Quantitative 4D-Digital Subtraction Angiography to Assess Changes in Hepatic Arterial Flow during Transarterial Embolization: A Feasibility Study in a Swine Model

PurposeTo determine the feasibility of using time-resolved 3D-digital subtraction angiography (4D-DSA) for quantifying changes in hepatic arterial blood flow and velocity during transarterial embolization.Materials and MethodsHepatic arteriography and selective transarterial embolization were performed in 4 female domestic swine (mean weight, 54 kg) using 100–300-μm microspheres. Conventional 2D and 4D-DSA were performed before, during, and after each embolization. From the 4D-DSA reconstructions, blood flow and velocity values were calculated for hepatic arterial branches using a pulsatility-based algorithm. 4D-DSA velocity values were compared to those measured using an intravascular Doppler wire with a linear regression analysis. Paired t-tests were used to compare data before and after embolization.ResultsThere was a weak-to-moderate but statistically significant correlation of flow velocities measured with 4D-DSA and the Doppler wire (r = 0.35, n = 39, P = .012). For vessels with high pulsatility, the correlation was higher (r = 0.64, n = 11, P = .034), and the relationship between 4D-DSA and the Doppler wire fit a linear model with a positive bias toward the Doppler wire (failed to reject at 95% confidence level, P = .208). 4D-DSA performed after partial embolization showed a reduction in velocity in the embolized hepatic arteries compared to pre-embolization (mean, 3.96 ± 0.74 vs 11.8 2± 2.15 cm/s, P = .006).ConclusionQuantitative 4D-DSA can depict changes in hepatic arterial blood velocity during transarterial embolization in a swine model. Further work is needed to optimize 4D-DSA acquisitions and to investigate its applicability in humans.     

Technical feasibility and performance studies of a Doppler guide wire for potential neuroendovascular applications.

PURPOSETo conduct technical feasibility and performance studies on a new Doppler-tipped, 0.014-inch micro-guide wire for potential neuroendovascular applications.METHODSIn vivo microcatheterizations of brachiocephalic arteries were performed in two swine using the 0.014-inch Doppler guide wire and a commonly used microcatheter. A standardized, bench-top method of evaluating basic mechanical properties of micro-guide wires was also used to compare the 0.014-inch Doppler guide wire with a commonly used micro-guide wire.RESULTSThe 0.014-inch Doppler guide wire had similar steerability, tractability, torque control, and distal tip flexibility to the commonly used micro-guide wire in the in vivo simulations. Frequent micro-guide wire exchanges were possible without loss of superselective positioning of the microcatheter. Bench-top testing showed the 0.014-inch Doppler guide wire to have comparable distal tip flexibility and stiffness to the commonly used micro-guide wire.CONCLUSIONThe comparable subjective and objective mechanical properties of the 0.014-inch Doppler guide wire to that of a commonly used micro-guide wire further establishes the possibility of clinical implementation of the device.     

Predictors of Thrombosis in Hepatic Vasculature during Microwave Tumor Ablation of an In Vivo Porcine Model

PurposeTo evaluate and model the risk of in vivo thrombosis in each hepatic vessel type during hepatic microwave ablation as a function of vessel diameter, velocity, and vessel-antenna spacing.Materials and MethodsA single microwave ablation antenna was inserted into a single porcine lobe (n = 15 total) adjacent to a hepatic artery, hepatic vein, or portal vein branch. Conventional ultrasound and Doppler ultrasound were used to measure the vessel diameter, blood flow velocity, and vessel-antenna spacing. A microwave ablation zone was created at 100 W for 5 minutes. Thrombus formation was evaluated on ultrasound performed immediately after the procedure. Logistic regression was used to evaluate the predictive value of vessel diameter, blood flow velocity, and vessel-antenna spacing on vascular thrombosis.ResultsThrombosis was identified in 53% of portal veins, 13% of hepatic veins, and 0% of hepatic arteries. The average peak blood flow rate of the hepatic artery was significantly greater than the average peak blood flow rate of the hepatic vein and portal vein. Peak blood flow velocity < 12.45 cm/s, vessel diameter < 5.10 mm, and vessel-antenna spacing < 3.75 mm were strong predictors of hepatic vein thrombosis. However, these individual factors were not predictive of the more common portal vein thrombosis.ConclusionsHepatic arteries do not appear to be at risk for thrombosis during microwave ablation procedures. Portal vein thrombosis was more common than hepatic vein thrombosis during microwave ablation treatments but was not as predictable based on vessel diameter, flow velocity, or vessel-antenna spacing alone.     

MR flow mapping in coronary artery bypass grafts: a validation study with Doppler flow measurements.

PURPOSE: To validate fast magnetic resonance (MR) flow mapping with intravascular Doppler flow measurements in vitro and in patients with nonstenotic and stenotic coronary artery bypass grafts. MATERIALS AND METHODS: MR and Doppler flow measurements were performed in a small-diameter flow phantom with physiologic flow conditions and at baseline and during adenosine stress in 27 grafts in 23 patients, who were scheduled for cardiac catheterization. At invasive analysis, the grafts were divided into those with stenosis of less than 50% (nonstenotic) and those with stenosis greater than or equal to 50% (stenotic). In vitro velocity values and velocity values in nonstenotic and stenotic grafts were compared with linear regression analysis, and the in vitro interstudy variability was determined. RESULTS: Excellent correlations in average peak velocity (r = 0.99, P <.001) and diastolic peak velocity (r = 0.99, P <.001) were demonstrated in vitro between MR and Doppler flow measurements, with less than 5% interstudy variability. MR and Doppler flow measurements revealed good correlations in peak velocity and velocity reserve both in nonstenotic (n = 20) (average peak velocity: r = 0.81, P <.001; diastolic peak velocity: r = 0.83, P <.001; velocity reserve: r = 0.56, P =.010) and stenotic (n = 7) (average peak velocity: r = 0.83, P <.001; diastolic peak velocity: r = 0.78, P =.001; velocity reserve: r = 0.70, P =.078) grafts. CONCLUSION: Fast MR flow mapping provides noninvasive measures of peak velocity and velocity reserve, which closely correlate with Doppler values both in vitro and in nonstenotic and stenotic grafts.     

Assessment of coronary flow reserve with fast cine phase contrast magnetic resonance imaging: comparison with measurement by Doppler guide wire.

Fast cine phase contrast magnetic resonance imaging (fast cine phase contrast MRI) can measure phasic coronary flow velocity in humans. The purpose of this study was to compare the coronary flow velocity reserves measured by MR IMAGING with those obtained by Doppler guide wire. Nineteen patients with ischemic or valvular heart disease were studied. Fast cine phase contrast MR images of the left anterior descending (LAD) artery were acquired during breath-hold time in the basal state and after administration of dipyridamole. Flow velocity in the LAD artery was also measured with Doppler guide wire before and after venous injection of dipyridamole in all subjects. Flow velocity in the coronary artery measured with MR IMAGING in the basal state (12.5 +/- 4.9 cm/sec) was significantly lower than that obtained with Doppler guide wire (32.4 +/- 12.1 cm/sec, P < 0.01). However, MR assessments of coronary flow velocity reserve showed a good linear correlation with those measured by Doppler guide wire (r = 0.91). In conclusion, fast cine phase contrast MR imaging is a useful technique, which can provide a noninvasive assessment of flow reserve ratios in patients with coronary artery disease. J. Magn. Reson. Imaging 1999;10:563-568.     

Altered hepatic hemodynamics caused by temporary occlusion of the right hepatic vein: evaluation with Doppler US in 14 patients

PURPOSE: To evaluate with Doppler ultrasonography (US) the altered hepatic hemodynamics caused by temporary occlusion of the right hepatic vein. MATERIALS AND METHODS: The study group consisted of 14 patients being considered for hepatic arterial infusion or transarterial embolization. In all patients, maximum peak velocity of the blood flow in the right portal vein was measured with Doppler US before and during the occlusion of the right hepatic vein. In 13 patients, color Doppler US was performed to evaluate Doppler signal in the portal venous branch in the occluded area before and during occlusion. Average peak velocity in the right hepatic artery in eight patients was measured by using a transducer-tipped guide wire before and during occlusion. RESULTS: Maximum peak velocity of the right portal vein significantly decreased with occlusion (P <.01). Hepatic venous occlusion changed the Doppler signal in the portal venous branch in the occluded area from hepatopetal to no signal in 10 patients; to weakened hepatopetal in two; and to hepatofugal in one. Average peak velocity of the right hepatic artery showed a decrease or plateau for 15-30 seconds after the start of occlusion and then a rapid increase to reach a plateau at around 75-90 seconds, with 1.5-2 times as much velocity as that before occlusion. CONCLUSION: Increase in hepatic arterial velocity is accompanied by a decrease in the portal velocity with temporary occlusion of the right hepatic vein; the expected increased drainage through the portal vein was almost undetectable.     

Endovascular Doppler guide wire in renal arteries. Correlation with angiography in 20 patients.

RATIONALE AND OBJECTIVES: To evaluate the feasibility of endovascular Doppler recording in renal arteries and to compare the reliability of Doppler parameters for detection of renal artery stenosis. METHODS: The authors examined 36 renal arteries in 20 patients with a 0.018" endovascular flow wire. Peak systolic velocity and the renal artery-to-aortic peak were measured in the main renal artery. From intrarenal waveforms, acceleration, acceleration time, and the renal resistive index were obtained. Spectral analysis with consensus scoring of early systolic peak was also performed. RESULTS: Twelve significantly stenosed renal arteries and 26 normal renal arteries were examined with the Doppler guide wire, without complications. Peak systolic velocity was the only parameter significantly different in renal artery stenosis (P = 0.037). Peak systolic velocity also differed significantly between hypertensive and normotensive patients. Tardus parvus was specific for severe renal artery stenosis. CONCLUSIONS: Endovascular Doppler is a safe and accurate method for the determination of velocity measurements and may be useful during percutaneous renal artery revascularization.     

Blood flow in major cerebral arteries measured by phase-contrast cine MR.

PURPOSETo measure mean blood flow in individual cerebral arteries (carotid, basilar, anterior cerebral, middle cerebral, and posterior cerebral) using a cine phase contrast MR pulse sequence.METHODSTen healthy volunteers (22 to 38 years of age) were studied. The cine phase-contrast section was positioned perpendicular to the vessel of interest using oblique scanning planes. This pulse sequence used a velocity encoding range of 60 to 250 cm/sec. From the velocity and area measurements on the cine images, mean blood flow was calculated in milliliters per minute and milliliters per cardiac cycle. In the same subjects, transcranial Doppler measurements of blood velocity in these same vessels were also obtained.RESULTSThere was no difference in blood flow in the paired cerebral arteries. Carotid arteries had mean blood flow in the range of 4.8 +/- 0.4 ml/cycle, the basilar artery 2.4 +/- 0.2 ml/cycle, the middle cerebral artery 1.8 +/- 0.2 ml/cycle, the distal anterior cerebral artery 0.6 +/- 0.1 ml/cycle, and the posterior cerebral artery 0.8 +/- 0.1 ml/cycle. Overall, there was poor correlation between MR-measured and transcranial Doppler-measured peak velocity.CONCLUSIONAlthough careful attention to technical detail is required, mean blood flow measurements in individual cerebral vessels is feasible using a cine phase-contrast MR pulse sequence.     

横窦血液流量MR测量方法的比较研究

目的 通过与电影相位对比（PC）法和超声的比较，评价二维（2D）PC法测量横窦血液流速和流量的准确性。方法 （1）志愿者8例，共计测量12个横窦，在每个横窦相同层面上分别采用2DPC法和电影PC法进行血流信号面积，血液流速和流量测量，测量结果用配对t检验进行统计分析。（2）需要开颅手术患者5例。共计6个横窦，术前采用2DPC方法对横窦血液流速进行测量，术中暴露横窦以后，用TCD探测血液流速，测量结果采用相关回归分析。结果 统计结果表明：2DPC法和电影PC法测得的横窦血流信号面积（t=-1.106,P=0.293)。流速（t=0.262,P=0.798)和流量（t=0.439,P=0.669)均无显著性差异，2DPC测得的流速与TCD测得的流速相关性良好（y^=1.303x 0.62,r^2=0.88)。结论 2DPC法是测量横窦血液流量简便实用的方法。     

Accurate measurement of pulsatile flow velocity in a small tube phantom: comparison of phase-contrast cine magnetic resonance imaging and intraluminal Doppler guidewire

Purpose

We compared the accuracy of magnetic resonance imaging (MRI) measurements of pulsatile flow velocity in a small tube phantom using different spatial factors versus those obtained by intraluminal Doppler guidewire examination (as reference).

Materials and methods

We generated pulsatile flow velocities averaging about 20–290 cm/sec in a tube of 4 mm diameter; we performed phase-contrast cine MRI on pixels measuring 1.00²–2.50² mm². We quantified spatial peak flow velocities of a single pixel and a cluster of five pixels and spatial mean velocities within regions of interest enclosing the entire lumen in the phantom’s cross-section. Finally, we compared the measurements of temporally mean and maximum flow velocity with the Doppler measurements.

Results

Linear correlation was excellent between both measurements of spatial peak flow velocities in one pixel. The highest spatial resolution using spatial peak flow velocities of a single pixel allowed the most accurate MRI measurements of both temporally mean and maximum pulsatile flow velocity (r = 0.97 and 0.99, respectively: MRI measurement = 0.95x + 8.9 and 0.88x + 24.0 cm/s, respectively). Otherwise, MRI measurements were significantly underestimated at lower spatial resolutions.

Conclusion

High spatial resolution allowed accurate MRI measurement of temporally mean and maximum pulsatile flow velocity at spatial peak velocities of one pixel.     

Transcranial Doppler sonographic monitoring during cerebral aneurysm embolization: a preliminary report.

BACKGROUND AND PURPOSEThe wide application of embolization in the treatment of aneurysms has created the need for an intraprocedural means to anticipate a poor outcome by monitoring hemodynamic changes in the brain.METHODSTranscranial Doppler sonography was used to monitor flow velocity in the middle cerebral artery (MCA) in 23 patients undergoing embolization with Guglielmi detachable coils (GDCs) of either incidental or symptomatic intracranial aneurysms. Sonographic values were recorded from the ipsilateral MCA at the beginning, middle, and end of the interventional procedure and 24 hours afterward.RESULTSNo complications occurred in 15 patients. In these cases, sonography showed an average decrease in MCA flow velocity of 2.7% after GDC application, returning to baseline at the end of treatment and then increasing by about 17% 24 hours later. In four patients with vasospasm on posttreatment angiograms, MCA flow velocity increased to values higher than 120 cm/s after GDC application, returning to baseline after 24 hours. In four patients with ischemic complications (two transient ischemic attacks, one stroke, one vascular death), MCA flow velocity decreased more than 30% and did not return to preoperative values within 24 hours.CONCLUSIONThe application of transcranial Doppler sonographic monitoring during endovascular treatment may help to identify patients at risk for posttreatment cerebral ischemia.     

Parametric imaging of cerebral vascular reserve

We report the reproducibility and response to change in end-tidal CO₂ of a new method of quantifying regional mean cerebral transit time (MCTT) compared with the reproducibility and CO₂ reactivity of middle cerebral artery (MCA) blood flow velocities measured using transcranial Doppler ultrasound. Within the range of end-tidal CO₂ which could be achieved in conscious subjects breathing spontaneously, hemispheric MCTT, peak MCA velocity and mean MCA velocity showed a linear relationship with end-tidal CO₂. After correction to a standardised end-tidal CO₂, the coefficients of variation were 5.7% for hemispheric MCTT, 6.3% for peak MCA velocity and 6.8% for mean MCA velocity. Under the conditions of this study, MCA blood flow velocity was proportional to the reciprocal of MCTT, which in turn represents the ratio of blood flow to blood volume. Although the two methods appear to provide similar information, measurement of MCTT is quicker to perform, is less observer-dependent, provides regional information, uses conventional equipment present in most nuclear medicine departments and is less subject to problems associated with patient movement. Offprint requests to: M.V. Merrick     

胎儿肾血管彩色多普勒检测

本文报道了应用彩色多普勒超声显像仪对４６例胎儿肾动脉血流的测定结果。胎儿肾动脉血流在发育不同阶段呈规律的变化：Ｖｓ、Ｖｄ、Ｔａｍｘ、ＣＴＩ随胎龄的增加呈递增趋势，Ｖｓ／Ｖｄ随胎龄增加呈递减趋势，Ｖｓ反映肾动脉血流量，Ｖｄ反映肾动脉血管阻力，ＰＩ、ＲＩ在各胎龄期无明显差异。结果表明：应用多普勒超声检测胎儿肾动脉血流来评价胎儿周围循环状态，预测胎儿的发育情况是可行的，并且是可靠的。     

Parámetros hemodinámicos cerebrales,determinados mediante Doppler transcraneal,en un grupo de voluntarios sanos a 2.850 metros de altura

BackgroundTranscranial Doppler ultrasound (TDU) is useful in cerebrovascular patients. TDU findings are operator-dependent; they can also be influenced by anatomical and physiological variables as well as by the altitude at which the study is done.ObjectiveTo report the cerebral hemodynamic parameters measured by TDU in subjects who live in Quito, Ecuador (altitude 2850 meters).Material and methodsWe recruited 47 volunteers with no history or clinical evidence of stroke, hypertension, metabolic disorders, or hematologic disorders; 2 patients were excluded because they did not have a viable cranial window for TDU study. Thus, we recorded mean cerebral blood flow velocity, peak systolic flow velocity, end-diastolic flow velocity, and pulsatility indices in 45 patients (28 (62.2%) women; mean age, 35.9 years). We recorded patients’ age, sex, and hematocrit. We analyzed cerebrovascular hemodynamic parameters by sex and age group.ResultsNo significant differences between hemispheres were observed in mean flow velocities, except in the anterior cerebral arteries with right predominance. Flow velocities were higher in women and in the youngest age group. No significant differences in the pulsatility indices were found between sexes or between age groups. The flow velocities in this series are lower than those reported for other series.ConclusionsThe hemodynamic parameters in this series are lower than in other series and are influenced by the altitude, age, and sex.     

血管内多普勒超声对Budd—Chiari综合征介入治疗前后血流动力学变化的评价

目的 :检测Budd Chiari综合征 (BCS)患者血流动力学的变化及对BCS患者PTA术后即刻的效果进行评价。材料和方法 :使用血管内多普勒导丝对 2 7例BCS患者下腔静脉 /肝静脉 (IVC/HV)介入治疗 (PTA)前后血流速度、血流量和压力的变化进行测定及比较。结果 :IVC和HV病变远心端PTA后较PTA前的平均峰值流速、最大峰值流速及血流量显著增加 ,而压力显著下降。结论 :PTA有利于BCS患者IVC/HV血流动力学的恢复 ;血流动力学指标可作为BCS在PTA后IVC/HV再通的依据之一。血流速度的变化可以作为判定PTA治疗终点的可靠指标之一。     

The Doppler guide wire: clinical applications in neuroendovascular treatment

The application of Doppler-tipped guide wires to measure blood flow velocity in coronary and peripheral arteries has been described previously as a valuable means of functional assessment in interventional cardiological procedures. In animal studies intravascular Doppler has been used in the cerebrovascular system, and this appears to be an important field of application for this new technique. We used intravascular haemodynamic monitoring by the Doppler guide wire during neuroendovascular procedures in patients with different cerebrovascular diseases and evaluated the clinical feasibility of the method. We found it a safe technique which complements morphological angiographic information with valuable functional data. Further studies may be expected to demonstrate the relation of flow parameters to clinical outcome. Received: 16 January 1996 Accepted: 30 January 1996     

Novel doppler assessment of intracoronary volumetric flow reserve: validation against PET in patients with or without flow-dependent vasodilation.

Volumetric blood flow (Q) determination requires simultaneous assessment of mean blood flow velocity and vessel cross-sectional area. At present, no method provides both values. Intracoronary Doppler-based assessment of coronary flow velocity reserve (CFVR) relies on average peak velocity (APV). Because this does not account for changes in velocity profile or vessel area usually occurring with flow-dependent vasodilation, results can be misleading. The aim of this clinical study was to validate against the current gold standard (measurement of myocardial perfusion reserve [MPR] by PET) a new, Doppler-based method for calculating coronary Q and coronary flow reserve (CFR). METHODS: Doppler-based intracoronary Q was measured with a proprietary guidewire device in a nonstenotic coronary artery at baseline and during adenosine-induced hyperemic flow (140 mug/kg/min intravenously during 7 min). Three gate positions were assessed, of which 2 were lying within the vessel and 1 was intersecting the vessel. The zeroth (M(0)) and the first (M(1)) Doppler moments of the intersecting gate were used to calculate mean blood flow velocity (M(1)/M(0)) and vessel area (M(0)), and M(0) of the 2 proximal gates was used to correct for scattering and attenuation. CFR was calculated as hyperemic/resting flow with Q and compared with APV-derived CFVR and with the corresponding segmental MPR obtained with (15)O-labeled water and PET. RESULTS: Q (CFR, 2.60 +/- 1.07) correlated well with PET (MPR, 2.58 +/- 1.11) (r = 0.832, P < 0.005; Bland-Altman limits, -1.42 to 1.09), whereas CFVR did not (r = 0.09, P = not statistically significant; Bland-Altman limits, -3.36 to 2.24). However, in vessels without dilation, there was no difference between CFR, CFVR, and MPR. CONCLUSION: This procedure for intracoronary Q measurement using the proprietary Doppler guidewire system, which accounts for both changes in flow profile and changes in vessel area, allows invasive, accurate assessment of CFR even in the presence of flow-dependent vasodilation.     

冠状动脉内多普勒超声研究冠状动脉血流速度

目的:评价冠状动脉内多普勒超声测量冠脉血流速度的应用价值。材料和方法:利用冠状动脉内多普勒血流钢丝(FloWire) 测量21 例冠状动脉狭窄患者和12 例正常冠状动脉的血流速度。结果:左前降支冠脉狭窄远端的平均最大血流速度(APV) 、舒张期最大血流速度(DPV) 和舒张期与收缩期流速比值(DSVR) 均显著低于正常组测值。结论:应用冠脉内多普勒超声技术可评价正常和冠脉狭窄病变患者的冠脉血流速度,这为定量研究冠脉血流动力学提供了新方法。     

Pulsatile flow index for qualitative measurements of blood flow with duplex ultrasound. An experimental study

We determined the accuracy of Doppler blood flow measurements in an experimental investigation using a tissue-simulating phantom, pulsatile flow pumps and heparinized blood. A new index for qualitative assessment of blood flow, the pulsed flow index (PFI) is described. The PFI takes advantage of the area under the flow velocity curve between the true zero line and the diastolic baseline. Under conditions of continuous flow, the PFI ranged from 0.82 to 0.94 (mean value 0.90). The PFI was found to be relatively independent of the transducer/vessel angle (+/- 8%) and the inter/intra-operator variation was small (+/- 7.5%, or +/- 7%, respectively).     

Doppler Flow Wire Evaluation of Renal Blood Flow Reserve in Hypertensive Patients with Normal Renal Arteries

Purpose: To study the vasomotor responses of the renal microcirculation in patients with essential hypertension. Methods: We studied the reactivity of the renal microcirculation to papaverine, with intraarterial Doppler and quantitative arteriography, in 34 renal arteries of 19 hypertensive patients without significant renal artery stenosis. Isosorbide dinitrate was given to maximally dilate proximal renal arteries. APV (average peak blood flow velocity) was used as an index of renal blood flow. Results: Kidneys could be divided into two distinct subgroups based on their response to papaverine. An increase in APV of up to 55% occurred in 21 kidneys, an increase > 55% in 13 kidneys. Within each group the values were normally distributed. Both baseline APV and the effect of papaverine on mean velocity differed significantly between groups. Conclusion: There seems to be a subgroup of patients with essential hypertension that has an impaired reactivity to papaverine, consistent with a functional impairment of the renal microcirculation. Further studies are required to determine whether this abnormality contributes to or results from elevated blood pressure.