Frank Preiswerk¹, W. Scott Hoge¹, Matthew Toews¹, Jr-yuan George Chiou¹, Laurent Chauvin¹, Lawrence P. Panych¹, and Bruno Madore^1
1Department of Radiology, Harvard Medical School, Brigham and Women's Hospital, Boston, MA, United States

Imaging respiratory motion in the abdomen using MR is a challenge because of the limited speed of subsequent MR acquisitions. We developed a hybrid MR-US setup that exploits the very high acquisition rates of a 1d ultrasound probe for boosting the temporal resolution of MR image sequences. The 1d ultrasound data provides a fingerprint of the complex abdominal configuration at any respiratory state. Previously-acquired MR data are combined based on these fingerprints to produce a high-speed image sequence. The system even allows to continue "acquiring" MR images outside the scanner, based solely on the US signal.

Peter Roland Seevinck¹, Cornelis A van den Berg², Frank Zijlstra¹, Marielle E Philippens², Stan Jelle Hoogcarspel², Jan J Lagendijk², Maximus A Viergever¹, and Marinus Adriaan Moerland^2
1Image Sciences Institute, University Medical Center Utrecht, Utrecht, Netherlands, ²Department of Radiotherapy, University Medical Center Utrecht, Netherlands

This study demonstrates the feasibility of in vivo MRI-based localisation of implanted brachytherapy seeds with positive contrast and high specificity, using a robust, clinically available imaging sequence with RASOR reconstruction and straightforward post-processing. This approach may enable MRI-only postimplant dosimetry, preventing the need for CT-based seed detection and image fusion and all related disadvantages, including radiation exposure, registration errors and additional costs. Interestingly, the optimized RASOR sequence facilitates visualisation of bone structures. As a consequence other applications of the proposed technique may be bone and fiducial imaging for MRI-based treatment planning in external beam radiotherapy and attenuation correction in PET-MRI.

Matteo Maspero¹, Peter R. Seevinck², Anna Andreychenko¹, Sjoerd Crijns¹, Alessandro Sbrizzi³, Max Viergever², Jan J. W. Lagendijk¹, and Cornelis A. T. van Den Berg^1
1Radiotherapy, UMC Utrecht, Utrecht, Utrecht, Netherlands, ²Image Sciences Institute, UMC Utrecht, Utrecht, Utrecht, Netherlands, ³Radiology, UMC Utrecht, Utrecht, Utrecht, Netherlands

This paper purposes an automatic method for bone segmentation in the pelvic region based on in-phase and out-of-phase images acquired on a reduced TE through the use of a custom designed spectral-spatial selective excitation pulse. A segmentation bone mask is obtained through a k-mean algorithm and compared with a similar mask calculated on reference in-phase and out-of-phase images. The suggested method shows an improvement in the false positive reduction in the bowel area compared to the reference bone mask and is eligible to produce good Digitally Reconstructed Radiography.

S. Ghose¹, D. Rivest Henault¹, J. Mitra¹, J. Sun², P. Pichler³, P. Greer³, and J. Dowling^4
1Australian e-Health Research Centre, CSIRO Digital Productivity Flagship, Herston, QLD, Australia, ²University of Newcastle, NSW, Australia, ³Department of Radiation Oncology, University of Newcastle, NSW, Australia, ⁴Australian e-Health Research Centre, CSIRO Digital Productivity Flagship, QLD, Australia

In this work, we propose to use a hybrid atlas and regression-based method to generate synthetic CT images from MRI for MRI based radiation therapy planning for prostate cancer treatment. Compared to a pure regression-based method, an additional UTE sequence is not required to segment the bone, and in comparison to a pure atlas-based method, we use regression-based soft tissue modeling, producing better soft tissue estimation. The proposed hybrid approach achieves a 0.6% dose difference compared to the use of original CT in the dose plan.

Wei Wang^1,2, Akila N Viswanathan², Antonio L Damato², Zion T Tse³, Yue Chen³, Ravi T Seethamraju⁴, Clare M Tempany¹, Robert A Cormack², and Ehud J Schmidt^1
1Radiology, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA, United States, ²Radiation Oncology, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA, United States, ³The University of Georgia, GA, United States, ⁴MR R&D, Siemens Healthcare, MA, United States

In interstitial brachytherapy, catheters are normally inserted into the tumor under MRI guidance. Due to the inaccuracy of MRI catheter visualization, CT is required after placement to localize catheters for treatment planning. We propose an adaptive radiation treatment planning process based entirely on MRI, using catheter trajectories generated by an active MR-tracking system specifically developed for fast and accurate localization of metallic catheters. This provides intra-operative dosimetric feedback to clinicians during catheter implantation, which allows for adaptive repositioning or addition of catheters. It will improve tumor coverage, reduce toxicity to normal tissues and potentially eliminate the need for subsequent CT.

Adrienne E Campbell-Washburn¹, Burcu Basar^1,2, Toby Rogers¹, Merdim Sonmez¹, Ozgur Kocaturk^1,2, Robert J Lederman¹, Michael S Hansen¹, and Anthony Z Faranesh^1
1Cardiovascular and Pulmonary Branch, Division of Intramural Research, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, MD, United States, ²Institute of Biomedical Engineering, Bogazici University, Istanbul, Turkey

MRI-guided procedures rely on the accurate visualization of devices. Here, a method was developed to isolate distinct signatures of the tip and the shaft of a passive nitinol guidewire with an iron oxide marker. A single spiral image was acquired, and reconstructed three times at three different frequencies (on-resonance and ±100Hz off-resonance). The characteristic dark-bright-dark pattern generated from magnitude image subtraction was used to isolate the iron oxide marker and the nitinol guidwire shaft was isolated from complex image subtraction. The tip and shaft are overlaid as two separate color channels on an anatomical image to assist procedural guidance.

Eugene G. Kholmovski^1,2, Ravi Ranjan², Nicolas Coulombe³, Joshua Silvernagel², and Nassir F. Marrouche^2
1UCAIR, Department of Radiology, University of Utah, Salt Lake City, Utah, United States, ²CARMA Center, University of Utah, Salt Lake City, Utah, United States, ³Medtronic CryoCath, Montreal, Quebec, Canada

Cardiac cryo-ablation is being increasingly used for treatment of atrial fibrillation and ventricular tachycardia. However, reported success rate of the procedures is moderate and serious complications have been observed. MRI has a potential to improve success rate of cardiac cryo-ablations and reduce complications. In this study, feasibility of real-time MRI guided cardiac cryo-ablation procedure was studied.

Yuichiro Matsuoka^1,2, Yoshinori Morita³, Yoshiki Hashioka⁴, Etsuko Kumamoto⁵, Hiromu Kutsumi², Takeshi Azuma², and Kagayaki Kuroda^6
1Center for Information and Neural Networks, National Institute of Information and Communications Technology, Suita, Japan, ²Department of Internal Medicine, Kobe University Graduate School of Medicine, Kobe, Japan, ³Department of Gastroenterology, Kobe University School of Medicine, Kobe, Japan,⁴Faculty of Engineering, Kobe University, Kobe, Japan, ⁵Information Science and Technology Center, Kobe University, Kobe, Japan, ⁶School of Information Science and Technology, Tokai University, Hiratsuka, Japan

An integrated MR-endoscope system that provides high quality MR images with an endoscopic view and information of the scope location has been developed to improve the accuracy and safety of endoscopy and endoscopic surgeries. To examine the feasibility of this system, the MR imaging of a gastric ulcer in animal experiments was conducted in vivo. Using an intra-cavitary RF coil for 1.5T-MRI with navigation, the gastric ulcer region was visualized in T1- and T2-weighted images with sufficient SNR and CNR. These MR images could correspond to a histological specimen of ulcer region. Therefore, the feasibility of this system was demonstrated.

Jason J Lamanna^1,2, Lindsey N Urquia¹, Carl V Hurtig¹, Juanmarco Gutierrez¹, Cody Anderson³, Pete Piferi⁴, Thais Federici¹, Nicholas M Boulis^1,2, and John N Oshinski^2,5
1Neurosurgery, Emory University, Atlanta, GA, United States, ²Biomedical Engineering, Emory University & Georgia Institute of Technology, Atlanta, GA, United States, ³Physics, Emory University, Atlanta, GA, United States, ⁴MRI Interventions, Inc., Memphis, TN, United States, ⁵Radiology, Emory University, Atlanta, GA, United States

Transplantation of cellular therapeutics to the spinal cord is conventionally done with either systemic administration, or local injection following surgical exposure of the spinal cord. For intraparenchymal transplantation, targeting to the spinal cord is based on a combination pre-operative MRI measurements and anatomical landmarks. Our group developed an MR-compatible spinal cord injection system capable of replacing invasive surgical procedures. Here we present the proof-of-principle for percutaneous, intraparenchymal transplantation of stem cells into the spinal cord of a live Gottingen minipig under MRI guidance.

Karl K Vigen¹, Deborah Rusy², Laura Buyan-Dent³, Nancy L Ninman³, and Karl A Sillay^4,5
1Radiology, University of Wisconsin-Madison, Madison, WI, United States, ²Anesthesiology, University of Wisconsin-Madison, Madison, WI, United States,³Neurology, University of Wisconsin-Madison, Madison, WI, United States, ⁴Semmes-Murphy Neurologic and Spine Institute, Memphis, TN, United States,⁵Neurosurgery and Electrical Engineering & Computer Science, University of Tennessee, Memphis, TN, United States

MRI-guided surgery for deep-brain stimulator (DBS) placement has emerged as a promising alternative for conventional awake DBS surgery. We report initial experience and the targeting accuracy of the procedure in an initial cohort of patients using a 70-cm bore MRI system in a purposely designed MR-OR suite.