skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: SU-F-T-63: Dosimetric Relevance of the Valencia and Leipzig HDR Applicators Plastic Cap

Abstract

Purpose: Utilization of HDR brachytherapy treatment of skin lesions using collimated applicators, such as the Valencia or Leipzig is increasing. These applicators are made of cup-shaped tungsten material in order to focalize the radiation into the lesion and to protect nearby tissues. These applicators have an attachable plastic cap that removes secondary electrons generated in the applicator and flattens the treatment surface. The purpose of this study is to examine the dosimetric impact of this cap, and the effect if the cap is not placed during the HDR fraction delivery. Methods: Monte Carlo simulations have been done using the code Geant4 for the Valencia and Leipzig applicators. Dose rate distributions have been obtained for the applicators with and without the plastic cap. An experimental study using EBT3 radiochromic film has been realized in order to verify the Monte Carlo results. Results: The Monte Carlo simulations show that absorbed dose in the first millimeter of skin can increase up to 180% for the Valencia applicator if the plastic cap is absent and up to 1500% for the Leipzig applicators. At deeper distances the increase of dose is smaller being about 10–15%. Conclusion: Important differences have been found if the plastic capmore » of the applicators is absent in the treatment producing an overdosage in the skin. The user should have a checklist to remind him check always before HDR fraction delivery to insure the plastic cap is placed on the applicator. This work was supported in part by Generalitat Valenciana under Project PROMETEOII/2013/010, by the Spanish Government under Project No. FIS2013-42156, and by a research agreement with Elekta Brachytherapy, Veenendaal, The Netherlands.« less

Authors:
 [1];  [2]; ;  [3];  [4]; ;  [5]
  1. ERESA-Hospital General Universitario, Valencia (Spain)
  2. National Dosimetry Centre (CND), Valencia (Spain)
  3. University of Valencia, Burjassot (Spain)
  4. Hospital La Fe, Valencia (Spain)
  5. Helen F. Graham Cancer Center, Christiana Care Health System, Newark, DE (United States)
Publication Date:
OSTI Identifier:
22642311
Resource Type:
Journal Article
Resource Relation:
Journal Name: Medical Physics; Journal Volume: 43; Journal Issue: 6; Other Information: (c) 2016 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
07 ISOTOPES AND RADIATION SOURCES; 60 APPLIED LIFE SCIENCES; ABSORBED RADIATION DOSES; BRACHYTHERAPY; COMPUTERIZED SIMULATION; DOSE RATES; MONTE CARLO METHOD; SKIN; TUNGSTEN

Citation Formats

Granero, D, Candela-Juan, C, Vijande, J, Ballester, F, Perez-Calatayud, J, Jacob, D, and Mourtada, F. SU-F-T-63: Dosimetric Relevance of the Valencia and Leipzig HDR Applicators Plastic Cap. United States: N. p., 2016. Web. doi:10.1118/1.4956469.
Granero, D, Candela-Juan, C, Vijande, J, Ballester, F, Perez-Calatayud, J, Jacob, D, & Mourtada, F. SU-F-T-63: Dosimetric Relevance of the Valencia and Leipzig HDR Applicators Plastic Cap. United States. doi:10.1118/1.4956469.
Granero, D, Candela-Juan, C, Vijande, J, Ballester, F, Perez-Calatayud, J, Jacob, D, and Mourtada, F. 2016. "SU-F-T-63: Dosimetric Relevance of the Valencia and Leipzig HDR Applicators Plastic Cap". United States. doi:10.1118/1.4956469.
@article{osti_22642311,
title = {SU-F-T-63: Dosimetric Relevance of the Valencia and Leipzig HDR Applicators Plastic Cap},
author = {Granero, D and Candela-Juan, C and Vijande, J and Ballester, F and Perez-Calatayud, J and Jacob, D and Mourtada, F},
abstractNote = {Purpose: Utilization of HDR brachytherapy treatment of skin lesions using collimated applicators, such as the Valencia or Leipzig is increasing. These applicators are made of cup-shaped tungsten material in order to focalize the radiation into the lesion and to protect nearby tissues. These applicators have an attachable plastic cap that removes secondary electrons generated in the applicator and flattens the treatment surface. The purpose of this study is to examine the dosimetric impact of this cap, and the effect if the cap is not placed during the HDR fraction delivery. Methods: Monte Carlo simulations have been done using the code Geant4 for the Valencia and Leipzig applicators. Dose rate distributions have been obtained for the applicators with and without the plastic cap. An experimental study using EBT3 radiochromic film has been realized in order to verify the Monte Carlo results. Results: The Monte Carlo simulations show that absorbed dose in the first millimeter of skin can increase up to 180% for the Valencia applicator if the plastic cap is absent and up to 1500% for the Leipzig applicators. At deeper distances the increase of dose is smaller being about 10–15%. Conclusion: Important differences have been found if the plastic cap of the applicators is absent in the treatment producing an overdosage in the skin. The user should have a checklist to remind him check always before HDR fraction delivery to insure the plastic cap is placed on the applicator. This work was supported in part by Generalitat Valenciana under Project PROMETEOII/2013/010, by the Spanish Government under Project No. FIS2013-42156, and by a research agreement with Elekta Brachytherapy, Veenendaal, The Netherlands.},
doi = {10.1118/1.4956469},
journal = {Medical Physics},
number = 6,
volume = 43,
place = {United States},
year = 2016,
month = 6
}
  • Purpose: High dose rate (HDR) brachytherapy for treatment of small skin lesions using the Leipzig and Valencia applicators is a widely used technique. These applicators are equipped with an attachable plastic cap to be placed during fraction delivery to ensure electronic equilibrium and to prevent secondary electrons from reaching the skin surface. The purpose of this study is to report on the dosimetric impact of the cap being absent during HDR fraction delivery, which has not been explored previously in the literature. Methods: GEANT4 Monte Carlo simulations (version 10.0) have been performed for the Leipzig and Valencia applicators with andmore » without the plastic cap. In order to validate the Monte Carlo simulations, experimental measurements using radiochromic films have been done. Results: Dose absorbed within 1 mm of the skin surface increases by a factor of 1500% for the Leipzig applicators and of 180% for the Valencia applicators. Deeper than 1 mm, the overdosage flattens up to a 10% increase. Conclusions: Differences of treating with or without the plastic cap are significant. Users must check always that the plastic cap is in place before any treatment in order to avoid overdosage of the skin. Prior to skin HDR fraction delivery, the timeout checklist should include verification of the cap placement.« less
  • Purpose: and Leipzig applicators (VLAs) are single-channel brachytherapy surface applicators used to treat skin lesions up to 2cm diameter. Source dwell times can be calculated and entered manually after clinical set-up or ultrasound. This procedure differs dramatically from CT-based planning; the novelty and unfamiliarity could lead to severe errors. To build layers of safety and ensure quality, a multidisciplinary team created a protocol and applied Failure Modes and Effects Analysis (FMEA) to the clinical procedure for HDR VLA skin treatments. Methods: team including physicists, physicians, nurses, therapists, residents, and administration developed a clinical procedure for VLA treatment. The procedure wasmore » evaluated using FMEA. Failure modes were identified and scored by severity, occurrence, and detection. The clinical procedure was revised to address high-scoring process nodes. Results: Several key components were added to the clinical procedure to minimize risk probability numbers (RPN): -Treatments are reviewed at weekly QA rounds, where physicians discuss diagnosis, prescription, applicator selection, and set-up. Peer review reduces the likelihood of an inappropriate treatment regime. -A template for HDR skin treatments was established in the clinical EMR system to standardize treatment instructions. This reduces the chances of miscommunication between the physician and planning physicist, and increases the detectability of an error during the physics second check. -A screen check was implemented during the second check to increase detectability of an error. -To reduce error probability, the treatment plan worksheet was designed to display plan parameters in a format visually similar to the treatment console display. This facilitates data entry and verification. -VLAs are color-coded and labeled to match the EMR prescriptions, which simplifies in-room selection and verification. Conclusion: Multidisciplinary planning and FMEA increased delectability and reduced error probability during VLA HDR Brachytherapy. This clinical model may be useful to institutions implementing similar procedures.« less
  • Purpose: To determine the correction factor of the correspondence factor for the Standard Imaging IVB 1000 well chamber for commissioning of Elekta’s Leipzig and Valencia skin applicators. Methods: The Leipzig and Valencia applicators are designed to treat small skin lesions by collimating irradiation to the treatment area. Published output factors are used to calculate dose rates for clinical treatments. To validate onsite applicators, a correspondence factor (CFrev) is measured and compared to published values. The published CFrev is based on well chamber model SI HDR 1000 Plus. The CFrev is determined by correlating raw values of the source calibration setupmore » (Rcal,raw) and values taken when each applicator is mounted on the same well chamber with an adapter (Rapp,raw). The CFrev is calculated by using the equation CFrev =Rapp,raw/Rcal,raw. The CFrev was measured for each applicator in both the SI HDR 1000 Plus and the SI IVB 1000. A correction factor, CFIVB for the SI IVB 1000 was determined by finding the ratio of CFrev (SI IVB 1000) and CFrev (SI HDR 1000 Plus). Results: The average correction factors at dwell position 1121 were found to be 1.073, 1.039, 1.209, 1.091, and 1.058 for the Valencia V2, Valencia V3, Leipzig H1, Leipzig H2, and Leipzig H3 respectively. There were no significant variations in the correction factor for dwell positions 1119 through 1121. Conclusion: By using the appropriate correction factor, the correspondence factors for the Leipzig and Valencia surface applicators can be validated with the Standard Imaging IVB 1000. This allows users to correlate their measurements with the Standard Imaging IVB 1000 to the published data. The correction factor is included in the equation for the CFrev as follows: CFrev= Rapp,raw/(CFIVB*Rcal,raw). Each individual applicator has its own correction factor, so care must be taken that the appropriate factor is used.« less
  • The nucletron Leipzig applicator is designed for (HDR) {sup 192}Ir brachy radiotherapy of surface lesions. The dosimetric characteristics of this applicator were investigated using simulation method based on Monte Carlo N-particle (MCNP) code and phantom measurements. The simulation method was validated by comparing calculated dose rate distributions of nucletron microSelectron HDR {sup 192}Ir source against published data. Radiochromic films and metal-oxide-semiconductor field-effect transistor (MOSFET) detectors were used for phantom measurements. The double exposure technique, correcting the nonuniform film sensitivity, was applied in the film dosimetry. The linear fit of multiple readings with different irradiation times performed for each MOSFET detectormore » measurement was used to obtain the dose rate of each measurement and to correct the source transit-time error. The film and MOSFET measurements have uncertainties of 3%-7% and 3%-5%, respectively. The dose rate distributions of the Leipzig applicator with 30 mm opening calculated by the validated MC method were verified by measurements of film and MOSFET detectors. Calculated two-dimensional planar dose rate distributions show similar patterns as the film measurement. MC calculated dose rate at a reference point defined at depth 5 mm on the applicator's central axis is 7% lower than the film and 3% higher than the MOSFET measurements. The dose rate of a Leipzig applicator with 30 mm opening at reference point is 0.241{+-}3% cGy h{sup -1} U{sup -1}. The MC calculated depth dose rates and profiles were tabulated for clinic use.« less
  • Purpose: To obtain the absolute dose-rate distribution in liquid water for all six cup-shaped Leipzig applicators by means of an experimentally validated Monte Carlo (MC) code. These six applicators were used in high-dose-rate (HDR) afterloaders with the 'classic' and v2 {sup 192}Ir sources. The applicators have an inner diameter of 1, 2, and 3 cm, with the source traveling parallel or perpendicular to the contact surface. Methods and materials: The MC GEANT4 code was used to obtain the dose-rate distribution in liquid water for the six applicators and the two HDR source models. To normalize the applicator output factors, amore » MC simulation for the 'classic' and v2 sources in air was performed to estimate the air-kerma strength. To validate this specific application and to guarantee that realistic source-applicator geometry was considered, an experimental verification procedure was implemented in this study, in accordance with the TG43U1 recommendations. Thermolumniscent dosimeter chips and a parallel plate ionization chamber in a polymethyl methacrylate (PMMA) phantom were used to verify the MC results for the six applicators in a microSelectronHDR afterloader with the 'classic' source. Dose-rate distributions dependence on phantom size has been evaluated using two different phantom sizes. Results: Percentage depth dose and off-axis profiles were obtained normalized at a depth of 3 mm along the central axis for both phantom sizes. A table of output factors, normalized to 1 U of source kerma strength at this depth, is presented. The dose measured in the PMMA phantom agrees within experimental uncertainties with the dose obtained by the MC GEANT4 code calculations. The phantom size influence on dose-rate distributions becomes significant at depths greater than 5 cm. Conclusions: MC-detailed simulation was performed for the Nucletron Leipzig HDR applicators. The matrix data obtained, with a grid separation of 0.5 mm, can be used to build a dataset in a convenient format to model these distributions for routine use with a brachytherapy treatment planning system.« less