High precision Proton Therapy Dosimetry
MLIC*
The Multi Layer Ion Chamber (MLIC) is designed to assure fast measurement of depth dose distribution in particle.
The device consists of a stack of 180 plane parallel chambers. Its unique design combines fast and accurate acquisition with an excellent spatial resolution (of the order of 2 mm Water Equivalent). The complete depth dose profile can be measured in the whole clinical range up to 33 cm Water Equivalent.
The MLIC allows the measurement and the analysis of both pristine peaks and Spread-Out Bragg Peaks (SOBP) for both passive and scanning delivery techniques.
Uniform Scanning
The MLIC offers a revolutionary technique allowing the measurement of the complete field delivery in one shot compared to cumbersome measurement technique with a water phantom or similar. The MLIC data are represented by green circle points (data with PPC05 are symbolized by triangle orange points).
Indeed, when using a water phantom, SOBP is considerably long as the measurement of each single point lasts as much as the complete field delivery. By using the MLIC, the time needed is significantly reduced as it corresponds to one single field delivery for the full range of 180 measurement points. Furthermore, the temporal composition of the delivery can be extracted thanks to the fast full parallel readout down to 10 ms per sample. In consequence, the individual Bragg Peaks can be displayed with their relative weight contributions.
Double Scattering
The figure shows a comparison between MLIC and water phantom for the measurement of a complete delivery in passive scattering. The beam parameters like the flatness, modulation, range, distal fall-off are extracted for both device and merged in the following table.
Peaks measured in double scattering delivery technique for different proton ranges are visualized in this figure. The 2 mm spacing is defined by the native resolution of the detector (green points). The orange line is defined as the data measured in water phantom.
The determination of the range is found to agree better than 0.5 mm with respect to water phantom measurement.
Functionalities:
- fast and efficient set-up
- verification of the single as well as of the modulated peak in only one measurement
- unique detector layout
- parallel plates air vented ionization chamber
- 2 mm detector spacing along the beam axis
- temporal resolution down to 10 ms integration time and full parallel readout without dead time based on TERA06 technology
- device is set up on the couch and easily aligned with reference marks by means of the treatment room lasers. An attachment to robot positioning device is also possible.
* working title
This design was supported by Bernard Gottschalk thanks to his precious advices and recommendations.
