Jing-Ying Huang1, Yu-Jen Chen1, Chih-Min Liu2, Tzung-Jeng Hwang2,3, Yun-Chin Hsu1, Yu-Chun Lo1, Hai-Gwo Hwu2,3, and Wen-Yih Isaac Tseng1,3,4,5,6
1Institute of Medical Device and Imaging, National Taiwan University College of Medicine, Taipei, Taiwan, 2Department of Psychiatry, National Taiwan University Hospital, Taipei, Taiwan, 3Graduate Institute of Brain and Mind Sciences, National Taiwan University College of Medicine, Taipei, Taiwan, 4Institute of Biomedical Engineering, National Taiwan University, Taipei, Taiwan, 5Department of Medical Imaging, National Taiwan University Hospital, Taipei, Taiwan, 6Molecular Imaging Center, National Taiwan University, Taipei, Taiwan
Synopsis
This study aims to identify image biomarkers for
schizophrenia patients in order to predict treatment responses on individual
subject basis. We develop
algorithm that can discriminate remission or non-remission in patients with schizophrenia based on the
difference in microstructural integrity of the white matter tracts. The ROC
analysis shows that the accuracy of the prediction is 76%.Introduction
Patients with schizophrenia require lifelong
treatment even when symptoms have improved.
Unfortunately, antipsychotic drugs aren't equally effective for every patient;
it's unknown who might or might not benefit from the treatment
1. Previous
studies have found abnormal white matter tracts connecting frontal and temporal
structures which were predictive of the short-term outcome of psychosis
2.
However few have tried to identify the image biomarkers based on the alteration
patterns of the whole brain fiber tracts. Therefore, the purpose of this study
is to identify the image biomarkers for
schizophrenia patients in order to predict treatment responses on individual
subject basis.
Method
Ninety-nine patients
with schizophrenia were recruited in this study (male/female = 47/52, age = 33.33 ± 9.02). Patients were
divided into two groups (remission and non-remission) accordingly to
the Positive and Negative Syndrome Scale (PANSS) scores. Diffusion spectrum imaging (DSI) and
T1-weighted MRI images were acquired on a 3T MRI system (TIM Trio, Siemens, Germany).
T1‐weighted imaging used a MPRAGE sequence (TR/TE = 2000/3 ms, flip angle = 9°, acquisition matrix = 192 × 256, FOV = 256 × 256 mm^2,
resolution = 1 x 1 x 1 mm^3). DSI used a pulsed gradient twice‐refocused
spin‐echo diffusion echo‐planar imaging sequence (TR/TE = 9600/130 ms, FOV = 200 × 200 mm^2, matrix size = 80 × 80, slice thickness = 2.5 mm)
3.
A total of 102 diffusion-encoding gradients were applied with the maximum diffusion
sensitivity b
max of 4000 s/mm^2. The diffusion-encoding gradients
corresponded to the grid points in the diffusion-encoding space (q space)
filled in a half sphere
4. We used the
tract-based automatic analysis (TBAA) to analyze the tract integrity of 76
major fiber tract bundles in the brain
5. The output of the TBAA analysis was a 2D
connectogram for each DSI dataset, presenting GFA profiles of the 76 tract
bundles. To identify the image biomarkers, patients were divided randomly into two groups, a training group and a testing group, with
comparable number of remitted and non-remitted patients. The training group was
used to compare the difference between remitted and non-remitted patients and
to generate treatment response-relevant masks at different thresholds. We used 15 levels of cluster size and 20 levels of effect
size as our combined thresholds, resulting in 300 masks. The
testing group was used to verify the performance of the prediction for each of
the masks using the receiver
operating characteristic (ROC) analysis.
Specifically, each individual patient’s GFA value was compared to the mean
values of the remitted and non-remitted patients at the same step of the
connectogram in the training group. If patient’s GFA value was close to
remission, the step was set to 0, while it was set to 1 means close to
non-remission. Accordingly, we obtained a remission-or-non-remission (RON) map
for each subject. The RON map was then masked by the masks obtained from the
training group, producing 300 masked RON maps. We devised a scoring system of
likelihood of non-remission by counting the total number of non-zero steps in
the masked RON map. The number of count was defined as the non-remission index
(NRI). Consequently, we obtained the NRI for each of the masks in each subject.
Once each subject had the NRI for each mask, we performed the ROC analysis to
test the performance of the mask by comparing the NRI and the subject’s final
diagnosis (remission or non-remission). We used the area-under-curve (AUC)
value to indicate the accuracy of the prediction and repeated the test for200
permutation. The endpoint of the study was to identify the mask that best predicted
the non-remission and its accuracy of the prediction.
Result
We found that some
masks exhibited high AUC values in predicting remission and non-remission. The masks with the
cluster size of 14 to 15 and the effect size of
0.15 ± 0.10 showed the best prediction (Figure 1). By cumulating the
best-performance masks over
200 permutations, we obtained the heat map of the segments that contributed
significantly to the prediction (Figure 2). These segments were considered as the
potential biomarkers of the treatment response in schizophrenia. The mean AUC
value of the best-performance masks over 200 permutations was approximately
76%. This meant that using our prediction algorithm on individual subject basis,
the accuracy of predicting the treatment
response was around 76%.
Discussion
The algorithm based
on the alteration patterns of the whole-brain fiber tracts reveals satisfactory
AUC values in predicting the treatment response of schizophrenia (76% accuracy)
on individual subject basis.
Conclusions
Future work will
involve an independent longitudinal study to validate the clinical value of
these biomarkers.
Acknowledgements
No acknowledgement found.References
1. Dazzan, Paola. Neuroimaging biomarkers to
predict treatment response in schizophrenia: the end of 30 years of
solitude? Dialogues Clin Neurosci. 2014;16(4):491-503.
2. Luck,
D. et al. Fronto-temporal disconnectivity and clinical short-term
outcome in first episode psychosis: a DTI-tractography study. J Psychiatr Res. 2011;45(3):369-77.
3. Reese, T. G. et al. Reduction of eddy-current-induced distortion in diffusion MRI
using a twice-refocused
spin
echo. Magn Reson Med. 2003;49(1):177-82.
4. Kuo, L. W. et al. Optimization of diffusion spectrum imaging and q-ball imaging
on clinical MRI system. Neuroimage. 2008;41(1):7-18.
5. Chen, Y. J. et al. Automatic
whole brain tract-based
analysis using predefined tracts in a diffusion spectrum imaging template and
an accurate registration strategy. Hum Brain Mapp. 2015;36(9):3441-58.