Investigation of spatial resolution characteristics of an in vivo microcomputed tomography system

Ghani, Muhammad U.; Zhou, Zhongxing; Ren, Liqiang; Wong, Molly D.; Li, Yuhua; Yang, Kai; Liu, Hong

doi:10.1016/j.nima.2015.11.007

Cited by 26 publications

(15 citation statements)

References 25 publications

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“…A substantial difference in the resolution can be seen at lower frequencies when comparing the spatial resolution for the two scanning directions. We can infer that the small focal spot size in the vertical direction will have a favorable impact on the spatial resolution in the z-plane of the cone beam CTs as observed in previous studies [40, 41]. Our analysis suggests that the performance of the two emission modes was similar in terms of spatial resolution.…”

Section: Discussionsupporting

confidence: 78%

Characterization of continuous and pulsed emission modes of a hybrid micro focus x-ray source for medical imaging applications

Ghani

Wong

Ren

et al. 2017

Nuclear Instruments and Methods in Physics Research Section A:

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The aim of this study was to quantitatively characterize a micro focus x-ray tube that can operate in both continuous and pulsed emission modes. The micro focus x-ray source (Model L9181-06, Hamamatsu Photonics, Japan) has a varying focal spot size ranging from 16–50 μm as the source output power changes from 10–39 W. We measured the source output, beam quality, focal spot sizes, kV accuracy, spectra shapes and spatial resolution. Source output was measured using an ionization chamber for various tube voltages (kVs) with varying current (μA) and distances. The beam quality was measured in terms of half value layer (HVL), kV accuracy was measured with a non-invasive kV meter, and the spectra was measured using a compact integrated spectrometer system. The focal spot sizes were measured using a slit method with a CCD detector with a pixel pitch of 22 μm. The spatial resolution was quantitatively measured using the slit method with a CMOS flat panel detector with a 50 μm pixel pitch, and compared to the qualitative results obtained by imaging a contrast bar pattern. The focal spot sizes in the vertical direction were smaller than that of the horizontal direction, the impact of which was visible when comparing the spatial resolution values. Our analyses revealed that both emission modes yield comparable imaging performances in terms of beam quality, spectra shape and spatial resolution effects. There were no significantly large differences, thus providing the motivation for future studies to design and develop stable and robust cone beam imaging systems for various diagnostic applications.

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Section: Discussionsupporting

confidence: 78%

Characterization of continuous and pulsed emission modes of a hybrid micro focus x-ray source for medical imaging applications

Ghani

Wong

Ren

et al. 2017

Nuclear Instruments and Methods in Physics Research Section A:

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“…While linear ramp (Ram-Lak) is the intrinsic back projection filter used in the reconstruction process, shepp-logan and cosine filters are also available that can be used during the reconstruction process. Detailed specifications of the system can be found elsewhere [25]. The specifications associated with each field of view (FOV) used in this study are given in Table 1.…”

Section: Methodsmentioning

confidence: 99%

Noise Power Characteristics of a Micro–Computed Tomography System

Ghani

Ren

Wong

et al. 2017

Journal of Computer Assisted Tomography

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Objective The aim of this study was to investigate the noise power properties of a micro computed tomography (micro-CT) system under different operating conditions. Methods A commercial micro-CT was utilized in the study that employed a flat panel detector with a 127 µm pixel pitch, and a micro focus x-ray tube. Conical tubes of various diameters were used under different acquisition conditions. Multidimensional noise power spectrums (NPS) were used as a metric to investigate the noise properties of the system. NPS was calculated from the difference data generated by subtraction of two identical scans. The noise properties with respect to various parameters that include the impact of number of projections, x-ray spectra, mAs, slice location, object diameter, voxel size, geometric magnification (M), back projection filters and reconstruction magnification (MRecon) were studied. Results At a same isocentric exposure rate of 270 mR/s, the noise power was much lower for the image reconstructed with 3672 views (122 s) as compared to the 511 views (17 s); while at a fixed isocentric exposure of 4600 mR, the noise power levels were almost similar. Image noise with a 50 kV beam was higher as compared to the 90 kV beam at a same isocentric exposure. Image noise from a 16 mm diameter conical tube was much lower as compared to the 28 mm and 56 mm tubes under identical isocentric exposures. The choice of back-projection filter influence NPS curves in terms of width and amplitudes. MRecon applied during the reconstruction process increased the noise power at lower spatial frequencies while reduced the noise power at higher spatial frequencies. It can be established that for small details corresponding to high spatial frequencies, MRecon can provide an improved SNR. At all spatial frequencies, the in-plane images had lower noise power levels as compared to the z-plane images. Conclusion The noise power properties investigated in this study provide important image quality references for refined cone beam system development, optimization and operations.

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“…Nevertheless, the summary resolution metrics may also be used; the limiting spatial resolution is defined as the frequency at which the MTF drops below a certain percent value. Several values can be used; however, the 10% level is the most common one [50][51][52].…”

Section: Modulation Transfer Function (Mtf)mentioning

confidence: 99%

Characterization with X-rays of a Large-Area GEMPix Detector with Optical Readout for QA in Hadron Therapy

et al. 2021

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Quality Assurance (QA) in hadron therapy is crucial to ensure safe and accurate dose delivery to patients. This can be achieved with fast, reliable and high-resolution detectors. In this paper, we present a novel solution that combines a triple Gas Electron Multiplier (GEM) and a highly pixelated readout based on a matrix of organic photodiodes fabricated on top of an oxide-based thin-film transistor backplane. The first LaGEMPix prototype with an active area of 60 × 80 mm2 was developed and characterized using low energy X-rays. The detector comprises a drift gap of 3.5 mm, a triple-GEM stack for electron amplification, and a readout featuring 480 × 640 pixels at a 126 µm pitch. Here, we describe the measurements and results in terms of spatial resolution for various experimental configurations. A comparison with GAFCHROMIC® films and the GEMPix detector used in the charge readout mode was performed to better understand the contribution to the spatial resolution from both the electron diffusion and the isotropic emission of photons. The measurements were compared to Monte Carlo simulations, using the FLUKA code. The simulation predictions are in good agreement with the GEMPix results. Future plans with respect to applications in hadron therapy are discussed.

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Investigation of spatial resolution characteristics of an in vivo microcomputed tomography system

Cited by 26 publications

References 25 publications

Characterization of continuous and pulsed emission modes of a hybrid micro focus x-ray source for medical imaging applications

Characterization of continuous and pulsed emission modes of a hybrid micro focus x-ray source for medical imaging applications

Noise Power Characteristics of a Micro–Computed Tomography System

Characterization with X-rays of a Large-Area GEMPix Detector with Optical Readout for QA in Hadron Therapy

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