Wide-Bore 1.5 Tesla MR-System for Monitoring of Hepatic Radiofrequency Ablation: Initial Experience in the Treatment of 60 Metastases
Stephan Clasen¹, Hansjörg Rempp¹, Andreas Boss¹, Christina Schraml¹, Diethard Schmidt¹, Fritz Schick², Claus Claussen¹, Philippe Pereira^3
1Department of Diagnostic and Interventional Radiology, University of Tübingen, Tübingen, Germany; ²Section of Experimental Radiology, University of Tübingen, Tübingen, Germany; ³SLK Kliniken Heilbronn

MR-guided radiofrequency (RF) ablation using a wide-bore 1.5 Tesla MR-system was evaluated in the treatment of 60 hepatic metastases in 30 patients. Monitoring of ablation therapy was performed by using native T1w and T2w imaging. In addition MR temperature mapping by using the proton resonance frequency shift (PRF) method was applied. Complete coagulation was achieved in 58/60 (96.7%) metastases assessed during the mean follow-up of 5 months (range: 1 – 12 months). In conclusion, MR-guided RF ablation using a wide-bore 1.5 Tesla MR-system is an effective therapy in the local treatment of hepatic metastases.

Real-Time MR-Guided Biopsies to Target Focal Hepatic Fibrosis Detected with Magnetic Resonance Elastography
Ryan Babu Perumpail¹, Ning Jin¹, Yi Wang¹, Victoria Lee², Jennifer Karp¹, Bradley D. Bolster, Jr. ³, Saurabh Shah⁴, Sven Zuehlsdorff⁴, Richard Ehman⁵, Albert Andrew Nemcek¹, Josh Levitsky², Andrew Christian Larson¹, Frank Miller¹, Reed Ali Omary^1
1Radiology, Northwestern University, Chicago, IL, United States; ²Hepatology, Northwestern University, Chicago, IL, United States; ³Siemens Healthcare, Rochester, MN, United States; ⁴Siemens Healthcare, Chicago, IL, United States; ⁵Radiology, Mayo Clinic, Rochester, MN, United States

Magnetic resonance elastography (MRE), a non-invasive method to quantify liver stiffness, has not been directly correlated with MR-targeted biopsy results. We tested the hypothesis that real-time MR-guided biopsies could target focal segments of liver for histopathologic correlation with MRE stiffness measurements. Our results demonstrate the feasibility of real-time MR guidance to biopsy focal liver segments for correlation of fibrosis using MRE targets. Since early-stage hepatic fibrosis can present as focal lesions, MRE can be used to target biopsies to avoid clinical understaging and delayed initiation of therapy.

Preliminary Clinical Results: MR-HIFU Ablation of Uterine Fibroids with Automatic Volumetric Ablation
Charles Mougenot^1,2, Julia Enholm³, Nora Frulio⁴, Max O. Köhler³, Hervé Trillaud^4
1Philips Healthcare, Bordeaux, France; ²IMF laboratory, Bordeaux, France; ³Philips Healthcare, Vantaa, Finland; ⁴CHU Bordeaux, St André Hospital, Bordeaux, France

High Intensity Focused Ultrasound under MR guidance is a non-invasive thermotherapy procedure used for ablation of uterine fibroids. To improve this treatment, a volumetric heating method combined with temperature control was evaluated at St. André hospital following good clinical practice and using a Philips MR-HIFU platform. Preliminary results based on 13 clinical cases indicate that large volumetric sonications increase the ablation efficiency by a ratio 35. In addition, temperature control provides a reproducible ablation size with a diameter accuracy of 1mm, which enhances treatment safety. No serious adverse events or skin burns were observed.

Interactive Mr-Guided Percutaneous Nephrostomy Using an Open 1T Mr-Scanner: First Experience in 15 Patients
Frank Fischbach¹, Markus Porsch, Jürgen Bunke², Maciej Pech, Oliver Dudeck, Uwe-Bernd Liehr, Jens Ricke
¹OvGU, Magdeburg, Germany, Germany; ²PMS

The advantages of MR fluoroscopy including missing radiation, high tissue contrast, multiplanar imaging and the availability  of open high field systems giving good access to the patient and sufficient SNR should encourage broadening the indications for MR-guided interventions. MR-guided percutaneous nephrostomy can be performed in a routine setting. This is especially of interest in patients not suited for sonographic guidance

Transrectal MRI-Guided Biopsy of the Prostate - Results in a Cohort with 100 Patients with Negative Ultrasound Guided Biopsy and Persisting or Increasing PSA Levels
Matthias C. Roethke¹, David Schilling², Aristotelis G. Anastasiadis³, Matthias P. Lichy, Arnulf Stenzl², Claus D. Claussen, Heinz-Peter Schlemmer^1
1Diagnostic Radiology, University Hospital, Tuebingen, Germany; ²Urology, University Hospital, Tuebingen, Germany; ³Urology, Grossburgwedel Hospital, Germany

Transrectal MRI-guided biopsy of the prostate in a cohort with 100 patients with prior negative ultrasound guided biopsy and persisting or increasing PSA levels. Results show detection rate of MRI-guided biopsy(49%)is considerably higher compared to standard repetition procedure with transrectal ultrasound guided biopsy (up to 26% even after saturation biopsy).

Preliminary Human Evaluation of MRI-Guided Transurethral Ultrasound Therapy for the Treatment of Localized Prostate Cancer
Rajiv Chopra^1,2, Michael Bronskill^1,2, Masoom Haider^3,4, Laurence Klotz^5,6
1Imaging Research, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada; ²Medical Biophysics, University of Toronto, Toronto, Ontario, Canada; ³Medical Imaging, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada; ⁴Medical Imaging, University of Toronto, Toronto, Ontario, Canada; ⁵Urology, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada; ⁶Surgery, University of Toronto, Toronto, Ontario, Canada

MRI-guided transurethral ultrasound therapy is a minimally-invasive treatment for localized prostate cancer. The purpose of this study was to evaluate the feasibility of performing this treatment in humans. An initial clinical evaluation in prostate cancer patients destined for radical prostatectomy was performed. The predicted thermal damage zone was compared with the actual tissue damage measured on histology.

Online Guidance of Tumor Targeted Prostate Brachytherapy Using Histologically Referenced MRI
Cynthia Menard¹, Peter Chung, Jessamine Abed, Anna Simeonov, Jenny Lee, Kristy Brock, Warren Foltz, Gerald O'Leary², Christine Elliott³, Michael Milosevic, Robert Bristow, Gerard Morton⁴, Padraig Warde, Masoom Haider
¹Princess Margaret Hospital, University of Toronto, Toronto, Ontario, Canada; ²Toronto General Hospital, University Health Network; ³Sentinelle Medical Inc; ⁴Odette Cancer Center, University of Toronto

We demonstrate feasibility and report technical and clinical performance of a needle navigation system where pathologically referenced multi-parametric interventional MRI guidance improved the determination of tumor boundaries, and enabled accurate tumor-targeted HDR prostate brachytherapy. The value of 3D imaging to document actual location of biopsy cores in reference to anatomic boundaries is emphasized.

Localizing Prostate Brachytherapy Seeds with SGM
Gopal Varma¹, Peter Acher², Graeme Penney¹, Kawal Rhode¹, Stephen Keevil^1,3, Tobias Schaeffter^1
1Imaging Sciences, King's College London, London, United Kingdom; ²Department of Urology, Guy's and St Thomas' NHS Foundation Trust, London, United Kingdom; ³Medical Physics, Guy's and St Thomas' NHS Foundation Trust, London, United Kingdom

Treatment by prostate brachytherapy involves implant of radioactive seeds. Dosimetry requires seed position and number to be accurately defined relative to prostate anatomy. The advantage of soft tissue contrast from MRI allows depiction of the prostate but localization of the seeds is relatively poor.  A SGM technique is used to visualize the seeds by post-processing. The derived parameter is found to have a linear correlation with number of seeds and thus provides potential for dosimetry by MR.

Proof of Principle of an MR-Compatible Robot for MRI-Guided Interventions Using a Unique Tapping Device
Michiel R. van den Bosch¹, Maaike R. Moman¹, Marco van Vulpen¹, Jan J. Battermann¹, Ed Duiveman², Leonard J. van Schelven², Jan J.W Lagendijk¹, Marinus A. Moerland^1
1Department of Radiotherapy, University Medical Center Utrecht, Utrecht, Netherlands; ²Medical Technology & Clinical Physics, University Medical Center Utrecht, Utrecht, Netherlands

This in-vivo study demonstrates the proof of principle of an MR-compatible robot dedicated for MRI-guided interventions. The robot can be placed between patient's legs inside a 1.5T closed bore scanner for transperineal needle insertion. To minimize tissue deformation, it contains a tapping device to automatically tap (rather than push) the needle towards the target position. Four fiducial gold markers were placed into the prostate of a patient with a stage T3 prostate cancer under MRI-guidance using fast MR sequences. This opens the door for MRI-guided interventions as biopsy and brachytherapy in tissue, where deformation might be problematic.

MR-Compatible Transrectal Prostate Biopsy Robot: A Feasibility Study
Jurgen Futterer¹, Martijn Schouten¹, Tom Scheenen², Jelle Barentsz^3
1Radiology, Radboud University Nijmegen Medical Centre, Nijmegen, Netherlands; ²Radiology, Radboud University Nijmegen Medical Centre, Nijmegen, Netherlands; ³Radiology, Radboud University Nijmegen Medical Centre, Nijmegen, Netherlands

The meet the demand of a better sensitivity in MR-guided biopsy of the prostate the robotic system can be employed. We introduce the in-house developed pneumatic actuated MR-compatible robot where needle guide direction can be controlled inside the controller room. Feasibility and accuracy of the MR-compatible robot were validated with phantom measurements.