Twin robotic x-ray system for 2D radiographic and 3D cone-beam CT imaging

Fieselmann, Andreas; Steinbrener, Jan; Jerebko, Anna K.; Voigt, Johannes M.; Scholz, Rosemarie; Ritschl, Ludwig; Mertelmeier, Thomas

doi:10.1117/12.2212242

Cited by 18 publications

(23 citation statements)

References 6 publications

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“…In this preliminary study, all images were acquired with a twin‐robotic x‐ray prototype system based on a Multitom Rax (Siemens Healthcare GmbH, Forchheim, Germany). It is equipped with two ceiling‐mounted fully motorized robotic arms and can perform scans along defined trajectories . The x‐ray tube assembly (Optitop 150/40/80HC‐100) is operated in a pulsed mode with a selectable nominal focal spot size (IEC 60336) of either 0.6 (0.9 mm × 1.3 mm) or 1.0 (1.4 mm × 2.0 mm).…”

Section: Methodsmentioning

confidence: 99%

“…It is equipped with two ceiling-mounted fully motorized robotic arms and can perform scans along defined trajectories. 32 The x-ray tube assembly (Optitop 150/40/80HC-100) is operated in a pulsed mode with a selectable nominal focal spot size (IEC 60336) of either 0.6 (0.9 mm 9 1.3 mm) or 1.0 (1.4 mm 9 2.0 mm). The detector (Trixell Pixium 4343-F4) has a 2880 9 2880 pixel format with a pixel pitch of 0.148 mm and is operated in a 2 9 2 binning mode, hence the used pixel size within this work is 0.296 mm.…”

Section: A System Geometry and Image Acquisitionmentioning

confidence: 99%

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High‐speed slot‐scanning radiography using small‐angle tomosynthesis: Investigation of spatial resolution

et al. 2019

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Purpose This paper studies spatial resolution that is achievable with a fast slot‐scanning tomosynthesis approach for orthopedic examinations. Hereby, we use parallel scanning motion implemented in a twin robotic x‐ray system. Methods We have measured and analyzed the modulation transfer function (MTF) for various combinations of scanning speed, x‐ray tube voltage, pulse length, the nominal focal spot size as well as source‐to‐object distances. Moreover, we present a theoretical model which describes the system in terms of the MTF. The system was equipped with newly developed linear trajectory prototypes for slot scanning. The acquired images form the basis for a small‐angle tomosynthesis reconstruction. In total, three different scanning speeds (27, 14, 8 cm/s), pulse lengths (1, 2, 4 ms), tube voltages (80, 100, 120 kV), two nominal focal spot sizes (0.6, 1.0), and three source‐to‐object distances (950, 1050, 1150 mm) were investigated. To determine the resolution capabilities, we measured the MTF for the given parameter space. The results were then used to design a filter that yields a desired resolution in the reconstructed image. In addition, we also measured the noise power spectrum (NPS) to show the influence of the aforementioned filters on the noise distribution. Results We have shown that the presented model is in good agreement with the performed measurements. Scanning speed and pulse width have an impact on the MTF in the scanning direction. Up to a travel distance of 0.3 mm during an x‐ray pulse, an isotropic resolution can be achieved. Longer pulse width or higher scanning speed cause anisotropic resolution. Moreover, it is shown that none of the investigated parameters have an influence on the MTF perpendicular to the scanning direction (slot direction). The 10% MTF value ranges between 9 and 18 lp/cm in the scanning direction and about 18 lp/cm in slot direction. Tube voltage, nominal focal spot size as well as the source‐to‐object distance showed no major impact on the system MTF. In terms of the anisotropic resolution capabilities, we have shown that limiting the resolution in the slot direction to obtain isotropic resolution is possible yet at the cost of an inhomogeneous noise pattern. However, maintaining the resolution in slot direction will provide a better edge response and a more homogeneous noise texture at the cost of an inhomogeneous image resolution. Conclusions We have demonstrated the feasibility of the slot‐scanning technique using a twin‐robotic x‐ray system. Even the fastest scanning mode (27 cm/s) yields image resolution on a level that is sufficient for typical orthopedic examinations in terms of musculoskeletal (MSK) measurements. Moreover, it could be shown that the application of specifically designed target MTFs on two‐dimensional x‐ray images is feasible.

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Section: Methodsmentioning

confidence: 99%

Section: A System Geometry and Image Acquisitionmentioning

confidence: 99%

High‐speed slot‐scanning radiography using small‐angle tomosynthesis: Investigation of spatial resolution

et al. 2019

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“…21,22 Noncircular scan orbits of the system have been investigated for various imaging tasks such as CBCT of the weight-bearing spine 19,[23][24][25] and extremities, 26 and slot-scans for orthopedic imaging. 22,27 Here, we focus on two emerging diagnostic applications of robotic x-ray systemsweight-bearing CBCT of the lower extremity and the spine. In both cases, the flexibility in the positioning of the source and detector provided by the robotic platform is exploited to enable the scanning of upright subjects.…”

Section: Introductionmentioning

confidence: 99%

Cone‐beam imaging with tilted rotation axis: Method and performance evaluation

et al. 2020

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The recently introduced robotic x-ray systems provide the flexibility to acquire cone-beam computed tomography (CBCT) data using customized, application-specific source-detector trajectories. We exploit this capability to mitigate the effects of x-ray scatter and noise in CBCT imaging of weight-bearing foot and cervical spine (C-spine) using scan orbits with a tilted rotation axis. Methods: We used an advanced CBCT simulator implementing accurate models of x-ray scatter, primary attenuation, and noise to investigate the effects of the orbital tilt angle in upright foot and Cspine imaging. The system model was parameterized using a laboratory version of a three-dimensional (3D) robotic x-ray system (Multitom RAX, Siemens Healthineers). We considered a generalized tilted axis scan configuration, where the detector remained parallel to patient's long body axis during the acquisition, but the elevation of source and detector was changing. A modified Feldkamp-Davis-Kress (FDK) algorithm was developed for reconstruction in this configuration, which departs from the FDK assumption of a detector that is perpendicular to the scan plane. The simulated foot scans involved source-detector distance (SDD) of 1386 mm, orbital tilt angles ranging 10°to 40°, and 400 views at 1 mAs/view and 0.5°increment; the C-spine scans involved À25°to À45°tilt angles, SDD of 1090 mm, and 202 views at 1.3 mAs and 1°increment The imaging performance was assessed by projection-domain measurements of the scatter-to-primary ratio (SPR) and by reconstruction-domain measurements of contrast, noise and generalized contrast-to-noise ratio (gCNR, accounting for both image noise and background nonuniformity) of the metatarsals (foot imaging) and cervical vertebrae (spine imaging). The effects of scatter correction were also compared for horizontal and tilted scans using an ideal Monte Carlo (MC)-based scatter correction and a frame-byframe mean scatter correction. Results: The proposed modified FDK, involving projection resampling, mitigated streak artifacts caused by the misalignment between the filtering direction and the detector rows. For foot imaging (no grids), an optimized 20°tilted orbit reduced the maximum SPR from~1.5 in a horizontal scan to <0.5. The gCNR of the second metatarsal was enhanced twofold compared to a horizontal orbit. For the C-spine (with vertical grids), imaging with a tilted orbit avoided highly attenuating x-ray paths through the lower cervical vertebrae and shoulders. A À35°tilted orbit yielded improved image quality and visualization of the lower cervical spine: the SPR of lower cervical vertebrae was reduced from~10 (horizontal orbit) to <6 (tilted orbit), and the gCNR for C5-C7 increased by a factor of 2. Furthermore, tilted orbits showed potential benefits over horizontal orbits by enabling scatter correction with a simple frame-by-frame mean correction without substantial increase in noise-induced artifacts after the correction. Conclusions: Tilted scan trajectories, enabled by the emerging robotic x-ray system technolo...

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“…Several prototypes have already been built by various institutions, e.g. CEA [1], Fraunhofer [2], Siemens AG [3,4], RayScan Technologies [5], etc., for both medical and industrial purposes. Those systems can be roughly categorized as: robot aided conventional CT, robot-driven C-arm CT systems and twin robotics CT systems.…”

Section: Introductionmentioning

confidence: 99%

“…that provide 2x6 DoF. Another example is the Multitom Rax [3] from Siemens AG, which is equipped with two telescopic arms with 5 degrees of freedom (DoF) each.…”

Section: Introductionmentioning

confidence: 99%

Investigation of the impact of various robot properties on a twin Robot-CT system

Kang

Probst

Slaets

et al. 2020

Nondestructive Testing and Evaluation

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Robot-CT is drawing great attention for its potential to support highly flexible scan trajectories and various scan modes with a single system. However, the quality of CT reconstruction largely depends on accurate knowledge of the scan geometry, i.e. position and orientation of the source and the detector. This imposes major challenges on current serial industrial robots. In order to realistically assess the impact of various robot characteristics on the Robot-CT reconstruction quality and to facilitate the development of a dedicated calibration method, this paper elaborates on a set of simulations based on the performance evaluation of an ABB industrial robot. Simulation results reveal that: a) synchronous error motions of the twin robots can partially compensate for the robot errors; b) offline calibration is a possible way to implement high accuracy Robot-CT due to the excellent repeatability of current industrial robots; c) both robot positioning and orientation errors need to be compensated for to get a high quality reconstruction; d) compensating for only the relative error cannot improve the final reconstruction quality: absolute positioning and orientation errors need to be measured and compensated for. External sensors or radiograph based absolute geometry calibration are needed to improve the reconstruction quality.

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Twin robotic x-ray system for 2D radiographic and 3D cone-beam CT imaging

Cited by 18 publications

References 6 publications

High‐speed slot‐scanning radiography using small‐angle tomosynthesis: Investigation of spatial resolution

High‐speed slot‐scanning radiography using small‐angle tomosynthesis: Investigation of spatial resolution

Cone‐beam imaging with tilted rotation axis: Method and performance evaluation

Investigation of the impact of various robot properties on a twin Robot-CT system

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