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Tommy Knöös

Sjukhusfysiker

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Correction for Ion Recombination in a Built-in Monitor Chamber of a Clinical Linear Accelerator at Ultra-High Dose Rates

Författare

  • Elise Konradsson
  • Crister Ceberg
  • Michael Lempart
  • Börje Blad
  • Sven Bäck
  • Tommy Knöös
  • Kristoffer Petersson

Summary, in English

In the novel and promising radiotherapy technique known as FLASH, ultra-high dose-rate electron beams are used. As a step towards clinical trials, dosimetric advances will be required for accurate dose delivery of FLASH. The purpose of this study was to determine whether a built-in transmission chamber of a clinical linear accelerator can be used as a real-Time dosimeter to monitor the delivery of ultra-high-dose-rate electron beams. This was done by modeling the drop-in ion-collection efficiency of the chamber with increasing dose-per-pulse values, so that the ion recombination effect could be considered. The raw transmission chamber signal was extracted from the linear accelerator and its response was measured using radiochromic film at different dose rates/dose-per-pulse values, at a source-To-surface distance of 100 cm. An increase of the polarizing voltage, applied over the transmission chamber, by a factor of 2 and 3, improved the ion-collection efficiency, with corresponding increased efficiency at the highest dose-per-pulse values by a factor 1.4 and 2.2, respectively. The drop-in ion-collection efficiency with increasing dose-per-pulse was accurately modeled using a logistic function fitted to the transmission chamber data. The performance of the model was compared to that of the general theoretical Boag models of ion recombination in ionization chambers. The logistic model was subsequently used to correct for ion recombination at dose rates ranging from conventional to ultra-high, making the transmission chamber useful as a real-Time monitor for the dose delivery of FLASH electron beams in a clinical setup.

Avdelning/ar

  • Radiotherapy Physics
  • Medicinsk strålningsfysik, Lund
  • LUCC: Lunds universitets cancercentrum

Publiceringsår

2020

Språk

Engelska

Sidor

580-586

Publikation/Tidskrift/Serie

Radiation Research

Volym

194

Issue

6

Dokumenttyp

Artikel i tidskrift

Förlag

Radiation Research Society

Ämne

  • Radiology, Nuclear Medicine and Medical Imaging
  • Other Physics Topics

Status

Published

Forskningsgrupp

  • Radiotherapy Physics

ISBN/ISSN/Övrigt

  • ISSN: 0033-7587