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Diffusion Tensor Imaging in a Human PET/MR Hybrid System

Boss, Andreas MD, PhD*†; Kolb, Armin MSc; Hofmann, Matthias MSc†‡; Bisdas, Sotirios MD§; Nägele, Thomas MD§; Ernemann, Ulrike MD§; Stegger, Lars PhD*∥; Rossi, Cristina PhD; Schlemmer, Heinz-Peter MD*; Pfannenberg, Christina MD*; Reimold, Matthias MD; Claussen, Claus D. MD*; Pichler, Bernd J. PhD; Klose, Uwe PhD**

doi: 10.1097/RLI.0b013e3181dc3671
Technical Note
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Purpose: The aim of this study was to test and demonstrate the feasibility of diffusion tensor imaging (DTI) with a hybrid positron emission tomography (PET)/magnetic resonance imaging system for simultaneous PET and magnetic resonance (MR) data acquisition.

Materials and Methods: All measurements were performed with a prototype hybrid PET/MR scanner dedicated for brain and head imaging. The PET scanner, which is inserted into a conventional 3.0-Tesla high field MR imager equipped with a transmit/receive birdcage head coil, consists of 192 block detectors with a matrix of 12 × 12 lutetium oxyorthosilicate scintillation crystals combined with MR-compatible 3 × 3 avalanche photodiode arrays. In 7 volunteers and 4 patients with brain tumors, DTI was performed during simultaneous PET data readout applying a diffusion weighted echo planar sequence (12 noncollinear directions, echo time (TE)/repetition time (TR) 98 ms/5300 ms, b-value 800 s/mm2). Image quality and accuracy of DTI were assessed in comparison with DTI images acquired after removal of the PET insert.

Results: The diffusion images showed good image quality in all volunteers regardless of simultaneous PET data readout or after removal of the PET scanner; however, significantly (P < 0.01) stronger rim artifacts were found in fractional anisotropy images computed from DTI images recorded during simultaneous PET acquisition, demonstrating higher eddy-current effects. In region of interest analysis, no notable differences were found in the computation of the direction of the principal eigenvector (P > 0.05) and fractional anisotropy values (P > 0.05). In the assessment of pathologies, in all 4 patients PET and DTI provided important clinical information in addition to conventional magnetic resonance imaging.

Conclusion: Diffusion tensor imaging may be combined with simultaneous PET data acquisition, offering additional important morphologic and functional information for treatment planning in patients with brain tumors.

From the *Department of Diagnostic and Interventional Radiology, Eberhard-Karls University, Tübingen, Germany; †Laboratory of Preclinical Imaging and Imaging Technology of the Werner Siemens-Foundation, Eberhard-Karls University, Tübingen, Germany; ‡Max Planck Institute for Biological Cybernetics, Tübingen, Germany; §Department of Diagnostic and Interventional Neuroradiology, Eberhard-Karls University, Tübingen, Germany; ‖Department of Nuclear Medicine, Eberhard-Karls University, Tübingen, Germany; ¶Section of Experimental Radiology, Department of Diagnostic Radiology, Eberhard-Karls University, Tübingen, Germany; and **Department of Neuroradiology, Eberhard-Karls University, Tübingen, Germany.

Received November 12, 2009; accepted for publication (after revision) January 20, 2010.

Reprints: Andreas Boss, MD, PhD, Department of Diagnostic and Interventional Radiology, Eberhard-Karls-University of Tübingen, Hoppe-Seyler-Str. 3, Tübingen 72076, Germany. E-mail: andreas.boss@med.uni-tuebingen.de.

© 2010 Lippincott Williams & Wilkins, Inc.