Measurement of rectum dose by in vivo alanine/ESR dosimetry in gynecological 192Ir HDR brachytherapy |
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| Institution: | 1. Departamento de Ingeniería Física DCI, Universidad de Guanajuato campus León, Guanajuato, Mexico;2. Departamento de Física, FFCLRP, Universidade de São Paulo, SP, Brazil;3. Faculdade de Medicina de Ribeirão Preto and Hospital das Clínicas-FMRP, Universidade de São Paulo, SP, Brazil;4. Hospital das Clínicas-FMRP, Universidade de São Paulo, SP, Brazil;5. Universidade de São Paulo, Faculdade de Filosofia Ciências e Letras de Ribeirão Preto, Departamento de Física, Av. Bandeirantes, 3900, Monte Alegre, 14040901, Ribeirão Preto, SP, Brazil;1. Department of Construction Engineering, Escola Politécnica, University of São Paulo, 05508-900 São Paulo, SP, Brazil;2. Instituto de Química, University of São Paulo, 05513-970 São Paulo, SP, Brazil;1. Área Mecánica de Fluidos, Campus Científico Tecnológico Linares, Universidad de Jaén, Cinturón Sur s/n, 23700 Linares, Spain;2. Departamento de Ciencias Agroforestales, ETSIA, Universidad de Sevilla, Ctra. Utrera km 1, 41013 Sevilla, Spain;3. Institute for Soil Sciences and Agricultural Chemistry, Centre for Agricultural Research, Hungarian Academy of Sciences, H-1022 Budapest, Herman Ottó út 15, Hungary;1. National Institute of Astrophysics, Optics and Electronics, INAOE, Electronics Group, Tonantzintla, Puebla 72840, Mexico;2. Meritorious Autonomous University of Puebla, BUAP, Puebla 72000, Mexico;3. University of Texas at San Antonio, College of Science Dean, One UTSA Circle, San Antonio, TX 78249, USA |
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| Abstract: | High dose rate (HDR) brachytherapy (BT) used in treatments of gynecological cancer often results in high doses in the pelvic organs at risk (OARs) and the complications in the rectum are a serious concern. Dosimetry procedures in vivo can be used as an evaluation method of calculated dose in treatment planning. One dosimetric method is the use of alanine with electron spin resonance (ESR) that has been used in different clinical practices. The aim of this study was to indicate the dose level in the female rectum volume, using alanine dosimeters during 192Ir HDR gynecological BT, for cervical cancer. Doses were compared with the values obtained using the computational treatment planning system based on two orthogonal radiographic images. Firstly a phantom study in water was performed, enabling the in vivo study. Ten patients had the dose in rectum measured, resulting from 10 points properly referred; variations found were in the range of +60% and −50% of the delivered doses compared to the treatment planning system. Differences between planned and measured doses can be mainly due to uncertainty of dosimeter position determination, averaging of dose points specified over the whole dosimeter position, uncontrolled changes in detector position during treatment due to rectum movement and to a simplified treatment system planning, that do not take into account the details of the patient anatomy and the difference among the tissues. Results show that improvements of the protocol treatment should be done to enhance the relation between treatment planning system and experimental results, nevertheless the dose at the OARs was lower than the recommended by the ICRU Report 38. |
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| Keywords: | Brachytherapy HDR Alanine Electron Spin Resonance |
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