Hybrid echo and x-ray image guidance for cardiac catheterization procedures by using a robotic arm: a feasibility study
Identifieur interne : 000628 ( Istex/Corpus ); précédent : 000627; suivant : 000629Hybrid echo and x-ray image guidance for cardiac catheterization procedures by using a robotic arm: a feasibility study
Auteurs : Yingliang Ma ; Graeme P. Penney ; Dennis Bos ; Peter Frissen ; C Aldo Rinaldi ; Reza Razavi ; Kawal S. RhodeSource :
- Physics in Medicine and Biology [ 0031-9155 ] ; 2010.
Abstract
We present a feasibility study on hybrid echocardiography (echo) and x-ray image guidance for cardiac catheterization procedures. A self-tracked, remotely operated robotic arm with haptic feedback was developed that attached to a standard x-ray table. This was used to safely manipulate a three-dimensional (3D) trans-thoracic echo probe during simultaneous x-ray fluoroscopy and echo acquisitions. By a combination of calibration and tracking of the echo and x-ray systems, it was possible to register the 3D echo images with the 2D x-ray images. Visualization of the combined data was achieved by either overlaying triangulated surfaces extracted from segmented echo data onto the x-ray images or by overlaying volume rendered 3D echo data. Furthermore, in order to overcome the limited field of view of the echo probe, it was possible to create extended field of view (EFOV) 3D echo images by co-registering multiple tracked echo data to generate larger roadmaps for procedure guidance. The registration method was validated using a cross-wire phantom and showed a 2D target registration error of 3.5 mm. The clinical feasibility of the method was demonstrated during two clinical cases for patients undergoing cardiac pacing studies. The EFOV technique was demonstrated using two healthy volunteers.
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DOI: 10.1088/0031-9155/55/13/N01
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Penney</name><affiliation><mods:affiliation>Division of Imaging Sciences, King's College, London SE1 7EH, UK</mods:affiliation></affiliation></author><author><name sortKey="Bos, Dennis" sort="Bos, Dennis" uniqKey="Bos D" first="Dennis" last="Bos">Dennis Bos</name><affiliation><mods:affiliation>Philips Applied Technologies, High Tech. Campus 7, 5656 AE Eindhoven, The Netherlands</mods:affiliation></affiliation></author><author><name sortKey="Frissen, Peter" sort="Frissen, Peter" uniqKey="Frissen P" first="Peter" last="Frissen">Peter Frissen</name><affiliation><mods:affiliation>Philips Applied Technologies, High Tech. Campus 7, 5656 AE Eindhoven, The Netherlands</mods:affiliation></affiliation></author><author><name sortKey="Rinaldi, C Aldo" sort="Rinaldi, C Aldo" uniqKey="Rinaldi C" first="C Aldo" last="Rinaldi">C Aldo Rinaldi</name><affiliation><mods:affiliation>Department of Cardiology, Guy's and St Thomas' NHS Foundation Trust, London SE1 7EH, UK</mods:affiliation></affiliation></author><author><name sortKey="Razavi, Reza" sort="Razavi, Reza" uniqKey="Razavi R" first="Reza" last="Razavi">Reza Razavi</name><affiliation><mods:affiliation>Division of Imaging Sciences, King's College, London SE1 7EH, UK</mods:affiliation></affiliation></author><author><name sortKey="Rhode, Kawal S" sort="Rhode, Kawal S" uniqKey="Rhode K" first="Kawal S" last="Rhode">Kawal S. Rhode</name><affiliation><mods:affiliation>Division of Imaging Sciences, King's College, London SE1 7EH, UK</mods:affiliation></affiliation></author></titleStmt><publicationStmt><idno type="wicri:source">ISTEX</idno><idno type="RBID">ISTEX:6A03F416BBD9815142DC97D50DD3A5916A2F72D2</idno><date when="2010" year="2010">2010</date><idno type="doi">10.1088/0031-9155/55/13/N01</idno><idno type="url">https://api.istex.fr/document/6A03F416BBD9815142DC97D50DD3A5916A2F72D2/fulltext/pdf</idno><idno type="wicri:Area/Istex/Corpus">000628</idno></publicationStmt><sourceDesc><biblStruct><analytic><title level="a">Hybrid echo and x-ray image guidance for cardiac catheterization procedures by using a robotic arm: a feasibility study</title><author><name sortKey="Ma, Yingliang" sort="Ma, Yingliang" uniqKey="Ma Y" first="Yingliang" last="Ma">Yingliang Ma</name><affiliation><mods:affiliation>Division of Imaging Sciences, King's College, London SE1 7EH, UK</mods:affiliation></affiliation><affiliation><mods:affiliation>E-mail:y.ma@kcl.ac.uk</mods:affiliation></affiliation></author><author><name sortKey="Penney, Graeme P" sort="Penney, Graeme P" uniqKey="Penney G" first="Graeme P" last="Penney">Graeme P. Penney</name><affiliation><mods:affiliation>Division of Imaging Sciences, King's College, London SE1 7EH, UK</mods:affiliation></affiliation></author><author><name sortKey="Bos, Dennis" sort="Bos, Dennis" uniqKey="Bos D" first="Dennis" last="Bos">Dennis Bos</name><affiliation><mods:affiliation>Philips Applied Technologies, High Tech. Campus 7, 5656 AE Eindhoven, The Netherlands</mods:affiliation></affiliation></author><author><name sortKey="Frissen, Peter" sort="Frissen, Peter" uniqKey="Frissen P" first="Peter" last="Frissen">Peter Frissen</name><affiliation><mods:affiliation>Philips Applied Technologies, High Tech. Campus 7, 5656 AE Eindhoven, The Netherlands</mods:affiliation></affiliation></author><author><name sortKey="Rinaldi, C Aldo" sort="Rinaldi, C Aldo" uniqKey="Rinaldi C" first="C Aldo" last="Rinaldi">C Aldo Rinaldi</name><affiliation><mods:affiliation>Department of Cardiology, Guy's and St Thomas' NHS Foundation Trust, London SE1 7EH, UK</mods:affiliation></affiliation></author><author><name sortKey="Razavi, Reza" sort="Razavi, Reza" uniqKey="Razavi R" first="Reza" last="Razavi">Reza Razavi</name><affiliation><mods:affiliation>Division of Imaging Sciences, King's College, London SE1 7EH, UK</mods:affiliation></affiliation></author><author><name sortKey="Rhode, Kawal S" sort="Rhode, Kawal S" uniqKey="Rhode K" first="Kawal S" last="Rhode">Kawal S. Rhode</name><affiliation><mods:affiliation>Division of Imaging Sciences, King's College, London SE1 7EH, UK</mods:affiliation></affiliation></author></analytic><monogr></monogr><series><title level="j">Physics in Medicine and Biology</title><title level="j" type="abbrev">Phys. Med. Biol.</title><idno type="ISSN">0031-9155</idno><idno type="eISSN">1361-6560</idno><imprint><publisher>IOP Publishing</publisher><date type="published" when="2010">2010</date><biblScope unit="volume">55</biblScope><biblScope unit="issue">13</biblScope><biblScope unit="page" from="N371">N371</biblScope><biblScope unit="page" to="N382">N382</biblScope><biblScope unit="production">Printed in the UK</biblScope></imprint><idno type="ISSN">0031-9155</idno></series><idno type="istex">6A03F416BBD9815142DC97D50DD3A5916A2F72D2</idno><idno type="DOI">10.1088/0031-9155/55/13/N01</idno><idno type="PII">S0031-9155(10)37844-4</idno><idno type="articleID">337844</idno><idno type="articleNumber">N01</idno></biblStruct></sourceDesc><seriesStmt><idno type="ISSN">0031-9155</idno></seriesStmt></fileDesc><profileDesc><textClass></textClass><langUsage><language ident="en">en</language></langUsage></profileDesc></teiHeader><front><div type="abstract">We present a feasibility study on hybrid echocardiography (echo) and x-ray image guidance for cardiac catheterization procedures. A self-tracked, remotely operated robotic arm with haptic feedback was developed that attached to a standard x-ray table. This was used to safely manipulate a three-dimensional (3D) trans-thoracic echo probe during simultaneous x-ray fluoroscopy and echo acquisitions. By a combination of calibration and tracking of the echo and x-ray systems, it was possible to register the 3D echo images with the 2D x-ray images. Visualization of the combined data was achieved by either overlaying triangulated surfaces extracted from segmented echo data onto the x-ray images or by overlaying volume rendered 3D echo data. Furthermore, in order to overcome the limited field of view of the echo probe, it was possible to create extended field of view (EFOV) 3D echo images by co-registering multiple tracked echo data to generate larger roadmaps for procedure guidance. The registration method was validated using a cross-wire phantom and showed a 2D target registration error of 3.5 mm. The clinical feasibility of the method was demonstrated during two clinical cases for patients undergoing cardiac pacing studies. The EFOV technique was demonstrated using two healthy volunteers.</div></front></TEI><istex><corpusName>iop</corpusName><author><json:item><name>YingLiang Ma</name><affiliations><json:string>Division of Imaging Sciences, King's College, London SE1 7EH, UK</json:string><json:string>E-mail:y.ma@kcl.ac.uk</json:string></affiliations></json:item><json:item><name>Graeme P Penney</name><affiliations><json:string>Division of Imaging Sciences, King's College, London SE1 7EH, UK</json:string></affiliations></json:item><json:item><name>Dennis Bos</name><affiliations><json:string>Philips Applied Technologies, High Tech. Campus 7, 5656 AE Eindhoven, The Netherlands</json:string></affiliations></json:item><json:item><name>Peter Frissen</name><affiliations><json:string>Philips Applied Technologies, High Tech. Campus 7, 5656 AE Eindhoven, The Netherlands</json:string></affiliations></json:item><json:item><name>C Aldo Rinaldi</name><affiliations><json:string>Department of Cardiology, Guy's and St Thomas' NHS Foundation Trust, London SE1 7EH, UK</json:string></affiliations></json:item><json:item><name>Reza Razavi</name><affiliations><json:string>Division of Imaging Sciences, King's College, London SE1 7EH, UK</json:string></affiliations></json:item><json:item><name>Kawal S Rhode</name><affiliations><json:string>Division of Imaging Sciences, King's College, London SE1 7EH, UK</json:string></affiliations></json:item></author><subject><json:item><lang><json:string>eng</json:string></lang><value>echo</value></json:item><json:item><lang><json:string>eng</json:string></lang><value>x-ray</value></json:item><json:item><lang><json:string>eng</json:string></lang><value>cardiac catheterization</value></json:item><json:item><lang><json:string>eng</json:string></lang><value>procedure</value></json:item><json:item><lang><json:string>eng</json:string></lang><value>robotic arm</value></json:item></subject><language><json:string>eng</json:string></language><abstract>We present a feasibility study on hybrid echocardiography (echo) and x-ray image guidance for cardiac catheterization procedures. A self-tracked, remotely operated robotic arm with haptic feedback was developed that attached to a standard x-ray table. This was used to safely manipulate a three-dimensional (3D) trans-thoracic echo probe during simultaneous x-ray fluoroscopy and echo acquisitions. By a combination of calibration and tracking of the echo and x-ray systems, it was possible to register the 3D echo images with the 2D x-ray images. Visualization of the combined data was achieved by either overlaying triangulated surfaces extracted from segmented echo data onto the x-ray images or by overlaying volume rendered 3D echo data. Furthermore, in order to overcome the limited field of view of the echo probe, it was possible to create extended field of view (EFOV) 3D echo images by co-registering multiple tracked echo data to generate larger roadmaps for procedure guidance. The registration method was validated using a cross-wire phantom and showed a 2D target registration error of 3.5 mm. The clinical feasibility of the method was demonstrated during two clinical cases for patients undergoing cardiac pacing studies. The EFOV technique was demonstrated using two healthy volunteers.</abstract><qualityIndicators><score>7.557</score><pdfVersion>1.4</pdfVersion><pdfPageSize>595 x 842 pts (A4)</pdfPageSize><refBibsNative>true</refBibsNative><keywordCount>5</keywordCount><abstractCharCount>1303</abstractCharCount><pdfWordCount>4705</pdfWordCount><pdfCharCount>27222</pdfCharCount><pdfPageCount>12</pdfPageCount><abstractWordCount>196</abstractWordCount></qualityIndicators><title>Hybrid echo and x-ray image guidance for cardiac catheterization procedures by using a robotic arm: a feasibility study</title><genre.original><json:string>note</json:string><json:string>note</json:string></genre.original><pii><json:string>S0031-9155(10)37844-4</json:string></pii><genre><json:string>other</json:string><json:string>research-article</json:string></genre><serie><volume>vol 5528</volume><language><json:string>unknown</json:string></language><title>Lecture Notes in Computer Science</title></serie><host><volume>55</volume><publisherId><json:string>PMB</json:string></publisherId><pages><total>12</total><last>N382</last><first>N371</first></pages><issn><json:string>0031-9155</json:string></issn><issue>13</issue><genre><json:string>journal</json:string></genre><language><json:string>unknown</json:string></language><eissn><json:string>1361-6560</json:string></eissn><title>Physics in Medicine and Biology</title></host><publicationDate>2010</publicationDate><copyrightDate>2010</copyrightDate><doi><json:string>10.1088/0031-9155/55/13/N01</json:string></doi><id>6A03F416BBD9815142DC97D50DD3A5916A2F72D2</id><score>1</score><fulltext><json:item><original>true</original><mimetype>application/pdf</mimetype><extension>pdf</extension><uri>https://api.istex.fr/document/6A03F416BBD9815142DC97D50DD3A5916A2F72D2/fulltext/pdf</uri></json:item><json:item><original>false</original><mimetype>application/zip</mimetype><extension>zip</extension><uri>https://api.istex.fr/document/6A03F416BBD9815142DC97D50DD3A5916A2F72D2/fulltext/zip</uri></json:item><istex:fulltextTEI uri="https://api.istex.fr/document/6A03F416BBD9815142DC97D50DD3A5916A2F72D2/fulltext/tei"><teiHeader><fileDesc><titleStmt><title level="a">Hybrid echo and x-ray image guidance for cardiac catheterization procedures by using a robotic arm: a feasibility study</title></titleStmt><publicationStmt><authority>ISTEX</authority><publisher>IOP Publishing</publisher><availability><p>IOP</p></availability><date>2010</date></publicationStmt><sourceDesc><biblStruct type="inbook"><analytic><title level="a">Hybrid echo and x-ray image guidance for cardiac catheterization procedures by using a robotic arm: a feasibility study</title><author><persName><forename type="first">YingLiang</forename><surname>Ma</surname></persName><affiliation>Division of Imaging Sciences, King's College, London SE1 7EH, UK</affiliation><affiliation>E-mail:y.ma@kcl.ac.uk</affiliation></author><author><persName><forename type="first">Graeme P</forename><surname>Penney</surname></persName><affiliation>Division of Imaging Sciences, King's College, London SE1 7EH, UK</affiliation></author><author><persName><forename type="first">Dennis</forename><surname>Bos</surname></persName><affiliation>Philips Applied Technologies, High Tech. Campus 7, 5656 AE Eindhoven, The Netherlands</affiliation></author><author><persName><forename type="first">Peter</forename><surname>Frissen</surname></persName><affiliation>Philips Applied Technologies, High Tech. Campus 7, 5656 AE Eindhoven, The Netherlands</affiliation></author><author><persName><forename type="first">C Aldo</forename><surname>Rinaldi</surname></persName><affiliation>Department of Cardiology, Guy's and St Thomas' NHS Foundation Trust, London SE1 7EH, UK</affiliation></author><author><persName><forename type="first">Reza</forename><surname>Razavi</surname></persName><affiliation>Division of Imaging Sciences, King's College, London SE1 7EH, UK</affiliation></author><author><persName><forename type="first">Kawal S</forename><surname>Rhode</surname></persName><affiliation>Division of Imaging Sciences, King's College, London SE1 7EH, UK</affiliation></author></analytic><monogr><title level="j">Physics in Medicine and Biology</title><title level="j" type="abbrev">Phys. Med. Biol.</title><idno type="pISSN">0031-9155</idno><idno type="eISSN">1361-6560</idno><imprint><publisher>IOP Publishing</publisher><date type="published" when="2010"></date><biblScope unit="volume">55</biblScope><biblScope unit="issue">13</biblScope><biblScope unit="page" from="N371">N371</biblScope><biblScope unit="page" to="N382">N382</biblScope><biblScope unit="production">Printed in the UK</biblScope></imprint></monogr><idno type="istex">6A03F416BBD9815142DC97D50DD3A5916A2F72D2</idno><idno type="DOI">10.1088/0031-9155/55/13/N01</idno><idno type="PII">S0031-9155(10)37844-4</idno><idno type="articleID">337844</idno><idno type="articleNumber">N01</idno></biblStruct></sourceDesc></fileDesc><profileDesc><creation><date>2010</date></creation><langUsage><language ident="en">en</language></langUsage><abstract><p>We present a feasibility study on hybrid echocardiography (echo) and x-ray image guidance for cardiac catheterization procedures. A self-tracked, remotely operated robotic arm with haptic feedback was developed that attached to a standard x-ray table. This was used to safely manipulate a three-dimensional (3D) trans-thoracic echo probe during simultaneous x-ray fluoroscopy and echo acquisitions. By a combination of calibration and tracking of the echo and x-ray systems, it was possible to register the 3D echo images with the 2D x-ray images. Visualization of the combined data was achieved by either overlaying triangulated surfaces extracted from segmented echo data onto the x-ray images or by overlaying volume rendered 3D echo data. Furthermore, in order to overcome the limited field of view of the echo probe, it was possible to create extended field of view (EFOV) 3D echo images by co-registering multiple tracked echo data to generate larger roadmaps for procedure guidance. The registration method was validated using a cross-wire phantom and showed a 2D target registration error of 3.5 mm. The clinical feasibility of the method was demonstrated during two clinical cases for patients undergoing cardiac pacing studies. The EFOV technique was demonstrated using two healthy volunteers.</p></abstract><textClass><keywords scheme="keyword"><list><head>keywords</head><item><term>echo</term></item><item><term>x-ray</term></item><item><term>cardiac catheterization</term></item><item><term>procedure</term></item><item><term>robotic arm</term></item></list></keywords></textClass></profileDesc><revisionDesc><change when="2010">Published</change></revisionDesc></teiHeader></istex:fulltextTEI><json:item><original>false</original><mimetype>text/plain</mimetype><extension>txt</extension><uri>https://api.istex.fr/document/6A03F416BBD9815142DC97D50DD3A5916A2F72D2/fulltext/txt</uri></json:item></fulltext><metadata><istex:metadataXml wicri:clean="corpus iop not found" wicri:toSee="no header"><istex:xmlDeclaration>version="1.0" encoding="ISO-8859-1"</istex:xmlDeclaration><istex:docType SYSTEM="http://ej.iop.org/dtd/iopv1_5_2.dtd" name="istex:docType"></istex:docType><istex:document><article artid="pmb337844"><article-metadata><jnl-data jnlid="pmb"><jnl-fullname>Physics in Medicine and Biology</jnl-fullname><jnl-abbreviation>Phys. Med. Biol.</jnl-abbreviation><jnl-shortname>PMB</jnl-shortname><jnl-issn>0031-9155</jnl-issn><jnl-coden>PHMBA7</jnl-coden><jnl-imprint>IOP Publishing</jnl-imprint><jnl-web-address>stacks.iop.org/PMB</jnl-web-address></jnl-data><volume-data><year-publication>2010</year-publication><volume-number>55</volume-number></volume-data><issue-data><issue-number>13</issue-number><coverdate>7 July 2010</coverdate></issue-data><article-data><article-type type="note" sort="regular">NOTE</article-type><type-number type="note" artnum="N01">1</type-number><article-number>337844</article-number><first-page>N371</first-page><last-page>N382</last-page><length>12</length><pii>S0031-9155(10)37844-4</pii><doi>10.1088/0031-9155/55/13/N01</doi><copyright>2010 Institute of Physics and Engineering in Medicine</copyright><ccc>0031-9155/10/130371+12$30.00</ccc><printed>Printed in the UK</printed><features colour="global" mmedia="no" suppdata="no"></features></article-data></article-metadata><header><title-group><title>Hybrid echo and x-ray image guidance for cardiac catheterization procedures by using a robotic arm: a feasibility study</title><short-title>Hybrid echo and x-ray image guidance for cardiac catheterization procedures by using a robotic arm</short-title><ej-title>Hybrid echo and x-ray image guidance for cardiac catheterization procedures by using a robotic arm</ej-title></title-group><author-group><author address="pmb337844ad1" email="pmb337844ea1"><first-names>YingLiang</first-names><second-name>Ma</second-name></author><author address="pmb337844ad1"><first-names>Graeme P</first-names><second-name>Penney</second-name></author><author address="pmb337844ad2"><first-names>Dennis</first-names><second-name>Bos</second-name></author><author address="pmb337844ad2"><first-names>Peter</first-names><second-name>Frissen</second-name></author><author address="pmb337844ad3"><first-names>C Aldo</first-names><second-name>Rinaldi</second-name></author><author address="pmb337844ad1"><first-names>Reza</first-names><second-name>Razavi</second-name></author><author address="pmb337844ad1"><first-names>Kawal S</first-names><second-name>Rhode</second-name></author></author-group><address-group><address id="pmb337844ad1"><orgname>Division of Imaging Sciences, King's College</orgname>, London SE1 7EH, <country>UK</country></address><address id="pmb337844ad2"><orgname>Philips Applied Technologies, High Tech. Campus 7</orgname>, 5656 AE Eindhoven, <country>The Netherlands</country></address><address id="pmb337844ad3"><orgname>Department of Cardiology, Guy's and St Thomas' NHS Foundation Trust</orgname>, London SE1 7EH, <country>UK</country></address><e-address id="pmb337844ea1"><email mailto="y.ma@kcl.ac.uk">y.ma@kcl.ac.uk</email></e-address></address-group><history received="14 November 2009" finalform="12 May 2010" online="9 June 2010"></history><abstract-group><abstract><heading>Abstract</heading><p indent="no">We present a feasibility study on hybrid echocardiography (echo) and x-ray image guidance for cardiac catheterization procedures. A self-tracked, remotely operated robotic arm with haptic feedback was developed that attached to a standard x-ray table. This was used to safely manipulate a three-dimensional (3D) trans-thoracic echo probe during simultaneous x-ray fluoroscopy and echo acquisitions. By a combination of calibration and tracking of the echo and x-ray systems, it was possible to register the 3D echo images with the 2D x-ray images. Visualization of the combined data was achieved by either overlaying triangulated surfaces extracted from segmented echo data onto the x-ray images or by overlaying volume rendered 3D echo data. Furthermore, in order to overcome the limited field of view of the echo probe, it was possible to create extended field of view (EFOV) 3D echo images by co-registering multiple tracked echo data to generate larger roadmaps for procedure guidance. The registration method was validated using a cross-wire phantom and showed a 2D target registration error of 3.5 mm. The clinical feasibility of the method was demonstrated during two clinical cases for patients undergoing cardiac pacing studies. The EFOV technique was demonstrated using two healthy volunteers.</p></abstract></abstract-group><classifications><keywords><keyword>echo</keyword><keyword>x-ray</keyword><keyword>cardiac catheterization</keyword><keyword>procedure</keyword><keyword>robotic arm</keyword></keywords></classifications></header><body numbering="bysection" refstyle="alphabetic"><sec-level1 id="pmb337844s1" label="1"><heading>Introduction</heading><p indent="no">Cardiac catheterizations are undertaken either to obtain diagnostic information or to perform image-guided interventions. Traditionally, cardiac catheters, guide wires and devices, such as stents, are visualized using single plane or bi-plane digital x-ray fluoroscopy. Pure x-ray guidance has a number of disadvantages. X-ray images have very poor soft tissue contrast so that the heart and blood vessels are not well visualized. Therefore, during the manipulation of catheters or devices, the operator has to rely on the knowledge of the anatomy obtained either from experience or x-ray contrast angiographic images acquired during the procedure. Furthermore, x-ray imaging delivers a radiation dose to the patient and those carrying out the procedure. This can be significant for prolonged procedures (Kovoor <italic>et al</italic> <cite linkend="pmb337844bib08" show="year">1998</cite>) and in paediatric cases (Modan <italic>et al</italic> <cite linkend="pmb337844bib11" show="year">2000</cite>). One of several approaches to overcome these limitations is the fusion of pre-procedural three-dimensional (3D) anatomical images with live x-ray fluoroscopy. This can be performed using specialized hybrid imaging systems, such as combined x-ray and magnetic resonance (MR) systems (XMR systems) (Rhode <italic>et al</italic> <cite linkend="pmb337844bib15" show="year">2005</cite>, de Silva <italic>et al</italic> <cite linkend="pmb337844bib02" show="year">2006</cite>, Ratnayaka <italic>et al</italic> <cite linkend="pmb337844bib14" show="year">2009</cite>). Alternatively, this can be performed using standard catheter laboratories using pre-procedural computed tomography (CT) images (Sra <italic>et al</italic> <cite linkend="pmb337844bib17" show="year">2007</cite>) or rotational x-ray angiography images (Knecht <italic>et al</italic> <cite linkend="pmb337844bib07" show="year">2010</cite>). The fusion approach has already demonstrated reduced procedure time and radiation dose (Sra <italic>et al</italic> <cite linkend="pmb337844bib17" show="year">2007</cite>, Ratnayaka <italic>et al</italic> <cite linkend="pmb337844bib14" show="year">2009</cite>).</p><p>Another approach to overcome the limitations of x-ray only guidance is to introduce the use of 3D echocardiography (echo) during cardiac catheterization procedures. 3D echo can either be trans-thoracic (TTE) or trans-oesophageal (TOE). Although image quality is superior when using TOE for interventional guidance, there is the requirement for general anaesthesia, whereas TTE can be used during procedures that only require sedation. As pointed out by Silvestry <italic>et al</italic> (<cite linkend="pmb337844bib16" show="year">2009</cite>), 3D echo has high temporal and spatial resolutions, and the hardware is widely available in hospitals at much lower cost compared with MR or CT systems. 3D echo guidance has already been used as an adjuvant to x-ray fluoroscopy for cardiac catheterization to treat congenital heart disease (Baker <italic>et al</italic> <cite linkend="pmb337844bib01" show="year">2009</cite>) and for left atrial radiofrequency ablation to treat atrial fibrillation (Mackensen <italic>et al</italic> <cite linkend="pmb337844bib10" show="year">2008</cite>). Furthermore, using 3D echo in cardiac catheterization procedures can also overcome some limitations of MR/CT-based fusion guidance. Firstly, 3D echo can give clinicians real-time cardiac anatomical and functional information. Secondly, if real-time 3D echo images are registered with live x-ray images, there is no need to compensate for patient motion such as cardiac, respiratory and bulk patient motion. For example, when using pre-procedural anatomical data, respiratory motion could cause a 2D registration error of over 14 mm (King <italic>et al</italic> <cite linkend="pmb337844bib06" show="year">2009</cite>), which is a significant compromise in the accuracy of guidance. Only a few examples of strategies to register 3D echo data to 2D x-ray fluoroscopy have been published. Jain <italic>et al</italic> (<cite linkend="pmb337844bib05" show="year">2009</cite>) used a combination of calibration and electromagnetic (EM) tracking of a 3D TOE probe to perform the registration and report a 2D accuracy of 2 mm in a phantom study. Gao <italic>et al</italic> (<cite linkend="pmb337844bib04" show="year">2010</cite>) used a combination of calibration and an image-based method to track a 3D TOE probe to register to x-ray fluoroscopy with a reported 2D error of 1.8 mm in a phantom study and less than 3 mm in two clinical electrophysiology cases. Finally, Rasche <italic>et al</italic> (<cite linkend="pmb337844bib13" show="year">2008</cite>) used calibration and optical tracking of a 3D TTE probe to perform the registration. They used multiple x-ray views of a phantom to project fiducials into the 3D echo data and reported a 3D error of below 2 mm. Furthermore, they demonstrated the method for one clinical case for a patient undergoing cardiac resynchronization therapy for heart failure and showed how functional information from echo can be additive to the guidance strategy. The results of these 3D echo to 2D x-ray registration studies have been encouraging and suggest that this type of guidance strategy will have a significant clinical impact in terms of reducing procedure time and radiation dose.</p><p>This study presents a solution for the registration of 3D TTE data to x-ray fluoroscopy for the guidance of cardiac catheterization procedures using a novel combination of engineering, algorithmic and clinical workflow components. For the engineering component, we introduce a self-tracked, remotely operated robotic arm with haptic feedback that holds a 3D TTE probe. This allows the prolonged, steady positioning of the echo probe on the patient's chest wall during an entire procedure (typical procedure time is 3–4 h). Remote operation allows the safe simultaneous acquisition of echo and x-ray data without significant radiation exposure to the operator. The algorithmic component is a combination of calibration, self-tracking of the robotic arm and optical tracking of the x-ray system (in part similar to that presented in Rasche <italic>et al</italic> <cite linkend="pmb337844bib13" show="year">2008</cite>) to form the 3D to 2D registration pipeline. We also tackle the problem of visualizing the 3D echo image data and concurrently displaying this with the x-ray images. In MR/CT-based fusion guidance, transparent surface rendering is chosen as the option of visualization of the 3D MR/CT image data as these data can be automatically segmented within the accuracy of 2 mm (Peters <italic>et al</italic> <cite linkend="pmb337844bib12" show="year">2007</cite>, Ecabert <italic>et al</italic> <cite linkend="pmb337844bib03" show="year">2008</cite>). For echo image data, fully automatic segmentation is difficult due to speckle noise, attenuation and motion artefacts, and partially imaged or missing tissue boundaries. Therefore, manual or semi-automatic methods are often employed to segment echo data and accuracy can vary. In this note, we investigate surface rendering similar to the method used in MR/CT-based fusion guidance. Furthermore, we also investigate direct volume rendering of part of 3D echo image data which only shows the tissue boundaries by using a 3D binary mask. This method does not require accurate segmentation and it can be easily adapted to be used in 4D (time series 3D) echo image data. The registration method was tested using a cross-wire phantom. We develop the clinical workflow by testing the echo calibration and tracking on two healthy volunteers to produce extended field of view (EFOV) echo data. Finally, we examine the clinical feasibility by using the hybrid system during two clinical cases for patients undergoing pacing studies for cardiac resynchronization therapy.</p><p>In the following sections, we outline the technical details of the robotic arm, echo to x-ray image registration, echo image data visualization, validation experiments and results.</p></sec-level1><sec-level1 id="pmb337844s2" label="2"><heading>The robotic arm</heading><p indent="no">The robotic arm was designed for remote operation and has haptic feedback functionality. It contains two major parts: the master controller and the slave robot. As shown in figure <figref linkend="pmb337844fig01" override="yes">1(a)</figref>, the master controller is a commercially available Force Dimension Omega 6 (Force Dimension, Switzerland). It has six degrees of freedom: three translations and three rotations.
<figure id="pmb337844fig01"><graphic><graphic-file version="print" format="EPS" filename="images/pmb337844fig01.eps" width="26pc"></graphic-file><graphic-file version="ej" format="JPEG" filename="images/pmb337844fig01.jpg"></graphic-file></graphic><caption id="pmb337844fc01" label="Figure 1"><p indent="no">Components of the robotic arm system. (a) The master controller showing the five degrees of freedom (blue arrows) and the three directions of force feedback (red arrows). (b) The slave robotic arm holding a 3D TTE probe.</p></caption></figure></p><p>The slave robot was specially designed and constructed by Philips Applied Technologies (Eindhoven, The Netherlands). This holds the echo probe (figure <figref linkend="pmb337844fig01" override="yes">1(b)</figref>), senses the translational forces on the tip of the probe and sends these forces back to the master controller. Three translations and two rotations are implemented for the echo probe. The rotation along the long axis of the probe was not implemented in this first prototype. The slave robot has five motors controlling the five degrees of freedom of the echo probe. Software was developed to read the rotation angle meters of the five motors. By combining this with information of the gear ratios, it was possible to compute the three translations (in mm) and two rotations (in degrees) of the echo probe. The slave robot mounts onto a specially designed frame that attaches onto the side rails of a standard catheter laboratory table. This frame allows the initial positioning of the slave relative to the patient and has minimal interference with the operation of the x-ray system.</p><p>The sonographer is able to remotely control the echo probe by using the master controller. The haptic feedback is critical to ensure that sufficient contact has occurred between the probe and the patient's chest wall. Furthermore, the applied force is limited to within safe levels to prevent injury or discomfort to the patient. After finding a suitable echo acquisition window and getting a desired echo image, the sonographer can release the control stick of the master controller and the echo probe will maintain a fixed position. The slave robot is programmed to maintain the contact force vector of the echo probe so that the probe will automatically move in response to a patient's chest wall motion due to respiration and small amounts of bulk patient motion. This feature allows the maintenance of echo image quality for long periods of time (more than 2 h).</p></sec-level1><sec-level1 id="pmb337844s3" label="3"><heading>Echo to x-ray registration</heading><p indent="no">Tracking, x-ray system calibration and echo system calibration were combined to fuse 3D echo images with 2D x-ray images.</p><sec-level2 id="pmb337844s3-1" label="3.1"><heading>Tracking</heading><p indent="no">Similar to the XMR fusion guidance system (Rhode <italic>et al</italic> <cite linkend="pmb337844bib15" show="year">2005</cite>), we track the x-ray c-arm and x-ray table using an optical tracking system, Optotrak 3020 (Northern Digital Inc., Ontario, Canada). As shown in figure <figref linkend="pmb337844fig02">2</figref>, both the c-arm and the x-ray table are tracked by attaching an array of six infrared emitting diodes (IREDs).
<figure id="pmb337844fig02"><graphic><graphic-file version="print" format="EPS" filename="images/pmb337844fig02.eps" width="26pc"></graphic-file><graphic-file version="ej" format="JPEG" filename="images/pmb337844fig02.jpg"></graphic-file></graphic><caption id="pmb337844fc02" label="Figure 2"><p indent="no">(a) Tracking the x-ray table. A tracker object consisting of an array of six IREDs is affixed to the x-ray table. (b) Tracking the x-ray c-arm. Six IREDs are affixed to an aluminium plate that attaches to the image intensifier. (c) The Optotrak 3020 tracking system.</p></caption></figure></p></sec-level2><sec-level2 id="pmb337844s3-2" label="3.2"><heading>X-ray system calibration</heading><p indent="no">The x-ray system calibration (Rhode <italic>et al</italic> <cite linkend="pmb337844bib15" show="year">2005</cite>) establishes the transformation between Optotrak tracking space and 2D x-ray image space. It involves imaging a specially designed acrylic calibration object (figure <figref linkend="pmb337844fig03">3</figref>). This object consists of a half cylinder that can accept up to 120 interchangeable fiducial markers that can be visualized with x-ray imaging and located using an Optotrak pointer. The fiducial markers were automatically located in the tracked multi-view x-ray images and these data were used to compute the transformation <italic>T</italic><sub>CArm2OPT</sub>(from the x-ray c-arm local coordinate system to the Optotrak tracking space) and the perspective projection transformation <italic>T</italic><sub>proj</sub> (from the x-ray c-arm local coordinate system to the 2D x-ray image space).
<figure id="pmb337844fig03"><graphic><graphic-file version="print" format="EPS" filename="images/pmb337844fig03.eps" width="18pc"></graphic-file><graphic-file version="ej" format="JPEG" filename="images/pmb337844fig03.jpg"></graphic-file></graphic><caption id="pmb337844fc03" label="Figure 3"><p indent="no">The x-ray system calibration phantom showing 20 fiducial markers. This was used to determine the perspective geometry of the x-ray system using multi-view tracked x-ray images.</p></caption></figure></p></sec-level2><sec-level2 id="pmb337844s3-3" label="3.3"><heading>Echo robotic arm system calibration</heading><p indent="no">We have previously developed a method to calibrate a 3D echo probe with the Optotrak system (Ma <italic>et al</italic> <cite linkend="pmb337844bib09" show="year">2008</cite>). This method uses a simple echo phantom (figure <figref linkend="pmb337844fig04">4</figref>) that consists of a large PVC box filled with water with a rubber band cross in the centre. The two rubber bands pass close to each other but do not physically touch to ensure that they form perfectly straight lines. The calibration technique involves the acquisition of at least three 3D images while tracking the 3D echo probe using the Optotrak system. Intensity-based image registration algorithms are used to rigidly register these image volumes together. These transformations, along with the probe tracking information are used to find the calibration matrix which provides the transformation from echo image space to the local coordinate system on the echo probe.
<figure id="pmb337844fig04"><graphic><graphic-file version="print" format="EPS" filename="images/pmb337844fig04.eps" width="18pc"></graphic-file><graphic-file version="ej" format="JPEG" filename="images/pmb337844fig04.jpg"></graphic-file></graphic><caption id="pmb337844fc04" label="Figure 4"><p indent="no">The echo system calibration phantom showing the two crossed rubber bands contained in the PVC box. This was filled with water and used to determine the relationship of the 3D echo volume with the self-tracked coordinate system of the robotic arm by using multiple tracked echo views.</p></caption></figure></p><p>Echo robotic arm system calibration is similar to echo Optotrak tracking system calibration. It is only necessary to replace the optical tracking matrices with robotic arm tracking matrices. The robotic arm tracking matrix <italic>T</italic><sub>Tip2Base</sub> gives the transformation from the tip of the probe to the base of the robotic arm which is determined based on the robot arm kinematics. The echo robotic arm system calibration matrix <italic>T</italic><sub>US2Tip</sub> provides the transformation from echo image space to the local coordinate system at the tip of the echo probe.</p></sec-level2><sec-level2 id="pmb337844s3-4" label="3.4"><heading>Defining the base of the robotic arm in the Optotrak tracking coordinate system</heading><p indent="no">Finally, there is a missing transformation link between the robotic arm coordinate system and Optotrak tracking coordinate system. To establish the link, firstly, the base of the robotic arm is rigidly attached to the x-ray table through a specially designed mounting frame. Secondly, three markers are rigidly attached on the base so that the 3D positions of these can be measured using an Optotrak pointer. Finally, a local coordinate system for the base of the robotic arm is defined by using the 3D positions of the three markers. Then landmark-based registration is carried out between the local coordinate system for the base of the robotic arm and the Optotrak tracking coordinate system to get the transformation <italic>T</italic><sub>Base2OPT</sub> which is determined from the Optotrak tracking of the base of the robotic arm.</p></sec-level2><sec-level2 id="pmb337844s3-5" label="3.5"><heading>Overall registration</heading><p indent="no">The registration of the 3D echo images with the 2D x-ray images is achieved by combining real-time robotic arm self-tracking and Optotrak tracking. An overview of the registration pipeline is shown in figure <figref linkend="pmb337844fig05">5</figref>. <italic>T</italic><sub>proj</sub> is the x-ray projection matrix which is calculated from the x-ray system calibration (section <secref linkend="pmb337844s3-2">3.2</secref>). <italic>T</italic><sub>CArm2OPT</sub> is the tracking matrix of the x-ray c-arm. <italic>T</italic><sub>Tip2Base</sub> is the robotic arm tracking matrix. <italic>T</italic><sub>US2Tip</sub> is the echo robotic arm system calibration matrix (section <secref linkend="pmb337844s3-3">3.3</secref>). <italic>T</italic><sub>Base2OPT</sub> is described in section <secref linkend="pmb337844s3-4">3.4</secref>. The overall echo to the x-ray registration matrix is computed as
<display-eqn id="pmb337844eqn01" eqnnum="1"></display-eqn><figure id="pmb337844fig05"><graphic><graphic-file version="print" format="EPS" filename="images/pmb337844fig05.eps" width="26pc"></graphic-file><graphic-file version="ej" format="JPEG" filename="images/pmb337844fig05.jpg"></graphic-file></graphic><caption id="pmb337844fc05" label="Figure 5"><p indent="no">Overall registration pipeline showing all the transformations required to transform from the 3D echo image coordinates to the 2D x-ray image coordinates. All matrices are rigid body except for the final x-ray projection matrix.</p></caption></figure></p><p>Because the base of the robotic arm can be moved to allow the echo probe access to different acquisition windows, we can update the <italic>T</italic><sub>Base2OPT</sub> by measuring the new 3D positions of the three markers on the base.</p></sec-level2></sec-level1><sec-level1 id="pmb337844s4" label="4"><heading>Echo image data visualization</heading><p indent="no">Two ways of visualizing 3D echo image data were investigated. One method is surface rendering where surfaces are extracted from manual segmentation of echo data using ITK-SNAP (Yushkevich <italic>et al</italic> <cite linkend="pmb337844bib19" show="year">2006</cite>). The manual segmentation method was selected because there are almost no robust and efficient automatic or semi-automatic echo segmentation methods working for all cardiac chambers. On the other hand, a clinical expert can use a 3D brush to segment the ventricular or atrial tissue boundaries within reasonable time frame (less than half hour) using ITK-SNAP. A 3D Gaussian blur filter is used to smooth the resulting binary images and the marching cubes algorithm is used to extract the surfaces from the binary data. Figure <figref linkend="pmb337844fig06" override="yes">6(a)</figref> gives an example.
<figure id="pmb337844fig06"><graphic><graphic-file version="print" format="EPS" filename="images/pmb337844fig06.eps" width="18pc"></graphic-file><graphic-file version="ej" format="JPEG" filename="images/pmb337844fig06.jpg"></graphic-file></graphic><caption id="pmb337844fc06" label="Figure 6"><p indent="no">Visualization of 3D echo image data. The left ventricle (LV) tissue boundaries are shown in green colour and right ventricle (RV) tissue boundaries are in blue colour. (a) Surface rendering. Surfaces were extracted from manual segmentation of the echo data. (b) Volume rendering. Tissue boundaries of LV and RV were masked out by using a 3D binary mask.</p></caption></figure></p><p>The second method is volume rendering. For the majority of cases, the regions of interest are the tissue boundaries of ventricles and atria. For this reason, a binary mask can be used to mask out the 3D regions outside the tissue boundaries in order to achieve similar visualization to surface rendering and remove a large proportion of artefacts, speckle noise and motion artefacts. The binary mask can be created by dilating the 3D binary images of the segmented echo image. However, only an approximate segmentation is required for this and can be performed by a clinical expert using down-sampled echo image data (the typical resolution used is 2 mm isotropic voxel size). The typical time to perform such segmentation is only about 5 min. Furthermore, a graphics processing unit (GPU)-accelerated volume rendering method was used based on 3D textures in DirectX 9 (Microsoft Inc., USA) where modified colour tables and opacity tables were employed to achieve the assignment of different colours to different tissue boundaries. Figure <figref linkend="pmb337844fig06" override="yes">6(b)</figref> gives an example of visualizing the same echo image data using volume rendering.</p></sec-level1><sec-level1 id="pmb337844s5" label="5"><heading>Experiments</heading><sec-level2 id="pmb337844s5-1" label="5.1"><heading>Phantom experiment</heading><p indent="no">The echo cross-wire phantom (figure <figref linkend="pmb337844fig04">4</figref>) was used to carry out a validation experiment to evaluate the accuracy of our registration methods. The x-ray system used in this experiment was a mobile cardiac x-ray set (BV Pulsera, Philips Healthcare, The Netherlands) and the echo system was a Philips iE33 echocardiography system. The robotic arm holding the 3D echo probe was mounted onto the x-ray table. The echo probe was tracked by the robotic arm itself. First an echo robotic arm system calibration was carried out by acquiring three echo volumes of the cross-wire phantom and three robotic arm tracking matrices. The calibration method is described in section <secref linkend="pmb337844s3-3">3.3</secref>. The x-ray system calibration had been carried out previously as is used during XMR fusion guidance cases on a routine basis.</p><p>For validation of our echo to x-ray registration, 11 3D echo volumes and the corresponding x-ray images of the cross-wire phantom were acquired. Two points were manually picked on each line of the cross-wire to generate a single pixel/voxel width line in the 3D echo image. The marching cubes algorithm was then used to create triangulated surfaces of the cross-wire. Figure <figref linkend="pmb337844fig07">7</figref> shows the overlay of the echo line surfaces with the x-ray image. The error measurement of our registration is defined as the root mean square (RMS) error between the line points of two lines in the echo image and the x-ray image. Errors were measured in the 2D x-ray image. The results show a RMS error of 3.5 mm (maximum error 4.2 mm).
<figure id="pmb337844fig07"><graphic><graphic-file version="print" format="EPS" filename="images/pmb337844fig07.eps" width="12pc"></graphic-file><graphic-file version="ej" format="JPEG" filename="images/pmb337844fig07.jpg"></graphic-file></graphic><caption id="pmb337844fc07" label="Figure 7"><p indent="no">An example result from the phantom experiment. The post-processed echo image data have been projected onto the x-ray image using the computed echo to the x-ray registration matrix. The echo data are shown in red. The registration error was quantified using the RMS point-to-point distance between the echo and x-ray lines.</p></caption></figure></p></sec-level2><sec-level2 id="pmb337844s5-2" label="5.2"><heading>Volunteer study</heading><p indent="no">The main aim of the volunteer study was to establish a suitable clinical workflow for using the robotic arm during cardiac catheterization procedures. Two healthy volunteers were recruited for the study. In the absence of the x-ray images, the robotic arm self-tracking was used to create EFOV echo volumes, which were created by using an extended phase-based compounding technique (Yao <italic>et al</italic> <cite linkend="pmb337844bib18" show="year">2009</cite>) for a large number of 3D echo volumes (figure <figref linkend="pmb337844fig08">8</figref>). Given an echo robotic arm system calibration matrix <italic>T</italic><sub>US2Tip</sub> and robotic arm tracking matrices <italic>T</italic><sub>Tip2Base</sub>, the registration between two 3D echo volumes <italic>T</italic><sub>imgreg2to1</sub> can be calculated by using
<display-eqn id="pmb337844eqn02" eqnnum="2"></display-eqn><figure id="pmb337844fig08"><graphic><graphic-file version="print" format="EPS" filename="images/pmb337844fig08.eps" width="21pc"></graphic-file><graphic-file version="ej" format="JPEG" filename="images/pmb337844fig08.jpg"></graphic-file></graphic><caption id="pmb337844fc08" label="Figure 8"><p indent="no">Extended field of view images from multiple 3D echo data obtained using the tracked echo probe as described in section <secref linkend="pmb337844s5-2">5.2</secref>. It can be seen how the overlapping data give greater coverage of the cardiac chambers.</p></caption></figure></p></sec-level2><sec-level2 id="pmb337844s5-3" label="5.3"><heading>Patient study</heading><p indent="no">Two patients' studies were carried out in the XMR suite in St Thomas' Hospital, London, using a local ethics committee approved protocol. Both patients were undergoing pacing studies prior to pacemaker implantation for heart failure. In both clinical cases, the 3D echo probe was successfully positioned onto the patient's chest using the robotic arm (figure <figref linkend="pmb337844fig09">9</figref>). A stable four-chamber view of the heart was achieved from the apical window for a several hour period (case 1: 2.5 h; case 2: 2 h) with the requirement of only a single position alteration during this period in each case. There was no discomfort to the patient and x-ray fluoroscopy could be acquired without the need to reposition the robotic arm. For each pacing mode, there was simultaneous acquisition of the position of the pacing leads using sequential biplane x-ray images, the intra-cardiac electrical data, the left ventricular pressure, and the 4D echo data using the robotic arm. This provided very rich data to evaluate the outcome of the pacing modes. In addition, the 3D locations of catheters could be reconstructed from the sequential biplane x-ray data and back-projected into the registered 3D echo data. Figure <figref linkend="pmb337844fig09" override="yes">9(c)</figref> shows an example with one catheter in the left ventricle and another in right ventricle.
<figure id="pmb337844fig09"><graphic><graphic-file version="print" format="EPS" filename="images/pmb337844fig09.eps" width="26pc"></graphic-file><graphic-file version="ej" format="JPEG" filename="images/pmb337844fig09.jpg"></graphic-file></graphic><caption id="pmb337844fc09" label="Figure 9"><p indent="no">Clinical case 1. The Ensite balloon catheter is shown by the arrow. (a) Clinical setup, (b) a zoom view of the robotic arm, (c) 3D reconstruction of catheters, (d) original x-ray image, (e) surface overlay, (f) volume rendering overlay.</p></caption></figure></p><p>For both clinical cases, manual segmentations were carried out for the myocardium of left ventricle (green object), the myocardium of right ventricle (blue object) and electrical measurement catheter (red object) and overlaid onto one of the 2D x-ray images (figures <figref linkend="pmb337844fig09" override="yes">9(e)</figref> and <figref linkend="pmb337844fig10" override="yes">10(b)</figref>). Volume rendering of the masked 3D echo image was also used and overlaid onto the 2D x-ray images (figures <figref linkend="pmb337844fig09" override="yes">9(f)</figref> and <figref linkend="pmb337844fig10" override="yes">10(c)</figref>). The electrical measurement catheter (Ensite Array Catheter, St Jude Medical, USA) was used to visually inspect the accuracy of the echo to x-ray registration. The size of the Ensite array is 18 mm × 48 mm (<webref url="http://www.sjm.com">http://www.sjm.com</webref>). As the Ensite array was visible in both x-ray and echo images, the in-plane registration accuracy was estimated by inspecting this device in the overlay images. The registration accuracy was found to be within the clinical accuracy requirement of 5 mm for these types of procedure. Furthermore, the 3D catheter reconstructions (see figure <figref linkend="pmb337844fig09" override="yes">9(c)</figref>) showed that the catheters lied within the target chambers without intersecting the myocardium.
<figure id="pmb337844fig10"><graphic><graphic-file version="print" format="EPS" filename="images/pmb337844fig10.eps" width="26pc"></graphic-file><graphic-file version="ej" format="JPEG" filename="images/pmb337844fig10.jpg"></graphic-file></graphic><caption id="pmb337844fc10" label="Figure 10"><p indent="no">Clinical case 2. The Ensite balloon catheter is shown by the arrow. (a) Original x-ray image, (b) surface overlay, (c) volume rendering overlay.</p></caption></figure></p></sec-level2></sec-level1><sec-level1 id="pmb337844s6" label="6"><heading>Discussion and conclusions</heading><p indent="no">Our feasibility study shows that our prototype hybrid guidance system can achieve a clinically useful registration accuracy of 3.5 mm evaluated using a cross-wire phantom. Using volunteers we have established a safe working protocol for the robotic arm and also showed that the system can be used for the acquisition of EFOV data which could be applied for roadmap creation. Our initial clinical study not only demonstrated the potential use of this system for device navigation but also for the acquisition of functional information. In the particular case of a pacing study, the simultaneous collection of 4D echo data with pacing could be used to compute regional volume changes, regional myocardial strain and ejection fraction in order to optimize the pacing locations. Two different visualization methods of 3D echo image data were investigated. Volume rendering is the preferred method as it does not required accurate segmentation and can be applied to visualize 4D echo image data. We are very encouraged by our initial results and aim to continue our evaluation by application of the system to further clinical cases. This type of system opens up the possibility of echo-based guidance of many types of cardiac interventional procedures.</p><p>Currently, we use a specially made robotic arm to hold the 3D echo probe throughout the procedure and this robotic arm has self-tracking, remote operation and force feedback functionalities. Self-tracking is preferred in our system as optical tracking systems have line-of-sight issues and magnetic tracking systems are less accurate due to metal interference in the catheter laboratory. In this first prototype of the robotic arm, the base is still tracked optically as is the x-ray system. However, the requirement for tracking the base can be removed in the next generation design with a self-tracked and possibly motorized base. Furthermore, the external tracking of the x-ray system can be replaced in modern catheter laboratories with self-tracked systems.</p><p>Our hybrid echo to x-ray image guidance system provides clinicians with an intermediate solution for guidance during cardiac catheterization procedures working towards echo only guidance. In the longer term it may be possible to replace the x-ray system with 3D echo (potentially combining TTE and TOE) only for guidance and so involve no modalities that use ionizing radiation.</p></sec-level1><acknowledgment><heading>Acknowledgments</heading><p indent="no">This work was co-funded by the Technology Strategy Board's Collaborative Research and Development program, following an open competition (grant no 17352) and Philips Healthcare, Best, the Netherlands. 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Campus 7, 5656 AE Eindhoven, The Netherlands</affiliation><role><roleTerm type="text">author</roleTerm></role></name><name type="personal"><namePart type="given">Peter</namePart><namePart type="family">Frissen</namePart><affiliation>Philips Applied Technologies, High Tech. Campus 7, 5656 AE Eindhoven, The Netherlands</affiliation><role><roleTerm type="text">author</roleTerm></role></name><name type="personal"><namePart type="given">C Aldo</namePart><namePart type="family">Rinaldi</namePart><affiliation>Department of Cardiology, Guy's and St Thomas' NHS Foundation Trust, London SE1 7EH, UK</affiliation><role><roleTerm type="text">author</roleTerm></role></name><name type="personal"><namePart type="given">Reza</namePart><namePart type="family">Razavi</namePart><affiliation>Division of Imaging Sciences, King's College, London SE1 7EH, UK</affiliation><role><roleTerm type="text">author</roleTerm></role></name><name type="personal"><namePart type="given">Kawal S</namePart><namePart type="family">Rhode</namePart><affiliation>Division of Imaging Sciences, King's College, London SE1 7EH, UK</affiliation><role><roleTerm type="text">author</roleTerm></role></name><typeOfResource>text</typeOfResource><genre type="other" displayLabel="note"></genre><genre type="research-article" displayLabel="note"></genre><originInfo><publisher>IOP Publishing</publisher><dateIssued encoding="w3cdtf">2010</dateIssued><copyrightDate encoding="w3cdtf">2010</copyrightDate></originInfo><language><languageTerm type="code" authority="iso639-2b">eng</languageTerm><languageTerm type="code" authority="rfc3066">en</languageTerm></language><physicalDescription><internetMediaType>text/html</internetMediaType><note type="production">Printed in the UK</note></physicalDescription><abstract>We present a feasibility study on hybrid echocardiography (echo) and x-ray image guidance for cardiac catheterization procedures. A self-tracked, remotely operated robotic arm with haptic feedback was developed that attached to a standard x-ray table. This was used to safely manipulate a three-dimensional (3D) trans-thoracic echo probe during simultaneous x-ray fluoroscopy and echo acquisitions. By a combination of calibration and tracking of the echo and x-ray systems, it was possible to register the 3D echo images with the 2D x-ray images. Visualization of the combined data was achieved by either overlaying triangulated surfaces extracted from segmented echo data onto the x-ray images or by overlaying volume rendered 3D echo data. Furthermore, in order to overcome the limited field of view of the echo probe, it was possible to create extended field of view (EFOV) 3D echo images by co-registering multiple tracked echo data to generate larger roadmaps for procedure guidance. The registration method was validated using a cross-wire phantom and showed a 2D target registration error of 3.5 mm. The clinical feasibility of the method was demonstrated during two clinical cases for patients undergoing cardiac pacing studies. The EFOV technique was demonstrated using two healthy volunteers.</abstract><subject><genre>keywords</genre><topic>echo</topic><topic>x-ray</topic><topic>cardiac catheterization</topic><topic>procedure</topic><topic>robotic arm</topic></subject><relatedItem type="host"><titleInfo><title>Physics in Medicine and Biology</title></titleInfo><titleInfo type="abbreviated"><title>Phys. Med. Biol.</title></titleInfo><genre type="journal">journal</genre><identifier type="ISSN">0031-9155</identifier><identifier type="eISSN">1361-6560</identifier><identifier type="PublisherID">PMB</identifier><identifier type="CODEN">PHMBA7</identifier><identifier type="URL">stacks.iop.org/PMB</identifier><part><date>2010</date><detail type="volume"><caption>vol.</caption><number>55</number></detail><detail type="issue"><caption>no.</caption><number>13</number></detail><extent unit="pages"><start>N371</start><end>N382</end><total>12</total></extent></part></relatedItem><identifier type="istex">6A03F416BBD9815142DC97D50DD3A5916A2F72D2</identifier><identifier type="DOI">10.1088/0031-9155/55/13/N01</identifier><identifier type="PII">S0031-9155(10)37844-4</identifier><identifier type="articleID">337844</identifier><identifier type="articleNumber">N01</identifier><accessCondition type="use and reproduction" contentType="copyright">2010 Institute of Physics and Engineering in Medicine</accessCondition><recordInfo><recordContentSource>IOP</recordContentSource><recordOrigin>2010 Institute of Physics and Engineering in Medicine</recordOrigin></recordInfo></mods></metadata></istex></record>Pour manipuler ce document sous Unix (Dilib)
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