Publications

2013
Jayender J, Gombos E, Chikarmane S, Dabydeen D, Jolesz FA, Vosburgh KG. Statistical Learning Algorithm for in situ and Invasive Breast Carcinoma Segmentation. Comput Med Imaging Graph. 2013;37 (4) :281-92.Abstract

Dynamic Contrast Enhanced MRI (DCE-MRI) has proven to be a highly sensitive imaging modality in diagnosing breast cancers. However, analyzing the DCE-MRI is time-consuming and prone to errors due to the large volume of data. Mathematical models to quantify contrast perfusion, such as the black box methods and pharmacokinetic analysis, are inaccurate, sensitive to noise and depend on a large number of external factors such as imaging parameters, patient physiology, arterial input function, and fitting algorithms, leading to inaccurate diagnosis. In this paper, we have developed a novel Statistical Learning Algorithm for Tumor Segmentation (SLATS) based on Hidden Markov Models to auto-segment regions of angiogenesis, corresponding to tumor. The SLATS algorithm has been trained to identify voxels belonging to the tumor class using the time-intensity curve, first and second derivatives of the intensity curves ("velocity" and "acceleration" respectively) and a composite vector consisting of a concatenation of the intensity, velocity and acceleration vectors. The results of SLATS trained for the four vectors has been shown for 22 Invasive Ductal Carcinoma (IDC) and 19 Ductal Carcinoma In Situ (DCIS) cases. The SLATS trained for the velocity tuple shows the best performance in delineating the tumors when compared with the segmentation performed by an expert radiologist and the output of a commercially available software, CADstream.

Vosburgh KG, Golby AJ, Pieper S. Surgery, Virtual Reality, and the Future. Stud Health Technol Inform. 2013;184 :7-13.Abstract

MMVR has provided the leading forum for the multidisciplinary interaction and development of the use of Virtual Reality (VR) techniques in medicine, particularly in surgical practice. Here we look back at the foundations of our field, focusing on the use of VR in Surgery and similar interventional procedures, sum up the current status, and describe the challenges and opportunities going forward.

Schwartz BM, McDannold NJ. Ultrasound Echoes as Biometric Navigators. Magn Reson Med. 2013;69 (4) :1023-33.Abstract

We demonstrate a new method of using ultrasound data to achieve prospective motion compensation in MRI, especially for respiratory motion during interventional MRI procedures in moving organs such as the liver. The method relies on fingerprint-like biometrically distinct ultrasound echo patterns produced by different locations in tissue, which are collated with geometrical information from MRI during a training stage to form a mapping table that relates ultrasound measurements to positions. During prospective correction, the system makes frequent ultrasound measurements and uses the map to determine the corresponding position. Results in motorized linear motion phantoms and freely breathing animals indicate that the system performs well. Apparent motion is reduced by up to 97.8%, and motion artifacts are reduced or eliminated in two-dimensional spoiled gradient-echo images. The motion compensation is sufficient to permit MRI thermometry of focused ultrasound heating during respiratory-like motion, with results similar to those obtained in the absence of motion. This new technique may have applications for MRI thermometry and other dynamic imaging in the abdomen during free breathing.

Pernelle G, Mehrtash A, Barber L, Damato A, Wang W, Seethamraju RT, Schmidt E, Cormack RA, Wells III WM, Viswanathan A, et al. Validation of Catheter Segmentation for MR-guided Gynecologic Cancer Brachytherapy. Med Image Comput Comput Assist Interv. 2013;16 (Pt 3) :380-7.Abstract

Segmentation of interstitial catheters from MRI needs to be addressed in order for MRI-based brachytherapy treatment planning to become part of the clinical practice of gynecologic cancer radiotherapy. This paper presents a validation study of a novel image-processing method for catheter segmentation. The method extends the distal catheter tip, interactively provided by the physician, to its proximal end, using knowledge of catheter geometry and appearance in MRI sequences. The validation study consisted of comparison of the algorithm results to expert manual segmentations, first on images of a phantom, and then on patient MRI images obtained during MRI-guided insertion of brachytherapy catheters for the treatment of gynecologic cancer. In the phantom experiment, the maximum disagreement between automatic and manual segmentation of the same MRI image, as computed using the Hausdorf distance, was 1.5 mm, which is of the same order as the MR image spatial resolution, while the disagreement between automatic segmentation of MR images and "ground truth", manual segmentation of CT images, was 3.5 mm. The segmentation method was applied to an IRB-approved retrospective database of 10 interstitial brachytherapy patients which included a total of 101 catheters. Compared with manual expert segmentations, the automatic method correctly segmented 93 out of 101 catheters, at an average rate of 0.3 seconds per catheter using a 3 GHz Intel Core i7 computer with 16 GB RAM and running Mac OS X 10.7. These results suggest that the proposed catheter segmentation is both technically and clinically feasible.

Song S-E, Hata N, Iordachita I, Fichtinger G, Tempany CM, Tokuda J. A Workspace-orientated Needle-guiding Robot for 3T MRI-guided Transperineal Prostate Intervention: Evaluation of in-bore Workspace and MRI Compatibility. Int J Med Robot. 2013;9 (1) :67-74.Abstract

BACKGROUND: Magnetic resonance imaging (MRI)-guided prostate interventions have been introduced to enhance the cancer detection. For accurate needle positioning, in-bore-operated robotic systems have been developed and optimal use of the confined in-bore space become a critical engineering challenge. METHODS: As preliminary evaluation of our prostate intervention robot, we conducted a workspace design analysis, using a new evaluation method that we developed for in-bore-operated robots for transperineal prostate interventions, and an MRI compatibility study. RESULTS: The workspace analysis resulted in the effective workspace (VW ) of 0.32, which is greater than that of our early prototype, despite the current robot being ca. 50% larger than the early prototype in sectional space. The MRI compatibility study resulted in < 15% signal:noise ratio (SNR) reduction. CONCLUSIONS: The new workspace evaluation method quantifies the workspace utilization of the in-bore-operated robots for MRI-guided transperineal prostate interventions, providing a useful tool for evaluation and new robot design. The robot creates insignificant electromagnetic noise during typical prostate imaging sequences.

2012
Kapur T, Jolesz FA, Lewin JS, Kahn T. Proceedings of the 9th Interventional MRI Symposium. 9th Interventional MRI Symposium. 2012;9 :1-156. 2012 iMRI Symposium Proceedings
Kapur T, Tempany CM, Jolesz FA. Proceedings of the 5th Image Guided Therapy Workshop. Image Guided Therapy Workshop. 2012;5 :1-70. 2012 IGT Workshop Proceedings
Park BK, Morrison PR, Tatli S, Govindarajulu U, Tuncali K, Judy P, Shyn PB, Silverman SG. Estimated effective dose of CT-guided percutaneous cryoablation of liver tumors. Eur J Radiol. 2012;81 (8) :1702-6.Abstract
PURPOSE: To estimate effective dose during CT-guided cryoablation of liver tumors, and to assess which procedural factors contribute most to dose. MATERIALS AND METHODS: Our institutional review board approved this retrospective, HIPAA-compliant study. A total of 20 CT-guided percutaneous liver tumor cryoablation procedures were performed in 18 patients. Effective dose was determined by multiplying the dose length product for each CT scan obtained during the procedure by a conversion factor (0.015mSv/mGy-cm), and calculating the sum for each phase of the procedure: planning, targeting, monitoring, and post-ablation survey. Effective dose of each phase was compared using a repeated measures analysis. Using Spearman correlation coefficients, effective doses were correlated with procedural factors including number of scans, ratio of targeting distance to tumor size, anesthesia type, number of applicators, performance of ancillary procedures (hydrodissection and biopsy), and use of CT fluoroscopy. RESULTS: Effective dose per procedure was 72±18mSv. The effective dose of targeting (37.5±12.5mSv) was the largest component compared to the effective dose of the planning phase (4.8±2.2mSv), the monitoring phase (25.5±6.8mSv), and the post-ablation survey (4.1±1.9mSv) phase (p<0.05). Effective dose correlated positively only with the number of scans (p<0.01). CONCLUSIONS: The effective dose of CT-guided percutaneous cryoablation of liver tumors can be substantial. Reducing the number of scans during the procedure is likely to have the greatest effect on lowering dose.
Egger J, Colen RR, Freisleben B, Nimsky C. Manual refinement system for graph-based segmentation results in the medical domain. J Med Syst. 2012;36 (5) :2829-39.Abstract
The basic principle of graph-based approaches for image segmentation is to interpret an image as a graph, where the nodes of the graph represent 2D pixels or 3D voxels of the image. The weighted edges of the graph are obtained by intensity differences in the image. Once the graph is constructed, the minimal cost closed set on the graph can be computed via a polynomial time s-t cut, dividing the graph into two parts: the object and the background. However, no segmentation method provides perfect results, so additional manual editing is required, especially in the sensitive field of medical image processing. In this study, we present a manual refinement method that takes advantage of the basic design of graph-based image segmentation algorithms. Our approach restricts a graph-cut by using additional user-defined seed points to set up fixed nodes in the graph. The advantage is that manual edits can be integrated intuitively and quickly into the segmentation result of a graph-based approach. The method can be applied to both 2D and 3D objects that have to be segmented. Experimental results for synthetic and real images are presented to demonstrate the feasibility of our approach.
Seifabadi R, Song S-E, Krieger A, Cho NB, Tokuda J, Fichtinger G, Iordachita I. Robotic system for MRI-guided prostate biopsy: feasibility of teleoperated needle insertion and ex vivo phantom study. Int J Comput Assist Radiol Surg. 2012;7 (2) :181-90.Abstract
PURPOSE: Magnetic Resonance Imaging (MRI) combined with robotic assistance has the potential to improve on clinical outcomes of biopsy and local treatment of prostate cancer. METHODS: We report the workspace optimization and phantom evaluation of a five Degree of Freedom (DOF) parallel pneumatically actuated modular robot for MRI-guided prostate biopsy. To shorten procedure time and consequently increase patient comfort and system accuracy, a prototype of a MRI-compatible master-slave needle driver module using piezo motors was also added to the base robot. RESULTS: Variable size workspace was achieved using appropriate link length, compared with the previous design. The 5-DOF targeting accuracy demonstrated an average error of 2.5 mm (STD = 1.37 mm) in a realistic phantom inside a 3T magnet with a bevel-tip 18G needle. The average position tracking error of the master-slave needle driver was always below 0.1 mm. CONCLUSION: Phantom experiments showed sufficient accuracy for manual prostate biopsy. Also, the implementation of teleoperated needle insertion was feasible and accurate. These two together suggest the feasibility of accurate fully actuated needle placement into prostate while keeping the clinician supervision over the task.
Mei C-S, Mulkern RV, Oshio K, Chen N-kuei, Madore B, Panych LP, Hynynen K, McDannold NJ. Ultrafast 1D MR thermometry using phase or frequency mapping. MAGMA. 2012;25 (1) :5-14.Abstract
OBJECT: To develop an ultrafast MRI-based temperature monitoring method for application during rapid ultrasound exposures in moving organs. MATERIALS AND METHODS: A slice selective 90° - 180° pair of RF pulses was used to solicit an echo from a column, which was then sampled with a train of gradient echoes. In a gel phantom, phase changes of each echo were compared to standard gradient-echo thermometry, and temperature monitoring was tested during focused ultrasound sonications. Signal-to-noise ratio (SNR) performance was evaluated in vivo in a rabbit brain, and feasibility was tested in a human heart. RESULTS: The correlation between each echo in the acquisition and MRI-based temperature measurements was good (R = 0.98 ± 0.03). A temperature sampling rate of 19 Hz was achieved at 3T in the gel phantom. It was possible to acquire the water frequency in the beating heart muscle with 5-Hz sampling rate during a breath hold. CONCLUSION: Ultrafast thermometry via phase or frequency monitoring along single columns was demonstrated. With a temporal resolution around 50 ms, it may be possible to monitor focal heating produced by short ultrasound pulses.
Wu W, Rigolo L, O'Donnell LJ, Norton I, Shriver S, Golby AJ. Visual pathway study using in vivo diffusion tensor imaging tractography to complement classic anatomy. Neurosurgery. 2012;70 (1 Suppl Operative) :145-56; discussion 156.Abstract
BACKGROUND: Knowledge of the individual course of the optic radiations (ORs) is important to avoid postoperative visual deficits. Cadaveric studies of the visual pathways are limited because it has not been possible to separate the OR from neighboring tracts accurately and results may not apply to individual patients. Diffusion tensor imaging studies may be able to demonstrate the relationships between the OR and neighboring fibers in vivo in individual subjects. OBJECTIVE: To use diffusion tensor imaging tractography to study the OR and the Meyer loop (ML) anatomy in vivo. METHODS: Ten healthy subjects underwent magnetic resonance imaging with diffusion imaging at 3 T. With the use of a fiducial-based diffusion tensor imaging tractography tool (Slicer 3.3), seeds were placed near the lateral geniculate nucleus to reconstruct individual visual pathways and neighboring tracts. Projections of the ORs onto 3-dimensional brain models were shown individually to quantify relationships to key landmarks. RESULTS: Two patterns of visual pathways were found. The OR ran more commonly deep in the whole superior and middle temporal gyri and superior temporal sulcus. The OR was closely surrounded in all cases by an inferior longitudinal fascicle and a parieto/occipito/temporo-pontine fascicle. The mean left and right distances between the tip of the OR and temporal pole were 39.8 ± 3.8 and 40.6 ± 5.7 mm, respectively. CONCLUSION: Diffusion tensor imaging tractography provides a practical complementary method to study the OR and the Meyer loop anatomy in vivo with reference to individual 3-dimensional brain anatomy.
Mamata H, Tokuda J, Gill RR, Padera RF, Lenkinski RE, Sugarbaker DJ, Butler JP, Hatabu H. Clinical application of pharmacokinetic analysis as a biomarker of solitary pulmonary nodules: dynamic contrast-enhanced MR imaging. Magn Reson Med. 2012;68 (5) :1614-22.Abstract
The purpose of this study is to evaluate perfusion indices and pharmacokinetic parameters in solitary pulmonary nodules (SPNs). Thirty patients of 34 enrolled with SPNs (15-30 mm) were evaluated in this study. T1 and T2-weighted structural images and 2D turbo FLASH perfusion images were acquired with shallow free breathing. B-spline nonrigid image registration and optimization by χ² test against pharmacokinetic model curve were performed on dynamic contrast-enhanced MRI. This allowed voxel-by-voxel calculation of k(ep) , the rate constant for tracer transport to and from plasma and the extravascular extracellular space. Mean transit time, time-to-peak, initial slope, and maximum enhancement (E(max) ) were calculated from time-intensity curves fitted to a gamma variate function. After blinded data analysis, correlation with tissue histology from surgical resection or biopsy samples was performed. Histologic evaluation revealed 25 malignant and five benign SPNs. All benign SPNs had k(ep) < 1.0 min⁻¹. Nineteen of 25 (76%) malignant SPNs showed k(ep) > 1.0 min⁻¹. Sensitivity to diagnose malignant SPNs at a cutoff of k(ep) = 1.0 min⁻¹ was 76%, specificity was 100%, positive predictive value was 100%, negative predictive value was 45%, and accuracy was 80%. Of all indices studied, k(ep) was the most significant in differentiating malignant from benign SPNs.
Danagoulian GS, Qin L, Nayak KS, Colen RR, Mukundan S, Harris MB, Jolesz FA, Shankaranarayanan A, Copen WA, Schmidt EJ. Comparison of wideband steady-state free precession and T₂-weighted fast spin echo in spine disorder assessment at 1.5 and 3 T. Magn Reson Med. 2012;68 (5) :1527-35.Abstract
Wideband steady-state free precession (WB-SSFP) is a modification of balanced steady-state free precession utilizing alternating repetition times to reduce susceptibility-induced balanced steady-state free precession limitations, allowing its use for high-resolution myelographic-contrast spinal imaging. Intertissue contrast and spatial resolution of complete-spine-coverage 3D WB-SSFP were compared with those of 2D T₂-weighted fast spin echo, currently the standard for spine T₂-imaging. Six normal subjects were imaged at 1.5 and 3 T. The signal-to-noise ratio efficiency (SNR per unit-time and unit-volume) of several tissues was measured, along with four intertissue contrast-to-noise ratios; nerve-ganglia:fat, intradural-nerves:cerebrospinal fluid, nerve-ganglia:muscle, and muscle:fat. Patients with degenerative and traumatic spine disorders were imaged at both MRI fields to demonstrate WB-SSFP clinical advantages and disadvantages. At 3 T, WB-SSFP provided spinal contrast-to-noise ratios 3.7-5.2 times that of fast spin echo. At 1.5 T, WB-SSFP contrast-to-noise ratio was 3-3.5 times that of fast spin echo, excluding a 1.7 ratio for intradural-nerves:cerebrospinal fluid. WB-SSFP signal-to-noise ratio efficiency was also higher. Three-dimensional WB-SSFP disadvantages relative to 2D fast spin echo are reduced edema hyperintensity, reduced muscle signal, and higher motion sensitivity. WB-SSFP's high resolution and contrast-to-noise ratio improved visualization of intradural nerve bundles, foraminal nerve roots, and extradural nerve bundles, improving detection of nerve compression in radiculopathy and spinal-stenosis. WB-SSFP's high resolution permitted reformatting into orthogonal planes, providing distinct advantages in gauging fine spine pathology.
Srinivasan S, Hu P, Kissinger KV, Goddu B, Goepfert L, Schmidt EJ, Kozerke S, Nezafat R. Free-breathing 3D whole-heart black-blood imaging with motion sensitized driven equilibrium. J Magn Reson Imaging. 2012;36 (2) :379-86.Abstract
PURPOSE: To assess the efficacy and robustness of motion sensitized driven equilibrium (MSDE) for blood suppression in volumetric 3D whole-heart cardiac MR. MATERIALS AND METHODS: To investigate the efficacy of MSDE on blood suppression and myocardial signal-to-noise ratio (SNR) loss on different imaging sequences, seven healthy adult subjects were imaged using 3D electrocardiogram (ECG)-triggered MSDE-prep T(1) -weighted turbo spin echo (TSE), and spoiled gradient echo (GRE), after optimization of MSDE parameters in a pilot study of five subjects. Imaging artifacts, myocardial and blood SNR were assessed. Subsequently, the feasibility of isotropic spatial resolution MSDE-prep black-blood was assessed in six subjects. Finally, 15 patients with known or suspected cardiovascular disease were recruited to be imaged using a conventional multislice 2D double inversion recovery (DIR) TSE imaging sequence and a 3D MSDE-prep spoiled GRE. RESULTS: The MSDE-prep yielded significant blood suppression (75%-92%), enabling a volumetric 3D black-blood assessment of the whole heart with significantly improved visualization of the chamber walls. The MSDE-prep also allowed successful acquisition of black-blood images with isotropic spatial resolution. In the patient study, 3D black-blood MSDE-prep and DIR resulted in similar blood suppression in left ventricle and right ventricle walls but the MSDE-prep had superior myocardial signal and wall sharpness. CONCLUSION: MSDE-prep allows volumetric black-blood imaging of the heart.
Madore B, Meral CF. Reconstruction algorithm for improved ultrasound image quality. IEEE Trans Ultrason Ferroelectr Freq Control. 2012;59 (2) :217-30.Abstract
A new algorithm is proposed for reconstructing raw RF data into ultrasound images. Previous delay-and-sum beamforming reconstruction algorithms are essentially one-dimensional, because a sum is performed across all receiving elements. In contrast, the present approach is two-dimensional, potentially allowing any time point from any receiving element to contribute to any pixel location. Computer-intensive matrix inversions are performed once, in advance, to create a reconstruction matrix that can be reused indefinitely for a given probe and imaging geometry. Individual images are generated through a single matrix multiplication with the raw RF data, without any need for separate envelope detection or gridding steps. Raw RF data sets were acquired using a commercially available digital ultrasound engine for three imaging geometries: a 64-element array with a rectangular field-of- view (FOV), the same probe with a sector-shaped FOV, and a 128-element array with rectangular FOV. The acquired data were reconstructed using our proposed method and a delay- and-sum beamforming algorithm for comparison purposes. Point spread function (PSF) measurements from metal wires in a water bath showed that the proposed method was able to reduce the size of the PSF and its spatial integral by about 20 to 38%. Images from a commercially available quality-assurance phantom had greater spatial resolution and contrast when reconstructed with the proposed approach.
Shenton ME, Hamoda HM, Schneiderman JS, Bouix S, Pasternak O, Rathi Y, Vu M-A, Purohit MP, Helmer K, Koerte I, et al. A review of magnetic resonance imaging and diffusion tensor imaging findings in mild traumatic brain injury. Brain Imaging Behav. 2012;6 (2) :137-92.Abstract
Mild traumatic brain injury (mTBI), also referred to as concussion, remains a controversial diagnosis because the brain often appears quite normal on conventional computed tomography (CT) and magnetic resonance imaging (MRI) scans. Such conventional tools, however, do not adequately depict brain injury in mTBI because they are not sensitive to detecting diffuse axonal injuries (DAI), also described as traumatic axonal injuries (TAI), the major brain injuries in mTBI. Furthermore, for the 15 to 30 % of those diagnosed with mTBI on the basis of cognitive and clinical symptoms, i.e., the "miserable minority," the cognitive and physical symptoms do not resolve following the first 3 months post-injury. Instead, they persist, and in some cases lead to long-term disability. The explanation given for these chronic symptoms, i.e., postconcussive syndrome, particularly in cases where there is no discernible radiological evidence for brain injury, has led some to posit a psychogenic origin. Such attributions are made all the easier since both posttraumatic stress disorder (PTSD) and depression are frequently co-morbid with mTBI. The challenge is thus to use neuroimaging tools that are sensitive to DAI/TAI, such as diffusion tensor imaging (DTI), in order to detect brain injuries in mTBI. Of note here, recent advances in neuroimaging techniques, such as DTI, make it possible to characterize better extant brain abnormalities in mTBI. These advances may lead to the development of biomarkers of injury, as well as to staging of reorganization and reversal of white matter changes following injury, and to the ability to track and to characterize changes in brain injury over time. Such tools will likely be used in future research to evaluate treatment efficacy, given their enhanced sensitivity to alterations in the brain. In this article we review the incidence of mTBI and the importance of characterizing this patient population using objective radiological measures. Evidence is presented for detecting brain abnormalities in mTBI based on studies that use advanced neuroimaging techniques. Taken together, these findings suggest that more sensitive neuroimaging tools improve the detection of brain abnormalities (i.e., diagnosis) in mTBI. These tools will likely also provide important information relevant to outcome (prognosis), as well as play an important role in longitudinal studies that are needed to understand the dynamic nature of brain injury in mTBI. Additionally, summary tables of MRI and DTI findings are included. We believe that the enhanced sensitivity of newer and more advanced neuroimaging techniques for identifying areas of brain damage in mTBI will be important for documenting the biological basis of postconcussive symptoms, which are likely associated with subtle brain alterations, alterations that have heretofore gone undetected due to the lack of sensitivity of earlier neuroimaging techniques. Nonetheless, it is noteworthy to point out that detecting brain abnormalities in mTBI does not mean that other disorders of a more psychogenic origin are not co-morbid with mTBI and equally important to treat. They arguably are. The controversy of psychogenic versus physiogenic, however, is not productive because the psychogenic view does not carefully consider the limitations of conventional neuroimaging techniques in detecting subtle brain injuries in mTBI, and the physiogenic view does not carefully consider the fact that PTSD and depression, and other co-morbid conditions, may be present in those suffering from mTBI. Finally, we end with a discussion of future directions in research that will lead to the improved care of patients diagnosed with mTBI.
Egger J, Kapur T, Dukatz T, Kolodziej M, Zukić D, Freisleben B, Nimsky C. Square-cut: a segmentation algorithm on the basis of a rectangle shape. PLoS One. 2012;7 (2) :e31064.Abstract
We present a rectangle-based segmentation algorithm that sets up a graph and performs a graph cut to separate an object from the background. However, graph-based algorithms distribute the graph's nodes uniformly and equidistantly on the image. Then, a smoothness term is added to force the cut to prefer a particular shape. This strategy does not allow the cut to prefer a certain structure, especially when areas of the object are indistinguishable from the background. We solve this problem by referring to a rectangle shape of the object when sampling the graph nodes, i.e., the nodes are distributed non-uniformly and non-equidistantly on the image. This strategy can be useful, when areas of the object are indistinguishable from the background. For evaluation, we focus on vertebrae images from Magnetic Resonance Imaging (MRI) datasets to support the time consuming manual slice-by-slice segmentation performed by physicians. The ground truth of the vertebrae boundaries were manually extracted by two clinical experts (neurological surgeons) with several years of experience in spine surgery and afterwards compared with the automatic segmentation results of the proposed scheme yielding an average Dice Similarity Coefficient (DSC) of 90.97±2.2%.
Egger J, Freisleben B, Nimsky C, Kapur T. Template-cut: a pattern-based segmentation paradigm. Sci Rep. 2012;2 :420.Abstract
We present a scale-invariant, template-based segmentation paradigm that sets up a graph and performs a graph cut to separate an object from the background. Typically graph-based schemes distribute the nodes of the graph uniformly and equidistantly on the image, and use a regularizer to bias the cut towards a particular shape. The strategy of uniform and equidistant nodes does not allow the cut to prefer more complex structures, especially when areas of the object are indistinguishable from the background. We propose a solution by introducing the concept of a "template shape" of the target object in which the nodes are sampled non-uniformly and non-equidistantly on the image. We evaluate it on 2D-images where the object's textures and backgrounds are similar, and large areas of the object have the same gray level appearance as the background. We also evaluate it in 3D on 60 brain tumor datasets for neurosurgical planning purposes.
Treat LH, McDannold N, Zhang Y, Vykhodtseva N, Hynynen K. Improved anti-tumor effect of liposomal doxorubicin after targeted blood-brain barrier disruption by MRI-guided focused ultrasound in rat glioma. Ultrasound Med Biol. 2012;38 (10) :1716-25.Abstract
The blood-brain barrier (BBB) inhibits the entry of the majority of chemotherapeutic agents into the brain. Previous studies have illustrated the feasibility of drug delivery across the BBB using focused ultrasound (FUS) and microbubbles. Here, we investigated the effect of FUS-enhanced delivery of doxorubicin on survival in rats with and 9L gliosarcoma cells inoculated in the brain. Each rat received either: (1) no treatment (control; N = 11), (2) FUS only (N = 9), (3) IV liposomal doxorubicin (DOX only; N = 17), or (4) FUS with concurrent IV injections of liposomal doxorubicin (FUS+DOX; N = 20). Post-treatment by magnetic resonance imaging (MRI) showed that FUS+DOX reduced tumor growth compared with DOX only. Further, we observed a modest but significant increase in median survival time after a single treatment FUS+DOX treatment (p = 0.0007), whereas neither DOX nor FUS had any significant impact on survival on its own. These results suggest that combined ultrasound-mediated BBB disruption may significantly increase the antineoplastic efficacy of liposomal doxorubicin in the brain.

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