Automated assessment of the substantia nigra on susceptibility map-weighted imaging using deep convolutional neural networks for diagnosis of Idiopathic Parkinson's disease.

OBJECTIVES: Despite its use in determining nigrostriatal degeneration, the lack of a consistent interpretation of nigrosome 1 susceptibility map-weighted imaging (SMwI) limits its generalized applicability. To implement and evaluate a diagnostic algorithm based on convolutional neural networks for interpreting nigrosome 1 SMwI for determining nigrostriatal degeneration in idiopathic Parkinson's disease (IPD). METHODS: In this retrospective study, we enrolled 267 IPD patients and 160 control subjects (125 patients with drug-induced parkinsonism and 35 healthy subjects) at our institute, and 24 IPD patients and 27 control subjects at three other institutes on approval of the local institutional review boards. Dopamine transporter imaging served as the reference standard for the presence or absence of abnormalities of nigrosome 1 on SMwI. Diagnostic performance was compared between visual assessment by an experienced neuroradiologist and the developed deep learning-based diagnostic algorithm in both internal and external datasets using a bootstrapping method with 10000 re-samples by the "pROC" package of R (version 1.16.2). RESULTS: The area under the receiver operating characteristics curve (AUC) (95% confidence interval [CI]) per participant by the bootstrap method was not significantly different between visual assessment and the deep learning-based algorithm (internal validation, .9622 [0.8912-1.0000] versus 0.9534 [0.8779-0.9956], P = .1511; external validation, 0.9367 [0.8843-0.9802] versus 0.9208 [0.8634-0.9693], P = .6267), indicative of a comparable performance to visual assessment. CONCLUSIONS: Our deep learning-based algorithm for assessing abnormalities of nigrosome 1 on SMwI was found to have a comparable performance to that of an experienced neuroradiologist.

Comparative assessment of 6-[18 F]fluoro-L-m-tyrosine and 6-[18 F]fluoro-L-dopa to evaluate dopaminergic presynaptic integrity in a Parkinson's disease rat model.

Because of the progressive loss of nigro-striatal dopaminergic terminals in Parkinson's disease (PD), in vivo quantitative imaging of dopamine (DA) containing neurons in animal models of PD is of critical importance in the preclinical evaluation of highly awaited disease-modifying therapies. Among existing methods, the high sensitivity of positron emission tomography (PET) is attractive to achieve that goal. The aim of this study was to perform a quantitative comparison of brain images obtained in 6-hydroxydopamine (6-OHDA) lesioned rats using two dopaminergic PET radiotracers, namely [18 F]fluoro-3,4-dihydroxyphenyl-L-alanine ([18 F]FDOPA) and 6-[18 F]fluoro-L-m-tyrosine ([18 F]FMT). Because the imaging signal is theoretically less contaminated by metabolites, we hypothesized that the latter would show stronger relationship with behavioural and post-mortem measures of striatal dopaminergic deficiency. We used a within-subject design to measure striatal [18 F]FMT and [18 F]FDOPA uptake in eight partially lesioned, eight fully lesioned and ten sham-treated rats. Animals were pretreated with an L-aromatic amino acid decarboxylase inhibitor. A catechol-O-methyl transferase inhibitor was also given before [18 F]FDOPA PET. Quantitative estimates of striatal uptake were computed using conventional graphical Patlak method. Striatal dopaminergic deficiencies were measured with apomorphine-induced rotations and post-mortem striatal DA content. We observed a strong relationship between [18 F]FMT and [18 F]FDOPA estimates of decreased uptake in the denervated striatum using the tissue-derived uptake rate constant Kc . However, only [18 F]FMT Kc succeeded to discriminate between the partial and the full 6-OHDA lesion and correlated well with the post-mortem striatal DA content. This study indicates that the [18 F]FMT could be more sensitive, with respect of [18 F]FDOPA, to investigate DA terminals loss in 6-OHDA rats, and open the way to in vivo L-aromatic amino acid decarboxylase activity targeting in future investigations on progressive PD models.

[Quantitative evaluation of SPECT with FP-CIT. Importance of the reference area]. / Valoración cuantitativa del SPECT con FP-CIT. Importancia del área de referencia.

OBJECTIVE: The aim of this study is to compare several uptake indexes between specific and non-specific activity to determine the existence of degenerative Parkinsonism according to different reference areas. MATERIAL AND METHODS: A total of 46 patients (23 men and 23 women), randomly selected from individuals referred to our center with a movement disorder, were included in the study. Mean age was 70.2 ± 10.2 years (41-87). The uptake indexes were obtained through the areas of interest (ROIs) located in the striate (specific uptake) and other reference ROIs located in areas with different concentrations of serotonin receptors: low-cerebellum, medium-occipital cortex and high-midbrain. RESULTS: A high linear correlation was found between indexes having low and medium concentration of serotonin receptors. The ROC curve analysis shows an area under the curve of 0.874, 0.886 and 0.739 and regression coefficients of 5.41, 6.62 and 3.41, respectively for the striatum/cerebellum (E/C), striatum/occipital (E/O) and striatum midbrain (E/M) indexes. Optimal cutoff for E/O (1.35), index with the best behavior, provides a sensitivity of 0.84 and specificity of 0.89. CONCLUSION: The reference area selected may alter the predictive power of the different indexes to determine the existence of a degenerative Parkinsonism.

[Comparative assessment of clinical features and imaging findings for patients with vascular parkinsonism and idiopathic Parkinson's disease].

OBJECTIVE: To compare the differences of clinical features and imaging findings between vascular parkinsonism (VP) and idiopathic Parkinson's disease (PD). METHOD: The clinical features and imaging findings from 54 patients with VP and 53 patients with PD were compared. RESULTS: The main clinical manifestations of patients with VP were hemiplegia, rigidity and bulbar palsy with obviously pyramidal tract system damage and less rest tremor. Patients with PD showed remarkable tremor-cogwheel rigidity. In the aspect of imageology, there were obvious imaging changes in patients with VP, mainly manifested lacunar infarction located in unilateral or bilateral basal ganglia and white matter of frontal lobe. Furthermore, some ischemic changes could be seen in the cerebral peduncle and lateral cerebral ventricle. In patients with PD, ischemic changes were invisible. As to the therapeutic effect to the anti-Parkinson's disease, patients with PD showed better effect than VP patients. CONCLUSION: As a self-sustaining clinical syndrome, the clinical manifestations and imaging findings in patients with VP are different from those with PD.

The role of positron emission tomography in the assessment of human neurotransplantation.

Positron emission tomography (PET) using tracers of the dopaminergic system has been used to measure striatal function in a small number of parkinsonian patients undergoing neurotransplantation procedures. Some postoperative scans have shown an unequivocal increase in presynaptic dopaminergic function at the graft site, providing evidence of graft survival independent of clinical assessment. Combined PET and magnetic resonance imaging (MRI) images provide the facility to explore the relationship between graft placement, survival and clinical efficacy.