Annihilation photon GAN source model for PET Monte Carlo simulation.

Objective.Following previous works on virtual sources model with Generative Adversarial Network (GAN), we extend the proof of concept for generating back-to-back pairs of gammas with timing information, typically for Monte Carlo simulation of Positron Emission Tomography(PET) imaging.Approach.A conditional GAN is trained once from a low statistic simulation in a given attenuation phantom and enables the generation of various activity source distributions. GAN training input is a set of gammas exiting a phantom, tracked from a source of positron emitters, described by position, direction and energy. A new parameterization that improves the training is also proposed. An ideal PET reconstruction algorithm is used to evaluate the quality of the GAN.Main results.The proposed method is evaluated on National Electrical Manufacturers Association (NEMA) International Electrotechnical Commission (IEC) phantoms and with CT patient image showing good agreement with reference simulations. The proportions of 2-gammas, 1-gammas and absorbed-gammas are respected to within one percent, image profiles matched and recovery coefficients were close with less than 5% difference. GAN tends to blur gamma energy peak, e.g. 511 keV.Significance.Once trained, the GAN generator can be used as input source for Monte Carlo simulations of PET imaging systems, decreasing the computational time with speedups up to ×400 according to the configurations.

Therapeutic hypothermia for neonatal encephalopathy results in improved microstructure and metabolism in the deep gray nuclei.

BACKGROUND AND PURPOSE: Therapeutic hypothermia has reduced morbidity and mortality and is associated with a lower burden of lesions on conventional imaging in NE. However, its effects on brain microstructure and metabolism have not been fully characterized. We hypothesized that therapeutic hypothermia improves measures of brain microstructure and metabolism. MATERIALS AND METHODS: Forty-one neonates with moderate/severe NE (29 treated with hypothermia, 12 nontreated) and 12 healthy neonates underwent MR imaging, DTI, and (1)H-MR spectroscopy. MR imaging scans were scored by the predominant pattern of brain injury: normal, watershed, and BG/thalamus. ADC, FA, Lac:NAA, and NAA:Cho values from bilateral BG and thalamus ROIs were averaged. T test and linear regression analysis were used to determine the association between hypothermia and MR imaging quantitative measures. RESULTS: Conventional MR imaging findings were normal in 41% of treated neonates; all nontreated neonates had brain injury. Values of MR imaging metrics were closer to normal in treated neonates compared with nontreated neonates: ADC was 63% higher in the BG and 116% higher in the thalamus (both P < .05), and Lac:NAA was 76% lower (P = .04) in the BG. Treated neonates with normal MR imaging findings had normal (1)H-MR spectroscopy metabolites, and ADC was higher by 35% in the thalamus (P = .03) compared with healthy neonates. CONCLUSIONS: Therapeutic hypothermia may reduce disturbances of brain metabolism and preserve its microstructure in the setting of NE, possibly by minimizing cytotoxic edema and cell death. Long-term follow-up studies are required to determine whether early post-treatment DTI and (1)H-MR spectroscopy will be useful biomarkers of treatment response.

Strategy for genetic testing in Charcot-Marie-disease.

BACKGROUND: Charcot Marie Tooth disease (CMT) affects one in 2500 people. Genetic testing is often pursued for family planning purposes, natural history studies and for entry into clinical trials. However, identifying the genetic cause of CMT can be expensive and confusing to patients and physicians due to locus heterogeneity. METHODS: We analyzed data from more than 1000 of our patients to identify distinguishing features in various subtypes of CMT. Data from clinical phenotypes, neurophysiology, family history, and prevalence was combined to create algorithms that can be used to direct genetic testing for patients with CMT. FINDINGS: The largest group of patients in our clinic have slow motor nerve conduction velocities (MNCV) in the upper extremities. Approximately 88% of patients in this group have CMT1A. Those who had intermediate MNCV had primarily CMT1X (52.8%) or CMT1B (27.8%). Patients with very slow MNCV and delayed walking were very likely to have CMT1A (68%) or CMT1B (32%). No patients with CMT1B and very slow MNCV walked before 15 months of age. Patients with CMT2A form our largest group of patients with axonal forms of CMT. INTERPRETATION: Combining features of the phenotypic and physiology groups allowed us to identify patients who were highly likely to have specific subtypes of CMT. Based on these results, we created a series of algorithms to guide testing. A more detailed review of this data is published in Annals of Neurology (1).