Quantitative T1, T2, and T2* Mapping and Semi-Quantitative Neuromelanin-Sensitive Magnetic Resonance Imaging of the Human Midbrain

Hashido, Takashi; Saito, Shigeyoshi

doi:10.1371/journal.pone.0165160

Cited by 13 publications

(9 citation statements)

References 58 publications

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“…The TE, TR and flip angles typically used in both the TSE and 3D-SPGR based NM-MRI are consistent with T1-weighted imaging [64]. With the T1 of the SNc being intermediate between those of WM (higher T1) and GM (lower T1) however, as reported in [18, 65] T1 values alone cannot account for the contrast seen in NM-MRI images. Thus a further contrast mechanism must be involved.…”

Section: Discussionsupporting

confidence: 60%

Pool size ratio of the substantia nigra in Parkinson’s disease derived from two different quantitative magnetization transfer approaches

et al. 2017

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Purpose We sought to measure quantitative magnetization transfer (qMT) properties of the substantia nigra pars compacta (SNc) in patients with Parkinson’s disease (PD) and healthy controls (HCs) using a full qMT analysis and determine whether a rapid single-point measurement yields equivalent results for pool size ratio (PSR). Methods Sixteen different MT-prepared MRI scans were obtained at 3T from sixteen PD patients and eight HCs, along with B1, B0 and relaxation time maps. Maps of PSR, free and macromolecular pool transverse relaxation times ( T2f, T2m) and rate of MT exchange between pools ( kmf) were generated using a full qMT model. PSR maps were also generated using a single-point qMT model requiring just two MT-prepared images. qMT parameter values of the SNc, red nucleus, cerebral crus and grey matter were compared between groups and methods. Results PSR of the SNc was the only qMT parameter to differ significantly between groups (p<0.05). PSR measured via single-point analysis was less variable than with the full MT model, provided slightly better differentiation of PD patients from HCs (area under curve 0.77 vs. 0.75) with sensitivity and specificity of 0.87, and was better than transverse relaxation time in distinguishing PD patients from HCs (area under curve 0.71, sensitivity 0.87 and specificity 0.50). Conclusions The increased PSR observed in the SNc of PD patients may provide a novel biomarker of PD, possibly associated with an increased macromolecular content. Single-point PSR mapping with reduced variability and shorter scan times relative to the full qMT model appears clinically feasible.

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Section: Discussionsupporting

confidence: 60%

Pool size ratio of the substantia nigra in Parkinson’s disease derived from two different quantitative magnetization transfer approaches

et al. 2017

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“…This idea has been supported by in vitro studies showing that the NM-iron complex produces concentration-dependent T 1 shortening effects (Enochs et al, 1997, 1989; Tosk et al, 1992; Trujillo et al, 2017a). However, these observations do not fully explain the contrast enhancement between NM-containing structures and surrounding tissues when MT preparation is performed, and in fact, it has been reported that T 1 values alone cannot account for the contrast seen in NM-MRI images (Hashido and Saito, 2016; Nakane et al, 2008). An in vitro study exploring the MT properties of NM (Trujillo et al, 2017a) showed that the NM-iron complex does not affect the PSR, and therefore does not directly alter the MT effect.…”

Section: Discussionmentioning

confidence: 94%

Quantitative magnetization transfer imaging of the human locus coeruleus

et al. 2019

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The locus coeruleus (LC) is the major origin of norepinephrine in the central nervous system, and is subject to age-related and neurodegenerative changes, especially in disorders such as Parkinson’s disease and Alzheimer’s disease. Previous studies have shown that neuromelanin (NM)-sensitive MRI can be used to visualize the LC, and it is hypothesized that magnetization transfer (MT) effects are the primary source of LC contrast. The aim of this study was to characterize the MT effects in LC imaging by applying high spatial resolution quantitative MT (qMT) imaging to create parametric maps of the macromolecular content of the LC and surrounding tissues. Healthy volunteers (n = 26; sex = 17 F/9M; age = 41.0 ± 19.1 years) underwent brain MRI on a 3.0 T scanner. qMT data were acquired using a 3D MT-prepared spoiled gradient echo sequence. A traditional NM scan consisting of a T1-weighted turbo spin echo sequence with MT preparation was also acquired. The pool-size ratio (PSR) was estimated for each voxel using a single-point qMT approach. The LC was semi-automatically segmented on the MT-weighted images. The MT-weighted images provided higher contrast-ratio between the LC and surrounding pontine tegmentum (PT) (0.215 ± 0.031) than the reference images without MT-preparation (−0.005 ± 0.026) and the traditional NM images (0.138 ± 0.044). The PSR maps showed significant differences between the LC(0.090 ± 0.009) and PT (0.188 ± 0.025). The largest difference between the PSR values in the LC and PT was observed in the central slices, which also correspond to those with the highest contrast-ratio. These results highlight the role of MT in generating NM-related contrast in the LC, and should serve as a foundation for future studies aiming to quantify pathological changes in the LC and surrounding structures in vivo.

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“…Substantia nigra (SN) recording localization in both subjects was done using T1- and T2-weighted MRI (4.7T, Bruker). T2-weighted MRI is especially useful because T2 relaxation times in much shorter in SNr area due to higher iron content ( 47 ). Recoding chambers were equipped with a grid with 2-mm-hole spacing and were filled with gadolinium for better contrast (fig.…”

Section: Methodsmentioning

confidence: 99%

Common coding of expected value and value uncertainty memories in the prefrontal cortex and basal ganglia output

Ghazizadeh

Hikosaka

2021

Sci. Adv.

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Recent evidence implicates both basal ganglia and ventrolateral prefrontal cortex (vlPFC) in encoding value memories. However, comparative roles of cortical and basal nodes in value memory are not well understood. Here, single-unit recordings in vlPFC and substantia nigra reticulata (SNr), within macaque monkeys, revealed a larger value signal in SNr that was nevertheless correlated with and had a comparable onset to the vlPFC value signal. The value signal was maintained for many objects (>90) many weeks after reward learning and was resistant to extinction in both regions and to repetition suppression in vlPFC. Both regions showed comparable granularity in encoding expected value and value uncertainty, which was paralleled by enhanced gaze bias during free viewing. The value signal dynamics in SNr could be predicted by combining responses of vlPFC neurons according to their value preferences consistent with a scheme in which cortical neurons reached SNr via direct and indirect pathways.

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Quantitative T1, T2, and T2* Mapping and Semi-Quantitative Neuromelanin-Sensitive Magnetic Resonance Imaging of the Human Midbrain

Cited by 13 publications

References 58 publications

Pool size ratio of the substantia nigra in Parkinson’s disease derived from two different quantitative magnetization transfer approaches

Pool size ratio of the substantia nigra in Parkinson’s disease derived from two different quantitative magnetization transfer approaches

Quantitative magnetization transfer imaging of the human locus coeruleus

Common coding of expected value and value uncertainty memories in the prefrontal cortex and basal ganglia output

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