933 / 1096
S917
ESTRO 36
_______________________________________________________________________________________________
Z
eff
presented a 84.0% sensitivity and 81.8% specificity for
a threshold of 8.96 in ROC curves.
Conclusion
DECT imaging gives information on tumour necrosis.
Quantitative parameters (ρ
I
and Z
eff
) showed better
sensibility and specificity compared to standard HU
imaging. Mean Z
eff
showed better correlation with necrosis
status, due to necrotic core absorbs less iodine contrast.
Our approach has some advantages. Whole tumour semi-
automatic contouring had excellent reproducibility. No
cases were excluded due to geometry or mediastinal
contact.
This method could be a solid approach to assess necrosis
condition. However, we have not studied relationship
with the actual location of necrosis, so it would not be
useful for dose-painting protocols at necrotic core.
EP-1681 [C11]Choline PET/MRI for Prostate Cancer:
Identify Imaging Characteristics Predicting Metastasis
J.R. Tseng
1
, L.Y. Yang
2
, H.Y. Chang
2
, T.C. Yen
1
1
Chang Gung Memorial Hospital at Linkou, Nuclear
Medicine and Molecular Imaging Center, Kwei-Shan-
Taoyuan City, Taiwan
2
Chang Gung Memorial Hospital at Linkou, Biostatistics
Unit- Clinical Trial Center of Chang Gung Memorial
Hospital, Kwei-Shan- Taoyuan City, Taiwan
Purpose or Objective
Intergraded PET/MRI is a powerful imaging modality for
prostate cancer (Pca) in several aspects, from cancer
detection, primary staging, to staging of recurrent Pca.
The goal of primary staging is to detect metastatic spread
from the main tumor. In high risk Pca patients (PSA >20
ng/ml, or Gleason score of 8–10, or clinical stage T3a),
intergraded PET/MRI imaging may have great potential to
change clinical management. In the current study, we
aimed to identify imaging characteristics of main tumor
which can significantly predict distant metastasis.
Material and Methods
This prospective clinical study was approved by the Ethics
Committee (approval 102-3271A and 103-4561C). Since
January 2015 to June 2016, total 30 Pca patients
committed high risk criteria were enrolled to conduct
whole body integrated [C11]Choline PET/MRI (biograph
mMR, Simens). The PET and MRI imaging was interpreted
independently by one clinically-experienced nuclear
medicine physician and radiologist. In the PET imaging
analysis, main tumors were segmented using PMOD 3.3
software package. The borders of volumes of interest were
set by manual adjustment to avoid physiological
[C11]Choline uptake in the urine or intestine. The tumor
boundaries were automatically contoured based on the
thresholds of SUV 2.65. The gray-level run length encoding
matrix (GLRLM) was used for assessing the regional texture
features. In the MRI imaging analysis, anatomic (T2-
weighted MRI) and functional (diffusion-weighted MRI)
imaging features were documented. Multivariate
classification and regression tree analysis was used to
determine the best combination of variables and the
related cutoffs to predict risk for distant metastasis.
Results
The mean age is 70.1±6.2 years, and the mean PSA level
is 91.6 ± 139.4 ng/ml. In these 30 patients, 26 (87%) are
categorized as clinical stage IV, 4 (13%) as stage III. Fifteen
(50%) patients have distant metastasis, including 7 (23%)
non-regional lymph nodes metastasis, 11 (36%) bone
metastasis, 1 (3%) visceral organ metastasis. The
individual clinical risk factors (PSA >20 ng/ml, or Gleason
score of 8–10, or clinical stage T3a) are not significantly
associated with distant metastasis (P-value is 0.493,
0.087, 0.109, respectively). In the multivariate forward
analysis, imaging characteristics of main tumor side wall
invasion by anatomical T2 MRI is the only significant risk
factor predicting distant metastasis (odds ratio 42.25,
confidence interval 5.1-346.5, P-value <0.001). The PET
regional tumor texture features can further divide
patients into with or without distant metastasis by using
high intensity long run emphasis value > -0.40 and low
intensity run emphasis value <0.26 (Figure 1). The
Sensitivity and specificity of the multivariate tree model
was 80% and 80%, respectively.
Conclusion
By providing excellent anatomical, functional, and
metabolic information, integrated PET/MR enhances the
staging of metastatic disease in high risk Pca. Imaging
characteristics including pelvic side wall invasion and
tumor metabolic heterogeneity may have crucial role in
patient management.
EP-1682 Comparison of SUV based on different ROIs and
VOIs definitions: a multi-center 4D phantom study
M. Lambrecht
1
, K. Ortega Marin
1
, M. La Fontaine
2
, J.J.
Sonke
2
, R. Boellaard
3
, M. Verheij
2
, C.W. Hurkmans
1
1
Catharina Ziekenhuis, Physics/Radiotherapy, Eindhoven,
The Netherlands
2
Netherlands cancer institute, Radiotherapy,
Amsterdam, The Netherlands
3
University medical center- university of Groningen,
Nuclear medicine, Groningen, The Netherlands
Purpose or Objective
In the context of the EORTC LungTech trial, a QA
procedure including a PET/CT credentialing has been
developed. This procedure will ultimately allow us to pool
data from 23 institutions with the overall goal of
investigating the impact of tumour motion on
quantification. As no standardised procedure exists under
respiratory conditions, we investigated the variability of
14 SUV metrics to assess their robustness over respiratory
noise.
Material and Methods
The customized CIRS-008A phantom was scanned at 13
institutions. This phantom consists of a 18 cm long body,
a rod attached to a motion actuator, and a sphere of
either 1.5 or 2.5cm diameters. Body, rods and spheres
were filled with homogeneous 18FDG solutions
representative of activity concentrations in mediastinum,
lung and tumour for a 70kg patient. Three respiratory
patterns with peak-to-peak amplitudes and periods of
15mm/3sec, 15mm/6sec and 25mm/4sec were tested.
Prior to scanning in respiratory condition, a 3D static
PET/CT was acquired as reference. During motion, images