X‐ray scattering in single‐ and dual‐source CT

Engel, Klaus; Herrmann, Christoph; Zeitler, Günter

doi:10.1118/1.2820901

Cited by 70 publications

(61 citation statements)

References 22 publications

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“…where 1 and 2 are the reconstructed attenuation coefficient values and a = D 2 / D. For inserts of small size and low contrast, the above equation can be simplified to 25,26 …”

Section: ͑1͒mentioning

confidence: 99%

Monte Carlo evaluation of scatter mitigation strategies in cone‐beam CT

Lazos

Williamson

2010

Medical Physics

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Purpose: To investigate the efficacy of two widely used scatter mitigation methods: antiscatter grids ͑ASGs͒ and beam modulating with bowtie filters ͑BTFs͒, in combination with subtractive scatter correction or zeroth order normalization phantom calibration, for improving image noise, contrast, contrast-to-noise ratio ͑CNR͒, and image uniformity for on-board cone-beam CT ͑CBCT͒ imaging systems used for image-guided radiation therapy. Methods: PTRAN Monte Carlo CBCT x-ray projections of head and pelvic phantoms were calculated for combinations of beam-modulation and scatter rejection methods and images were reconstructed by in-house developed software. In addition, a simple one-dimensional analytic model was developed to predict scatter-to-primary ratio ͑SPR͒ and CNR as a function of cylindrical phantom thickness, ASG transmission, and beam modulation with bow-tie filters. Results: ASGs were found to have slightly negative or no effect on head phantom image CNR and to modestly improve CNR ͑10%-20%͒ in pelvic phantom images. However, scatter subtraction and norm-phantom calibration perform better when applied on data acquired with ASGs. Scatter subtraction improves CT number accuracy, but increases noise, and in high SPR/low primary-photon transmission scenarios can dramatically reduce CNR and introduce streaking artifacts. The BTF is found to reduce SPR and image noise, resulting in a better trade-off between CNR and imaging dose, but introduces a circular band artifact. Conclusions: Our study shows that ASGs have a modest positive impact in pelvic scans and negative in head scans, scatter subtraction improves the HU accuracy but reduces CNR, while BTF has a clearly positive effect.

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“…where 1 and 2 are the reconstructed attenuation coefficient values and a = D 2 / D. For inserts of small size and low contrast, the above equation can be simplified to 25,26 …”

Section: ͑1͒mentioning

confidence: 99%

Monte Carlo evaluation of scatter mitigation strategies in cone‐beam CT

Lazos

Williamson

2010

Medical Physics

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“…The bigger the irradiated tissue volume, the more scatter artifacts can be observed. The scattered radiation also reduces the signal-to-noise ratio (SNR) and deteriorates image contrast [5].…”

Section: Metal Artifacts Observed In Computed Tomographymentioning

confidence: 99%

CT and MRI Techniques for Imaging Around Orthopedic Hardware

Duong

Sutter

Skornitzke

et al. 2017

Fortschr Röntgenstr

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ZUSAMMENFASSUNGOrthopädische Implantate verringern die Bildqualität in der Schnittbildgebung. Bei steigendem Einsatz von orthopädi-schen Implantaten in einer alternden Bevölkerung ist eine Metallartefaktreduktion von zunehmender Bedeutung. Im folgenden Review möchten wir einen Überblick über die wesentlichen Artefakte in der Computertomografie und Magnetresonanztomografie sowie die neuesten Standards zur Verbesserung der Bildqualität geben. Alle Schritte der Bildakquisition von Gerätewahl über Scanvorbereitungen und -parameter bis hin zur Bildverarbeitung beeinflussen das Ausmaß der Metallartefakte. Technische Fortschritte wie die Dual-energy-Computertomografie mit der Option der Virtuellen monochromatischen Bildgebung sowie neue Implantatmaterialien bieten weitere Möglichkeiten der Metallartefaktreduktion in CT und MRT. Dezidierte MetallartefaktSequenzen beinhalten Algorithmen zur Artefaktreduktion und zur Verbesserung der Bildqualität des umgebenden Gewebes und sind essenzielle Werkzeuge in der orthopä-dischen Bildgebung zur frühzeitigen Detektion von postoperativen Komplikationen. ABSTR AC TOrthopedic hardware impairs image quality in cross-sectional imaging. With an increasing number of orthopedic implants in an aging population, the need to mitigate metal artifacts in computed tomography and magnetic resonance imaging is becoming increasingly relevant. This review provides an overview of the major artifacts in CT and MRI and state-ofthe-art solutions to improve image quality. All steps of image acquisition from device selection, scan preparations and parameters to image post-processing influence the magnitude of metal artifacts. Technological advances like dual-energy CT with the possibility of virtual monochromatic imaging (VMI) and new materials offer opportunities to further reduce artifacts in CT and MRI. Dedicated metal artifact reduction sequences contain algorithms to reduce artifacts and improve imaging of surrounding tissue and are essential tools in orthopedic imaging to detect postoperative complications in early stages.

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“…With DCBCT, the detector may detect the photons scattered by the object, resulting in degradation of the image quality 16, 17. Engel et al 18 used a Monte Carlo method to simulate photon scatter in the SCBCT and DCBCT. With SCBCT, the image uniformity obtained with tube 2 was worse than that of tube 1, which implies that the two SCBCT systems have slightly different detector responses.…”

Section: Discussionmentioning

confidence: 99%

Image quality and absorbed dose comparison of single‐ and dual‐source cone‐beam computed tomography

Miura

Ozawa

Okazue³

et al. 2018

J Applied Clin Med Phys

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PurposeDual‐source cone‐beam computed tomography (DCBCT) is currently available in the Vero4DRT image‐guided radiotherapy system. We evaluated the image quality and absorbed dose for DCBCT and compared the values with those for single‐source CBCT (SCBCT).MethodsImage uniformity, Hounsfield unit (HU) linearity, image contrast, and spatial resolution were evaluated using a Catphan phantom. The rotation angle for acquiring SCBCT and DCBCT images is 215° and 115°, respectively. The image uniformity was calculated using measurements obtained at the center and four peripheral positions. The HUs of seven materials inserted into the phantom were measured to evaluate HU linearity and image contrast. The Catphan phantom was scanned with a conventional CT scanner to measure the reference HU for each material. The spatial resolution was calculated using high‐resolution pattern modules. Image quality was analyzed using ImageJ software ver. 1.49. The absorbed dose was measured using a 0.6‐cm3 ionization chamber with a 16‐cm‐diameter cylindrical phantom, at the center and four peripheral positions of the phantom, and calculated using weighted cone‐beam CT dose index (CBCTDI w).ResultsCompared with that of SCBCT, the image uniformity of DCBCT was slightly reduced. A strong linear correlation existed between the measured HU for DCBCT and the reference HU, although the linear regression slope was different from that of the reference HU. DCBCT had poorer image contrast than did SCBCT, particularly with a high‐contrast material. There was no significant difference between the spatial resolutions of SCBCT and DCBCT. The absorbed dose for DCBCT was higher than that for SCBCT, because in DCBCT, the two x‐ray projections overlap between 45° and 70°.ConclusionsWe found that the image quality was poorer and the absorbed dose was higher for DCBCT than for SCBCT in the Vero4DRT.

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X‐ray scattering in single‐ and dual‐source CT

Cited by 70 publications

References 22 publications

Monte Carlo evaluation of scatter mitigation strategies in cone‐beam CT

Monte Carlo evaluation of scatter mitigation strategies in cone‐beam CT

CT and MRI Techniques for Imaging Around Orthopedic Hardware

Image quality and absorbed dose comparison of single‐ and dual‐source cone‐beam computed tomography

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