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2D luminescence dosimetry techniques for the assessment of linear energy transfer (LET)

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In hadron therapy, including proton therapy (PT), there is increasing focus on the effect of the linear energy transfer (LET) distribution in treatment plans. Radiation of different LET differs in track structure which affects the type of damage and the capacity of cells to repair the damage as clusters of strand breaks are more concentrated in space and less likely to be repaired correctly. In radiotherapy the treatment is described in absorbed dose but a scaling factor is used for the difference in energy deposition patterns. The proton relative biological effectiveness (RBE) nowadays uses a generic RBE of 1.1. Nevertheless there is pre-clinical evidence that the LET increases at the distal edge of the beam. This property provides an opportunity for biological optimization based on LET as well as an improved protection of organs at risk.

Ionization quenching has been exploited to estimate the LET by comparing the response of two detectors having different quenching characteristics. In our group the use of differently quenching thermoluminescent detectors (TLDs) have showed the possibility to measure both the absorbed dose and LET (Parisi, PMB 2019). However, the use of 2 detector systems is associated to large uncertainties in the regions of steep gradients, such as the distal edge. Therefore, the use of a single detector type to assess LET and dose is more favorable.

Al2O3:C,Mg (Landauer Inc, Stillwater Crystal Growth Division, USA) can be measured using optically stimulated luminescence (OSL) and radiophotoluminescence (RPL) with different quenching properties. In SCK CEN we have several options to measure both OSL and RPL properties from Al2O3:C,Mg films. Point measurements are performed using a commercial system RISO (OSL), while RPL reader Apollo can be used to measure RPL in a point. Recently we have developed a 2D RPL acquisition system (Nascimento 2019), which will be extended to OSL readout. Moreover, a 3D robotic system is currently under construction. 2D/3D dose mapping will allow to assess dose and LET distributions which features great potentials for physical characterization of the PT radiation field.

Objective

  • Extend 2D acquisition system to allow OSL readout. Films will be irradiation with Co60 source for different absorbed doses and linearity of the dose response will be assessed and compared to the commercial RISO system.
  • Irradiations in Hadron therapy (HIMAC) will allow to characterize OSL and RPL quenching properties as function of LET and to create an LET calibration curve.
  • Irradiations in proton therapy fields will allow to assess LET which will be compared to other detectors measuring dose and LET (TLD combinations, TimePix).

The minimum diploma level of the candidate needs to be

  • Master of industrial sciences
  • Master of sciences in engineering
  • Master of sciences

The candidate needs to have a background in

  • Physics
  • Engineers

Estimated duration

at least 6 months

Expert group

Research in Dosimetric Applications

SCK CEN Mentor

De Saint-Hubert Marijke
mdsainth [at] sckcen.be
+32 (0)14 33 21 40

SCK CEN Co-mentor

de Freitas Nascimento Luana
ldfnasci [at] sckcen.be
+32 (0)14 33 28 11