# Ultrafast FLASH radiation therapy dosimetry

> **NIH NIH R21** · UNIVERSITY OF KANSAS MEDICAL CENTER · 2024 · $172,098

## Abstract

PROJECT SUMMARY
Ultrafast FLASH radiation therapy dosimetry is an unsolved clinical and engineering problem. The goal of this
research is to develop a first-of-its-kind pulse-resolved ultrafast radiation detector prototype based on
innovative low-gain-avalanche-detector (LGAD) technology and ultrafast electronics for FLASH radiation
therapy dosimetry. Our recent work published in Physics in Medicine and Biology demonstrates that, for the
first time, LGAD sensors with associated ultrafast readout electronics (International patent number
WO2019232172A1) developed at the University of Kansas (KU) can measure charged particle fluences with
high speed and spatial precision. The system has been tested with a medical LINAC where single particles
were measured with a time resolution of 50 picoseconds. The integrated response is as accurate as a standard
ionization chamber but with a spatial resolution twenty times finer and a temporal resolution over 100 million
times better with the capability to measure the charges deposited by a single LINAC pulse. The unprecedented
resolving power allows the structure of the commonly known 3-microsecod LINAC pulses to be viewed and,
most strikingly, the 350-picosecond sub-pulses in the train to be reconstructed. This project is in response to
PAR-19-150 which seeks to encourage quantitative and physical scientists to work with biomedical
researchers to catalyze the use of bioengineering approaches for their potential to open new areas of
biomedical investigation. We aim to 1) design and build a LGAD dosimetry prototype, both a single-element
and a 16-element array with a 1-cm pitch, and 2) determine if the prototypes can function as an ultrafast and
proportional dose measurement device. This proof-of-concept study provides an innovative method for FLASH
dosimetry that has the potential to expand dose measurement capability from milliseconds to microseconds
and even to nanoseconds. The ultrafast detectors can be used by the radiation biologists for accurate dose
estimations in preclinical animal studies, by FLASH system vendors to allow their use in a safety feedback
system that could stop a beam during treatment, and by the clinical medical physicists to function as a two-
dimensional detector array for both FLASH delivery commissioning and patient-specific quality assurance and
quality control.

## Key facts

- **NIH application ID:** 10840959
- **Project number:** 5R21CA274193-02
- **Recipient organization:** UNIVERSITY OF KANSAS MEDICAL CENTER
- **Principal Investigator:** Harold Hui Li
- **Activity code:** R21 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $172,098
- **Award type:** 5
- **Project period:** 2023-07-01 → 2025-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10840959

## Citation

> US National Institutes of Health, RePORTER application 10840959, Ultrafast FLASH radiation therapy dosimetry (5R21CA274193-02). Retrieved via AI Analytics 2026-05-25 from https://api.ai-analytics.org/grant/nih/10840959. Licensed CC0.

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