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.
Explore the source record for details and available documents.
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.
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.
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.
OBJECTIVE: The purpose of this study was to determine if three-dimensional (3D) sonography could improve prenatal evaluation of fetal lips in comparison with conventional two-dimensional (2D) sonography. MATERIALS AND METHODS: Sixty-one high-risk pregnant women and 10 low-risk pregnant women were examined with conventional 2D sonography followed by 3D sonography with a volume transducer. The ability to visualize cleft lips and normal lips was compared between the two techniques. RESULTS: Of the 71 fetuses studied, faces were seen in 68 and not seen in three by either 2D or 3D sonography. Abnormal lips were seen in five fetuses on both 2D and 3D sonograms. Of the remaining fetuses, 3D sonography was able to confirm the presence of a normal lip in 92% (58/63) compared with 76% (48/63) with 2D sonography. In the subgroup of fetuses less than 24 weeks' estimated gestational age, 3D sonography confirmed a normal lip in 93% (38/41) of fetuses as compared with 68% (28/41) for 2D sonography. There was no difference between 3D and 2D in the subgroup of fetuses older than 24 weeks. One false-positive finding of cleft lip was observed at 36 weeks' gestational age with the rendered surface display on 3D sonography, whereas the 3D planar views of the same volume showed the lips to be normal. CONCLUSION: 3D sonography was able to confirm the presence of normal lips more frequently than did 2D sonography in fetuses less than 24 weeks' gestational age. Abnormal lips were seen on both 2D and 3D sonograms; however, 3D images of cleft lip were easier to understand for both the family and clinical colleagues.
The purpose of this study was to assess the accuracy of distance and volume measurements obtained by three-dimensional ultrasonography. A tissue-mimicking phantom was scanned using a prototype three-dimensional sonographic imaging system to verify distance measurements. Measurements were taken from the reconstructed three-dimensional sonographic data and compared to the real distances. Volume measurements were obtained by scanning 30 balloons of various shapes, sized 23 ml to 2400 ml. Each balloon was scanned twice in two orientations; three different masks were accomplished for each volume. Each volume measurement of 180 three-dimensional sonographic measurements was compared to conventional two-dimensional ultrasonographic volume estimates and to the actual, measured balloon size. Distance measurements had a mean error of 0.02 +/- 3.65% (range, -4.27 to 7.18%). Two-dimensional sonographic volume estimates using traditional scanner based methods had a mean error of 13.7 +/- 10.1%. Three-dimensional sonographic volume measurements had a mean error of 2.2 +/- 2.9% for regular and irregular objects over the entire range of volumes. The masking required 10 to 30 min. The field of view varied from 10 to 24 cm with a mean object depth of 9.8 cm. Three-dimensional ultrasonographic methods can provide accurate volume measurements of regular and irregular objects and offer improved accuracy compared to traditional two-dimensional methods.
Evaluation of the fetal face is an essential part of the sonographic examination for high risk pregnancies. Even under optimal conditions, the complex curvature of the face makes it difficult to obtain adequate images with two-dimensional ultrasonography, and many cross-sectional images are required to obtain a complete impression. The purpose of this paper is to show preliminary work in assessing the utility of three-dimensional ultrasonographic visualization of the fetal face. Fetal facial features were evaluated with three-dimensional sonography by scanning with a volume transducer and compared to conventional two-dimensional ultrasonographic images in 27 fetuses (gestational ages 10 to 39 weeks). Surface rendered three-dimensional sonographic images of the fetal face were obtained in 24 of 27 fetuses. In four cases the upper lip was clearly imaged on three-dimensional ultrasonography when it could not be seen on two dimensional ultrasonography. Information requiring multiple planes with two-dimensional ultrasonography could be demonstrated on a single image from three-dimensional ultrasonography. Images of abnormal faces were seen with both two- and three-dimensional ultrasonography in two cases of cleft lip and one case of holoprosencephaly. Volume data acquisition required approximately 10 sec and reconstruction required approximately 5 sec with instantaneous review of planes through the volume data set. Surface rendering required 2 to 10 min depending on the angular viewing range. Three-dimensional ultrasonography has the potential to provide improved visualization of the fetal face compared with conventional two-dimensional sonographic imaging.