Publications

2017
O'Donnell LJ, Suter Y, Rigolo L, Kahali P, Zhang F, Norton I, Albi A, Olubiyi O, Meola A, Essayed WI, et al. Automated White Matter Fiber Tract Identification in Patients with Brain Tumors. Neuroimage Clin. 2017;13 :138-53.Abstract

We propose a method for the automated identification of key white matter fiber tracts for neurosurgical planning, and we apply the method in a retrospective study of 18 consecutive neurosurgical patients with brain tumors. Our method is designed to be relatively robust to challenges in neurosurgical tractography, which include peritumoral edema, displacement, and mass effect caused by mass lesions. The proposed method has two parts. First, we learn a data-driven white matter parcellation or fiber cluster atlas using groupwise registration and spectral clustering of multi-fiber tractography from healthy controls. Key fiber tract clusters are identified in the atlas. Next, patient-specific fiber tracts are automatically identified using tractography-based registration to the atlas and spectral embedding of patient tractography. Results indicate good generalization of the data-driven atlas to patients: 80% of the 800 fiber clusters were identified in all 18 patients, and 94% of the 800 fiber clusters were found in 16 or more of the 18 patients. Automated subject-specific tract identification was evaluated by quantitative comparison to subject-specific motor and language functional MRI, focusing on the arcuate fasciculus (language) and corticospinal tracts (motor), which were identified in all patients. Results indicate good colocalization: 89 of 95, or 94%, of patient-specific language and motor activations were intersected by the corresponding identified tract. All patient-specific activations were within 3mm of the corresponding language or motor tract. Overall, our results indicate the potential of an automated method for identifying fiber tracts of interest for neurosurgical planning, even in patients with mass lesions.

Guenette JP, Tuncali K, Himes N, Shyn PB, Lee TC. Percutaneous Image-Guided Cryoablation of Head and Neck Tumors for Local Control, Preservation of Functional Status, and Pain Relief. AJR Am J Roentgenol. 2017;208 (2) :453-8.Abstract

OBJECTIVE: We report nine consecutive percutaneous image-guided cryoablation procedures of head and neck tumors in seven patients (four men and three women; mean age, 68 years; age range, 50-78 years). Ablation of the entire tumor for local control or ablation of a region of tumor for pain relief or preservation of function was achieved in eight of nine procedures. One patient experienced intraprocedural bradycardia, and another developed a neopharyngeal abscess. There were no deaths, permanent neurologic or functional deficits, vascular complications, or adverse cosmetic sequelae due to the procedures. CONCLUSION: Percutaneous image-guided cryoablation offers a potentially less morbid minimally invasive treatment option than salvage head and neck surgery. The complications that we encountered may be avoidable with increased experience. Further work is needed to continue improving the safety and efficacy of cryoablation of head and neck tumors and to continue expanding the use of cryoablation in patients with head and neck tumors that cannot be treated surgically.

Glazer DI, Hassanzadeh E, Fedorov A, Olubiyi OI, Goldberger SS, Penzkofer T, Flood TA, Masry P, Mulkern RV, Hirsch MS, et al. Diffusion-weighted Endorectal MR Imaging at 3T for Prostate Cancer: Correlation with Tumor Cell Density and Percentage Gleason Pattern on Whole Mount Pathology. Abdom Radiol (NY). 2017;42 (3) :918-25.Abstract

OBJECTIVE: To determine if tumor cell density and percentage of Gleason pattern within an outlined volumetric tumor region of interest (TROI) on whole-mount pathology (WMP) correlate with apparent diffusion coefficient (ADC) values on corresponding TROIs outlined on pre-operative MRI. METHODS: Men with biopsy-proven prostate adenocarcinoma undergoing multiparametric MRI (mpMRI) prior to prostatectomy were consented to this prospective study. WMP and mpMRI images were viewed using 3D Slicer and each TROI from WMP was contoured on the high b-value ADC maps (b0, 1400). For each TROI outlined on WMP, TCD (tumor cell density) and the percentage of Gleason pattern 3, 4, and 5 were recorded. The ADCmean, ADC10th percentile, ADC90th percentile, and ADCratio were also calculated in each case from the ADC maps using 3D Slicer. RESULTS: Nineteen patients with 21 tumors were included in this study. ADCmean values for TROIs were 944.8 ± 327.4 vs. 1329.9 ± 201.6 mm(2)/s for adjacent non-neoplastic prostate tissue (p < 0.001). ADCmean, ADC10th percentile, and ADCratio values for higher grade tumors were lower than those of lower grade tumors (mean 809.71 and 1176.34 mm(2)/s, p = 0.014; 10th percentile 613.83 and 1018.14 mm(2)/s, p = 0.009; ratio 0.60 and 0.94, p = 0.005). TCD and ADCmean (ρ = -0.61, p = 0.005) and TCD and ADC10th percentile (ρ = -0.56, p = 0.01) were negatively correlated. No correlation was observed between percentage of Gleason pattern and ADC values. CONCLUSION: DWI MRI can characterize focal prostate cancer using ADCratio, ADC10th percentile, and ADCmean, which correlate with pathological tumor cell density.

Mitsouras D, Lee TC, Liacouras P, Ionita CN, Pietilla T, Maier SE, Mulkern RV. Three-dimensional Printing of MRI-visible Phantoms and MR Image-guided Therapy Simulation. Magn Reson Med. 2017;77 (2) :613-22.Abstract

PURPOSE: To demonstrate the use of anatomic MRI-visible three-dimensional (3D)-printed phantoms and to assess process accuracy and material MR signal properties. METHODS: A cervical spine model was generated from computed tomography (CT) data and 3D-printed using an MR signal-generating material. Printed phantom accuracy and signal characteristics were assessed using 120 kVp CT and 3 Tesla (T) MR imaging. The MR relaxation rates and diffusion coefficient of the fabricated phantom were measured and (1) H spectra were acquired to provide insight into the nature of the proton signal. Finally, T2 -weighted imaging was performed during cryoablation of the model. RESULTS: The printed model produced a CT signal of 102 ± 8 Hounsfield unit, and an MR signal roughly 1/3(rd) that of saline in short echo time/short repetition time GRE MRI (456 ± 36 versus 1526 ± 121 arbitrary signal units). Compared with the model designed from the in vivo CT scan, the printed model differed by 0.13 ± 0.11 mm in CT, and 0.62 ± 0.28 mm in MR. The printed material had T2 ∼32 ms, T2*∼7 ms, T1 ∼193 ms, and a very small diffusion coefficient less than olive oil. MRI monitoring of the cryoablation demonstrated iceball formation similar to an in vivo procedure. CONCLUSION: Current 3D printing technology can be used to print anatomically accurate phantoms that can be imaged by both CT and MRI. Such models can be used to simulate MRI-guided interventions such as cryosurgeries. Future development of the proposed technique can potentially lead to printed models that depict different tissues and anatomical structures with different MR signal characteristics. 

Hassanzadeh E, Glazer DI, Dunne RM, Fennessy FM, Harisinghani MG, Tempany CM. Prostate Imaging Reporting and Data System Version 2 (PI-RADS v2): A Pictorial Review. Abdom Radiol (NY). 2017;42 (1) :278-89.Abstract

The most recent edition of the prostate imaging reporting and data system (PI-RADS version 2) was developed based on expert consensus of the international working group on prostate cancer. It provides the minimum acceptable technical standards for MR image acquisition and suggests a structured method for multiparametric prostate MRI (mpMRI) reporting. T1-weighted, T2-weighted (T2W), diffusion-weighted (DWI), and dynamic contrast-enhanced (DCE) imaging are the suggested sequences to include in mpMRI. The PI-RADS version 2 scoring system enables the reader to assess and rate all focal lesions detected at mpMRI to determine the likelihood of a clinically significant cancer. According to PI-RADS v2, a lesion with a Gleason score ≥7, volume >0.5 cc, or extraprostatic extension is considered clinically significant. PI-RADS v2 uses the concept of a dominant MR sequence based on zonal location of the lesion rather than summing each component score, as was the case in version 1. The dominant sequence in the peripheral zone is DWI and the corresponding apparent diffusion coefficient (ADC) map, with a secondary role for DCE in equivocal cases (PI-RADS score 3). For lesions in the transition zone, T2W images are the dominant sequence with DWI/ADC images playing a supporting role in the case of an equivocal lesion.

Sastry R, Bi WL, Pieper S, Frisken S, Kapur T, Wells W, Golby AJ. Applications of Ultrasound in the Resection of Brain Tumors. J Neuroimaging. 2017;27 (1) :5-15.Abstract

Neurosurgery makes use of preoperative imaging to visualize pathology, inform surgical planning, and evaluate the safety of selected approaches. The utility of preoperative imaging for neuronavigation, however, is diminished by the well-characterized phenomenon of brain shift, in which the brain deforms intraoperatively as a result of craniotomy, swelling, gravity, tumor resection, cerebrospinal fluid (CSF) drainage, and many other factors. As such, there is a need for updated intraoperative information that accurately reflects intraoperative conditions. Since 1982, intraoperative ultrasound has allowed neurosurgeons to craft and update operative plans without ionizing radiation exposure or major workflow interruption. Continued evolution of ultrasound technology since its introduction has resulted in superior imaging quality, smaller probes, and more seamless integration with neuronavigation systems. Furthermore, the introduction of related imaging modalities, such as 3-dimensional ultrasound, contrast-enhanced ultrasound, high-frequency ultrasound, and ultrasound elastography, has dramatically expanded the options available to the neurosurgeon intraoperatively. In the context of these advances, we review the current state, potential, and challenges of intraoperative ultrasound for brain tumor resection. We begin by evaluating these ultrasound technologies and their relative advantages and disadvantages. We then review three specific applications of these ultrasound technologies to brain tumor resection: (1) intraoperative navigation, (2) assessment of extent of resection, and (3) brain shift monitoring and compensation. We conclude by identifying opportunities for future directions in the development of ultrasound technologies.

Ciris PA, Cheng C-C, Mei C-S, Panych LP, Madore B. Dual-Pathway Sequences for MR Thermometry: When and Where to use Them. Magn Reson Med. 2017;77 (3) :1193-200.Abstract

PURPOSE: Dual-pathway sequences have been proposed to help improve the temperature-to-noise ratio (TNR) in MR thermometry. The present work establishes how much of an improvement these so-called "PSIF-FISP" sequences may bring in various organs and tissues. METHODS: Simulations and TNR calculations were validated against analytical equations, phantom, abdomen, and brain scans. Relative TNRs for PSIF-FISP, as compared to a dual-FISP reference standard, were calculated for flip angle (FA) = 1 to 85 º and repetition time (TR) = 6 to 60 ms, for gray matter, white matter, cervix, endometrium, myometrium, prostate, kidney medulla and cortex, bone marrow, pancreas, spleen, muscle, and liver tissues. RESULTS: PSIF-FISP was TNR superior in the kidney, pelvis, spleen, or gray matter at most tested TR and FA settings, and benefits increased at shorter TRs. PSIF-FISP was TNR superior in other tissues, e.g., liver, muscle, pancreas, for only short TR settings (20 ms or less). The TNR benefits of PSIF-FISP increased slightly with FA, and strongly with decreasing TR. Up to two- to three-fold reductions in TR with 20% TNR gains were achievable. In any given tissue, TNR performance is expected to further improve with heating, due to changes in relaxation rates. CONCLUSION: Dual-pathway PSIF-FISP can improve TNR and acquisition speed over standard gradient-recalled echo sequences, but optimal acquisition parameters are tissue dependent. Magn Reson Med 77:1193-1200, 2017. © 2016 International Society for Magnetic Resonance in Medicine.

Chao T-C, Chiou J-yuan G, Maier SE, Madore B. Fast Diffusion Imaging with High Angular Resolution. Magn Reson Med. 2017;77 (2) :696-706.Abstract

PURPOSE: High angular resolution diffusion imaging (HARDI) is a well-established method to help reveal the architecture of nerve bundles, but long scan times and geometric distortions inherent to echo planar imaging (EPI) have limited its integration into clinical protocols. METHODS: A fast imaging method is proposed here that combines accelerated multishot diffusion imaging (AMDI), multiplexed sensitivity encoding (MUSE), and crossing fiber angular resolution of intravoxel structure (CFARI) to reduce spatial distortions and reduce total scan time. A multishot EPI sequence was used to improve geometrical fidelity as compared to a single-shot EPI acquisition, and acceleration in both k-space and diffusion sampling enabled reductions in scan time. The method is regularized and self-navigated for motion correction. Seven volunteers were scanned in this study, including four with volumetric whole brain acquisitions. RESULTS: The average similarity of microstructural orientations between undersampled datasets and their fully sampled counterparts was above 85%, with scan times below 5 min for whole-brain acquisitions. Up to 2.7-fold scan time acceleration along with four-fold distortion reduction was achieved. CONCLUSION: The proposed imaging strategy can generate HARDI results with relatively good geometrical fidelity and low scan duration, which may help facilitate the transition of HARDI from a successful research tool to a practical clinical one. Magn Reson Med, 2016. © 2016 Wiley Periodicals, Inc.

2016
Mallory MA, Losk K, Camuso K, Caterson S, Nimbkar S, Golshan M. Does "Two is Better Than One" Apply to Surgeons? Comparing Single-Surgeon Versus Co-surgeon Bilateral Mastectomies. Ann Surg Oncol. 2016;23 (4) :1111-6.Abstract
BACKGROUND: Bilateral mastectomies (BM) are traditionally performed by single surgeons (SS); a co-surgeon (CS) technique, where each surgeon concurrently performs a unilateral mastectomy, offers an alternative approach. We examined differences in general surgery time (GST), overall surgery time (OST), and patient complications for BM performed by CS and SS. METHODS: Patients undergoing BM with tissue expander reconstruction (BMTR) between January 2010 and May 2014 at our center were identified through operative case logs. GST (incision to end of BM procedure), reconstruction duration (RST) (plastic surgery start to end of reconstruction) and OST (OST = GST + RST) was calculated. Patient age, presence/stage of cancer, breast weight, axillary procedure performed, and 30-day postoperative complications were extracted from medical records. Differences in GST and OST between CS and SS cases were assessed with a t test. A multivariate linear regression was fit to identify factors associated with GST. RESULTS: A total of 116 BMTR cases were performed [CS, n = 67 (57.8 %); SS, n = 49 (42.2 %)]. Demographic characteristics did not differ between groups. GST and OST were significantly shorter for CS cases, 75.8 versus 116.8 min, p < .0001, and 255.2 versus 278.3 min, p = .005, respectively. Presence of a CS significantly reduces BMTR time (β = -38.82, p < .0001). Breast weight (β = 0.0093, p = .03) and axillary dissection (β = 28.69, p = .0003) also impacted GST. CONCLUSIONS: The CS approach to BMTR reduced both GST and OST; however, the degree of time savings (35.1 and 8.3 %, respectively) was less than hypothesized. A larger study is warranted to better characterize time, cost, and outcomes of the CS-approach for BM.
Manuel MM, Cho LP, Catalano PJ, Damato AL, Miyamoto DT, Tempany CM, Schmidt EJ, Viswanathan AN. Outcomes with Image-based Interstitial Brachytherapy for Vaginal Cancer. Radiother Oncol. 2016;120 (3) :486-92.Abstract

PURPOSE: To compare clinical outcomes of image-based versus non-image-based interstitial brachytherapy (IBBT) for vaginal cancer. METHODS AND MATERIALS: Of 72 patients with vaginal cancer treated with brachytherapy (BT), 47 had image guidance (CT=31, MRI=16) and 25 did not. Kaplan-Meier (KM) estimates were generated for any recurrence, local control (LC), disease-free interval (DFI), and overall survival (OS) and Cox models were used to assess prognostic factors. RESULTS: Median age was 66 and median follow-up time was 24months. Median cumulative EQD2 dose was 80.8Gy in the non-IBBT group and 77Gy in the IBBT group. For non-IBBT versus IBBT, the 2-year KM LC was 71% vs. 93% (p=0.03); DFI was 54% vs. 86% (p=0.04); and OS 52% vs. 82% (p=0.35). On multivariate analysis, IBBT was associated with better DFI (HR 0.24, 95% CI 0.07-0.73). Having any 2 or more of chemotherapy, high-dose-rate (HDR) BT or IBBT (temporally correlated variables) significantly reduced risk of relapse (HR=0.33, 95% CI=0.13-0.83), compared to having none of these factors. CONCLUSION: Over time, the use of chemotherapy, HDR, and IBBT has increased in vaginal cancer. The combination of these factors resulted in the highest rates of disease control. Image-guided brachytherapy for vaginal cancer patients maximizes disease control.

Guenette JP, Tuncali K, Himes N, Tatli S, Lee TC. Spine Cryoablation: A Multimodality Image-Guided Approach for Tumors Adjacent to Major Neural Elements. AJNR Am J Neuroradiol. 2016;37 (12) :2396-9.Abstract

We report percutaneous cryoablation of spine tumors in 7 consecutive patients (5 men, 2 women [mean age, 47 years; range, 17-68 years]) by using intraprocedural image monitoring of ice ball margins to protect adjacent neural elements. Complete tumor ablation was achieved in all patients without neurologic complication. Pain relief was achieved in 4 of 5 (80%) patients; the patient with persistent pain was later found to have enlarging metastases at other sites.

Li M, Miller K, Joldes GR, Kikinis R, Wittek A. Biomechanical Model for Computing Deformations for Whole-body Image Registration: A Meshless Approach. Int J Numer Method Biomed Eng. 2016;32 (12).Abstract

Patient-specific biomechanical models have been advocated as a tool for predicting deformations of soft body organs/tissue for medical image registration (aligning two sets of images) when differences between the images are large. However, complex and irregular geometry of the body organs makes generation of patient-specific biomechanical models very time-consuming. Meshless discretisation has been proposed to solve this challenge. However, applications so far have been limited to 2D models and computing single organ deformations. In this study, 3D comprehensive patient-specific nonlinear biomechanical models implemented using meshless Total Lagrangian explicit dynamics algorithms are applied to predict a 3D deformation field for whole-body image registration. Unlike a conventional approach that requires dividing (segmenting) the image into non-overlapping constituents representing different organs/tissues, the mechanical properties are assigned using the fuzzy c-means algorithm without the image segmentation. Verification indicates that the deformations predicted using the proposed meshless approach are for practical purposes the same as those obtained using the previously validated finite element models. To quantitatively evaluate the accuracy of the predicted deformations, we determined the spatial misalignment between the registered (i.e. source images warped using the predicted deformations) and target images by computing the edge-based Hausdorff distance. The Hausdorff distance-based evaluation determines that our meshless models led to successful registration of the vast majority of the image features. Copyright © 2016 John Wiley & Sons, Ltd.

Kapur T, Tempany CM. Proceedings of the 8th Image Guided Therapy Workshop. Image Guided Therapy Workshop. 2016;8 :1-68. 2016 IGT Workshop Proceedings
Tempany CM. Multi-modal Image Guided Therapy: Novel Personalized Approaches in Oncology. Keynote Speech at the 2016 MICCAI Meeting. Int Conf Med Image Comput Comput Assist Interv. 2016 Oct;. 2016;19.Abstract Clare Tempany MICCAI 2016 Invited Talk
Guenette JP, Himes N, Giannopoulos AA, Kelil T, Mitsouras D, Lee TC. Computer-Based Vertebral Tumor Cryoablation Planning and Procedure Simulation Involving Two Cases using MRI-Visible 3D Printing and Advanced Visualization. AJR Am J Roentgenol. 2016;207 (5) :1128-31.Abstract

OBJECTIVE: We report the development and use of MRI-compatible and MRI-visible 3D printed models in conjunction with advanced visualization software models to plan and simulate safe access routes to achieve a theoretic zone of cryoablation for percutaneous image-guided treatment of a C7 pedicle osteoid osteoma and an L1 lamina osteoblastoma. Both models altered procedural planning and patient care. CONCLUSION: Patient-specific MRI-visible models can be helpful in planning complex percutaneous image-guided cryoablation procedures.

Chansakul T, Chen PN, Lee TC, Tierney T. Interventional MR Imaging for Deep-Brain Stimulation Electrode Placement. Radiology. 2016;281 (3) :940-6.Abstract

Purpose To investigate the safety and targeting errors of deep-brain stimulation (DBS) electrodes placed under interventional magnetic resonance (MR) imaging, which allows near real-time anatomic placement without physiologic mapping. Materials and Methods Retrospectively evaluated were 10 consecutive patients (five women, five men) with a mean age of 59.9 years (age range, 17-79 years). These patients underwent interventional MR imaging-guided DBS placement for movement disorders from September 2013 to August 2014 for placement of 19 DBS electrodes in cases where traditional frame-based surgery may be challenging because of the following: dystonia resulting in difficulty in placing the patients in frame, patient's inability or unwillingness to tolerate awake surgery, or anatomic anomaly or variant that could increase the risk of bleeding from microelectrode mapping. Outcomes measured included perioperative hemorrhage, death, and stroke, and electrode functionality assessed at 2 weeks after the operation. In addition, the mean radial error and mean trajectory error were calculated. Results No intraoperative neurologic complications (n = 10 [95% confidence interval: 0%, 31%]) were observed. One patient developed aspiration pneumonia in the postoperative period. Mean radial error was 0.7 mm ± 0.4 (standard deviation) and mean trajectory error was 0.5 mm ± 0.4. All leads delivered clinically effective stimulation. Conclusion Interventional MR imaging-guided DBS electrode placement may be a safe and effective alternative to conventional frame-based surgery in well-selected patients.

Zhang F, Savadjev P, Cai W, Song Y, Verma R, Westin C-F, O'Donnell LJ. Fiber Clustering Based White Matter Connectivity Analysis for Prediction of Autism Spectrum Disorder using Diffusion Tensor Imaging, in IEEE International Symposium on Biomedical Imaging. ; 2016 :564-7.Abstract

Autism Spectrum Disorder (ASD) has been suggested to associate with alterations 
in brain connectivity. In this study, we focus on a fiber clustering tractography segmentation 
strategy to observe white matter connectivity alterations in ASD. Compared to another 
popular parcellation-based approach for tractography segmentation based on cortical 
regions, we hypothesized that the clustering-based method could provide a more 
anatomically correspondent division of white matter. We applied this strategy to conduct a population-based group statistical analysis for the automated prediction of ASD. We obtained a maximum classification accuracy of 81.33% be- tween ASDs and controls, compared to the results of 78.00% from the parcellation-based method.

Zhang ISBI 2016 Paper
Preiswerk F, Toews M, Cheng C-C, Chiou J-yuan G, Mei C-S, Schaefer LF, Hoge WS, Schwartz BM, Panych LP, Madore B. Hybrid MRI Ultrasound Acquisitions, and Scannerless Real-time Imaging. Magn Reson Med. 2016.Abstract

PURPOSE: To combine MRI, ultrasound, and computer science methodologies toward generating MRI contrast at the high frame rates of ultrasound, inside and even outside the MRI bore. METHODS: A small transducer, held onto the abdomen with an adhesive bandage, collected ultrasound signals during MRI. Based on these ultrasound signals and their correlations with MRI, a machine-learning algorithm created synthetic MR images at frame rates up to 100 per second. In one particular implementation, volunteers were taken out of the MRI bore with the ultrasound sensor still in place, and MR images were generated on the basis of ultrasound signal and learned correlations alone in a "scannerless" manner. RESULTS: Hybrid ultrasound-MRI data were acquired in eight separate imaging sessions. Locations of liver features, in synthetic images, were compared with those from acquired images: The mean error was 1.0 pixel (2.1 mm), with best case 0.4 and worst case 4.1 pixels (in the presence of heavy coughing). For results from outside the bore, qualitative validation involved optically tracked ultrasound imaging with/without coughing. CONCLUSION: The proposed setup can generate an accurate stream of high-speed MR images, up to 100 frames per second, inside or even outside the MR bore. Magn Reson Med, 2016. © 2016 International Society for Magnetic Resonance in Medicine.

Schmidt EJ, Watkins RD, Zviman MM, Guttman MA, Wang W, Halperin HA. A Magnetic Resonance Imaging–Conditional External Cardiac De brillator for Resuscitation within the Magnetic Resonance Imaging Scanner Bore. Circ Cardiovasc Imaging. 2016;9 :e005091.Abstract

Subjects undergoing cardiac arrest within a magnetic resonance imaging (MRI) scanner are currently removed from the bore and then from the MRI suite, before the delivery of cardiopulmonary resuscitation and de brillation, potentially increasing the risk of mortality. This precludes many higher-risk (acute ischemic and acute stroke) patients from undergoing MRI and MRI-guided intervention. An MRI-conditional cardiac de brillator should enable scanning with de brillation pads attached and the generator ON, enabling application of de brillation within the seconds of MRI after a cardiac event. An MRI-conditional external de brillator may improve patient acceptance for MRI procedures. Methods and Results—A commercial external de brillator was rendered 1.5 Tesla MRI-conditional by the addition of novel radiofrequency lters between the generator and commercial disposable surface pads. The radiofrequency lters reduced emission into the MRI scanner and prevented cable/surface pad heating during imaging, while preserving all the de brillator monitoring and delivery functions. Human volunteers were imaged using high speci c absorption rate sequences to validate MRI image quality and lack of heating. Swine were electrically brillated (n=4) and thereafter de brillated both outside and inside the MRI bore. MRI image quality was reduced by 0.8 or 1.6 dB, with the generator in monitoring mode and operating on battery or AC power, respectively. Commercial surface pads did not create artifacts deeper than 6 mm below the skin surface. Radiofrequency heating was within US Food and Drug Administration guidelines. De brillation was completely successful inside and outside the MRI bore. Conclusions—A prototype MRI-conditional de brillation system successfully de brillated in the MRI without degrading the image quality or increasing the time needed for de brillation. It can increase patient acceptance for MRI procedures.

Bersvendsen J, Toews M, Danudibroto A, Wells WM, Urheim S, San José Estépar R, Samset E. Robust Spatio-Temporal Registration of 4D Cardiac Ultrasound Sequences. Proc SPIE Int Soc Opt Eng. 2016;9790.Abstract
Registration of multiple 3D ultrasound sectors in order to provide an extended field of view is important for the appreciation of larger anatomical structures at high spatial and temporal resolution. In this paper, we present a method for fully automatic spatio-temporal registration between two partially overlapping 3D ultrasound sequences. The temporal alignment is solved by aligning the normalized cross correlation-over-time curves of the sequences. For the spatial alignment, corresponding 3D Scale Invariant Feature Transform (SIFT) features are extracted from all frames of both sequences independently of the temporal alignment. A rigid transform is then calculated by least squares minimization in combination with random sample consensus. The method is applied to 16 echocardiographic sequences of the left and right ventricles and evaluated against manually annotated temporal events and spatial anatomical landmarks. The mean distances between manually identified landmarks in the left and right ventricles after automatic registration were (mean ± SD) 4.3 ± 1.2 mm compared to a reference error of 2.8 ± 0.6 mm with manual registration. For the temporal alignment, the absolute errors in valvular event times were 14.4 ± 11.6 ms for Aortic Valve (AV) opening, 18.6 ± 16.0 ms for AV closing, and 34.6 ± 26.4 ms for mitral valve opening, compared to a mean inter-frame time of 29 ms.

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