Study of the Microfocus X-Ray Tube Based on a Point-Like Target Used for Micro-Computed Tomography

Abstract

For a micro-Computed Tomography (Micro-CT) system, the microfocus X-ray tube is an essential component because the spatial resolution of CT images, in theory, is mainly determined by the size and stability of the X-ray focal spot of the microfocus X-ray tube. However, many factors, including voltage fluctuations, mechanical vibrations, and temperature changes, can cause the size and the stability of the X-ray focal spot to degrade. A new microfocus X-ray tube based on a point-like micro-target in which the X-ray target is irradiated with an unfocused electron beam was investigated. EGS4 Monte Carlo simulation code was employed for the calculation of the X-ray intensity produced from the point-like micro-target and the substrate. The effects of several arrangements of the target material, target and beam size were studied. The simulation results demonstrated that if the intensity of X-rays generated at the point-like target is greater than half of the X-ray intensity produced on the substrate, the X-ray focal spot is determined in part by the point-like target rather than by the electron beam in the conventional X-ray tube. In theory, since it is able to reduce those unfavorable effects such as the electron beam trajectory swinging and the beam size changing for the microfocus X-ray tube, it could alleviate CT image artifacts caused by the X-ray focal spot shift and size change.

Lenseless X-ray Nano-Tomography down to 150nm Resolution: On the Quantification of Modulation Transfer and Focal Spot of the Lab-based ntCT System

“…In addition, a contribution of 20% of the total emitted intensity can be observed when focusing the electron beam on the bare diamond vacuum window, which may originate from the vacuum window itself, from de-focused electrons hitting distant target regions, or from residual metals on the vacuum window. However, bremsstrahlung generated within the vacuum window (which also serves as the structured target's substrate) is indeed expected from Monte Carlo simulations [31], and will, due to the window's much larger thickness as compared to the actual target material, indeed exhibit a considerably wider FWHM as compared to the main contribution from the target layer.…”

Design and fabrication of multi-metal patterned target anodes for improved quality of hyperspectral x-ray radiography and computed tomography imaging systems

“…The detector produces spectral data, such that when a photon interacts with a pixel on the detector, the photon is binned into one of 128 channels based on its energy. The spatial resolution improvements described in this work are inspired of the previous work of Zhou et al 4 They proposed that using an anode comprised of a substrate transparent to X-rays with embedded metal features smaller than the electron beam effectively shrinks the focal spot size of the system to the size of the smaller metal features. Zhou et al 4 demonstrated this through simulation, showing that the X-rays generated from the anode mostly come from the embedded metal features while radiation generated from the substrate was minimal.…”

“…The spatial resolution improvements described in this work are inspired of the previous work of Zhou et al 4 They proposed that using an anode comprised of a substrate transparent to X-rays with embedded metal features smaller than the electron beam effectively shrinks the focal spot size of the system to the size of the smaller metal features. Zhou et al 4 demonstrated this through simulation, showing that the X-rays generated from the anode mostly come from the embedded metal features while radiation generated from the substrate was minimal. This established that the effective focal spot size is proportional to the diameter of the metal in the anode, thus improving spatial resolution.…”

“…This configuration resulted in producing XPCI images more efficiently and with fewer artifacts. 5 Previous work by Dalton et al 6 showed through simulation that a multi-metal patterned anode based on the combined efforts by Zhou et al 4 and Morimoto et al 5 and combined with a hyperspectral X-ray detector further improves spatial resolution when focused on narrow X-ray energy neighborhoods. This work simulated a typical W anode and a multi-metal patterned anode; the goal of the simulations was to compare SNR and spatial resolution about the emission lines of the metals contained within the multi-metal anode.…”

Design optimization of a periodic microstructured array anode for hard x-ray grating interferometry

“…Figure 3(d) shows the X-ray production efficiency of three transmission MAATs with optimized thickness of MMI as a function of electron beam energy. Compared with the single microstructured anode target (SMAT) proposed by Ihsan (Ihsan et al 2009, Zhou et al 2016), the optimal thickness of transmission W-MMI becomes larger. For instance, at the electron energy 90 keV, the optimal thickness of transmission W-MMI is 15.0 μm , while the optimal thickness of SMAT is less than 5.0 μm .…”