ESTRO 36 Abstract Book

937 / 1096

S921 ESTRO 36
_______________________________________________________________________________________________
parameters of 18F-FDG PET/CT image in patients with
early stage non-small cell lung cancer (NSCLC) treated by
stereotactic body radiation therapy (SBRT).
Material and Methods
Thirty patients with early stage NSCLC (T1-2N0M0) were
retrospectively investigated. SBRT was delivered with
total dose of 40-48Gy in 4 fractions for peripheral regions
or 50-60Gy in 7-15 fractions for central regions or regions
nearby other organ at risk. All patients underwent 18F-
FDG PET/CT scan before treatment. Each tumor was
delineated using PET Edge (MIM Software Inc., Cleveland)
and texture parameters were calculated using open-
source code CGITA (Fang, ., 2014). From 18F-FDG
PET/CT image, three conventional parameters including
metabolic tumor volume (MTV), maximum standardized
uptake value (SUV) and total lesion glycolysis (TLG) and
four textural parameters including entropy and
dissimilarity derived from co-occurrence matrix and high-
intensity large-area emphasis and zone percentage
derived from size-zone matrix were analyzed.
Reproducibility was evaluated using two independent
delineation conducted by two observers using intraclass
correlation coefficients (ICC). The ability to predict local
control (LC) was tested for each parameter using Cox
proportional hazards model.
Results
Median follow-up period was 30.1 month and 8 (23%)
patients occurred local relapse. Between two observers,
six parameters besides zone percentage (ICC value 0.59)
showed ICC value ranged between 0.81 and 1.00. In
univariate analysis, there were significant correlations
between LC and tumor diameter>30mm (hazard ratio
7.21, p=0.02), MTV≥5.14cm3 (HR 9.38, p=0.01), TLG≥59.7
(HR 5.86, p=0.04), entropy≥-34.3 (HR 0.13, p=0.02),
dissimilarity≥2235 (HR 6.87, p=0.03) and treatment
biological equivalent dose≥100Gy (HR 0.02, p=0.04),
respectively. Maximum SUV≥10.4 was not a significant
predictor for LC (p=0.09).
Conclusion
Texture analysis based on gradient-based delineation
method has high reproducibility in most parameters.
Entropy and dissimilarity calculated from co-occurrence
matrix is potentially beneficial to predict LC with
reproducibility in patients with NSCLC treated by SBRT. To
establish utility of texture analysis in 18F-FDG PET/CT
image, further study including prospective trial will be
needed.
EP-1688 Voxelbased analysis of FMISO-PET and
diffusion-weighted MRI of two different HNSCC models
in mice
R. Winter1, S. Boeke2, M. Krueger 3, A. Menegakis2, E.
Sezgin2, L. Wack1, G. Reischl3, B. Pichler 3, D. Zips2, D.
Thorwarth1
1University Hospital Tübingen, Section for Biomedical
Physics, Tübingen, Germany
2University Hospital Tübingen, Radiation Oncology,
Tübingen, Germany
3Werner Siemens Imaging Center, Preclinical Imaging and
Radiopharmacy, Tübingen, Germany
Purpose or Objective
Hypoxia is an important prognostic marker for
radiotherapy (RT) response, particularly for head and neck
squamous cell carcinoma (HNSCC) and may be measured
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