Peter Choi | Searcharxiv

arXiv2024

MRAnnotator: multi-Anatomy and many-Sequence MRI segmentation of 44 structures

In this retrospective study, we annotated 44 structures on two datasets: an internal dataset of 1,518 MRI sequences from 843 patients at the Mount Sinai Health System, and an external dataset of 397 MRI sequences from 263 patients for benchmarking. The internal dataset trained the nnU-Net model MRAnnotator, which demonstrated strong generalizability on the external dataset. MRAnnotator outperformed existing models such as TotalSegmentator MRI and MRSegmentator on both datasets, achieving an overall average Dice score of 0.878 on the internal dataset and 0.875 on the external set. Model weights are available on GitHub, and the external test set can be shared upon request.

eess.IV↗

arXiv2006

Reproducibility of a Titanium Plasma Vacuum Spark Discharge

The results of an extensive operation of a Vacuum Spark plasma using Titanium electrodes in a 120 ns 150 kA discharge are presented. The hot spots are found to form with a regular spacing in a zippering Z-pinch plasma, which forms close to the cathode and extends to approximately two thirds of the anode separation over a period of a few ns. The axis of the discharge is well defined by an initial plasma from a Nd:YAG laser focussed onto the cathode electrode surface. The statistics of the formation of the hot spots are given for the life of one anode electrode. Between one and three hotspots form and the favored positions are at 1.5 and 3.0 mm from the cathode and the strongest emission, as observed in a filtered X-ray pinhole camera, comes from the hot spot closest to the cathode. The emission spectra resolved between 50 and 350 \AA shows a wide range of Ti ionization which allows the temperatures of the anode blow off plasma, the Z-pinch and the hot spot plasma to be distinguished. These results are compared with filtered PIN diode signals and filtered pinhole images.

physics.plasm-ph↗