Dose Monitoring System Research Articles

TU‐E‐224‐01: The Role of Voluntary versus Mandatory Regulatory Standards

The patientˈs skin and the lens of the eye are the critical tissues for most fluoroscopically guided interventional procedures. Risks include hair loss, skin toxicity, and radiogenic cataracts. Appropriate dosimetric feedback to the operator contributes to optimizing benefit‐risk. Ideally, interventional fluoroscopes should provide real‐time feedback via a continuously updated dose maps and accurate estimates of peak skin dose. Such technology is not generally available in 2011. However, a variety of real‐time and post‐procedure tools are currently available for managing fluoroscopic skin irradiation. Equipment conforming to IEC 60601‐2‐43 (2000, 2010) displays fluoroscopic time, PKA and Ka,r at the operatorˈs working position. All fluoroscopes sold in the USA after mid 2006 displays fluoro‐time and Ka,r. Various film and detector arrays have been used to obtain post‐procedure dose maps for more than a decade.Newer fluoroscopes and third‐party dose monitoring systems are beginning to offer useful proprietary dose mapping in angular space (defined by gantry angles) in both real‐time and post‐procedure flavors. Initial commercial deliveries of the DICOM Radiation Dose Structured Report (RDSR) provide detailed post‐procedure procedural information in enough detail to facilitate detailed dose reconstruction. Data in the RDSR is in defined public fields to facilitate accessibility. The relevant DICOM and IEC standards include specifications for real‐time streaming of the data. This will facilitate the development of independent real‐time dose modeling. This lecture will review the technologies available in 2011 and will provide an estimate of future time‐lines in this area. It will also include a discussion of the use of complete sets of dosimetric data as part of the quality process.Learning Objectives:1. Understand the advantages and disadvantages of currently available dose monitoring technologies.2. Understand the evolution toward real‐time skin dose mapping.3. Understand how standardized dosimetry can be incorporated into a QA program.

Upgrades of DARWIN, a dose and spectrum monitoring system applicable to various types of radiation over wide energy ranges

A dose and spectrum monitoring system applicable to neutrons, photons and muons over wide ranges of energy, designated as DARWIN, has been developed for radiological protection in high-energy accelerator facilities. DARWIN consists of a phoswitch-type scintillation detector, a data-acquisition (DAQ) module for digital waveform analysis, and a personal computer equipped with a graphical-user-interface (GUI) program for controlling the system. The system was recently upgraded by introducing an original DAQ module based on a field programmable gate array, FPGA, and also by adding a function for estimating neutron and photon spectra based on an unfolding technique without requiring any specific scientific background of the user. The performance of the upgraded DARWIN was examined in various radiation fields, including an operational field in J-PARC. The experiments revealed that the dose rates and spectra measured by the upgraded DARWIN are quite reasonable, even in radiation fields with peak structures in terms of both spectrum and time variation. These results clearly demonstrate the usefulness of DARWIN for improving radiation safety in high-energy accelerator facilities.

重离子治癌终端的束流强度及剂量监测系统

重离子治癌终端的束流强度及剂量监测系统

Dose calculation in biological samples in a mixed neutron-gamma field at the TRIGA reactor of the University of Mainz

To establish Boron Neutron Capture Therapy (BNCT) for non-resectable liver metastases and for in vitro experiments at the TRIGA Mark II reactor at the University of Mainz, Germany, it is necessary to have a reliable dose monitoring system. The in vitro experiments are used to determine the relative biological effectiveness (RBE) of liver and cancer cells in our mixed neutron and gamma field. We work with alanine detectors in combination with Monte Carlo simulations, where we can measure and characterize the dose. To verify our calculations we perform neutron flux measurements using gold foil activation and pin-diodes. Material and methods. When L-α-alanine is irradiated with ionizing radiation, it forms a stable radical which can be detected by electron spin resonance (ESR) spectroscopy. The value of the ESR signal correlates to the amount of absorbed dose. The dose for each pellet is calculated using FLUKA, a multipurpose Monte Carlo transport code. The pin-diode is augmented by a lithium fluoride foil. This foil converts the neutrons into alpha and tritium particles which are products of the 7Li(n,α)3H-reaction. These particles are detected by the diode and their amount correlates to the neutron fluence directly. Results and discussion. Gold foil activation and the pin-diode are reliable fluence measurement systems for the TRIGA reactor, Mainz. Alanine dosimetry of the photon field and charged particle field from secondary reactions can in principle be carried out in combination with MC-calculations for mixed radiation fields and the Hansen & Olsen alanine detector response model. With the acquired data about the background dose and charged particle spectrum, and with the acquired information of the neutron flux, we are capable of calculating the dose to the tissue. Conclusion. Monte Carlo simulation of the mixed neutron and gamma field of the TRIGA Mainz is possible in order to characterize the neutron behavior in the thermal column. Currently we also speculate on sensitizing alanine to thermal neutrons by adding boron compounds.

Establishment of technical prerequisites for cell irradiation experiments with laser-accelerated electrons

In recent years, laser-based acceleration of charged particles has rapidly progressed and medical applications, e.g., in radiotherapy, might become feasible in the coming decade. Requirements are monoenergetic particle beams with long-term stable and reproducible properties as well as sufficient particle intensities and a controlled delivery of prescribed doses at the treatment site. Although conventional and laser-based particle accelerators will administer the same dose to the patient, their different time structures could result in different radiobiological properties. Therefore, the biological response to the ultrashort pulse durations and the resulting high peak dose rates of these particle beams have to be investigated. The technical prerequisites, i.e., a suitable cell irradiation setup and the precise dosimetric characterization of a laser-based particle accelerator, have to be realized in order to prepare systematic cell irradiation experiments. The Jena titanium:sapphire laser system (JETI) was customized in preparation for cell irradiation experiments with laser-accelerated electrons. The delivered electron beam was optimized with regard to its spectrum, diameter, dose rate, and dose homogeneity. A custom-designed beam and dose monitoring system, consisting of a Roos ionization chamber, a Faraday cup, and EBT-1 dosimetry films, enables real-time monitoring of irradiation experiments and precise determination of the dose delivered to the cells. Finally, as proof-of-principle experiment cell samples were irradiated using this setup. Laser-accelerated electron beams, appropriate for in vitro radiobiological experiments, were generated with a laser shot frequency of 2.5 Hz and a pulse length of 80 fs. After laser acceleration in the helium gas jet, the electrons were filtered by a magnet, released from the vacuum target chamber, and propagated in air for a distance of 220 mm. Within this distance a lead collimator (aperture of 35 mm) was introduced, leading, along with the optimized setup, to a beam diameter of 35 mm, sufficient for the irradiation of common cell culture vessels. The corresponding maximum dose inhomogeneity over the beam spot was less than 10% for all irradiated samples. At cell position, the electrons posses a mean kinetic energy of 13.6 MeV, a bunch length of about 5 ps (FWHM), and a mean pulse dose of 1.6 mGy/bunch. Cross correlations show clear linear dependencies for the online recorded accumulated bunch charges, pulse doses, and pulse numbers on absolute doses determined with EBT-1 films. Hence, the established monitoring system is suitable for beam control and a dedicated dose delivery. Additionally, reasonable day-to-day stable and reproducible properties of the electron beam were achieved. Basic technical prerequisites for future cell irradiation experiments with ultrashort pulsed laser-accelerated electrons were established at the JETI laser system. The implemented online control system is suitable to compensate beam intensity fluctuations and the achieved accuracy of dose delivery to the cells is sufficient for radiobiological cell experiments. Hence, systematic in vitro cell irradiation experiments can be performed, being the first step toward clinical application of laser-accelerated particles. Further steps, including the transfer of the established methods to experiments on higher biological systems or to other laser-based particle accelerators, will be prepared.

北陸地域の訪問線量測定による基準点吸収線量測定と ＱＡ／ＱＣアンケート調査（第１報）‐過去データとの比較による経年的推移について‐

To analyze temporal changes in human resources in the radiotherapy section, quality assurance/quality control (QA/QC) and dose difference for radiotherapy in the Hokuriku area based on the results of past investigations and our investigation. We visited radiotherapy sections of 17 hospitals in the Hokuriku area (5 in Toyama, 9 in Ishikawa and 3 in Fukui) to measure the dose at the reference point of a linear accelerator (LINAC), as we asked questions to a radiotherapist about human resources, QA/QC of LINAC, etc. We compared our results with past reports (1992 to 2007) on the dose difference, human resources and frequency of dose monitor system calibration. The number of physicians has not changed since 1999, but the number of radiotherapists was significantly increased. Weekly dose monitor system calibration has been achieved in 80% of the institutions in our survey. This percentage was significantly higher than in the past surveys. The dose difference distribution from our onsite dosimetry did not significantly differ from that from the onsite dosimetry in 2007. 91% of the institutions have accomplished within 2% of the dose difference. We found that the number of physicians has not increased since 1999, but the number of radiotherapists has increased. We conclude that the increment of radiotherapists led to 80% achievement of the weekly dose monitor system calibration. Almost all institutions in Hokuriku area have properly performed QA of the dose monitor system.

The Recent Improvement and Verification of DARWIN: Development of a New DAQ System and Results of Flight Experiment

To improve radiation safety in high-energy accelerator facilities, the authors have been developing the new radiation dose monitor device DARWIN: Dose monitoring system Applicable to various Radiations with WIde energy raNges. DARWIN is composed of (a) a phoswitch-type scintillation detector, which consists of liquid organic scintillator BC501A coupled with ZnS(Ag) scintillation sheets doped with 6Li, and (b) a data acquisition (DAQ) system for digital analysis of the waveform of the scintillator signals. The DAQ system was recently updated in order to apply DARWIN in monitoring dose rates in radiation fields having time structure, introducing an originally developed module based on a field-programmable gate array. To examine the performance of DARWIN placed in radiation fields composed of varieties of particles over wide energy ranges, the authors mounted DARWIN on a jet aircraft and measured neutron, photon, muon, electron, and positron dose rates at high altitudes. The measured dose rates excellently agreed with the corresponding data calculated by EXPACS over a wide altitude range. This agreement indicates the applicability of DARWIN to dose monitoring in complex radiation fields such as those in high-energy accelerator facilities and aircrafts.

SU‐FF‐T‐308: Output Factor Measurements and Aperture Size Dependence of Dose Distributions for Scanned Proton Beams at MPRI

Purpose: Prior to a patient's proton beam treatment at MPRI, the Quality Assurance program entails measurement of the specific output factor for each field with its associated hardware in place. As a basis for comparison to patient specific measurements, and to characterize our dose delivery and monitoring system, we have measured a standard set of output factors (10 cm diameter aperture without compensator) over the energy range of clinical interest for all spread‐out Bragg peaks (SOBPs) commissioned for delivery. We have also made detailed measurements of on‐axis depth‐dose distributions as a function of aperture diameter from 10 cm to 2 cm for representative scanned‐beam fields to further characterize our system. Method and Materials: Single point output factor measurements were made in a water phantom using a Markus ionization chamber. Additionally, depth‐dose distributions were acquired with a multi‐layer ionization chamber (MLIC) array, which provides 122 depth channels spaced approximately every 0.18 cm. Lastly, beam profiles were measured with a commercial array of ionization chambers (MatriXX, IBA). Results: The results show the systematic decrease in dose along the SOBP plateau, and the increase of the SOBP entrance dose relative to the plateau dose, as a function of aperture size and treatment range. The need to carefully plan and deliver fields less than 5 cm diameter is obvious. Additionally, the application of the standard output factor measurements to predicting patient specific output factors for prostate patients has been verified with ±0.8% accuracy. Conclusions: Given the similarity of prostate fields and our ability to model the output factors within ±0.8%, we no longer measure patient specific output factors for prostate patients treated with opposed laterals. But, we do make these output factor measurements for other treatment fields while utilizing the MLIC to characterize depth‐dose distributions for fields smaller than 5 cm diameter.

Application of MOSFET Detectors for Dosimetry in Small Animal Radiography Using Short Exposure Times

Digital subtraction angiography (DSA) X-ray imaging for small animals can be used for functional phenotyping given its ability to capture rapid physiological changes at high spatial and temporal resolution. The higher temporal and spatial requirements for small-animal imaging drive the need for short, high-flux X-ray pulses. However, high doses of ionizing radiation can affect the physiology. The purpose of this study was to verify and apply metal oxide semiconductor field effect transistor (MOSFET) technology to dosimetry for small-animal diagnostic imaging. A tungsten anode X-ray source was used to expose a tissue-equivalent mouse phantom. Dose measurements were made on the phantom surface and interior. The MOSFETs were verified with thermoluminescence dosimeters (TLDs). Bland-Altman analysis showed that the MOSFET results agreed with the TLD results (bias, 0.0625). Using typical small animal DSA scan parameters, the dose ranged from 0.7 to 2.2 cGy. Application of the MOSFETs in the small animal environment provided two main benefits: (1) the availability of results in near real-time instead of the hours needed for TLD processes and (2) the ability to support multiple exposures with different X-ray techniques (various of kVp, mA and ms) using the same MOSFET. This MOSFET technology has proven to be a fast, reliable small animal dosimetry method for DSA imaging and is a good system for dose monitoring for serial and gene expression studies.

Design of the Online Integral Dose Monitor System for BESIII EMC

High beam current of BEPCII leads to high radiation background around the interaction point where the Electro-Magnetic Calorimeter (EMC), a key sub-detector of BESIII, is located. The performance of EMC degrades due to accumulated exposure to the high radiation background. In order to monitor the integral dose deposited in the EMC, an online integral dose monitor system has been developed according to the study on 400nm IMPL RadFET. This system consists of 72 RadFETs located around EMC. A microcontroller based DAQ box can readout all the RadFET information and send to computers via an Ethernet interface. The detail of this system and the BEPC testing result are presented in this paper.

Advanced optimization and process control of plasma doping apparatus

AbstractIn keeping with the trend of progressively shrinking device features, future generation advanced Logic and DRAM devices will require shallower junction depths and poly thickness and also higher doses compared to their current day counterparts. Present monomer based beamline technology suffers decreasing throughput during this transition as a result of space charge limitations. Plasma doping is a well characterized alternative that not only meets the doping requirements for <70 nm ITRS DRAM and Logic technology nodes but also features superior throughput levels that are largely energy insensitive. The simplicity of the Plasma doping tool design and evolution in process control offer a promising future for production worthiness of this technique. Key challenges for adoption of plasma doping tools in mainstream doping production are dose and contamination control. In this article, we report on the plasma modeling and diagnostic approaches used to optimize reactor design and describe how a closed loop faraday dose monitoring system is utilized to ensure dose repeatability. This combined modeling, diagnostics and sensor approach, which will be validated with on‐wafer measurements, enables the adoption of plasma doping in a mass production environment. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Linearity of the Dose Monitor System at Low Monitor Units

The accuracy of the dose monitor system of a medical electron accelerator is of crucial importance for the precise delivery of the prescribed dose. Special attention is given to the case of low monitor units (MU). The long-term stability of the dose monitor system is analyzed. Photon and electron fields with monitor units between 1 and 500 MU were measured with field sizes of 10 x 10 cm(2) and 20 x 20 cm(2) at source-skin distances (SSDs) of 100 cm and 95 cm, respectively. The relative dose per MU [see text] was determined for an Elekta linear accelerator. The relative dose per MU was measured to be constant within about 1% down to fields with only 2 MU. The deviation remained below 2% down to 1 MU which is the minimum setting of the accelerator. The long-term stability is better than 0.2% per month. No therapeutically relevant deviation of the prescribed dose could be detected for the Elekta linear accelerator. This is a prerequisite for the implementation of intensity-modulated radiotherapy (IMRT) techniques.

Darwin: dose monitoring system applicable to various radiations with wide energy ranges

A new radiation dose monitor, designated as DARWIN (Dose monitoring system Applicable to various Radiations with Wide energy ranges), has been developed for real-time monitoring of doses in workspaces and surrounding environments of high-energy accelerator facilities. DARWIN is composed of a phoswitch-type scintillation detector, which consists of liquid organic scintillator BC501A coupled with ZnS(Ag) scintillation sheets doped with (6)Li, and a data acquisition system based on a Digital-Storage-Oscilloscope. DARWIN has the following features: (1) capable of monitoring doses from neutrons, photons and muons with energies from thermal energy to 1 GeV, 150 keV to 100 MeV and 1 MeV to 100 GeV, respectively, (2) highly sensitive with precision and (3) easy to operate with a simple graphical user-interface. The performance of DARWIN was examined experimentally in several radiation fields. The results of the experiments indicated the accuracy and wide response range of DARWIN for measuring dose rates from neutrons, photons and muons with wide energies. It was also found from the experiments that DARWIN enables us to monitor small fluctuations of neutron dose rates near the background level because of its high sensitivity. With these properties, DARWIN will be able to play a very important role for improving radiation safety in high-energy accelerator facilities.

Measurement of Response Functions of a Liquid Organic Scintillator for Neutrons up to 800 Me V

Response functions of a BC501A liquid organic scintillator for neutrons up to 800 MeV have been measured at the heavy-ion accelerator of the National Institute of Radiological Sciences, Japan. A thick graphite target was bombarded with 400-MeV/u C ions and 800-MeV/u Si ions to produce high-energy neutrons whose kinetic energy was determined by the time-of-flight method. The measured response functions were compared with the results obtained using SCINFUL-QMD code, and the accuracy of the code was experimentally verified up to 800 MeV. This work will contribute to extending the energies measurable with our new radiation dose-monitoring system (DARWIN), which is based on the BC501A scintillator.

META‐ANALYSIS OF THE DIFFERENCES IN THE TIME TO ONSET OF ACTION BETWEEN ROCURONIUM AND VECURONIUM

1. The aim of the present study was to conduct a meta-analysis of the magnitude of differences in the onset of action (T(max)) between rocuronium and vecuronium. 2. A search was made in PubMed, EMBASE Drugs and Pharmacology, Cochrane Controlled Trials Register and Cochrane Database on Systematic Reviews. Studies comparing the T(max) at the adductor policies between rocuronium and vecuronium administered as an intravenous bolus were included in the study. Twenty-nine effect sizes obtained from 21 studies were included. 3. The result of the meta-analysis of differences was -57.9 s (95% confidence interval -71.4 to -44.3 s), favouring rocuronium over vecuronium. The smallest difference in T(max) between these neuromuscular-blocking agents was observed in children (-19.1 s). The difference in T(max) between rocuronium and vecuronium in female patients was -38.7 s. The difference in T(max) between rocuronium and vecuronium measured by electromyography was approximately 50% shorter than that determined by acceleromyography or mechanomyography. In a subanalysis between rocuronium 600 mg/kg versus vecuronium 100 mg/kg, the difference in T(max) between them was very similar to that obtained in the general meta-analysis. 4. According to subanalyses of patient age and sex, drug dose and neuromuscular monitoring systems, the T(max) of rocuronium was approximately 20-70 s faster than that of vecuronium.

Development of Dose Monitoring System Applicable to Various Radiations with Wide Energy Ranges

A new inventive radiation dose monitor, designated as DARWIN (Dose monitoring system Applicable to various Radiations with WIde energy raNges), has been developed for monitoring doses in workspaces and surrounding environments of high energy accelerator facilities. DARWIN is composed of a phoswitch-type scintillation detector, which consists of liquid organic scintillator BC501A coupled with ZnS(Ag) scintillation sheets doped with 6Li, and a data acquisition system based on a Digital-Storage-Oscilloscope. Scintillations from the detector induced by thermal and fast neutrons, photons and muons were discriminated by analyzing their waveforms, and their light outputs were directly converted into the corresponding doses by applying the G-function method. Characteristics of DARWIN were studied by both calculation and experiment. The calculated results indicate that DARWIN gives reasonable estimations of doses in most radiation fields. It was found from the experiment that DARWIN has an excellent property of measuring doses from all particles that significantly contribute to the doses in surrounding environments of accelerator facilities—neutron, photon and muon with wide energy ranges. The experimental results also suggested that DARWIN enables us to monitor small fluctuation of neutron dose rates near the background-level owing to its high sensitivity.

Development of Dose Monitoring System Applicable to Various Radiations with Wide Energy Ranges

A new inventive radiation dose monitor, designated as DARWIN (Dose monitoring system Applicable to various Radiations with WIde energy raNges), has been developed for monitoring doses in workspaces and surrounding environments of high energy accelerator facilities. DARWIN is composed of a phoswitch-type scintillation detector, which consists of liquid organic scintillator BC501A coupled with ZnS(Ag) scintillation sheets doped with 6Li, and a data acquisition system based on a Digital-Storage-Oscilloscope. Scintillations from the detector induced by thermal and fast neutrons, photons and muons were discriminated by analyzing their waveforms, and their light outputs were directly converted into the corresponding doses by applying the G-function method. Characteristics of DARWIN were studied by both calculation and experiment. The calculated results indicate that DARWIN gives reasonable estimations of doses in most radiation fields. It was found from the experiment that DARWIN has an excellent property of measuring doses from all particles that significantly contribute to the doses in surrounding environments of accelerator facilities—neutron, photon and muon with wide energy ranges. The experimental results also suggested that DARWIN enables us to monitor small fluctuation of neutron dose rates near the background-level owing to its high sensitivity.

Irradiation facility for radiobiology and molecular biophysics studies at the University of São Paulo Pelletron Accelerator laboratory

In this work, we describe the new facility for Radiobiology and Molecular Biophysics studies with charged particle beams, built at the University of São Paulo Pelletron Accelerator Laboratory. It consists of a dedicated beam line, sample holder and dose monitoring system. The beam line is designed in such a way that a 15 mm diameter and 2% uniformity external beam is delivered to the sample. In order to reach these beam features, the beam line is composed of one focusing system with tantalum slits and a Faraday cup, two scattering chambers with 1 mm tantalum collimators and 2 mg/cm 2 Au diffusing foils, and one 10 μm thick mylar foil serving as exit window. The sample holder has x, y and z movement with 10 μm precision and the dose monitoring system consists of one Si detector inside each scattering chamber, and one Si detector in air at the sample location. A multiwire position sensitive detector will be soon installed right before the exit window to monitor the beam shape and help in the beam uniformity measurements. The facility and tests of the beam uniformity and dose monitoring system are described. The dose tests are performed through the irradiation of LiF TLD-100 crystals and the comparison of their results with the calculated values based on the counting rate on the Si detectors.

Real-time measurement and audit of radiation dose to patients undergoing computed radiography.

A real-time patient dose monitoring system for auditing computed radiography is described. Technical data from each exposure and for every examination type are collected and sent by a network to a workstation, which calculates the moving average values of entrance skin dose and dose-area product from the 10 most recently examined patients. Comparison of averages with reference values generates warning messages if reference values are exceeded, prompting corrective action if necessary.

The electron dose monitoring and control system in EB radiation processing for wires and cables

This paper introduces a close-loop microcomputer control system used for EB radiation processing of wires and cables, which is based on the measurements and calculations of the absorbed dose distribution of 0.6–2.0 MeV electrons in circular compound materials. The calculation of electron energy deposition in 4-layer media is carried out by the bipartition model of electron transport. The design ideas, system configuration and implementation of this control system governed by a 586 personal computer under windows 98 OS are described in this paper. The field operation results such as control precision and step response curves of this system are also given. The control system has been used for EB radiation processing of wires.