A multicontrast approach for comprehensive imaging of substantia nigra.
We characterize the contrast behavior of substantia nigra (SN) in both magnetization transfer (MT) imaging, which is believed to be sensitive to neuromelanin (NM), and susceptibility weighted imaging (SWI). Images were acquired with a MT prepared dual echo gradient echo sequence. The first echo was taken as the MT contrast image and the second was used to generate the SWI image. SN volumes were segmented from these two types of images using a thresholding method. The spatial and signal characteristics of the extracted SWI and MT volumes were compared. Both images showed the presence of SN but the volumes of the SN identified in the two are spatially incongruent. The MT volume was more caudal than the SWI volume and with only a 12% overlap between the two volumes. Considering the SN volumes in each hemisphere separately, the average distances between the centers of mass of the volumes from the two types images are 5.1±1.1mm and 4.1±1.2mm, respectively. The frequency offsets (homodyne filtered phase/echo time) for the volumes derived from MT (NM) images and SWI images are 0.09±0.32radians/s and -1.12±0.57radians/s (p<0.0001), respectively. The MT contrasts for the two volumes are 0.16±0.02 and 0.10±0.03 (p<0.001), respectively. Our results indicate that the two contrasts are sensitive to different portions of the SN, with MT seeing the more caudal portion of the SN than SWI, likely due to variations of NM and iron content in the SN. Despite the small overlap, these regions are complementary. Our results provide a new understanding of the contrast behavior of the SN in the two imaging approaches commonly used to image it and indicate that using both may yield a more comprehensive visualization of the SN.
Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, United States.
Jason
J
Langley
Department of Neurology, Emory University, Atlanta, GA, United States; Center for Health Research Southeast, Kaiser Permanente, Atlanta, GA, United States.
Daniel E
DE
Huddleston
Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, United States.
Xiangchuan
X
Chen
Department of Neuroradiology, University Medical Center Hamburg-Eppendorf (UKE), Hamburg, Germany.
Jan
J
Sedlacik
Department of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, GA, United States.
Nishant
N
Zachariah
Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, United States. Electronic address: xhu3@emory.edu.
Xiaoping
X
Hu
D000328:Adult; D000465:Algorithms; D015415:Biomarkers; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008543:Melanins / Q000378:metabolism; D010300:Parkinson Disease / Q000175:diagnosis; D012012:Red Nucleus / Q000033:anatomy & histology / Q000378:metabolism; D013378:Substantia Nigra / Q000033:anatomy & histology* / Q000378:metabolism
D015415:Biomarkers; D008543:Melanins
Iron; Magnetization transfer; Neuromelanin; Substantia nigra; Susceptibility weighted imaging