Influence of signal intensity non-uniformity on brain volumetry using an atlas-based method.
OBJECTIVE
Many studies have reported pre-processing effects for brain volumetry; however, no study has investigated whether non-parametric non-uniform intensity normalization (N3) correction processing results in reduced system dependency when using an atlas-based method. To address this shortcoming, the present study assessed whether N3 correction processing provides reduced system dependency in atlas-based volumetry.


METHODS
Contiguous sagittal T1-weighted images of the brain were obtained from 21 healthy participants, by using five magnetic resonance protocols. After image preprocessing using the Statistical Parametric Mapping 5 software, we measured the structural volume of the segmented images with the WFU-PickAtlas software. We applied six different bias-correction levels (Regularization 10, Regularization 0.0001, Regularization 0, Regularization 10 with N3, Regularization 0.0001 with N3, and Regularization 0 with N3) to each set of images. The structural volume change ratio (%) was defined as the change ratio (%) = (100 × [measured volume - mean volume of five magnetic resonance protocols] / mean volume of five magnetic resonance protocols) for each bias-correction level.


RESULTS
A low change ratio was synonymous with lower system dependency. The results showed that the images with the N3 correction had a lower change ratio compared with those without the N3 correction.


CONCLUSIONS
The present study is the first atlas-based volumetry study to show that the precision of atlas-based volumetry improves when using N3-corrected images. Therefore, correction for signal intensity non-uniformity is strongly advised for multi-scanner or multi-site imaging trials.
Department of Radiological Technology, University of Tokyo Hospital, Tokyo 113-8655, Japan. car6_pa2_rw@yahoo.co.jp
Masami
M
Goto
Osamu
O
Abe
Tosiaki
T
Miyati
Hiroyuki
H
Kabasawa
Hidemasa
H
Takao
Naoto
N
Hayashi
Tomomi
T
Kurosu
Takeshi
T
Iwatsubo
Fumio
F
Yamashita
Hiroshi
H
Matsuda
Harushi
H
Mori
Akira
A
Kunimatsu
Shigeki
S
Aoki
Kenji
K
Ino
Keiichi
K
Yano
Kuni
K
Ohtomo
D000328:Adult; D001271:Atlases as Topic; D001931:Brain Mapping / Q000379:methods*; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D012984:Software; D018709:Statistics, Nonparametric