Sina Marhabaie¹, Georges Willoquet¹, Rose-Marie Dubuisson¹, Bruno Quesson^2,3,4, and Marie Poirier-Quinot^1
1Université Paris-Saclay, BioMaps, Orsay, France, ²IHU L’Institut de RYthmologie et de Modélisation Cardiaque (LIRYC), Electrophysiology and Heart Modeling Institute, Fondation Bordeaux Université, 33600 Pessac, Bordeaux, France, ³Centre de recherche Cardio-Thoracique de Bordeaux, U1045, Université de Bordeaux, 33000, Bordeaux, France, ⁴INSERM, Centre de Recherche Cardio-Thoracique de Bordeaux, U1045, Université de Bordeaux, 33000, Bordeaux, France

Receive-only coils must be decoupled from the transmit coil during excitation. For conventional coils, decoupling is achieved using a resonant trap, which is switched during B1 transmit. However, in situations with very limited space like intravascular coils, this method remains problematic. We aimed to address efficient remote decoupling of a receive-only coil. We implemented an alternative approach by adding a “negative resistance” to the trap. This negative resistance is tailored in such a way that cancels out the positive resistance of the blocking trap, hence augmenting the quality factor of the trap and thus the decoupling efficiency.

Daniel Tewelde Gebrezgiabbhier^1,2, Hsin-Yu Chen³, Robert Bok³, Lucas Carvajal³, Matthew Cooperberg², Hao Nguyen², Katsuto Shinohara², Kimberly Okamoto³, Mary Frost³, Zhen Wang³, Michael Ohliger³, Jeremy Gordon³, Peder Larson³, Rahul Aggarwal², and Daniel Vigneron^3
1Bioengineering, University of California, San Francisco, CA, United States, ²School of Medicine, University of California, San Francisco, CA, United States, ³Radiology and Biomedical Imaging, University of California, San Francisco, CA, United States

A new ¹³C/¹H endorectal coil was designed, 3D printed, and manufactured with optimal dimensions to improve the comfort and tolerability for patients and provide higher SNR over the original endorectal coil used for over a decade. After bench and phantom tests, the new endorectal coil was applied in patient studies for mpMRI-TRUS guided fusion prostate biopsies with hyperpolarized C-13 pyruvate molecular imaging in three patients on active surveillance. The results of this novel approach with the new ¹³C/¹H coil provides an increase in sensitivity, image quality and ultimately supports better detection of lesions.

Adam Mitchell Maunder^1,2, Samuel Pichardo³, G. Bruce Pike³, Melany Mclean³, Fraser Robb⁴, Ashwin Iyer², and Nicola De Zanche^1,5
1Oncology, University of Alberta, Edmonton, AB, Canada, ²Electrical and Computer Engineering, University of Alberta, Edmonton, AB, Canada, ³Departments of Radiology and Clinical Neurosciences, Hotchkiss Brain Institute, University of Calgary, Calgary, AB, Canada, ⁴GE Healthcare Inc., Aurora, OH, United States, ⁵Medical Physics, Cross Cancer Institute, Edmonton, AB, Canada

The piezoelectric transducer array in magnetic resonance guided focused ultrasound shields the RF body-sized birdcage (BC) fields, leading to regions of low receive sensitivity that hinder MR thermometry and structural imaging. This work presents a flexible, acoustically transparent receive array consisting of dipole sections that mimic loops and are contained within the water bath of the ultrasound transducer array helmet surrounding the head. Adjacent elements are decoupled by shared current paths and lumped inductors. In simulation, the receive sensitivity is increased by 7.8-fold compared to a BC and causes a negligible alteration of the transmit field and specific absorption rate.

Eric Knull^1,2, Claire Park^2,3, Jeffrey Bax², David Tessier², and Aaron Fenster^1,2,3
1Biomedical Engineering, Western University, London, ON, Canada, ²Robarts Research Institute, London, ON, Canada, ³Medical Biophysics, Western University, London, ON, Canada

MRI-guided focal laser ablation (FLA) is a promising minimally-invasive therapy method for men with localized prostate cancer. We previously developed an MR-compatible mechatronic system capable of transperineal needle delivery within an in-bore 3T MRI environment. This work presents an improved multi-fiducial structure for robust registration of the mechatronic system for MRI-guided FLA needle delivery. Real-time MRI-guided needle delivery was performed in a tissue-mimicking prostate phantom to virtual targets simulating focal ablation zones. With the implementation of the improved multi-fiducial structure, mechatronics-assisted MRI-guided needle delivery enables a 1.44 mm ablation radius, showing potential utility for accurate FLA to small prostate lesions.

Manon Desclides^1,2,3, Guillaume Machinet⁴, Christophe Pierre⁴, Valéry Ozenne^1,3,5,6, Stéphane Chemouny², and Bruno Quesson^3,5,6
1UMR5536 CRMSB, Université de Bordeaux, Bordeaux, France, ²Certis Therapeutics, Pessac, France, ³IHU Liryc, Electrophysiology and Heart Modeling Institute, Hopital Xavier Arnozan, Pessac, France, ⁴ALPhANOV, Talence, France, ⁵Centre de Recherche Cardio-Thoracique de Bordeaux, U1045, University of Bordeaux, Bordeaux, France, ⁶INSERM, Centre de Recherche Cardio-Thoracique de Bordeaux, U1045, Bordeaux, France

We present here a new laser device allowing us to induce local temperature increase in several directions around the inserted probe to create conformational thermal ablation. The device incorporates 6 independent emitters illuminating several angles radially to the probe. We illustrate the capabilities of the device to create various heating shapes that can be visualized by real-time 2D multi-slice MR-thermometry.  

Nandita Saha¹, Andre Kuehne^2,3, Thomas Wilhelm Eigentler^1,4, and Thoralf Niendorf^1,2,5
1Berlin Ultrahigh Field Facility (B.U.F.F.), Max-Delbrück Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany, ²MRI.TOOLS GmbH, Berlin, Germany, ³MT MedTech Engineering GmbH, Berlin, Germany, ⁴Technische Universität Berlin, Chair of Medical Engineering, Berlin, Germany, ⁵Experimental and Clinical Research Center (ECRC), a joint cooperation between the Charité Medical Faculty and the Max-Delbrück Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany

This work proposes the concept of a loop and SGBT dipole antenna array for diagnostic proton (¹H) imaging and thermal intervention at 7.0T MRI. Dipole antennas are the general choice for RF induced heating application as they can be made to operate over a broadband frequency range, have symmetric B1+ field and provide a central E-field distribution. Adding the inherently orthogonal and thus well-decoupled electromagnetic (EM) fields of loops to the dipoles provides additional degrees of freedom for RF shimming and thermal intervention not afforded by only using dipole antennas.

Kemal Sumser¹, Gennaro G Bellizzi¹, Juan A Hernandez-Tamames², Gerard C van Rhoon¹, and Margarethus M Paulides^1,3
1Department of Radiotherapy, Erasmus Medical Center Rotterdam, Rotterdam, Netherlands, ²Department of Radiology and Nuclear Medicine, Erasmus Medical Center Rotterdam, Rotterdam, Netherlands, ³Department of Electrical Engineering, Eindhoven University of Technology, Eindhoven, Netherlands

In the head and neck region, precise heating and temperature monitoring is a challenge. The MRcollar, an MR compatible head and neck microwave hyperthermia applicator has been developed for conformal heating and to enable MR thermometry (MRT) during the treatment. To deliver on the needs of accurate temperature monitoring, the MRcollar has been equipped with 8-channel receiver coil array. This coil array improves increased the SNR by 5 times compared to the body coil of the MRcollar. Increase in the SNR also led to improvement in the MRT precision, from 0.91 °C to 0.37 °C.

Dominik Horstmann¹, Bennet Hensen¹, Karen Meyer zu Hartlage¹, Daniel Luca Reimert¹, Josef Joaquin Löning Caballero¹, Frank Wacker¹, and Marcel Gutberlet^1
1Hannover Medical School, Hannover, Germany

A 3D stack-of-stars MR-thermometry sequence was developed and evaluated during hepatic microwave ablation in a chicken phantom. A commercially available microwave generator (MWG) working in pulsed mode controlled by a temperature sensor was used. Results show a spatially dependent phase-offset in the MR-image only during active ablation mode of the pulsed MWG impairing thermometry. Consequently, 73% of thermometry data were discarded for the fixed phantom yielding a temperature precision of 0.72°C±0.60°C whereas 94% were discarded for the moving phantom with an accuracy of 1.08°C±1.25°C. For clinical MR-thermometry, an MWG with less EMI is required to improve resolution and temperature precision.

Dang Bich Thuy Le¹, Ram Narayanan¹, Meredith Sadinski¹, Kathryn Nicholas², Aleksandar Nacev¹, Dinesh Kumar¹, and Srirama Venkataraman^1
1Promaxo, Oakland, CA, United States, ²Lakeland Radiologists PA, Jackson, MS, United States

Haralick texture features extract frequencies of local spatial variations in signal intensity, quantifying pixel relationships within regions of interest. In this study, Haralick texture features were used to differentiate biopsy-proven, cancerous lesions from non-suspicious regions in low-field MR images. The results demonstrate consistency in texture measures for cancerous regions compared to non-suspicious, where Energy and Homogeneity are elevated while Contrast and Correlation are reduced within cancerous regions compared to non-suspicious regions.

Kilian A. Dietrich^1,2,3, Sebastian Klüter^2,4,5, Jürgen Debus^{1,2,3,4,5,6,7,8}, Fabian Dinkel⁹, Gernot Echner⁹, Mark E. Ladd^1,3,8, and Tanja Platt^1,2
1Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany, ²Department of Radiation Oncology, Heidelberg University, Heidelberg, Germany, ³Faculty of Physics, Heidelberg University, Heidelberg, Germany, ⁴National Center for Radiation Research in Oncology (NCRO), Heidelberg, Germany, ⁵Heidelberg Institute of Radiation Oncology (HIRO), Heidelberg, Germany, ⁶National Center for Tumor Diseases (NCT), Heidelberg, Germany, ⁷German Cancer Consortium (DKTK), Heidelberg, Germany, ⁸Faculty of Medicine, Heidelberg University, Heidelberg, Germany, ⁹German Cancer Research Center (DKFZ), Heidelberg, Germany

An RF body coil compatible with particle therapy was built for a clinical MR scanner at 1.5T with a rotatable patient capsule. The attenuation of ¹H⁺ and ¹²C⁶⁺ ions due to inelastic scattering was calculated for different materials to estimate the detrimental effects of the RF coil on the particle beam. The imaging capabilities could be demonstrated with phantom measurements at different flip angles, and corresponding transmit and receive characteristics were analyzed and compared to electromagnetic field simulations for both a horizontal and a tilted position of a phantom.

Isabellle Saniour¹, Victor Taracila², Fraser J.L. Robb², Rena Fukuda¹, Jana Vincent², Henning U. Voss¹, Michael G. Kaplitt³, J. Levi Chazen¹, and Simone Angela Winkler ^1
1Department of Radiology, Weill Cornell Medicine, New York, NY, United States, ²GE Healthcare, Aurora, OH, United States, ³Department of Neurological Surgery, Weill Cornell Medicine, New York, NY, United States

MRgFUS image quality remains poor and suffers from a low-signal band artifact, preventing efficient image acquisition. We propose to place overlapped acoustically transparent loop elements in “passive mode” between the transducer and the head that act as a transmit field repeater/concentrator. Simulation results not only show mitigation of the low-signal band artifact in the thalamus region, but also demonstrate improvement of the RF transmit signal by a factor of 5 and 2 in the upper brain and the thalamus region, respectively.