Intracranial blood flow: quantification with duplex Doppler and color Doppler flow US

The authors compared changes in cerebral blood flow (CBF), determined by means of injection of radiolabeled microspheres, with Doppler blood flow measurements obtained simultaneously in the middle (n = 9) and anterior cerebral arteries (n = 3) in 12 newborn lambs. Doppler estimates of blood flow and mean blood flow velocity correlated well with changes in CBF. However, with changes in mean blood flow velocity, the degree of change in CBF tended to be underestimated. The resistive index correlated well with perfusion pressure but correlated weakly with cerebrovascular resistance and poorly with changes in CBF. Doppler blood flow estimates and mean blood flow velocities correlate well with changes in CBF and allow significant improvement in accuracy over instantaneous velocity or pulsatility measurements alone. Determination of absolute blood flow remains difficult due to systolic and diastolic differences in vessel diameter and intrinsic error in true diameter measurement with currently available color flow technology.     

Renal blood flow in neonates: quantification with color flow and pulsed Doppler US.

Color flow and pulsed Doppler ultrasound measurements of renal artery blood flow were compared with cardiac output in 22 preterm and 19 full-term healthy neonates. Renal arteries were insonated 3-5 mm from the abdominal aorta at an angle of less than 15 degrees. Vessel diameter was estimated from color flow diameter. Total renal blood flow increased significantly (P less than .001) with advancing birth weight and gestational age, because of increased vessel diameter, but flow velocity did not. The mean (+/- 1 standard deviation) value for both right and left renal artery blood flow was 21 mL/min/kg +/- 5, and the mean proportion of cardiac output to the kidneys was 16.1% +/- 3.7. Seven preterm infants with a symptomatic patent ductus arteriosus had increased cardiac output values (444 mL/min/kg +/- 45) and reduced right (15 mL/min/kg +/- 7) and left (16 mL/min/kg +/- 7) renal artery blood flow, with 6.6% +/- 2.0 of cardiac output directed to the kidneys. These values normalized after closure of the ductus. This study provides normative data for renal artery blood flow in neonates during the first week of life.     

Measurement of aortic blood flow with MR imaging: comparative study with Doppler US

An innovative magnetic resonance imaging technique was applied to the measurement of blood flow in the abdominal aorta. The technique combines selective excitation and visualization from an orthogonal view. The distance that fluid has moved is directly visualized. The blood flow velocity at every 50 msec throughout the cardiac cycle was measured in a short time (about 4 minutes) using electrocardiographic gating and repeated excitations in each cycle. Measurements were compared with those obtained by Doppler ultrasound (US) as a reference. The pulsatile change of flow velocity in the cycle correlated well with the Doppler US recording. Two flow velocity indexes, peak flow velocity and the velocity integral, also showed good correlation (r = .98 for both). This method is applicable for clinical use and is useful for measurement of high flow rates, as found in arteries.     

Splanchnic arterial stenosis or occlusion: diagnosis at Doppler US

PURPOSE: To determine the diagnostic accuracy of Doppler ultrasonography (US) in the detection of high-grade stenosis or occlusion of the celiac artery (CA) and superior mesenteric artery (SMA) and validate the previously reported Doppler US criteria. MATERIALS AND METHODS: During a recent 36-month period, 82 patients were prospectively examined with Doppler US of the splanchnic arteries and with lateral abdominal aortography, regardless of their abdominal symptoms. The previously reported diagnostic criteria with the fasting peak systolic velocity measurement were prospectively used in all patients. The results of Doppler US were compared with those of lateral aortography. RESULTS: The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of Doppler US for the detection of 70% or greater CA stenosis or occlusion were 100%, 87%, 57%, 100%, and 89%, respectively; for 70% or greater SMA stenosis or occlusion, these values were 100%, 98%, 93%, 100%, and 99%, respectively. CONCLUSION: Owing to its high accuracy in the diagnosis of high-grade splanchnic arterial stenosis or occlusion, Doppler US can be used as a screening method to help detect CA or SMA stenosis or occlusion and can reduce the use of unnecessary, invasive angiography.     

Pulmonary arterial hypertension: noninvasive detection with phase-contrast MR imaging

PURPOSE: To retrospectively identify pulmonary arterial (PA) flow parameters measured with phase-contrast magnetic resonance (MR) imaging that allow noninvasive diagnosis of chronic PA hypertension (PAH). MATERIALS AND METHODS: The study was HIPAA compliant and was approved by the institutional review board; a waiver of informed consent was obtained. Fifty-nine patients (49 female patients; mean age, 46 years; range, 16-85 years) known to have or suspected of having PAH underwent breath-hold phase-contrast MR imaging and right-sided heart catheterization (RHC). The presence of PAH (mean pulmonary artery pressure [mPAP], >25 mm Hg) was confirmed in 42 patients. Parameters, including PA areas, PA strain, average velocity, peak velocity, acceleration time, and ejection time, were measured in each patient by investigators blinded to RHC results. These measurements were correlated with mPAP, systolic pulmonary artery pressure (sPAP), and pulmonary vascular resistance index (PVRI). The diagnostic ability of phase-contrast MR imaging to depict PAH was quantified. Statistical tests included Spearman rho coefficients, receiver operating characteristic curve analysis, and Bland-Altman plots. RESULTS: Results showed average velocity to have the best correlation with mPAP, sPAP, and PVRI (r = -0.73, -0.76, and -0.86, respectively; P < .001). Average velocity (cutoff value = 11.7 cm/sec) revealed PAH with a sensitivity of 92.9% (39 of 42) and a specificity of 82.4% (14 of 17). Sensitivity and specificity for the minimum PA area (cutoff value = 6.6 cm(2)) were 92.9% (39 of 42) and 88.2% (15 of 17), respectively. CONCLUSION: The average blood velocity throughout the cardiac cycle is strongly correlated with pulmonary pressures and resistance.     

Prostate: high-frequency Doppler US imaging for cancer detection

PURPOSE: To evaluate cancer detection with targeted biopsy of the prostate performed on the basis of high-frequency Doppler ultrasonographic (US) imaging findings versus cancer detection with a modified sextant biopsy approach with laterally directed cores. MATERIALS AND METHODS: Sixty-two patients were prospectively evaluated with gray-scale, color, and power Doppler transrectal US performed with patients in the lithotomy position. Gray-scale and Doppler findings within each sextant were rated on a five-point scale. Up to four targeted biopsy specimens were obtained from each patient on the basis of Doppler findings; this was followed by a modified sextant biopsy. Conditional logistic regression analysis was performed to compare the positive yields for targeted and sextant biopsy specimens. Clustered receiver operating characteristic analysis was performed to compare gray-scale, color, and power Doppler detection of cancer at sextant biopsy sites. RESULTS: Cancer was detected in 18 (29%) of 62 patients, including 11 patients in whom cancer was detected with both sextant and targeted biopsy, six in whom cancer was detected only with sextant biopsy, and one in whom cancer was detected only with targeted biopsy. The positive biopsy rate for targeted biopsy (24 [13%] of 185 cores) was slightly higher than that for sextant biopsy (36 [9.7%] of 372 cores; P =.1). The odds ratio for cancer detection with targeted versus sextant cores was 1.8 (95% CI: 0.9, 3.7). Receiver operating characteristic analysis demonstrated that overall identification of positive sextant biopsy sites was close to random chance for gray-scale (area under the curve, 0.53), color Doppler (area under the curve, 0.50), and power Doppler (area under the curve, 0.47) imaging. CONCLUSION: Targeted biopsy performed on the basis of high-frequency color or power Doppler findings will miss a substantial number of cancers detected with sextant biopsy.     

Quantified power Doppler US of tumor blood flow correlates with microscopic quantification of tumor blood vessels

P:URPOSE: To evaluate the ability of a quantified power Doppler ultrasonography (US) system to help quantitate differences in tumor vascularity after radiation therapy and administration of tumor necrosis factor (TNF). MATERIALS AND METHODS: Murine glioblastoma tumors were grown in the thighs of two sets of 25 mice each. Each mouse was assigned to one of four treatment groups: control (no treatment), radiation therapy, TNF therapy, or combination therapy (both radiation and TNF therapies). Mice were then evaluated with quantified power Doppler US, and a vascularity index (color area) was calculated for different tumor regions in each group. The tumors were then excised, and histologic evaluation was performed by using an immunofluorescence-tagged monoclonal antibody against blood vessel endothelium. The number of stained blood vessels per high-power field was correlated with the sonographically determined vascularity index. RESULTS: The color area of the total tumor decreased to 37% of that in the control group in mice treated with radiation therapy alone (P: =.02), 26% of that in the control group in mice treated with TNF alone (P: =.05), and 8% of that in the control group in those treated with both TNF and radiation (P: =.006). These results correlated well with the quantified results from immunofluorescent staining (r = 0.98). CONCLUSION: Quantified power Doppler US is a noninvasive method for the evaluation of tumor vascularity and blood flow.     

Human abdominal aorta: comparative measurements of blood flow with MR imaging and multigated Doppler US

Magnetic resonance (MR) imaging has proved to be a new alternative method for the noninvasive detection and quantification of blood flow in human vessels. By means of standard gradient echo sequences triggered with electrocardiography on a 1.5-T whole-body imaging system, the authors measured the flow-induced phase shift in the abdominal aorta of healthy volunteers. The instantaneous two-dimensional velocity profiles and the integrated flow rate were determined in intervals down to 21 msec throughout the cardiac cycle. The results were validated by means of comparative measurements with a multigated Doppler ultrasound instrument. The velocity values acquired with this instrument in one spatial dimension in the anteroposterior direction of the abdominal aorta agreed to a great extent with the temporal and spatial corresponding values recorded with MR imaging. The same high correlation between the two methods was found for the calculated instantaneous total blood flow.     

Superior mesenteric artery blood flow velocity and estimated volume flow: duplex Doppler US study of preterm and term neonates

To obtain information about intestinal hemodynamics of healthy neonates, the authors assessed velocity and volume of blood flow with duplex Doppler sonography in the superior mesenteric artery (SMA) in 91 stable preterm and term neonates. Blood flow velocity in the SMA and estimated volume blood flow increased linearly with gestational age and increasing body weight. The mean estimated volume blood flow (+/- standard deviation) was 43 mL/kg/min +/- 13 and did not depend on differences in body weight. The authors also assessed blood flow velocity in the SMA and volume blood flow in 18 infants with conditions that may affect blood supply to the bowel. Twelve infants who were small for gestational age appeared to have an abnormally low resistance of the vascular bed of the SMA during the 1st days of life, as compared with stable appropriate-for-gestational-age infants matched for gestational age. Three of six term neonates with cardiovascular abnormalities had left ventricular outflow obstruction and an abnormal blood flow velocity waveform of the SMA, suggesting a decrease in blood supply to the bowel. The results of this study may help in evaluations of intestinal perfusion in infants with abnormal conditions.     

Hepatoblastoma: detection of tumor vascularity with duplex Doppler US

The evaluation of pediatric abdominal masses commonly includes computed tomography, ultrasound (US), and, more recently, magnetic resonance imaging. A previous study suggested that duplex US is of use in further tissue characterization of hepatic lesions in adults. The authors describe the Doppler signals arising from hepatoblastomas in three infants. Peak systolic Doppler frequency shifts in the neoplasms of these three patients were all equal to or greater than 4 kHz, well above the normal range for hepatic arteries. Each neoplasm also exhibited antegrade diastolic flow. The detection of high Doppler frequency shifts associated with neovascularity may prove useful in future evaluation of pediatric hepatic masses.     

Doppler sonography of hepatic arterial blood flow velocity after percutaneous transhepatic portal vein embolization

OBJECTIVE: This study was conducted to elucidate the changes in hepatic arterial blood flow after portal vein embolization. SUBJECTS AND METHODS: We prospectively measured the flow velocity and resistive index of the common, right, and left hepatic arteries, using Doppler sonography, in 21 patients who underwent embolization of the right portal vein. The measurements were performed before and 1, 3, 5, 7, and 14 days after embolization. We assessed the changes in liver volume with a volumetric study using CT. RESULTS: After embolization, flow velocity in the common hepatic artery increased significantly (p < 0.0001). Flow velocity in the right hepatic artery also increased significantly (p < 0.0001), with a significant decrease in resistive index (p < 0.0001). The flow velocity and resistive index of the left hepatic artery were unchanged. The increase in flow velocity in the right hepatic artery significantly correlated with that in the common hepatic artery (r = 0.514, p < 0.05). The calculated volume of the embolized right hepatic lobe significantly (p < 0.0001) decreased, from 685 +/- 32 cm(3) before embolization to 568 +/- 28 cm(3) after embolization. The atrophy rate of the right hepatic lobe significantly correlated with the increase in flow velocity in the right hepatic artery (r = 0.700, p < 0.0005). CONCLUSION: Portal vein embolization induces an increase in hepatic arterial blood flow velocity in the embolized hepatic segments, resulting from an increase in common hepatic arterial flow, but not from a steal phenomenon due to decreased hepatic arterial blood flow in the nonembolized hepatic segments. This observation may be explained by the simple mechanical effect of interposing a slower flowing stream (portal flow) in the path of a faster flowing stream (arterial flow).