John W. Peifer

Technical aspects of myocardial spect imaging with technetium-99m sestamibi

Most reports to date using single photon emission computed tomography (SPECT) with technetium-99m (Tc-99m) sestamibi have used acquisition parameters that were optimized for thallium-201. To fully utilize the superior imaging characteristics of Tc-99m sestamibi, there is a need to optimize the technical aspects of SPECT imaging for this agent. Performance can be enhanced through the careful selection of optimal radiopharmaceutical doses, imaging sequences, acquisition parameters, reconstruction filters, perfusion quantification methods and multidimensional methods for visualizing perfusion distribution. The current report describes theoretical considerations, phantom studies and preliminary patient results that have led to optimized protocols, developed at Emory University and Cedars-Sinai Medical Center, for same-day rest-stress studies, given existing instrumentation and recommended dose limits. The optimizations were designed to fit a low-dose-high-dose rest-stress same-day imaging protocol. A principal change in the acquisition parameters compared with previous Tc-99m sestamibi protocols is the use of a high-resolution collimator. The approach is being developed in both prone and supine positions. A new method for extracting a 3-dimensional myocardial count distribution has been developed that uses spherical coordinates to sample the apical region and cylindrical coordinates to sample the rest of the myocardium. New methods for visualizing the myocardial distribution in multiple dimensions are also described, with improved 2-dimensional, as well as 3- and 4-dimensional (3 dimensions plus time) displays. In the improved 2-dimensional display, distance-weighted and volume-weighted polar maps are used that appear to significantly improve the representation of defect location and defect extent, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Critical Analysis of the Impact of Glottal Features in the Classification of Clinical Depression in Speech

The motivation for this work is in an attempt to rectify the current lack of objective tools for clinical analysis of emotional disorders. This study involves the examination of a large breadth of objectively measurable features for use in discriminating depressed speech. Analysis is based on features related to prosodics, the vocal tract, and parameters extracted directly from the glottal waveform. Discrimination of the depressed speech was based on a feature selection strategy utilizing the following combinations of feature domains: prosodic measures alone, prosodic and vocal tract measures, prosodic and glottal measures, and all three domains. The combination of glottal and prosodic features produced better discrimination overall than the combination of prosodic and vocal tract features. Analysis of discriminating feature sets used in the study reflect a clear indication that glottal descriptors are vital components of vocal affect analysis.

Computer-simulated eye surgery : a novel teaching method for residents and practitioners

PURPOSE To describe an eye surgery simulator that uses a computerized graphic display to allow ophthalmic surgeons of all experience levels to enhance their surgical skills. METHODS The eye surgery simulation environment consists of a high-speed computer graphics workstation, a stereo operating system, a wrist rest, and a position tracking stylus connected to force feedback motors. The surgeon views computer-generated images of the eye and surgical instruments through the stereo operating system and controls the position and orientation of the chosen surgical instrument by moving the stylus. During the simulated instrument-tissue interactions, three feedback motors generate component force feedback along three orthogonal axes connected by thin rigid bars to the tip of the stylus. RESULTS The current proof-of-concept system provides a method for rapid learning experiences in a living eye simulation. Procedures can be recorded for playback and analysis, as well as for examination of techniques from different viewpoints (e.g., from inside the eye). Four simulated surgical instruments are available for use (scalpel, forceps, scissors, and phacoemulsifier). CONCLUSION Eye surgery simulation offers both beginning and experienced ophthalmic surgeons an opportunity to learn new techniques and skills and achieve a satisfactory level of proficiency before use of that procedure in the operating room. When fully developed, this system should shorten the learning curve for new surgeons (i.e., residents) and offer an opportunity for practice before doing a difficult case or development of new techniques by experienced surgeons. The goal of replacement of current standard training methods for surgeons awaits further refinement and adjustment of the model.

Visualization of multimodality cardiac imagery

The methods and results associated with a research program aimed at quantifying and visualizing the unified anatomic and physiologic information obtained from two complementary imaging modalities-structural information describing coronary vessel anatomy and functional information related to heart muscle physiology-are presented and discussed. The reconstruction, processing, and visualization of three-dimensional cardiovascular structure, including the procedures and results obtained from phantom and patient studies, are emphasized. The visualization methodology is designed to convey a significant amount of multimodality information in a single, meaningful display. The methodology is also designed to quantify the visualized information and to provide the information both visually and textually. Hence, both objective and subjective assessments of medical information are possible in complementary forms and in interactive fashions.<<ETX>>

Comparing objective feature statistics of speech for classifying clinical depression

Human communication is saturated with emotional context that aids in interpreting a speakers mental state. Speech analysis research involving the classification of emotional states has been studied primarily with prosodic (e.g., pitch, energy, speaking rate) and/or spectral (e.g., formants) features. Glottal waveform features, while receiving less attention (due primarily to the difficulty of feature extraction), have also shown strong clustering potential of various emotional and stress states. This study provides a comparison of the major categories of speech analysis in the application of identifying and clustering feature statistics from a control group and a patient group suffering from a clinical diagnosis of depression.

Investigating the role of glottal features in classifying clinical depression

Classifying emotion and emotion related disorders in the voice have often been studied utilizing prosodic (pitch, energy, speaking rate) and other spectral characteristics (formants, power spectral density) of the acoustic speech signal. Glottal waveform features have received little attention in the study of many emotion and emotion related disorders, but have shown strong correlations in a variety of speech pattern studies including speaker characterization and stress analysis. We employ glottal extraction techniques to obtain features related to timing, ratios, shimmer, and spectral characteristics of the glottal waveform in the study of clinical depression. Our study reports on several glottal waveform features that show very good separation among a control group and patient group of males and females suffering from a depressive disorder.

Analysis of prosodic variation in speech for clinical depression

Understanding how someone is speaking can be equally important to what they are saying when evaluating emotional disorders, such as depression. In this study, we use the acoustic speech signal to analyze variations in prosodic feature statistics for subjects suffering from a depressive disorder. A new sample database of subjects with and without a depressive disorder is collected and pitch, energy, and speaking rate feature statistics are generated at a sentence level and grouped into a series of observations (subset of sentences) for analysis. A common technique in quantifying an observation had been to simply use the average of the feature statistic for the subset of sentences within an observation. However, we investigate the merit of a series of statistical measures as a means of quantifying a subset of feature statistics to capture emotional variations from sentence to sentence within a single observation. Comparisons with the exclusive use of the average show an improvement in overall separation accuracy for other quantifying statistics.

Visualization of cardiovascular nuclear medicine tomographic perfusion studies

Several methodologies and tools for enhancing the clinicians ability to visualize and characterize perfusion defects are presented. The tools include an improved method for sampling the myocardium which reduces the partial volume effects often encountered when sampling the apex, volume-weighted and distance-weighted polar maps that enhance the information extracted from the new sampling technique, a method for visualizing perfusion information in three dimensions which decreases the distortions inherent in 2-D polar maps and also allows for unifying the perfusion information with the anatomic information obtained from 3-D coronary trees, and a method for visualizing 3-D gated perfusion information that allows a clinician to assess both perfusion and wall thickening.<<ETX>>

Computer modeling of the abdominal aorta using magnetic resonance images

An approach is described for creating a 3-D computer model of the abdominal aorta from just two projective images. The aorta is modeled by conical segments connecting circular cross sections. Accuracy of this technique is within 1 mm. From the 3-D computer model, quantitative measurements of vessel dameter, length, and position are available for any subset of the arterial structure. Visualization is enhanced by displaying the computer model rather than a direct set of images obtained from different perspectives. Ambiguities from overlapping branches can be resolved by rotating the model or by eliminating the interfering structures. This approach has been applied in both phatom studies, in which quantitative comparisons were made, andin vivo studies, in which qualitative evaluations were made.

3-dimensional registration and visualization of reconstructed coronary arterial trees on myocardial perfusion distributions

Models created independently from nuclear perfusion images of the myocardium and x-ray angiograms of the coronary arteries are placed in register to produce a unified three- dimensional representation that more clearly displays and quantifies the relationship between stenotic defects in the arterial tree and perfusion distribution in the myocardium