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See detailA parametric study of occupational radiation dose in interventional radiology by Monte-Carlo simulations
Abdelrahman, Mahmoud Eid Mahmoud ULiege; Lombardo, Pasquale; Camp, Anna et al

in Physica Medica-European Journal of Medical Physics (in press)

This paper presents the results of a parametric study on the occupational exposure in interventional radiology to explore the influence of various variables on the staff doses. These variables include the ... [more ▼]

This paper presents the results of a parametric study on the occupational exposure in interventional radiology to explore the influence of various variables on the staff doses. These variables include the angiography beam settings: x-ray peak voltage (kVp), added copper filtration, field diameter, beam projection and source to detector distance. The study was performed using Monte-Carlo simulations with MCNPX for more than 5600 combinations of parameters that account for different clinical situations. Additionally, the analysis of the results was performed using both multiple and random forest regression to build a predictive model and to quantify the importance of each variable when the variables simultaneously change. Primary and secondary projections were found to have the most effect on the scatter fraction that reaches the operator followed by the effect of changing the x-ray beam quality. The effect of changing the source to image intensifier distance had the lowest effect. [less ▲]

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See detailPersonal dosimetry of workers without a physical dosemeter using computational methods
Abdelrahman, Mahmoud Eid Mahmoud ULiege

Doctoral thesis (2020)

Monitoring the individual exposure of workers constitutes an integral part of any radiation protection program. Individual monitoring of exposed workers to external ionizing radiation is essential in ... [more ▼]

Monitoring the individual exposure of workers constitutes an integral part of any radiation protection program. Individual monitoring of exposed workers to external ionizing radiation is essential in order to ensure safe and satisfactory working conditions; demonstrate compliance with dose limits and the application of the ALARA principle. At present, personal dosimetry is typically performed by issuing staff with physical dosimeters. These physical measurement devices are part of routine practice, but still have many limitations, both from a practical and from a metrological point of view. The results are usually known only after some delay (30-60 days) with passive dosimeters. In addition, performing precise and reliable personal dose measurements in all types of workplaces is quite difficult. There are issues with compliance and multiple dosimeters can be mixed up or worn incorrectly. The number and positioning of individual dosimeters is becoming more complex with the new focus on eye lens dosimetry. Also, the uncertainties with the present dosimeters are not negligible. An uncertainty factor of 2 is accepted as good practice for low doses and for neutron fields in particular the uncertainties are even higher. On the other hand, computational techniques are evolving rapidly. In the past, simplified mathematical phantoms were used, while now very detailed voxel and mesh phantoms are available. In addition, with increasing computational power, such calculations can be performed faster and faster. The objective of this thesis work is to improve occupational dosimetry by an innovative approach: the development of a computational dosimetry application based on Monte-Carlo (MC) simulations without the use of physical dosimeters. This is done using a combination of (i) monitoring of the position of workers in real time and (ii) the spatial radiation field, including its energy and angular distribution. With this input, the doses of the workers can be simulated or calculated. The methodology was applied and validated for two situations where improvements in dosimetry are urgently needed: neutron and interventional radiology workplaces. Human motion tracking system was developed to monitor worker’s movements. The movement of the worker is then used to animate an anthropomorphic flexible computational phantom. As regards interventional radiology workplaces, the required information and data sources have been identified. In particular, for the calculations the most reliable way to gather the required information is from the Radiation Dose Structured Report (RDSR). For neutron fields, the radiation field map of the workplace can be based on analytical calculations or more advanced MC calculations. This proposed methodology for personal dosimetry for workers is very innovative and challenging. It explores a new direction in personal dosimetry and, as such, adds value to the radiation protection community and regulatory system. In addition, the proposed approach can be used for ALARA optimization, as well as for education and training activities. [less ▲]

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See detailFirst steps towards online Personal Dosimetry Using Computational Methods in Interventional Radiology: operator’s position tracking and simulation input generation
Abdelrahman, Mahmoud Eid Mahmoud ULiege; Lombardo, Pasquale; Vanhavere, Filip et al

in Radiation Physics and Chemistry (2020, January 16)

Introduction <br />With this work we present an innovative system for calculating occupational doses, as it is now being developed within the PODIUM (Personal Online DosImetry Using computational Methods ... [more ▼]

Introduction <br />With this work we present an innovative system for calculating occupational doses, as it is now being developed within the PODIUM (Personal Online DosImetry Using computational Methods) project. Individual monitoring of workers is essential to follow up regulatory dose limits and to apply the ALARA principle. However, current personal dosimeters are subject to large uncertainties, especially in non-homogeneous fields, like those found interventional radiology/cardiology. Workers in these fields also need to wear several dosimeters (extremity, eye lens, above/below apron), which causes practical problems. As the capabilities of computational methods are increasing exponentially, it will become feasible to use pure computations to calculate doses in place of physical dosimeters. <br /> <br />Methods <br />In our concept system, operational and protection quantities are calculated by fast Monte Carlo methods. Our dose calculation accounts for the real radiation field (including fluence, energy and angular distributions) and for the relative position of different body parts of the worker. The real movements of exposed workers are captured using depth cameras. This information is translated to a flexible anthropomorphic phantom, and then in Monte-Carlo simulations. For the moment this is done off-line, after the procedure is finished, and the parameters of the procedure are collected. <br /> <br />Results <br />For validating our system, we performed tests in interventional radiology (IR) rooms. In total, we followed 15 procedures in Cath-labs at UZ-VUB and CHU- Liège. An accurate analysis of the staff position was performed, and as a first step, we compared simulated Hp(10) and measured Hp(10) with electronic personal dosimeter (EPD) during an angiography procedure for some of these procedures. The results showed good agreement between the calculated doses and the ones measured by the EPD dosimeter. <br /> <br />Conclusions <br />With this work, we show that simulating worker doses based on tracking systems and flexible phantoms is possible. This method has big advantages in interventional radiology workplaces where the fields are non-homogeneous and doses to staff can be relatively high. This method can also help in ALARA applications and for education and training. [less ▲]

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See detailPersonal dose computation using monitoring systems and 3D cameras
Abdelrahman, Mahmoud Eid Mahmoud ULiege; Lombardo, Pasquale; Van Hoey, Olivier ULiege et al

Conference (2019, November 27)

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See detailPersonal Online DosImetry Using CoMputational Methods
Abdelrahman, Mahmoud Eid Mahmoud ULiege; Lombardo, Pasquale; Vanhoey, Olivier et al

Scientific conference (2019, October 11)

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See detailPodium - Personal online dosimetry using computational methods
Abdelrahman, Mahmoud Eid Mahmoud ULiege; Seret, Alain ULiege; Phillips, Christophe ULiege et al

Scientific conference (2019, October 11)

Individual monitoring of radiation workers is essential to ensure compliance with official dose limits and to allow application of the ALARA principle. Routine monitoring of staff is usually performed by ... [more ▼]

Individual monitoring of radiation workers is essential to ensure compliance with official dose limits and to allow application of the ALARA principle. Routine monitoring of staff is usually performed by means of passive dosimeters. However, current personal dosimeters are subject to large uncertainties, especially in heterogeneous fields, like those found in interventional radiology (IR). Within the PODIUM (Personal Online DosImetry Using computational Methods) research project, a user-friendly application was developed based on MCNP Monte-Carlo code to calculate doses to the staff in IR. The application uses both the data of motion tracking system to generate the position of the operator and the data from the Radiation Dose Structure Report (RDSR) from the imaging device to generate time-dependent parameters of the radiation source. The results of the first clinical validation of the system show good agreement within 10-40% between simulated Hp(10) with MCNP and measured Hp(10) with electronic personal dosimeter worn above the lead apron. Some challenges and limitations remain, however, the results from the two-year proof-of-concept PODIUM project are promising. We have shown that the technology is now available for tracking staff position and calculating their dose using detailed phantoms, without the need to wear an individual dosimeter. [less ▲]

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See detailDevelopment and Validation of Online Personal Dosimetry Application Using Computational Method for Interventional Cardiology
Abdelrahman, Mahmoud Eid Mahmoud ULiege; Seret, Alain ULiege; Phillips, Christophe ULiege et al

Conference (2019, June 20)

Introduction Interventional cardiologists are often occupationally exposed to low radiation doses which put them at risk of stochastic radiation induced detriments. Therefore, individual monitoring of ... [more ▼]

Introduction Interventional cardiologists are often occupationally exposed to low radiation doses which put them at risk of stochastic radiation induced detriments. Therefore, individual monitoring of medical staff is essential to follow up regulatory dose limits and to apply the ALARA principle. However, current personal dosimeters are subject to large uncertainties, especially in non-homogeneous fields, like those found interventional radiology/cardiology. In these workplaces, medical staff should wear several dosimeters (extremity, eye lens, above/below apron) for a proper monitoring. However, the use of multiple dosimeters is unpractical, and in some cases it could hinder the work of the physicians (like in the case of finger dosimeters). As the capabilities of computational methods are increasing exponentially, it will become feasible to use pure computations to calculate doses in place of physical dosimeters. With this work, we present the current state of development of an innovative tool for calculating occupational doses using Monte-Carlo methods. The system is being developed within the PODIUM (Personal Online DosImetry Using computational Methods) research project. Materials & Methods In typical interventional radiology/cardiology scenarios, operators are exposed to non-homogeneous scatter radiation field coming from the body of the patient. The anisotropy is higher while working close by to the patient for performing manipulations. The two main inputs to our computational dosimetry system are: a) the spatiotemporal distribution of the scattered radiation field, including its intensity, its energy and its angular distributions; b) the relative position and pose of the operator in the scatter field. 1. Radiation field parameters. The scatter radiation is dependent on a number of factors such as: primary beam intensity, beam projection angle and patient thickness. Acquiring information about the primary beam and the patient can help reproducing the scatter field computationally. Imaging parameters includes kVp, filtration, collimation and beam projection are used to simulate the primary beam and its scattered field in Monte-Carlo simulations. At this stage, such information is obtained from a summary dose report after each procedure. The measured dose-area product (DAP) value allows to normalize the simulated relative doses (eV/g per particle) to the equivalent absolute dose units. 2. Operator motion tracking. The main input to compute doses to operators is the position and pose of the body of the operator relative to the X-ray beam and to the patient. Our system provides an indoor tracking system for tracking the position and the posture of the workers. The system is constituted by a Microsoft Kinect v2 Time-Of-Flight (TOF) camera and by an acquisition software package. The body skeleton information provided by the tracking system is then used to position a phantom. At the current stage, the system represents a proof-of-concept and calculations are done off-line, after the procedure is finished, and the parameters of the procedure are collected. For validating our system, we performed tests in two interventional radiology (IR) rooms. In total, we followed 15 procedures in Cath-labs at UZ-VUB and CHU- ULiège hospitals. The Monte Carlo N-particle code (MCNPX 2.7) code [1] is used in our method for modelling and dosimetry calculations. The body skeleton information of the main operator provided by the tracking system is used to estimate the position of a dosimeter on the chest level in the simulations. Results An accurate analysis of the staff position was performed, and as a first step, we compared simulated Hp(10) with MCNP and measured Hp(10) with electronic personal dosimeter (EPD) Mk2.3 from Thermo Fisher Scientific worn above the lead apron during an angiography procedure for some of these procedures. The results showed good agreement with less than 5% difference between the calculated doses and the ones measured by the EPD dosimeter. The differences found in our simulations are easily explained by the uncertainties of the EPD dosemeter. In fact, the study performed by Clairand et al. [2] showed that the EPD Mk2.3 has a variation on the response within 30-40% due to the energy and angular response with the effect of the pulse frequency of the x-ray beam in interventional radiology fields. In addition, simulations provided extra information about the eye lens dose Hp(3) to the operator during one procedure which shows the high spread of the ratio Hp(3)/Hp(10) between 0.48 to 1.75 for different beam projections due to field inhomogeneity. Conclusions and future work With this work, we show that simulating worker doses based on tracking systems and flexible phantoms in Monte-Carlo codes is possible. This method has big advantages in interventional radiology workplaces where the radiation fields are non-homogeneous and doses to staff can be relatively high. This method can also help for the application of the ALARA principle and for education and training of medical staff. For the future, we will transfer the skeletal data to the Realistic Anthropomorphic Flexible computational phantom [3] in Monte-Carlo simulation to calculate organ doses. References [1] D.B. Pelowitz, Ed., "MCNPX User’s Manual Version 2.7.0" LA-CP-11-00438 (2011). [2] Clairand et al. “Use of active personal dosemeters in interventional radiology and cardiology: Tests in laboratory conditions and recommendations - ORAMED project”, Radiation Measurements, Volume 46, Issue 11, (2011). [3] Lombardo et al. “Development and validation of the realistic anthropomorphic flexible (RAF) phantom”, Health Physics, 114:489–499, 05 (2018). Acknowledgements This project is funded by the CONCERT - European Joint Programme for the Integration of Radiation Protection Research 2014-2018 under grant agreement No. 662287. [less ▲]

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See detailPODIUM: Personal Online DosImetry Using computational Methods
Abdelrahman, Mahmoud Eid Mahmoud ULiege; Pasquale, Lombardo; Vanhoey, Olivier et al

Scientific conference (2019, February 01)

Individual monitoring of radiation workers is essential to ensure compliance with official dose limits and to allow application of the ALARA principle. Routine monitoring of staff is usually performed by ... [more ▼]

Individual monitoring of radiation workers is essential to ensure compliance with official dose limits and to allow application of the ALARA principle. Routine monitoring of staff is usually performed by means of passive dosimeters. However, current personal dosimeters are subject to large uncertainties, especially in heterogeneous fields, like those found in interventional radiology (IR). Within the PODIUM (Personal Online DosImetry Using computational Methods) research project, a user-friendly application was developed based on MCNP Monte-Carlo code to calculate doses to the staff in IR. The application uses both the data of motion tracking system to generate the position of the operator and the data from the Radiation Dose Structure Report (RDSR) from the imaging device to generate time-dependent parameters of the radiation source. The results of the first clinical validation of the system show good agreement within 10-40% between simulated Hp(10) with MCNP and measured Hp(10) with electronic personal dosimeter worn above the lead apron. Some challenges and limitations remain, however, the results from the two-year proof-of-concept PODIUM project are promising. We have shown that the technology is now available for tracking staff position and calculating their dose using detailed phantoms, without the need to wear an individual dosimeter. [less ▲]

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See detailPersonal Dose Computation with the Aid of Staff Monitoring systems based on 3D Depth Cameras
Abdelrahman, Mahmoud Eid Mahmoud ULiege; Phillips, Christophe ULiege; Seret, Alain ULiege et al

Conference (2018, April 16)

For more than 50 years, passive dosimeters have been used to assess the dose to workers occupationally exposed to ionizing radiation. Such dosimeters are designed to measure the operational quantity Hp(10 ... [more ▼]

For more than 50 years, passive dosimeters have been used to assess the dose to workers occupationally exposed to ionizing radiation. Such dosimeters are designed to measure the operational quantity Hp(10) as an estimate of the effective dose, E, which is a quantitative expression of the “radiation detriment” that cannot be measured directly. With these dosimeters, the results are mostly known only after some time, and wearing a dosimeter is often seen as a burden by some workers. Furthermore, the uncertainties associated with the present dosimeters (within a factor of 1.5 or 2 from the real value) are not negligible. In line with the current move to more real-time personal dose monitoring, we are working towards an innovative approach based on computational methods to determine occupational exposures. The aim of this research is to calculate doses to workers instead of measuring them. For this, the spatial radiation field, including energy and angular distribution, needs to be known. The real movement of the persons in a given workplace can be monitored in real-time using Time-of-Flight cameras and flexible computational phantoms representing the workers anatomy can be positioned using the tracking information. Finally, all this input data should be transferred to a tool, using Monte Carlo techniques to calculate the doses to the workers. As a first step, a tool used to track a person in 3D coordinates using Microsoft® Kinect™ was developed. The tool, which is utilizing the skeleton tracking algorithm embedded in the Kinect SDK from Microsoft, is capable of correctly tracking the worker movement in real-time. A series of validation experiments were performed to test the tracking tool and the dose calculation method. An anthropomorphic phantom was positioned on a moveable table in the horizontal irradiator of the Laboratory for Nuclear Calibration (LNK) at SCK•CEN. The phantom was moved to different distances from a Cs-137 source. The position of the phantom was monitored with the Kinect™ and the coordinates recorded. The dose to the phantom was calculated using different methods: 1. Using the reference values from the calibration facility (LNK), 2. Using VISIPLAN-3D: An analytical dose assessment tool developed at SCK•CEN, 3. Using MCNPX Monte-Carlo simulations, and 4. Using InstaDose® dosimeters based on direct ion storage technology. A comparison was made between each method and results showed good agreement between the reference, the measured and the calculated dose. This experiment was repeated with different degrees of complexity of movement of the phantom. This first test proved the validity of the methodology used. [less ▲]

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See detailPersonal Dose Computation with the Aid of Staff Monitoring system based on 3D Depth Cameras
Abdelrahman, Mahmoud Eid Mahmoud ULiege; Vanhavere, Filip; Struelens, Lara et al

Poster (2018, February 01)

For more than 50 years, passive dosimeters have been used to assess the dose to workers occupationally exposed to ionizing radiation. Such dosimeters are designed to measure the operational quantity Hp(10 ... [more ▼]

For more than 50 years, passive dosimeters have been used to assess the dose to workers occupationally exposed to ionizing radiation. Such dosimeters are designed to measure the operational quantity Hp(10) as an estimate of the effective dose, E, which is a quantitative expression of the “radiation detriment” that cannot be measured directly. With these dosimeters, the results are mostly known only after some time, and wearing a dosimeter is often seen as a burden by some workers. Furthermore, the uncertainties associated with the present dosimeters (within a factor of 1.5 or 2 from the real value) are not negligible. In line with the current move to more real time personal dose monitoring, we are working towards an innovative approach based on computational methods to determine occupational exposures. The aim of this research is to calculate doses to workers instead of measuring them. For this, the spatial radiation field, including energy and angular distribution, needs to be known. The real movement of the persons in a given workplace can be monitored in real-time using Time-of-Flight cameras and flexible computational phantoms representing the workers anatomy can be positioned using the tracking information. Finally, all this input data should be transferred to a tool, using Monte Carlo techniques to calculate the doses to the workers. As a first step, a tool used to track a person in 3D coordinates using Microsoft® Kinect™ was developed. The tool, which is utilizing the skeleton tracking algorithm embedded in the Kinect SDK from Microsoft, is capable of correctly tracking the worker movement in real-time. A series of validation experiments were performed to test the tracking tool and the dose calculation method. An anthropomorphic phantom was positioned on a moveable table in the horizontal irradiator of the Laboratory for Nuclear Calibration (LNK) at SCK•CEN. The phantom was moved to different distances from a Cs-137 source. The position of the phantom was monitored with the Kinect™ and the coordinates recorded. The dose to the phantom was calculated using different methods: 1. Using the reference values from the calibration facility (LNK), 2. Using VISIPLAN-3D: An analytical dose assessment tool developed at SCK•CEN, 3. Using MCNPX Monte-Carlo simulations, and 4. Using InstaDose® dosimeters based on direct ion storage technology. A comparison was made between each method and results showed good agreement between the reference, the measured and the calculated dose. This experiment was repeated with different degrees of complexity of movement of the phantom. This first test proved the validity of the methodology used. [less ▲]

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