Simulation and optimization of system configuration for the stationary head CT using CNT x-ray source array: reconstruction and quality evaluation

Luo, Yueting; Spronk, Derrek; Lee, Yueh Z.; Zhou, Otto; Lü, Jianping

doi:10.1117/12.2549996

Cited by 8 publications

(5 citation statements)

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“…The processed projection images from all source positions were used to reconstruct volumetric CT images using an iterative reconstruction (IR) algorithm based on the ASTRA Toolbox (Luo et al 2020, van Aarle 2016. All ´N 360 source projection views were included in one single system matrix, including the distinct source/ detector geometry for each projection view.…”

Section: Adjacent Scattering Ratio Subtraction (Asrs) and Ct Image Re...mentioning

confidence: 99%

Evaluation of the feasibility of a multisource CBCT for maxillofacial imaging

Inscoe

et al. 2023

Phys. Med. Biol.

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Objective: The aim of this study was to investigate the feasibility of improving the image quality and accuracy of cone beam computed tomography (CBCT) by replacing the conventional wide cone angle X-ray tube with a distributed X-ray source array positioned in the axial direction. Approach: The multisource CBCT (ms-CBCT) design was experimentally simulated using a benchtop scanner with a carbon nanotube (CNT) X-ray tube and a flat-panel detector. The source was collimated and translated in the axial direction to simulate a source array with a reduced cone angle for each beam. An adjacent scatter ratio subtraction (ASRS) method was implemented for residual scatter reduction. Several phantoms were imaged using the ms-CBCT and conventional CBCT configurations under otherwise similar conditions. The requirements of the ms-CBCT design on the X-ray source and detector were evaluated.Main results: Compared to the conventional CBCT, the ms-CBCT design with 8 sources and ASRS significantly improved the image quality and accuracy, including: 1) reducing the cupping artifact from 15% to 3.5%; 2) reducing the spatial nonuniformity of the CT Hounsfield unit (HU) values from 38.0 to 9.2; 3) improving the contrast-to-noise ratio of the low contrast objects (acrylic and low density polyethylene inserts) against the water-equivalent background by ~20% and 4) reducing the root-mean-square error of the HU values by 70%, from 420.1 to 124.4. The imaging dose and scanning time used by the current clinical CBCT for maxillofacial imaging can be achieved by current source and detector technologies. Significance: The ms-CBCT design significantly reduces the scatter and improves the image quality and accuracy compared to the conventional CBCT.

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Section: Adjacent Scattering Ratio Subtraction (Asrs) and Ct Image Re...mentioning

confidence: 99%

Evaluation of the feasibility of a multisource CBCT for maxillofacial imaging

Inscoe

et al. 2023

Phys. Med. Biol.

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“…Multiple source‐detector geometries have been evaluated through simulation, 22 and one potential configuration has been constructed using this same CNT x‐ray source array 23 . These results suggest that sufficient sinogram coverage of the object can be acquired by a triangular configuration of three arrays.…”

Section: Methodsmentioning

confidence: 98%

Evaluation of carbon nanotube x‐ray source array for stationary head computed tomography

et al. 2021

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Purpose Stationary computed tomography (s‐CT) conceptually offers several advantages over existing rotating gantry‐based CT. Over the last 40 yr, s‐CT has been investigated using different technological approaches. We are developing a s‐CT system specifically for head/brain imaging using carbon nanotube (CNT)‐based field emission x‐ray source array technology. The noncircular geometry requires different assessment approaches as compared to circular geometries. The purpose of the present study is to investigate whether the CNT source array meets the requirements for stationary head CT (s‐HCT). Methods Multiple prototype CNT x‐ray source arrays were manufactured based on the system requirements obtained from simulation. Source characterization was performed using a benchtop setup consisting of an x‐ray source array with 45 distributed focal spots, each operating at 120 kVp, and an electronic control system (ECS) for high speed control of the x‐ray output from individual focal spots. Due to the forward‐angled geometry of the linear anode, the projected focal spot shape is expected to vary at wide angle views. A pinhole method was implemented to determine the effective focal spot size (FSS) in the imaging plane at a range of angular viewpoints with a flat panel detector. The output spectrum and half value layer (HVL) were also evaluated for a range of viewing angles to characterize the beam quality across the fan‐beam. Dosimetry was performed on a simulated scan to evaluate total exposure. Results The prototype CNT x‐ray source array demonstrated adequate specifications for a s‐HCT imaging machine. The source array was operated at 120 kVp with long‐term stability over a full year of regular laboratory use. Multiple cathode current measurements were used to confirm submicrosecond accuracy with regards to exposure time and subsequently dose control. All 45 focal spots were measured with an average value of 1.26 (±0.04) mm × 1.21 (±0.03) mm (equivalent to IEC 1,0). The x‐ray spectrum was found to be appropriately filtered based on sources used in existing rotary CT systems. A stable and reliable output of 0.04 mAs per emitter and a resulting dose of 0.015 mGy per projection were observed over several months of rigorous phantom imaging. Dose per projection was regulated by the ECS and measured with ±0.5% tolerance. Conclusions The CNT x‐ray source array was found to meet the requirements for the proposed stationary head CT scanner, with regard to FSS, beam quality, and dose precision. The remaining challenges are related to the overall system design of a nonrotating CT scanner with distributed sources. The next phase of the project will incorporate multiple CNT source arrays with multirow detectors in a proof‐of‐concept study and analysis of a fully functional s‐HCT system.

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“…The projection images were reconstructed using a model-based iterative reconstruction (IR) algorithm based on the open-source AIR Tools II and the ASTRA Toolbox [ 29 , 30 ]. The reconstruction process is implemented in the MATLAB R2020b programming environment on a PC with Intel Core i5-9600K CPU @ 3.70GHz and NVIDIA GeForce RTX 2070 graphic card.…”

Section: Methodsmentioning

confidence: 99%

Feasibility of dual-energy CBCT by spectral filtration of a dual-focus CNT x-ray source

Spronk

Luo

et al. 2022

PLoS ONE

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Cone beam computed tomography (CBCT) is now widely used in dentistry and growing areas of medical imaging. The presence of strong metal artifacts is however a major concern of using CBCT especially in dentistry due to the presence of highly attenuating dental restorations, fixed appliances, and implants. Virtual monoenergetic images (VMIs) synthesized from dual energy CT (DECT) datasets are known to reduce metal artifacts. Although several techniques exist for DECT imaging, they in general come with significantly increased equipment cost and not available in dental clinics. The objectives of this study were to investigate the feasibility of developing a low-cost dual energy CBCT (DE-CBCT) by retrofitting a regular CBCT scanner with a carbon nanotube (CNT) x-ray source with dual focal spots and corresponding low-energy (LE) and high-energy (HE) spectral filters. A testbed with a CNT field emission x-ray source (NuRay Technology, Chang Zhou, China), a flat panel detector (Teledyne, Waterloo, Canada), and a rotating object stage was used for this feasibility study. Two distinct polychromatic x-ray spectra with the mean photon energies of 66.7keV and 86.3keV were produced at a fixed 120kVp x-ray tube voltage by using Al+Au and Al+Sn foils as the respective LE and HE filters attached to the exist window of the x-ray source. The HE filter attenuated the x-ray photons more than the LE filter. The calculated post-object air kerma rate of the HE beam was 31.7% of the LE beam. An anthropomorphic head phantom (RANDO, Nuclear Associates, Hicksville, NY) with metal beads was imaged using the testbed and the images were reconstructed using an iterative volumetric CT reconstruction algorithm. The VMIs were synthesized using an image-domain basis materials decomposition method with energy ranging from 30 to 150keV. The results were compared to the reconstructed images from a single energy clinical dental CBCT scanner (CS9300, Carestream Dental, Atlanta, GA). A significant reduction of the metal artifacts was observed in the VMI images synthesized at high energies compared to those from the same object imaged by the clinical dental CBCT scanner. The ability of the CNT x-ray source to generate the output needed to compensate the reduction of photon flux due to attenuation from the spectral filters and to maintain the CT imaging time was evaluated. The results demonstrated the feasibility of DE-CBCT imaging using the proposed approach. Metal artifact reduction was achieved in VMIs synthesized. The x-ray output needed for the proposed DE-CBCT can be generated by a fixed-anode CNT x-ray source.

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Simulation and optimization of system configuration for the stationary head CT using CNT x-ray source array: reconstruction and quality evaluation

Cited by 8 publications

References 0 publications

Evaluation of the feasibility of a multisource CBCT for maxillofacial imaging

Evaluation of the feasibility of a multisource CBCT for maxillofacial imaging

Evaluation of carbon nanotube x‐ray source array for stationary head computed tomography

Feasibility of dual-energy CBCT by spectral filtration of a dual-focus CNT x-ray source

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