Contrastive learning methods have been widely adopted in numerous unsupervised and self-supervised visual representation methods. Such algorithms aim to maximize the cosine similarity between two positive samples while minimizing that of negative samples. Recently, Grill et al. propose an algorithm, BYOL [1], utilize only samples, completely giving up on ones, by introducing a Siamese-like asym...

An ordered subsets expectation maximization (OS-EM) algorithm is used for image reconstruction to suppress image noise and to make non-negative value images. We have applied OS-EM to a digital brain phantom and to human brain 18F-FDG PET kinetic studies to generate parametric images. A 45 min dynamic scan was performed starting injection of FDG with a 2D PET scanner. The images were reconstruct...

Due to low counts in an (111)In single photon emission computed tomography (SPECT) scan, a large part of the head was missing in the reconstructed images on Philips Extended Brilliance Workspace (EBW) and IntelliSpace Portal (ISP) workstations. This problem occurred for the ordered subsets expectation maximization (OSEM) algorithm with and without resolution recovery (Astonish), but not for fil...

Background: In this study, Quantitative 32P bremsstrahlung planar and SPECT imaging and consequent dose assessment were carried out as a comprehensive phantom study to define an appropriate method for accurate Dosimetry in clinical practice. Materials and Methods: CT, planar and SPECT bremsstrahlung images of Jaszczak phantom containing a known activity of 32P were acquired. In addition, Phanto...

the aim of this study is to introduce a parametric mixture model to analysis the competing-risks data with two types of failure. in mixture context, i t h type of failure is i th component. the baseline failure time for the first and second types of failure are modeled as proportional hazard models according to weibull and gompertz distributions, respectively. the covariates affect on both the ...

OBJECTIVE With the increasing number of patients undergoing positron emission tomography (PET) scans and the fact that multiple whole body acquisitions are performed during therapy monitoring, the reduction of scan time as well as of the injected radioactive dose are important issues. However, short scan time and reduction of the injected radiation dose result in low count statistics, which sig...

Iterative algorithms such as MLEM are rapidly becoming the standard for reconstruction in emission computed tomography. However, such algorithms require arbitrary stopping criteria, are sensitive to noise artifacts, and require accelerated implementations that may not work well for all imaging situations. We have investigated several new iterative algorithms with likelihood-based objective func...

let $s$ be an ordered semigroup. a fuzzy subset of $s$ is anarbitrary mapping   from $s$ into $[0,1]$, where $[0,1]$ is theusual interval of real numbers. in this paper,  the concept of fuzzygeneralized bi-ideals of an ordered semigroup $s$ is introduced.regular ordered semigroups are characterized by means of fuzzy leftideals, fuzzy right ideals and fuzzy (generalized) bi-ideals.finally, two m...

The reconstruction of sparse signal is an active area research. Different from a typical i.i.d. assumption, this paper considers non-independent prior group structure. For more practical setup, we propose EM-aided HyGEC, new algorithm to address the stability issue and hyper-parameter facing other algorithms. instability problem results ill condition transform matrix, while unavailability hyper...