Yu-Jen Chen1, Chih-Ming Liu2, Tzung-Jeng Huang2, Yun-Chin Hsu1, Yu-Chun Lo1, Hai-Gwo Hwu2, and Wen-Yih Isaac Tseng1,3
1National Taiwan University, Institute of Medical Device and Imaging, Taipei, Taiwan, 2National Taiwan University Hospital, Department of Psychiatry, Taipei, Taiwan, 3National Taiwan University, Molecular Imaging Center, Taipei, Taiwan
Synopsis
In
this study, we examined the performance of predicting patients with
schizophrenia based on the patterns of altered tract integrity over the whole
brain. The whole-brain tract information was compared with predefined
differences between schizophrenia patients and healthy participants to
calculate an index of SLI indicating the similarity to schizophrenia. Our
results showed that the prediction performance was high (AUC = 0.86 for males;
AUC = 0.77 for females) when we compared the white matter integrities at
specific segments on fiber pathways. Objectives
Biomarkers
have been sought after in the field of schizophrenia research for decades. Diffusion
magnetic resonance imaging (dMRI) has been widely used to investigate structural
differences between patients with schizophrenia and healthy participants.
However, there is no study showing the capability of individualized prediction
of the schizophrenia based on the differences in the tract integrity over the
whole brain. In this study, we used the tract-based automatic analysis (TBAA)
method [1] to obtain whole brain tract integrity for
individual subject. The information of integrities, named 2D connectogram, was tested
for predicting adult patients with schizophrenia. Subjects were separated into males and females to remove the
gender effect. We aim to investigate the capability of individualized
prediction of schizophrenia by using the information of whole brain fiber tracts.
Methods
One
hundred and eight schizophrenia patients (males: 54, females: 54) and 144 age-matched
healthy controls (males: 70, females: 74) were recruited in the analysis. Images were acquired on a 3T MRI system with a
32-channel head coil (Tim Trio, Siemens, Erlangen, Germany). Diffusion spectrum
imaging (DSI) was acquired for 102 diffusion encoding gradients with b
max = 4000 s/mm
2 (TR/TE =
9600/130 ms, image matrix size = 80 x 80, spatial resolution = 2.5 x 2.5 mm
2,
and slice thickness = 2.5 mm). TBAA method
was applied to subjects to assess the whole-brain white matter properties. A 2D
connectogram comprising generalized fractional anisotropy (GFA) along
predefined 76 major tracts and 100 continuous steps for each tract was
estimated as standardized information for each subject. Subjects of
males/females were randomly separated into training group and predicting group
for 200 permutations. For each permutation, whole brain difference (WD) between
training patients and training controls was determined by comparing the 2D
connectogram between the two groups. Series of masks were determined to
represent the locations containing different effect size (ES) and cluster size
(CS) in WD (ES: 0, 0.05, 0.1,…, 1; CS: 1, 2, 3,…, 15). For predicting group, the
whole-brain tract information of each subject was assessed by performing TBAA
first. A schizo-like index (SLI) was then estimated for each subject by using
following steps. 1) Schizo-or-control maps (SOC) were estimated by comparing the
connectogram with WD. Steps with GFA values closer to schizophrenia than to
control were noted as schizo-liked, otherwise as control-liked. 2) Masked SOC
(mSOC) was derived by applying a mask to SOC. Steps passing the criteria of the
mask were reserved for mSOC. 3) SLI was defined
as the number of steps which were schizo-liked in the mSOC. The performance of
prediction was evaluated with receiver operating characteristic (ROC) curve
analysis by comparing the SLI scores and clinical diagnostic results. Masks
with different criteria of ES and CS were applied to evaluate what kind of
difference between schizophrenia patients and healthy participants over the
whole brain has the best capability in distinguishing the two groups.
Results
Figure
1 shows the maps of averaged area under ROC curves (AUC) of different masks
from 200 permutations of males. The highest AUC of 0.87 was found for
predicting males with the mask of ES ≥
0.75 and CS ≥ 1 step (Black grid). Figure 2 shows the maps
for female. The highest predicting performance (AUC = 0.77) was found with the
mask of ES > 0.1 and CS > 1 step (Black grid). Figure 3 shows the accumulated
masks of the masks with highest AUC from 200 permutations for males (3a) and
females (3b).
Discussion
In
this study, we examined the performance of predicting patients with
schizophrenia based on the patterns of altered tract integrity over the whole
brain. The whole-brain tract information was compared with predefined
differences between schizophrenia patients and healthy participants to
calculate an index of SLI indicating the similarity to schizophrenia. Our
results showed that the prediction performance was high (AUC = 0.86 for males;
AUC = 0.77 for females) when we compared the white matter integrities at
specific segments on fiber pathways. The segments for predicting male subjects
are located in several specific tract bundles with high ES as figure 3a showed
while the contrast of the colors may imply the importance level for prediction.
The fiber pathways for predicting female subjects are widespread over whole
brain (figure 3b) which implies that there is higher variability of the tract
impairment in female patients than in male patients.
Conclusions
The information
of the whole-brain tracts estimated by TBAA method is potentially useful for
predicting adult patients with schizophrenia. Our study warrants a prospective
study to validate the diagnostic accuracy of the method.
Acknowledgements
No acknowledgement found.References
Chen YJ, Lo YC, Hsu YC, Fan CC, Hwang TJ, Liu CM, Chien YL,
Hsieh MH, Liu CC, Hwu HG, Tseng WY. (2015): Automatic whole brain tract-based
analysis using predefined tracts in a diffusion spectrum imaging template and
an accurate registration strategy. Hum Brain Mapp 36(9):3441-58.