Quick overview

FLASH–DOSE: Dosimetry for FLASH radiotherapy

Aim: To develop traceable dosimetry to support the development of reference dosimetry Codes of Practice (CoP) required by UHDPP electron and UHDR proton beam facilities aimed for FLASH radiotherapy.

Need

The FLASH effect

Radiotherapy: > 1 M cancer patients treated annuallyin EU 27
Conventional radiotherapy: delivers dose to patients with dose-rate of 0.1 Gy/s
FLASH radiotherapy: is able to strongly reduce side effects in radiotherapy.
The FLASH effect: increased sparing of healthy tissue for dose delivery with ultra-high dose rates (UHDR, > 40 Gy/s) or ultra high-dose-per-pulse (UHDPP, > 0.6 Gy/ pulse)

A comparison of skin conditions: on the left, a necrotic lesion labeled with dosage information at 0.1 Gy/s, and on the right, normal skin appearance at 300 Gy/s. Below, a graph illustrates tumor control and complication probabilities against radiation dosages.

Recombination correction, ks

Graph showing the relationship between measurement current and dose rate (Gy/s), with highlighted regions for Ultra-high dose-rate (UHDR) and Ultra-high dose-per-pulse (UHDPP). Includes labels for calibration and a secondary standard ionisation chamber.

Codes of Practice for reference dosimetry

Codes of Practice (CoPs): used to determine
absorbed dose Dw, under reference conditions in radiotherapy beams (e.g. TRS-398)
Clinical introduction of FLASH radiotherapy requires:
Codes of Practice for reference dosimetry in clinical:
– UHDPP electron beams with dose-per-pulse (DPP) > 0.6 Gy and electron energies 4 – 20 MeV
– UHDR scanning proton beams with dose-rates > 40 Gy/s and proton energies < 250 MeV

A technical report cover on absorbed dose determination in external beam radiotherapy by IAEA, shown alongside images of calibration and clinical beams.

Scientific excellence

WP1 Portable primary standard for scanning UHDR proton beams

Output:
– Extend the operational range of porta- ble water and graphite calorimeters to determine DW under UHDR conditions
in scanning proton beams.
– First comparison of primary standards in scanning UHDR proton beams

An illustration of a cylindrical device with a marked component labeled 'A' on top, alongside a 3D model showing internal profiles and measurements related to the device's function.

WP2 Reference dosimetry in scanning UHDR proton beams

Output:
• Methodology for reference dosimetry in scanning UHDR proton beams with target uncertainty of 1.7%
• Methodology for measuring spatial and temporal beam structure
• Measured and simulated kq data for novel secondary standards compared
• Measured ks data
• Validated reference conditions

Graph depicting instant dose rate over time, with peaks in red and cyan, along with a spatial grid showing colored markers.

WP3 Simulation of secondary standard correction factors (ks, kQ)

Output:
– Simulation models for increased understanding and quantification of recombination effects at UHDR and UHDPP conditions
– Uncertainty budget for ks

Illustration showing electric field lines between a negative electrode (top) and a positive electrode (bottom) with positively charged ions represented as blue dots and negatively charged ions as red dots.

WP4 Reference dosimetry in clinical UHDPP electron beams

Output:
– Clinical-like reference fields
– Methodology for reference dosimetry in UHDPP electron beams with target uncertainty of 1.2 %
– Measured k data for novel secondary
standards
– Measured ks data
– Validated reference conditions

A graph displaying chamber current in mA over time in microseconds, with a marked decline in current following a sharp peak, annotated with '100 ms (10 Hz)' and 'DPP [Gy] 5.75'.

Impact

Early impact

  • Accelerate development of Codes of Practice for reference dosimetry (AAPM TG-359)
  • Enabling widespread clinical implementation of FLASH facilities
  • Uptake of secondary standards characteristics in IEC 60731 “Medical electrical equipment – Dosimeters with ionization chambers as used in radiotherapy”
  • Calibration of secondary standards in clinical-like reference fields for UHDPP

Wider impact

  • European cancer patients benefit from reduced side effects and will have 
  • improved quality of life 
  • Enhanced cost effectiveness of radiotherapy 
  • Enhanced reliability in FLASH facilities (market > 1 B€) 
  • Enhanced reliability in new detectors and new measurement systems dedicated to and characterized for FLASH

Consortium

Stakeholders