TestSTORM: Simulator for optimizing sample labeling and image acquisition in localization based super-resolution microscopy.

Localization-based super-resolution microscopy image quality depends on several factors such as dye choice and labeling strategy, microscope quality and user-defined parameters such as frame rate and number as well as the image processing algorithm. Experimental optimization of these parameters can be time-consuming and expensive so we present TestSTORM, a simulator that can be used to optimize these steps. TestSTORM users can select from among four different structures with specific patterns, dye and acquisition parameters. Example results are shown and the results of the vesicle pattern are compared with experimental data. Moreover, image stacks can be generated for further evaluation using localization algorithms, offering a tool for further software developments.

Single-energy material decomposition using X-ray path length estimation.

OBJECTIVE: Clinical computed tomographies (CTs) can typically use only a single energy at a time. The main purpose of the present paper was to study whether the calculated x-ray path lengths can help replace one of the 2 dual-energy measurements by 2-material decomposition. METHOD: The proposed single-energy material decomposition method (SEMD) is based on the evaluation of a single CT scan. The SEMD combines postreconstruction and prereconstruction algorithms for the determination of x-ray path length and material decomposition, respectively. RESULTS: The simulation results of the proposed and dual-energy methods were compared using pregenerated look-up tables. The results show that SEMD is more sensitive to CT signal errors at higher tube voltages. The dual-energy method is generally less sensitive to CT signal bias but more sensitive to the noise. CONCLUSIONS: In the case of inferior signal errors, the proposed method gives the same results as the dual-energy variant. Although the x-ray path length estimation method with SEMD is more complex, the dose is considerably lower.

Monte Carlo simulation of the effects of anode surface roughness on x-ray spectra.

PURPOSE: Spectral and angular distribution of the x-ray beam generated by medical x-ray tubes as a function of anode surface roughness was analyzed. METHODS: Different sets of profiles such as ideal flat, regular profiles, and measured profiles adopted from the literature were analyzed by means of MCNPX Monte Carlo simulator. The geometry used was simplified to separate different physical effects. A sphere centered on the origin of the coordinate system was divided into two hemispheres filled with tungsten and a vacuum, respectively. The studied anode surfaces were placed at the center of the plane of the hemisphere. The profiles were realized by means of the general lattice structure of the MCNPX. The energy and angular distributions of the excited photons were recorded with energy and angular resolutions of 0.5 keV and 1 degrees, respectively, by means of point detectors. The range of the studied anode surface roughness was 0-550 micro Ra. The emission angle dependencies of the following quantities were analyzed: Half value layer (HVL) value, intensity, and spectral photon flux. RESULTS: The analysis of the HVL of the x-ray beam showed that around an emission angle of 5 degrees, the hardness of the beam was practically independent of the surface roughness. The value of this emission angle depends on the filtration. Below this critical angle, the HVL value decreases, while at a higher emission angle, the beam becomes harder with increasing surface roughness. The intensity degradation saturates with increasing roughness. The position of the maximum spectral photon flux shifts to higher emission angles as the anode surface roughness increases. The surface roughness (Ra) was found to be an inadequate quantity to describe the effect of anode surface roughness on x-ray spectra since no definite connection was found between the values of the intensity degradation and surface roughness. At 120 kVp tube voltage and at a 3.84 microm Ra roughness value, the effect of anode surface roughness introduces a 5% and 12% intensity degradation at a 5 degrees and 12 degrees emission angle, respectively. However, it has a higher impact at low tube voltages (<60 keV), e.g., in mammography systems where the intensity degradation could even be 25% at the "newly" polished anode surface. CONCLUSIONS: The effects of anode surface roughness on x-ray spectra were successfully simulated by a Monte Carlo method. It was proved that the effect of the anode surface roughness could not be modeled by simple filters made from the anode material. The surface roughness (Ra) was found to be an inadequate quantity to describe the effect of anode surface roughness on x-ray spectra.

Monte Carlo analysis of energy dependent anisotropy of bremsstrahlung x-ray spectra.

The energy resolved emission angle dependence of x-ray spectra was analyzed by MCNPX (Monte Carlo N particle Monte Carlo) simulator. It was shown that the spectral photon flux had a maximum at a well-defined emission angle due to the anisotropy of the bremsstrahlung process. The higher the relative photon energy, the smaller the emission angle belonging to the maximum was. The trends predicted by the Monte Carlo simulations were experimentally verified. The Monte Carlo results were compared to both the Institute of Physics and Engineering in Medicine spectra table and the SPEKCALCV1.0 code.