Ultrasound computer tomography: Difference between revisions
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== Description == |
== Description == |
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''Ultrasound computer tomographs'' use [[ultrasound]] [[wave]]s for creating images. In the first measurement step a defined ultrasound wave is generated with typically [[Piezoelectric]] [[ultrasound transducer]]s, transmitted in direction of the measurement object and received with other or the same ultrasound transducers. While traversing and interacting with the object the ultrasound wave is changed by the object and carries now information about the object. After being recorded the information from the modulated waves can be extracted and used to create an image of the object in a second step. Unlike [[X-ray]] or other physical properties, who provide typically one image information, ultrasound provides multiple information of the object: the [[attenuation]] the wave's [[sound pressure]] experiences indicate on the object's [[attenuation coefficient]], the [[time-of-flight]] of the wave gives [[speed of sound]] information, and the received reflection distribution indicates on the reflectivity properties of the object (e.g. [[refraction index]], surface morphology, etc). Unlike conventional ultrasound [[sonography]] most USCT systems don't use a [[phased array]] for [[beamforming]] but unfocused spherical waves for imaging. Most USCT systems aiming for 3D-imaging, either by synthesizing ("stacking") 2D images or by full 3D aperture setups. |
''Ultrasound computer tomographs'' use [[ultrasound]] [[wave]]s for creating images. In the first measurement step a defined ultrasound wave is generated with typically [[Piezoelectric]] [[ultrasound transducer]]s, transmitted in direction of the measurement object and received with other or the same ultrasound transducers. While traversing and interacting with the object the ultrasound wave is changed by the object and carries now information about the object. After being recorded the information from the modulated waves can be extracted and used to create an image of the object in a second step. Unlike [[X-ray]] or other physical properties, who provide typically one image information, ultrasound provides multiple information of the object: the [[attenuation]] the wave's [[sound pressure]] experiences indicate on the object's [[attenuation coefficient]], the [[time-of-flight]] of the wave gives [[speed of sound]] information, and the received reflection distribution indicates on the reflectivity properties of the object (e.g. [[refraction index]], surface morphology, etc). Unlike conventional ultrasound [[sonography]] most USCT systems don't use a [[phased array]] for [[beamforming]] but unfocused spherical waves for imaging. Most USCT systems aiming for 3D-imaging, either by synthesizing ("stacking") 2D images or by full 3D aperture setups. Another aim is [[Quantitative property|quantitative]] [[imaging]] instead of only [[Qualitative data|qualitative]] imaging. |
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The idea of ''Ultrasound computer tomography'' goes back to the 1950s with analogue compounding setups,<ref>[http://www.ob-ultrasound.net/dussik_apparatus.html Acta Neurochirurgica, Springer Verlag Wien, Volume 2, Numbers 3-4, September 1952, 379 - 401.]</ref><ref>{{cite paper|year=1954 |authors=Holmes, J., Howry, D., Posakony, G., and Cushman, C.|title=The ultrasonic visualization of soft tissue structures in the human body.|work=Transactions of the American Clinical and Climatological Association |issue=66 |pages=208}}</ref><ref>[http://people.csail.mit.edu/wachinger/articles/Thesis.pdf Ultrasound Mosaicing and Motion Modeling - Applications in Medical Image Registration] Christian Wachinger, PhD Thesis, [[TU München]] (2011)</ref> in the mid 1970s the first "computed" USCT systems were built up, utilizing digital technology.<ref name="kak&slaney_hist">{{Cite book|title = Principles of Computerized Tomographic Imaging |authors=Avinash C. Kak, Malcolm Slaney |publisher=IEEE Press. Institute for Electrical and Electronic Engineers. |year =1988 |isbn = 978-0898714944|location = |pages = |url = https://engineering.purdue.edu/~malcolm/pct/CTI_Ch04.3.pdf |quote=''The first such tomograms were made by Greenleaf et al. [Gre74], [Gre75], followed by Carson et al. [Car76], Jackowatz and Kak [Jak76], and Glover and Sharp [Glo77].''|chapter=4}}</ref> The "computer" in the USCT concept indicates the heavy reliance on computational intensive advanced digital [[signal processing]], [[image reconstruction]] and [[image processing]] [[algorithm]]s for imaging. Successfully realization of USCT systems in the last decades was possible through the continuously growing availability of [[computing power]] and [[data bandwidth]] provided by the [[digital revolution]]. |
The idea of ''Ultrasound computer tomography'' goes back to the 1950s with analogue compounding setups,<ref>[http://www.ob-ultrasound.net/dussik_apparatus.html Acta Neurochirurgica, Springer Verlag Wien, Volume 2, Numbers 3-4, September 1952, 379 - 401.]</ref><ref>{{cite paper|year=1954 |authors=Holmes, J., Howry, D., Posakony, G., and Cushman, C. |title=The ultrasonic visualization of soft tissue structures in the human body.|work=Transactions of the American Clinical and Climatological Association |issue=66 |pages=208}}</ref><ref>[http://people.csail.mit.edu/wachinger/articles/Thesis.pdf Ultrasound Mosaicing and Motion Modeling - Applications in Medical Image Registration] Christian Wachinger, PhD Thesis, [[TU München]] (2011)</ref> in the mid 1970s the first "computed" USCT systems were built up, utilizing digital technology.<ref name="kak&slaney_hist">{{Cite book|title = Principles of Computerized Tomographic Imaging |authors=Avinash C. Kak, Malcolm Slaney |publisher=IEEE Press. Institute for Electrical and Electronic Engineers. |year =1988 |isbn = 978-0898714944|location = |pages = |url = https://engineering.purdue.edu/~malcolm/pct/CTI_Ch04.3.pdf |quote=''The first such tomograms were made by Greenleaf et al. [Gre74], [Gre75], followed by Carson et al. [Car76], Jackowatz and Kak [Jak76], and Glover and Sharp [Glo77].''|chapter=4}}</ref> The "computer" in the USCT concept indicates the heavy reliance on computational intensive advanced digital [[signal processing]], [[image reconstruction]] and [[image processing]] [[algorithm]]s for imaging. Successfully realization of USCT systems in the last decades was possible through the continuously growing availability of [[computing power]] and [[data bandwidth]] provided by the [[digital revolution]]. |
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== Setup == |
== Setup == |
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USCT systems designed for [[medical imaging]] of [[soft tissue]] typically aim for [[Resolution|resolution]] in order of [[centimeters]] to [[millimeter]]s and require therefore ultrasound waves in the order of [[mega]]-[[hertz]] [[frequency]]. This requires typically water as low-attenuating [[Transmission medium|transmission medium]] between ultrasound transducers and object to retain suitable sound pressures.<ref name="kak&slaney">{{Cite book|title = Principles of Computerized Tomographic Imaging |authors=Avinash C. Kak, Malcolm Slaney |publisher=IEEE Press. Institute for Electrical and Electronic Engineers. |year =1988 |isbn = 978-0898714944 |location = |pages = |url = https://engineering.purdue.edu/~malcolm/pct/CTI_Ch04.3.pdf |chapter=4}}</ref> |
USCT systems designed for [[medical imaging]] of [[soft tissue]] typically aim for [[Resolution|resolution]] in order of [[centimeters]] to [[millimeter]]s and require therefore ultrasound waves in the order of [[mega]]-[[hertz]] [[frequency]]. This requires typically water as low-attenuating [[Transmission medium|transmission medium]] between ultrasound transducers and object to retain suitable sound pressures.<ref name="kak&slaney">{{Cite book|title = Principles of Computerized Tomographic Imaging |authors=Avinash C. Kak, Malcolm Slaney |publisher=IEEE Press. Institute for Electrical and Electronic Engineers. |year =1988 |isbn = 978-0898714944 |location = |pages = |url = https://engineering.purdue.edu/~malcolm/pct/CTI_Ch04.3.pdf |chapter=4}}</ref> |
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USCT systems share with the common [[Tomography]] the fundamental architectural similarity that the [[aperture]], the active imaging elements, surround the object. For the distribution of ultrasound transducers around the measurement object, forming the [[aperture]], multiple design approaches exist. There exist mono-, bi- and multistatic setups of transducer configurations. Common are 1D- or 2D- linear arrays of ultrasound transducers acting as emitters on one side of the object, on the opposing side of the object a similar array acting as receiver is placed, forming a [[parallel]] setup. Sometimes accompanied with the additional ability to be moved to gather more information from additional angles. While cost efficient to build the main disadvantage of such an setup is the limited ability (or inability) of gathering reflectivity information, as such an aperture is limited to only transmission information. Another aperture approach is a ring setup of transducers,<ref>[http://proceedings.spiedigitallibrary.org/proceeding.aspx?articleid=2209818 Transducer elements position calibration in a ring array USCT system] Satoshi Tamano ; Takashi Azuma ; Haruka Imoto ; Shu Takagi ; Shin-ichiro Umemura ; Yoichiro Matsumoto, Proc. SPIE 9419, Medical Imaging 2015: Ultrasonic Imaging and Tomography, 94190P (March 17, 2015); doi:10.1117/12.2082323</ref> sometimes with the degree of freedom of lifting, to be able to synthesize 3d images by gathering additional information over the height. Full 3D setups, with no inherent need for aperture movements, exist in form of apertures formed by semi-spherical distributed transducers. While the most expensive setup they offer the advantage of nearly-uniform data |
USCT systems share with the common [[Tomography]] the fundamental architectural similarity that the [[aperture]], the active imaging elements, surround the object. For the distribution of ultrasound transducers around the measurement object, forming the [[aperture]], multiple design approaches exist. There exist mono-, bi- and multistatic setups of transducer configurations. Common are 1D- or 2D- linear arrays of ultrasound transducers acting as emitters on one side of the object, on the opposing side of the object a similar array acting as receiver is placed, forming a [[parallel]] setup. Sometimes accompanied with the additional ability to be moved to gather more information from additional angles. While cost efficient to build the main disadvantage of such an setup is the limited ability (or inability) of gathering reflectivity information, as such an aperture is limited to only transmission information. Another aperture approach is a ring setup of transducers,<ref>[http://proceedings.spiedigitallibrary.org/proceeding.aspx?articleid=2209818 Transducer elements position calibration in a ring array USCT system] Satoshi Tamano ; Takashi Azuma ; Haruka Imoto ; Shu Takagi ; Shin-ichiro Umemura ; Yoichiro Matsumoto, Proc. SPIE 9419, Medical Imaging 2015: Ultrasonic Imaging and Tomography, 94190P (March 17, 2015); doi:10.1117/12.2082323</ref> sometimes with the degree of freedom of lifting, to be able to synthesize 3d images by gathering additional information over the height. Full 3D setups, with no inherent need for aperture movements, exist in form of apertures formed by semi-spherical distributed transducers. While the most expensive setup they offer the advantage of nearly-uniform data, gathered from many directions. Also, they are fast in data taking as they don't require time-costly mechanical movements. |
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== Imaging methods == |
== Imaging methods == |
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For USCT systems, classical [[radon transform|inverse radon transform]] and [[fourier slice theorem]] based methods are in use for transmission information based imaging, [[Algebraic Reconstruction Technique|ART]]-based approaches are advanced alternatives also in use. For high resolution and [[speckle noise]] reduced reflectivity imaging Synthetic Aperture Focusing Techniques (SAFT), similar to [[radar]]'s [[Synthetic aperture radar|SAR]] and [[sonar]]'s [[Synthetic aperture sonar|SAS]], are widely used. Iterative [[wave equation]] inversion approaches as imaging method are under academic research, but usage for real world applications is due to computational and memory burden still a challenge. |
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== Usage and Application == |
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Many USCT systems are designed for soft tissue imaging and for [[breast cancer]] detection specifically. As ultrasound based method, USCT is a harmless and risk-free imaging method, suitable for periodical [[Breast cancer screening|screening]]. As USCT setups are fixed or motor moved without direct contact with the breast the reproduction of images is easier as the common, manually guided methods which rely on the examiners performance and experience. In comparison with conventional screening methods as [[mammography]], USCT setups offer potentially an increased [[Specificity (statistics)|specificity]], as multiple breast cancer characteristic properties are imaged at the same time: speed-of-sound, attenuation and morphology.<ref name="greenleaf">{{cite paper|url=http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=4121179&tag=1 |title=Clinical Imaging with Transmissive Ultrasonic Computerized Tomography |authors=JAMES F. GREENLEAF, ROBERT C. BAHN |date=1981 |journal=IEEE Transactions on Biomedical Engineering. |issue=28, 2|pages=177-185}}</ref> |
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== See also == |
== See also == |
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Revision as of 00:57, 10 November 2015
Ultrasound computer tomography (USCT), sometimes also Ultrasound computed tomography, Ultrasound computerized tomography[1] or just Ultrasound tomography,[2] is a form of medical ultrasound tomography involving ultrasound as physical wave used for imaging. It is mostly in use for soft tissue medical imaging, especially breast imaging.[2][3][4]
Description
Ultrasound computer tomographs use ultrasound waves for creating images. In the first measurement step a defined ultrasound wave is generated with typically Piezoelectric ultrasound transducers, transmitted in direction of the measurement object and received with other or the same ultrasound transducers. While traversing and interacting with the object the ultrasound wave is changed by the object and carries now information about the object. After being recorded the information from the modulated waves can be extracted and used to create an image of the object in a second step. Unlike X-ray or other physical properties, who provide typically one image information, ultrasound provides multiple information of the object: the attenuation the wave's sound pressure experiences indicate on the object's attenuation coefficient, the time-of-flight of the wave gives speed of sound information, and the received reflection distribution indicates on the reflectivity properties of the object (e.g. refraction index, surface morphology, etc). Unlike conventional ultrasound sonography most USCT systems don't use a phased array for beamforming but unfocused spherical waves for imaging. Most USCT systems aiming for 3D-imaging, either by synthesizing ("stacking") 2D images or by full 3D aperture setups. Another aim is quantitative imaging instead of only qualitative imaging.
The idea of Ultrasound computer tomography goes back to the 1950s with analogue compounding setups,[5][6][7] in the mid 1970s the first "computed" USCT systems were built up, utilizing digital technology.[8] The "computer" in the USCT concept indicates the heavy reliance on computational intensive advanced digital signal processing, image reconstruction and image processing algorithms for imaging. Successfully realization of USCT systems in the last decades was possible through the continuously growing availability of computing power and data bandwidth provided by the digital revolution.
Setup
USCT systems designed for medical imaging of soft tissue typically aim for resolution in order of centimeters to millimeters and require therefore ultrasound waves in the order of mega-hertz frequency. This requires typically water as low-attenuating transmission medium between ultrasound transducers and object to retain suitable sound pressures.[1]
USCT systems share with the common Tomography the fundamental architectural similarity that the aperture, the active imaging elements, surround the object. For the distribution of ultrasound transducers around the measurement object, forming the aperture, multiple design approaches exist. There exist mono-, bi- and multistatic setups of transducer configurations. Common are 1D- or 2D- linear arrays of ultrasound transducers acting as emitters on one side of the object, on the opposing side of the object a similar array acting as receiver is placed, forming a parallel setup. Sometimes accompanied with the additional ability to be moved to gather more information from additional angles. While cost efficient to build the main disadvantage of such an setup is the limited ability (or inability) of gathering reflectivity information, as such an aperture is limited to only transmission information. Another aperture approach is a ring setup of transducers,[9] sometimes with the degree of freedom of lifting, to be able to synthesize 3d images by gathering additional information over the height. Full 3D setups, with no inherent need for aperture movements, exist in form of apertures formed by semi-spherical distributed transducers. While the most expensive setup they offer the advantage of nearly-uniform data, gathered from many directions. Also, they are fast in data taking as they don't require time-costly mechanical movements.
Imaging methods
For USCT systems, classical inverse radon transform and fourier slice theorem based methods are in use for transmission information based imaging, ART-based approaches are advanced alternatives also in use. For high resolution and speckle noise reduced reflectivity imaging Synthetic Aperture Focusing Techniques (SAFT), similar to radar's SAR and sonar's SAS, are widely used. Iterative wave equation inversion approaches as imaging method are under academic research, but usage for real world applications is due to computational and memory burden still a challenge.
Usage and Application
Many USCT systems are designed for soft tissue imaging and for breast cancer detection specifically. As ultrasound based method, USCT is a harmless and risk-free imaging method, suitable for periodical screening. As USCT setups are fixed or motor moved without direct contact with the breast the reproduction of images is easier as the common, manually guided methods which rely on the examiners performance and experience. In comparison with conventional screening methods as mammography, USCT setups offer potentially an increased specificity, as multiple breast cancer characteristic properties are imaged at the same time: speed-of-sound, attenuation and morphology.[10]
See also
- Medical ultrasound
- Tomography
- Ultrasound transmission tomography
- Ultrasound-modulated optical tomography
References
- ^ a b "4". Principles of Computerized Tomographic Imaging (PDF). IEEE Press. Institute for Electrical and Electronic Engineers. 1988. ISBN 978-0898714944.
{{cite book}}: Unknown parameter|authors=ignored (help) - ^ a b "Clinical breast imaging with ultrasound tomography: A description of the SoftVue system". The Journal of the Acoustical Society of America (135(4)): 2155. 2014-04-01. doi:10.1121/1.4876990.
{{cite journal}}: Unknown parameter|authors=ignored (help) - ^ "Quantitative volumetric breast imaging with 3D inverse scatter computed tomography". Engineering in Medicine and Biology Magazine. IEEE. 2012-01-01. doi:10.1109/EMBC.2012.6346129.
{{cite journal}}: Unknown parameter|authors=ignored (help) - ^ "3D Ultrasound Computertomography of the Breast (3D USCT): a new era". European Journal of Radiology. 2012.
{{cite journal}}: Cite journal requires|journal=(help); Unknown parameter|authors=ignored (help) - ^ Acta Neurochirurgica, Springer Verlag Wien, Volume 2, Numbers 3-4, September 1952, 379 - 401.
- ^ "The ultrasonic visualization of soft tissue structures in the human body". Transactions of the American Clinical and Climatological Association (66): 208. 1954.
{{cite journal}}: Unknown parameter|authors=ignored (help) - ^ Ultrasound Mosaicing and Motion Modeling - Applications in Medical Image Registration Christian Wachinger, PhD Thesis, TU München (2011)
- ^ "4". Principles of Computerized Tomographic Imaging (PDF). IEEE Press. Institute for Electrical and Electronic Engineers. 1988. ISBN 978-0898714944.
The first such tomograms were made by Greenleaf et al. [Gre74], [Gre75], followed by Carson et al. [Car76], Jackowatz and Kak [Jak76], and Glover and Sharp [Glo77].
{{cite book}}: Unknown parameter|authors=ignored (help) - ^ Transducer elements position calibration in a ring array USCT system Satoshi Tamano ; Takashi Azuma ; Haruka Imoto ; Shu Takagi ; Shin-ichiro Umemura ; Yoichiro Matsumoto, Proc. SPIE 9419, Medical Imaging 2015: Ultrasonic Imaging and Tomography, 94190P (March 17, 2015); doi:10.1117/12.2082323
- ^ "Clinical Imaging with Transmissive Ultrasonic Computerized Tomography". IEEE Transactions on Biomedical Engineering. (28, 2): 177–185. 1981.
{{cite journal}}: Unknown parameter|authors=ignored (help)