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1.
J Appl Clin Med Phys ; 13(1): 3585, 2012 Jan 05.
Artigo em Inglês | MEDLINE | ID: mdl-22231210

RESUMO

The purpose of this study was to develop and evaluate filmless quality assurance (QA) tools for helical tomotherapy by using the signals from the on-board megavoltage computed tomography (MVCT) detector and applying a dedicated step-wedge phantom. The step-wedge phantom is a 15 cm long step-like aluminum block positioned on the couch. The phantom was moved through the slit beam and MVCT detector signals were analyzed. Two QA procedures were developed, with gantry fixed at 0°: 1) step-wedge procedure: to check beam energy consistency, field width, laser alignment with respect to the virtual isocenter, couch movement, and couch velocity; and 2) completion procedure: to check the accuracy of a field abutment made by the tomotherapy system after a treatment interruption. The procedures were designed as constancy tool and were validated by measurement of deliberately induced variations and comparison with a reference method. Two Hi-Art II machines were monitored over a period of three years using the step-wedge procedures. The data acquisition takes 5 minutes. The analysis is fully automated and results are available directly after acquisition. Couch speed deviations up to 2% were induced. The mean absolute difference between expected and measured couch speed was 0.2% ± 0.2% (1 standard deviation SD). Field width was varied around the 10 mm nominal size, between 9.7 and 11.1 mm, in steps of 0.2 mm. Mean difference between the step-wedge analysis and the reference method was < 0.01 mm ± 0.03 mm (1 SD). Laser (mis)alignment relative to a reference situation was detected with 0.3 mm precision (1SD). The step-wedge profile was fitted to a PDD in water. The PDD ratio D20/D10, measured at depths of 20 cm and 10 cm, was used to check beam energy consistency. Beam energy variations were induced. Mean difference between step-wedge and water PDD ratios was 0.2% ± 0.3% (1SD). The completion procedure was able to reveal abutment mismatches with a mean error of -0.6 mm ± 0.2 mm (1SD). The trending data over a period of three years showed a mean deviation of 0.4% ± 0.1% (1 SD) in couch speed. The spread in field width was 0.15 mm (1 SD). The sagittal and transverse lasers showed a variation of 0.5 mm (1 SD). Beam energy varied 1.0% (1 SD). A mean abutment mismatch was found of -0.4 mm ± 0.2 mm (1 SD) between interrupted treatments. The on-board MVCT detector, in combination with the step-wedge phantom, is a suitable tool for a QA program for helical tomotherapy. The method allowed frequent monitoring of machine behavior for the past three years.


Assuntos
Imagens de Fantasmas/normas , Garantia da Qualidade dos Cuidados de Saúde/normas , Radiometria/normas , Radioterapia Conformacional/instrumentação , Radioterapia Conformacional/normas , Tomografia Computadorizada por Raios X/instrumentação , Tomografia Computadorizada por Raios X/normas , Guias como Assunto , Países Baixos , Radiometria/instrumentação
2.
Radiother Oncol ; 84(1): 49-51, 2007 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-17561295

RESUMO

A clip forceps was developed which can insert markers at the border of a bladder tumour through a rigid cystoscope. This technique proved to be simple and safe and is of help for delineation of the target volume during CT simulation for focal boost irradiation of bladder cancer.


Assuntos
Cistoscopia/métodos , Carga Tumoral , Neoplasias da Bexiga Urinária/diagnóstico por imagem , Neoplasias da Bexiga Urinária/radioterapia , Cistoscópios , Estudos de Viabilidade , Feminino , Humanos , Masculino , Instrumentos Cirúrgicos , Tomografia Computadorizada por Raios X , Neoplasias da Bexiga Urinária/patologia
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