Electronic Personal Dosimeters Research Articles

Radiation Doses to Operators in Hepatobiliary Interventional Procedures.

The primary aim of this study is to provide a summary of operators' radiation doses during hepatobiliary fluoroscopic guided procedures. In addition, patient dose in these procedures was also documented. A total of 283 transarterial chemoembolisation (TACE) and 302 biliary procedures, including 52 percutaneous transhepatic cholangiogram (PTC), 36 bilioplasty and 214 biliary catheter changes (BCC) performed over 14months, were included. Electronic personal dosimeters were used to measure operator radiation doses. Effective dose (E) was calculated using modified Niklason algorithm. Patient dose was measured as dose area product (DAP) and fluoroscopy time (FT). For TACE, E for radiologist ranged between 0 and 9.96µSv, for radiographer 0-0.99µSv and for nurse 0-4.65 µSv. The patient DAP and FT ranged between 1.5 and 421.9Gycm2 and 1.91-67.25min. For PTC, E for the radiologist ranged between 0.33 and 55.89µSv, for radiographer 0-38.61µSv and for nurse 0-3.18µSv. Patient DAP and FT ranged between 1.7 and 218.4Gycm2 and 2.07-71.53min. For bilioplasty, E ranged between 0.09 and 9.24µSv for radiologist, 0-0.84µSv for radiographer and 0-1.38 µSv for nurse. The patients' DAP and FT ranged from 0.7 to 52.54Gycm2 and 1.13-24.47min. For BCC, E ranged from 0 to 12.78 µSv for radiologist, 0-8.43µSv for radiographer and 0-4.05µSv for nurse. Patient DAP and FT ranged between 0.12 and 117.3Gycm2 and 0.57-15.83min. This study shows that doses to all operators performing hepatobiliary interventional procedures can be very low.

Response assessment of a new albedo neutron dosimeter

The use of thermoluminescent dosimeters (TLDs) by personnel who work in radiation-rich environments is required by law. However, many professionals prefer to use Electronic Personal Dosimeters (EPDs), which provide dose estimation in real time. This preference may lead to a generalized use of the EPD instead of using the required TLD, as the use of both types at once can be uncomfortable and impractical. In an effort to avoid this scenario, a gamma/neutron dosimeter composed of a TLD and an EPD is being developed. In this paper, the results obtained from the studies performed in order to develop the neutron albedo dosimeter to be incorporated in the TLD[Formula: see text]EPD dosimeter are presented. Monte Carlo simulations using the state-of-the-art Monte Carlo N-Particle Transport (MCNPX) code were used to calculate the response of the albedo dosimeter. The thermal neutron detectors under consideration for use in the proposed dosimeter are the EJ-426 and the EJ-420. Both detectors employ a lithium compoundenriched to 95% [Formula: see text]Li dispersed in a ZnS:(Ag) matrix. The tomographic phantom Korean Typical Man-2 was used in the simulations to calculate the fraction of radiation backscattered by a human body in different radiation field conditions. From these results, it was concluded that both dosimeters are fit to be used as albedo dosimeters.

Effective Techniques to Reduce Radiation Exposure to Medical Staff during Assist of X-ray Computed Tomography Examination

Medical staffs like radiological technologists, doctors, and nurses are at an increased risk of exposure to radiation while assisting the patient in a position or monitor contrast medium injection during computed tomography (CT). However, methods to protect medical staff from radiation exposure and protocols for using radiological protection equipment have not been standardized and differ among hospitals. In this study, the distribution of scattered X-rays in a CT room was measured by placing electronic personal dosimeters in locations where medical staff stands beside the CT scanner gantry while assisting the patient and the exposure dose was measured. Moreover, we evaluated non-uniform exposure and revealed effective techniques to reduce the exposure dose to medical staff during CT. The dose of the scattered X-rays was the lowest at the gantry and at the examination table during both head and abdominal CT. The dose was the highest at the trunk of the upper body of the operator corresponding to a height of 130 cm during head CT and at the head corresponding to a height of 150 cm during abdominal CT. The maximum dose to the crystalline lens was approximately 600 μSv during head CT. We found that the use of volumetric CT scanning and X-ray protective goggles, and face direction toward the gantry reduced the exposure dose, particularly to the crystalline lens, for which lower equivalent dose during CT scan has been recently recommended in the International Commission on Radiological Protection Publication 118.

OCCUPATIONAL EXPOSURE FROM F-18-FDG PET/CT: IMPLEMENTATION TO ROUTINE CLINICAL PRACTICE.

The purpose of this study was to assess the occupational radiation exposure arising from positron emission tomography combined with X-ray computed tomography (PET/CT) procedures. From 2009 through the end of 2014, in a team of six technologists, personal dosimetry was performed using electronic personal dosemeters and film badge dosemeters. The technologists registered the separate exposure after each PET/CT operational step, which included radiopharmaceutical arrival, dispensing in individual syringes, injection and patient positioning.From the total of 3024 PET/CT procedures, 2142 were available for analysis. The personal dose equivalent for the technologists performing PET/CT ranged from 11.5 nSv/MBq to 23.8 nSv/MBq. Whole-body radiation dose originated mainly from radiopharmaceutical injection (41.5%) and patient positioning (51.1%). The sources of occupational exposure were successfully identified for PET/CT procedures. Record keeping using on-site occupational dosimetry is a useful tool for exposure optimisation.

Radiation exposure levels according to vascular access sites during PCI : Aprospective controlled study.

We previously showed that using the radial artery access site as opposed to the femoral artery site decreases the radiation exposure of patients during coronary artery interventions. The objective of this study was to compare radiation exposure levels of the operating physician during coronary interventions when incorporating both radial and femoral artery approaches. The study assessed all coronary angioplasties performed in amajor metropolitan general hospital. The study design was prospective and observational, in which we measured the radiation exposure of the patient and the operator. Measurements of radiation levels were made using an electronic personal dosimeter (Diamentor® E2-DAP) at the radial and at the femoral artery access sites. Aninterventional cardiologist operator performed all the percutaneous coronary interventions (PCI) using asingle-plane angiography unit via both femoral and radial artery approaches. Data from 252 PCIs were recorded. The mean physician radiation exposure levels from the femoral access site and the right radial access site were 40.5± 20.2 µSv and 47.5± 26.5 µSv, respectively (p< 0.02). There was astrong correlation between physician and patient radiation exposure levels. However, there was no correlation between patient body mass index and radiation exposure levels. We found significantly higher physician radiation exposure levels with the radial artery than with the femoral artery access site.

Performance Testing of Selected Types of Electronic Personal Dosimeters in X- and Gamma Radiation Fields

Performance Testing of Selected Types of Electronic Personal Dosimeters in X- and Gamma Radiation Fields

Performance Testing Of Selected Types of Electronic Personal Dosimeters in X- and Gamma Radiation Fields.

Electronic personal dosimeters (EPDs) are increasingly being used alongside conventional thermoluminescent dosimeters to measure the dose of legal record in terms of personal dose equivalent. Therefore, it is of great importance to execute performance tests of these dosimeters in photon fields of various energies and at various angles of incidence. This testing is done in order to simulate the behavior of these dosimeters in realistic multidirectional polyenergetic ionizing radiation fields. Tests of accuracy, linearity, energy response, and angular response have been performed on 10 EPDs from multiple manufacturers. Various radiation qualities have been used in the energy range from 33 keV to 1.33 MeV and for angles of incidence 0° to 80°. This research proves that many of the EPDs tested performed according to the manufacturer's specifications and the requirements of the international standards regarding personal dosimetry.

Development of measurement methods and dose evaluating algorithms for electronic personal dosimeter

For personal radiation dose monitoring, electronic personal dosimeters (EPD), also known as active personal dosimeter (APD), using silicon diode detector have the advantage capability of measuring and displaying directly the exposure results of gamma, beta and neutron radiations in real time. They are mainly considered as good complement to passive dosimeters to satisfy ALARA principle in the radiation protection. In this paper, the meansurement methods and algorithms for evaluating personal dose equivalents such as Hp(10) and Hp(0.07) from air-kerma are studied and developed in two directions: the first, named energy correction method based on incident energy determined by the ratio of two detector responses with the different filter configurations; the second new method is carried out in the way that matching the shape of a detector’s energy response curve to the kerma-to-personal dose equivalent conversion function provides an approximate means of determining the dose equivalent without the need to resolve the actual incident energies. The algorithm has also been experimentally verified at Secondary Standards Dosimetry Laboratory (SSDL) of INST by the beam of radiation defined in ISO 4037-1. The obtained results of personal dose equivalents with errors almost less than 30% in energy range from 20 keV to 1.5 MeV are partially met the EPD design requirements according to the IEC 61526 Standard. The work and results of described in this paper are important basics for design and construction of completed electronic personal dosimeter.

Energy response correction for an electronic personal dosimeter using the channel ratio method

An electronic personal dosimeter mainly uses a Si-PIN photodiode as X- and gamma-ray detectors. The photon energy response of this instrument is inconsistent in the case of no correction, which seriously affects the accurate monitoring of personal dose equivalent \(H_{\mathrm{p}}\)(10) parameters for radiation workers. For this reason, in this paper we propose a method of combining composite screen detection technology, multichannel measurement technology, and the channel ratio method to achieve accurate measurement of the personal dose equivalent parameters. According to China National Standard GB/T 13161-2003 and National Verification Regulation JJG 1009-2006, the instrument was tested in the energy range between 48 keV and 1.25 MeV. The experimental results showed that the difference of energy response to \(^{137}\)C\(_{s}\) corrected by the new method was almost constant within \(\pm 6.0\%\), which fulfilled the \(\pm 30\%\) requirement of GB/T 13161-2003 and JJG 1009-2006. Meanwhile, the method proposed obtained energy information regarding the radiation field.

Effect of the Scattering Radiation in Air and Two Type of Slap Phantom between PMMA and the ISO Water Phantom for Personal Dosimeters Calibration

The calibration of personal dosimeter to determine the quantities of the personal dose equivalent, Hp(d), is required to be placed on a suitable phantom in order to provide a reasonable approximation to the radiation backscattering properties as equivalent as part of body. The dosimeter which is worn on the trunk usually calibrated with slap phantom which recommended in ICRU 47 with dimension of 30 cm (w) x 30 cm (h) x 15 cm (t) PMMA slab phantom to achieve uniformity in calibration procedures, on the other hand the International Organization for Standardization (ISO), ISO 4037-3, proposed the ISO water slap phantom, with PMMA walls, same dimension but different wall thickness (front wall 2.5 mm and other side wall 10 mm thick) and fill with water. However, some laboratories are still calibrating a personal dosimeter in air in term of ambient dose equivalent, H*(d). This research study the effect of the scattering radiation in two type of those slap phantoms and in air, to calibrate two type of OSL (XA and LA) and electronic personal dosimeters. The X-ray and Cs-137 radiation field with the energy range from 33 to 662 keV were used. The results of this study will be discussed.

Personalized Feedback on Staff Dose in Fluoroscopy-Guided Interventions: A New Era in Radiation Dose Monitoring

PurposeRadiation safety and protection are a key component of fluoroscopy-guided interventions. We hypothesize that providing weekly personal dose feedback will increase radiation awareness and ultimately will lead to optimized behavior. Therefore, we designed and implemented a personalized feedback of procedure and personal doses for medical staff involved in fluoroscopy-guided interventions.Materials and MethodsMedical staff (physicians and technicians, n = 27) involved in fluoroscopy-guided interventions were equipped with electronic personal dose meters (PDMs). Procedure dose data including the dose area product and effective doses from PDMs were prospectively monitored for each consecutive procedure over an 8-month period (n = 1082). A personalized feedback form was designed displaying for each staff individually the personal dose per procedure, as well as relative and cumulative doses. This study consisted of two phases: (1) 1–5th months: Staff did not receive feedback (n = 701) and (2) 6–8th months: Staff received weekly individual dose feedback (n = 381). An anonymous evaluation was performed on the feedback and occupational dose.ResultsPersonalized feedback was scored valuable by 76% of the staff and increased radiation dose awareness for 71%. 57 and 52% reported an increased feeling of occupational safety and changing their behavior because of personalized feedback, respectively. For technicians, the normalized dose was significantly lower in the feedback phase compared to the prefeedback phase: [median (IQR) normalized dose (phase 1) 0.12 (0.04–0.50) µSv/Gy cm2 versus (phase 2) 0.08 (0.02–0.24) µSv/Gy cm2, p = 0.002].ConclusionPersonalized dose feedback increases radiation awareness and safety and can be provided to staff involved in fluoroscopy-guided interventions.

Dose inspection and risk assessment on radiation safety for the use of non-medical X-ray machines in Taiwan

The subject of this study is the on-site visits and inspections of facilities commissioned by the Atomic Energy Council (AEC) in Taiwan. This research was conducted to evaluate the possible dose and dose rate of cabinet-type X-ray equipment with nominal voltages of 30–150kV and open-beam (portable or handheld) equipment, taking both normal operation and possibly abnormal operation conditions into account. Doses and dose rates were measured using a plastic scintillation survey meter and an electronic personal dosimeter. In total, 401 X-ray machines were inspected, including 139 units with nominal voltages of 30–50kV X-ray equipment, 140 units with nominal voltages of 50–150kV, and 122 open-beam (portable or handheld) X-ray equipment. The investigated doses for radiation workers and non-radiation workers operating cabinet-type X-ray equipment under normal safety conditions were all at the background dose level. Several investigated dose rates at the position of 10cm away from the surface of open-beam (portable or handheld) X-ray equipment were very high, such X-ray machines are used by aeronautical police for the detection of suspected explosives, radiation workers are far away (at least 10m away) from the X-ray machine during its operation. The doses per operation in X-ray equipment with a 30–50kV nominal voltage were less than 1 mSv in all cases of abnormal use. Some doses were higher than 1 mSv per operation for X-ray equipment of 50–150kV nominal voltage X-ray. The maximum dose rates at the beam exit have a very wide range, mostly less than 100 μSv/s and the largest value is about 3.92 mSv/s for open-beam (portable or handheld) X-ray devices. The risk induced by operating X-ray devices with nominal voltages of 30–50kV is extremely low. The 11.5 mSv dose due to one operation at nominal voltage of 50–150kV X-ray device is equivalent to the exposure of taking 575 chest X-rays. In the abnormal use of open-beam (portable or handheld) X-ray equipment, the effective dose of 3.92 mSv/s is equivalent to taking 196 chest radiographs within 1s. This work assessed the annual doses (equivalent and effective doses) and risks of X-ray operator staff as reasonably as possible. The results of this research are helpful to the AEC (competent authority of ionization radiation) to improve the management and perform the safe control of X-ray equipment.

Beam projections and radiation exposure in transradial and transfemoral approaches during coronary angiography.

Objective:We aimed to compare the operator and patient radiation exposure in standard projections during elective diagnostic coronary angiography procedures via transradial (TRA) versus transfemoral (TFA) approaches.Methods:In this analytical cross-sectional study, a total of 202 consecutive patients who were candidates for diagnostic coronary angiography were randomized to undergo the procedure via TFA or TRA approaches (101 in each group). Patients with abnormal Allen test and history of coronary artery bypass surgery, valvular heart disease, and unsuccessful coronary angiography were excluded from the study. A single operator performed all of the procedures using a single angiography system. Patient and operator radiation exposure were measured using diamentor and an electronic personal dosimeter, respectively. Each procedure comprised a standardized sequence of projections including four standard views for the left coronary system and two standard views for the right coronary system.Results:Left anterior oblique (LAO) caudal (50°/30°) and right anterior oblique RAO (30°) projections were associated with the highest and lowest patient radiation exposure, respectively. The operator received a significantly higher radiation exposure in the TRA approach for LAO cranial (for both left and right coronary systems) and LAO caudal (for left coronary system) projections during coronary angiography compared with the TFA approach.Conclusion:Though a similar amount of patient radiation exposure in each projection was observed among TFA and TRA groups; LAO cranial and LAO caudal projections were associated with a significantly higher operator radiation exposure in the TRA group. These findings need to be considered when choosing the optimal arterial approach for patients scheduled for coronary angiography.

O24. Calibration of radiation monitoring instruments at the NMISA

Introduction Radiation monitoring instruments are calibrated to ensure measurements of the instrument are reliable and accurate in all ranges and for energy spectrum in which the instrument is expected to function. The Dosimetry Section (Radiation Protection) of NMISA provides the calibration service for all types of radiation monitoring instruments. This paper will focus on the calibration of surface contamination monitor in terms of 2 π efficiency and surface activity response (SAR), survey meter in terms of ambient dose equivalent (ADE) rate and electronic personal dosimeter (EPD) in terms of personal dose equivalent (PDE). Measurements are traceable to the national standards calibrated at NPL, PTB and BIPM. Materials and methods Measurements for determining the 2 π efficiency and surface activity response of the surface contamination monitor were performed using the wide area reference sources and linearity measurements were performed using Cs-137 source. Survey meter and electronic personal dosimeter were calibrated using Cs-137 and Am-241 sources. Calibrations were performed in accordance with ISO 4037-3, ISO 8769 and SANAS TR 18-02. IAEA report series no. 16 is also used as a guideline. Results The uncertainties in the 2 π efficiency and surface activity response were estimated not to exceed ± 11% and ±4,0% respectively. For the survey meter and electronic personal dosimeter, the average error for all calibrated ranges did not exceed ±15% and the average percentage error per point for all ranges did not exceed ±25%. Conclusion The results obtained from calibrations were conforming to the SANAS TR 18-02 requirements and certificates issued in accordance with the ISO/IEC 17025:2005.

Radiation doses to operators performing transjugular intrahepatic portosystemic shunt using a flat-panel detector-based system and ultrasound guidance for portal vein targeting.

The aim of this study was to prospectively evaluate effective dose (E) of operators performing transjugular intrahepatic portosystemic shunts (TIPS) in a single centre. Patients' radiation exposure was also collected. Between 8/2015 and 6/2016, 45 consecutive TIPS were performed in adult patients using a flat-panel detector-based system (FPDS) and real-time ultrasound guidance (USG) for portal vein targeting. Electronic personal dosimeters were used to measure radiation doses to the primary and assistant operators, anaesthesia nurse and radiographer. Patients' radiation exposure was measured with dose area product (DAP); fluoroscopy time (FT) was also collected. Mean E for the primary operator was 1.40μSv (SD 2.68, median 0.42, range 0.12 - 12.18), for the assistant operator was 1.29μSv (SD 1.79, median 0.40, range 0.10 - 4.89), for the anaesthesia nurse was 0.21μSv (SD 0.67, median 0.10, range 0.03 - 3.99), for the radiographer was 0.42μSv (SD 0.71, median 0.25, range 0.03 - 2.67). Mean patient DAP was 59.31 GyCm2 (SD 56.91, median 31.58, range 7.66 - 281.40); mean FT was 10.20min (SD 7.40, median 10.40, range 3.8 - 31.8). The use of FPDS and USG for portal vein targeting allows a reasonably low E to operators performing TIPS. • The operators' E vary according to the complexity of the procedure. • FPDS and USG allow a reasonably low E to TIPS operators. • FPDS and USG have an important role in reducing the occupational exposure.

Effect of dosimeter's position on occupational radiation extremity dose measurement for nuclear medicine workers during (18)F-FDG preparation for PET/CT.

BackgroundThe recent spread of positron emission tomography-computed tomography (PET/CT) poses extremity dosimetry challenges. The question arose whether the radiation dose measured by the ring thermoluminescent dosimeter usually worn on the proximal phalanx (P1) of the index finger measures doses that are representative of the true doses received by the upper extremities of the operators. A prospective individual dosimetry study was performed in which the personal equivalent dose Hp (0.07) received during a specific 2-[18F]fluoro-2-deoxy-d-glucose (18F-FDG) manual dose-dispensing procedure was measured in a paired design by two operational personal electronic dosimeters fitted on the palm side of the index finger, namely in the P1 and distal phalanx (P3) positions. The study participants were ten nuclear medicine technologists working in two nuclear medicine departments. The personal equivalent radiation doses received by the palm side of the proximal phalanx of the index finger [Hp (0.07)P1] and that received by the distal phalanx [Hp (0.07)P3] were compared.ResultsThe median Hp (0.07)P3/Hp (0.07)P1 ratio per participant varied between 1.0 and 2.5 (based on 23 to 31 measurements per participant). The 271 paired measurements revealed a crude Hp (0.07)P3/Hp (0.07)P1 ratio of 1.67, significantly different from 1 (p = 0.0004, 95 % CI [1.35–2.07]). When adjusted on participant’s gender and mother vial activity, the ratio was similar (1.53, p = 0.003, 95 % CI [1.22–1.92]).ConclusionsThe study demonstrated a significant disparity that may exist between the radiation doses measured in the P1 and P3 positions of operators during 18F-FDG manipulation. These findings emphasize the importance of performing workplace dosimetry studies adapted to each radiopharmaceutical and manipulation thereof, aiming to guarantee optimal workers’ dosimetry monitoring schemes.Trial registrationHospital Nursing and Paramedical Research Program (PHRIP, 2011–2013) from the French Ministry of Health (DGOS), http://social-sante.gouv.fr/IMG/pdf/Resultats_PHRIP_2011.pdf

On the response of electronic personal dosimeters in constant potential and pulsed x- ray beams

Electronic personal dosimeters (EPDs) based on solid state detectors have widely been used but some deficiencies in their response in pulsed radiation beams have been reported. Nowadays, there is not an international standard for pulsed x-ray beams for calibration or type testing of dosimeters. Irradiation conditions for testing the response of EPDs in both the constant potential and pulsed x-ray beams were established in CDTN. Three different types of EPDs were tested in different conditions in similar ISO and IEC x-ray qualities. Results stressed the need of performing additional checks before using EPDs in constant potential or pulsed x-rays.

Effect of real time visual feedback on cardiologist’s radiation exposure with an established electronic real time radiation system

Introduction Real time visual feedback from electronic personal dosimeters has been shown to reduce occupational exposures when first introduced in an interventional cardiology setting [1] . In a recent paper by our group, we found that there was little difference one month and six months after the introduction of such a system. This study aims to assess the effect of removing the visual dose feedback on operator exposures. Materials and methods Occupational collar exposures were monitored for cardiologists ( n = 5) over a series of mixed case types ( n = 95) in a busy interventional cardiology laboratory [1] . For half the cases the visual feedback screen was switched off during the procedure depending on an assigned random number. The radiation exposure data was analysed using a Mann Whitney U test. Results/discussion There was no significant statistical difference in radiation exposure to the cardiologists between when the visual feedback system was switched off or on. Increased case numbers may point to differences between operators and case types. Conclusion This study suggests that real time visual feedback may not prove beneficial to dose reduction in an established electronic monitoring system.

Surgeon's and Patient's Radiation Exposure Through Vertebral Body Cement Augmentation Procedures: A Prospective Multicentric Study of 49 Cases

Vertebral body cement augmentation as a treatment option for osteoporotic or traumatic fractures has become increasingly popular during the past decade. However, these surgical procedures require numerous fluoroscopic examinations, resulting in high radiation exposure for the patient and the surgical team. The aim of this study was to evaluate the level of radiation exposure of the spine surgeon and the patient during these percutaneous procedures. Forty-nine patients admitted for single- or 2-level vertebral compression fracture were prospectively included and treated with vertebral body cement augmentation. For each procedure, radiation dose was measured on the surgeon's whole body, lens, and extremities as well as patient irradiation. Each surgeon wore 2 thermoluminescent dosimeters to measure lens and extremities radiation exposure and 1 electronic personal dosimeter. Patient clinical and surgical data, effective dose to patient, and surgeon were analyzed. Mean operative time was 31.5 ± 11.7 minutes. The average fluoroscopic time was 61.0 ± 27.1 seconds. The average whole-body radiation dose per procedure was 1.4 ± 2.1 μSv. The average equivalent dose to lens and extremities were 44 μSv and 59 μSv, respectively. Values of radiation doses for surgeon and patient were lower than those reported in the previous literature. The recommended annual dose limit is set to 500mSv for extremities and 150 mSv for lens. According to our results, the exposure dose to the eye exceeds the annual limit after 3500 procedures. However, there is increasing concern among surgeons about radiation exposure, and there is still a need for solutions as preventive measures.

RESPONSE OF DOSEMETERS IN FIELDS GENERATED BY LASER-ACCELERATED PROTONS.

In laser-driven acceleration, ultra-short and intense laser pulses are focussed on targets to generate beams of ionising radiation. One of the most important issues to be addressed is personal monitoring. While traditional dosemeters were designed primarily for measurements in continuous fields, dosemeters for laser laboratories must be capable of working in pulsed fields of pulse length below 1 ps, in a single-shot regime up to the repetition rate of 1 kHz. Responses of conventional dosemeters (films, polyallyldiglycol carbonate, electronic personal dosemeter) to proton bunches of up to 30 MeV energy produced by South Korean PW laser system at the Advanced Photonics Research Institute, Gwangju Institute of Science and Technology were studied, both by means of Monte Carlo simulations and experimentally.