Biomedical subjects
Publications and source records attributed to T R Nelson.
Cardiac-gated 3-dimensional fetal echocardiography can reconstruct and display cardiac structures and views not visualized with conventional 2-dimensional ultrasonography. This new technique may become an integral part of screening ultrasonography, complementing 2-dimensional fetal echocardiography when real-time imaging is incomplete.
Three-dimensional ultrasound (3DUS) has recently been introduced into clinical practice. Various techniques are available for display of the volume data. We review the importance of selecting the proper display option and rendering mode depending on the specific diagnostic question. Current display options include (1) arbitrary planar images similar to conventional two-dimensional US images, (2) surface rendering with emphasis on soft tissues or skeletal detail, (3) stereo viewing using liquid crystal glasses or red/blue glasses, and (4) cine review of gated studies. Rotation of volume data also is important in understanding/comprehending patient anatomy. The range of rotation angles varies depending on the clinical setting. Also data storage requirements increase as the number of views increases.
OBJECTIVE: To describe normal fetal spinal anatomy displayed by three-dimensional ultrasound and to determine whether three-dimensional ultrasound improves visualization of specific spinal defects. METHODS: Fetuses (n = 28) (16 normal and 12 abnormal) were examined on standard two- and three-dimensional sonographic equipment. RESULTS: In 15 of 16 normal fetuses, the spine was visualized at least from the upper thoracic area to the lower sacrum in a single three-dimensional image, and in 14 normal fetuses continuity of the ribs and spine was depicted. Neural tube defects were identified on both two- and three-dimensional ultrasounds; however, three-dimensional ultrasound displayed the level of the defect more accurately in three of the five cases. Scoliosis was recognized easily on a single three-dimensional rendered image, whereas several two-dimensional redered image, whereas several two-dimensional images were needed for the examiner mentally to reconstruct the scoliosis. CONCLUSION: Three-dimensional ultrasound may become an important tool for imaging of the fetal spine. Additional studies are necessary to determine the efficacy and cost effectiveness of this technology. However, our preliminary data suggest that presentation of the spine as a continuous structure rather than in independent two-dimensional views makes visualization of the spatial relationship of the spinal anatomy and adjacent structures easier. The ability to review the volume data using techniques not available on two-dimensional ultrasound may enable physicians to determine the extent of neural tube defects with more accuracy.
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PURPOSE: To quantify the educational activities and types of teachers that medical students had in third-year clerkships at community-based teaching hospitals. METHOD: In October-November 1992, 201 students in third-year medical clerkships at nine community-based hospitals completed a log that recorded the primary activity, site, and educator and method of education (for teaching or supervised activities) for each 15-minute interval of a 24-hour day. Each hospital offered at least three of the clerkships studied: medicine, obstetrics-gynecology (ob-gyn), pediatrics, psychiatry, and surgery. Statistical comparisons of the clerkships were done with chi-square analysis and one-way analysis of variance. RESULTS: The students received 6.5 hours a day of teaching with an instructor and committed an additional 4.9 hours to clerkship-related learning. Nearly 75% of the teaching fell to full-time faculty members and residents. In just over half of their educational activities the students participated with other learners, such as residents. The clerkships did not differ significantly in the amounts of formal teaching given; however, medicine did significantly more informal teaching, and surgery and ob-gyn did significantly more supervised practice. CONCLUSION: This preliminary study quantified medical students' educational activities in 1992 during third-year clerkships and provides baseline data describing these activities and the educators involved. Some findings may not be replicable, however, with the increasing demands of full-time faculty members in inpatient and outpatient settings and the shifting emphases in how and where residents provide instruction. Another study such as this one would help assess the effects on medical education of changes in the health care environment.
The purpose of this study was to evaluate the anatomy of the cerebral circulation, particularly the circle of Willis, using three-dimensional ultrasound (3DUS) imaging. Image data were obtained through the right transtemporal window from 8 young, healthy volunteers by acquiring gray-scale and color Doppler spectral (CDI) and energy (CDE) images using two-dimensional ultrasound equipment with a 2-MHz probe. Images and transducer position coordinates were fed into a graphics workstation, reprojected, analyzed to extract the blood flow signal, volume rendered, and displayed interactively. The architecture of the cerebral circulation was evaluated from multiple orientations using stereo viewing glasses and rotation to enhance the understanding of vessel position. The primary vessels of the cerebral circulation including the circle of Willis and bilateral views of the branching arteries (middle, anterior, and posterior cerebral arteries and internal carotid artery) could be imaged readily with 3DUS through one transtemporal window. Acquisition time was typically less than 30 seconds. Volume-rendering methods greatly assisted in showing the overall spatial relationships and continuity of cranial vessels. Secondary branches of the cerebral arteries were seen in 2 patients. Color data from two-dimensional ultrasound imaging that otherwise might be identified as artifact was found to represent continuous small vessels on three-dimensional viewing. 3DUS facilitates imaging of cranial vascular anatomy by clarifying overall spatial relationships and enhancing comprehension, compared to two-dimensional ultrasound methods. The method is rapid and the circle of Willis can be visualized from one side of the head.
Morphogenesis of the cardiovascular system is likely linked to its functional development. This report presents an approach to functional assessment of early cardiovascular development using parametric imaging based on videodensitometry. Trypan blue was injected into the sinus venosus of chick embryos at stage 20 (3.5 d of incubation). Images were recorded on videotape, digitized, and analyzed by a microcomputer. A sampling window was placed over the entire image, and a densogram (time-density curve) for each pixel in the window was obtained. Parameters extracted from the densogram and its derivative were plotted in form of: 1) maximal image, 2) peak derivative image, and 3) time to peak derivative image. This approach revealed isochronal lines that divide the aortic arch and dorsal aorta into several segments. Regional flow velocity at these segments was estimated by dividing the distance between isochronal lines by the time interval. Flow velocity at the mid-systolic phase at the dorsal aorta and at the fourth aortic arch was 35.9 and 45.0 mm/s, respectively. Shear rate at the vessel wall was estimated to be 2.7 times larger at the fourth aortic arch than at the dorsal aorta. The extensive remodeling experienced by the aortic arch system compared with the dorsal aorta could be related to increased shear rate on the walls of the aortic arches.
Tubulointerstitial nephritis antigen (TIN-ag) is a recently described basement membrane component reactive with autoantibodies in some forms of autoimmune mediated tubulointerstitial nephritis. Immunofluorescence studies using polyclonal and monoclonal antibodies have indicated a restrictive tissue distribution for TIN-ag, with the site of most prominent expression the kidney tubular basement membrane. However, Lewis rat does not demonstrate any immunoreactivity for TIN-ag and does not develop tubuloinsterstitial nephritis after injection of tubular basement membrane material. As TIN-ag would appear to be a molecule of biological significance, experiments were designed to explore the presence or absence of this macromolecule in the Lewis rat model. Southern blotting of Lewis rat genomic DNA revealed the presence of gene sequences corresponding to TIN-ag. RTPCR analysis of Lewis rat kidney cortex total RNA illustrated the expression of a TIN-ag gene product. Western blotting demonstrated the presence of TIN-ag protein forms in kidney cortical homogenates of Lewis rat. The data suggest either extensive epitope masking or expression polymorphism of TIN-ag in the Lewis rat.
Primary care physicians rely on specialists. Specialists are too expensive to be located at every clinical site requiring a practical means for specialists to help without requiring patients or specialists to travel for consultation. To address the challenge of providing primary care physician access to specialists, we are developing a clinical prototype system for the high-speed access and transfer of patient data and images within Radiology Departments, Medical Centers and Health Care Networks. The key components of the system are: a high-bandwidth network (100 Mbit/s upgradeable to ATM); an image server system with a 30-60 day patient image on-line archive ( < 10 sec. recall) coupled with a long term archive; viewing consoles matching existing film display paradigms located within the medical center and clinics providing rapid access to patient data and diagnostic images for house staff (OR/ER/ICU); clinician access to the image archive on a consultation basis in office computers; and image review applications which closely follow the established paradigms used by clinicians. Using our system primary care physicians can rapidly review patient data locally obtaining additional consultation from tertiary sites while the patient is present. Clinics and outlying medical centers gain rapid access to specialists with physicians in different cities discussing patient diagnostic and management issues in a shared environment leading to instantaneous data analysis and diagnosis further reducing health care costs and enhancing patient care.
PURPOSE: To evaluate the display modalities of three dimensional ultrasound (3D US) in the prenatal assessment of the fetal spine and thorax. METHOD: Twenty prenatal spine examinations (mean gestational age: 21 weeks, 15 normal findings, five pathological cases) were performed with a commercially available 3D US device. The visualization of fetal spine and rib anatomy and pathology by 3D US display was evaluated using various rendering methods and the optimal method was determined in regard to comprehensive diagnostic display. RESULTS: Demonstration of continuity of both the spine and the ribs could be achieved by 3D US. Visualization of clavicles, scapula and iliac bone was possible on rendered images. CONCLUSION: 3D US offers an additional diagnostic tool for prenatal assessment of the fetal spine and ribs; it provides a continuous demonstration of curved or tortuous structures in the rendered image. It improves comprehension of complex anatomy by providing a simultaneous display of all orthogonal sectional planes.
The aim of this study was to evaluate the accuracy of three-dimensional ultrasound distance and volume measurements using a commercially available three-dimensional ultrasound scanner. Sixty-two distance measurements were performed twice on an ultrasound tissue-mimicking phantom located in a water bath. Three-dimensional ultrasound distance measurements were compared to the actual distance. Volume measurements were made in a water bath with 21 balloons of various shapes ranging in volume from 20 ml to 490 ml. Three-dimensional ultrasound volume measurements were compared to actual balloon volumes and to conventional two-dimensional ultrasound volume calculations. The mean absolute error in three-dimensional ultrasound distance measurements was 1.0 +/- 0.8% (range, -2.3 to +1.9%) in the plane of acquisition and 1.0 +/- 0.6% (range, -2.0 to -0.2%) for planes with other orientations. Three-dimensional ultrasound volume measurements showed a mean absolute error of 6.4 +/- 4.4% (range, -6.0% to +15.5%), which was considerably better than two-dimensional ultrasound volume estimates having a mean absolute error of 12.6 +/- 8.7% (range, -27.5% to +39.2%). Volume measurements using two-dimensional ultrasound methods were much less accurate than three-dimensional ultrasound methods for irregularly shaped objects. In conclusion, our data show that three-dimensional ultrasound measurements of distance and volume are sufficiently accurate to use clinically.
The purpose of this study was to assess the accuracy of in vivo measurement of organ volume using 3DUS and compare the results to 2D sonographic methods using the urinary bladder as the target organ and voided urine volume for validation. Fifty normal volunteers were studied. 2D volume measurements were based on length, width, and depth data and assumed a regular geometric model. 3D volume measurements were based on masked slices with the voxels integrated over the entire bladder. Voided urine volumes ranged from 35 ml to 701 ml. Residual urine volume was present in 48% of the subjects and ranged from 1% to 14% of the voided volume. 2D volume estimates for all 50 subjects had a mean absolute value of the error of 27.5% +/- 17.8%. 3D volume measurements had a mean absolute value of the error of 4.3% +/- 3.7% (transverse) and 5.6% +/- 3.8% (longitudinal). 3DUS provided more accurate volume measurements than 2DUS, particularly for irregularly shaped organs.
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The purpose of this work was to assess the functional dynamics and anatomy of the cardiac chambers and great vessels in the fetus (18 to 36 weeks) using in utero three-dimensional ultrasonographic imaging. Fifteen patients were studied using conventional two-dimensional sonographic equipment incorporating a position sensor attached to the transducer and a graphics workstation. Sonographic image data were acquired at 30 images per second and required less than 30 seconds per data set. Fetal heart rate and time in the cardiac cycle were determined and used to synchronize image data for reprojection into a volume at the appropriate part of the cardiac cycle. Volume data were analyzed, rendered, and displayed interactively. Three-dimensional sonographic volume data demonstrated fetal cardiac anatomy from multiple orientations and showed the myocardium, valves, ventricles, and atria clearly. The images showed good correlation with currently available embryologic-anatomic-pathologic data. Dynamic and spatial relationships among chambers, valves, and great vessels were readily appreciated. Three-dimensional sonographic imaging of the fetal heart provides both anatomic and functional information regarding the valves, myocardium, great vessels, and chamber dynamics. Interactive three-dimensional cinegraphic display enhances visualization of cardiac anatomy, which can be difficult to appreciate with two-dimensional methods. The methods presented in this work demonstrate the feasibility of three-dimensional fetal echocardiography.
Tubulointerstitial nephritis antigen (TIN-ag) is a 58-kDa basement membrane glycoprotein that is recognized by human autoantibodies in certain forms of tubulointerstitial nephritis. To further characterize this macromolecule and isolate cDNAs encoding TIN-ag, amino acid sequences from tryptic peptides were used to design and synthesize primers in order to amplify a probe for screening a rabbit kidney cortex cDNA library. A cDNA encoding TIN-ag was cloned and sequenced. The predicted amino acid sequence deduced from this cDNA includes the chemically determined sequences of peptides derived from TIN-ag, supporting its authenticity. The predicted amino acid sequence also shows that the carboxyl-terminal region of the molecule exhibits a 30% homology with human preprocathepsin B, a member of the cysteine proteinase family of proteins. A domain in the amino-terminal region of TIN-ag contains an epidermal growth factor-like motif that shares homology with laminin A and S chains, alpha 1 chain of type I collagen, von Willebrand's factor, and mucin, suggesting structural and perhaps functional similarities among these molecules. Immunoprecipitation of in vitro generated recombinant protein using a TIN-ag-specific monoclonal antibody (A8), confirms the identity of the isolated TIN-ag cDNA. In this report the cDNA and predicted amino acid sequences of TIN-ag are presented. Knowledge of the primary structure of TIN-ag will facilitate our understanding of the molecular structure of this novel basement membrane component and may provide clues toward understanding its functional role.
The papers in this issue show that the feasibility of three-dimensional ultrasound methods in the clinical setting using commercially available equipment is nearby. Their results demonstrate some of the advantages compared to two-dimensional ultrasound and other diagnostic modalities, including reduced scanning times that will offer more cost-effective use of equipment and sonographer time. Other benefits of three-dimensional ultrasound include allowing the physician: to evaluate arbitrary planes not available with two-dimensional ultrasound due to patient body habitus; to measure organ dimensions and volumes; to obtain anatomic and blood flow information; to improve assessment of complex anatomic anomalies; to confirm normalcy; to standardized the ultrasound exam procedures; to enhance the understanding of physicians in primary care facilities and communicate volume data over networks for consultation at tertiary facilities. Standardization of the ultrasound examination protocols can lead to uniformly high-quality examinations and decreased health care costs. Ultimately, three-dimensional ultrasound imaging will make it easier for primary care physicians to understand complex patient anatomy. Tertiary care physicians specializing in ultrasound can further enhance the quality of patient care by using high-speed computer networks to review volume or dynamic data at specialization centers with primary care physicians. Access to volume data at specialization centers affords more sophisticated analysis and review, further augmenting patient diagnosis and treatment and reducing health care costs.
Sonographic evaluation of the fetal spine is an essential part of any fetal survey, and it is included in the current American Institute of Ultrasound in Medicine/American College of Radiology and American College of Obstetrics and Gynecology guidelines for obstetric sonography [1, 2]. In this paper, we review the current knowledge of anatomy of the normal fetal spine and the sonographic findings associated with spinal anomalies, with special emphasis on neural tube defects. Important cranial clues to a spine abnormality initially may be more obvious at sonography than the spine abnormality itself, and the general significance of these clues is provided. The expanding role of prenatal maternal serum and amniotic fluid testing is explored, as are the benefits and modifications these bring to sonographic evaluations. Finally, the potential benefits of the rapidly advancing technology of three-dimensional sonography are introduced.
OBJECTIVE: Evaluation of the complete anatomy of the thoracic skeleton in the developing fetus often is difficult with conventional two-dimensional (2D) sonography because of the curvature of the bones. The purpose of the present work was to assess the ability of three-dimensional (3D) sonography to provide a more complete representation of the fetal thoracic skeleton than available with 2D sonography. SUBJECTS AND METHODS: We performed 3D sonographic imaging in eight healthy volunteer pregnant women after obtaining informed consent. Conventional 2D sonographic equipment was adapted to obtain 3D data and to produce volume-rendered images. The 3D sonographic images of the bony spine and thorax were evaluated for clarity with which the vertebral bodies, ribs, scapulae, clavicles, and overall thoracic anatomy were depicted. RESULTS: The vertebral bodies, spine, and ribs were identifiable on 3D sonograms, which clearly showed the structural continuity of the spine and ribs in all fetuses. Zoomed images of subregions of the spine were useful for showing details of the vertebrae. Stereo glasses and rotation of the volume data proved useful in appreciating the spatial relationships of the spine and rib cage. CONCLUSION: Three-dimensional sonography provides additional information about the fetal thoracic skeleton to that furnished by 2D sonography by presenting the thorax as a coherent structure rather than as a series of cross-sectional slices.