Electronic Resource
Transit dosimetry based on water equivalent path length measured with an amorphous silicon electronic portal imaging device
| العنوان: | Transit dosimetry based on water equivalent path length measured with an amorphous silicon electronic portal imaging device |
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| المؤلفون: | Kavuma, Awusi |
| نوع الوثيقة: | Electronic Resource |
| مستخلص: | Background and purpose: In vivo dosimetry is one of the quality assurance tools used in radiotherapy to monitor the dose delivered to the patient. The digital image format makes electronic portal imaging devices (EPIDs) good candidates for in vivo dosimetry. Currently there is no commercial transit dosimetry module, which could facilitate routine in vivo dosimetry with the EPID. Some centres are developing their in-house packages, and they are under assessment before introduction into routine clinical usage. The main purpose of this work was to develop the EPID as an in vivo dosimetry device. Materials and methods: Knowledge of a detector’s dose-response behaviour is a prerequisite for any clinical dosimetric application, hence in the first phase of the study, the dosimetric characteristics of eleven Varian a-Si500 EPIDs that are in clinical use in our centre were investigated. The devices have been in use for varying periods and interfaced with two different acquisition control software packages, IAS2 / IDU-II or IAS3 / IDU-20. Properties investigated include: linearity, reproducibility, signal uniformity, field size and dose-rate dependence, memory effects and image profiles as a function of dose. In the second phase, an EPID was calibrated using the quadratic method to yield values for the entrance and exit doses at the phantom or patient. EPID images for a set of solid water phantoms of varying thicknesses were acquired and the data fitted onto a quadratic equation, which relates the reduction in photon beam intensity to the attenuation coefficient and material thickness at a reference condition. The quadratic model was used to convert the measured grey scale value into water equivalent path length (EPL) at each pixel for any material imaged by the detector. For any other non-reference conditions, scatter, field size and MU variation effects on the image were corrected. The 2D EPL is linked to the percentage exit-dose for different thicknesses and fiel |
| مصطلحات الفهرس: | QC Physics, RZ Other systems of medicine, Thesis, NonPeerReviewed |
| URL: | |
| الاتاحة: | Open access content. Open access content |
| ملاحظة: | application/pdf English |
| Other Numbers: | QCL oai:theses.gla.ac.uk:2580 https://theses.gla.ac.uk/2580/1/2011kavumaphD.pdf Kavuma, Awusi (2011) Transit dosimetry based on water equivalent path length measured with an amorphous silicon electronic portal imaging device. PhD thesis, University of Glasgow. 1140935093 |
| المصدر المساهم: | UNIV OF GLASGOW LIBR From OAIster®, provided by the OCLC Cooperative. |
| رقم الانضمام: | edsoai.on1140935093 |
| قاعدة البيانات: | OAIster |
| الوصف غير متاح. |