Selective image similarity measure for bronchoscope tracking based on image registration.

We propose a selective method of measurement for computing image similarities based on characteristic structure extraction and demonstrate its application to flexible endoscope navigation, in particular to a bronchoscope navigation system. Camera motion tracking is a fundamental function required for image-guided treatment or therapy systems. In recent years, an ultra-tiny electromagnetic sensor commercially became available, and many image-guided treatment or therapy systems use this sensor for tracking the camera position and orientation.

Comprehensive maps of Drosophila higher olfactory centers: spatially segregated fruit and pheromone representation.

In Drosophila, approximately 50 classes of olfactory receptor neurons (ORNs) send axons to 50 corresponding glomeruli in the antennal lobe. Uniglomerular projection neurons (PNs) relay olfactory information to the mushroom body (MB) and lateral horn (LH). Here, we combine single-cell labeling and image registration to create high-resolution, quantitative maps of the MB and LH for 35 input PN channels and several groups of LH neurons.

Bronchoscope tracking based on image registration using multiple initial starting points estimated by motion prediction.

This paper presents a method for tracking a bronchoscope based on motion prediction and image registration from multiple initial starting points as a function of a bronchoscope navigation system. We try to improve performance of bronchoscope tracking based on image registration using multiple initial guesses estimated using motion prediction. This method basically tracks a bronchoscopic camera by image registration between real bronchoscopic images and virtual ones derived from CT images taken prior to the bronchoscopic examinations.

A study of the accuracy of cyberknife spinal radiosurgery using skeletal structure tracking.

Objective: New technology has enabled the increasing use of radiosurgery to ablate spinal lesions. The first generation of the CyberKnife (Accuray, Inc., Sunnyvale, CA) image-guided radiosurgery system required implanted radiopaque markers (fiducials) to localize spinal targets.

Shape-based averaging.

A new method for averaging multidimensional images is presented, which is based on signed Euclidean distance maps computed for each of the pixel values. We refer to the algorithm as "shape-based averaging" (SBA) because of its similarity to Raya and Udupa's shape-based interpolation method. The new method does not introduce pixel intensities that were not present in the input data, which makes it suitable for averaging nonnumerical data such as label maps (segmentations).

A method for bronchoscope tracking by combining a position sensor and image registration.

This paper describes a method for tracking a bronchoscope by combining a position sensor and image registration. A bronchoscopy guidance system is a tool for providing real-time navigation information acquired from pre-operative CT images to a physician during a bronchoscopic examination. In this system, one of the fundamental functions is tracking a bronchoscope's camera motion.

Virtual 3D planning and guidance of mandibular distraction osteogenesis.

We present a system for 3D planning and pre-operative rehearsal of mandibular distraction osteogenesis procedures. Two primary architectural components are described: a planning system that allows geometric bone manipulation to rapidly explore various modifications and configurations, and a visuohaptic simulator that allows both general-purpose training and preoperative, patient-specific procedure rehearsal. We provide relevant clinical background, then describe the underlying simulation algorithms and their application to craniofacial procedures.

Hybrid bronchoscope tracking using a magnetic tracking sensor and image registration.

In this paper, we propose a hybrid method for tracking a bronchoscope that uses a combination of magnetic sensor tracking and image registration. The position of a magnetic sensor placed in the working channel of the bronchoscope is provided by a magnetic tracking system. Because of respiratory motion, the magnetic sensor provides only the approximate position and orientation of the bronchoscope in the coordinate system of a CT image acquired before the examination.

Markerless real-time 3-D target region tracking by motion backprojection from projection images.

Accurate and fast localization of a predefined target region inside the patient is an important component of many image-guided therapy procedures. This problem is commonly solved by registration of intraoperative 2-D projection images to 3-D preoperative images. If the patient is not fixed during the intervention, the 2-D image acquisition is repeated several times during the procedure, and the registration problem can be cast instead as a 3-D tracking problem.

Fast generation of digitally reconstructed radiographs using attenuation fields with application to 2D-3D image registration.

Generation of digitally reconstructed radiographs (DRRs) is computationally expensive and is typically the rate-limiting step in the execution time of intensity-based two-dimensional to three-dimensional (2D-3D) registration algorithms. We address this computational issue by extending the technique of light field rendering from the computer graphics community. The extension of light fields, which we call attenuation fields (AFs), allows most of the DRR computation to be performed in a preprocessing step; after this precomputation step, DRRs can be generated substantially faster than with conventional ray casting.

Progressive attenuation fields: fast 2D-3D image registration without precomputation.

Computation of digitally reconstructed radiograph (DRR) images is the rate-limiting step in most current intensity-based algorithms for the registration of three-dimensional (3D) images to two-dimensional (2D) projection images. This paper introduces and evaluates the progressive attenuation field (PAF), which is a new method to speed up DRR computation. A PAF is closely related to an attenuation field (AF).

Unwarping confocal microscopy images of bee brains by nonrigid registration to a magnetic resonance microscopy image.

Confocal microscopy (CM) is a powerful image acquisition technique that is well established in many biological applications. It provides 3-D acquisition with high spatial resolution and can acquire several different channels of complementary image information. Due to the specimen extraction and preparation process, however, the shapes of imaged objects may differ considerably from their in vivo appearance.

Intensity-based 2D-3D spine image registration incorporating a single fiducial marker.

Rationale And Objectives: The two-dimensional (2D)-three dimensional (3D) registration of a computed tomography image to one or more x-ray projection images has a number of image-guided therapy applications. In general, fiducial marker-based methods are fast, accurate, and robust, but marker implantation is not always possible, often is considered too invasive to be clinically acceptable, and entails risk. There also is the unresolved issue of whether it is acceptable to leave markers permanently implanted.

The impact of fiducial distribution on headset-based registration in image-guided sinus surgery.

Objective: The objective of this study was to assess registration error due to fiducial configuration for the ENT headsets for the CBYON Suite (CBYON, Mountain View, CA) and InstaTrak (GEMS Navigation and Visualization, Waukesha, WI).

Study Design: Axial CT scans (1-mm slice thickness) were obtained of for 24 cadaveric heads using the CBYON headset and for 23 cadaveric heads using the GEMS headset. The CBYON and GEMS NAV software were used to calculate the fiducial registration error (FRE).

Expectation maximization strategies for multi-atlas multi-label segmentation.

It is well-known in the pattern recognition community that the accuracy of classifications obtained by combining decisions made by independent classifiers can be substantially higher that the accuracy of the individual classifiers. In order to combine multiple segmentations we introduce two extensions to an expectation maximization (EM) algorithm for ground truth estimation based on multiple experts (Warfield et al., MICCAI 2002).

Performance-based classifier combination in atlas-based image segmentation using expectation-maximization parameter estimation.

It is well known in the pattern recognition community that the accuracy of classifications obtained by combining decisions made by independent classifiers can be substantially higher than the accuracy of the individual classifiers. We have previously shown this to be true for atlas-based segmentation of biomedical images. The conventional method for combining individual classifiers weights each classifier equally (vote or sum rule fusion).

Quantitative computer-aided computed tomography analysis of sphenoid sinus anatomical relationships.

Background: This study describes a novel computer-generated anatomic symmetry plane as a framework for the quantitative description of sphenoid sinus anatomy. The aim of this study was to (1) determine relationships and distances between a midline sphenoid reference point (called the central sphenoid point [CSP]) and lateral sphenoid wall structures and (2) assess the incidence of anterior clinoid process (ACP) pneumatization and pterygoid recess (PR) pneumatization.

Methods: Axial computed tomography (CT) scans (1-mm slice thickness) were obtained on a VolumeZoom CT scanner (Siemens Medical, Erlangen, Germany).

Designing optically tracked instruments for image-guided surgery.

Most image-guided surgery (IGS) systems track the positions of surgical instruments in the physical space occupied by the patient. This task is commonly performed using an optical tracking system that determines the positions of fiducial markers such as infrared-emitting diodes or retroreflective spheres that are attached to the instrument. Instrument tracking error is an important component of the overall IGS system error.

Modeling liver motion and deformation during the respiratory cycle using intensity-based nonrigid registration of gated MR images.

We present a technique for modeling liver motion during the respiratory cycle using intensity-based nonrigid registration of gated magnetic resonance (MR) images. Three-dimensional MR images of the abdomens of four volunteers were acquired at end-inspiration, end-expiration, and eight time points in between using respiratory gating. The deformation fields between the images were computed using intensity-based rigid and nonrigid registration algorithms.

Evaluation of atlas selection strategies for atlas-based image segmentation with application to confocal microscopy images of bee brains.

This paper evaluates strategies for atlas selection in atlas-based segmentation of three-dimensional biomedical images. Segmentation by intensity-based nonrigid registration to atlas images is applied to confocal microscopy images acquired from the brains of 20 bees. This paper evaluates and compares four different approaches for atlas image selection: registration to an individual atlas image (IND), registration to an average-shape atlas image (AVG), registration to the most similar image from a database of individual atlas images (SIM), and registration to all images from a database of individual atlas images with subsequent multi-classifier decision fusion (MUL).

Volume-preserving nonrigid registration of MR breast images using free-form deformation with an incompressibility constraint.

In this paper, we extend a previously reported intensity-based nonrigid registration algorithm by using a novel regularization term to constrain the deformation. Global motion is modeled by a rigid transformation while local motion is described by a free-form deformation based on B-splines. An information theoretic measure, normalized mutual information, is used as an intensity-based image similarity measure.

Nonrigid image registration in shared-memory multiprocessor environments with application to brains, breasts, and bees.

One major problem with nonrigid image registration techniques is their high computational cost. Because of this, these methods have found limited application to clinical situations where fast execution is required, e.g.

Effect of changing patient position from supine to prone on the accuracy of a Brown-Roberts-Wells stereotactic head frame system.

Objective: Despite the growing popularity of frameless image-guided surgery systems, stereotactic frame systems are widely accepted by neurosurgeons and are commonly used to perform biopsies, functional procedures, and stereotactic radiosurgery. We investigated the accuracy of the Brown-Roberts-Wells stereotactic frame system when the mechanical load on the frame changes between preoperative imaging and the intervention because of different patient position: supine during imaging, prone during intervention.

Methods: We analyzed computed tomographic images acquired from 14 patients who underwent stereotactic biopsy, deep brain stimulator implantation, or radiosurgery.

Implementation, calibration and accuracy testing of an image-enhanced endoscopy system.

This paper presents a new method for image-guided surgery called image-enhanced endoscopy. Registered real and virtual endoscopic images (perspective volume renderings generated from the same view as the endoscope camera using a preoperative image) are displayed simultaneously; when combined with the ability to vary tissue transparency in the virtual images, this provides surgeons with the ability to see beyond visible surfaces and, thus, provides additional exposure during surgery. A mount with four photoreflective spheres is rigidly attached to the endoscope and its position and orientation is tracked using an optical position sensor.