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Gimenez-Alventosa V, Gimenez V, Ballester F, Vijande J, Andreo P. Correction factors for ionization chamber measurements with the 'Valencia' and 'large field Valencia' brachytherapy applicators. Phys Med Biol 2018; 63:125004. [PMID: 29726409 DOI: 10.1088/1361-6560/aac27a] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Treatment of small skin lesions using HDR brachytherapy applicators is a widely used technique. The shielded applicators currently available in clinical practice are based on a tungsten-alloy cup that collimates the source-emitted radiation into a small region, hence protecting nearby tissues. The goal of this manuscript is to evaluate the correction factors required for dose measurements with a plane-parallel ionization chamber typically used in clinical brachytherapy for the 'Valencia' and 'large field Valencia' shielded applicators. Monte Carlo simulations have been performed using the PENELOPE-2014 system to determine the absorbed dose deposited in a water phantom and in the chamber active volume with a Type A uncertainty of the order of 0.1%. The average energies of the photon spectra arriving at the surface of the water phantom differ by approximately 10%, being 384 keV for the 'Valencia' and 343 keV for the 'large field Valencia'. The ionization chamber correction factors have been obtained for both applicators using three methods, their values depending on the applicator being considered. Using a depth-independent global chamber perturbation correction factor and no shift of the effective point of measurement yields depth-dose differences of up to 1% for the 'Valencia' applicator. Calculations using a depth-dependent global perturbation factor, or a shift of the effective point of measurement combined with a constant partial perturbation factor, result in differences of about 0.1% for both applicators. The results emphasize the relevance of carrying out detailed Monte Carlo studies for each shielded brachytherapy applicator and ionization chamber.
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Affiliation(s)
- V Gimenez-Alventosa
- Instituto de Instrumentación para Imagen Molecular (I3M), Centro Mixto CSIC-Universitat Politècnica de València, 46022 Valencia, Spain
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Rodríguez S, Arenas M, Gutierrez C, Richart J, Perez-Calatayud J, Celada F, Santos M, Rovirosa A. Recommendations of the Spanish brachytherapy group (GEB) of Spanish Society of Radiation Oncology (SEOR) and the Spanish Society of Medical Physics (SEFM) for high-dose rate (HDR) non melanoma skin cancer brachytherapy. Clin Transl Oncol 2017; 20:431-442. [PMID: 28808925 DOI: 10.1007/s12094-017-1733-z] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2017] [Accepted: 07/28/2017] [Indexed: 12/13/2022]
Abstract
Clinical indications of brachytherapy in non-melanoma skin cancers, description of applicators and dosimetry recommendations are described based on the literature review, clinical practice and experience of Spanish Group of Brachytherapy and Spanish Society of Medical Physics reported in the XIV Annual Consensus Meeting on Non Melanoma Skin Cancer Brachytherapy held in Benidorm, Alicante (Spain) on October 21st, 2016. All the recommendations for which consensus was achieved are highlighted in blue. Regular and small surfaces may be treated with Leipzig, Valencia, flap applicators or electronic brachytherapy (EBT). For irregular surfaces, customized molds or interstitial implants should be employed. The dose is prescribed at a maximum depth of 3-4 mm of the clinical target volume/planning target volume (CTV/PTV) in all cases except in flaps or molds in which 5 mm is appropriate. Interstitial brachytherapy should be used for CTV/PTV >5 mm. Different total doses and fraction sizes are used with very similar clinical and toxicity results. Hypofractionation is very useful twice or 3 times a week, being comfortable for patients and practical for Radiotherapy Departments. In interstitial brachytherapy 2 fractions twice a day are applied.
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Affiliation(s)
- S Rodríguez
- Radiation Oncology Department, Hospital Clínica Benidorm, Av. Alfonso Puchades 8, 30501, Benidorm, Alicante, Spain.
| | - M Arenas
- Radiation Oncology Department, Hospital Universitari Sant Joan de Reus, Tarragona, Spain
| | - C Gutierrez
- Radiation Oncology Department, Institut Català d'Oncologia, Hospitalet de Llobregat, Catalonia, Spain
| | - J Richart
- Radiation Oncology Department, Hospital Clínica Benidorm, Av. Alfonso Puchades 8, 30501, Benidorm, Alicante, Spain
| | - J Perez-Calatayud
- Radiation Oncology Department, Hospital La Fe-IRIMED, Valencia, Spain
| | - F Celada
- Radiation Oncology Department, Hospital La Fe-IRIMED, Valencia, Spain
| | - M Santos
- Radiation Oncology Department, Hospital Clínica Benidorm, Av. Alfonso Puchades 8, 30501, Benidorm, Alicante, Spain
| | - A Rovirosa
- Radiation Oncology Department, ICMHO, Hospital Clínic I Universitari, Barcelona, Spain
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