Measurement of temperature induced X-ray tube transmission target displacements for dimensional computed tomography

Computed tomography systems are increasingly used for dimensional metrology. Accurate CT machine geometry and temperatures close to 20 °C are crucial for dimensional measurements. Usually, considerable thermal loads are imposed onto CT systems by the X-ray source and the detector that dissipate heat in the order of 100 W. Because temperature variations and gradients induce deformations on the machine geometry, it is crucial to characterise and control such influences. Here, a homebuilt water cooling system for a flat-panel X-ray detector was characterised for heat dissipation into the CT system, positional and angular drift, and pixel grey value stability.

Section: Discussionmentioning

confidence: 99%

Section: Position Variationsmentioning

confidence: 99%

CT machine geometry changes under thermal load

Bircher¹,

Meli²,

Küng³

et al. 2019

“…Another use case for reconstruction methods based on projection matrices is the compensation of known geometrical drifts during the scan. Tracking systems for CT components are currently investigated [22] and would provide useful information to be incorporated into the reconstruction process.…”

Section: Tools For Arbitrary Cone-beam Ct Geometries and Trajectoriesmentioning

confidence: 99%

The CTSimU software toolbox for CT-related image processing and quality assessment

Plotzki¹,

Hartlaub²,

Oliveira³

et al. 2022

A software toolbox is introduced that addresses several needs common to computed tomography (CT). Built for the WIPANO CTSimU project [1] to serve as the reference implementation for its image processing and evaluation tasks, it provides a Python 3 interface that is adaptable to many conceivable applications. Foremost, the toolbox features a pipeline architecture for sequential 2D image processing tasks, such as flat field corrections and image binning, and enables the user to create their own processing modules. Beyond that, it provides means to measure line profiles and image quality assessment algorithms to calculate modulation transfer functions (MTF) or to determine the interpolated basic spatial resolution (iSRb) using a duplex wire image [2]. It can also be used to calculate projection matrices for the reconstruction of scans with arbitrary industrial CT geometries and trajectories. The CTSimU project defined a framework of projection- and volume-based test scenarios [3] for the qualification of radiographic simulation software towards its use in dimensional metrology. The toolbox implements the necessary evaluation routines and generates reports for all projection-based tests.

“…They can be used for estimation of local effects, e.g. finite element modelling of deformations in the X-ray tube [20], or implemented for the full XCT geometry combined with a computational fluid dynamics (CFD) model. Establishing traceability could be achieved through comparisons to reference measurements [20].…”

Section: Numerical Simulationsmentioning

confidence: 99%

Traceable determination of non-static XCT machine geometry: New developments and case studies

Bircher¹,

Meli²,

Küng³

et al. 2022

It is fundamental to determine the machine geometry accurately for dimensional X-ray computed tomography (XCT) measurements. When performing high-accuracy scans, compensation of a non-static geometry, e.g. due to rotary axis errors or drift, might become necessary. Here we provide an overview of methods to determine and account for such deviations on a per projection basis. They include characterisation of stage error motions, in situ geometry measurements, numerical simulations, and reconstruction-based optimization relying on image quality metrics and will be discussed in terms of their metrological performance. Since a radiographic calibration is always required to provide an initial absolute geometry, this method will be presented as well. The improvements of the XCT geometry correction methods are presented by means of case studies. The methods can be applied individually or in combination and are intended to provide a toolbox for XCT geometry compensation.