Standard Imaging, the University of Texas MD Anderson Cancer Center, and the University of Wisconsin-Madison collaborated on a FLASH radiotherapy research project to develop a novel ionization chamber for reference dosimetry in ultra-high dose per pulse “FLASH” radiotherapy. This effort was supported in part by an NIH/NCI SBIR Phase I contract for Topic 434.
“Our recent collaboration to develop and test our Exradin A30 Parallel Plate Ion Chamber research project represents a significant leap forward in active dose measurements for ultra-high dose rate FLASH beams,” said Eric DeWerd, MBA, Standard Imaging President. “This exciting new chamber will help enable clinical translation of FLASH treatments, ensuring that such extremely fast dose deliveries are well characterized and understood. At Standard Imaging, we are thrilled to be at the forefront of these advancements, which will help transform patient care and outcomes globally.”
Research Parameters and Purpose
Ultra-high dose rate (UHDR) radiation therapy, often called “FLASH” radiotherapy, has generated much excitement in the radiotherapy community, with both research and preclinical trials indicating that extremely fast dose deliveries can decrease damage to normal tissues while still achieving the desired tumor control. One of the primary factors hindering both the interpretation of multi-modality and multi-institution results as well as clinical translation of these methods is the lack of an active measurement device for dose calibration. Ionization chambers are used for this purpose in clinical radiotherapy, but traditional chamber designs suffer from dose-per-pulse dependencies that require significant correction in UHDR beams. This collaborative study focused on optimizing the design and performance of a thin parallel plate ionization chamber specifically for high dose per pulse UHDR beams.
“Our goal was to make an ion chamber that could be calibrated in a standard radiation beam but still used for ultra-high dose per pulse beams,” explained Shannon Holmes, Ph.D., Standard Imaging medical physicist and product manager. “The existing methods used for FLASH beam calibration are passive detectors that have to be read out after the fact. The Exradin A30 on the other hand can provide an immediate readout in the method that physicists are accustomed to using in their normal clinical practice. Having a calibrated ion chamber that doesn’t require massive correction factors is a huge step forward for FLASH dosimetry.”
Multiple chambers designs were produced and tested to determine the optimal electrode size, electrode gap, and operating bias voltage. The team also performed electric field modeling to help guide the design and to improve performance in high dose-per-pulse beams.
The primary goal was to evaluate the potential of these chambers as reference class instruments for calibration purposes, ensuring precise and reliable measurements in advanced radiation therapies. These advancements could significantly enhance the accuracy and efficiency of dosimetry for FLASH beams, paving the way for clinical translation of these promising treatments.
Exradin A30 Parallel Plate Chamber
A thin parallel plate ionization chamber designed for reference dosimetry in UHDR applications, the Exradin A30 is expected to provide high precision measurements both for FLASH and Conventional Radiation Therapy.
- 0.3mm collecting electrode separation
- Better than 95% charge collection efficiency for doses up to 5 Gy/pulse
- Better than 90% charge collection efficiency at up to 9 Gy/pulse
A peer reviewed article describing this work has been accepted for publication in Medical Physics.