Publications by Year: 2013

2013
Pernelle G, Kapur T, Mehrtash A, Penzkofer T, Damato A, Barber L, Schmidt E, Viswanathan A, Cormack RA. Automated Interstitial Brachytherapy Catheter Localization from Volumetric MR Data. Med Phys. 2013;40 (6Part2) :94.Abstract

PURPOSE: This work seeks to validate an automatic method for extracting interstitial catheter locations from volumetric MR data. METHODS: A 3D b-SSFP (balanced Steady State Free Precession) MRI sequence was used to enhance catheter detection, utilizing a controlled enlargement of size caused by magnetic susceptibility artifacts . Starting with a user-provided needle-tip location, the needle extraction algorithm searched the MR image for segments that maximized the "needle likelihood" and iteratively fit Bezier curves to these segments. To validate the geometry of extracted catheters, a phantom was constructed from transparent gel wax. An obturator was placed at the center of a transparent plastic container, and wax gel was melted and poured around it. A Syed-Neblett template was then placed at one end of the obturator and 12 MR compatible catheters were inserted into the gel. The catheter trajectories extracted from the MR scan by the algorithm were compared to a CT scan. The algorithm was applied to patient scans under an IRB approved protocol. RESULTS: The volumetric b-SSFP sequence produced an artifact enhancement that enabled brachytherapy catheters to be distinguished from other signal voids. Comparison in a phantom of catheter locations extracted automatically from MR to those extracted manually from CT showed agreement of 3.5 mm Hausdorff Distance. When applied to patient scans, the presence of low signal regions between template and the target tumor required some manual intervention to ensure proper catheter extraction. CONCLUSION: An automatic algorithm for extracting interstitial catheter locations from MR scans has been developed. Using a b-SSFP sequence allowed an iterative curve fitting algorithm to track MR artifacts from user provided tips to template. This algorithm should prove helpful to facilitate MR based treatment planning for interstitial brachytherapy.

Wang W, Gao Y, Mehrtash A, Seethmaraju R, Kapur T, Vishwanathan A, Schmidt E, Cormack RA. Real-Time Catheter Tracking and Visualization in MR-Guided Brachytherapy. Med Phys. 2013;40 (6Part30) :505.Abstract

PURPOSE: The challenge of catheter-tip visualization for interstitial needle placement in gynecologic brachytherapy remains unmet. We evaluate an approach to actively track tip locations and visualize catheter trajectories and surrounding soft-tissue in real-time during an intervention. The methods include development of clinical needles with magnetic resonance (MR) tracked microcoils, an MR tracking and rapid imaging sequence and integration with a graphical workstation for visualization. METHODS: An active tracking device was built based on a commercial catheter which consists of a hollow tube and a central needle with microcoils at the distal end. An MR tracking sequence was developed (isotropic resolution: 0.6 mm, frame rate: 40 updates/sec). It runs continuously during navigation or interleaves with real-time imaging (3 frames/sec), where image position/orientation are automatically set to provide visualization of anatomy around the catheter. The catheter-tip position/orientation was passed to the workstation for visualization. Needle shapes were superimposed on pre-acquired high-resolution images or on the intra-procedural images. RESULTS: MR-guided catheter placement procedures were conducted in a gel phantom and an animal model. High-resolution 3D MR scans were acquired and loaded into the workstation for navigation. During insertion, the catheter tips were visualized advancing on a 3D anatomic model and on assigned planes. Real-time imaging with slice continuously updating at the instantaneous tip positions was also performed. Both methods served well to guide catheter placement. After insertion, complete catheter trajectories were rendered by recording tip positions as needles were pulled out and overlaid on the images, to support treatment planning. CONCLUSION: We demonstrated the feasibility of active catheter tracking and visualization in MR-guided brachytherapy. This will facilitate accurate and time-efficient catheter insertion by providing on-line identification of catheter position, and visualization of anatomy ahead of the catheter tip. This enables identifying preferential paths to target locations, and reduces the risk to critical organs. FUNDING SOURCES: NIH P41 EB015898; AHA 10SDG261039.

Cormack RA, Federov A, Fennesy F, Penzkofer T, Tuncali K, Tempany CM, Nguyen P. Constraints on Focal Brachytherapy Treatments for Early Stage Prostate Cancer: A Comparison of Isotopes. Med Phys. 2013;40 (6Part3) :104.Abstract

PURPOSE: Patients with favorable-risk prostate cancer may be attracted to focal therapy aimed at the dominant intraprostatic lesion as a middle ground between the morbidity of full gland treatment and the uncertainty of observation. The various approaches involve isotopes having different energies implying different dosimetric characteristics. This work seeks to determine if choice of isotope makes a substantial difference in the fraction of prostate that may be implanted as a function of implant volume and rectal dose limit. METHODS: Representations of prostate, urethra and rectum were generated from MR scans as part of an IRB approved medical record review of patients with confirmed low risk prostate cancer. Anatomic structures were digitized on a 2.5 × 2.5 × 5.0 mm grid. Focal implants were simulated by placement of a single source. All prostate points 5 mm or further from a sensitive structure were considered as potential implant location. Dose distributions were calculated for implants of 125I, 109Pd and 192Ir. The fraction of potential implant locations that respected normal tissue constraints (rectum: 10-100% of Rx, urethra 100-200% of Rx) as a function of prescription radius was recorded. RESULTS: The fraction of the prostate implantable for a given prescription radius primarily depends on the normal tissue dose limits that are to be respected with a secondary dependence on isotope. Prescription radius less than 1 cm and rectal dose constraints greater than 50% of prescription dose allow a substantial portion of the gland to be considered for a focal implant. Detailed results are presented as a function of normal tissue constraints and prescription radius. CONCLUSION: While isotope choice does affect the implantable volume, the effect is secondary to the choice of prescription parameters. Choice of focal brachytherapy approach may be made based on consideration of duration of irradiation or clinical concerns.

Wright J. Surgery: The Eyes of the Operation. Nature. 2013;502 (7473) :S88-9.Abstract

Real-time imaging of a patient's body is guiding surgeons and radiologists past healthy tissue to the diseased cells.

 

In the early 1990s, Jolesz pioneered the use of MRI in operations, taking scans during brain surgery for the first time. When this was successful, it became clear that the best way to guide treatment would be to combine as many forms of imaging as possible, says Jolesz. In September 2011, a grant from the US National Institutes of Health led to the Advanced Multimodality Image Guided Operating (AMIGO) suite — a three-room operating suite that includes an MRI scanner, a CT and positron emission tomography (PET) scanner, and an advanced three-dimensional ultrasound and navigation system.

Researchers are exploring how to combine the resources at AMIGO to refine treatments. Imaging during surgery can address the problem of overtreating early-stage tumours, such as those found during routine lung CT scans on smokers. Small lumps are difficult to locate so surgeons may end up removing large pieces of lung tissue that will never grow back, says Raphael Bueno, a thoracic surgeon at Brigham and Women's Hospital. As part of an ongoing clinical trial, Bueno has devised a method to use a CT scan to guide the placement of a small hook-like device in the lesion. The hook is attached to surgical thread that reaches out of the lung. During surgery the thread acts as a guide, allowing Bueno to snip out only the affected tissue.

 

 

Kapur T, Tempany CM, Jolesz FA. Proceedings of the 6th Image Guided Therapy Workshop. 2013;6 :1-87. 2013 IGT Workshop Proceedings
Shriver S, Knierim KE, O'Shea JP, Glover GH, Golby AJ. Pneumatically driven finger movement: a novel passive functional MR imaging technique for presurgical motor and sensory mapping. AJNR Am J Neuroradiol. 2013;34 (1) :E5-7.Abstract
Two of the most common reasons for failure to obtain adequate preoperative functional data are inadequate task performance and excessive head motion. With an MR imaging-compatible pneumatically driven manipulandum, passive motor tasks elicited reproducible contralateral activation in the M1 and S1 in 10 healthy controls and 6 patients. The SMA was localized in all healthy controls and in 5 of 6 patients. Head motion was reduced in passive tasks compared with active tasks.
Kolesov I, Lee J, Vela P, Tannenbaum A. Stochastic Image Registration with User Constraints. Proc SPIE Int Soc Opt Eng. 2013;8669.Abstract
Constrained registration is an active area of research and is the focus of this work. This note describes a non-rigid image registration framework for incorporating landmark constraints. Points that must remain stationary are selected, the user chooses the spatial extent of the inputs, and an automatic step computes the deformable registration, respecting the constraints. Parametrization of the deformation field is by an additive composition of a similarity transformation and a set of Gaussian radial basis functions. The bases' centers, variances, and weights are determined with a global optimization approach that is introduced. This approach is based on the particle filter for performing constrained optimization; it explores a series of states defining a deformation field that is physically meaningful (i.e., invertible) and prevents chosen points from moving. Results on synthetic two dimensional images are presented.
Seifabadi R, Cho NBJ, Song S-E, Tokuda J, Hata N, Tempany CM, Fichtinger G, Iordachita I. Accuracy Study of a Robotic System for MRI-guided Prostate Needle Placement. Int J Med Robot. 2013;9 (3) :305-16.Abstract

BACKGROUND: Accurate needle placement is the first concern in percutaneous MRI-guided prostate interventions. In this phantom study, different sources contributing to the overall needle placement error of a MRI-guided robot for prostate biopsy have been identified, quantified and minimized to the possible extent. METHODS: The overall needle placement error of the system was evaluated in a prostate phantom. This error was broken into two parts: the error associated with the robotic system (called 'before-insertion error') and the error associated with needle-tissue interaction (called 'due-to-insertion error'). Before-insertion error was measured directly in a soft phantom and different sources contributing into this part were identified and quantified. A calibration methodology was developed to minimize the 4-DOF manipulator's error. The due-to-insertion error was indirectly approximated by comparing the overall error and the before-insertion error. The effect of sterilization on the manipulator's accuracy and repeatability was also studied. RESULTS: The average overall system error in the phantom study was 2.5 mm (STD = 1.1 mm). The average robotic system error in the Super Soft plastic phantom was 1.3 mm (STD = 0.7 mm). Assuming orthogonal error components, the needle-tissue interaction error was found to be approximately 2.13 mm, thus making a larger contribution to the overall error. The average susceptibility artifact shift was 0.2 mm. The manipulator's targeting accuracy was 0.71 mm (STD = 0.21 mm) after robot calibration. The robot's repeatability was 0.13 mm. Sterilization had no noticeable influence on the robot's accuracy and repeatability. CONCLUSIONS: The experimental methodology presented in this paper may help researchers to identify, quantify and minimize different sources contributing into the overall needle placement error of an MRI-guided robotic system for prostate needle placement. In the robotic system analysed here, the overall error of the studied system remained within the acceptable range.

Eberlin LS, Norton I, Orringer D, Dunn IF, Liu X, Ide JL, Jarmusch AK, Ligon KL, Jolesz FA, Golby AJ, et al. Ambient Mass Spectrometry for the Intraoperative Molecular Diagnosis of Human Brain Tumors. Proc Natl Acad Sci U S A. 2013;110 (5) :1611-6.Abstract

The main goal of brain tumor surgery is to maximize tumor resection while preserving brain function. However, existing imaging and surgical techniques do not offer the molecular information needed to delineate tumor boundaries. We have developed a system to rapidly analyze and classify brain tumors based on lipid information acquired by desorption electrospray ionization mass spectrometry (DESI-MS). In this study, a classifier was built to discriminate gliomas and meningiomas based on 36 glioma and 19 meningioma samples. The classifier was tested and results were validated for intraoperative use by analyzing and diagnosing tissue sections from 32 surgical specimens obtained from five research subjects who underwent brain tumor resection. The samples analyzed included oligodendroglioma, astrocytoma, and meningioma tumors of different histological grades and tumor cell concentrations. The molecular diagnosis derived from mass-spectrometry imaging corresponded to histopathology diagnosis with very few exceptions. Our work demonstrates that DESI-MS technology has the potential to identify the histology type of brain tumors. It provides information on glioma grade and, most importantly, may help define tumor margins by measuring the tumor cell concentration in a specimen. Results for stereotactically registered samples were correlated to preoperative MRI through neuronavigation, and visualized over segmented 3D MRI tumor volume reconstruction. Our findings demonstrate the potential of ambient mass spectrometry to guide brain tumor surgery by providing rapid diagnosis, and tumor margin assessment in near-real time.

Galsky MD, Xie W, Nakabayashi M, Ross RW, Fennessy FM, Tempany CM, Choueiri TK, Khine K, Kantoff PW, Taplin M-E, et al. Analysis of the Correlation between Endorectal MRI Response to Neoadjuvant Chemotherapy and Biochemical Recurrence in Patients with High-Risk Localized Prostate Cancer. Prostate Cancer Prostatic Dis. 2013;16 (3) :266-70.Abstract

BACKGROUND: Intermediate end points are desirable to expedite the integration of neoadjuvant systemic therapy into the treatment strategy for high-risk localized prostate cancer. Endorectal magnetic resonance imaging at 1.5 Tesla (1.5T erMRI) response has been utilized as an end point in neoadjuvant trials but has not been correlated with clinical outcomes. METHODS: Data were pooled from two trials exploring neoadjuvant chemotherapy in high-risk localized prostate cancer. Trial 1 explored docetaxel for 6 months and Trial 2 explored docetaxel plus bevacizumab for 4.5 months, both before radical prostatectomy. erMRI was done at baseline and end of chemotherapy. 1.5T erMRI response, based upon T2W sequences, was recorded. Multivariable Cox regression was undertaken to evaluate the association between clinical parameters and biochemical recurrence. RESULTS: There were 53 evaluable patients in the combined analysis: 20 (33%) achieved a PSA response, 16 (27%) achieved an erMRI partial response and 24 (40%) achieved an erMRI minor response. Median follow-up was 4.2 years, and 33 of 53 evaluable (62%) patients developed biochemical recurrence. On multivariable analysis, PSA response did not correlate with biochemical recurrence (hazard ratio=0.58, 95% confidence interval (CI) 0.25-1.33) and paradoxically erMRI response was associated with a significantly shorter time to biochemical recurrence (hazard ratio=2.47, 95% CI 1.00-6.13). CONCLUSIONS: Response by 1.5T erMRI does not correlate with a decreased likelihood of biochemical recurrence in patients with high-risk localized prostate cancer treated with neoadjuvant docetaxel and may be associated with inferior outcomes. These data do not support the use of 1.5T erMRI response as a primary end point in neoadjuvant chemotherapy trials.

Risholm P, Janoos F, Norton I, Golby AJ, Wells III WM. Bayesian Characterization of Uncertainty in Intra-subject Non-rigid Registration. Med Image Anal. 2013;17 (5) :538-55.Abstract

In settings where high-level inferences are made based on registered image data, the registration uncertainty can contain important information. In this article, we propose a Bayesian non-rigid registration framework where conventional dissimilarity and regularization energies can be included in the likelihood and the prior distribution on deformations respectively through the use of Boltzmann's distribution. The posterior distribution is characterized using Markov Chain Monte Carlo (MCMC) methods with the effect of the Boltzmann temperature hyper-parameters marginalized under broad uninformative hyper-prior distributions. The MCMC chain permits estimation of the most likely deformation as well as the associated uncertainty. On synthetic examples, we demonstrate the ability of the method to identify the maximum a posteriori estimate and the associated posterior uncertainty, and demonstrate that the posterior distribution can be non-Gaussian. Additionally, results from registering clinical data acquired during neurosurgery for resection of brain tumor are provided; we compare the method to single transformation results from a deterministic optimizer and introduce methods that summarize the high-dimensional uncertainty. At the site of resection, the registration uncertainty increases and the marginal distribution on deformations is shown to be multi-modal.

Mostayed A, Garlapati RR, Joldes GR, Wittek A, Roy A, Kikinis R, Warfield SK, Miller K. Biomechanical Model as a Registration Tool for Image-guided Neurosurgery: Evaluation Against BSpline Registration. Ann Biomed Eng. 2013;41 (11) :2409-25.Abstract

In this paper we evaluate the accuracy of warping of neuro-images using brain deformation predicted by means of a patient-specific biomechanical model against registration using a BSpline-based free form deformation algorithm. Unlike the BSpline algorithm, biomechanics-based registration does not require an intra-operative MR image which is very expensive and cumbersome to acquire. Only sparse intra-operative data on the brain surface is sufficient to compute deformation for the whole brain. In this contribution the deformation fields obtained from both methods are qualitatively compared and overlaps of Canny edges extracted from the images are examined. We define an edge based Hausdorff distance metric to quantitatively evaluate the accuracy of registration for these two algorithms. The qualitative and quantitative evaluations indicate that our biomechanics-based registration algorithm, despite using much less input data, has at least as high registration accuracy as that of the BSpline algorithm.

Arvanitis CD, Livingstone MS, McDannold N. Combined Ultrasound and MR Imaging to Guide Focused Ultrasound Therapies in the Brain. Phys Med Biol. 2013;58 (14) :4749-61.Abstract

Several emerging therapies with potential for use in the brain, harness effects produced by acoustic cavitation--the interaction between ultrasound and microbubbles either generated during sonication or introduced into the vasculature. Systems developed for transcranial MRI-guided focused ultrasound (MRgFUS) thermal ablation can enable their clinical translation, but methods for real-time monitoring and control are currently lacking. Acoustic emissions produced during sonication can provide information about the location, strength and type of the microbubble oscillations within the ultrasound field, and they can be mapped in real-time using passive imaging approaches. Here, we tested whether such mapping can be achieved transcranially within a clinical brain MRgFUS system. We integrated an ultrasound imaging array into the hemisphere transducer of the MRgFUS device. Passive cavitation maps were obtained during sonications combined with a circulating microbubble agent at 20 targets in the cingulate cortex in three macaques. The maps were compared with MRI-evident tissue effects. The system successfully mapped microbubble activity during both stable and inertial cavitation, which was correlated with MRI-evident transient blood-brain barrier disruption and vascular damage, respectively. The location of this activity was coincident with the resulting tissue changes within the expected resolution limits of the system. While preliminary, these data clearly demonstrate, for the first time, that it is possible to construct maps of stable and inertial cavitation transcranially, in a large animal model, and under clinically relevant conditions. Further, these results suggest that this hybrid ultrasound/MRI approach can provide comprehensive guidance for targeted drug delivery via blood-brain barrier disruption and other emerging ultrasound treatments, facilitating their clinical translation. We anticipate that it will also prove to be an important research tool that will further the development of a broad range of microbubble-enhanced therapies.

Córdova H, San José Estépar R, Rodríguez-D'Jesús A, Martínez-Pallí G, Arguis P, Rodríguez de Miguel C, Navarro-Ripoll R, Perdomo JM, Cuatrecasas M, Llach J, et al. Comparative Study of NOTES Alone versus NOTES Guided by a New Image Registration System for Navigation in the Mediastinum: A Study in a Porcine Model. Gastrointest Endosc. 2013;77 (1) :102-7.Abstract

BACKGROUND: Natural orifice transluminal endoscopic surgery (NOTES) mediastinoscopy (MED) through the esophagus has proved to be feasible in the animal model. However, injury of the adjacent pleura and pneumothorax has been reported as a frequent adverse event when using a blind access. OBJECTIVE: To assess the utility and safety of a CT-based image registration system (IRS) for navigation in the mediastinum. DESIGN: Prospective, randomized, controlled trial in 30 Yorkshire pigs. Thirty-minute MEDs were performed: 15 MEDs were performed with IRS guidance (MED-IRS), and 15 MEDs were performed with a blind access. SETTING: Animal research laboratory. INTERVENTIONS: In both groups, the mediastinum was accessed through a 10-cm submucosal tunnel in the esophageal wall. Timed exploration was performed with identification of 8 mediastinal structures. MAIN OUTCOME MEASUREMENTS: Technical feasibility, adverse events, and the number of mediastinal structures identified. RESULTS: Thirty animals weighing 31.5 ± 3.5 kg were included in this study. MED was not possible in 2 animals in the "MED with blind access" group but was possible in all MEDs performed with IRS. The mean number of identified organs was slightly higher in "with IRS-MED" (6.13 ± 1.3) than with MED with blind access (4.7 ± 2.3; P = .066). Moreover, the right atrium and vena cava were identified in more cases with IRS-MED than in MED with blind access (13 vs 3 and 15 vs 11, P = .000 and P = .03, respectively). There were 3 (23%) adverse events with IRS-MED and 4 (27%) with "MED with blind access" (P = not significant), with pneumothorax being the most frequent (2 and 3, respectively). LIMITATIONS: Nonsurvival animal study. CONCLUSIONS: This study demonstrates that the IRS system appears feasible in natural orifice transluminal endoscopic surgery MED and suggests that IRS guidance might be useful for selected procedures.

Tokuda J, Song S-E, Tuncali K, Tempany CM, Hata N. Configurable Automatic Detection and Registration of Fiducial Frames for Device-to-Image Registration in MRI-guided Prostate Interventions. Med Image Comput Comput Assist Interv. 2013;16 (Pt 3) :355-62.Abstract

We propose a novel automatic fiducial frame detection and registration method for device-to-image registration in MRI-guided prostate interventions. The proposed method does not require any manual selection of markers, and can be applied to a variety of fiducial frames, which consist of multiple cylindrical MR-visible markers placed in different orientations. The key idea is that automatic extraction of linear features using a line filter is more robust than that of bright spots by thresholding; by applying a line set registration algorithm to the detected markers, the frame can be registered to the MRI. The method was capable of registering the fiducial frame to the MRI with an accuracy of 1.00 +/- 0.73 mm and 1.41 +/- 1.06 degrees in a phantom study, and was sufficiently robust to detect the fiducial frame in 98% of images acquired in clinical cases despite the existence of anatomical structures in the field of view.

Huang Y, Vykhodtseva NI, Hynynen K. Creating Brain Lesions with Low-intensity Focused Ultrasound with Microbubbles: A Rat Study at Half a Megahertz. Ultrasound Med Biol. 2013;39 (8) :1420-8.Abstract

Low-intensity focused ultrasound was applied with microbubbles (Definity, Lantheus Medical Imaging, North Billerica, MA, USA; 0.02 mL/kg) to produce brain lesions in 50 rats at 558 kHz. Burst sonications (burst length: 10 ms; pulse repetition frequency: 1 Hz; total exposure: 5 min; acoustic power: 0.47-1.3 W) generated ischemic or hemorrhagic lesions at the focal volume revealed by both magnetic resonance imaging and histology. Shorter burst time (2 ms) or shorter sonication time (1 min) reduced the probability of lesion production. Longer pulses (200 ms, 500 ms and continuous wave) caused significant near-field damage. Using microbubbles with focused ultrasound significantly reduced acoustic power levels and, therefore, avoided skull heating issues and potentially can extend the treatable volume of transcranial focused ultrasound to brain tissues close to the skull.

Song S-E, Tokuda J, Tuncali K, Tempany CM, Zhang E, Hata N. Development and Preliminary Evaluation of a Motorized Needle Guide Template for MRI-guided Targeted Prostate Biopsy. IEEE Trans Biomed Eng. 2013;60 (11) :3019-27.Abstract

To overcome the problems of limited needle insertion accuracy and human error in the use of a conventional needle guide template in magnetic resonance imaging (MRI)-guided prostate intervention, we developed a motorized MRI-compatible needle guide template that resembles a transrectal ultrasound-guided prostate template. The motorized template allows automated, gapless needle guidance in a 3T MRI scanner with minimal changes in the current clinical procedure. To evaluate the impact of the motorized template on MRI, signal-to-noise ratio and distortion were measured under various system configurations. A maximum of 44% signal-to-noise ratio decrease was found when the ultrasonic motors were running, and a maximum of 0.4% image distortion was observed due to the presence of the motorized template. To measure needle insertion accuracy, we performed four sets of five random target needle insertions mimicking four biopsy procedures, which resulted in an average in-plane targeting error of 0.94 mm with a standard deviation of 0.34 mm. The evaluation studies indicated that the presence and operation of the motorized template in the MRI bore create insignificant image degradation, and provide submillimeter targeting accuracy. The automated needle guide that is directly controlled by navigation software eliminates human error so that the safety of the procedure can be improved.

Abd-El-Barr MM, Saleh E, Huang RY, Golby AJ. Effect of Disease and Recovery on Functional Anatomy in Brain Tumor Patients: Insights from Functional MRI and Diffusion Tensor Imaging. Imaging Med. 2013;5 (4) :333-46.Abstract

Patients with brain tumors provide a unique opportunity to understand functional brain plasticity. Using advanced imaging techniques, such as functional MRI and diffusion tensor imaging, we have gained tremendous knowledge of brain tumor behavior, transformation, infiltration and destruction of nearby structures. Using these advanced techniques as an adjunct with more proven techniques, such as direct cortical stimulation, intraoperative navigation and advanced microsurgical techniques, we now are able to better formulate safer resection trajectories, perform larger resections at reduced risk and better counsel patients and their families about possible complications. Brain mapping in patients with brain tumors and other lesions has shown us that the old idea of fixed function of the adult cerebral cortex is not entirely true. Improving care for patients with brain lesions in the future will depend on better understanding of the functional organization and plasticity of the adult brain. Advanced noninvasive brain imaging will undoubtedly play a role in advancing this understanding.

Lemaire J-J, Golby AJ, Wells III WM, Pujol S, Tie Y, Rigolo L, Yarmarkovich A, Pieper S, Westin C-F, Jolesz FA, et al. Extended Broca's Area in the Functional Connectome of Language in Adults: Combined Cortical and Subcortical Single-subject Analysis using fMRI and DTI Tractography. Brain Topogr. 2013;26 (3) :428-41.Abstract

Traditional models of the human language circuitry encompass three cortical areas, Broca's, Geschwind's and Wernicke's, and their connectivity through white matter fascicles. The neural connectivity deep to these cortical areas remains poorly understood, as does the macroscopic functional organization of the cortico-subcortical language circuitry. In an effort to expand current knowledge, we combined functional MRI (fMRI) and diffusion tensor imaging to explore subject-specific structural and functional macroscopic connectivity, focusing on Broca's area. Fascicles were studied using diffusion tensor imaging fiber tracking seeded from volumes placed manually within the white matter. White matter fascicles and fMRI-derived clusters (antonym-generation task) of positive and negative blood-oxygen-level-dependent (BOLD) signal were co-registered with 3-D renderings of the brain in 12 healthy subjects. Fascicles connecting BOLD-derived clusters were analyzed within specific cortical areas: Broca's, with the pars triangularis, the pars opercularis, and the pars orbitaris; Geschwind's and Wernicke's; the premotor cortex, the dorsal supplementary motor area, the middle temporal gyrus, the dorsal prefrontal cortex and the frontopolar region. We found a functional connectome divisible into three systems-anterior, superior and inferior-around the insula, more complex than previously thought, particularly with respect to a new extended Broca's area. The extended Broca's area involves two new fascicles: the operculo-premotor fascicle comprised of well-organized U-shaped fibers that connect the pars opercularis with the premotor region; and (2) the triangulo-orbitaris system comprised of intermingled U-shaped fibers that connect the pars triangularis with the pars orbitaris. The findings enhance our understanding of language function.

Toews M, Zöllei L, Wells III WM. Feature-based Alignment of Volumetric Multi-modal Images. Inf Process Med Imaging. 2013;23 :25-36.Abstract

This paper proposes a method for aligning image volumes acquired from different imaging modalities (e.g. MR, CT) based on 3D scale-invariant image features. A novel method for encoding invariant feature geometry and appearance is developed, based on the assumption of locally linear intensity relationships, providing a solution to poor repeatability of feature detection in different image modalities. The encoding method is incorporated into a probabilistic feature-based model for multi-modal image alignment. The model parameters are estimated via a group-wise alignment algorithm, that iteratively alternates between estimating a feature-based model from feature data, then realigning feature data to the model, converging to a stable alignment solution with few pre-processing or pre-alignment requirements. The resulting model can be used to align multi-modal image data with the benefits of invariant feature correspondence: globally optimal solutions, high efficiency and low memory usage. The method is tested on the difficult RIRE data set of CT, T1, T2, PD and MP-RAGE brain images of subjects exhibiting significant inter-subject variability due to pathology.

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