Ability to use duplex US to quantify internal carotid arterial stenoses: fact or fiction?

PURPOSE: To determine if duplex ultrasonography (US) can help predict the degree of internal carotid arterial (ICA) stenosis. MATERIALS AND METHODS: ICA peak systolic velocity (PSV) and the ratio of the PSV in the ICA to that in the ipsilateral common carotid artery (VICA/VCCA) were compared with the degree of arteriographically measured stenosis. ICAs were arteriographically subgrouped at 10% incremental levels of stenosis and broader ranges. Mean PSV, VICA/VCCA, and SDs were calculated for each category. Histograms showing the numbers of stenotic ICAs in subgroups and for vessels with stenoses of greater than or equal to or less than 70% narrowing were constructed. The number of vessels correctly subgrouped with typical Doppler US thresholds was calculated. RESULTS: Mean PSV and VICA/VCCA increased with stenosis level (P < .01); SDs were wide. Histograms showed Doppler US values in the central groups across all disease levels. Histograms differentiating at least or less than 70% stenosis showed minimal overlap. PSV and VICA/VCCA helped classify, respectively, 185 and 181 of 204 vessels with stenoses of less than 50%, 15 and 21 of 46 vessels with stenoses of 50%-69%, and 73 and 67 of 84 vessels with stenoses of 70% or greater. When classifying stenoses as 69% or less or 70% or more, PSV and VICA/VCCA were correct in 90.6% and 90.3% of vessels. CONCLUSION: Doppler US is excellent for classifying stenoses as above or below a single degree of severity but does not function well in stenosis subclassification.

Benign versus malignant solid breast masses: US differentiation.

PURPOSE: To investigate the general applicability and interobserver variability of ultrasonographic (US) features in differentiating benign from malignant solid breast masses. MATERIALS AND METHODS: One hundred sixty-two consecutive solid masses with a tissue diagnosis were reviewed. Three radiologists reviewed the masses without knowledge of clinical history or histologic examination results. RESULTS: US features that most reliably characterize masses as benign were a round or oval shape (67 of 71 [94%] were benign), circumscribed margins (95 of 104 [91%] were benign), and a width-to-anteroposterior (AP) dimension ratio greater than 1.4 (82 of 92 [89%] were benign). Features that characterize masses as malignant included irregular shape (19 of 31 [61%] were malignant), microlobulated (four of six [67%] were malignant) or spiculated (two of three [67%] were malignant) margins, and width-to-AP dimension ratio of 1.4 or less (28 of 70 [40%] were malignant). If the three most reliable criteria had been strictly applied by each radiologist, the overall cancer biopsy yield would have increased (from 23% to 39%) by 16%. When US images and mammograms were available, the increase in biopsy yield contributed by US was not statistically significant (2%, P = .73). However, in independent reviews, one to three reviewers interpreted four carcinomas as benign at US. CONCLUSION: The data confirm that certain US features can help differentiate benign from malignant masses. However, practice and interpreter variability should be further explored before these criteria are generally applied to defer biopsy of solid masses.

Doppler sonographic parameters for detection of carotid stenosis: is there an optimum method for their selection?

OBJECTIVE: A wide range of Doppler threshold values for carotid stenosis is found in the literature. We undertook this study to compare methods of derivation and to determine if an optimum strategy of threshold selection exists for a high-risk population. MATERIALS AND METHODS: From the sonograms of all patent internal carotid arteries, peak systolic velocity in the internal carotid artery (ICA(PSV)) and the ratio of peak systolic velocity in the internal carotid artery to that of the common carotid artery (ICA(PSV)/ CCA(PSV)) were compared with the percentage of angiographically determined stenosis. Receiver operating characteristic curves were generated for levels of stenosis > or =60% and > or =70%. Doppler thresholds were chosen on the basis of maximum accuracy and on the basis of > or =90% sensitivity and specificity. Patients were then segregated into symptomatic and asymptomatic cohorts, and the above process was repeated. An effectiveness analysis was also conducted using various Doppler thresholds. Thresholds derived using these three methods were compared and optimal values chosen. RESULTS. Of 333 carotid arteries that fit inclusion criteria, 132 were found in asymptomatic patients and 201 in symptomatic patients. Maximum accuracy, > or =90% sensitivity and specificity, and effectiveness analysis each produced different ranges of thresholds. We chose final thresholds that maintained patient outcome profiles. For asymptomatic patients at the > or =60% stenosis level, thresholds were ICA(PSV) = 200 cm/sec and ICA(PSV)/CCA(PSV) = 3.0. For symptomatic patients with stenosis > or =70%, thresholds were ICA(PSV) = 175 cm/sec and ICA(PSV)/CCA(PSV) = 2.5. CONCLUSION: Considerable latitude exists in the choice of carotid Doppler thresholds. We propose a rational strategy for threshold selection based on a combination of three commonly used methods. Our observations indicate that it appears advisable to consider symptomatic and asymptomatic patients separately and to apply appropriately derived thresholds.

Effect of US contrast agents on spectral velocities: in vitro evaluation.

PURPOSE: To evaluate the effect of ultrasonographic (US) contrast agents on measurements of peak velocity with spectral Doppler US in stenotic and nonstenotic flow states. MATERIALS AND METHODS: Nonpulsatile flow was established in a flow phantom with 0%, 50%, 75%, and 90% stenoses. SH U 508A, perflenapent emulsion, and perfluorohexane emulsion were the contrast agents evaluated. Before and after administration of each contrast agent, two peak velocity measurements obtained proximal to, at the site of, and distal to the stenosis in each vessel model were averaged. The percentage difference in peak velocity after contrast agent administration was calculated for each site interrogated. The mean, SD, and coefficient of variation of the percentage difference in peak velocity were calculated. RESULTS: Percentage differences in peak velocity after contrast agent administration at different sample volume sites were not significantly different irrespective of the degree of stenosis or the contrast agent evaluated. CONCLUSION: The contrast agents evaluated do not produce a statistically significant increase in peak velocity. If this result is corroborated in clinical practice, contrast agents can be used without reevaluating existing Doppler US thresholds for stenosis.

Disclosure of results of sonographic examinations to patients by sonologists.

OBJECTIVE: The aim of this study was to assess if patients prefer to talk with a sonologist concerning the results of sonographic examinations. MATERIALS AND METHODS: The study involved outpatients who underwent diagnostic sonography. Technologists offered patients the chance to speak with a sonologist about the results of their sonograms. If requested, a sonologist reviewed the results, and if the study showed an abnormality, its significance was discussed. No treatment recommendations were offered. Patients then filled out a questionnaire. RESULTS: Of the 391 outpatients given the choice, 348 (89%) requested a consultation and 207 of those (60%) returned the completed questionnaire. Of the 207 patients completing the questionnaire, 94% preferred receiving the results from the sonologist rather than from their referring physician. CONCLUSION: We propose a revision of the traditional role of the office-based sonologist to one in which he or she will function as a consultant to both the patient and the patient's physician.

Significance of fetal intracardiac echogenic foci in relation to trisomy 21: a prospective sonographic study of high-risk pregnant women.

OBJECTIVE: The aim of the study was to determine if an association exists between intracardiac echogenic foci in the second-trimester fetus and trisomy 21. SUBJECTS AND METHODS: Over a 2-year period, targeted fetal sonography was performed for various indications in 1593 second-trimester high-risk pregnant women. Presence or absence of echogenic foci was recorded for each fetus. Amniocentesis for karyotype analysis was performed in 901 subjects immediately after sonography. The findings of these 901 subjects formed the basis of this report. RESULTS: Intracardiac echogenic foci were present in the left ventricle of 24 (3%) of the 901 fetuses. Three (13%) of these 24 fetuses had trisomy 21; no chromosomal abnormalities were found in the other 21 fetuses. Karyotype analysis revealed trisomy 21 in 14 (2%) of the remaining 877 fetuses who did not exhibit intracardiac echogenic foci. The sensitivity, specificity, positive predictive values, and negative predictive values for intracardiac echogenic foci in predicting trisomy 21 were 18%, 98%, 13%, and 98%, respectively. The association of intracardiac echogenic foci and trisomy 21 was significant (p < .009) by the two-tailed Fisher's exact test. CONCLUSION: In a high-risk obstetric population, the association between fetal intracardiac echogenic foci and trisomy 21 was statistically significant. Therefore, women carrying fetuses with intracardiac echogenic foci should be informed of the statistical association with trisomy 21.

Ability of a phase shift US contrast agent to improve imaging of the main renal arteries.

PURPOSE: To evaluate the ability of a phase shift contrast agent to improve Doppler sonographic imaging of the main renal arteries in cases of suspected renal artery stenosis. MATERIALS AND METHODS: In 25 patients in whom renal artery stenosis was suspected, baseline Doppler sonography was performed followed by two studies performed after blinded administration of contrast material or placebo (saline). Each kidney (n = 45) was evaluated for (a) visualization of the main renal artery on a scale of 0-4, (b) presence of accessory renal arteries, and (c) direct Doppler sonographic findings suggestive of renal artery stenosis. Correlative magnetic resonance angiography was performed in 24 patients, and angiograms were obtained in eight kidneys with stenosis at one or both imaging studies. RESULTS: Contrast enhancement was observed in 23 patients. Enhancement was 8-20 minutes. Renal artery visualization scores improved from a mean of 2.56 and 2.71 on baseline and noncontrast scans, respectively, to 3.69 after administration of contrast material. Contrast-enhanced images depicted seven kidneys with accessory renal arteries not seen at other studies. Two of eight cases of stenosis were seen only with contrast-enhanced sonography. CONCLUSION: Use of the phase shift contrast agent appears to enable a reduction in the number of equivocal findings of renal artery stenosis.

Clinical experience with sonographic contrast agents.

Early generations of sonographic contrast agents are beginning to reach the attention of the clinician. Research and development of ultrasound contrast agents is progressing at a rapid pace with several new agents approaching US Food and Drug Administration approval. Cardiac imaging has been affected by even the limited availability of contrast agents on the market today both with regard to diagnosis of shunts and chamber opacification, and most recently actual enhancement of the myocardium. Later generations of contrast are capable of providing consistent opacification of both peripheral veins and arteries, and should prove useful in a variety clinical applications. Thus far, it appears that longer vessel segments may be seen with contrast rather than without contrast, and that flow may be demonstrated in vessels which were not seen or thought to be occluded with conventional color imaging. Improved detection of arterial and venous collaterals and enhanced identification of run-off vessels is demonstrated with sonographic contrast agents. An improved ability to evaluate renal artery stenosis and subtotal occlusion of the carotid artery are specific advantages of using contrast as well. Several compounds are currently being tested that may allow routine parenchymal opacification. Ultrasound is the most commonly performed diagnostic imaging procedure; therefore, contrast agents have the potential to dramatically alter the practice of clinical medicine. This article reviews the current status of ultrasound contrast agents and speculates regarding the future applications of these agents.