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Biomedical subjects

E A Hoffman

Publications and source records attributed to E A Hoffman.

At least 19 recordsLinked to original sources
PubMed2001

Three-dimensional vocal tract imaging and formant structure: varying vocal register, pitch, and loudness.

Although advances in techniques for image acquisition and analysis have facilitated the direct measurement of three-dimensional vocal tract air space shapes associated with specific speech phonemes, little information is available with regard to changes in three-dimensional (3-D) vocal tract shape as a function of vocal register, pitch, and loudness. In this study, 3-D images of the vocal tract during falsetto and chest register phonations at various pitch and loudness conditions were obtained using electron beam computed tomography (EBCT). Detailed measurements and differences in vocal tract configuration and formant characteristics derived from the eight measured vocal tract shapes are reported.

Humans↗
PubMed2000

Distinct representations of eye gaze and identity in the distributed human neural system for face perception.

Face perception requires representation of invariant aspects that underlie identity recognition as well as representation of changeable aspects, such as eye gaze and expression, that facilitate social communication. Using functional magnetic resonance imaging (fMRI), we investigated the perception of face identity and eye gaze in the human brain. Perception of face identity was mediated more by regions in the inferior occipital and fusiform gyri, and perception of eye gaze was mediated more by regions in the superior temporal sulci. Eye-gaze perception also seemed to recruit the spatial cognition system in the intraparietal sulcus to encode the direction of another's gaze and to focus attention in that direction.

Adult↗
PubMed1999

Repetitive transcranial magnetic stimulation of the dominant hemisphere can disrupt visual naming in temporal lobe epilepsy patients.

We used repetitive transcranial magnetic stimulation (rTMS) to study visual naming in 14 patients with temporal lobe epilepsy. Ten had left hemisphere language by Wada testing and all experienced speech arrest with rTMS of the motor speech area in the left frontal lobe. One left-hander had speech arrest with stimulation of sites on both sides. Subjects were asked to name pictures or read words presented on a computer monitor. rTMS was delivered on half of the trials. Stimulation sites were the motor speech area in the left frontal lobe, the mirror site on the right, and the left and right mid superior and posterior temporal lobes. rTMS at left hemisphere sites caused more naming errors than did right hemisphere rTMS. All individual subjects, except two who had temporal lobe resections and the one with bilateral speech arrest, produced more naming errors with rTMS of left hemisphere sites. There was no significant effect on word reading. rTMS at the left hemisphere and right frontal sites produced reductions in reaction time for picture naming, but not for word reading. This was observed for both correct and incorrect responses. This study shows that left hemisphere rTMS can disrupt visual naming selectively.

Adult↗
PubMed1999

The effect of face inversion on activity in human neural systems for face and object perception.

The differential effect of stimulus inversion on face and object recognition suggests that inverted faces are processed by mechanisms for the perception of other objects rather than by face perception mechanisms. We investigated the face inversion using functional magnetic resonance imaging (fMRI). The principal effect of face inversion on was an increased response in ventral extrastriate regions that respond preferentially to another class of objects (houses). In contrast, house inversion did not produce a similar change in face-selective regions. Moreover, stimulus inversion had equivalent, minimal effects for faces in in face-selective regions and for houses in house-selective regions. The results suggest that the failure of face perception systems with inverted faces leads to the recruitment of processing resources in object perception systems, but this failure is not reflected by altered activity in face perception systems.

Brain↗
PubMed1999

Pulmonary CT image classification with evolutionary programming.

RATIONALE AND OBJECTIVES: It is often difficult to classify information in medical images from derived features. The purpose of this research was to investigate the use of evolutionary programming as a tool for selecting important features and generating algorithms to classify computed tomographic (CT) images of the lung. MATERIALS AND METHODS: Training and test sets consisting of 11 features derived from multiple lung CT images were generated, along with an indicator of the target area from which features originated. The images included five parameters based on histogram analysis, 11 parameters based on run length and co-occurrence matrix measures, and the fractal dimension. Two classification experiments were performed. In the first, the classification task was to distinguish between the subtle but known differences between anterior and posterior portions of transverse lung CT sections. The second classification task was to distinguish normal lung CT images from emphysematous images. The performance of the evolutionary programming approach was compared with that of three statistical classifiers that used the same training and test sets. RESULTS: Evolutionary programming produced solutions that compared favorably with those of the statistical classifiers. In separating the anterior from the posterior lung sections, the evolutionary programming results were better than two of the three statistical approaches. The evolutionary programming approach correctly identified all the normal and abnormal lung images and accomplished this by using less features than the best statistical method. CONCLUSION: The results of this study demonstrate the utility of evolutionary programming as a tool for developing classification algorithms.

Algorithms↗
PubMed1999

Interstitial lung disease: A quantitative study using the adaptive multiple feature method.

We have previously described an adaptive multiple feature method (AMFM) for the objective assessment of global and regional changes in pulmonary parenchyma to detect emphysema. This computerized method uses a combination of statistical and fractal texture features for characterization of lung tissues based upon high resolution computed tomography (HRCT) scans. This present study was a substantial extension of the AMFM to simultaneously discriminate between multiple pulmonary disease processes. Normal subjects and those with emphysema, idiopathic pulmonary fibrosis (IPF), or sarcoidosis were studied. The AMFM was compared with two currently utilized computer-based methods: mean lung density (MLD) and the histogram analysis (HIST). Globally, when comparing two-subject groups the AMFM overall accuracy was 2 to 18% better than the overall accuracy of MLD and as much as 36% better than the accuracy of the HIST methods. In three-subject group discrimination tasks, the AMFM performed 7 to 27% better than the MLD and 4 to 36% better than the HIST methods. Finally, in discriminating all four subject groups at a time, the AMFM overall accuracy was 81%, which was 21% better than the MLD and 25% better than the HIST method. In most three-subject group comparisons and in the four-subject group comparison, the AMFM was significantly (p < 0.01) better than the MLD and HIST methods. Next, the AMFM was applied to local discrimination between normal and each disease group individually. The normal versus emphysema, normal versus IPF, and normal versus sarcoidosis samples were discriminated with an accuracy of 95, 86, and 77%, respectively. The AMFM is an objective quantitative method that can be adapted for successful discrimination of multiple parenchymal lung diseases.

Diagnosis, Computer-Assisted↗
PubMed1999

Computer recognition of regional lung disease patterns.

We have developed an objective, reproducible, and automated means for the regional evaluation of the pulmonary parenchyma from computed tomography (CT) scans. This method, known as the Adaptive Multiple Feature Method (AMFM) assesses as many as 22 independent texture features in order to classify a tissue pattern. In this study, the six tissue patterns characterized were: honeycombing, ground glass, bronchovascular, nodular, emphysemalike, and normal. The lung slices were evaluated regionally using 31 x 31 pixel regions of interest. In each region of interest, an optimal subset of texture features was evaluated to determine which of the six patterns the region could be characterized as. The computer output was validated against experienced observers in three settings. In the first two readings, when the observers were blinded to the primary diagnosis of the subject, the average computer versus observer agreement was 44.4 +/- 8.7% and 47.3 +/- 9.0%, respectively. The average interobserver agreement for the same two readings were 48.8 +/- 9.1% and 52.2 +/- 10.0%, respectively. In the third reading, when the observers were provided the primary diagnosis, the average computer versus observer agreement was 51.7 +/- 2.9% where as the average interobserver agreement was 53.9 +/- 6.2%. The kappa statistic of agreement between the regions, for which the majority of the observers agreed on a pattern type, versus the computer was found to be 0.62. For regional tissue characterization, the AMFM is 100% reproducible and performs as well as experienced human observers who have been told the patient diagnosis.

Diagnosis, Computer-Assisted↗
PubMed1998

Mechanics of the single left ventricle: a study in ventricular-ventricular interaction II.

BACKGROUND: Left ventricular (LV) effects on right ventricular (RV) function are well known. Less is understood about the effect of the RV on systemic LV mechanics. To determine this interaction, we compared systemic LVs with and without an RV mechanically coupled to them. METHODS AND RESULTS: MR myocardial tagging was used to examine 18 subjects with systemic LVs: 10 with functional single LVs (SLV) and 8 normal subjects (NL). Tracking the systolic motion of the intersecting stripes were used to determine regional twist and radial motion. Finite strain analysis was applied to derive principal strains at the atrioventricular valve (AVV) and apical short-axis levels and in 4 anatomic wall regions. Similar E1 (circumferential shortening) strain and heterogeneity of strain were noted between SLV and NL except in the septal wall. At the septal wall, NL displayed greater absolute strain (AVV=-0.16+/-0.02, apex=-0.17+/-0.02) and less heterogeneity of strain than SLV (AVV= -0.12+/-0.02, apex=-0.13+/-0.02). Similar E2 (wall thickening) strain and heterogeneity of strain were also noted between SLV and NL except again at the septal wall. At the septal wall, SLV displayed greater absolute E2 strain (AVV=0.17+/-0.08, apex=0.19+/-0.09) and less heterogeneity of strain than NL (AVV=0.07+/-0.07, apex=0.05+/-0.05). SLV twisted significantly less counterclockwise than NL in 6 of 8 wall regions and actually twisted clockwise at the AVV lateral wall. Although there was no significant difference between groups in radial wall motion, the septal and inferior walls of SLV demonstrated significantly less radial motion compared with other SLV walls. CONCLUSIONS: A major influence of the RV on systemic LV strain and radial motion occurs in the septal wall, whereas absence of the RV causes marked differences in LV twist. These findings may yield clues to the long-term functioning of the SLV and be useful in determining strategies for RV augmentation of LV function.

Adolescent↗
PubMed1998

Quantitative pulmonary imaging: spatial and temporal considerations in high-resolution CT.

RATIONALE AND OBJECTIVES: The authors performed this study to determine how scanner temporal resolution affects image quality in high-resolution computed tomography (CT)-based quantitative analysis of lung parenchyma. MATERIALS AND METHODS: A 37-kg, anesthetized white pig, in which 1.5-mm-diameter radiopaque markers were bronchoscopically implanted, was scanned supine with electron-beam CT and spiral CT scanners. Images were first acquired during apnea at functional residual capacity with electron-beam CT at a single level with multiple scan apertures. Without altering body posture, the animal was transported to the spiral CT scanner and scanned at the same lung volume and level. The animal was then euthanized and rescanned with spiral CT. All images were reconstructed with high-spatial-frequency algorithms resident on the respective scanners. RESULTS: High-resolution CT images of the live animal in the spiral scanner showed substantial cardiogenic motion artifacts for markers both near and distant from the heart. The matched postmortem images showed no motion artifacts. While line-pair phantom scans showed reduced spatial resolution of electron-beam CT compared with spiral CT scans, the electron-beam CT images of the markers in the live animal were free of artifacts, even with scan apertures of up to 700 msec. CONCLUSION: Motion artifacts may be accentuated by differences in high-resolution CT implementations. Applications such as lung parenchyma texture analysis, which regionally quantifies the subtle tissue density variations, will likely benefit from short scanning apertures.

Animals↗
PubMed1998

Segmentation of intrathoracic airway trees: a fuzzy logic approach.

Three-dimensional (3-D) analysis of airway trees extracted from computed tomography (CT) image data can provide objective information about lung structure and function. However, manual analysis of 3-D lung CT images is tedious, time consuming and, thus, impractical for routine clinical care. We have previously reported an automated rule-based method for extraction of airway trees from 3-D CT images using a priori knowledge about airway-tree anatomy. Although the method's sensitivity was quite good, its specificity suffered from a large number of falsely detected airways. We present a new approach to airway-tree detection based on fuzzy logic that increases the method's specificity without compromising its sensitivity. The method was validated in 32 CT image slices randomly selected from five volumetric canine electron-beam CT data sets. The fuzzy-logic method significantly outperformed the previously reported rule-based method (p < 0.002).

Animals↗
PubMed1998

Vocal tract area functions for an adult female speaker based on volumetric imaging.

Magnetic resonance imaging (MRI) was used to acquire vocal tract shapes of ten vowels /i, I, [symbol: see text] a, [symbol: see text], o, [symbol: see text] u/ and two liquid approximants /3[symbol: see text], 1/ for a 27-year-old adult female. These images were complemented with additional images acquired with electron beam computed tomography (CT) of /i/ and /a/. Each 3-D shape was condensed into a set of cross-sectional areas of oblique sections perpendicular to the centerline of the vocal tract's long axis, resulting in an "area function." Formant frequencies computed for each area function showed reasonable similarity to those determined from the natural (recorded) speech of the imaged subject, but differences suggest that some of the imaged vocal tract shapes were articulated differently during imaging than during recording of natural speech, and also that imaging procedures may have compromised some accuracy for a few shapes. The formant calculations also confirmed the significant effect that the piriform sinus can have on lowering the formant frequencies. A comparison is made between area functions derived using both MRI and CT methods for the vowels /i/ and /a/. Additionally, the area functions reported in this study are compared with those from two previous studies and demonstrate general similarities in shape but also obvious differences that can be attributed to anatomical differences of the imaged subjects and to differences in imaging techniques and image processing methods.

Adult↗
PubMed1998

Age-related vasodilatory response to acetazolamide challenge in healthy adults: a dynamic contrast-enhanced MR study.

PURPOSE: We examined age-related changes in baseline regional cerebral blood volume (rCBV) and response to acetazolamide stimulation by using dynamic contrast-enhanced MR imaging. METHODS: Thirty healthy volunteers ranging widely in age (23 to 82 years) were examined before and after intravenous injection of acetazolamide with dynamic susceptibility contrast-enhanced MR imaging. rCBV values were normalized for intersubject and intrasubject comparison by estimating an arterial input function directly from the imaging data. Preacetazolamide baseline rCBV and the percentage volume change index (PVCI) of the postacetazolamide to preacetazolamide state were calculated and examined as a function of age. RESULTS: Older adults (>50 years) had lower baseline rCBV per unit tissue than did younger adults (<50 years), but higher rCBV after acetazolamide stimulation. Baseline rCBV tended to decrease with age in the medial frontal and frontoparietal gray matter regions. Response to acetazolamide stimulation, measured by PVCI, showed a significant age-related increase in gray matter, approximately 0.5% per year. CONCLUSION: rCBV can be significantly increased after acetazolamide stimulation in the healthy aged. These results support the notion that age-related decreases in rCBV measured at rest reflect reduced regional metabolic requirements rather than reduced capacity for regional substrate delivery. These data serve as a normative baseline for comparison studies of rCBV vascular reserve in aging persons with various cerebrovascular disorders.

Acetazolamide↗
PubMed1997

Evaluation of in vivo total and regional air content and distribution in primate lungs with high-resolution CT.

RATIONALE AND OBJECTIVES: The authors sought to determine whether gray-scale quantitative information from high-resolution computed tomography (CT) could reliably yield estimates of lung air content and help determine changes in air content with lung inflation and deflation. MATERIALS AND METHODS: High-resolution CT images (n = 40) of lungs of two anesthetized monkeys were obtained after inflation with known air volumes. Percentage air content was calculated for each voxel, and lung volumes and patterns of air distribution were determined. RESULTS: When corrected for pressure and temperature, high-resolution CT-based volumes correlated closely with inflation volumes (r = .99; standard error = 3.4%). Patterns of regional change in air content demonstrated known patterns of ventilation. CONCLUSION: Although the high-spatial-frequency algorithm used in high-resolution CT enhances edges of structures and improves visualization of anatomic detail, gray-scale values from the same high-resolution CT data set remain a reliable index of regional lung attenuation.

Animals↗
PubMed1997

Accurate measurement of intrathoracic airways.

Airway geometry measurements can provide information regarding pulmonary physiology and pathophysiology. There has been considerable interest in measuring intrathoracic airways in two-dimensional (2-D) slices from volumetric X-ray computed tomography (CT). Such measurements can be used to evaluate and track the progression of diseases affecting the airways. A popular airway measurement method uses the "half-max" criteria, in which the gray level at the airway wall is estimated to be halfway between the minimum and maximum gray levels along a ray crossing the edge. However, because the scanning process introduces blurring, the half-max approach may not be applicable across all airway sizes. We propose a new measurement method based on a model of the scanning process. In our approach, we examine the gray-level profile of a ray crossing the airway wall and use a maximum-likelihood method to estimate the airway inner and outer radius. Using CT scans of a physical phantom, we present results showing that the new approach is more accurate than the half-max method at estimating wall location for thin-walled airways.

Bronchi↗
PubMed1997

Quantification of pulmonary emphysema from lung computed tomography images.

A texture-based adaptive multiple feature method (AMFM) for evaluating pulmonary parenchyma from computed tomography (CT) images is described. This method incorporates multiple statistical and fractal texture features. The AMFM was compared to two previously published methods, namely, mean lung density (MLD) and the lowest fifth percentile of the histogram (HIST). First, the ability of these methods to detect subtle differences in ventral-dorsal lung density gradient in the prone normal lung was studied. Second, their abilities to differentiate between normal and emphysematous whole lung slices were compared. Finally, regional analyses comparing normal and emphysematous regions were performed by dividing the lungs. In the CT slices into six equal regions, ventral to dorsal, and analyzing each region separately. The results demonstrated that the AMFM could separate the ventral from the dorsal one-third of the normal prone lung with 89.8% accuracy, compared to an accuracy of 74.6% with the MLD and 64.4% with the HIST methods. The normal and emphysematous slices were separated on a global basis with 100.0% accuracy using the AMFM as compared to an accuracy of 94.7% and 97.4% using the MLD and HIST methods, respectively. The regional normal and emphysematous tissues were discriminated with an average accuracy of 97.9%, 89.9%, and 99.1% with the AMFM, MLD, and HIST methods, respectively. The three methods and the pulmonary function tests in the normal and emphysema groups were poorly correlated. Quantitative texture analysis using adaptive multiple features holds promise for the objective noninvasive evaluation of the pulmonary parenchyma.

Humans↗
PubMed1996

Late ventricular geometry and performance changes of functional single ventricle throughout staged Fontan reconstruction assessed by magnetic resonance imaging.

OBJECTIVES: We sought to test the hypothesis that late ventricular geometry and performance changes occur in functional single ventricles as they progress through staged Fontan reconstruction. BACKGROUND: Indexes of ventricular geometry and performance are important in evaluating the functional state of the heart. Magnetic resonance imaging determines these indexes in complex ventricular shapes with minimal geometric assumptions. Previous studies have shown that 1 week after hemiFontan, the mass/volume ratio markedly increases. METHODS: Multiphase, multislice, spin echo (n = 5) and cine (n = 30) magnetic resonance imaging was performed in 35 patients with a functional single ventricle (1 week to 12 years old) at various stages of Fontan reconstruction (15 in the pre hemiFontan stage, 11 after [6 to 9 months] the hemiFontan procedure and 9 after [1 to 2 years] the Fontan procedure). Volume and mass were calculated at end-systole and end-diastole. Ventricular output was then obtained. Ventricular centroid motion was also calculated. RESULTS: No difference was noted (power > 72%) from the pre hemiFontan stage to 6 to 9 months after the hemiFontan procedure in (mean +/- SD) end-diastolic volume (104 +/- 24 vs. 123 +/- 40 cc/m2), mass (171 +/- 46 vs. 202 +/- 61 g/m2), ventricular output (7.9 +/- 2.2 vs. 6.6 +/- 2.4 liters/min per m2) or centroid motion (6.9 +/- 2.8 vs. 6.7 +/- 2. mm/m2). Patients in the Fontan group demonstrated a marked decrease in all indexes, indicating significant volume unloading and decrease in mass and ventricular performance. Mass/volume ratio was not significantly different among all three groups. CONCLUSIONS: No geometric and performance changes from the volume-loaded stage are noted 6 to 9 months after the hemiFontan procedure; however, major changes occur 1 to 2 years after the Fontan procedure. The dramatic changes in the mass/volume ratio seen early after the hemiFontan procedure were not detected at 6 to 9 months. Furthermore diminution of mass, volume and ventricular performance are present at least 2 years after the Fontan procedure.

Case-Control Studies↗