Geometric calibration for a dual tube/detector micro‐CT system

Johnston, S. M.; Johnson, G. Allan; Badea, Cristian T.

doi:10.1118/1.2900000

Cited by 56 publications

(56 citation statements)

References 29 publications

(33 reference statements)

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“…Effects of yshifts are not clearly visible either. Many methods for the estimation of geometrical parameters of cone-beam scanners have been proposed since 1990 [20, [26][27][28][29][30]. These techniques have generally fallen into two categories: those based on iterative nonlinear optimization [26,27] and those based on the direct solution of geometric equations [20,28,29,31].…”

Section: Misalignment Correction In Single Bed Acquisitionsmentioning

confidence: 99%

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Software architecture for multi-bed FDK-based reconstruction in X-ray CT scanners

Abella

Vaquero

Sisniega

et al. 2012

Computer Methods and Programs in Biomedicine

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Cone-beam t r a c tMost small-animal X-ray computed tomography (CT) scanners are based on cone-beam geometry with a flat-panel detector orbiting in a circular trajectory. Image reconstruction in these systems is usually performed by approximate methods based on the algorithm proposed by Feldkamp et al. (FDK). Besides the implementation of the reconstruction algorithm itself, in order to design a real system it is necessary to take into account numerous issues so as to obtain the best quality images from the acquired data. This work presents a comprehensive, novel software architecture for small-animal CT scanners based on cone-beam geometry with circular scanning trajectory. The proposed architecture covers all the steps from the system calibration to the volume reconstruction and conversion into Hounsfield units. It includes an efficient implementation of an FDK-based reconstruction algorithm that takes advantage of system symmetries and allows for parallel reconstruction using a multiprocessor computer. Strategies for calibration and artifact correction are discussed to justify the strategies adopted. New procedures for multi-bed misalignment, beam-hardening, and Housfield units calibration are proposed. Experiments with phantoms and real data showed the suitability of the proposed software architecture for an X-ray small animal CT based on cone-beam geometry. IntroductionMany small animal X-ray computed tomography (CT) scanners are based on cone-beam geometry with a flat-panel detector orbiting in a circular trajectory [1][2][3][4]. This configuration presents advantages over other alternatives used in clinical and preclinical applications: reduction of acquisition time, large axial field of view (FOV) without geometrical distortions, and optimization of radiated dose [5]. proposed by Feldkamp et al. (FDK) [6] are still widely used for solving the 3D reconstruction task because of their straightforward implementation and computational efficiency [4]. Almost every aspect of the reconstruction process has been studied: there is literature on algorithm variations for different trajectories [7,8], optimizations using graphic processing units (GPUs) [9][10][11][12][13][14][15], strategies to reduce cone beam artifacts [16,17], study of consistency conditions [18], optimization of the back-projection step [19], etc. However, in a real practical system, the implementation of a reconstruction algorithm core such as FDK is just an initial step of the process, and there 1

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Section: Misalignment Correction In Single Bed Acquisitionsmentioning

confidence: 99%

“…In [27][28][29][30], either the design of this calibration object or its positioning, or both, required very high precision. Contrarily, in [20,32] the authors propose methods that avoid strict requirements on the object shape and positioning.…”

Section: Misalignment Correction In Single Bed Acquisitionsmentioning

confidence: 99%

Software architecture for multi-bed FDK-based reconstruction in X-ray CT scanners

Abella

Vaquero

Sisniega

et al. 2012

Computer Methods and Programs in Biomedicine

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“…We have recently introduced a geometric calibration method for the dual tube/detector system, which allows combinations of projections from the two detectors in a single reconstruction for faster dynamic scanning. 17 Due to our dual imaging chains, projection data have to be acquired only over a 90°+ fan angle, rotation. The fan angle for our system is 6.27°.…”

Section: Iia Imaging Systemmentioning

confidence: 99%

Lung perfusion imaging in small animals using 4D micro‐CT at heartbeat temporal resolution

et al. 2009

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Purpose: Quantitative in vivo imaging of lung perfusion in rodents can provide critical information for preclinical studies. However, the combined challenges of high temporal and spatial resolution have made routine quantitative perfusion imaging difficult in small animals. The purpose of this work is to demonstrate 4D micro-CT for perfusion imaging in rodents at heartbeat temporal resolution and isotropic spatial resolution. Methods: We have recently developed a dual tube/detector micro-CT scanner that is well suited to capture first pass kinetics of a bolus of contrast agent used to compute perfusion information. Our approach is based on the paradigm that similar time density curves can be reproduced in a number of consecutive, small volume injections of iodinated contrast agent at a series of different angles. This reproducibility is ensured by the high-level integration of the imaging components of our system with a microinjector, a mechanical ventilator, and monitoring applications. Sampling is controlled through a biological pulse sequence implemented in LABVIEW. Image reconstruction is based on a simultaneous algebraic reconstruction technique implemented on a graphic processor unit. The capabilities of 4D micro-CT imaging are demonstrated in studies on lung perfusion in rats. Results: We report 4D micro-CT imaging in the rat lung with a heartbeat temporal resolution ͑approximately 150 ms͒ and isotropic 3D reconstruction with a voxel size of 88 m based on sampling using 16 injections of 50 L each. The total volume of contrast agent injected during the experiments ͑0.8 mL͒ was less than 10% of the total blood volume in a rat. This volume was not injected in a single bolus, but in multiple injections separated by at least 2 min interval to allow for clearance and adaptation. We assessed the reproducibility of the time density curves with multiple injections and found that these are very similar. The average time density curves for the first eight and last eight injections are slightly different, i.e., for the last eight injections, both the maximum of the average time density curves and its area under the curve are decreased by 3.8% and 7.2%, respectively, relative to the average time density curves based on the first eight injections. The radiation dose associated with our 4D micro-CT imaging is 0.16 Gy and is therefore in the range of a typical micro-CT dose. Conclusions: 4D micro-CT-based perfusion imaging demonstrated here has immediate application in a wide range of preclinical studies such as tumor perfusion, angiogenesis, and renal function. Although our imaging system is in many ways unique, we believe that our approach based on the multiple injection paradigm can be used with the newly developed flat-panel slip-ring-based micro-CT to increase their temporal resolution in dynamic perfusion studies.

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“…This involves a geometric calibration procedure presented in [7] . In essence, the geometric calibration is achieved by scanning a calibration phantom with metallic beads and computing the projections matrices required by the reconstruction.…”

Section: Geometric Calibrationmentioning

confidence: 99%

A dual micro-CT system for small animal imaging

et al. 2008

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Micro-CT is a non-invasive imaging modality usually used to assess morphology in small animals. In our previous work, we have demonstrated that functional micro-CT imaging is also possible. This paper describes a dual micro-CT system with two fixed x-ray/detectors developed to address such challenging tasks as cardiac or perfusion studies in small animals. A two-tube/detector system ensures simultaneous acquisition of two projections, thus reducing scanning time and the number of contrast injections in perfusion studies by a factor of two. The system is integrated with software developed in-house for cardio-respiratory monitoring and gating. The sampling geometry was optimized for 88 microns in such a way that the geometric blur of the focal spot matches the Nyquist sample at the detector. A geometric calibration procedure allows one to combine projection data from the two chains into a single reconstructed volume. Image quality was measured in terms of spatial resolution, uniformity, noise, and linearity. The modulation transfer function (MTF) at 10% is 3.4 lp/mm for single detector reconstructions and 2.3 lp/mm for dual tube/detector reconstructions. We attribute this loss in spatial resolution to the compounding of slight errors in the separate single chain calibrations. The dual micro-CT system is currently used in studies for morphological and functional imaging of both rats and mice.

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Geometric calibration for a dual tube/detector micro‐CT system

Cited by 56 publications

References 29 publications

Software architecture for multi-bed FDK-based reconstruction in X-ray CT scanners

Software architecture for multi-bed FDK-based reconstruction in X-ray CT scanners

Lung perfusion imaging in small animals using 4D micro‐CT at heartbeat temporal resolution

A dual micro-CT system for small animal imaging

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