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<export-example>
  <doc>
    <id>137</id>
    <completedYear/>
    <publishedYear>2008</publishedYear>
    <thesisYearAccepted/>
    <language>eng</language>
    <pageFirst>1142</pageFirst>
    <pageLast>1146</pageLast>
    <pageNumber/>
    <edition/>
    <issue>6</issue>
    <volume>35</volume>
    <type>article</type>
    <publisherName/>
    <publisherPlace/>
    <creatingCorporation/>
    <contributingCorporation/>
    <belongsToBibliography>0</belongsToBibliography>
    <completedDate>--</completedDate>
    <publishedDate>--</publishedDate>
    <thesisDateAccepted>--</thesisDateAccepted>
    <title language="eng">MR-based attenuation correction for torso-PET/MR imaging</title>
    <abstract language="eng">Purpose&#13;
MR-based attenuation correction (AC) will become an integral part of combined PET/MR systems. Here, we propose a toolbox to validate MR-AC of clinical PET/MRI data sets.&#13;
Methods&#13;
Torso scans of ten patients were acquired on a combined PET/CT and on a 1.5-T MRI system. MR-based attenuation data were derived from the CT following MR–CT image co-registration and subsequent histogram matching. PET images were reconstructed after CT- (PET/CT) and MR-based AC (PET/MRI). Lesion-to-background (L/B) ratios were estimated on PET/CT and PET/MRI.&#13;
Results&#13;
MR–CT histogram matching leads to a mean voxel intensity difference in the CT- and MR-based attenuation images of 12% (max). Mean differences between PET/MRI and PET/CT were 19% (max). L/B ratios were similar except for the lung where local misregistration and intensity transformation leads to a biased PET/MRI.&#13;
Conclusion&#13;
Our toolbox can be used to study pitfalls in MR-AC. We found that co-registration accuracy and pixel value transformation determine the accuracy of PET/MRI.</abstract>
    <parentTitle language="eng">European Journal of Nuclear Medicine and Molecular Imaging</parentTitle>
    <subTitle language="eng">pitfalls in mapping MR to CT data</subTitle>
    <identifier type="doi">10.1007/s00259-008-0734-0</identifier>
    <author>Thomas Beyer</author>
    <author>Markus Weigert</author>
    <author>Harald H. Quick</author>
    <author>Uwe Pietrzyk</author>
    <author>Florian Vogt</author>
    <author>Christoph Palm</author>
    <author>Gerald Antoch</author>
    <author>Stefan P. Müller</author>
    <author>Andreas Bockisch</author>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>PET/MRI</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>PET/CT</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>Attenuation correction</value>
    </subject>
    <subject>
      <language>deu</language>
      <type>swd</type>
      <value>Kernspintomografie</value>
    </subject>
    <subject>
      <language>deu</language>
      <type>swd</type>
      <value>Positronen-Emissions-Tomografie</value>
    </subject>
    <subject>
      <language>deu</language>
      <type>swd</type>
      <value>Schwächung</value>
    </subject>
    <collection role="ddc" number="0">Informatik, Informationswissenschaft, allgemeine Werke</collection>
    <collection role="institutes" number="FakIM">Fakultät Informatik und Mathematik</collection>
    <collection role="persons" number="palmremic">Palm, Christoph (Prof. Dr.) - ReMIC</collection>
    <collection role="othpublikationsherkunft" number="">Externe Publikationen</collection>
    <collection role="othforschungsschwerpunkt" number="16314">Lebenswissenschaften und Ethik</collection>
    <collection role="institutes" number="">Labor Regensburg Medical Image Computing (ReMIC)</collection>
  </doc>
  <doc>
    <id>141</id>
    <completedYear/>
    <publishedYear>2008</publishedYear>
    <thesisYearAccepted/>
    <language>eng</language>
    <pageFirst>59</pageFirst>
    <pageLast>66</pageLast>
    <pageNumber/>
    <edition/>
    <issue>1</issue>
    <volume>18</volume>
    <type>article</type>
    <publisherName/>
    <publisherPlace/>
    <creatingCorporation/>
    <contributingCorporation/>
    <belongsToBibliography>0</belongsToBibliography>
    <completedDate>--</completedDate>
    <publishedDate>--</publishedDate>
    <thesisDateAccepted>--</thesisDateAccepted>
    <title language="eng">Whole-body PET/CT imaging</title>
    <abstract language="eng">Aim&#13;
Combined whole-body (WB) PET/CT imaging provides better overall co-registration compared to separate CT and PET. However, in clinical routine local PET-CT mis-registration cannot be avoided. Thus, the reconstructed PET tracer distribution may be biased when using the misaligned CT transmission data for CT-based attenuation correction (CT-AC). We investigate the feasibility of retrospective co-registration techniques to align CT and PET images prior to CT-AC, thus improving potentially the quality of combined PET/CT imaging in clinical routine.&#13;
Methods&#13;
First, using a commercial software registration package CT images were aligned to the uncorrected PET data by rigid and non-rigid registration methods. Co-registration accuracy of both alignment approaches was assessed by reviewing the PET tracer uptake patterns (visual, linked cursor display) following attenuation correction based on the original and co-registered CT. Second, we investigated non-rigid registration based on a prototype ITK implementation of the B-spline algorithm on a similar targeted MR-CT registration task, there showing promising results.&#13;
Results&#13;
Manual rigid, landmark-based co-registration introduced unacceptable misalignment, in particular in peripheral areas of the whole-body images. Manual, non-rigid landmark-based co-registration prior to CT-AC was successful with minor loco-regional distortions. Nevertheless, neither rigid nor non-rigid automatic co-registration based on the Mutual Information image to image metric succeeded in co-registering the CT and noAC-PET images. In contrast to widely available commercial software registration our implementation of an alternative automated, non-rigid B-spline co-registration technique yielded promising results in this setting with MR-CT data.&#13;
Conclusion&#13;
In clinical PET/CT imaging, retrospective registration of CT and uncorrected PET images may improve the quality of the AC-PET images. As of today no validated and clinically viable commercial registration software is in routine use. This has triggered our efforts in pursuing new approaches to a validated, non-rigid co-registration algorithm applicable to whole-body PET/CT imaging of which first results are presented here. This approach appears suitable for applications in retrospective WB-PET/CT alignment.&#13;
&#13;
Ziel&#13;
Kombinierte PET/CT-Bildgebung ermöglicht verbesserte Koregistrierung von PET- und CT-Daten gegenüber separat akquirierten Bildern. Trotzdem entstehen in der klinischen Anwendung lokale Fehlregistrierungen, die zu Fehlern in der rekonstruierten PET- Tracerverteilung führen können, falls die unregistrierten CT-Daten zur Schwächungskorrektur (AC) der Emissionsdaten verwendet werden. Wir untersuchen daher die Anwendung von Bildregistrierungsalgorithmen vor der CT-basierten AC zur Verbesserung der PET-Aufnahmen.&#13;
Methoden&#13;
Mittels einer kommerziellen Registrierungssoftware wurden die CT-Daten eines PET/CT- Tomographen durch landmarken- und intensitätsbasierte rigide (starre) und nicht-rigide Registrierungsverfahren räumlich an die unkorrigierten PET-Emissionsdaten angepasst und zur AC verwendet. Zur Bewertung wurden die Tracerverteilungen in den PET-Bildern (vor AC, CT-AC, CT-AC nach Koregistrierung) visuell und mit Hilfe korrelierter Fadenkreuze verglichen. Zusätzlich untersuchten wir die ITK-Implementierung der bekannten B-spline basierten, nicht-rigiden Registrierungsansätze im Hinblick auf ihre Verwendbarkeit für die multimodale PET/CT-Ganzkörperregistrierung.&#13;
Ergebnisse&#13;
Mittels landmarkenbasierter, nicht-rigider Registrierung konnte die Tracerverteilung in den PET-Daten lokal verbessert werden. Landmarkenbasierte rigide Registrierung führte zu starker Fehlregistrierung in entfernten Körperregionen. Automatische rigide und nicht-rigide Registrierung unter Verwendung der Mutual-Information-Ähnlichkeitsmetrik versagte auf allen verwendeten Datensätzen. Die automatische Registrierung mit B-spline-Funktionen zeigte vielversprechende Resultate in der Anwendung auf einem ähnlich gelagerten CT–MR-Registrierungsproblem.&#13;
Fazit&#13;
Retrospektive, nicht-rigide Registrierung unkorrigierter PET- und CT-Aufnahmen aus kombinierten Aufnahmensystemen vor der AC kann die Qualität von PET-Aufnahmen im klinischen Einsatz verbessern. Trotzdem steht bis heute im klinischen Alltag keine validierte, automatische Registrierungssoftware zur Verfügung. Wir verfolgen dazu Ansätze für validierte, nicht-rigide Bildregistrierung für den klinischen Einsatz und präsentieren erste Ergebnisse.</abstract>
    <parentTitle language="deu">Zeitschrift für Medizinische Physik</parentTitle>
    <subTitle language="eng">Combining software- and hardware-based co-registration</subTitle>
    <identifier type="doi">10.1016/j.zemedi.2007.07.004</identifier>
    <author>Markus Weigert</author>
    <author>Uwe Pietrzyk</author>
    <author>Stefan P. Müller</author>
    <author>Christoph Palm</author>
    <author>Thomas Beyer</author>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>PET/CT</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>combined imaging</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>image co-registration</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>attenuation</value>
    </subject>
    <subject>
      <language>eng</language>
      <type>uncontrolled</type>
      <value>correction</value>
    </subject>
    <subject>
      <language>deu</language>
      <type>swd</type>
      <value>Positronen-Emissions-Tomografie</value>
    </subject>
    <subject>
      <language>deu</language>
      <type>swd</type>
      <value>Computertomografie</value>
    </subject>
    <subject>
      <language>deu</language>
      <type>swd</type>
      <value>Bildgebendes Verfahren</value>
    </subject>
    <subject>
      <language>deu</language>
      <type>swd</type>
      <value>Registrierung &lt;Bildverarbeitung&gt;</value>
    </subject>
    <subject>
      <language>deu</language>
      <type>swd</type>
      <value>Schwächung</value>
    </subject>
    <collection role="ddc" number="0">Informatik, Informationswissenschaft, allgemeine Werke</collection>
    <collection role="institutes" number="FakIM">Fakultät Informatik und Mathematik</collection>
    <collection role="persons" number="palmremic">Palm, Christoph (Prof. Dr.) - ReMIC</collection>
    <collection role="othpublikationsherkunft" number="">Externe Publikationen</collection>
    <collection role="othforschungsschwerpunkt" number="16314">Lebenswissenschaften und Ethik</collection>
    <collection role="institutes" number="">Labor Regensburg Medical Image Computing (ReMIC)</collection>
  </doc>
</export-example>
