Donna D. Johnson

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 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.

Three dimensional ultrasound: display modalities in the fetal spine and thorax

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.

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.

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.

Gene Expression of Atrial Natriuretic Factor in Ovine Fetal Heart During Development

OBJECTIVE: The present study quantified the abundance of atrial natriuretic factor (ANF) messenger RNA (mRNA) and determined the developmental pattern of ANF gene expression in the four cardiac chambers of the ovine fetus during the last two-thirds of gestation. METHODS: Twenty-one fetuses from 13 time-dated pregnant ewes at gestational ages of 60- 145 days were used for this study. Total RNA from fetal atria and ventricles was extracted and ANF mRNA was analyzed by Northern blotting. The ANF mRNA signal was quantified by light densitometry. The abundance of ANF mRNA in the cardiac chambers across gestational ages was analyzed by linear regression analysis and one-way analysis of variance. RESULTS: Atrial natriuretic factor mRNA was much more abundant in the atria than in the ventricles of all fetuses at each gestational age studied. Atrial ANF mRNA levels were lowest in the younger fetuses at 60 days and increased with advancing gestation. Ventricular ANF mRNA levels were highest in fetuses at 60 days and decreased to almost nondetectable levels near term. No difference in ANF mRNA abundance was noted between the right and left atria or the right and left ventricles at each gestational age. CONCLUSION: A developmental pattern of ANF gene expression is demonstrated in the ovine fetal heart during the last two-thirds of gestation. This pattern shows that atrial ANF mRNA abundance increases while ventricular abundance decreases as the fetus matures. Expression of the ANF gene in the fetal period may be regulated developmentally or induced by cardiovascular changes in utero. (J Soc Gynecol Invest 1994;1:14-8)

False-positive diagnosis of spina bifida in a fetus with triploidy

Background Neural tube defects can be difficult to diagnose using ultrasound. Cranial markers, such as the lemon and banana signs, are useful sonographic findings that alert the ultrasonographer to examine the spine more carefully. The false-positive rate for the banana sign has been reported previously as zero. Case A patient with elevated maternal serum alphafetoprotein presented for a fetal ultrasound examination. Findings on the scan included a lemon sign, a banana sign, an effaced cisterna magna, and splayed lumbar vertebrae. After pregnancy termination, no spinal abnormality was detected on autopsy. X-rays of the fetal spine demonstrated narrowing in the thoracic spine. The karyotype of the fetus was 69,XXY. Conclusion The sonographic cranial findings suggestive of a neural tube defect were misleading in this case.

Informed consent: A review

Abstract Informed consent lies at the heart of the physician-patient relationship and is an integral part of any medical practice. This doctrine preserves the patients ability to participate in her own care. The physician providing primary care faces new challenges to informed consent in todays complex economic and legal environment. This article covers the history and theory behind informed consent and describes how informed consent should be used in the primary care setting.