Measurement Of Blood Flow Volume Research Articles

Colour velocity flow measurement: In vitro validation and application to human carotid arteries

Ultrasound measurement of volume blood flow is potentially useful for many clinical situations, yet practical implementation and use are restricted by the many instrumentation and blood flow limitations that can arise. Colour velocity imaging offers a number of theoretical advantages over methods based on duplex imaging. We evaluated a colour velocity flow measurement system (CVI-Q, Philips) both in a flow phantom and in vivo in the extracranial carotid arteries of normal volunteers. Over a range of constant (50–1200 ml/min) and pulsatile (92–366 ml/min) flows and using both steered and unsteered beams with beam angles of 30° and 40°, errors usually within 5% were obtained for constant flow and within 10% for pulsatile flow. However, with a beam angle of 70°, higher errors of 20% were obtained for pulsatile flow. The reproducibility of flow measurements made using both anterior and posterior-lateral scanning approaches was determined in the common (CCA), internal (ICA) and external carotid (ECA) arteries of 18 volunteers. A greater reproducibility was found using the posterior-lateral approach (CCA 6.27%; ICA 9.8%), and mean (SD) flow values were 376 ml/min in the CCA and 255 ml/min in the ICA. The ratio of (ICA + ECA) CCA flow calculated for each subject individually was mean (SD) 0.95 (0.11). Insonation from an anterior approach resulted in lower reproducibility and lower flow values. In conclusion, colour flow velocity imaging allows repeatable reproducible measurements of CCA and ICA flow, but results are optimal if a posterior-lateral scanning approach is used.

Validation of a new transit time ultrasound flowmeter in man

To validate the new CardioMed CM 4000 transit time ultrasound apparatus for intraoperative measurement of volume blood flow in vivo in man. Open, prospective series. Thirteen patients undergoing in situ saphenous vein grafting for chronic critical leg ischaemia and 12 patients subjected to myocardial revascularisation with the internal thoracic artery as coronary bypass. During operations, volume blood flows were measured simultaneously by exsanguination from the cut distal end of the in situ saphenous vein graft or the internal thoracic artery and by the transit time flowmeter equipment. In addition, the feasibility to detect arteriovenous fistula during in situ saphenous vein grafting was examined. Within the examined blood flow range, the volume blood flow determined by the transit time method corresponded to the directly measured blood flow. For in situ saphenous vein grafts: y = -2.4 + 0.95.x (r = 0.99; 35 measurements in 13 patients), and for internal thoracic artery grafts: y = -9.6 + 1.1.x (r = 0.99; 21 measurements in 12 patients), where y is blood flow determined by transit time, and x is directly measured blood flow by exsanguination (r = correlation coefficient) as calculated by the least squares regression method. Fistula detection was easy and swift. The transit time apparatus was simple to use during intraoperative settings and gave fast, precise measurements of volume blood flow.

Quantitative blood flow measurements with cine phase-contrast MR imaging of subjects at rest and after exercise to assess peripheral vascular disease.

The purpose of this study was to determine whether cine phase-contrast MR volume flow measurements can identify patients with peripheral vascular disease. We performed MR measurements of volume blood flow in the popliteal artery of subjects at rest and after 5 min of plantar flexion exercise in 10 volunteers (mean age, 28 years old), in five patients suspected of having peripheral vascular disease (mean age, 58 years old), and in five other volunteers of a similar age (mean age, 57 years old). Volume blood flow at rest was similar in volunteers and in patients. Four patients who had abnormal ankle-brachial indexes had lower flow increases after exercise (2.6-fold) compared with the five older normal volunteers (4.8-fold; p < .03, t test). These flow increases correlated well with ankle-brachial indexes: r = .97. The four patients with abnormal ankle-brachial indexes had monophasic resting waveforms, whereas all other subjects had triphasic waveforms. MR volume blood flow measurement may aid in evaluating peripheral vascular disease. Studies of larger patient groups will be necessary.

Color duplex measurement of cerebral blood flow volume: intra- and interobserver reproducibility and habituation to serial measurements in normal subjects.

Color duplex flowmetry of internal carotid and vertebral arteries permits estimation of intravascular flow volumes and global cerebral blood flow volume (CBFV) by summing the flow volumes measured in each of the four extracranial vessels. Intravascular flow volumes were calculated as the product of angle-corrected time-averaged flow velocity and the cross-sectional area of the vessel. The reliability of this new method was tested in a prospective, intra- and interdiane, intra- and interobserver reproducibility study of 32 healthy subjects aged 7-57 years. In each subject, CBFV was tested by each observer twice on day 1 and once on day 2 in consecutive recordings. In each artery, both examiners found closely similar mean intravascular flow volumes. Intradiane interobserver reproducibility of CBFV was high on both days (correlation coefficient, CC, 0.90 and 0.85, p < or = 0.0001; coefficient of variance, CV, 10.0 and 10.4%, respectively), as was the interdiane comparison (CC = 0.81, p < or = 0.0001; CV < or = 13.3%). Intraobserver reproducibility was even higher. On both days, there was a progressive decrease in CBFV from each subject's first to the last examination within a 1-h examination period (day 1: 717 +/- 150 ml/min to 690 +/- 120 ml/min; difference, p < or = 0.05; day 2: 700 +/- 120 ml/min to 665 +/- 126 ml/min; difference, p < or = 0.01). This habituation effect was more pronounced in subjects with high initial CBFV. Reproducibility of CBFV is comparable to that of mean CBF measurements with 133Xe inhalation and H2 15(O) positron emission tomography techniques reported by other groups. This method makes serial bedside-monitoring of CBFV feasible without posing the risks of radiation exposure.

An alternative to radioactive microspheres for measuring regional myocardial blood flow, part 2: Laser-doppler perfusion monitor

To compare measurements of regional myocardial blood flow volume between microsphere measurement of regional flow (0.5- to 2- g tissue sampling) and a potential alternative measure, local flow (1 mm3) in the microcirculation measured by laser-Doppler perfusion monitor. Prospective, randomized, controlled. University research laboratory. Pigs. After anesthetization, in 5 pigs (25 to 30 kg), the left anterior descending coronary artery was isolated and its resting flow measured by a perivascular-Doppler flowmeter. Left ventricular pressure and first time derivative of left ventricular pressure were measured. The laser-Doppler probe needle (type N) (Model ALF-21, Transonic Systems, Inc, Ithaca, NY) was inserted 2 to 3 mm into the wall of the left ventricle, parallel to the coronary artery. All 5 pigs were subjected to 0 (control), 50% , 75%, and 100% constriction of the left anterior coronary artery. Measurements by radio-active microspheres correlated poorly with those by laser-Doppler and extremely poorly with those by perivascular Doppler flowmeter. For percent change from baseline in the constricted arterial zone, radioactive measurements correlated well with those by laser-Doppler but not those by Doppler flowmeter. Also, radioactive measurements of percent change in flow in the circumflex (nonconstricted) zone and laser-Doppler measurements in the constricted arterial zone did not correlate well. Laser-Doppler can be recommended for experimental research to monitor local flow. These measurements may relate to change in regional flow during normal perfusion and hypoperfusion. Before the laser-Doppler perfusion monitor can be used clinically, tissue trauma from the 0.55-mm needle needs to be evaluated.

Preoperative and postoperative evaluation of latissimus dorsi myocutaneous flap vascularization by color flow duplex scanning.

At the Plastic and Reconstructive Surgery Department of the University of Perugia, 104 patients have been examined by color flow duplex scanning in order to study latissimus dorsi vascular supply before and after surgical procedures. This noninvasive ultrasound technique provides a precise and accurate measurement of blood flow velocity (15 cm/s) and volume (27 ml/min) within the thoracodorsal artery, which represents the vascular pedicle of the flap, and it allows us to detect the exact location of the perforating branches with their cutaneous distribution. This preoperative evaluation, pointing out vascular pathologies that contraindicate use of the latissimus dorsi flap, can be considered a great help for the reconstructive surgeon in the choice of the most suitable operation, and it can surely lead to a significant decrease in postoperative graft failure rates.

In vivo validation of magnetic resonance blood volume flow measurements with limited spatial resolution in small vessels.

The accuracy of magnetic resonance phase contrast volume flow measurements in small blood vessels is expected to be smaller than in large vessels, because of partial volume effects at the vessel boundary. Accuracy was validated in the dog femoral artery, diameter 3.5 +/- 0.7 mm, using an ultrasonic transit-time flowmeter (TT). The number of pixels per vessel diameter (ND) ranged from 1.6 to 4.8. The vessel cross-section was determined using a threshold in the magnitude image. Between the two methods the correlation coefficient was 0.95 (range 10-200 ml/min). The proportional difference (PD), (QTT-QMR)/1/2(QTT+QMR), was 0.8%, showing no systematic difference between the methods. The PDs standard deviation was 27%, and 19% for flow rates above 30 ml/min. Only a significant decrease of the PDs variance was found at the highest ND values, suggesting other sources of error than partial volume effects. It is concluded that with an ND value of about 3, accurate blood volume flow rates can be determined.

Activity of Crohn disease assessed by measurement of superior mesenteric artery flow with Doppler US.

To test the hypothesis that increased blood flow in the superior mesenteric artery (SMA) reflects disease activity in patients with Crohn disease. Duplex Doppler sonographic measurements of SMA blood flow volume were obtained in 10 patients with active Crohn disease, 10 patients with chronic inactive Crohn disease, and 10 healthy volunteers. Disease activity was determined with clinical and laboratory indicators. Interstudy reproducibility of repeated SMA flow volume measurements was good (r = .98). A marked increase in SMA flow volume was noted in patients with active disease compared with patients with inactive disease and healthy volunteers: 1,588 mL/min +/- 576 versus 288 mL/min +/- 113 and 417 mL/min +/- 147, respectively (P < .05 for both comparisons). Activity of Crohn disease causes a substantial increase in SMA flow volume. Measurement of SMA blood flow may be an important noninvasive, readily available, inexpensive tool that can be used to monitor Crohn disease objectively.

Validation of volume blood flow measurements using three-dimensional distance-concentration functions derived from digital x-ray angiograms.

The authors present phantom validation of a method for computing pulsatile flow waveforms in arterial vessels from high-frame-rate biplane x-ray angiograms. The three-dimensional course of a blood vessel is constructed from biplane digital x-ray angiograms. A parametric image of contrast mass versus time and true three-dimensional path length is generated. Adjacent contrast mass-distance profiles are matched to compute instantaneous velocity, which is multiplied by cross-sectional area to yield volume flow. An electromagnetic flowmeter was used to validate flow estimates in a phantom consisting of 150-mm tubes 3, 4, and 6 mm in diameter, orientated 15 degrees, 30 degrees, and 35 degrees to the imaging plane, with flow rates and waveforms expected in vivo. Mean and peak flows were accurate to within 9% and 10%, respectively, for velocities of less than 1 meter/second at a frame rate of 25 frames per second. A practical method for computing highly pulsatile flow waveforms in vivo in tortuous vessels is presented.

The relationship between blood flow and pulsatility index in the superior mesenteric artery at rest and during constrictor stimuli in normal subjects.

The relationships between superior mesenteric artery blood flow (SMABF) and pulsatility index (PI) measurement during rest (25 subjects) and stimuli constricting the SMA (16 subjects) have been studied in normal subjects. At rest and during constrictor stimuli, SMABF and PI were highly reproducible (r = 0.89, p < 0.01 for SMABF, and r = 0.97, p < 0.001 for PI) between two observers. There was significant correlation between changes in SMABF, PI, and SMA vascular resistance during the constrictor stimuli, except during head-up tilt when PI was unchanged. Both PI and SMABF measurements are reproducible and can be used to monitor physiological changes in suitable (18 of 25) subjects. PI measurement, although semiquantitative, by itself can also be used to monitor these changes. This may be also of importance in pathological situations such as intestinal ischemia, where measurement of volume blood flow may be less accurate due to irregularities of the vessel wall. PI measurement, however, ideally should not be used in studies involving postural change.

Magnetic resonance, a new method for measuring blood flow in hemodialysis fistulae

Blood flow through arteriovenous fistulae in patients undergoing hemodialysis needs to be within a certain range for optimal management. Magnetic resonance (MR) velocity mapping is a new modality that allows the noninvasive measurement of blood flow volume. This technique was applied in 13 patients with either a Brescia-Cimino shunt (N = 6) or a Polytetrafluoroethylene graft (Goretex, N = 7). Fistula flow volume measured by MR velocity mapping was 1386 +/- 411 ml/min (mean +/- SD, range 644 to 1921 ml/min). Interstudy reproducibility of MR velocity mapping was good (r = 0.94). Interstudy reproducibility of MR velocity mapping was good (r = 0.94). MR velocity mapping derived flow volumes showed good correlation with values obtained with an indicator dilution technique using Indocyanine Green (ICG) which was performed simultaneously in eight patients (r = 0.86). We conclude that MR velocity mapping is an accurate noninvasive method to quantify flow volume through arteriovenous fistulae in patients requiring hemodialysis.

Volume blood flow measurements with a transit time flowmeter: an in vivo and in vitro variability and validation study.

A transit time flowmeter, Transonic TC101 (Transonic Inc., USA) has been evaluated to study volume flow. Two flow probes, 4 and 6 mm, were used. The experiments were carried out in vivo on the carotid arteries (n = 16) in sheep and in vitro against a pre calibrated rotational pump. Exsanguination measurements, n = 32, were used for the calculation of the error of measurement in vivo. The error of measurement in vitro was calculated on 11 different flow rates from 0 to 150 ml min-1. The variability in vivo was evaluated using data from 10, 30 s measurement periods with a 30 s pause between measurements. The variability in vitro was evaluated at three flow rates (46, 78, and 113 ml min-1). Five 1-min measurements with a 1-min pause between measurements were made. The error of measurement in vivo was 12.05% and in vitro 5.50% (4 mm probe) and 14.90% (6 mm probe). In vivo the variability was between 1.1 and 4.4% and in vitro between 1.5 and 11.2%. The correlation coefficients between the flowmeter on the one hand and exsanguination and the rotational pump on the other were 0.99, 0.99 (4 mm probe) and 0.98 (6 mm probe). It is concluded that the flowmeter has a small variability and error of measurement both in vivo and in vitro.

Quantitative Measurements of Prostatic Blood Flow and Blood Volume by Positron Emission Tomography

Prostatic blood flow was measured with 15oxygen-water by positron emission tomography using a 1-compartment model. A dynamic study method was applied to 9 normal subjects, 6 with benign prostatic hypertrophy (BPH) and 11 with advanced stages C to D2 prostatic adenocarcinoma. Prostatic blood flow was 15.7 ± 7.5ml. per minute per 100gm. in normal controls, 17.7 ± 5.2ml. per minute per 100gm. in BPH patients and 29.4 ± 7.8ml. per minute per 100gm. in prostatic cancer patients. Prostatic blood flow negatively correlated well with age in the normal subjects. Prostatic blood volume was also estimated by the steady state method using 15oxygen-carbon monoxide. Prostatic blood volume was 8.1 ± 2.6% in normal controls, 8.9 ± 1.1% in BPH patients and 6.1 ± 2.1% in prostatic cancer patients. Blood flow in the prostatic cancer tissue was higher than that in the normal (p <0.001) or BPH (p <0.01) tissue. A significant difference in prostatic blood volume was also observed between BPH and cancer tissues (p <0.02).

Simultaneous cardio-cerebral ultrasonic measurement technique for assessing the interrelationship between cardiac and cerebral circulations in elderly subjects: A preliminary study

To assess the interrelationship between the cardiac and cerebral circulations, simultaneous measurements of cardiac output (CO) and common carotid blood flow volume (CCBFV) was performed by M-mode echocardiography of the left ventricle, and quantitative ultrasonic Doppler blood flowmetry of the common carotid artery. The subjects studied were 12 healthy persons living in a home for the elderly ranging in age from 62 to 99 years. These subjects were divided into two groups: those who were in their 90s (Group I, 5 females) with a mean age of 93.6 ± 3.5 years (mean ± SD), and those who were in their 60s to 80s (Group II,1 male and 6 females) with a mean age of 77.1 ± 8.1 years. The average CO in Group I was 2.85 ± 0.37 L/min, and 4.18 ± 0.52 L/min in Group II. The average CCBFV was 4.74 ± 0.64 dl/min in Group I, and 4.44 ± 1.01 dl/min in Group II. The ratio of CCBFV to CO was 16.6 ± 1.32% in Group I, and 10.6 ± 1.45% in group II. Good linear correlations of y = 1.44 x + 0.65 ( r = 0.82) in Group I and y = 1.58 x – 2.15 ( r = 0.81, p < 0.05) in Group II were observed between CO ( x) and CCBFV ( y). No such close correlations were observed between CCBFV and other indices of left ventricular function such as circumferential fiber shortening or fractional shortening of the diameter of the left ventricle ( r ≤ 0.56, p > 0.05). Thus the present study in healthy elderly subjects showed a homeostatic shift of cardiac and cerebral circulations maintaining the cerebral blood flow volume constant against ageing.

Impaired Cerebral Hemodynamics in Internal Carotid Occlusion

We performed a hemodynamic assessment involving the measurement of regional cerebral blood flow (rCBF) and regional cerebral blood volume (rCBV) with single-photon-emitting isotopes in 75 patients wit

A haemodynamic evaluation of the femoro-femoral cross-over bypass

The femoro-femoral cross-over bypass has become a popular choice for the management of unilateral iliac artery disease, being used in preference to aorto-femoral or extraperitoneal ilio-femoral bypasses. It is a relatively minor procedure and associated with a small incidence of side effects, the main one being the risk of development of a steal of blood from the donor limb by the bypass. Although this problem has been widely discussed, haemodynamic studies have been limited by the use of indirect measurements of blood flow, such as ankle systolic pressures or by the use of electromagnetic flowmetry at the time of surgery. No study employing volumetric blood flow measurements to identify and quantify blood steal in the postoperative patient has been reported to date. With aims of studying the haemodynamic effects of a femoro-femoral cross-over bypass on the circulation in both the recipient and donor limbs, and of identifying preoperatively, problems likely to lead to haemodynamic problems or to graft failure, the present study of 31 patients undergoing femoro-femoral bypass was undertaken. The patients, 18 of whom had rest pain and 13 intermittent claudication, were studied preoperatively using arteriography and a non-invasive assessment. At 3 months from the operation, all received a clinical assessment and a further non-invasive assessment, including a measurement of blood volume flow. Flow measurements were made in the bypass at rest and during a reactive hyperaemia test. In addition, flow measurements were made in the donor limb below the bypass origin at rest and during hyperaemic testing of the recipient limb in order to assess any steal effect the bypass might cause to the donor limb circulation. All 31 patients were improved by surgery, but five developed donor limb claudication which was attributed to steal in three cases. Resting blood flow in the bypasses, 161 (65-282)ml/min [median (range)], rose by 116% (5-428%) to 300 (82-1114)ml/min after hyperaemic testing. Simultaneously, bypass hyperaemia caused a fall in donor limb blood flow of 32% (0-74%). Of the preoperative non-invasive tests, only donor femoral artery pulse rise time was related to the later development of objective evidence of steal. Successful Gruntzig dilatation of four major stenoses resulted in a satisfactory outcome.

Quantitative measurement of abdominal arterial blood flow using image‐directed Doppler ultrasonography: Superior mesenteric, splenic, and common hepatic arterial blood flow in normal adults

To measure volume blood flow quantitatively in human abdominal arteries, we used an ultrasonic image-directed Doppler system and electromagnetic flowmeter to first measure volume flow in canine arteries. In dogs, there was a strong linear correlation (R = 0.98) between the product of the time average of the maximum blood flow velocity and the average cross-sectional area and the volume blood flow measured by an electromagnetic flowmeter. These results enabled measurement of volume blood flow in the human superior mesenteric (SMA), splenic (SPA), and common hepatic (CHA) arteries from the abdominal wall. Comparison of pulsatility index values indicated a larger vascular resistance in the SMA than in the SPA or CHA.

Clinical results of extracranial-intracranial bypass surgery in patients with hemodynamic cerebrovascular disease.

The importance of hemodynamic factors in the pathogenesis and treatment of cerebrovascular disease remains uncertain. The extracranial-intracranial (EC-IC) bypass trial has been criticized for failing to identify and separately analyze those patients with chronic reduction in regional cerebral perfusion pressure (rCPP) who might be most likely to benefit from surgery. Positron emission tomography (PET) measurements of regional cerebral blood flow (rCBF) and blood volume (rCBV) were performed on 29 patients with symptomatic occlusion or intracranial stenosis of the carotid arterial system prior to undergoing EC-IC bypass surgery. Twenty-four patients had evidence of reduced rCPP (increased rCBV/rCBF ratio) distal to the arterial lesion. Of 21 patients who survived surgery without stroke, three suffered ipsilateral ischemic strokes during the 1st postoperative year. A nonrandomized control group of 23 nonsurgical patients' with similar clinical, arteriographic, and PET characteristics experienced no ipsilateral ischemic strokes during the 1st year following PET. Based on these results in 44 patients, the probability that successful surgery reduces the occurrence of ipsilateral ischemic stroke 1 year later was calculated. This probability ranged from 0.045 for a 50% reduction to 0.168 for a 10% reduction. Thus, there was little evidence to suggest that measurements of cerebral hemodynamics can identify a group of patients who would benefit from EC-IC bypass surgery.

Measurement of airway mucosal perfusion and water volume with an inert soluble gas.

The purpose of this study was to develop and validate a new in vivo technique for the measurement of tracheal mucosal blood flow (Qtr) and tissue water volume (VH2O) with an inert soluble gas. The technique was based on the notion that the uptake of dimethyl ether (VDME) from an isolated tracheal segment is governed by VH2O (transient state) and Qtr (steady state). In lightly anesthetized sheep, an endotracheal tube with two cuffs placed 14.5-16.5 cm apart was placed to create a chamber into which dimethyl ether was introduced and from which VDMME into the mucosa was determined with a sensitive pneumotachograph. Mean Qtr was 1.20 ml/min (range 0.87-1.73), and mean VH2O was 1.67 ml (range 1.27-2.26). Qtr correlated with cardiac output but not with body weight or tracheal mucosal surface area determined by He dilution. VH2O did not show a correlation with any of these parameters. The response to selected pharmacological agents suggested that the measurements of Qtr and VH2O are independent of each other and from changes in tracheal diameter. Mean Qtr was 80% of mean tracheal mucosal blood flow measured with radiolabeled microspheres. We concluded that the inert soluble gas method is capable of measuring in vivo the perfusion and a water compartment of the intact tracheal mucosa.

Fetal cardiac arrhythmias and their effect on volume blood flow in descending aorta of human fetus.

Using a two-dimensional linear array real-time and pulsed Doppler ultrasound system, volume blood flow measurements were made in 86 normal pregnancies, seven cases of fetal bradycardia, and seven cases of fetal tachycardia at the lower thoracic level of the fetal descending aorta. During fetal cardiac arrhythmias, volume blood flow was maintained within the normal range until the heart rates reached around 50 bpm and 230 bpm, after which the volume blood flow diminished. The changes observed suggest that the Frank-Starling mechanism is functional in the fetal myocardium and demonstrate the stability of the fetal circulation.