arXiv subjects

Youngho Seo

Publications and source records attributed to Youngho Seo.

7 recordsLinked to original sources

arXiv2025

Configurable γ Photon Spectrometer to Enable Precision Radioguided Tumor Resection

Surgical tumor resection aims to remove all cancer cells in the tumor margin and at centimeter-scale depths below the tissue surface. During surgery, microscopic clusters of disease are intraoperatively difficult to visualize and are often left behind, significantly increasing the risk of cancer recurrence. Radioguided surgery (RGS) has shown the ability to selectively tag cancer cells with gamma (γ) photon emitting radioisotopes to identify them, but require a mm-scale γ photon spectrometer to localize the position of these cells in the tissue margin (i.e., a function of incident γ photon energy) with high specificity. Here we present a 9.9 mm2 integrated circuit (IC)-based γ spectrometer implemented in 180 nm CMOS, to enable the measurement of single γ photons and their incident energy with sub-keV energy resolution. We use small 2 2 um reverse-biased diodes that have low depletion region capacitance, and therefore produce millivolt-scale voltage signals in response to the small charge generated by incident γ photons. A low-power energy spectrometry method is implemented by measuring the decay time it takes for the generated voltage signal to settle back to DC after a γ detection event, instead of measuring the voltage drop directly. This spectrometry method is implemented in three different pixel architectures that allow for configurable pixel sensitivity, energy-resolution, and energy dynamic range based on the widely heterogenous surgical and patient presentation in RGS. The spectrometer was tested with three common γ-emitting radioisotopes (64Cu, 133Ba, 177Lu), and is able to resolve activities down to 1 uCi with sub-keV energy resolution and 1.315 MeV energy dynamic range, using 5-minute acquisitions.

eess.IV↗

arXiv2025

Design and Evaluation of CZT-based Micro-activity Dose Calibrator for TAT Application using Monte Carlo Simulation

A novel CZT-based micro-activity dose calibrator has been designed via Monte Carlo simulation (GATE) to accurately measure low-level activity 225Ac for targeted alpha therapy (TAT) application. Because even small overdoses in TAT can induce severe local toxicity, activities in the microcurie down to nanocurie regime are often required, and accurate activity measurement by dose calibrators is a priori to safe and effective treatment. Standard dose calibrators, or high-pressurized gas-filled ionization chambers, are not suitable in this range due to limited sensitivity and lack of energy discrimination. To address this, we designed a CZT-based micro-activity calibrator that (i) adopts a box-shaped well geometry to obtain higher solid-angle coverage and (ii) applies time-coincident pixel-level clustering to recover full-energy-peak net counts otherwise lost to multi-site Compton scattering. Using GATE, serial dilutions from 1.0 uCi down to 1e-6 uCi were simulated, activities were reconstructed from the 218 and 440 keV gamma peaks and performance was compared against a NaI(Tl) well counter, which serves as an alternative to standard dose calibrator. Across six orders of magnitude, the CZT-based micro-activity dose calibrator exhibited near-unity linearity (slope m=0.9934) with percent-level bias, whereas the NaI(Tl) counter showed systematic under-response under identical conditions. These results indicate that a CZT-based approach can provide accurate low-activity quantification for TAT, motivating forthcoming hardware validation.

physics.ins-det↗

arXiv2020

Transaction-level Model Simulator for Communication-Limited Accelerators

Rapid design space exploration in early design stage is critical to algorithm-architecture co-design for accelerators. In this work, a pre-RTL cycle-accurate accelerator simulator based on SystemC transaction-level modeling (TLM), AccTLMSim, is proposed for convolutional neural network (CNN) accelerators. The accelerator simulator keeps track of each bus transaction between accelerator and DRAM, taking into account the communication bandwidth. The simulation results are validated against the implementation results on the Xilinx Zynq. Using the proposed simulator, it is shown that the communication bandwidth is severely affected by DRAM latency and bus protocol overhead. In addition, the loop tiling is optimized to maximize the performance under the constraint of on-chip SRAM size. Furthermore, a new performance estimation model is proposed to speed up the design space exploration. Thanks to the proposed simulator and performance estimation model, it is possible to explore a design space of millions of architectural options within a few tens of minutes.

cs.AR↗

arXiv2018

Joint Correction of Attenuation and Scatter Using Deep Convolutional Neural Networks (DCNN) for Time-of-Flight PET

Deep convolutional neural networks (DCNN) have demonstrated its capability to convert MR image to pseudo CT for PET attenuation correction in PET/MRI. Conventionally, attenuated events are corrected in sinogram space using attenuation maps derived from CT or MR-derived pseudo CT. Separately, scattered events are iteratively estimated by a 3D model-based simulation using down-sampled attenuation and emission sinograms. However, no studies have investigated joint correction of attenuation and scatter using DCNN in image space. Therefore, we aim to develop and optimize a DCNN model for attenuation and scatter correction (ASC) simultaneously in PET image space without additional anatomical imaging or time-consuming iterative scatter simulation. For the first time, we demonstrated the feasibility of directly producing PET images corrected for attenuation and scatter using DCNN (PET-DCNN) from noncorrected PET (PET-NC) images.

cs.CV↗

arXiv2018

Attenuation correction for brain PET imaging using deep neural network based on dixon and ZTE MR images

Positron Emission Tomography (PET) is a functional imaging modality widely used in neuroscience studies. To obtain meaningful quantitative results from PET images, attenuation correction is necessary during image reconstruction. For PET/MR hybrid systems, PET attenuation is challenging as Magnetic Resonance (MR) images do not reflect attenuation coefficients directly. To address this issue, we present deep neural network methods to derive the continuous attenuation coefficients for brain PET imaging from MR images. With only Dixon MR images as the network input, the existing U-net structure was adopted and analysis using forty patient data sets shows it is superior than other Dixon based methods. When both Dixon and zero echo time (ZTE) images are available, we have proposed a modified U-net structure, named GroupU-net, to efficiently make use of both Dixon and ZTE information through group convolution modules when the network goes deeper. Quantitative analysis based on fourteen real patient data sets demonstrates that both network approaches can perform better than the standard methods, and the proposed network structure can further reduce the PET quantification error compared to the U-net structure.

physics.med-ph↗

arXiv2003

Mini-LANNDD T40: A detector to measure the neutrino-argon cross section and the electron-neutrino contamination in the off-axis NuMI beam

We describe a preliminary study of a 40-ton liquid argon TPC based on the ICARUS method to use in the NuMI near region in line with the LANNDD project. This reduced-scale detector, called ``Mini-LANNDD T40'', is designed for R&D purposes and systematic measures on its response. Safety concerns are a key issue, which will be discussed as well as a preliminary design of the detector. Adapted as a near or vertex detector in a neutrino beam, the Mini-LANNDD T40 is capable of observing the electron-neutrino flux in the off-axis beam, a key to use for measuring $\sin^2 2 θ_{13}$ in the future, and measuring the low energy neutrino-argon cross-section, an important piece of information for future long baseline experiments.

astro-ph↗

arXiv2002

Study of the Backgrounds for the Search for Proton Decay to 10^35 Y at the WIPP Site with the LANNDD Detector

We briefly describe the LANNDD 70-kT liquid argon TPC proposal for the WIPP underground facility at Carlsbad, New Mexico. We, then, identify the key backgrounds for the search for p -> K+ nu_bar to 10^35 years lifetime. The most serious non-neutrino background is due to high-energy neutrons producing strange particles in the detector. We show that this can be reduced to an acceptable level by appropriate fiducial volume cuts.

astro-ph↗