Fetal exposure from endovaginal ultrasound examinations in the first trimester.

Ultrasonic obstetrical examinations during the first trimester are now often performed endovaginally with higher-frequency (5-7.5 MHz) transducers operating closer to the fetus than for transabdominal examinations. To estimate exposure to the fetus, propagation distances were obtained from a retrospective study of 100 normal first-trimester endovaginal B-mode examinations. No significant dependence of attenuation on gestational age was observed. The range of the attenuation estimates was 1.8-10.4 dB. A mean attenuation of 5.0 dB at 5 MHz for an average depth of 2.8 cm resulted in an attenuation coefficient of .36 dB/cm/MHz. Exposure (ISPTA) to the fetus at each gestational week from three ultrasound units was very similar: worst-case values of the 100 cases ranged from 1.2-1.9 mW/cm2, well within the Food and Drug Administration (FDA) guidelines of 94 mW/cm2 for derated focused transducers. Energy density deposited to the anterior surface of the fetus during a typical examination, assuming that the transducer is kept stationary over one area for the entire period of the examination (which is unlikely), ranged from 143-217 mJoules/cm2, within the American Institute of Ultrasound in Medicine (AIUM) recommendations.

Inter- and intra-observer variability of Doppler peak velocity measurements: an in-vitro study.

To determine the variability of pulsed Doppler peak velocity measurements, four radiologists with differing experience were tested using a calibrated flow phantom. Two ultrasound units, three probes and eight velocity rates varying between 40.5 and 78 cm/sec were studied, with a total of 303 measurements. The results were normalized against a set of 106 separate measurements made under highly-controlled conditions. The residual error standard deviation (not attributable to any systematically varied factor, including the velocity rate) was 6.8 cm/sec, with most of the remaining variation due to changing transducer or machine. Observer/equipment interactions accounted for 15.8% of the observed variability. The duration of the radiologist's Doppler experience had no significant effect.

Detection of renal stones with real-time sonography: effect of transducers and scanning parameters.

Three experiments with a variety of transducers and scanning parameters were designed to investigate if renal stones could be detected with greater certainty by using particular transducers or scanning parameters. First, the lateral resolution, derived from the -6-dB size of the beam profile, was measured at various depths for five transducers commonly used for renal sonography. Second, an in vitro test object was constructed from bovine liver, porcine kidneys, and two renal calculi to access gray-scale map effects on shadow visibility before and after storage in the digital scan converter. The third experiment combined 15 lithotripsy patients with known renal stones with 16 patients in whom the results of renal sonography and other radiographic procedures suggested renal calculi. The group of 15 patients was scanned several times with the transducers and gray-scale maps studied earlier, and the group of 16 patients was scanned only with one transducer and one gray-scale map. On radiographs, 12 of the 16 patients did not have renal calculi. Sonograms of the test object showed that low-contrast images were best for detection of posterior shadows. Three radiologists interpreted the 31 sonograms with a sensitivity of 81% and a specificity of 86% for detecting renal stones. For the 15 cases of renal stones scanned with a variety of transducers, the three radiologists found that annular-array transducers depicted stone shadowing with less ambiguity than mechanical sector transducers did 81% of the time.

A new electronically enhanced biopsy system: value in improving needle-tip visibility during sonographically guided interventional procedures.

Sonographically guided fine-needle biopsy procedures are hampered by poor visibility of the needle tip. This study was performed to evaluate a new system for placing needles under sonographic guidance. The Biosponder needle (Advanced Technology Laboratories, Bothell, WA) incorporates a specialized stylet with a passive sensor at its tip. When an ultrasound pulse is detected by the sensor, an electrical signal is transmitted to the sonographic unit by a battery-powered electronic module connected to the stylet and to the scanner. This signal is converted into a bright, flashing marker on the screen at the precise location of the needle tip. The Biosponder system, which uses 20- or 22-gauge needles, was compared with a 20-gauge Turner needle (Cook, Bloomington, IN) in 18 patients with masses or fluid collections and two patients requiring nephrostomy tube placement. The tip of the Turner needle could not be localized precisely in any patient. The shaft of the Turner needle was seen clearly in 13 patients, poorly in three, and was not visualized at all in four patients. Excluding four instances of mechanical failure, the Biosponder system allowed precise localization of the needle tip in every patient and was consistently rated as easier to use than the Turner needle. We conclude that the Biosponder needle, with its precise tip localization and ease of use, is a valuable tool for sonographically guided needle placement.

Endovaginal sonographic diagnosis of dilated fallopian tubes.

Twelve cases of fallopian tube dilatation were diagnosed in 10 patient by using endovaginal sonography. The diagnosis was confirmed by surgery in seven patients and by hysterosalpingography in three. A tubular shape was present in every case. Other sonographic features included a well-defined echogenic wall, a folded configuration, and linear echoes protruding into the tube lumen. Dilated tubes were distinguished from bowel loops by a lack of peristaltic activity and from pelvic veins by a lack of moving low-level echoes on real-time sonography. We conclude that the findings of dilated fallopian tubes on endovaginal sonography are sufficiently characteristic to allow the diagnosis to be made with this technique.

The pulsatile portal vein in cases of congestive heart failure: correlation of duplex Doppler findings with right atrial pressures.

To better understand portal vein pulsatility in congestive heart failure, the authors compared portal vein spectral patterns to right atrial pressures measured with a Swan-Ganz catheter in 17 adult patients suspected of having congestive heart failure. Portal vein pulsatility was also evaluated in 17 healthy adults. A pulsatility score (scale, 1-5) based on a ratio of minimum to peak portal vein velocity was assigned. A score of 1 indicated continuous, monophasic flow, while a score of 5 indicated that flow reversal was observed with each cardiac cycle. All 17 healthy volunteers had portal vein pulsatility scores of 2 or less. Among the 17 patients suspected of having congestive heart failure, seven had normal right atrial pressure (less than 10 mm Hg) and pulsatility scores of 2 or less. Among the 10 patients with a right atrial pressure of 10 mm Hg or greater, six had pulsatility scores of 3 or greater (sensitivity, 60%; specificity, 100%). Greater than 50% of the variation in portal vein score is explained by changes in right atrial pressure. Review of echocardiograms in 13 of 17 patients showed no significant correlation between the degree of tricuspid regurgitation and portal vein score. Portal vein pulsatility is a sign of elevated systemic venous pressure.

Sonographic findings after surgical ablation of the endometrium.

OBJECTIVE: Endometrial ablation is a new surgical technique that is an alternative to hysterectomy in women with dysfunctional uterine bleeding. The endometrium is either coagulated or resected in an attempt to render the patient amenorrheic. Because of the newness of the procedure, no report of radiologic findings after endometrial ablation has been published. Accordingly, the sonographic appearance of the uterus after endometrial ablation is described. MATERIALS AND METHODS: Using transvaginal sonography, we examined a select group of 16 women, seven of whom were symptomatic after endometrial ablation. All patients had a preoperative diagnosis of menorrhagia not responsive to conventional hormonal therapy and no evidence of cancer. RESULTS: In the seven symptomatic patients, sonography showed that postoperatively two had hematometra, one had a nonviable intrauterine pregnancy, and four had residual islands of functioning endometrial tissue alone or in combination with hematometra. In nine asymptomatic patients, postoperative sonography showed seven had normal findings except for leiomyomata and two had residual islands of functioning endometrial tissue. CONCLUSION: Sonographic examination of the uterus after endometrial ablation provides a method for evaluating symptomatic patients and for identifying any remaining endometrium that could later become symptomatic.

Color Doppler imaging of the hepatic vasculature.

Duplex sonography added a new dimension to real-time sonographic imaging and can be used to characterize flow dynamics. Unfortunately, duplex sonography also has significant drawbacks, most of which are the result of the limited sampling ability of pulse-gated technology and the inability to provide a global display of Doppler information. Sonographic imaging of intraabdominal vessels has improved markedly with the advent of color Doppler techniques. This article reviews the use of color Doppler sonography in the evaluation of hepatic vessels. The complementary role of Doppler spectral analysis is also considered.

Transabdominal versus endovaginal pelvic sonography: prospective study.

Transabdominal and endovaginal pelvic sonograms were obtained in 108 nonpregnant patients referred for pelvic sonography. The studies were independently obtained by two radiologists and interpreted on the basis of identical clinical information. The sonograms were then compared for anatomic detail and abnormalities. A determination was made about which examination, if either, was superior. Follow-up was performed through a review of the medical records and follow-up studies. Overall, the endovaginal study was judged superior in 65 cases (60.2%), equal in 39 (36.1%), and inferior in four (3.7%). The authors conclude that the endovaginal examination can effectively replace the transabdominal examination as the initial approach for routine pelvic sonography.

Transvaginal saline hysterosonography: characteristics distinguishing malignant and various benign conditions.

OBJECTIVE: The objective of this study is to establish criteria for distinguishing endometrial polyps, submucosal leiomyomas, endometrial hyperplasia, and endometrial carcinoma on saline hysterosonography. MATERIALS AND METHODS: Sixty-three saline hysterosonograms with histologic confirmation were retrospectively analyzed. We found 26 endometrial polyps, 16 submucosal leiomyomas, three endometrial hyperplasias, one abnormal endometrium associated with a sloughed polyp, one pseudopolyp, and three endometrial carcinomas; 15 sonograms revealed no abnormality. In two patients, sonography revealed both polyps and submucosal leiomyomas. The sonographic appearance of these abnormalities was analyzed to define criteria for their diagnosis. RESULTS: Twenty-five of 26 polyps were uniformly echogenic with smooth borders and either had a stalk or formed acute angles with underlying endometrium. Sixteen of 16 submucosal leiomyomas showed heterogeneous echogenicity; however, 13 were sessile and three were pedunculated. Endometrial hyperplasia was manifested by wall thickening in two patients and tiny polypoid excrescences in one patient. In all patients with endometrial carcinoma, the endometrial cavities were poorly distensible despite successful cervical os cannulation. All patients with abnormalities other than endometrial carcinoma had fully distensible uterine cavities. CONCLUSION: Malignant and various benign endometrial conditions may be accurately distinguished on saline hysterosonography. Uniformity of echogenicity distinguished all polyps from submucosal leiomyomas, but the angulation formed with the endometrial wall by the intracavitary mass did not distinguish all polyps from submucosal leiomyomas. Lack of distensibility of the endometrial canal is a potential sign of endometrial carcinoma.

Diagnosis of portal vein thrombosis: value of color Doppler imaging.

This study was undertaken to determine the accuracy of color Doppler imaging in the diagnosis of portal vein thrombosis. Two hundred fifteen patients were studied with color Doppler imaging to determine patency of the main portal vein. Sonographic findings were confirmed in 75 patients, aged 19 to 66 years. Correlation with angiography was obtained in 13 patients, and surgical correlation was obtained in the remaining 62. Nine patients had portal vein thrombosis on the basis of these gold standards. Sonograms were classified as showing either patency or thrombosis, depending on the ability to show color flow within the main portal vein. Agreement between sonography and angiography or surgery was found in 69 patients (61 patent, eight thrombosed). One patient with a patent portal vein at sonography was found to have a thrombosed vessel at surgery, whereas five patients without portal venous flow at sonography had patent vessels at angiography (one patient) or surgery (four patients). Overall sensitivity and specificity for detection of portal vein thrombosis were 89% and 92%, with an accuracy of 92%, a false-negative rate of 0.11, a negative predictive value of 0.98, and a positive predictive value of 0.62. We postulate that the majority of errors in our study occurred in vessels that, although patent, had only sluggish flow, which could not be resolved because of technical limitations. We conclude that color Doppler imaging is a valuable screening procedure for the assessment of portal vein patency. If the sonogram shows a patent portal vein, no further studies are required. However, a lack of demonstrable flow does not always indicate thrombosis, and other imaging studies should be performed for confirmation.

Endoluminal catheter-assisted transcervical US of the human embryo. Work in progress.

To enhance visualization of anatomic structures of the human embryo, the authors used a commercially available catheter-based ultrasound (US) transducer (12.5 MHz) introduced through the cervix and into the endometrial cavity of seven women about to undergo voluntary termination of first-trimester pregnancy. The authors term this technique endoluminal catheter-assisted transcervical (ELCAT) sonography. In none of the patients did the US catheter rupture the fluid-filled chorionic/amniotic cavity. The duration of pregnancy ranged from 5.2 to 10.0 menstrual weeks. The most prominent anatomic structures visualized were the heart and neural tube. As an investigational technique, ELCAT US can be used to image anatomic structures of the developing human embryo.

Budd-Chiari syndrome: treatment with percutaneous transhepatic recanalization and dilation.

The authors describe a child with Budd-Chiari syndrome secondary to membranous obstruction of the hepatic veins and a web in the inferior vena cava. Transhepatic catheter venography demonstrated the occlusion, which was recanalized and dilated percutaneously via a transhepatic approach. Hepatomegaly and ascites decreased promptly and the prothrombin time became normal.

Color Doppler imaging findings in patients with Budd-Chiari syndrome: correlation with venographic findings.

OBJECTIVE: This study was undertaken to evaluate color Doppler imaging findings in patients with Budd-Chiari syndrome and to compare these findings with results of venography. SUBJECTS AND METHODS: In a prospective study, 21 patients with proved Budd-Chiari syndrome had color Doppler imaging. Sonographic evaluations ware performed to detect appropriately directed flow in the hepatic veins, portal vein, and inferior vena cava. Intrahepatic collaterals were characterized when present. Results of color Doppler imaging were compared with those of angiography in 20 patients. Color Doppler images of the hepatic veins were also obtained in a reference group (20 control subjects, 20 patients with hepatomegaly, and 20 patients with cirrhosis). RESULTS: Color Doppler imaging showed abnormalities of anatomy or flow in one or more of the main hepatic veins in all 21 patients with Budd-Chiari syndrome. Commonly observed abnormalities were visualization of a hepatic vein on real-time sonograms that had no flow or retrograde flow on color Doppler sonograms (11 cases) and no visualization of part or all of a hepatic vein on either real-time or color Doppler sonograms (10 cases). When compared with venographic findings (16 patients), findings on color Doppler sonograms could be used to distinguish patent from occluded hepatic veins in all cases. In our reference group, real-time and color Doppler sonograms showed normal hepatic veins in all control subjects. Real-time sonograms clearly showed hepatic veins in 12 of 20 patients with hepatomegaly; color Doppler sonograms showed flow in the hepatic veins in all 20 of these patients. Among 20 patients with cirrhosis, real-time sonograms showed hepatic veins in only seven; color Doppler imaging confirmed patent veins in 17. Intrahepatic collaterals typical of Budd-Chiari syndrome were observed in 10 of 21 patients with the syndrome. The portal vein was assessed by using color Doppler imaging in all 21 patients with Budd-Chiari syndrome; portograms were available for comparison in 10 patients. Findings were consistent in eight; in two cases, the direction of flow was reversed on color Doppler sonograms compared with portograms. For the inferior vena cava, venographic and sonographic findings correlated in 16 of 20 cases. Color Doppler sonograms did not show a caval web in one patient. CONCLUSION: Abnormalities of the hepatic veins, portal veins, and inferior vena cava detected on color Doppler sonograms in patients with Budd-Chiari syndrome correlate well with findings on venograms.(ABSTRACT TRUNCATED AT 400 WORDS)

Evaluation of renal transplant dysfunction by duplex Doppler sonography: a prospective study and review of the literature.

A disconcertingly wide variation exists in the literature as to the accuracy of duplex Doppler sonography in the detection of acute renal transplant rejection. Sensitivities range from 9% to 76%. In an attempt to explain the disparity of results, we undertook a double-blind prospective study of the accuracy of duplex Doppler ultrasound in the detection of acute rejection in renal transplants. We scanned 49 consecutive patients with a total of 65 biopsies; 46 biopsies in 33 consecutive patients were included in our study. In our population, the prevalence of acute rejection was 61% (28/46). Using a resistive index (RI) cutoff of greater than 0.90 based on the main renal artery flow pattern, the sensitivity of our test was 43%, with a 67% specificity. The positive predictive value was 67%. Our results are contrasted and compared with the published data from other groups in a critical survey of the literature. We conclude that duplex Doppler sonography alone is inadequate to evaluate acute rejection in renal transplants.

Color Doppler imaging of portosystemic shunts.

This study was designed to investigate the utility of color Doppler sonography in the evaluation of portosystemic shunts. Thirty-one patients with a total of 32 shunts were imaged. The types of shunts examined included portacaval, five; mesocaval, eight; distal splenorenal (Warren), 14; and mesoatrial, five. Sonography was performed without knowledge of the status of the shunt, although the type of shunt was known before beginning the study. The sonographic studies were evaluated to determine their sensitivity and specificity on the basis of a prospective comparison with angiography or MR imaging (22 cases). The possible advantages of color Doppler over duplex Doppler sonography in evaluating portosystemic shunts were also investigated, as was the ability of color Doppler sonography to image specifically the shunt anastomoses. Color Doppler sonography successfully inferred shunt patency (17 cases) or thrombosis (five cases) in all 22 shunts for which correlative imaging was available (sensitivity = 100%, specificity = 100%). In comparing duplex with color Doppler sonography in all 32 shunts, the two techniques were almost equally effective in establishing patency in portacaval, mesocaval, and mesoatrial shunts. Duplex Doppler sonography, however, provided useful diagnostic information in only four of 14 splenorenal shunts. Color Doppler correctly inferred patency or thrombosis in all 14. Among all 32 shunts, the anastomosis was shown clearly by color Doppler in 23, probably in four, and not all in five. Our results suggest that color Doppler sonography is an excellent method for the evaluation of all varieties of surgically created portosystemic shunts. In particular, color Doppler sonography appears to be superior to duplex Doppler sonography in imaging splenorenal communications.

Duplex Doppler sonography in renal allografts: the significance of reversed flow in diastole.

This study was undertaken to assess the significance of diastolic flow reversal seen on duplex Doppler sonograms of patients with renal transplant dysfunction. Earlier studies have evaluated the causes of increased vascular resistance in renal transplants. None, however, have investigated specifically the subset of patients in whom impedance in the renal microcirculation has increased to the degree that retrograde arterial flow is present. In our series, 533 consecutive scans in 270 patients were reviewed. The patients were referred for evaluation of renal transplant dysfunction during a 25-month period. Doppler samples were obtained from main, segmental, and, when possible, arcuate arteries. An episode of reversed diastolic flow was identified in nine patients. Correlation was made with clinical, laboratory, histologic (biopsy in six patients, nephrectomy in three patients), and imaging studies (DTPA scintigraphy in seven patients, angiography in one patient). On the basis of histologic and nephrectomy results, we determined that among the nine patients, four had acute tubular necrosis, three had acute rejection, and two had renal vein thrombosis. One of these patients had both severe rejection and renal vein thrombosis. One additional patient had neither biopsy nor nephrectomy and was not included in the diagnostic groups listed here. Our study suggests that reversed diastolic flow is not specific for either acute rejection or acute tubular necrosis. Reversal of diastolic flow, however, is a poor prognostic sign; nephrectomy was imminent in three of the nine patients. Furthermore, two (22%) patients had renal vein thrombosis, whereas renal vein thrombosis was not found in any of the 261 patients without reversed diastolic flow. Duplex Doppler examinations with reversed diastolic flow should suggest renal vein thrombosis.

Cranial arteriovenous malformations in neonates: color Doppler imaging with angiographic correlation.

Five neonates with cranial arteriovenous malformations were studied with color Doppler sonography. Excellent correlation was found between sonography and subsequent angiography. In three patients with vein of Galen aneurysms, sonography showed a cystic structure with rapid or swirling flow. Careful adjustment of the color Doppler system was required to demonstrate flow in another patient with a dural arteriovenous malformation. An arteriovenous fistula in a fifth patient appeared as an area of increased flow. Arterial feeders and major draining veins were visualized in all five patients. Color Doppler imaging also was used to assess the effect of embolic or operative therapy in three of the patients. We conclude that color Doppler sonography is able reliably to characterize flow patterns in neonatal cranial arteriovenous malformations. Color Doppler imaging also is helpful in assessing flow after embolic or surgical therapy.