Bridget F Kilbride¹, Caroline D Jordan², Andrew Chu³, Dave Barry³, Kerstin Mueller⁴, Sinyeob Ahn⁴, Teri Moore⁵, Mark W Wilson⁵, and Steven W Hetts^5
1Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, CA, United States, ²Texas A&M University, Houston, TX, United States, ³Penumbra, Inc., Alameda, CA, United States, ⁴Siemens Medical Solutions, Malvern, PA, United States, ⁵University of California San Francisco, San Francisco, CA, United States

Interventional MRI catheter-based procedures are greatly limited by current devices and their safety profiles, and next-generation MR-safe devices are still in development. We designed and evaluated a polymeric catheter concept that is both safe and visible in MRI and X-ray environments. All imaging was done in a two-room hybrid angio-MR suite to demonstrate compatibility with next-generation image-guided procedures.  In a phantom, we acquired GRE and TSE sequences at 3T and imaged on a clinical biplane angiographic system to quantitate MRI visibility and radiopacity, respectively. The catheters exhibited promising tracking characteristics under MRI and X-ray on a polymer-based catheter.

Han Nijsink¹, Kristian G. Overduin¹, Sytse F. De Jong¹, Paul J.A. Borm², Torben Pätz³, Dennis G.H. Bosboom⁴, Michiel C. Warlé¹, and Jurgen J. Fütterer^1
1Radboudumc, Nijmegen, Netherlands, ²Nano4Imaging, Düsseldorf, Germany, ³Fraunhover MEVIS, Bremen, Germany, ⁴Soteria Medical B.V., Arnhem, Netherlands

MRI-guidance for endovascular interventions is only eligible with clearly visible endovascular devices. Hence, we quantitatively and qualitatively evaluated marker visibility and artifact size of passive marker guidewires for different MRI sequence types, MRI parameters and marker concentrations at 3T MRI using a pulsatile flow phantom. Artifact size was positively correlated with TE and marker concentration and was significantly larger for bSSFP images compared to GRE images. The GRE images outperformed the bSSFP images in the quantitative image quality assessment. In conclusion, markers were adequately visible in GRE images and artifact visibility can be optimized by adjusting TE and marker concentration.

Andreas Reichert¹ and Michael Bock^1
1Department of Radiology, Medical Physics, Medical Center – University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany

The phase-only cross correlation (POCC) algorithm can be used to accurately detect the orientation of a passive needle guide in needle interventions. A POCC sequence continuously visualizes the planned needle pathway during needle guide movement. The insertion of a needle into the needle guide, however, degrades the POCC detection because of susceptibility artifacts. In this work, susceptibility artifacts of a needle are measured and simulated, and a potential integration integrated into the POCC algorithm is evaluated.

Junichi Tokuda^1,2, Pedro Moreira^1,2, Amanda Aleong³, Franklin King¹, John P Grimble⁴, Kemal Tuncali^1,2, Ravi Seethamraju⁵, Gerald Moran⁶, Himanshu Bhat⁵, Nick V Iftimia⁴, and Jesung Park^4
1Radiology, Brigham and Women's Hospital, Boston, MA, United States, ²Harvard Medical School, Boston, MA, United States, ³University of Toronto, Toronto, ON, Canada, ⁴Physical Science Inc., Andover, MA, United States, ⁵Siemens Medical Solutions USA Inc., Boston, MA, United States, ⁶Siemens Healthcare Ltd., Oakville, ON, Canada

Accurate needle placement is crucial for MRI-guided targeted prostate biopsy. However, needle placement accuracy is often affected by the deviation of the needle caused by the anatomical structures on the needle path. To avoid anatomical structures that are likely to cause significant needle deviation, we developed a 4-degree-of-freedom (DoF) needle-guide manipulator system named “Smart Template”. The Smart Template allows physicians to insert a needle accurately to the target while monitoring the needle through interactive real-time MRI. We performed a preliminary evaluation of the device to test the feasibility of needle placement using Smart Template.

Ehud Jeruham Schmidt¹, Marc Morcos², Anthony Gunderman³, Junichi Tokuda⁴, Ravi Teja Seethamraju⁵, Luca Neri¹, Carmen Kut², Henry R. Halperin¹, Akila Ninette Viswanathan², and Yue Chen^3
1Medicine (Cardiology), Johns Hopkins School of Medicine, Baltimore, MD, United States, ²Radiation Oncology, Johns Hopkins School of Medicine, Baltimore, MD, United States, ³Mechanical Engineering, University of Arkansas, Fayetteville, AR, United States, ⁴Radiology, Brigham and Women's Hospital, Boston, MA, United States, ⁵Siemens Medical Solutions, Boston, MA, United States

  A metallic actively-tracked injection needle was constructed for purposes of reducing dose to normal tissues surrounding irradiated tumors in cervical cancer and prostate cancer radiation therapy. Hydrogel is injected into tissue or anatomic cavities between the tumor and normal tissues, increasing the distance from the radiation source. The needle was tested in a gynecological phantom and in swine. It provided 1.2x1.2x1.2mm³ targeting precision @16 frames-per-second navigation, supporting rapid navigation speeds currently possible only under X-ray or Ultrasound guidance. The injected topology over time was visualized during injection, allowing creation of more uniform dose-shielding regions.      

Isabelle Saniour¹, Fraser Robb², Victor Taracila², 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, ²MR Engineering, GE Healthcare, Aurora, OH, United States, ³Department of Neurological Surgery, Weill Cornell Medicine, New york, NY, United States

Transcranial magnetic resonance guided focused ultrasound (MRgFUS) has shown dramatic success in the treatment of various neurodegenerative diseases. However, black band artifacts arise in MR images due to the high-permittivity water bath and the metallically lined helmet-shaped transducer together with the vendor-installed body coil. In this work, we present electromagnetic simulations of a very thin, flexible, and acoustic transparent head coil design (FUS-Flex). Simulations show a signal-to-noise-ratio (SNR) increase of 3.5× and 5× compared to a body coil with and without the transducer, respectively, and an attenuation of the black band artifact in the regions of interest.

Jaime Mata¹, Lauren Powlovich², David Moore², and Linda Martin^1
1University of Virginia, Charlottesville, VA, United States, ²Focused Ultrasound Foundation, Charlottesville, VA, United States

  Malignant lung cancer carries a poor prognosis with a 5-year survival rate of about 18%. This new method proposes an innovative minimally invasive procedure for the transcutaneous ablation of lung tumor masses with complete removal or significant debulking of the masses. This new procedure could increase lung cancer survival rates and at the same time decrease morbidity and side effects associated with current treatment therapies. It will also provide a viable treatment for a large group of patients that cannot tolerate resection surgery, radiotherapy and chemotherapy, or who have had prior radiation and cannot have additional radiation to that region.

Kristin Quah¹, Jonathan Samuel Goodman², Gustavo Loo Kang Chau³, Kim Butts Pauly⁴, Pejman Ghanouni⁴, Gary Glover⁴, and Jennifer McNab^4
1Electrical Engineering, Stanford University, Stanford, CA, United States, ²Biophysics, Stanford University, Stanford, CA, United States, ³Bioengineering, Stanford University, Stanford, CA, United States, ⁴Radiology, Stanford University, Stanford, CA, United States

Probabilistic diffusion tractography and fMRI are two alternative methods for targeting the ventral intermediate nucleus of the thalamus in patients with essential tremor (ET) for treatment with transcranial magnetic resonance imaging-guided focused ultrasound (tcMRgFUS). In this study, three ET subjects underwent MRgFUS thalamotomy with traditional targeting using anatomic landmarks. Tractography and fMRI targeting were compared retrospectively to determine how they relate to one another and to the targets selected by the surgeon. Two of the three subjects showed a consistent spatial relationship between fMRI, tractography and anatomical targets.

Kilian A. Dietrich^1,2, Sebastian Klüter², Benjamin R. Knowles¹, Jürgen Debus^2,3, Markus E. Ladd^1,3, and Tanja Platt^1
1Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany, ²Radiation Oncology, University Hospital, Heidelberg, Germany, ³Faculty of Medicine, Heidelberg University, Heidelberg, Germany

Electromagnetic field simulations were performed at 0.345T and 1.5T to find an advantageous RF coil design for typical scanners in MR-guided therapy. Hence, different birdcage coil designs were characterized and compared with one another with respect to their corresponding transmit and receive field characteristics.

Osman Akdag¹, Stefano Mandija¹, Pim Borman¹, Eveline Alberts², and Martin Fast^1
1Radiotherapy, University Medical Center Utrecht, Utrecht, Netherlands, ²Philips Healthcare, Best, Netherlands

Stereotactic arrhythmia radioablation (STAR) is a novel non-invasive treatment technique for ventricular tachycardia patients, refractory to conventional catheter ablation. Here, we investigate the feasibility of integrating real-time, free-breathing, cardiac cine-MRI into the STAR radiotherapy workflow. As a first step towards MRI-guided STAR treatments, we test our imaging approach on a diagnostic 1.5T MRI-simulator (Philips, Ingenia), and on a 1.5T Elekta Unity MR-linac. Our results indicate the feasibility of acquiring real-time, free-breathing, cine MRI images on both systems at 14Hz, enabling real-time motion assessment and delivery adaptation without additional cardiac imaging hardware. 

Jonathan Goodwin^1,2, Satomi Higuchi¹, Laura O'Connor^1,2, Amy Zafara¹, Kate Skehan¹, Terry Perkins³, Sanjiv Gupta¹, Peter Greer^1,2, Jane Ludbrook^1,2, and John Simpson^1,2
1Calvary Mater Hospital, Newcastle, Australia, ²Univeristy of Newcastle, Newcastle, Australia, ³Blacktown Cancer & Haematology Centre, Blacktown, Australia

4D-CT is routinely acquired for lung cancer treatment planning to visualise the extent of tumour motion, to determine the appropriate treatment target volume. However, it can be unreliable in cases of irregular breathing, is susceptible to image artefact in regions close to the diaphragm, and shows generally poor soft tissue contrast. In this study we evaluated an alternative self-navigating 4D-MRI approach in terms of motion detection accuracy, measured tumour volume, and dosimetric differences observed with respect to patients’ existing lung cancer treatment plans.

Nathanael Kim¹, Kathryn Tringale², Christopher Crane², Neelam Tyagi¹, and Ricardo Otazo^1,3
1Medical Physics, Memorial Sloan Kettering Cancer Center, New York, NY, United States, ²Radiation Oncology, Memorial Sloan Kettering Cancer Center, New York, NY, United States, ³Radiology, Memorial Sloan Kettering Cancer Center, New York, NY, United States

MRSIGMA is a promising real-time volumetric imaging for MRI-guided adaptive radiotherapy using a MR-Linac system. However, the lack of a real-time 3D reference image acquired with similar temporal resolution introduces significant challenges for in vivo validation. This work proposes a retrospective self-validation for MRSIGMA, where the same data used for real-time imaging are used to create a non-real-time reference. MRSIGMA with self-validation is tested in patients with liver tumors using quantitative metrics defined on the tumor and nearby organs-at-risk structures.

Tian Li¹, Haonan Xiao¹, Ge Ren¹, Weiwei Liu², Yibao Zhang², Hao Wu², Weihu Wang², and Jing Cai^1
1Department of Health Technology and Informatics, The Hong Kong Polytechnic University, Hong Kong, Hong Kong, ²Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education/Beijing), Department of Radiation Oncology, Beijing Cancer Hospital & Institute, Peking University Cancer Hospital & Institute, Beijing, China, Beijing, China

Motion management plays an important role in abdominal cancer radiotherapy. Current motion measurement method using 2D Cine MRI is inefficient. However, there is no commercial four-dimensional MRI available for motion management. In this study, we aim to investigate a fast-volumetric four-dimensional MRI technique using commercial sequence for tumor motion management in liver cancer patient. Our preliminary results shown that the commercially available TWIST-VIBE 4D-MRI sequence is capable of measuring liver tumor motion accurately with an acceptable tumor contrast.

Oi Lei Wong¹, Jing Yuan¹, Darren MC Poon², Yi Hang Zhou¹, Siu Ki Yu¹, and Kin Yin Cheung^1
1Medical Physics and Research, Hong Kong Sanatorium, Hong Kong, Hong Kong, ²Comprehensive Oncology Center, Hong Kong Sanatorium, Hong Kong, Hong Kong

A novel ITV determination technique based on the volume of positional probability distribution (PPV) generated by volumetric 4DMRI was proposed and verified on cancer patients. For large targets, both PPV and 4D-CT generated ITV were similar with relatively large DSC. For small targets, however, relatively small DSC was observed, where poor tumor visibility in 4D-CT may be the cause.

Emilia Palmér¹, Fredrik Nordström^1,2, Anna Karlsson^1,2, Karin Petruson³, Maria Ljungberg^1,2, and Maja Sohlin^1,2
1Department of Radiation Physics, Institute of Clinical Sciences, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden, ²Department of Medical Physics and Biomedical Engineering, Sahlgrenska University Hospital, Gothenburg, Sweden, ³Department of Oncology and Radiotherapy, Institute of Clinical Sciences, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden

In an MRI-only radiotherapy workflow, in addition to enabling absorbed dose calculation the generated synthetic CT (sCT) must also be valid for patient positioning at treatment course. To evaluate MRI-only patient positioning for head and neck cancer patients, fourteen 3D cone beam CTs were retrospectively registered to CT and sCT. Further, original Digital Reconstructed radiographs originating from the CT and synthetic Digital Reconstructed radiographs originating from the sCT, were retrospectively registered to orthogonal projections. The small mean difference between the registrations showed that sCT could replace the CT for both 3D and 2D head and neck radiotherapy patient positioning.

Erik R Huijing¹, Femke Wetzels¹, Edwin Versteeg¹, Koenraad Rhebergen¹, Simon Woodings¹, Dennis Klomp¹, Marielle Philippens¹, Nico van den Berg², and Stefano Mandija^3
1UMC Utrecht, Utrecht, Netherlands, ²Computational Imaging Group for MR Diagnostic & Therapy, UMC Utrecht, Utrecht, Netherlands, ³Computational Imaging Group for MR Diagnostic & Therapy, University Medical Center Utrecht, Utrecht, Netherlands

We present two hoods for acoustic noise damping for MRI in Radiotherapy. This is especially relevant for brain and head-and-neck patients who are scanned repetitively inside immobilization masks, which prevent wearing all the required earing protection devices. The hoods show good noise damping (average at least 10 dB attenuation) and minimal radiation dose attenuation (<1%), making them suitable also for MR-linac systems. Subjective results from a survey on 15 volunteers show that the hoods are well tolerated and do not increase significantly the feeling of claustrophobia. 

Xin Miao¹, Raanan Marants², Thomas Benkert³, Evangelia Kaza², Jeremy Bredfeldt², and Atchar Sudhyadhom^2
1Siemens Medical Solutions USA Inc., Boston, MA, United States, ²Department of Radiation Oncology, Dana-Farber/Brigham and Women's Cancer Center, Boston, MA, United States, ³Siemens Healthcare GmbH, Erlangen, Germany

CT-based proton therapy dose calculation suffers from significant uncertainties that critically limit clinical efficacy. Previous works demonstrated improved proton range calculation by combining quantitative MRI with CT. This study extends those works into bone, a challenging region for tissue characterization. CT and a novel UTE MRI technique were used to investigate their complimentary information for bone characterization. Both phantom and in vivo experiments showed that combining UTE-MRI and CT measurements achieved accurate classification of bone types.  Understanding of bone types can have significant implications on the determination of bone tissue composition and, ultimately, accuracy of radiation delivery in proton therapy.

Ali Agely¹, Vipul Sheth¹, Pejman Ghanouni¹, and Ryan L. Brunsing^1
1Radiology, Stanford University, Palo Alto, CA, United States

Desmoid tumors are challenging to control with chemotherapy, surgery, or radiation. This retrospective review evaluated patients with extra-abdominal desmoid tumors treated with MR-guided cryoablation at our institution over two years. The primary endpoint was tumor volume change before and 3 months after cryoablation; the secondary endpoint was the change in health status assessed at the same interval. Our study demonstrates MR-guided cryoablation results in the reduction of both tumor size and improvement in health status scores. No severe adverse events occurred. We conclude that MR-guided cryoablation is an effective and safe treatment option for desmoid tumors.

Weiguo Li^1,2, Kathleen Harris¹, Amrutha Mylarapu¹, Malcolm Burks¹, Simone Raiter¹, Vanessa Louise Gates¹, Andrew Gordon¹, Robert Lewandowski¹, Riad Salem¹, and Samdeep Mouli^1
1Radiology, Northwestern University, Chicago, IL, United States, ²Bioengineering, University of Illinois at Chicago, Chicago, IL, United States

Local-regional therapy of prostate cancer with ⁹⁰Yttrium (⁹⁰Y) radioembolization is a novel radiotherapy approach that delivers 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 PET/MRI to assess biodistribution of ⁹⁰Y and estimate effects of treatment following ⁹⁰Y prostate artery radioembolization in a dog prostate model.

L. Klaassen^1,2, M.G. Jaarsma-Coes^1,2, T.A. Ferreira², T.H.K. Vu¹, M. Marinkovic¹, C.R.N. Rasch³, G.P.M. Luyten¹, and J.W.M. Beenakker^1,2
1Department of Ophthalmology, LUMC, Leiden, Netherlands, ²Department of Radiology, LUMC, Leiden, Netherlands, ³Department of Radiotherapy, LUMC, Leiden, Netherlands

Ocular magnetic resonance imaging, enabling 3D tumour imaging and providing better soft tissue contrast than conventional ultrasound, is increasingly used for uveal melanoma. The aim of this research was to determine the difference in geometrical tumour measurements between ultrasound and MRI. For this purpose, tumour prominence and largest basal diameter were calculated automatically based on MR imaging and compared to the US measurements. Differences >0.5mm were observed in 55% of prominence measurements and 80% of LBD measurements. Furthermore, automatically measuring tumour geometry based on 3D MR imaging lead to the discovery of inconsistencies in measurement definitions within and across disciplines.