title: Quantitative T1, T2, and T2* Mapping and Semi-Quantitative Neuromelanin-Sensitive Magnetic Resonance Imaging of the Human Midbrain.
abstract: OBJECTIVE
  Neuromelanin is a dark pigment granule present within certain catecholamine neurons of the human brain. Here, we aimed to clarify the relationship between contrast of neuromelanin-sensitive magnetic resonance imaging (MRI) and MR relaxation times using T1, T2, and T2* mapping of the lower midbrain.
  
  
  METHODS
  The subjects were 14 healthy volunteers (11 men and 3 women, mean age 29.9 ± 6.9 years). Neuromelanin-sensitive MRI was acquired using an optimized T1-weighted two-dimensional (2D)-turbo spin-echo sequence. To quantitatively evaluate the relaxation time, 2D-image data for the T1, T2, and T2* maps were also acquired. The regions of interest (substantia nigra pars compacta [SNc], superior cerebellar peduncles [SCP], cerebral peduncles [CP], and midbrain tegmentum [MT]) were manually drawn on neuromelanin-sensitive MRI to measure the contrast ratio (CR) and on relaxation maps to measure the relaxation times.
  
  
  RESULTS
  The CR in the SNc was significantly higher than the CRs in the SCP and CP. Compared to the SCP and CP, the SNc had significantly higher T1 relaxation times. Moreover, the SNc had significantly lower T2 and T2* relaxation times than the other three regions (SCP, CP, and MT). Correlation analyses showed no significant correlations between the CRs in the SNc, SCP, and CP and each relaxation time.
  
  
  CONCLUSIONS
  We demonstrated the relationship between the CR of neuromelanin-sensitive MRI and the relaxation times of quantitative maps of the human midbrain.
authors: Division of Radiology, Department of Medical Technology, Osaka University Hospital, Suita, Osaka, Japan.
authors: Takashi
authors: T
authors: Hashido
authors: Department of Medical Engineering, Division of Health Sciences, Osaka University, Graduate School of Medicine, Suita, Osaka, Japan.
authors: Shigeyoshi
authors: S
authors: Saito
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008543:Melanins / Q000378:metabolism*; D008636:Mesencephalon / Q000000981:diagnostic imaging* / Q000378:metabolism; D055815:Young Adult
chemical_list: D008543:Melanins; C014121:neuromelanin