathological discrimination of various PCG signals.

Keywords

  • phonocardiography
  • non-linearity
  • recordings
  • higher-order statistics
  • bispectrum
Open Access

Effects of detection system parameters on cross-correlations between MUAPs generated from parallel and inclined muscle fibres

Published Online: 18 Mar 2021
Page range: 87 - 97

Abstract

Abstract

The aim of this study was to investigate the effects of inter-electrode distance (IED), electrode radius (ER) and electrodes configurations on cross-correlation coefficient (CC) between motor unit action potentials (MUAPs) generated in a motor unit (MU) of parallel fibres and in a MU of inclined fibres with respect to the detection system. The fibres inclination angle (FIA) varied from 0° to 180° by a step of 5°. Six spatial filters (the longitudinal single differential (LSD), longitudinal double differential (LDD), bi-transversal double differential (BiTDD), normal double differential (NDD), an inverse binomial filter of order two (IB2) and maximum kurtosis filter (MKF)), three values of IED and three values of ER were considered.

A cylindrical multilayer volume conductor constituted by bone, muscle, fat and skin layers was used to simulate the MUAPs.

The cross-correlation coefficient analysis showed that with the increase of the FIA, the pairs of MUAPs detected by the IB2 system were more correlated than those detected by the five other systems. For each FIA, the findings also showed that the MUAPs pairs detected by BiTDD, NDD, IB2 and MKF systems were more correlated with smaller IEDs than with larger ones, while inverse results were found with the LSD and LDD systems. In addition, the pairs of MUAPs detected by the LDD, BiTDD, IB2 and MKF systems were more correlated with large ERs than with smaller ones. However, inverse results were found with the LSD and NDD systems.

Keywords

  • cross-correlation
  • electrodes
  • electromyography
  • fibres
  • inclination
Open Access

Optical investigation of bovine grey and white matters in visible and near-infrared ranges

Published Online: 18 Mar 2021
Page range: 99 - 107

Abstract

Abstract

Introduction: Due to enormous interests for laser in medicine and biology, optical properties characterization of different tissue have be affecting in development processes. In addition, the optical properties of biological tissues could be influenced by storage methods. Thus, optical properties of bovine white and grey tissues preserved by formalin have been characterized over a wide wavelength spectrum varied between 440 nm and 1000 nm.

Materials and Methods: To that end, a single integrating sphere system was assembled for spectroscopic characterization and an inverse adding-doubling algorithm was used to retrieve optical coefficients, i.e. reduced scattering and absorption coefficients.

Results: White matter has shown a strong scattering property in comparison to grey matter. On the other hand, the grey matter has absorbed light extensively. In comparison, the reduced scattering profile for both tissue types turned out to be consistent with prior works that characterized optical coefficients in vivo. On the contrary, absorption coefficient behavior has a different feature.

Conclusion: Formalin could change the tissue’s optical properties because of the alteration of tissue’s structure and components. The absence of hemoglobin that seeps out due to the use of a formalin could reduce the absorption coefficient over the visible range. Both the water replacement by formalin could reduce the refractive index of a stored tissue and the absence of hemoglobin that scatters light over the presented wavelength range should diminish the reduced scattering coefficients over that wavelength range.

Keywords

  • white matter
  • grey matter
  • reduced scattering
  • absorption
  • reduced albedo
Open Access

Evaluation of the performance of designed coaxial antennas for hyperthermia using simulation and experimental methods

Published Online: 18 Mar 2021
Page range: 109 - 117

Abstract

Abstract

Introduction: Antenna geometries and tissue properties affect microwave energy distributions during microwave ablation procedures. There is paucity information on the potential of antenna fabricated from a thick semi-rigid coaxial cable in the field of microwave thermal therapy. This study aimed at comparing the performance of two dual-slot antennas designed from different semi-rigid coaxial cables for the ablation of a liver tumour using numerical simulation and experimental validation methods.

Materials and Methods: COMSOL Multiphysics software was used for designing dual-slot antennas and as well as to evaluate microwave energy deposition and heat distribution in the liver tissue. Experimental validations were conducted on the ex-vivo bovine livers to validate the simulation results.

Results: Thick antenna developed in this study produced a higher sphericity index, larger ablation diameter and reduced backward heating along the antenna shaft than the existing one. The experimental validation results also indicate significant differences between the two antennas in terms of ablation diameters (p = 0.04), ablation lengths (p = 0.02) and aspect ratios (p = 0.02).

Conclusion: Based on the findings in this study, antenna fabricated from a thick coaxial cable has a higher potential of localizing microwave energy in the liver than conventional antennas.

Keywords

  • liver tumour
  • coaxial dual-slot antenna
  • microwave ablation
  • hyperthermia
Open Access

Reactor Laboratory for Biomedical Research in National Centre for Nuclear Research in Poland

Published Online: 18 Mar 2021
Page range: 119 - 122

Abstract

Abstract

National Centre for Nuclear Research, NCBJ is one of the biggest research institutes in Poland, in which scientists deal with basic research in the various fields of subatomic physics, development of nuclear technologies and practical applications of nuclear physics methods, including those for nuclear medicine and radiotherapy. NCBJ operates the only Polish nuclear research reactor MARIA, around which a Reactor Laboratory for Biomedical Research, RLBR has been built in the last 4 years.

One of the main aims of the RLBR team is to adapt the H2 channel, one of the eight MARIA’s horizontal channels, to a specific irradiation facility delivering a high flux thermal/epithermal neutron beam. The beam derived from the channel will be a tool for biological, physical and material studies for Boron Neutron Capture Therapy, BNCT.

While NCBJ is focused on building a neutron research facility, the Polish scientific community expressed its interest in BNCT development and implementation as an alternative therapy for cancer treatment. Through the working group meetings organized in the form of regular scientific workshops since 2015, it led to the establishment of a national scientific consortium dedicated to BNCT.

Polish Consortium for Boron Neutron Capture Therapy agreement was initially signed by twelve institutions including scientific institutes, universities and oncological centres in October 2019. National Centre for Nuclear Research was appointed the leader of the consortium. A year later the consortium was enlarged by two more institutions.

Keywords

  • BNCT
  • radiobiology
  • radiochemistry
  • neutron beam
  • research reactor

Plan your remote conference with Sciendo