When a calibration image is processed, the information is saved and will be used for all subsequent clinical images until a new. Complete epid dosimetry epiqa tm is a program that allows to convert a dosimetric image acquired by an epid into a dose map and to compare the dose map with a reference dose distribution. This work will contribute to a more consistent understanding and implementation of pixeltodose calibration methods for epid based imrt dosimetry. Pdf commissioning and evaluation of an electronic portal. We provide solutions in over 200 hospital centers in 38 countries. Software is required to analyze the results of epid measurements and produce predicted results to allow comparison. Epid calibration method for transit invivo dosimetry. Epid dosimetry 2d and 3d verification methods van elmpt et al.
Pretreatment dosimetry by means of 2dimensional 2d dosimeters or directly by the electronic portal imaging devices epids 1,2 is commonly used to assess the accuracy of computed treatment planning system tps and dose distributions of intensitymodulated radiotherapy imrt beams, but the method is time consuming and the dose differences. This work will contribute to a more consistent understanding and implementation of pixeltodose calibration methods for epidbased imrt dosimetry. Epid based transit dosimetry to monitor interfraction. See the epidos website for details and current releases. Adaptivo displays relevant information without overloading the user. Overlaying this calibration with an existing absolute calibration can give you a measurement of the overall accuracy.
The pdp software is commissioned for portal dosimetry in tps eclipse version11, varian, palo alto, ca, united states, at hospital of ain shams university, cairo. After the initial commissioning process, clinical experiments on phantom treatments were evaluated to assess the level of accuracy of the electronic portal imaging device epid based invivo dose verification. Epigray, epidbased transit dosimetry software receives a. Pdf dose calibration of epids for segmented imrt dosimetry. To perform qa for imrt with portal dosimetry, one uses analytic software to correlate the response of an amorphous silicon asi epid to the dose delivered by applying positionspecific factors from a dose calibration table. Patient specific pretreatment qa verification using an. The first step was calibration of the asi epid mounted on three linear accelerators clianc23exs, varian. Commissioning as electronic portal imaging device, epid. Dosimetry check uses the electronic portal imaging device epid or detector array to capture images measuring the xray intensity applied to the patient. The epid response depending on the beam mode, treatment time and static square field size was measured. Radiation therapy innovative, industryleading dosimetry solutions for safer cancer patient treatments. The epid response is graded to the extent that 1 cu is matched to 1 mu delivered. Epid qc phantom has been designed to check and monitor the image quality of epids used in highenergy photon beams. The program will default to the plan dose at the average isocenter of all the fields.
Epid qc phantom epidsoft software ptw freiburg gmbh. Epidbased in vivo dosimetry provides clinically more useful information and is less time consuming than patientspecific pretreatment dose verification. Select the gamma criteria values distance in cm and percent difference including the dose to compare to what the percent is of. This allows clinicians to spend more time on patients who need adjustments to their plans, while providing the justification necessary for billable replanning. Dosimetry calibration the dosimetric calibration was performed at the same sid used for the dark field and flood field calibration. Epid central signals, obtained at source to epid distances sed equal to 159cm or 150cm, were converted into dose at a reference point in the patient. The software recently received 510k clearance from the u. Epid in vivo dosimetry in rapidarc technique request pdf. Improved compare functions with different reference points for gamma index analysis and advanced 3 d gamma analysis. Epids have also been used for dosimetry in radiation therapy mcdermott et al 2004, winkler et al 2005, van esch et al 2004, greer and popescu 2003, siebers et al 2004, kirkby and sloboda 2005.
Many papers have reported on the use of epid dosimetry for patient. Evaluation of a fast method of epidbased dosimetry for. This reconstructed dose is then compared to the intended dose from the planning system. Succinct metrics and graphs communicate analysis and warnings, and user editable tolerances direct attention only when needed. The epid calibration method calculates portal dose values with an uncertainty of less than 3% 1 sd, the calibration of the mv conebeam ct scan into electron density values results in maximum differences of 2% in the dose distribution, and the 3d monte carlo based dose calculation evaluated for headandneck cancer patients showed. The dose response measured under different acquisition settings and different linacepid combinations matched closely. Either route will require substantial commissioning.
In addition to accurate 3d dose verification, in vivo epid based dosimetry will also detect major errors in the dose received by individual patients. This was performed using the truebeam imaging system calibration workflow. Iba dosimetry is the global market leader for independent integrated quality assurance solutions and services that maximize efficiency and minimize errors in radiation therapy, medical imaging, and calibration procedures. Independent verification of the dose delivered by complex radiotherapy can be performed by electronic portal imaging device epid dosimetry. Rit patient qa imrt, planbased calibration, batch analysis. This applies both internally, due to ingested or inhaled radioactive substances, or externally due to irradiation by sources of radiation.
Radiation dosimetry in the fields of health physics and radiation protection is the measurement, calculation and assessment of the ionizing radiation dose absorbed by an object, usually the human body. It also helps to easily determine which patients require replanning. For more information on ptw dosimetry and qa solutions, visit. In vivo dosimetry in uk external beam radiotherapy. It is possible to utilize epiqa for a verification of static as well as intensity modulated fields, including rapidarc fields. The graphical user interface gui has two principle functions which are a epid image calibration and b imrt qa. The epid shows promise as a device for verification of imrt, the major. Then dosimetric characteristics of the epid were investigated. Initial calibration of an inhouse software tool includes characterization of epid dosimetry parameters by importing dicom images of varying delivered mus to determine linear mapping factors in order to convert image pixel values to variandefined calibrated units cu. Learn more because this system is fully automated so that no physicist time is required for data acquisition and evaluation, daily patient treatment qa is feasible. Adaptivo drastically reduces the amount of time required for pretreatment qa when compared to using a phantom. It can also be used with an ion chamber array to produce fast absolute dose calibration at.
Clinical imrt epid dosimetry implemented with the different pixeltodose calibration methods indicated that calibration at 20 mu provides equivalent results to implementing a ghosting correction. The aim of this study is to evaluate the ability of transit dosimetry using commercial treatment planning system tps and an electronic portal imaging device epid with simple calibration method to verify the beam delivery based on detection of large errors in treatment room. As a result of the calibration the predict ed and measured fl uency map can be expressed in calibrated units cu. Calculate the transmissions from epid images of a large field passing through a series of homogeneous, planar, plastic phantoms, with different physical thicknesses. The essentials of epid based dosimetry are the accuracy of the imager calibration and the cal culation algorithm. Radiation calibration, qa, and dosimetry equipment stand. Epiqa tm is a program that allows to convert a dosimetric image acquired by an epid into a dose map and to compare the dose map with a reference dose distribution. Dosisoft sa, french software leader specialized in radiotherapy and medical imaging, is pleased to announce that epigray, epidbased transit dosimetry solution, has received a medical device licence from health canada, on the 2nd of february, 2016 and is now available for sale on the canadian market. X 10 cm, y 10 cm monitor units 100 1cu was scaled to 100 mu at sid 100cm.
The epid name can be different see the next example. Cureus commissioning and evaluation of an electronic. Vivo dosimetry software electronic portal imaging device. Afterwards, configuration of the calculation algorithm in tps was carried out. Epid based in vivo dosimetry provides clinically more useful information and is less time consuming than patientspecific pretreatment dose verification. This technique can be used to eliminate field size dependencies in film, epid and cr images. Routine epid invivo dosimetry in a reference point for. This calibration table is determined using the calibration protocol outlined in the portal dosimetry systems users.
Dosimetry and qa solutions for halcyon product overview. Patient specific pretreatment qa verification using an epid. Cureus commissioning and evaluation of an electronic portal. Epidbased dosimetry, in combination with inroom imaging, is a fast and accurate tool for 3d in vivo verification of vmat delivery. The investment in getting epid dosimetry into clinical use for ivd cannot be neglected in terms of either developing or purchasing software to facilitate ivd using the epid output. The versatile phantom provides a wide range of test elements to check all relevant quality parameters of mv imagers with a single beam in one image. Subsequently, the epigray calibration and conversion factors were defined. First step was calibration of the asi epid mounted on three linear accelerators clianc23exs, varian. Step wedge and uniform irradiation are the two options currently implemented for the calibration of the system. Twenty four fields of intensity modulated radiotherapy imrt plans were selected from four lung cancer patients.
Darkfield and floodfield calibration of all imrt scanning modes that shall be used for portal dosimetry, e. Results are analyzed in 3d using epid andor log file data, or in 2d through the transit dosimetry feature, with no additional time or effort required. When a calibration image is processed, the information is saved and will be used for all subsequent clinical images until a new calibration image is received and processed. Identify the calibration relationship between transmission and physical thickness of plastic phantom. The list of eight items would be repeated for a second and subsequent epids. Epid detector design, the linac, and the image acquisition and processing methods implemented across different systems. Epid based transit dosimetry to monitor interfraction variation in radiation therapy bawazeer, o 2018, epid based transit dosimetry to monitor interfraction variation in radiation therapy, doctor of philosophy phd, health and biomedical sciences, rmit university. All evaluations on this page were performed with version 2.
The dosimetry check software was used to evaluate patientspecific qa on the two imrt techniques step and shoot, as well as smart arc with measurements based on epid set to 110 cm sdd. Any inaccuracy in that proc ess could lead to inconsistency between the pre dicted and measured dose. Epid dosimetry configuration and pretreatment imrt. Dolphin transmission detector enables efficiency for patient qa measurements. Epigray was commissioned based on the companys instructions. Epiqa is a commercial software which we use for the independent verification of imrt treatments with the varian epid electronic portal imaging device. Clinical imrt epid dosimetry implemented with the different pixeltodose calibration methods indicated that calibration at 20 mu provides equivalent results to implementing a ghosting. New elekta iviewdose software designed to provide an. Portal dosimetry portal vision asi imager panel of varian clinac is used, with a pixel dimension and spatial resolution of 1024. The additional correction of the conversion factors reduced a systematic discrepancy between appa and lateral beams for single fields by 2%, which. Imrt patient plan verification software for comparing dose distributions measured in an imrt verification phantom with dose distributions computed by a rtps. Dosimetry check operating manual, page 12 of 43 for details see the plan section of the dosimetry check reference manual.
Webbased qa data management software trackit qa data management highlights integrated platform to automate and streamline data management in radiotherapy qa oneclick export of analyzed qa data from ptw devices. Once the dosimetry mode on the varian truebeam was calibrated, the data acquisition required for the software commissioning took about three hours of measurements per beam energy and per machine. The mu epid software has been developed using matlab version 9. The epid measurements were also found to depend on the input beam profile utilized for epid floodfield calibration. Evaluation of dosimetry check software for imrt patient. To calibrate the megavoltage mv dosimetry mode, diagonal beam profiles are imported as described in the varian user guide. Epid qc phantom and epidsoft software epid qc phantom has been designed to check and monitor the image quality of epids used in highenergy photon beams. The algorithms and the software, used to perform the ivd checks, are described elsewhere fidanzio 2010, et al piermattei et al 2012. Establishing action levels for epidbased qa for imrt. The analysis software follows the scaling, outputcorrection, and dose redistribution steps for these large epid calibration images outlined above, and then creates a pixelbypixel lookup table of pixel valuetodose calibration factors by referencing against the measured calibration absolute dose planes. The calibration of epid is done, where radiation beam is linked to calibration units cu. It provides the basic image quality uniformity etc. Dosimetry check dc operating manual math resolutions.
913 956 973 97 125 893 1181 76 219 1454 1457 1560 1422 1555 571 1200 469 1242 536 870 1077 900 1285 777 872 1281 918 707 1283 447 1322 1207 633 1109 1351 959 1180 769 132 1335 546 693 230