Wending Tang¹, Xing Wei², Muheng Li¹, Fuyixue Wang^3,4, Zijing Dong^3,5, Danna Wei⁶, Kawin Setsompop^3,4,5, and Karen Ying^1
1Department of Engineering Physics, Tsinghua University, Beijing, China, ²Orthopedic Department, Aerospace Center Hospital, Beijing, China, ³Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, United States, ⁴Harvard-MIT Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, MA, United States, ⁵Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA, United States, ⁶Department of Biomedical Engineering, School of Medicine, Tsinghua University, Beijing, China

Proton resonance frequency (PRF) of water protons is widely utilized in MR thermometry. EPI sequence is often used to speed up  the imaging rate, but suffers from geometric distortion and blurring. Here we proposed a rapid temperature mapping method through the EPTI sequence. EPTI sequence is a new multi-shot EPI technique capable of rapidly obtaining distortion-free images. Via this method, greater speed is achieved for monitoring temperature, which makes real-time temperature mapping possible.

Waqas Majeed¹, Sunil Patil¹, Pan Su¹, Rainer Schneider², Henrik Odéen³, Dennis L. Parker³, John Roberts³, Jiachen Zhuo⁴, and Himanshu Bhat^1
1Siemens Medical Solutions USA Inc., Malvern, PA, United States, ²Siemens Healthcare GmbH, Erlangen, Germany, ³Department of Radiology and Imaging Sciences, University of Utah, Salt Lake City, UT, United States, ⁴Department of Diagnostic Radiology and Nuclear Medicine, University of Maryland School of Medicine, Baltimore, MD, United States

Anatomical misregistration and background phase variation due to physiological motion are two major sources of inaccuracy in PRF thermometry of the liver. We propose a pipeline consisting of 3D segmented EPI acquisition, 3D deformable motion correction and PCA-based background phase correction for liver thermometry. 3D acquisition results in an increase in SNR and makes 3D registration possible. PCA-based background phase correction improves ΔT quality over a more commonly used dictionary-based method. The proposed pipeline was used to achieve 75th percentile ΔT bias and standard deviation values of 1.70°C and 1.65°C respectively over whole-liver in one healthy volunteer. 

Yekaterina K Gilbo¹, Helen Sporkin², Samuel W Fielden³, John P Mugler⁴, Grady W Miller⁴, Steven P Allen², and Craig H Meyer^2
1University of Virginia, Charlottesville, VA, United States, ²Biomedical Engineering, University of Virginia, Charlottesville, VA, United States, ³Department of Imaging Sciences & Innovation, Geisenger, Danville, PA, United States, ⁴Radiology and Medical Imaging, University of Virginia, Charlottesville, VA, United States

Skull temperature monitoring is important for MR-guided focused ultrasound (MRgFUS), as the skull is highly absorptive to acoustic energy. T1 thermometry uses T1 mapping to observe a linear increase in T1 with temperature but requires long acquisitions. Here we compare T1-weighted thermometry with T1 thermometry using a 3D spiral ultra-short-echo time sequence and show that T1 thermometry is feasible, but requires further acceleration, whereas T1-weighted thermometry results are nonlinear and inconsistent.

Pei Han^1,2, Fei Han³, Debiao Li^1,2,4, Anthony Christodoulou², and Zhaoyang Fan^1,2,4
1Department of Bioengineering, UCLA, Los Angeles, CA, United States, ²Biomedical Imaging Research Institute, Cedars-Sinai Medical Center, Los Angeles, CA, United States, ³Siemens Healthineers, Los Angeles, CA, United States, ⁴Department of Medicine, UCLA, Los Angeles, CA, United States

A new real-time imaging scheme is proposed based on low-rank spatiotemporal decomposition. Briefly, a high-quality spatial subspace and a direct linear mapping from k-space navigator data to subspace coordinates are first learned from a “demo” scan. In the subsequent “live” scan, successive real-time images can be generated by a fast matrix multiplication procedure on a single instance of the k-space navigator readout (e.g. a single k-space line), which can be acquired at a high temporal rate. The method was demonstrated in vivo using a T1-T2 abdominal multitasking sequence.

Shenyan Zong^1,2, Chang-Sheng Mei³, Guofeng Shen¹, and Bruno Madore^2
1Biomedical Instrument Institute, School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China, ²Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, United States, ³Department of Physics, Soochow University, Taipei, Taiwan

It has been shown that spatial gradients in the background phase of an image can cause artifacts/errors in MRI temperature measurement. In the present work, a reconstruction method called 'k-space energy spectrum analysis' (KESA), originally developed in the context of partial-Fourier imaging, is adapted and tested here for its ability to correct for this particular problem. Compared to the previously-published image-based method already available for this purpose, the present k-space based method proved considerably more robust in the presence of high levels of noise, as tested with phantom data.

Laura Gui¹, Orane Lorton¹, Max Scheffler², and Rares Salomir^1,2
1Image Guided Interventions Laboratory, Faculty of Medicine, University of Geneva, Geneva, Switzerland, ²Department of Radiology, University Hospitals of Geneva, Geneva, Switzerland

Magnetic resonance thermometry via the classic time-referenced PRFS method is perturbed by tissue motion and external magnetic field perturbations. We extend an existing 2-D reference-free PRFS thermometry method to 3-D data, by performing near-harmonic reconstruction of the background phase inside a sphere. Ex-vivo HIFU sonication experiments and in-vivo “zero-measurement” of a human brain showed good method accuracy and precision, fast computation times and similar results with the time-referenced PRFS method for motion-free scenarios. This study demonstrates the method’s feasibility for real time thermometry of moving tissues.  

Kagayaki Kuroda¹, Satoshi Yatsushiro¹, Yuta Hiranobu¹, Takuya Watanabe¹, Toru Niwa², and Yutaka Imai^2
1Department of Human and Information Sciences, School of Information Science and Technology, Tokai University, Hiratsuka, Japan, ²Department of Radiology, School of Medicine, Tokai University, Isehara, Japan

An practical MR thermometry technique for fat-water mixed tissues was proposed. Fatty tissue temperature was quantified by T₂ synthesized from T₂’s of methylene chain and terminal methyl obtained by chemical shift suppression of water and surrounding fatty acid components. While the aqueous tissue temperature was estimated by PRF shift of water proton. Those maps were then integrated into one based on the fat and water contents in each voxel. The resultant in vitro images demonstrated the usefulness of the technique.

Boyu Zhang¹, Xianfu Meng², Yuwen Zhang¹, Wenbo Bu², and He Wang^1,3
1Institute of Science and Technology for Brain-Inspired Intelligence, Fudan University, Shanghai, China, ²School of Chemistry and Molecular Engineering, East China Normal University, Shanghai, China, ³Human Phenome Institute, Fudan University, Shanghai, China

It is a challenge that accurate monitoring the spatial distribution of photothermal transducing agents (PTAs), meanwhile, real-time mapping temperature in photothermal therapy. Here, we propose an effective strategy that integrates T1 and MR temperature imaging for tracking nanoPTAs and real-time temperature monitoring in vivo. The synthesized nanoPTAs equip with favorable T1 performance and marginal susceptibility guaranteeing the accuracy of temperature mapping. The time resolution is 20 seconds, and the detection accuracy of temperature change is as low as 0.1K, which contributes to promoting the clinical application of photothermal therapy.

Saikat Sengupta¹ and Xinqiang Yan^1
1Department of Radiology, Vanderbilt University Institute of Imaging Science, Nashville, TN, United States

Artifacts caused by large magnetic susceptibility differences between metallic probes and the surrounding tissue are a persistent problem in interventional MRI. In 2019, we presented the concept, design and modeling of active shims for metallic probes inspired from naval degaussing systems. Field disturbance induced by a metallic probe at 3 Tesla was modeled and an active shim insert design was presented to shim the field variation around the probe. In this abstract we present the first experimental results showing effective recovery of metallic probe induced signal loss at 3 Tesla.

Andrew Dupuis¹, Dan Ma², and Mark A Griswold^1,2
1Biomedical Engineering, Case Western Reserve University, Cleveland, OH, United States, ²Department of Radiology, School of Medicine, Case Western Reserve University, Cleveland, OH, United States

We implemented an augmented reality (AR) scanner interface in order to streamline the scanner console while allowing users to work natively in three dimensions. The Microsoft Hololens was leveraged to allow users to visualize and control the scanner wirelessly. A gesture based interface was created, with emphasis placed on simplification of the scan process to help untrained non-imaging personnel to interact with the scanner. The resulting system is simple to use and allows the operator to maintain direct sight of the patient throughout the scan. 

Megan E Poorman^1,2, Rasim Boyacioglu³, William A Grissom⁴, Mark A Griswold³, and Kathryn E Keenan^1
1Physical Measurement Laboratory, National Institute of Standards and Technology, Boulder, CO, United States, ²Department of Physics, University of Colorado Boulder, Boulder, CO, United States, ³Department of Radiology, Case Western Reserve Univeristy, Cleveland, OH, United States, ⁴Vanderbilt University Institute of Imaging Science, Nashville, TN, United States

Temperature monitoring in both adipose and aqueous tissues is important for guidance of thermal therapies in vivo. However, the proton resonant frequency shift for thermometry is only reliable in aqueous tissues. Temperature mapping in adipose has been explored using relaxation, but is limited by the accuracy and speed of the method used. MR Fingerprinting provides a framework for mapping differences due to multiple tissue properties simultaneously. This work explores adapting the MRF framework to allow temperature changes to be mapped directly in all tissue types, and simulates a dictionary update method that could offer improved temporal resolution over standard MRF.

Chang-Sheng Mei¹, Shenyan Zong^2,3, Sheng Chen⁴, Guofeng Shen³, and Bruno Madore^2
1Department of Physics, Soochow University, Taipei, Taiwan, ²Department of Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, United States, ³Biomedical Instrument Institute, School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China, ⁴Shanghai Shende Medical Technology Co., Ltd, Shanghai, China

The proton resonance frequency (PRF) shift, whereby the Larmor frequency varies with temperature, is the effect that enables most currently-employed MR thermometry methods. The present work aimed to demonstrate that such temperature-related frequency changes can also cause non-negligible spatial distortions in single-shot EPI. In addition to demonstrating the effect, a solution is also proposed here. Phantom experiments are presented that demonstrate the problem and its solution.

Eva Oberacker¹, Andre Kuehne², Thomas Wilhelm Eigentler¹, Cecilia Diesch¹, Jacek Nadobny³, Pirus Ghadjar³, Peter Wust³, and Thoralf Niendorf^1,2,4
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, ³Clinic for Radiation Oncology, Charité Universitätsmedizin, Berlin, Germany, ⁴Experimental and Clinical Research Center (ECRC), joint cooperation between the Charité Medical Faculty and the Max-Delbrück-Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany

Ultrahigh field (UHF) MR employs higher radio frequencies (RF) than conventional MR and has unique potential to provide focal temperature manipulation and high resolution imaging (ThermalMR), as our simulations and experimental work demonstrated for f=300MHz. Here we use EMF simulations to demonstrate the added value for multi-frequency thermal intervention (f=300MHz-500MHz) to boost the efficacy of the heating paradigm for clinical target volumes (TVs) of two brain tumor patients. An optimization algorithm was developed to study RF power deposition in the TV for a single, double or triple frequency set permitting highest RF power deposition in the TV.

Dara Kraitchman¹, Cory Brayton¹, Rebecca Krimins¹, Byung-Hak Kang¹, Zachary Millman¹, Edward McCarthy¹, and Brian Ladle^1
1Johns Hopkins University School of Medicine, Baltimore, MD, United States

Improvements in outcomes with current chemotherapy and surgery treatment approaches for patients with osteosarcoma have plateaued over the past three decades necessitating new treatment paradigms. A novel therapy for osteosarcoma of MR-guided cryotherapy in conjunction with intratumoral injection of an immune adjuvant in the clinically relevant animal model of spontaneously occurring osteosarcoma in client-owned dogs with the intent of priming an adaptive immune response capable of delaying or preventing the occurrence of metastatic disease is demonstrated.

Aiming Lu¹, David A Woodrum¹, Christopher P Favazza¹, Joel P Felmlee¹, Brian T Welch¹, Jacinta Browne¹, and Krzysztof R Gorny^1
1Radiology, Mayo Clinic, Rochester, MN, United States

MRI-guided cryoablation is a promising minimal invasive approach to treat localized tumors. Since the cryoneedles used in this system are metallic and the gas lines have metallic components, RF heating could occur during MR imaging. Our phantom study demonstrated temperature increase of more than 100 °C due to a sequence with moderate SAR of 2.1W/kg.In this work, we demonstrate that RF heating caused by the real-time monitoring MRI sequence could potentially affect the temperature course near the cryoneedles and therefore affect the treatment efficacy, especially when angiocath was used to aid the cryoneedle placement.

Xiaoyan Huang¹, Yufu Zhou¹, and Bensheng Qiu^1
1University of Science and Technology of China, Hefei, China

A novel MR-compatible microwave needle is proposed to achieve spherical ablation and monitor the temperature of needle shaft. It has an asymmetrical dipole choke with titanium alloy tube and a conical tip made of solid zirconia to facilitate needle insertion into tissues. FDTD simulations are used to minimize reflection coefficient and maximize aspect ratio. This most optimal design was validated in ex vivo pork liver in a 0.7T open MR system and concluded an acceptable artifacts, reflection coefficient of -27.86 dB and near-spherical ablation zone with a length of 39.5 mm, a diameter of 34.5 mm at 50W, 5 min.

Thomas Lilieholm¹, Alan McMillan^1,2, Fang Liu¹, Robert Moskwa¹, Azam Ahmed³, and Walter F Block^1,2,4
1Medical Physics, University of Wisconsin - Madison, Madison, WI, United States, ²Radiology, University of Wisconsin - Madison, Madison, WI, United States, ³Neurological Surgery, University of Wisconsin - Madison, Madison, WI, United States, ⁴Biomedical Engineering, University of Wisconsin - Madison, Madison, WI, United States

Improved image guidance is needed for neurosurgeons to reduce the residual remaining clot levels during minimally invasive evacuation of intracerebral hemorrhage (ICH) while not causing rebleeds. Neurosurgeons would benefit from a means to periodically render the clot volume against surrounding normal tissue during mechanical evacuation or pharmaceutical-based clot-busting. Using convolutional neural networks (CNN), we created machine learning models  to automatically segment the constituent clot and edema induced by ICH cases using T2-weighted MR images. The CCN’s output results were found to be in agreement with manual segmentations of the same ICH cases.

Dogangun Uzun¹ and Ozgur Kocaturk^1
1Institute of Biomedical Engineering, Bogazici University, Istanbul, Turkey

In this work, a novel design fiber optic force sensor with increased resolution thru Titanium coating is fabricated using Fabry-Pérot Interferometry (FPI) method and integrated into a biopsy needle to be used in interventional biopsy operations under MRI. The FPI based force sensor with improved resolution is tested via benchtop experiments after integrating into a MRI compatible biopsy needle. Sensor’s penetration detection, tissue characterization and differentiation capabilities are tested using different types of tissues. Overall system performance is tested via in vitro experiments under MRI using a commercial prostate phantom with leisons. 

Xinzhou Li^1,2, Yu-Hsiu Lee³, Tsu-Chin Tsao³, and Holden H. Wu^1,2
1Radiological Sciences, University of California, Los Angeles, Los Angeles, CA, United States, ²Bioengineering, University of California, Los Angeles, Los Angeles, CA, United States, ³Mechanical and Aerospace Engineering, University of California, Los Angeles, Los Angeles, CA, United States

Discrepancy between the physical needle location and the MRI passive needle feature could lead to needle localization errors in MRI-guided percutaneous interventions. By leveraging physics-based simulations with different needle orientations and MR imaging parameters, we designed and trained a Mask Regional Convolutional Neural Network (R-CNN) to automatically localize the physical needle tip and axis orientation based on the MRI passive needle feature. The Mask R-CNN framework was tested on a separate set of actual phantom MR images and achieved physical needle localization with median tip error of 0.74 mm and median axis error of 0.95°.

Orso Andrea Pusterla^1,2,3, Francesco Santini^2,3, Grzgorz Bauman^2,3, Rahel Heule⁴, Alina Giger³, Philippe Claude Cattin³, Sairos Safai⁵, Sebastian Kozerke¹, and Oliver Bieri^2,3
1Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland, ²Department of Radiology, Division of Radiological Physics, University Hospital Basel, Basel, Switzerland, ³Department of Biomedical Engineering, University of Basel, Allschwil, Switzerland, ⁴High Field Magnetic Resonance, Max Planck Institute for Biological Cybernetics, Tübingen, Germany, ⁵Center for Proton Therapy, Paul Scherrer Institute, Villigen-PSI, Switzerland

Time-resolved volumetric imaging (4D-MRI) of moving organs is essential for several clinical applications, e.g., in interventional treatments, radiation therapies, and high-intensity focused ultrasound ablations. In this work, an interleaved time-resolved data-navigator acquisition strategy for 4D-MRI with flexible contrast is developed offering versatile settings for thoracic and abdominal imaging: for both, image and navigator, not only the flip angle but also the basic acquisition type (pulse sequence kernel) can be chosen independently from either balanced SSFP (i.e., T₂/T₁-weighted) or spoiled gradient echo (i.e., T₁-weighted).

Paul Zhi Yuan Liu¹, Urszula Jelen², Bin Dong², Gary Liney², and Paul Keall^1
1Image X Institute, The University of Sydney, The University of Sydney, Australia, ²Department of Medical Physics, Ingham Institute for Applied Medical Research, Liverpool, Australia

A real-time tumor tracking system has been developed for MRI-guided radiation therapy.  This system allows for tumor motion to be monitored during radiotherapy and for the radiation beam to be modified to compensate for this motion. The tumor location was found during treatment through the use of a template matching algorithm and 2D cine-MR images. The tumor location information was sent to a tracking algorithm that modifies the shape of the beam in real-time to ensure the tumor target is irradiated. The tumor tracking system has been tested and found to be of submilimeter accuracy.

Dongsuk Sung¹, Peter A. Kottke², Jason W. Allen^3,4, Fadi Nahab⁴, Andrei G. Fedorov^2,5, and Candace C. Fleischer^1,3,5
1Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, United States, ²Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, United States, ³Department of Radiology and Imaging Sciences, Emory University School of Medicine, Atlanta, GA, United States, ⁴Department of Neurology, Emory University School of Medicine, Atlanta, GA, United States, ⁵Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA, United States

Brain temperature regulation is a key parameter after injury and ischemia. Experimental magnetic resonance (MR)-based thermometry is promising but not always clinically feasible. To complement MR thermometry measures, an improved thermal model of the brain based on first principles has been developed that rigorously ensures energy conservation in thermally interacting brain domains. As initial validation, a temperature map was generated using our model with MR angiography (MRA) and structural MR imaging (MRI) data, and compared with experimental chemical shift thermometry (CST) in the same subject. Biophysical models provide further insight into brain thermoregulation by complementing experimental thermometry measurements.

Robin Navest^1,2, Stefano Mandija^1,2, Bjorn Stemkens¹, Stefan Zijlema^1,2, Anna Andreychenko^1,3, Jan Lagendijk¹, and Cornelis van den Berg^1,2
1Radiotherapy, UMC Utrecht, Utrecht, Netherlands, ²Computational Imaging Group for MRI Diagnostics & Therapy, Center for Image Sciences, UMC Utrecht, Utrecht, Netherlands, ³Research and Practical Clinical Center of Diagnostics and Telemedicine Technologies of the Moscow Department of Healthcare, Moscow, Russian Federation

The noise navigator provides physiological motion detection completely independent of the imaging volume or contrast of the MR images and can be acquired on a much faster (millisecond) time scale than MRI. We believe that the noise navigator can be used as an independent verification method to detect the occurrence of motion in synergy with real-time MRI-guided radiotherapy and standalone during e.g. recontouring when typically no MRI is performed. For abdominothoracic radiotherapy, we investigated bulk motion and variable breathing as these have a relatively large amplitude (millimeters). Additionally, swallowing detection was investigated given its complications for head-and-neck radiotherapy.

Suzanne Lydiard^1,2, Beau Pontre³, Boris Lowe², and Paul Keall^1
1ACRF ImageX Institute, University of Sydney, Sydney, Australia, ²Auckland City Hospital, Auckland, New Zealand, ³University of Auckland, Auckland, New Zealand

Cardiac radiosurgery for atrial fibrillation (AF) is challenging; the target moves with both cardiac contraction and respiration and is in close proximity to critical structures. This study utilized non-contrast MRI to characterize AF cardiac radiosurgery target motion as well as relative target displacement to surrounding structures. The absolute and relative target motion seen in this study in combination with target proximity to the aorta and esophagus highlights the importance of carefully selecting cardiac radiosurgery technology and techniques. This MRI-based methodology could be useful in the AF cardiac radiosurgery clinical workflow to optimize treatment for the individual.

Christoph Leuze¹, Supriya Sathyanarayana¹, Mahendra T Bhati², Noriah D Johnson², Christopher C Cline^2,3, Trishia El Chemaly¹, Bruce Daniel¹, Aapo Nummenmaa^4,5, Amit Etkin², and Jennifer A McNab^1
1Radiology, Stanford University, Stanford, CA, United States, ²Psychiatry, Stanford University, Stanford, CA, United States, ³MIRECC, VA Palo Alto Health Care System, Palo Alto, CA, United States, ⁴Neuroscience, Massachusetts General Hospital, Charlestown, MA, United States, ⁵Radiology, Harvard Medical School, Charlestown, MA, United States

Transcranial magnetic stimulation (TMS) treatment is an important non-invasive treatment option for depressive patients who do not respond to medication. Effective TMS treatment is dependent on accurate stimulation intensity calibration and coil positioning, which is best achieved through image-based neuronavigation. Unfortunately, most TMS treatments use generalized scalp measurements, which are faster and cheaper but less accurate and less effective than image-based neuronavigation. We present a mixed reality neuronavigation system that allows the clinician to view brain MRI and targeting information superimposed on the patient’s head for an accelerated and simplified procedure

Simon Stephan¹, Simon Reiss¹, Thomas Lottner¹, Ali Caglar Özen¹, and Michael Bock^1
1Dept. of Radiology, Medical Physics, Medical Center University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany, Freiburg, Germany

For quantitative myocardial perfusion measurements with intra-arterial contrast agent (CA) injection precise knowledge of the arterial input function (AIF) is needed. Not necessarily absolute values of the AIF are needed if blood flow measurements are used to normalize the perfusion maps. In this work it is shown for a constant-flow phantom that this method works and probable issues for transferring the method to in-vivo measurements are discussed.

Aaron E Rusheen^1,2, Elise M Berning¹, Dane T Bothun¹, Ben T Gifford¹, Stephan J Goerss¹, Kirk M Welker³, John Huston³, Kevin E Bennet^1,4, Yoonbae Oh^1,5, Charles D Blaha¹, Kendall H Lee^1,5, and Fagan J Andrew^3
1Department of Neurosurgery, Mayo Clinic, Rochester, MN, United States, ²Medical Scientist Training Program, Mayo Clinic, Rochester, MN, United States, ³Department of Radiology, Mayo Clinic, Rochester, MN, United States, ⁴Department of Engineering, Mayo Clinic, Rochester, MN, United States, ⁵Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN, United States

7.0T MRI provides precise visualization and targeting of brain structures for image-guided stereotactic neurosurgery. However, image localizers used by stereotactic systems do not exist for 7.0T scanners. Challenges in their development include: the small bore creates geometric constraints that disallow use of conventional localizers, and the increased B₀ increases geometric distortion, affecting registration accuracy. Here, a skull-contoured localizer utilizing point fiducials was designed to attach to a novel stereotactic frame. Extracranial distortion was thoroughly mapped using several optimized imaging sequences. This data was used to optimally place fiducials on the localizer, improving registration accuracy. 

Lin Chen^1,2, Jing Liu^1,3, Chengyan Chu^1,4, Nirhbay Yadav^1,2, Jiadi Xu^1,2, Monica Pearl¹, Piotr Walczak^1,4, Peter van Zijl^1,2, Miroslaw Janowski⁴, and Guanshu Liu^1,2
1Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, MD, United States, ²F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Research Institute, Baltimore, MD, United States, ³The First Affiliated Hospital of Jinan University, Guangzhou, China, ⁴Department of Diagnostic Radiology and Nuclear Medicine, University of Maryland, Baltimore, MD, United States

The use of contrast media, such as Gadolinium-based contrast agents (GBCA), superparamagnetic iron oxide particles (SPIO) and carbon dioxide, can improve the conspicuity of MRI, thereby helping to improve the accuracy of transcathether infusions during endovascular neurointerventions. In this study, we exploited deuterium oxide (D₂O) as a new MRI contrast medium for guiding intra-arterial hyperosmotic blood brain barrier (BBB) opening in experimental animal models. Compared to the SPIO-based approach, D₂O MRI guidance was found to provide comparable results that can predict the territory of BBB opening (assessed by Gd-MRI).

Keerthi Sravan Ravi^1,2, Sairam Geethanath², Patrick Quarterman³, Maggie Fung³, and John Thomas Vaughan Jr.^2
1Biomedical Engineering, Columbia University, New York, NY, United States, ²Columbia University Magnetic Resonance Research Center, Columbia University, New York, NY, United States, ³GE Healthcare Applied Sciences Laboratory East, New York, NY, United States

MR Value can be interpreted as the ratio of image contrast to acquisition time. This can be maximised via intelligent protocolling that chooses an optimal combination of pulse sequence parameters. In this work, a Look Up Table (LUT) is consulted to obtain parameters that satisfy an acquisition time constraint. The LUT is populated with data collected from a vendor’s simulator, and a search algorithm is designed to prioritise preserving image contrast and achieving high through-plane resolution. Data is collected across four experiments from a healthy volunteer. LUT-derived and measured relative SNR values are compared and analysed.

Jhimli Mitra¹, Sydney Jupitz², Bryan Bednarz², James H. Holmes³, David Mills¹, Lowell Scott Smith¹, Heather Chan¹, Aqsa Patel¹, Eric Fiveland¹, Warren Lee¹, Alan McMillan³, Wes Culberson², Michael Bassetti⁴, Andrew Shepard², Shourya Sarcar¹, and Thomas K. Foo^1
1General Electric Research, Niskayuna, NY, United States, ²Medical Physics, University of Wisconsin - Madison, Madison, WI, United States, ³Radiology, University of Wisconsin - Madison, Madison, WI, United States, ⁴Human Oncology, University of Wisconsin - Madison, Madison, WI, United States

An MR-compatible ultrasound probe was developed for hands-free, simultaneous MR-ultrasound image acquisition for image-guided radiation therapy in liver. Simultaneously acquired pre-treatment MR and U/S associates a pair of MR image and U/S volume to each respiratory state over multiple respiratory cycles without requiring physical MR image acquisition during the radiation treatment LINAC phase. Automatic fiducial tracking and respiratory state clustering were performed on the U/S volumes to determine expiration states for dose delivery. In a test-retest analysis, consistent and reproducible expiration states were obtained that can be used for targeted-dose delivery under LINAC.

Christof Böhm¹, Dominik Weidlich¹, Sophia Kronthaler¹, and Dimitrios C. Karampinos^1
1TUM, Munich, Germany

Climate change is one of the defining issues of our time. Weather patterns are shifting and sea levels are rising. The most abundant greenhouse gas, accounting for about two-thirds of total greenhouse gas emissions, is carbon dioxide (CO₂). CO₂ is largely the product of burning fossil fuel and therefore the traveling towards the conference venue is expected to be a main contributor to the carbon footprint of the annual ISMRM meeting. This work estimates the C0₂ emissions of the past ISMRM meetings and tries to give data driven recommendation for future selection of ISMRM conference locations.

Tom Bruijnen^1,2, Osman Akdag^1,2,3, Charlotte VM Bruel^1,2,3, Bjorn Stemkens^1,2, Tim Schakel¹, Jan JW Lagendijk¹, Cornelis AT van den Berg^1,2, and Rob HN Tijssen^1
1Department of Radiotherapy, University Medical Center Utrecht, Utrecht, Netherlands, ²Computational Imaging Group for MRI diagnostics and therapy, Centre for Image Sciences, University Medical Center Utrecht, Utrecht, Netherlands, ³Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, Netherlands

T₂-weighted turbo spin-echo (TSE) sequences are used for abdominal tumour contouring in MR-guided radiotherapy, but these sequences are generally not compatible with most respiratory-correlated 4D imaging methods. To overcome this limitation we propose a free-breathing T₂-weighted TSE sequence based on a Cartesian acquisition with rewinded spiral profile ordering in combination with motion compensated image reconstruction. We showed that high quality free-breathing T₂-weighted TSE scans are feasible with short scan times (<5 min), which have similar contrast to the conventional linear sampled scans while simultaneously quantifying the respiratory motion.

Elizabeth Jones^1
1Radiology, NIH Clinical Center, Bethesda, MD, United States

A total cost of ownership (TCO) model was developed for MRI scanners over the ownership life from fund allocation through decommissioning in an organization with outpatient, inpatient and research scanners. The TCO model included acquisition and installation costs; site modifications to comply with safety requirements; human resources including ancillary personnel; small equipment, supplies, contrast; service contracts; IT; overhead; and upgrades. The largest expense was human resources accounting for 35% of TCO.  A cost reduction strategy is centralized remote scanning, reducing the total number of highly skilled technologists. TCO is tool for identifying hidden costs and comparing scenarios for managing costs.

Parth Kumar¹, Caroline D. Jordan¹, Joseph E. Blecha¹, Thomas R. Hayes¹, Carol Stillson¹, Aaron D. Losey¹, Eric Mastria¹, Colin Yee¹, Bridget F. Kilbride¹, Teri Moore¹, Mark W. Wilson¹, Henry F. VanBrocklin¹, and Steven W. Hetts^1
1Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, CA, United States

Recent studies have shown effective use of intravascular filtration devices to remove chemotherapy drugs; however, accurate quantification of the drug’s distribution on the device, within the targeted organ, and systemically, is necessary. We synthesized 18F analog of doxorubicin, fluorobenzylamide doxorubicin ([¹⁸F]FB-Dox), which was administered via an intra-arterial catheter, without a filter, and imaged under PET/MRI in vivo. [¹⁸F]FB-Dox showed a measurable decrease in the liver, and an increase in the bladder, kidney, and gall bladder over a 90-minute period after injection. This demonstrates a viable way to assess and track the baseline biodistribution of an intra-arterial chemotherapy procedure. 

Pim Pullens^1,2, Pieter Devolder¹, Tony Thienpont¹, and Eric Achten^1,2
1Radiology, University Hospital Gent, Gent, Belgium, ²Ghent Institute for functional and Metabolic Imaging, Ghent University, Gent, Belgium

Monitoring protocol and sequence changes is of key importance for efficiently running a clinical imaging department. Since an MRI protocol contains hundreds of parameters, it is almost impossible to manage protocols from the scanner console, especially in a clinical situation where console time for the MR physicist is very limited.  We present a python-based platform that performs all these duties and show 4 potential use cases: 1) compare parameters from sequences that share the same name 2) same purpose, different name 3) differences in naming of Regions/Exams/Programs 4) real-life example of decluttering a pediatric neuro protocol.

Egor Kretov¹, Andre Kuehne², Eva Oberacker¹, Thomas Wilhelm Eigentler¹, and Thoralf Niendorf^1,2
1B.U.F.F., Berlin Ultrahigh Field Facility, Max-Delbrück Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany, ²MRI.TOOLS GmbH, Berlin, Germany

This work presents electrodynamic considerations and an RF applicator concept that permit MR imaging and RF energy focusing inside of the human brain using sub-nanosecond broadband electromagnetic pulses. Such pulses can deposit RF energy in a small, focal area for thermal intervention. To meet this goal proof-of-principle is provided through EMF simulations using a dual-mode RF applicator that combines antipodal Vivaldi antennae with loop elements.

Antonella Castellano¹, Alice Segato², Valentina Pieri¹, Marco Vidotto², Nicolò Pecco¹, Marco Riva^3,4, Riccardo Secoli⁵, Davide Danilo Zani⁶, Stefano Brizzola⁶, Marco Trovatelli⁷, Giuliano Ravasio⁶, Marcello Cadioli⁸, Lorenzo Bello^4,9, Ferdinando Rodriguez Y Baena⁵, Elena De Momi², and Andrea Falini^1
1Neuroradiology Unit and CERMAC, Vita-Salute San Raffaele University, IRCCS San Raffaele Scientific Institute, Milan, Italy, ²Department of Electronics, Information and Bioengineering, Politecnico di Milano, Milan, Italy, ³Department of Medical Biotechnology and Translational Medicine, Università degli Studi di Milano, Milan, Italy, ⁴Neurosurgical Oncology Unit, IRCCS Humanitas Clinical and Research Center, Rozzano (MI), Italy, ⁵Department of Mechanical Engineering, Imperial College London, London, United Kingdom, ⁶Department of Veterinary Medicine, Università degli Studi di Milano, Milan, Italy, ⁷Department of Health, Animal Science and Food Safety, Faculty of Veterinary Medicine, Università degli Studi di Milano, Milan, Italy, ⁸Philips Healthcare, Milan, Italy, ⁹Department of Oncology and Hemato-Oncology, Università degli Studi di Milano, Milan, Italy

Brain tissue microstructure may influence the efficient delivery of therapeutics within the brain. Diffusion Tensor Imaging (DTI) enables the depiction of tissue properties in vivo, and thus is potentially relevant for planning convection-enhanced delivery (CED) within the brain. We report on the quantitative assessment of the distribution of a Gadolinium solution infused by CED within the brain of a live ovine model. Infusate distributions were measured at multiple timepoints and compared to microstructural properties as depicted by DTI, thus demonstrating the impact of tissue features and catheter positioning on drug distribution in vivo.

Venkateswara Gogineni¹, Dilip Maddirela¹, Woo Ram Park², Jaidip Jagtap¹, Abdul Parchur¹, Gayatri Sharma¹, El-Sayed H Ibrahim¹, Amit Joshi¹, Andrew Larson², Dong-Hyun Kim², and Sarah B White^1
1Medical College of Wisconsin, Milwaukee, WI, United States, ²Northwestern University, Chicago, IL, United States

Systemic chemotherapy is the standard of care for the treatment of unresectable metastatic colorectal cancer. However, new drug delivery platforms are needed to mitigate its associated toxicities. In this study, we develop and evaluate a liposome formulation that deliver oxaliplatin under magnetic field stimulus site selectively release in high concentration to alleviate the off-target effects in a rat model of colorectal liver metastases (CRLM). Quantitative MRI enabled assessment of changes in tumor characteristics over time for confirmation of procedural success and proper catheter-selective tumor targeting, which allows for high concentrations of oxaliplatin and improves survival outcomes in CRLM tumor-bearing rats.

Weiguo Li^1,2, Kathleen Harris¹, Ali Khan¹, Simone Raiter¹, Monica Matsumoto³, Andrew C Larson¹, and Samdeep Mouli^1
1Radiology, Northwestern University, Chicago, IL, United States, ²Research Resource Centers, University of Illinois at Chicago, Chicago, IL, United States, ³Radiology, University of Chicago, Chicago, IL, United States

Management options for localized prostate cancer have largely remained the same for the past 30 years. ⁹⁰Yttrium (⁹⁰Y) radioembolization is a novel radiotherapy approach that offers the potential to deliver high-dose radiation therapy with minimal non-target radiation. However, currently no accurate way exists to evaluate radiation effects noninvasively following embolization. In this study, we sought to apply diffusion and dynamic contrast-enhanced perfusion MRI to investigate assess the effects of treatment following ⁹⁰Y prostate artery radioembolization in a dog prostate model.

Finya Ketelsen^1,2, Jakob Kreutner³, Gregor Schaefers^1,3, and Kevin Kröninger^2
1MR:comp GmbH, Testing Services for MR Safety & Compatibility, Gelsenkirchen, Germany, ²TU Dortmund University, Dortmund, Germany, ³MRI-STaR - Magnetic Resonance Institute for Safety, Technology and Research GmbH, Gelsenkirchen, Germany

To determine the RF-induced heating of an active implant, it is necessary to measure the 3D distribution of the power deposition in the hotspot volume. By measuring the E_rms distribution around a test object, different influences on the decay were investigated. It was shows that radial decay can be described with a single model along test object. This model is normalized to a defined distance. The measurement values along the TO at this distance, can be used to scale the model and the power deposition inside the hotspot volume can be calculated. This leads to an advantage in time saving.

Beni Mulyana^1,2, Qingfei Luo¹, Aki Tsuchiyagaito¹, Ashkan Rashedi¹, Jared Smith¹, Masaya Misaki¹, Duke Shereen³, Samuel Cheng², Martin Paulus¹, Hamed Ekhtiari¹, and Jerzy Bodurka^1,4
1Laureate Institute for Brain Research, Tulsa, OK, United States, ²University of Oklahoma, Tulsa, OK, United States, ³The Graduate Center, City University of New York, New York, NY, United States, ⁴Stephenson School of Biomedical Engineering, University of Oklahoma, Norman, OK, United States

We evaluated subject safety and the fMRI image quality in the presence of transcranial alternating current stimulation (tACS). Scalp temperatures under the tACS electrodes with and without stimulations were measured. Result indicated: i) the tACS stimulation itself had no harmful impact on scalp temperature; ii) tACS’s artifacts had negligible effects on fMRI images. Although the fMRI scan produced heating effects due to the RF energy deposition in tACS electrodes, the scalp temperatures remained below 37°C during a 12-min scan regardless of the presence of stimulations. Thus, concurrent tACS with fMRI has no impact on patient safety and image quality.

Maxim Terekhov¹, Ibrahim A. Elabyad¹, Carsten Kögler², Theresa Reiter^1,3, and Laura M. Schreiber^1
1Chair of Cellular and Molecular Imaging, Comprehensive Heart Failure Center (CHFC), University Hospital Würzburg, Wuerzburg, Germany, ²Rapid Biomedical, Rimpar, Germany, ³Department of Internal Medicine l, University Hospital Wuerzburg, Wuerzburg, Germany

The purpose of this study was to simulate the variation of SAR caused by shifting the position of a cardiac array prototype when different B1-shimming phase vectors are employed. The variation of 10g average SAR distribution due to displacing the anterior array position on the thorax (central, shifted 5 cm to the right, left, head, foot and diagonal directions) was computed and analyzed using two human voxel models. The final goal is to determine maximal driving voltage of the array with adequate safety margins considering new hot-spots originated from possible array misplacement

Astrid Wollrab¹, Oliver Kraff², Oliver Speck^1,3,4, Harald H. Quick^2,5, and Mark E. Ladd^2,6
1Biomedical Magnetic Resonance, Otto-von-Guericke University, Magdeburg, Germany, ²Erwin L. Hahn Institute for Magnetic Resonance Imaging, University Duisburg-Essen, Essen, Germany, ³German Center of Neurodegenerative Diseases - DZNE, Magdeburg, Germany, ⁴Leibniz Institute for Neurobiology, Magdeburg, Germany, ⁵High-Field and Hybrid MR Imaging, University Hospital Essen, Essen, Germany, ⁶Medical Physics in Radiology, German Cancer Research Center - DKFZ, Heidelberg, Germany

One of the main tasks of the German Ultrahigh Field Imaging (GUFI) network was the establishment of a uniform online MRI safety training, created in cooperation with all German ultrahigh field (UHF) sites. Implemented with Moodle, the course provides basic MRI safety training and includes three lessons: "MRI Environment", "Subject Measurements" and "In Case of Emergencies". Participants have to pass tests, consisting of appropriate questions, at the end of each lesson. In total, 255 participants have successfully completed the course (since April 2018).

Tom Dijkhuis^1,2, Pim Hendriks², Mark Burgmans², Andrew Webb², and Irena Zivkovic^2
1Technical University of Delft, Delft, Netherlands, ²Radiology Department, Leiden University Medical Center, Leiden, Netherlands

Magnetic resonance (MR) guidance of microwave ablation of hepatic tumors could help to overcome poor visualisation of the ablation zone by ultrasound, may allow better intraprocedural confirmation of technical success. The ablation applicator is a metallic rod and can potentially act as an ‘antenna’ during MR imaging which can produce unwanted localized heating in nearby tissue. In this abstract, we investigated via electromagnetic simulations the maximum SAR_10g changes caused by applicators of different radius and length and for various insertion angles.

 

Xin Chen¹, Shinji Mitsui², Yoshinori Hamamura¹, and Michael Steckner^1
1Canon Medical Research USA, Inc., Mayfield Village, OH, United States, ²Canon Medical Systems Corporation, Otawara-shi, Japan

Pulse energy SAR measurement method (NEMA standard MS-8) uses current sensing flux loops to measure coil power loss, which varies in different imaging conditions. Modeling results suggest that using multiple flux loops distributed around Tx coil, as presently defined by the standard, may not give accurate results. For whole body birdcage coil loaded with a human subject, single flux loop spaced from endring and positioned at 3 or 9 o’clock may give more accurate results.