John W. Haller

Three-dimensional computed tomography landmark measurement in craniofacial surgical planning: Experimental validation in vitro

PURPOSE This study evaluated the measurement accuracy of three-dimensional (3D) volumetric images from spiral computed tomography (CT) in vitro. MATERIALS AND METHODS The study sample consisted of nine cadaver heads that were submitted to an impact force by a special device to promote blunt traumatic craniofacial fractures. The heads were subsequently scanned by a spiral CT scanner (Toshiba Xpress S/X). The archived CT data were transferred to networked computer workstations (Sun Microsystems with Cemax VIP version 1.4 software) to generate 3D volumetric images. The visualization software was used to make interactive linear measurements on the 3D images. Measurements were made on the images twice by two observers, based on conventional craniofacial anatomic landmarks. The soft tissues were subsequently removed, and the same measurements were repeated on the cadaver heads with an electromagnetic digitizer (3 Space, Polhemus, Colchester, VT). RESULTS The results showed no statistically significant differences between the 3D-CT and the physical measurements, with P>.05 for all measurements. The mean difference between the image and real measurements was less than 2 mm in all instances. CONCLUSIONS It is concluded that measurement of the skull and facial bone landmarks by 3D reconstruction is quantitatively accurate for surgical planning and treatment evaluation of craniofacial fractures.

Visual attention in obsessive-compulsive disorder

Performance on neuropsychological tasks was compared in 15 subjects with obsessive-compulsive disorder (OCD) and 15 age- and sex-matched psychiatrically screened control subjects. The tasks chosen are known from studies in other patient groups to demonstrate lateralized abnormalities of visual and limited capacity attentional impairment. The Posner task performance of the OCD group demonstrated decreased inhibition of return for left visual field targets and no inhibition of return for right visual field targets. The OCD groups spatial-linguistic conflict task responses were significantly slowed in the conflict condition, as predicted. The results are discussed in relation to the phenomenology of OCD and prior neuropsychological evaluations.

Lateralized attentional abnormality in schizophrenia is correlated with severity of symptoms.

Numerous studies have demonstrated a lateralized impairment of attention in schizophrenia. In this study, attention in schizophrenia is investigated with a task that involves centering a rod while blindfolded. Symptoms were rated on the Brief Psychiatric Rating Scale (BPRS) for each of the 20 schizophrenic subjects. The more symptomatic patients demonstrated a right-sided hemineglect compared to the less symptomatic patients (p = 0.013). Furthermore, the difference between more and less symptomatic patients was even more distinct when they were categorized by the BPRS schizophrenia subscale alone (p = 0.0025). These findings support the hypothesis that the pathophysiology of schizophrenia involves a lateralized defect in the control of attention, and that this defect is associated with the severity of symptoms. This raises the possibility that effects of neuroleptic medication may be asymmetric, which could account for some of the inconsistencies in studies of hemispheric dysfunction in schizophrenia.

Navigation in diagnosis and therapy

Image-guided navigation for surgery and other therapeutic interventions has grown in importance in recent years. During image-guided navigation a target is detected, localized and characterized for diagnosis and therapy. Thus, images are used to select, plan, guide and evaluate therapy, thereby reducing invasiveness and improving outcomes. A shift from traditional open surgery to less-invasive image-guided surgery will continue to impact the surgical marketplace. Increases in the speed and capacity of computers and computer networks have enabled image-guided interventions. Key elements in image navigation systems are pre-operative 3D imaging (or real-time image acquisition), a graphical display and interactive input devices, such as surgical instruments with light emitting diodes (LEDs). CT and MRI, 3D imaging devices, are commonplace today and 3D images are useful in complex interventions such as radiation oncology and surgery. For example, integrated surgical imaging workstations can be used for frameless stereotaxy during neurosurgical interventions. In addition, imaging systems are being expanded to include decision aids in diagnosis and treatment. Electronic atlases, such as Voxel Man or others derived from the Visible Human Project, combine a set of image data with non-image knowledge such as anatomic labels. Robot assistants and magnetic guidance technology are being developed for minimally invasive surgery and other therapeutic interventions. Major progress is expected at the interface between the disciplines of radiology and surgery where imaging, intervention and informatics converge.

Real-time multiple linear regression for fMRI supported by time-aware acquisition and processing

Real‐time parametric statistical analysis of functional MRI (fMRI) data would potentially enlarge the scope of experimentation and facilitate its application to clinical populations. A system is described that addresses the need for rapid analysis of fMRI data and lays the foundation for dealing with problems that impede the application of fMRI to clinical populations. The system, I/OWA (Input/Output time‐aWare Architecture), combines a general architecture for sampling and time‐stamping relevant information channels in fMRI (image acquisition, stimulation, subject responses, cardiac and respiratory monitors, etc.) and an efficient approach to manipulating these data, featuring incremental subsecond multiple linear regression. The advantages of the system are the simplification of event timing and efficient and unified data formatting. Substantial parametric analysis can be performed and displayed in real‐time. Immediate (replay) and delayed off‐line analysis can also be performed with the same interface. The capabilities of the system are demonstrated in normal subjects using a polar visual angle phase mapping paradigm. The system provides a time‐accounting infrastructure that readily supports standard and innovative approaches to fMRI. Magn Reson Med 45:289–298, 2001.

Gaussian Random Fields on Sub-Manifolds for Characterizing Brain Surfaces

This paper provides analytical methods for characterizing the variation of the shape of neuro-anatomically significant substructures of the brain in an ensemble of brain images. The focus of this paper is on the neuro-anatomical variation of the “shape” of 2-dimensional surfaces in the brain. Brain surfaces are studied by building templates that are smooth sub-manifolds of the underlying coordinate system of the brain. Variation of the shape in populations is quantified via defining Gaussian random vector fields on these sub-manifolds. Methods for the empirical construction of Gaussian random vector fields for representing the variations of the substructures are presented. As an example, using these methods we characterize the shape of the hippocampus in a population of normal controls and schizophrenic brains. Results from a recently completed study comparing shapes of the hippocampus in a group of matched schizophrenic and normal control subjects are presented. Bayesian hypothesis test is formulated to cluster the normal and schizophrenic hippocampi in the population of 20 individuals.

A quantitative correlation of extravascular lung water accumulation with vascular permeability and hydrostatic pressure measurements: a positron emission tomography study

Abstract In 11 supine dogs, we related regional lung water concentration (rLWC) measurements made with positron emission tomography (PET) after canine oleic acid (OA)-induced acute lung injury to extravascular lung water measurements by the thermal-green dye indicator dilution technique (EVLW-TGD), and to measurements of vascular permeability (also by PET) and hydrostatic pressure. The rLWC measurements correlated well with EVLW-TGD (R 2 = 97%). Changes in LWC did not correlate with either the pulmonary wedge pressure or PET measurements of protein leak (as an index of vascular permeability), but were related when both variables were considered together (R 2 = 73%). Lung water concentration increased significantly 60 minutes after OA, primarily in dorsal, gravity-dependent lung regions, with a small, but statistically significant, change over the next 75 minutes. These data suggest that PET measurements of LWC or EVLW on one tomography slice can be representative of changes in EVLW in the lung as a whole after diffuse lung injury. Furthermore, the magnitude of edema accumulation after acute lung injury can be accurately predicted by quantitative measurements of hydrostatic pressure and of protein leak using PET.

Synthesizing average 3D anatomical shapes using deformable templates

A major task in diagnostic medicine is to determine whether or not an individual has a normal or abnormal anatomy by examining medical images such as MRI, CT, etc. Unfortunately, there are few quantitative measures that a physician can use to discriminate between normal and abnormal besides a couple of length, width, height, and volume measurements. In fact, there is no definition/picture of what normal anatomical structures--such as the brain-- look like let alone normal anatomical variation. The goal of this work is to synthesize average 3D anatomical shapes using deformable templates. We present a method for empirically estimating the average shape and variation of a set of 3D medical image data sets collected from a homogeneous population of topologically similar anatomies. Results are shown for synthesizing the average brain image volume from a set of six normal adults and synthesizing the average skull/head image volume from a set of five 3 - 4 month old infants with sagittal synostosis.

Colon unraveling based on electrical field: recent progress and further work

CT colonography (CTC) is a new technology, which permits endoscopic-like evaluation of the mucosal surface. Recently, an electrical field based approach was developed to unravel the colon in spiral CT image volumes, that is to digitally straighten then flatten the colon using curved cross-sections. In this paper, we report (1) an exact and computation- intensive algorithm for straightening the colon using curved cross-sections, and (2) an approximate but computationally efficient straightening algorithm. In the direct straightening algorithm, each curved cross-section of the colon is defined by electrical force lines due to charges distributed along the colon path, and constructed by directly tracing the force lines. In the fast straightening algorithm, only representative force lines are traced that originate equiangularly from the current colon path position, while other force lines are interpolated from the traced force lines. The experiments are performed with both phantom and patient data. It is demonstrated that straightening the colon with curved cross-sections facilitates visualization and analysis, has potential for use in CTC; and the speed of the interpolation based straightening algorithm is practically acceptable, which is about 40 times faster than that of the direct algorithm.

Effects of body position on regional pulmonary blood flow during acute pulmonary edema in dogs: A positron emission tomography study☆

Abstract The effect of body position on regional pulmonary blood flow (rPBF) and lung water concentration (rLWC) was studied before and after canine oleic acid (OA)-induced acute lung injury. Regional measurements were made with positron emission tomography. Eleven supine and five prone dogs were studied. In supine animals, LWC increased significantly 60 minutes after OA, primarily in gravity-dependent dorsal lung regions, with a small but still significant additional change over the next 75 minutes. Despite some redistribution, a disproportionate amount of blood flow continued to go to regions with the greatest lung water accumulation. In the prone group, LWC and rPBF were more evenly distributed than in the supine animals, both before and after lung injury. Furthermore, in the prone position, and in contrast to the supine position, regions with the greatest LWC had the least fractional flow. Thus, the benefits of the prone position on oxygenation are related to both the spatial distribution of lung water accumulation and regional pulmonary blood flow.