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Biomedical subjects

D H Pretorius

Publications and source records attributed to D H Pretorius.

At least 37 records · Page 2Linked to original sources
PubMed1999

Normal splenic volumes estimated using three-dimensional ultrasonography.

The purposes of this study were to determine splenic volumes using three-dimensional ultrasonography and to compare these measurements with two-dimensional splenic indices. Fifty-two healthy volunteers were studied. Two-dimensional volume measurements were based on length, width, and thickness, and the splenic index was calculated using the standard prolated ellipsoid formula (length x width x thickness x 0.523). Three-dimensional volume planar measurements were obtained with a slice by slice technique by manually drawing a region of interest around the spleen from one end of the sweep to the opposite end. These measurements were recorded three times by two observers. In addition, in vitro determination of splenic volume was performed using three cadaveric human spleens in a water bath. No statistically significant interobserver or intraobserver variability was present for either two-dimensional or three dimensional ultrasonography. Three-dimensional sonographic estimations of planar splenic volumes and ellipsoid splenic volumes were consistently smaller than two-dimensional sonographic estimations of splenic volumes. Three-dimensional sonographic splenic volumes calculated in vitro using the planar method were accurate to within 2% of in vitro water displacement volumes. Three-dimensional ultrasonography is potentially superior to two-dimensional sonography for evaluation of irregularly shaped objects, such as the spleen, and can provide improved accuracy over that of traditional two-dimensional techniques.

Adult↗
PubMed1998

Three-dimensional ultrasound imaging.

The objective of this article is to provide scientists, engineers and clinicians with an up-to-date overview on the current state of development in the area of three-dimensional ultrasound (3-DUS) and to serve as a reference for individuals who wish to learn more about 3-DUS imaging. The sections will review the state of the art with respect to 3-DUS imaging, methods of data acquisition, analysis and display approaches. Clinical sections summarize patient research study results to date with discussion of applications by organ system. The basic algorithms and approaches to visualization of 3-D and 4-D ultrasound data are reviewed, including issues related to interactivity and user interfaces. The implications of recent developments for future ultrasound imaging/visualization systems are considered. Ultimately, an improved understanding of ultrasound data offered by 3-DUS may 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 networks to review volume ultrasound data at specialization centers. Access to volume data and expertise at specialization centers affords more sophisticated analysis and review, further augmenting patient diagnosis and treatment.

Algorithms↗
PubMed1998

Imaging of placental vasculature using three-dimensional ultrasound and color power Doppler: a preliminary study.

OBJECTIVE: To assess placental vasculature using color power Doppler and three-dimensional ultrasound techniques. DESIGN: A prospective study was performed in patients to correlate visualization of placental vessels in vivo with known anatomy. SUBJECTS: Fourteen normal patients and one patient with intrauterine growth restriction were recruited to the study. METHODS: Vessels were assessed with regard to, first, the number of vessels seen within the placenta, second, the branching pattern of the vessels within the placenta, third, the number of vessels seen along the surface of the placenta, and, last, the number of vessels seen in the maternal circulation. RESULTS: Our results show that the placental vessels seen with this technique correlate well with known anatomy. A progressive increase in the number of intraplacental vessels and the number of vascular branches observed was seen with increasing gestational age. Volume data review using three orthogonal planar images had two distinct advantages. First, they could be obtained from orientations not possible using two-dimensional ultrasound alone, and, second, they could be viewed in conjunction with volume-rendered images to allow for referencing and identification of specific vessels. Volume-rendered images were valuable in allowing the observer to acquire an improved overall understanding of placental anatomy. They also assisted the observer in following the continuity of vessels as they wrapped around and twisted through three-dimensional space. Stereo viewing was helpful in distinguishing overlapping vessels. CONCLUSIONS: Our study showed that sonographic volume imaging combined with color power Doppler imaging methods allowed for individual vessels in the placenta to be identified, both in the fetal and maternal circulations.

Arteries↗
PubMed1998

Three-dimensional ultrasound examination of the fetal hands: normal and abnormal.

PURPOSE: To assess particular features of fetal hand evaluation using three-dimensional ultrasound, and to determine whether any advantage is offered by three-dimensional over two-dimensional ultrasound in fetal hand evaluation. METHODS: Three-dimensional fetal data were collected prospectively from 44 hands in 40 fetuses from a predominantly high-risk patient population. All had a concurrent two-dimensional ultrasound examination of the hands. Diagnoses from two- and three-dimensional ultrasound examinations were compared and additional information from the three-dimensional volume assessment was noted. Three-dimensional assessment of distal forearm bones, wrist position, finger configuration and number of metacarpals and digits was recorded. RESULTS: Hands were appropriately identified as normal (32/32) or abnormal (12/12) by both two- and three-dimensional ultrasound. Three-dimensional ultrasound provided additional information when compared to two-dimensional ultrasound in both normal and abnormal hands, including the provision of three orthogonal planes with one volume acquisition, allowing rotation of the volume so that hands could be evaluated in planes not possible during two-dimensional imaging, assessment of a hand with loosely curled fingers as normal, the ability to evaluate thumb and fingers simultaneously, and improved assessment of abnormal hands. CONCLUSIONS: Three-dimensional ultrasound offers the potential to provide greater information in fetal hand evaluation for both normal and abnormal hands.

Embryonic and Fetal Development↗
PubMed1998

Hydroceles identified prenatally: common physiologic phenomenon?

Though the reported frequency of infant hydrocele has varied, the frequency of hydrocele in the fetus has not been studied. Our purpose was to determine the frequency of fetal hydrocele in the third trimester and subsequent outcome. Of the 123 fetuses studied, 19 fetuses had hydroceles. Of these, 14 babies were normal at follow-up, one baby had a persistent hydrocele, and four babies were lost to follow-up. Our study suggests that hydrocele is a relatively common finding in the third trimester in utero. Moreover, it suggests that parents can be reassured that, in the absence of other abnormalities, a hydrocele is usually a physiologic finding which resolves spontaneously.

Female↗
PubMed1998

Three-dimensional ultrasonography of the fetal distal lower extremity: normal and abnormal.

The objective of this study was to compare two-dimensional and three-dimensional ultrasonographic evaluation of fetal distal lower extremities. Data from two-dimensional and three-dimensional ultrasonographic examinations from 40 distal lower extremities in 33 fetuses from a predominantly high-risk patient population were compared. Three-dimensional ultrasonography routinely provided three orthogonal planes (coronal, sagittal, and axial) for distal lower extremity evaluation. Specific features of distal lower extremity evaluation were not different using two-dimensional and three-dimensional ultrasonography. Rotation of the rendered volume provided assistance in assessing all but one of 40 distal lower extremities. Time from image acquisition to assessment for two views (coronal and sagittal) was longer with three-dimensional ultrasonography (8.2 min) than with two-dimensional ultrasonography (3.2 min). Confidence in the diagnosis of abnormal distal lower extremities was slightly improved using three-dimensional ultrasonography compared to two-dimensional ultrasonography. Pregnancy management was assisted in three of the four cases with isolated limb anomalies. In conclusion, three-dimensional ultrasonography improves the ability to evaluate the fetal distal lower extremity because of the multiplanar nature of volume assessment and the ability to rotate volume data sets. In addition, it provides assistance in counseling families, particularly for cases involving isolated limb anomalies.

Female↗
PubMed1998

Three-dimensional gray scale ultrasonographic imaging of the celiac axis: preliminary report.

The vessels of the celiac axis were evaluated in 16 healthy volunteers with three-dimensional gray scale ultrasonography. Sonographic volume data sets were obtained from both sagittal and transverse planes. The visualization of specific branches of the celiac artery (hepatic, splenic, left gastric, gastroduodenal, left hepatic, right hepatic, right gastric) was evaluated, and each vessel was placed in one of four categories on the basis of the appearance of the specific vessel and image clarity (not seen, poorly seen, adequately seen, well seen). Each vessel was evaluated on an initial two-dimensional scan and on a second scan using the entire volume to optimize and follow the designated vessel using rotating, referencing, and scrolling display capabilities. The ability to manipulate an entire volume improved visualization of the selected vessels as noted by an improved score. The proportion of vessels in the "not seen" and "poorly seen" categories decreased from the initial scan (62.5%) to the scan utilizing the entire volume (36%). Alternatively, the percentage of vessels in the "adequately seen" to "well seen" categories improved from 37.50% on the initial examination to 64% on the scans using the entire volume to depict vascular anatomy. The optimal plane to image each vessel depended on the course of a specific vessel. For optimal imaging of all the selected vessels, both sagittal and transverse volume acquisitions and both sagittal and transverse planes were needed. Three-dimensional imaging provided a new imaging plane (coronal) that was useful in following and identifying vessels, especially those vessels coursing in a right to left direction. Vascular variants were identified by this technique in two of 16 subjects. Vascular imaging was improved with three-dimensional ultrasonography, and this imaging method may provide additional assistance in decision making when evaluating abdominal vessels.

Adult↗
PubMed1998

Three-dimensional ultrasonography of normal fetal heart: comparison with two-dimensional imaging.

Thirty-one high-risk patients (16 to 35 weeks' gestation) underwent two-dimensional and three-dimensional ultrasonography to compare two-dimensional and non-cardiac-gated three-dimensional ultrasonography of the normal fetal heart. After normal two-dimensional studies, three-dimensional sonographic volumes were acquired without cardiac gating in transverse and longitudinal planes. Standard cardiac views were derived from three-dimensional data, analyzed, and rated as follows: (1) not identifiable, (2) identifiable but inadequate for diagnosis, (3) adequate, and (4) excellent. Two-dimensional ultrasonography demonstrated better yields of diagnostically acceptable images of basic echocardiographic views (four-chamber view, 100% for two-dimensional sonography versus 10 to 71% for three-dimensional sonography; right ventricular outflow tract, 42% for two-dimensional versus 6 to 26% for three-dimensional ultrasonography; left ventricular outflow tract, 71% for two-dimensional versus 13 to 45% for three-dimensional sonography). In one subject three-dimensional ultrasonography was superior to two-dimensional sonography in demonstrating an outflow tract. Aortic and ductal arches were not imaged with the two-dimensional technique but were available from the acquired three-dimensional volumes in 3 to 32% and 23%, respectively. False-positive and false-negative findings were observed on three-dimensional ultrasonograms. Overall, compared to two-dimensional ultrasonography, non-cardiac-gated three-dimensional sonography yielded inadequate reconstructed image quality of basic echocardiographic views (four-chamber view, right ventricular outflow tract, left ventricular outflow tract). Three-dimensional ultrasonography, however, shows potential for allowing nonechocardiographers to acquire some diagnostically acceptable views of the aortic and ductal arches.

Echocardiography, Three-Dimensional↗
PubMed1998

Three-dimensional fetal echocardiography: gated versus nongated techniques.

The purpose of this study was to compare gated with nongated three-dimensional fetal echocardiography in terms of the ability to demonstrate fetal cardiac anatomy. We examined nine fetuses in utero using conventional two-dimensional sonographic imaging equipment, an electromagnetic position sensor, and a computer-graphics workstation. Free-hand sweeps were performed through the fetal heart and great vessels in either transverse or sagittal orientations with respect to the fetal heart. Seven transverse and five sagittal sweeps were selected for reconstruction and analysis. Cardiac gating was performed by using a temporal Fourier transform to determine the fundamental frequency of cardiac motion. Two-dimensional data from each sweep were reprojected to a series of volume data sets. Each series was then condensed to a single volume, so that each two-dimensional sweep could be compared with its respective gated and nongated volume data sets. The two-dimensional data were reviewed utilizing a display with forward and backward cineloop capability. The gated and nongated volume data sets were displayed interactively as a series of three orthogonal planes, with the ability of the observer to control the location of each image plane within the volume. The gated data were animated with variable display frame rates. Conventional two-dimensional imaging provided a fairly complete evaluation of the fetal heart when scanning included the four-chamber view with a sweep across the outflow tracts. Nongated three-dimensional fetal echocardiography allowed visualization of some structures and views not demonstrated with two-dimensional ultrasonography. Gated three-dimensional fetal echocardiography provided significantly better visualization and comprehension of cardiac anatomy than nongated three-dimensional fetal echocardiography. The superiority of gated over nongated three-dimensional fetal echocardiography appears to come from both improved image quality and the anatomic clues that derive from the ability to view cardiac motion.

Echocardiography, Three-Dimensional↗
PubMed1997

Usefulness of gated three-dimensional fetal echocardiography to reconstruct and display structures not visualized with two-dimensional imaging.

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.

Data Display↗
PubMed1997

Three-dimensional ultrasound: display modalities in obstetrics.

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.

Echocardiography, Doppler, Color↗
PubMed1997

Three-dimensional ultrasound of the fetal spine.

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.

Female↗
PubMed1997

Anencephaly with holoprosencephalic facies due to ring chromosome 18.

An anencephalic infant with holoprosencephalic facies and ring chromosome 18 [r(18)] is reported with review of the pertinent literature. Although the association of anencephaly and holoprosencephalic facies is well established, this is the first instance of an accompanying karyotypic abnormality. Review of other r(18) cases suggests that this is not a coincidental finding. Karyotype analysis appears warranted in cases of anencephaly with holoprosencephalic facies.

Anencephaly↗