SU-FF-T-128: A Novel Approach for Measurement of Dosimetric Leaf Gap for a Rounded Leaf End Multi-Leaf Collimator

Abstract Modern treatment machines have shown small inter-unit variability regarding beam data. Recently, vendor-provided average beam data, such as the Representative Beam Data (RBD) of the TrueBeam (Varian Medical Systems, Palo Alto, CA, USA), has been used for modeling of the Eclipse (Varian Medical Systems) treatment planning system. However, RBD does not provide multi-leaf collimator (MLC) parameters, such as MLC leaf transmission factor (LTF) and dosimetric leaf gap (DLG). We performed a web-based multi-institutional survey to investigate these parameters as well as the measurement protocols and customization of the parameters for intensity-modulated radiotherapy (IMRT) and/or volumetric modulated radiotherapy (VMAT) commissioning. We collected 69 sets of linear accelerator (linac) data from 58 institutions. In order to measure MLC parameters, most institutions used farmer-type ionization chambers with a sensitive volume of 0.6 cm3, water phantoms, source surface distance of 90 cm with 10 cm depth, and a vendor-provided plan. The LTF showed small inter-unit variabilities, although the DLG showed large variations. For optimization of the parameters for IMRT/VMAT calculations, DLG values were upwardly adjusted at many institutions, whereas the LTF values were modestly changed. We clarified that MLC parameters were measured under the same conditions at more than half of the facilities. Most institutions customized parameters in a similar manner for IMRT/VMAT. The median measured and customized values obtained in our study will be valuable to verify MLC installation accuracy and to shorten the iterative processes of finding the optimal values.

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Modelagem dos Fatores de Transmissão e DLG para um TrueBeam STX

Revista Brasileira de Física Médica ◽

10.29384/rbfm.2017.v11.n2.p7-10 ◽

2017 ◽

Vol 11 (2) ◽

pp. 7

Author(s):

Lais Bueno da Silva ◽

Guilherme Alexandre Pavan ◽

André Vinícius Camargo ◽

Diego Cunha Silveira Alves da Silva ◽

Letícia Medeiros Santoni

Keyword(s):

Radiation Therapy ◽

Volumetric Modulated Arc Therapy ◽

Intensity Modulated Radiation Therapy ◽

Intensity Modulated ◽

Portal Dosimetry ◽

Multi Leaf Collimator ◽

Arc Therapy ◽

Dosimetric Leaf Gap

Para Multi Leaf Collimator (MLC) de ponta arredondada, o sistema de planejamento Eclipse (Varian) exige a medida do Fator de transmissão (FT) e Dosimetric Leaf Gap (DLG) para Intensity Modulated Radiation Therapy (IMRT) e Volumetric Modulated Arc Therapy (VMAT). O uso desses fatores obtidos pela metodologia proposta pela Varian, pode não garantir a melhor concordância em controles de qualidade (CQ) de pacientes, enquanto a modelagem dos mesmos possibilita obter um valor “ótimo” reduzindo as diferenças entre doses medida/calculada. O objetivo desse trabalho foi medir o FT e DLG de um acelerador TrueBeam (TB) com diferentes setups e detectores, modelar esses parâmetros e validar os resultados aplicando a metodologia da AAPM-TG119 utilizando o sistema Portal Dosimetry (PD). Para obtenção do FT e DLG (6MV, 6FFF, 10MV e 10FFF), utilizaram-se planos DICOM fornecidos pelo fabricante e câmara de ionização Farmer e CC13 em diferentes setups. Para a modelagem, inicialmente utilizou-se a dose medida com a câmara Farmer em planejamentos de VMAT de próstata e cabeça e pescoço. A partir dos dados obtidos, interativamente os valores do FT e DLG foram alterados buscando maior índice de aceite (>95%) no critério gama 1%1mm usando o PD. Finalmente, todos os planejamentos do TG119 com IMRT e VMAT foram medidos usando PD. Os valores finais medidos/modelados foram: 6X[(FT=1.1%/1.0%)(DLG=0.044cm/0,12cm)], 10X[(FT=1.3%/1,3%) (DLG=0.055cm/0,13cm)], 6FFF[(FT=0.93%/0,4%)(DLG=0.036cm/0,05cm)], 10FFF[(FT=1,14%/1,05%) (DLG=0.048cm/0,05cm)]. A média das porcentagens de aceite para o critério gamma 1%1mm dos planejamentos do TG119 com VMAT/IMRT após a modelagem foram 6X: 96%/76%; 10X: 98%/95%; 6FFF: 97%/87%; 10FFF: 97%/82%. A modelagem do FT e DLG é útil para melhorar a acurácia dos controles de qualidade dos pacientes, porém, o detector de escolha e a técnica usada (VMAT ou IMRT) são determinantes e levam a diferentes resultados. Um equilíbrio deve ser encontrado de acordo com a rotina do departamento.

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Copper-dependent ATP7B up-regulation drives the resistance of TMEM16A-overexpressing head-and-neck cancer models to platinum toxicity

Biochemical Journal ◽

10.1042/bcj20190591 ◽

2019 ◽

Vol 476 (24) ◽

pp. 3705-3719 ◽

Cited By ~ 2

Author(s):

Avani Vyas ◽

Umamaheswar Duvvuri ◽

Kirill Kiselyov

Keyword(s):

Oxidative Stress ◽

Head And Neck ◽

Transcriptional Activation ◽

Platinum Resistance ◽

Mrna Levels ◽

Strong Positive Correlation ◽

Platinum Compounds ◽

Copper Chelation ◽

Novel Approach ◽

Cancer Models

Platinum-containing drugs such as cisplatin and carboplatin are routinely used for the treatment of many solid tumors including squamous cell carcinoma of the head and neck (SCCHN). However, SCCHN resistance to platinum compounds is well documented. The resistance to platinum has been linked to the activity of divalent transporter ATP7B, which pumps platinum from the cytoplasm into lysosomes, decreasing its concentration in the cytoplasm. Several cancer models show increased expression of ATP7B; however, the reason for such an increase is not known. Here we show a strong positive correlation between mRNA levels of TMEM16A and ATP7B in human SCCHN tumors. TMEM16A overexpression and depletion in SCCHN cell lines caused parallel changes in the ATP7B mRNA levels. The ATP7B increase in TMEM16A-overexpressing cells was reversed by suppression of NADPH oxidase 2 (NOX2), by the antioxidant N-Acetyl-Cysteine (NAC) and by copper chelation using cuprizone and bathocuproine sulphonate (BCS). Pretreatment with either chelator significantly increased cisplatin's sensitivity, particularly in the context of TMEM16A overexpression. We propose that increased oxidative stress in TMEM16A-overexpressing cells liberates the chelated copper in the cytoplasm, leading to the transcriptional activation of ATP7B expression. This, in turn, decreases the efficacy of platinum compounds by promoting their vesicular sequestration. We think that such a new explanation of the mechanism of SCCHN tumors’ platinum resistance identifies novel approach to treating these tumors.

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Collecting Words: A Clinical Example of a Morphology-Focused Orthographic Intervention

Language Speech and Hearing Services in Schools ◽

10.1044/2020_lshss-19-00050 ◽

2020 ◽

Vol 51 (3) ◽

pp. 544-560 ◽

Cited By ~ 3

Author(s):

Kimberly A. Murphy ◽

Emily A. Diehm

Keyword(s):

Written Language ◽

Morphological Knowledge ◽

English Orthography ◽

Word Level ◽

Novel Approach ◽

Language Pathology ◽

The One ◽

Critical Intervention ◽

Reading And Spelling ◽

Reading And Spelling Difficulties

Purpose Morphological interventions promote gains in morphological knowledge and in other oral and written language skills (e.g., phonological awareness, vocabulary, reading, and spelling), yet we have a limited understanding of critical intervention features. In this clinical focus article, we describe a relatively novel approach to teaching morphology that considers its role as the key organizing principle of English orthography. We also present a clinical example of such an intervention delivered during a summer camp at a university speech and hearing clinic. Method Graduate speech-language pathology students provided a 6-week morphology-focused orthographic intervention to children in first through fourth grade ( n = 10) who demonstrated word-level reading and spelling difficulties. The intervention focused children's attention on morphological families, teaching how morphology is interrelated with phonology and etymology in English orthography. Results Comparing pre- and posttest scores, children demonstrated improvement in reading and/or spelling abilities, with the largest gains observed in spelling affixes within polymorphemic words. Children and their caregivers reacted positively to the intervention. Therefore, data from the camp offer preliminary support for teaching morphology within the context of written words, and the intervention appears to be a feasible approach for simultaneously increasing morphological knowledge, reading, and spelling. Conclusion Children with word-level reading and spelling difficulties may benefit from a morphology-focused orthographic intervention, such as the one described here. Research on the approach is warranted, and clinicians are encouraged to explore its possible effectiveness in their practice. Supplemental Material https://doi.org/10.23641/asha.12290687

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