Valencia Applicator Research Articles

Dosimetry of Large Field Valencia applicators for Cobalt-60-based brachytherapy.

Non-melanoma skin cancer is one of the most common types of cancer and one of the main approaches is brachytherapy. For small lesions, the treatment of this cancer with brachytherapy can be done with two commercial applicators, one of these is the Large Field Valencia Applicators (LFVA). The aim of this study is to test the capabilities of the LFVA to use clinically 60Co sources instead of the 192Ir ones. This study was designed for the same dwell positions and weights for both sources. The Penelope Monte Carlo code was used to evaluate dose distribution in a water phantom when a 60Co source is considered. The LFVA design and the optimized dwell weights reported for the case of 192Ir are maintained with the only exception of the dwell weight of the central position, that was increased. 2D dose distributions, field flatness, symmetry and the leakage dose distribution around the applicator were calculated. When comparing the dose distributions of both sources, field flatness and symmetry remain unchanged. The only evident difference is an increase of the penumbra regions for all depths when using the 60Co source. Regarding leakage, the maximum dose within the air volume surrounding the applicator is in the order of 20% of the prescription dose for the 60Co source, but it decreases to less than 5% at about 1cm distance. Flatness and symmetry remains unaltered as compared with 192Ir sources, while an increase in leakage has been observed. This proves the feasibility of using the LFVA in a larger range of clinical applications.

HDR brachytherapy in keratinocyte skin carcinomas - Single center experience with analysis of clinical, dosimetric, and radiobiological factors in acute skin toxicity

PURPOSERadiotherapy techniques have been utilized to treat keratinocyte skin carcinoma (KSC). The objective of this study was to report the results of patients with KSC treated with HDR brachytherapy, with a variety of techniques and applicators. A statistical analysis of clinical, radiobiological, and technical factors has been made to analyze those factors related to skin acute toxicity, focused on acute epithelitis G3. METHODS AND MATERIALSBetween February 2005 and August 2020, 93 patients with 120 histologically proven KSC have been treated in our Institution. BT treatment has been performed using superficial BT/plesiotherapy (Valencia applicator (22%), flaps (48%), customized molds (4%) or interstitial techniques (26%)). The indications of BT were primary/definitive in 38 treatments (32%) or adjuvant/postoperative in 82 (68%). In 14 (17%) of the 82 operated patients a skin graft. Mean comparison t tests were performed for quantitative variables, and percentage comparison Chi2 tests for qualitative. Multivariate binomial logistic regression models were done. RESULTSMedian follow-up was 36.5 months (range 5–141). Local control was achieved in 110 treatments (92%). Acute toxicity, dermatitis, was G1 7%; G2, 57% and G3 38%. The main factors statistically associated to the appearance of dermatitis G3 were the total dose, the volume treated, and the use of manufactured flaps. The main protective factor against dermatitis G3 was implant of skin graft. CONCLUSIONSIn KSC BT the use of manufactured flap is accompanied by greater EG3, only with a relationship with the volume of treatment and total dose.

In Vivo Dosimetry for Superficial High Dose Rate Brachytherapy with Optically Stimulated Luminescence Dosimeters: A Comparison Study with Metal-Oxide-Semiconductor Field-Effect Transistors

The purpose of the study was to calibrate and commission optically-stimulated luminescence dosimeters (OSLDs) for in vivo measurements in contact-based 192Ir treatments for superficial high dose rate (HDR) brachytherapy in place of metal-oxide-semiconductor field-effect transistors (MOSFETs). Dose linearity and dose rate dependence were tested by varying source-to-OSLD distance and dwell time. Angular dependence was measured using a solid water phantom setup for OSLD rotation. A group of OSLDs were readout 34 consecutive times to test readout depletion while OSLDs were optically annealed using a mercury lamp for 34.7 h. End-to-end tests were performed using a Freiburg flap and Valencia applicator. OSLD measurements were compared to MOSFETs and treatment planning system (TPS) doses. OSLD response was supralinear for doses above 275 cGy. They were found to be independent of dose rate and dependent on the incident angle in edge-on scenarios. OSLDs exhibited minimal readout depletion and were successfully annealed after 24 h of illumination. Freiburg flap measurements agreed well with the TPS. For the Valencia, OSLDs showed to be the more accurate system over MOSFETs, with a maximum disagreement with the TPS being 0.09%. As such, OSLDs can successfully be used in place of MOSFETs for in vivo dosimetry for superficial HDR brachytherapy.

Two different sizes of Valencia applicators in non-melanoma skin cancer treatment with iridium-192 high-dose-rate brachytherapy.

PurposeThe aim of this retrospective study was to analyze tumor control, toxicity, and aesthetic outcome of patients affected by non-melanoma skin cancer (NMSC) and treated with iridium-192 (192Ir) high-dose-rate (HDR) brachytherapy (BT) using Valencia applicators at the Division of Radiotherapy, University of Pisa.Material and methodsFrom June 2015 to December 2020, 95 NMSC patients, including 61.5% basal cell carcinoma and 38.5% squamous cell carcinoma patients, with median age of 83 years (range, 32-96 years) were treated. In total, 182 lesions with a diameter ≤ 25 mm (median, 12 mm) and a depth ≤ 4 mm, located in scalp (19.2%), face (20.9%), chest (8.8%), nose (16.5%), ear (15.4%), and extremities (19.2%) were analyzed. All lesions were treated with 192Ir-based HDR afterloader using Valencia applicators. 105 lesions (57.7%) were treated with applicator of 20 mm and 77 lesions (42.3%) with applicator of 30 mm in diameter, depending on the size of lesions. Prescribed dose was 40 Gy in 8 fractions (5 Gy/fraction) delivered 2-3 times a week. Biological effective dose (BED) was ≈ 60 Gy.ResultsThe median follow-up was 14 months (range, 3-59 months). The 2-year local control rate was 96%. According to common terminology criteria for adverse events (CTCAE v. 5.0), G1-G2 acute toxicities included dermatitis (22.0%) and pain (8.2%). The most common G1 late toxicities were hypopigmentation (27.5%) and fibrosis (8.2%), and G2 late toxicity included ulceration (0.5%). No G3 or higher acute or late toxicities were reported. Excellent cosmetic results were observed in 77.5% of the lesions, with one only (0.5%) reported as a poor cosmetic result (ulceration refractory to therapy).ConclusionsHDR-BT using Valencia applicators is a safe, effective, and well-tolerated treatment modality for NMSC, and can be considered a good alternative for treatment, especially in elderly patients who are often unfit for surgery.

High-dose-rate brachytherapy in the treatment of skin Kaposi sarcoma.

PurposeThe aim of the study is to review our experience in treatment of Kaposi sarcoma (KS) lesions with high-dose-rate (HDR) brachytherapy.Material and methodsWe present five new KS lesions (three patients) that were treated in our hospital from May 2016 to February 2017 with HDR brachytherapy using Valencia applicators. The treatment was delivered in 5 Gy fractions over five sessions, on alternate days. Total dose of 25 Gy (EQD2 31.25 Gy) was delivered. All patients were male, Caucasian, without a history of HIV, organ transplantation, or current immunosuppressive therapy. The median age was 76 years.ResultsAll lesions (100%) were located in lower limbs (60% in the ankle, 20% in the leg, and 20% in the foot), and their development was progressive. No lesion was greater than 2 cm (range, 0.5-1.5 cm). With a median follow-up of 15 months, all patients had a complete response to the treatment, with no evidence of local recurrence or tumor progression. Most of the patients (80%) had no acute toxicity; only one patient developed erythema grade 2.ConclusionsHDR brachytherapy could be a good option of treatment for these types of lesions, especially in elderly patients, or when cosmetic results are not good after surgery. Brachytherapy with the Valencia applicator, using hypofractionated regimen provides excellent results in terms of cosmetic and local control, and furthermore, facilitates treatment compliance, which is very relevant in elderly patients. HDR brachytherapy offers a simple, safe, quick, and attractive non-surgical treatment option.

SU‐F‐T‐23: Correspondence Factor Correction Coefficient for Commissioning of Leipzig and Valencia Applicators with the Standard Imaging IVB 1000

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 setup (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.

SU-G-201-05: Comparison of Different Methods for Output Verification of Eleckta Nucletron's Valencia Skin Applicators

Purpose: The provided output factors for Elekta Nucletron's skin applicators are based on Monte Carlo simulations. These outputs have not been independently verified, and there is no recognized method for output verification of the vendor's applicators. The purpose of this work is to validate the outputs provided by the vendor experimentally. Methods: Using a Flexitron Ir-192 HDR unit, three experimental methods were employed to determine dose with the 30 mm diameter Valencia applicator: first a gradient method using extrapolation ionization chamber (Far West Technology, EIC-1) measurements in solid water phantom at 3 mm SCD was used. The dose was derived based on first principles. Secondly a combination of a parallel plate chamber (Exradin A-10) and the EIC-1 was used to determine air kerma at 3 mm SCD. The air kerma was converted to dose to water in line with TG-61 formalism by using a muen ratio and a scatter factor measured with the skin applicators. Similarly a combination of the A-10 parallel plate chamber and gafchromic film (EBT 3) was also used. The Nk factor for the A-10 chamber was obtained through linear interpolation between ADCL supplied Nk factors for Cs-137 and M250. Results: EIC-1 measurements in solid water defined the outputs factor at 3 mm as 0.1343 cGy/U hr. The combination of A-10/ EIC-1 and A-10/EBT3 lead to output factors of 0.1383 and 0.1568 cGy/U hr, respectively. For comparison the output recommended by the vendor is 0.1659 cGy/U hr. Conclusion: All determined dose rates were lower than the vendor supplied values. The observed discrepancy between extrapolation chamber and film methods can be ascribed to extracameral gradient effects that may not be fully accounted for by the former method.

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

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.

New HDR Valencia Applicator for Treating Skin Lesions Larger Than 3 cm Size with Either a Co-60 or Ir-192 Source

New HDR Valencia Applicator for Treating Skin Lesions Larger Than 3 cm Size with Either a Co-60 or Ir-192 Source

Technical Note: Dosimetry of Leipzig and Valencia applicators without the plastic cap.

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. geant4 Monte Carlo simulations (version 10.0) have been performed for the Leipzig and Valencia applicators with and without the plastic cap. In order to validate the Monte Carlo simulations, experimental measurements using radiochromic films have been done. 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. 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.

EP-1992: Design and characterization of a new HDR brachytherapy Valencia applicator for larger skin lesions

EP-1992: Design and characterization of a new HDR brachytherapy Valencia applicator for larger skin lesions

Design and characterization of a new high-dose-rate brachytherapy Valencia applicator for larger skin lesions.

The aims of this study were (i) to design a new high-dose-rate (HDR) brachytherapy applicator for treating surface lesions with planning target volumes larger than 3 cm in diameter and up to 5 cm in size, using the microSelectron-HDR or Flexitron afterloader (Elekta Brachytherapy) with a (192)Ir source; (ii) to calculate by means of the Monte Carlo (MC) method the dose distribution for the new applicator when it is placed against a water phantom; and (iii) to validate experimentally the dose distributions in water. The penelope2008 MC code was used to optimize dwell positions and dwell times. Next, the dose distribution in a water phantom and the leakage dose distribution around the applicator were calculated. Finally, MC data were validated experimentally for a (192)Ir mHDR-v2 source by measuring (i) dose distributions with radiochromic EBT3 films (ISP); (ii) percentage depth-dose (PDD) curve with the parallel-plate ionization chamber Advanced Markus (PTW); and (iii) absolute dose rate with EBT3 films and the PinPoint T31016 (PTW) ionization chamber. The new applicator is made of tungsten alloy (Densimet) and consists of a set of interchangeable collimators. Three catheters are used to allocate the source at prefixed dwell positions with preset weights to produce a homogenous dose distribution at the typical prescription depth of 3 mm in water. The same plan is used for all available collimators. PDD, absolute dose rate per unit of air kerma strength, and off-axis profiles in a cylindrical water phantom are reported. These data can be used for treatment planning. Leakage around the applicator was also scored. The dose distributions, PDD, and absolute dose rate calculated agree within experimental uncertainties with the doses measured: differences of MC data with chamber measurements are up to 0.8% and with radiochromic films are up to 3.5%. The new applicator and the dosimetric data provided here will be a valuable tool in clinical practice, making treatment of large skin lesions simpler, faster, and safer. Also the dose to surrounding healthy tissues is minimal.

Commissioning and quality assurance procedures for the HDR Valencia skin applicators

The Valencia applicators (Nucletron, an Elekta company, Elekta AB, Stockholm, Sweden) are cup-shaped tungsten applicators with a flattening filter used to collimate the radiation produced by a high-dose-rate (HDR) 192Ir source, and provide a homogeneous absorbed dose at a given depth. This beam quality provides a good option for the treatment of skin lesions at shallow depth (3-4 mm). The user must perform commissioning and periodic testing of these applicators to guarantee the proper and safe delivery of the intended absorbed dose, as recommended in the standards in radiation oncology.In this study, based on AAPM and GEC-ESTRO guidelines for brachytherapy units and our experience, a set of tests for the commissioning and periodic testing of the Valencia applicators is proposed. These include general considerations, verification of the manufacturer documentation and physical integrity, evaluation of the source-to-indexer distance and reproducibility, setting the library plan in the treatment planning system, evaluation of flatness and symmetry, absolute output and percentage depth dose verification, independent calculation of the treatment time, and visual inspection of the applicator before each treatment. For each test, the proposed methodology, equipment, frequency, expected results, and tolerance levels (when applicable) are provided.

3316 Non-melanoma skin cancer treated with HDR Brachytherapy and Valencia applicator in elderly patients

3316 Non-melanoma skin cancer treated with HDR Brachytherapy and Valencia applicator in elderly patients

SU-F-BRA-07: Dosimetric Verification of the Valencia Skin Applicator Using Gafchromic EBT3 Film

Purpose: The Valencia applicators have recently been introduced for HDR treatment of small and shallow superficial skin lesions (< 20 mm diameter and 3-mm depth). Per AAPM TG 56, any HDR applicator internal dimensions must be verified prior to clinical use. However radiographic and tomographic imaging to validate the Valencia applicators is impractical due to the Tungsten alloy housing and flattening filter. In this study, we propose to use EBT3 film to indirectly confirm the physical integrity of the Valencia applicators. Methods: Treatment plans were created using the Oncentra MasterPlan TPS v4.5 for the H2 (20-mm dia.) and H3 (30-mm dia.) Valencia Applicators. A virtual CT phantom (2-mm slice thickness) was created with one source position in water. The published effective depth method was used for each applicator to delivery 500 cGy to a 3-mm depth using the TG-43 formalism. Film measurements (n=3) at 3-mm depth and vertical plane in solid water were performed for each applicator to verify the prescribed dose calculated by the TPS. Percent depth dose curves and off-axis profiles (phantom surface and 3-mm depth) were measured and compared to published data. Films were analyzed using an in-house written program and RIT113 v6 software. Film calibration was performed per TG-55 protocol using the Ir-192 source with NIST-traceable calibration. Results: The prescription absolute dose difference was 1% for the Valencia H2 applicator and 4% for the Valencia H3 applicator. The measured percent depth dose curves and off-axis dose profiles measured for the H2 and H2 Valencia applicators are in excellent agreement with the Granero et al. Monte Carlo results1. Conclusion: Gafchromic EBT3 film can be used to indirectly verify the internal components of special HDR skin applicators constructed from high Z materials.1Granero et al. “Design and evaluation of a HDR skin applicator with flattening filter”, Med. Phys. 35(2), 495–503, 2008

Non-melanoma skin cancer treated with high-dose-rate brachytherapy and Valencia applicator in elderly patients: a retrospective case series.

PurposeThe incidence of non-melanoma skin cancer (NMSC) has been increasing over the past 30 years. Basal cell carcinoma and squamous cell carcinoma are the two most common subtypes of NMSC. The aim of this study was to estimate tumour control, toxicity, and aesthetic events in elderly patients treated with high-dose-rate (HDR) brachytherapy (BT) using Valencia applicator.Material and methodsFrom January 2012 to May 2015, 57 lesions in 39 elderly eligible patients were enrolled. All the lesions had a diameter ≤ 25 mm (median: 12.5 mm) and a depth ≤ 4 mm. The appropriate Valencia applicator, 2 or 3 cm in diameter was used. The prescribed dose was 40 Gy in 8 fractions (5 Gy/fraction) in 48 lesions (group A), and 50 Gy in 10 fractions (5 Gy/fraction) in 9 lesions (group B), delivered 2/3 times a week. The biological effective dose (BED) was 60 Gy and 75 Gy, respectively.ResultsAfter median follow-up of 12 months, 96.25% lesions showed a complete response and only two cases presented partial remission. Radiation Therapy Oncology Group – European Organization for Research and Treatment of Cancer (RTOG/EORTC) G 1-2 acute toxicities were observed in 63.2% of the lesions: 56.3% in group A and 77.7% in group B. Late G1-G2 toxicities was observed in 19.3% of the lesions: 18.8% in group A and 22.2% in group B, respectively. No G3 or higher acute or late toxicities occurred. In 86% of the lesions, an excellent cosmetic result was observed (87.5% in group A and 77.8% in group B). Six lesions had a good cosmetic outcome and only 2.3% presented a fair cosmetic impact.ConclusionsThe treatment of NMSC with HDR-BT using Valencia surface applicator is effective with excellent and good cosmetics results in elderly patients. The hypofractionated course appears effective and no statistical differences were observed between the two groups analysed.

HDR Valencia Applicator in Nonmelanoma Skin Cancer: Clinical Outcomes

Non melanoma skin cancer (NMSC) is the most common malignancy. For many decades, radiation therapy (RT) has played a significant role in treating NMSC. High Dose Rate (HDR) brachytherapy (BT) approaches have a paramount relevance due to their adaptability, patient protection and variable dose fractionation schedules. Several innovative applicators have been introduced to the BT community and the use of skin BT has increased significantly. The Valencia applicator is a new superficial device that improves the dose distribution compared with the Leipzig applicator design.

SU‐E‐T‐343: Valencia Applicator Commissioning Using a Micro‐Chamber Array

Purpose:In the commissioning and QA of surface isotope‐based applicators, source‐indexer distance (SID) has a great influence in the flatness, symmetry and output. To these purposes, methods described in the literature are the use of a special insert at the entrance of dwell chamber or radiochromic films. Here we present the experience with a micro‐chamber array to perform the commissioning and QA of Valencia applicators.Methods:Valencia applicators have been used, the classic and the new extra‐shielded version. A micro‐chamber array has been employed, 1000 SRS (PTW), with 977 liquid filled, 2.3×2.3×0.5 mm3 sized ion chambers covering 11×11 cm2, which spacing is 2.5 mm in the central 5.5×5.5 cm2, dedicated mainly in principle, in conjunction with Octavius 4D (PTW), to IMRT, VMAT, SBRT verifications. Verisoft software that allows for 3D and planar analysis has been used to evaluate the results. Applicators were located on the surface of the array. To verify the SID, measurements corresponding to the reference value, SID ± 1 mm and SID ± 2 mm were acquired (integration time was fixed in order to discard the influence of the source entrance/exit). Once SID was determined, standard protocol treatments corresponding to 3 Gy and 7 Gy were acquired in order to establish typical patient dose distribution.Results:The method is fast and sensitive. The SID obtained was 1321 mm which is the nominal value included in the applicator manual. For example at 1319 mm an asymmetry of ±8% with respect to the central value was measured, along with a central deviation of −4% referred to 1321 mm.Conclusion:A practical method for the commissioning and QA of Valencia applicators has been described. It has been shown that it is an efficient and accurate tool for these purposes as well as for the verification of the absolute output constancy.

Correction Required for Formula Used to Determine “Correspondence Factor” of the Valencia Skin Applicator

The Valencia applicator set is used with the MicroSelectron HDR system for brachytherapy treatment of superficial skin lesion. It is designed with a fixed flattening filter built in and uses tungsten-alloy shielding to limit irradiation to the required area. Determination of distal reference distance of the applicator prior to clinical use is required to ensure the source is in the correct position, which is in the middle of the applicator shielding. The output factor verification per manufacturer is done by measurement using well chamber and calculating the manufacturer defined “correspondence factor” (CF).

The use of Valencia applicators at extended source surface distances for irregular surface contours

The use of Valencia applicators across irregular surface contours results in significant dose heterogeneities at the prescription depth. Investigations were carried out using extended source surface distances (standoff) to reduce these dose heterogeneities. Relative output factors were measured with a Roos chamber and Gafchromic EBT3 film was used to measure profiles and percentage depth doses at numerous standoff distances. The use of 20 mm standoff was found to reduce the relative difference in delivered dose across a 4 mm change in surface contour by 10.6% for the H2 applicator and 10.0% for the H3 applicator. The radiation became more penetrating with standoff and the field size larger, as expected. The results show that standoff can be used with the Valencia applicator to reduce dose heterogeneities across changes in surface contour.