ESTRO 36 Abstract Book

925 / 1082

S909 ESTRO 36 2017
_______________________________________________________________________________________________
using PET-tracers such as 18F-FMISO. Moreover, parameters
derived from functional MRI have been correlated with
response to RT, such as ADC.
Our hypothesis is that multiparametric PET/MRI, i.e. a
combination of different parameters derived from PET and
functional MRI, allows a better prediction in terms of RT
response than single parameters do.
The aim of this study was to distinguish two different
HNSCC cell-lines grown as xenografts in mice, based on
voxel-wise image analysis of simultaneously acquired
FMISO-PET and ADC data.
Material and Methods
11 immunodeficient nude mice were injected into the hind
leg with tumor-cells of human HNSCC cell-lines FaDu (n=7)
or CAL-33 (n=4). Once a tumor reached its target size
(~300 mm³), simultaneous PET and MR imaging was
performed on a 7T-PET/MR scanner (Bruker) at two time
points: before (d0) and after two weeks (d14) of
fractionated irradiation (10x 2Gy). The protocol included
dynamic FMISO-PET (90min), anatomical T2- and diffusion-
weighted MRI.
An image of the FMISO uptake was reconstructed from the
last 5 min of the acquired PET data. An ADC map was
calculated from a set of 9 diffusion-weighted MR images
(b=0-800 s⁄mm²). On the anatomical MR image, tumor and
muscle were defined as regions of interest (ROIs). ROIs and
ADC map were then resampled to the PET image grid for
consistent image analysis on the voxel level. FMISO tumor-
to-muscle-ratios (TMRs) were determined at both time
points for ROI-based and voxel-by-voxel comparison with
ADC values.
Results
The median (d0/d14) TMRmean was 1.43/1.06 and
1.25/1.00, median ADCmean was 780/929 and 1095/1286
x10⁻⁶ mm²/s, median FMISO TMRmax was 2.55/1.57 and
1.80/1.52, median slope m of a regression line through
voxelbased FMISO TMR and ADC scatter data was -2.29/-
1.25 and 0.02/-0.26 x10⁻⁴ , median ADCmean of a
thresholded subregion of the tumor where FMISO TMR≥1.4
was 730 (d0) and 1145 (d0) x10 ⁻⁶ mm²/s for FaDu and CAL-
33 tumor ROIs, respectively.
Parameter values for all tumors are presented in Fig1; a
scatter plot of voxelbased FMISO TMR and ADC values for
one FaDu and one CAL-33 tumor at d0, in Fig2.
Out of five parameters, three had strong potential for
differentiation of the HNSCC cell-line, when measured at
d0: TMRmax, slope m of the regression line and ADCmean
of the FMISO positive region (TMR≥1.4).
Conclusion
Voxelbased analysis of FMISO-PET and ADC data proved to
have high potential for discrimination of tumor cell-lines
presenting different radiobiological properties. Three
parameters were found to be suitable to distinguish the
two cell-lines with well-known difference in
radiosensitivity before the start of RT.
Additional sets of imaged-derived parameters will be
investigated and further cell-lines be measured to identify
relations with radiosensitivity for the development of a
multiparametric prediction model for personalized RT in
HNSCC.
EP-1689 Gleason driven dose painting based on ADC
MR imaging
E. Grönlund1, S. Johansson2, T. Nyholm1, A. Ahnesjö1
1Uppsala University, Medical radiation sciences, Uppsala,
Sweden
2Uppsala University, Experimental and clinical oncology,
Uppsala, Sweden
Purpose or Objective
To investigate a Gleason driven dose painting approach for
high risk prostate cancer patients based on outcome for
conventional treatments, and using apparent diffusion
coefficient (ADC) MR images for dose prescription.
Material and Methods