Technique For Measuring Blood Flow Research Articles

Reproducibility of a single-volume dynamic CT myocardial blood flow measurement technique: validation in a swine model

BackgroundWe prospectively assessed the reproducibility of a novel low-dose single-volume dynamic computed tomography (CT) myocardial blood flow measurement technique.MethodsThirty-four pairs of measurements were made under rest and stress conditions in 13 swine (54.3 ± 12.3 kg). One or two acquisition pairs were acquired in each animal with a 10-min delay between each pair. Contrast (370 mgI/mL; 0.5 mL/kg) and a diluted contrast/saline chaser (0.5 mL/kg; 30:70 contrast/saline) were injected peripherally at 5 mL/s, followed by bolus tracking and acquisition of a single volume scan (100 kVp; 200 mA) with a 320-slice CT scanner. Bolus tracking and single volume scan data were used to derive perfusion in mL/min/g using a first-pass analysis model; the coronary perfusion territories of the left anterior descending (LAD), left circumflex (LCx), and right coronary artery (RCA) were automatically assigned using a previously validated minimum-cost path technique. The reproducibility of CT myocardial perfusion measurement within the LAD, LCx, RCA, and the whole myocardium was assessed via regression analysis. The average CT dose index (CTDI) of perfusion measurement was recorded.ResultsThe repeated first (Pmyo1) and second (Pmyo2) single-volume CT perfusion measurements were related by Pmyo2 = 1.01Pmyo1 − 0.03(ρ = 0.96; RMSE = 0.08 mL/min/g; RMSE = 0.07 mL/min/g) for the whole myocardium, and by Preg2 = 0.86Preg1 + 0.13(ρ = 0.87; RMSE = 0.31 mL/min/g; RMSE = 0.29 mL/min/g) for the LAD, LCx, and RCA perfusion territories. The average CTDI of the single-volume CT perfusion measurement was 10.5 mGy.ConclusionThe single-volume CT blood flow measurement technique provides reproducible low-dose myocardial perfusion measurement using only bolus tracking data and a single whole-heart volume scan.Relevance statementThe single-volume CT blood flow measurement technique is a noninvasive tool that reproducibly measures myocardial perfusion and provides coronary CT angiograms, allowing for simultaneous anatomic-physiologic assessment of myocardial ischemia.Key PointsA low-dose single-volume dynamic CT myocardial blood flow measurement technique is reproducible.Motion misregistration artifacts are eliminated using a single-volume CT perfusion technique.This technique enables combined anatomic-physiologic assessment of coronary artery disease.Graphical

Dynamic Light Scattering in Biomedical Applications: feature issue introduction

The feature Issue on “Dynamic Light Scattering in Biomedical Applications” presents a compilation of research breakthroughs and technological advancements that have shaped the field of biophotonics, particularly in the non-invasive exploration of biological tissues. Highlighting the significance of dynamic light scattering (DLS) alongside techniques like laser Doppler flowmetry (LDF), diffusing wave spectroscopy (DWS), and laser speckle contrast imaging (LSCI), this issue underscores the versatile applications of these methods in capturing the intricate dynamics of microcirculatory blood flow across various tissues. Contributions explore developments in fluorescence tomography, the integration of machine learning for data processing, enhancements in microscopy for cancer detection, and novel approaches in optical biophysics, among others. Innovations featured include a high-resolution speckle contrast tomography system for deep blood flow imaging, a rapid estimation technique for real-time tissue perfusion imaging, and the use of convolutional neural networks for efficient blood flow mapping. Additionally, studies delve into the impact of skin strain on spectral reflectance, the sensitivity of cerebral blood flow measurement techniques, and the potential of photobiomodulation for enhancing brain function. This issue not only showcases the latest theoretical and experimental strides in DLS-based imaging but also anticipates the continued evolution of these modalities for groundbreaking applications in disease detection, diagnosis, and monitoring, marking a pivotal contribution to the field of biomedical optics.

Ultrasound Speckle Decorrelation-Based Blood Flow Measurements.

Ultrasound imaging is the preferred noninvasive technique to measure blood flow to diagnose cardiovascular disease such as heart failure, carotid stenosis, and renal failure. Conventional ultrasound techniques such as Doppler ultrasound, ultrasound imaging velocimetry, vector Doppler and transverse oscillation beamforming have been used for blood flow velocity profile measurement. However, these techniques were limited to measuring blood flow velocities within the 2-D lateral (across the ultrasound beam) plane of a vessel, and the blood flow velocity profile was derived by assuming that blood vessels have a circular cross-section with axis symmetry. This assumption is incorrect because most vessels have complex geometries, such as tortuosity and branches, and an asymmetric flow profile in the presence of vascular plaque. Consequently, ultrasound speckle decorrelation has been proposed to measure blood flow from transverse views of blood vessels wherein the ultrasound beam is perpendicular to the vessel axis. In this review, we present a summary of recent progress in ultrasound speckle decorrelation-based blood flow measurement techniques.

Technique for comprehensive fetal hepatic blood flow assessment in sheep using 4D flow MRI.

The comprehensive visualization and quantification of in vivo fetal hepatic haemodynamics, particularly the shunting of ductus venosus blood, has been elusive and is not yet fully understood. We introduce the combination of chronically instrumented fetal sheep and 4D flow MRI of the whole fetal liver, which allows retrospective blood flow measurement in all visible vessels as well as qualitative assessment. The applicability and usefulness of this technique is exhibited in normally grown fetal Merino sheep in mid- and late-gestation with detailed dynamic distribution of hepatic blood flow presented. The feasibility of this approach in clinical pathology is demonstrated in two growth-restricted fetuses at mid-gestation. Further exemplification of blood flow quantification is performed over major hepatic vessels. Although the fetal vasculature has been demarcated and well understood for several decades, the corresponding haemodynamics permitting oxygen- and nutrient-rich blood delivery to the fetal organs has been comparatively difficult to study. We married two well-established methods: 4D flow MRI, a volumetric and dynamic blood-flow measurement technique, and chronically instrumented sheep to broadly assess fetal hepatic circulation. We performed this technique in mid- and late-gestation fetal Merino sheep under normoxemic conditions and major hepatic vasculature was segmented to quantify blood flow and related parameters. Dynamic blood flow was visualized, exhibiting an acceleration of umbilical vein blood through the ductus venosus as well as spiralling into the inferior vena cava where its stream remained separate from that of the hepatic veins and lower body. Ductus venosus changes from mid- to late-gestation included larger diameter (mid: 5.8±0.9 vs. late: 7.1±1.1mm; P=0.003) and cross-sectional area (mid: 27.1±8.6 vs. late: 40.4±11.8mm2 ; P=0.003), and lower velocity averaged over the cardiac cycle (mid: 15.7±5.4 vs. late: 9.8±7.0cms-1 ; P=0.020). This resulted in higher magnitude blood flow (indexed to umbilical vein input) at mid-gestation in the ductus venosus (mid: 0.73±0.21; late: 0.46±0.21; P=0.008). The visualization and quantification results support the further use of this technique to better understand regional blood flow changes during normal or abnormal fetal growth, as well as to observe acute haemodynamic responses to physiological challenges or drug interventions.

A Simple Capillary Blood Cell Flow Monitoring System using Magnetic Micro-Sensor: A Simulation Study

Since blood flow is a physiologically important parameter in determining the state of the tissue (e.g., viability and activity), various blood flow measurement techniques have been developed. However, existing blood flow measurement methods require complex equipment to generate external energy sources to be applied onto the tissue. This paper describes a magnetic method for the simple and external source-free measurement of blood flowing throughout the capillary. A microcoil located near to the capillary captures the intrinsic magnetic field produced by flowing negatively charged blood cells (e.g., red blood cells and white blood cells) to induce the electromotive force (EMF). The velocity of blood cells is estimated using the time interval between adjacent peaks and the slope of the induced EMF. The direction of blood flow can also be determined based on the frequency shift of the induced EMF. When moving the microcoil in the same direction of the blood flow, the frequency of induced EMF decreases, whereas an increased frequency is observed when moving the microcoil in the opposite direction to the blood flow. Moreover, this method could detect and distinguish streams of red blood cells and white blood cells. These results support the feasibility of a non-invasive magnetic blood flow monitoring system that does not require any external power source applied to the blood stream and thereby alleviates the complexity of conventional blood flow monitoring systems.

Differences in salivary secretory function between patients with erosive esophagitis and those with nonerosive reflux disease

It has been speculated that impaired salivary flow contributes to abnormal acid clearance in patients with erosive esophagitis (EE). For easy and objective assessment of salivary function, we developed a salivary gland blood flow measurement technique using continuous-wave Doppler sonography. In the present study, we evaluated the salivary secretory function in patients with EE and those with nonerosive reflux disease (NERD) using this method. Doppler waveform analysis was performed on the facial artery to assess blood inflow to the submandibular gland of 30 healthy subjects (HS). Blood flow was compared before and after secretory stimulation with 1mL of lemon juice. Saliva was simultaneously collected and weighed before and after stimulation. Continuous-wave Doppler sonography was also performed in patients with EE and NERD. The size of the submandibular gland was compared in 26 patients with EE, 41 patients with NERD, and 86 HS. The submandibular gland blood flow increased after stimulation in all HS. Both within-day and day-to-day reproducibility were good. There was a significant correlation between the percent increase in the maximum velocity and the percent increase in salivary secretion. Although the size of the submandibular gland was not significantly different among the three groups, the percent increase in the maximum velocity in patients with EE was significantly smaller than that in HS. We have established an easy method of assessing salivary function in daily practice. This study revealed that a decrease in salivary secretory function is involved in the pathology of EE.

Laser Doppler Flow Meter: A New Approach for Calculation of Human Blood Flow Rate

In this paper, we are going to introduce the new technique for measurement of blood flow rate in humans based on LDF (Laser Doppler Flowmetry) technique. We had developed overall embedded system which takes input from laser Doppler blood flow sensor & gives output on personal computer via wireless communication. The structure of the sensor consists of two compartments with a light dependant resistor (LDR) and a laser diode in each. The size & weight of sensor & overall system is very less. The overall system is powered through a dedicated battery & hence power saving arrangement is also provided. Proper blood flow in human body is essential because an adequate amount of blood supply is necessary for the proper functioning of all body organs as blood carries all the nutrients and oxygen that our body needs to stay healthy. Improper blood flow rate is main symptoms of various diseases. The measurement of the blood flow can therefore provide essential information for the judgment of diseases. Since changes in blood flow occurs with the very primary stage of disease, with a fast, reliable blood flow measurement technique, the physicians have a new option for early disease diagnosis. So using this system, we can successfully & easily able to measure human blood flow rate. Major advantage of this technique is this method is noninvasive which means not involving the introduction of instruments into the body[1][2]

Taking the perfect nuclear image: Quality control, acquisition, and processing techniques for cardiac SPECT, PET, and hybrid imaging

Nuclear Cardiology for the past 40 years has distinguished itself in its ability to non-invasively assess regional myocardial blood flow and identify obstructive coronary disease. This has led to advances in managing the diagnosis, risk stratification, and prognostic assessment of cardiac patients. These advances have all been predicated on the collection of high quality nuclear image data. National and international professional societies have established guidelines for nuclear laboratories to maintain high quality nuclear cardiology services. In addition, laboratory accreditation has further advanced the goal of the establishing high quality standards for the provision of nuclear cardiology services. This article summarizes the principles of nuclear cardiology single photon emission computed tomography (SPECT) and positron emission tomography (PET) imaging and techniques for maintaining quality: from the calibration of imaging equipment to post processing techniques. It also will explore the quality considerations of newer technologies such as cadmium zinc telleride (CZT)-based SPECT systems and absolute blood flow measurement techniques using PET.

Accurate Blood Flow Measurements: Are Artificial Tracers Necessary?

Imaging-based blood flow measurement techniques, such as particle image velocimetry, have become an important tool in cardiovascular research. They provide quantitative information about blood flow, which benefits applications ranging from developmental biology to tumor perfusion studies. Studies using these methods can be classified based on whether they use artificial tracers or red blood cells to visualize the fluid motion. We here present the first direct comparison in vivo of both methods. For high magnification cases, the experiments using red blood cells strongly underestimate the flow (up to 50% in the present case), as compared to the tracer results. For medium magnification cases, the results from both methods are indistinguishable as they give the same underestimation of the real velocities (approximately 33%, based on in vitro reference measurements). These results suggest that flow characteristics reported in literature cannot be compared without a careful evaluation of the imaging characteristics. A method to predict the expected flow averaging behavior for a particular facility is presented.

げっ歯類の脳循環測定から探る脳血流調節機序

脳血管機能障害や脳精神疾患の診断とその治療評価には，ポジトロン断層画像法（PET）や機能的核磁気共鳴画像法（fMRI）など生体イメージング技術による脳血流測定が用いられる。これらイメージング技術から得られる情報を治療に正しく活かすには，脳血流の動態調節機序を正確に理解する必要がある。げっ歯類などモデル動物を対象とした脳血流動態の基礎研究は，マイクロレベルの微小血管で生じる脳血流の調節機序を明らかにする上で極めて重要な意味をもつ。げっ歯類を用いたこれまでの脳血流測定の多くは麻酔条件下で行われてきた。麻酔は実験動物福祉（苦痛やストレスの軽減）や計測技術（自発運動による振動ノイズの抑制）の観点から必要であるが，薬剤による生理機能への影響が測定結果に反映されるなどの問題も存在した。著者らは覚醒状態のげっ歯類を用いた脳血流実験システムを開発し，本来の生理状態を維持した条件下での脳血流動態の測定を可能とした。本稿では，脳血流の調節機序に関する最近の知見を概説するとともに，覚醒マウスから得られた脳血流調節機序の一端について紹介する。

Comparaison des mesures des débits d’abords vasculaires pour hémodialyse obtenues par méthode de thermodilution utilisant le module Blood Temperature Monitoring et par débimétrie doppler

BackgroundAccess blood flow measurements are considered useful indicators for thrombosis prevention. It was the purpose of this study to compare measurements of access blood flow by two different techniques: duplex doppler and BTM thermodilution. MethodsPatients included must be on chronic hemodialysis on arterioveinous vascular access. They must be in a unit fit with hemodialysis generator equipped with BTM tool. The measurements of access blood flow were made during the first hour of the hemodialysis session. A measurement with each technique was performed for each patient. ResultsFifteen patients were included: seven men and eight women, average age 60.8±9.2 years, average weight 76±16kg, duration on hemodialysis therapy 6.6±6.1 years. Access blood flow was native fistula (14 patients) and a prothetic access (one patient). Average access blood flow was 1088±586mL/mn (doppler) and 1094±570mL/mn (BTM). Comparison of access flows obtained by the BTM and doppler techniques showed a strong linear relationship. The average time to perform a measure was six minutes for the doppler technique and five minutes for the BTM technique. No adverse effect was observed in our study. ConclusionOur study shows a strong correlation between the two techniques (doppler and BTM) for the measurement of hemodialysis access blood flow. The BTM access blood flow measurement technique is fast, economic and made during the hemodialysis session by the nurse.

Measurements of wound edge microvascular blood flow during negative pressure wound therapy using thermodiffusion and transcutaneous and invasive laser Doppler velocimetry

The effects of negative pressure wound therapy (NPWT) on wound edge microvascular blood flow are not clear. The aim of the present study was therefore to further elucidate the effects of NPWT on periwound blood flow in a porcine peripheral wound model using different blood flow measurement techniques. NPWT at -20, -40, -80, and -125 mmHg was applied to a peripheral porcine wound (n = 8). Thermodiffusion, transcutaneous, and invasive laser Doppler velocimetry were used to measure the blood perfusion 0.5, 1.0, and 2.5 cm from the wound edge. Thermodiffusion (an invasive measurement technique) generally showed a decrease in perfusion close to the wound edge (0.5 cm), and an increase further from the edge (2.5 cm). Invasive laser Doppler velocimetry showed a similar response pattern, with a decrease in blood flow 0.5 cm from the wound edge and an increase further away. However, 1.0 cm from the wound edge blood flow decreased with high pressure levels and increased with low pressure levels. A different response pattern was seen with transcutaneous laser Doppler velocimetry, showing an increase in blood flow regardless of the distance from the wound edge (0.5, 1.0, and 2.5 cm). During NPWT, both increases and decreases in blood flow can be seen in the periwound tissue depending on the distance from the wound edge and the pressure level. The pattern of response depends partly on the measurement technique used. The combination of hypoperfusion and hyperperfusion caused by NPWT may accelerate wound healing.

Noninvasively measuring the hemodynamic effects of massage on skeletal muscle: A novel hybrid near-infrared diffuse optical instrument

Increase in tissue blood flow is one of the most acknowledged potential effects of massage; however, actual research studies examining this phenomenon are inconsistent and inconclusive. One possible reason for continued uncertainty regarding this topic is methodology, specifically how tissue blood flow is measured because limitations exist in previously utilized technologies. Near-infrared spectroscopy (NIRS) affords massage researchers a versatile and non-invasive measurement option by providing dynamic information on oxy- and deoxy-hemoglobin concentrations, total hemoglobin concentration, and blood oxygen saturation in deep tissue. Near-infrared diffuse correlation spectroscopy (DCS) is an innovative technique for continuous non-invasive measurement of blood flow in deep tissue. The combination of these two technologies has resulted in a novel hybrid diffuse optical instrument for simultaneous measurement of limb muscle blood flow and oxygenation. The purposes of this short report are to review previous blood flow measurement techniques and limitations in massage therapy research, introduce a novel hybrid near-infrared diffuse optical instrument that addresses previous limitations in the assessment of hemodynamic properties, outline a proposed massage therapy pilot study utilizing the novel measurement technology, and present sample data from a pilot participant using the introduced novel technology.

Computed tomographic x-ray velocimetry

An x-ray velocimetry technique is described which provides three components of velocity measurement in three dimensional space. Current x-ray velocimetry techniques, which use particle images taken at a single projection angle, are limited to two components of velocity measurement, and are unable to measure in three dimensions without a priori knowledge of the flow field. The proposed method uses multiple projection angles to overcome these limitations. The technique uses a least-squares iterative scheme to tomographically reconstruct the three-dimensional velocity field directly from two-dimensional image pair cross-correlations, without the need to reconstruct three-dimensional particle images. Synchrotron experiments demonstrate the effectiveness of the technique for blood flow measurement in opaque vessels, with applications for the diagnosis and treatment of cardiovascular disease.

Hyperemic flow heterogeneity within the calf, foot, and forearm measured with continuous arterial spin labeling MRI

Arterial spin labeling (ASL) is a noninvasive magnetic resonance imaging (MRI) technique for microvascular blood flow measurement. We used a continuous ASL scheme (CASL) to investigate the hyperemic flow difference between major muscle groups in human extremities. Twenty-four healthy subjects with no evidence of vascular disease were recruited. MRI was conducted on a 3.0 Tesla Siemens Trio whole body system with a transmit/receive knee coil. A nonmagnetic orthopedic tourniquet system was used to create a 5-min period of ischemia followed by a period of hyperemic flow (occlusion pressure = 250 mmHg). CASL imaging, lasting from 2 min before cuff inflation to 3 min after cuff deflation, was performed on the midcalf, midfoot, and midforearm in separate sessions from which blood flow was quantified with an effective temporal resolution of 16 s. When muscles in the same anatomic location were compared, hyperemic flow was found to be significantly higher in the compartments containing muscles known to have relatively higher slow-twitch type I fiber compositions, such as the soleus muscle in the calf and the extensors in the forearm. In the foot, the plantar flexors exhibited a slightly delayed hyperemic response relative to that of the dorsal compartment, but no between-group flow difference was observed. These results demonstrate that CASL is sensitive to flow heterogeneity between diverse muscle groups and that nonuniform hyperemic flow patterns following an ischemic paradigm correlate with relative fiber-type predominance.

Measurement of renal blood flow in human subjects using the ultrasound velocity profiling technique.

To (1) assess the accuracy of the ultrasound velocity profiling (USVP) technique of renal blood flow (RBF) measurement in normal subjects and (2) compare renal blood flow measurements obtained using USVP and renal clearance rate in patients with renal diseases. First, we calculated unilateral renal blood flow (unil-RBF) using USVP and the clearance rate of para-aminohippuric acid (CPAH) simultaneously in six healthy male subjects. We then compared unil-RBFUSVP and unil-RBFPAH in nine patients with chronic glomerulonephritis (CGN). In the first study, the limits of agreement in a Bland-Altman plot ranged from -325.3 to 32.0 ml/min per 1.48 m(2). The mean bias was -146.7 ml/min per 1.48 m(2). Subdivision for values of unil-RBFUSVP by flow showed small discrepancies in values above 280 ml/min per 1.48 m(2): mean bias, -98.2 ml/min per 1.48 m(2); limits of agreement, -223.3 to 26.8 ml/min per 1.48 m(2). The three patients in the second study had immunoglobulin A (IgA) nephropathy, in whom unil-RBFPAH was estimated as being markedly lower than unil-RBFUSVP, contrary to the primary result. Despite its consistent negative bias, USVP may be a reliable method of quantifying renal blood flow noninvasively when measured values exceed 280 ml/min per 1.48 m(2). We assumed that the p-aminohippurate extraction rate (EPAH) was profoundly impaired in the three patients with IgA nephropathy.

Expanding role of MR angiography in clinical practice

MRA has higher accuracy, less operator dependence, a larger field-of-view, three-dimensionality and superior contrast resolution than ultrasonography. Additionally, MRA offers a safer alternative to the patient than CTA as neither ionizing radiation nor iodinated contrast agents are used. Contrast-enhanced MRA with extra cellular contrast agents is fast and flow-independent, offers substantially higher spatial and temporal resolution compared to non-contrast techniques and has become the standard of practice. The highly accurate but static anatomical road-map thus generated can be supplemented with time-resolved MRA and blood flow measurement techniques for a more comprehensive assessment of systemic vascular disease. In the context of burgeoning technological advances with rapid translation into clinical MRA practice, this review explores the current position of MRA and the potential role for the new and exciting blood-pool contrast agents for diagnosing and characterizing vascular disease. Blood-pool agents offer the potential to take MRA to the next level by combining first-pass arterial phase imaging with steady state high-resolution images that exploit the persistent high intravascular enhancement generated by blood-pool agents and which is significantly greater than with extra cellular agents. Additional benefits derive from the ability to characterize plaque and to detect internal bleeding. These advantages place MRA in a prime position to comprehensively and non-invasively evaluate both vascular anatomy and function with anticipated further expansion into more and more clinical applications.

Measurement of Portal Blood and Transjugular Intrahepatic Portosystemic Shunt Flow with Use of a Retrograde Thermodilutional Catheter

Direct blood flow measurement in the portal vein (PV) and in transjugular intrahepatic portosystemic shunts (TIPS) holds potential as a means of optimizing shunt creation and predicting outcomes. A retrograde thermodilutional flow measurement catheter was recently designed. The purpose of this study was to validate and optimize the technique of blood flow measurement in the PV with use of this catheter in a swine model of TIPS. Six domestic swine underwent TIPS creation. At day 14, shunts were catheterized for venography and portal blood flow measurement with use of thermodilutional catheters. Simultaneous flow measurements were made with use of the thermodilutional and perivascular methods at the same anatomic location within the PV. To test reproducibility of the flow measurement, repeated measurements were performed in the PV and shunt. Fifty-five measurements of PV blood flow with the thermodilutional catheter and perivascular probe were made in five animals. Perivascular probe placement was unsuccessful in one animal. There was high correlation between the thermodilutional and perivascular measurements (r(2) = 0.96; Q(periv) = 0.80 . Q(therm) + 147 mL/min; n = 55; range, 205-1541 mL/min). The difference between two consecutive thermodilutional measurements and their mean was less than 50 mL/min in 72% of measurements and less than 100 mL/min in 94% of measurements (N = 85 pairs). Measurement of PV blood flow with use of a retrograde thermodilutional catheter system yields reliable and reproducible results. This catheter system holds promising utility as a device for measuring flow within TIPS and the PV.

Microspheres accurately predict regional bone blood flow.

Even though the microsphere method frequently is used to determinate bone blood flow, validation of this technique for bone blood flow measurement is incomplete. The method is based on the principle that injected microspheres are distributed with the arterial blood and trapped in the capillaries because of their diameter (15 microm). The number of spheres lodged in an organ is proportional to its blood flow. The number of radioactive or fluorescent microspheres in a specific organ is determined indirectly by measuring radioactivity or fluorescence intensity in the organ. In this study the reliability and precision of the microsphere method for determining bone blood flow was established using radioactive and fluorescent microspheres. Six female, anesthetized New Zealand rabbits received left ventricular injections of pairs of fluorescent and/or radioactive microspheres. The humerus, femur, and tibia were dissected in a standardized manner and blood flow was determined in each sample. Comparison of relative blood flow values showed an excellent correlation between radioactive and fluorescent microspheres. The percentage difference and variation between two simultaneously injected sets of microspheres was minimal for radioactive microspheres (0.8% +/- 9.6%) and for fluorescent microspheres (0.2% +/- 11.4%). Regional bone blood flow in different regions of the femur, tibia, or humerus ranged from 2.2-28.1 mL/minute/100 g, but there was no significant difference between right and left bone samples of the same region after repeated measurement. Radioactive and fluorescent microspheres allow precise determination of regional bone blood flow.

The acute cerebrovascular effects of intracarotid adenosine in nonhuman primates.

In this study we sought to determine the acute cerebrovascular effects of intracarotid adenosine by using real-time cerebral blood flow (CBF) measurements in nonhuman primates. The internal carotid arteries of healthy anesthetized baboons were transfemorally cannulated. Changes in CBF were continuously measured at baseline and with 6 increasing doses of adenosine (0.002 to 1.5 mg/min) by use of an intraparenchymal thermal diffusion (TD) probe. Each infusion lasted 5 min. At baseline and at the largest dose of adenosine, CBF was also determined by the intraarterial (133)Xe technique. TD measurements revealed a dose-dependent increase in CBF from 32 +/- 6 mL x l00 g(-1) x min(-1) at baseline to 90 +/- 38 mL x l00 g(-1) x min(-1) with the largest dose of adenosine (n = 5; P < 0.0001). A similar magnitude of increase in CBF was also observed with (133)Xe CBF measurements. No significant increases in intracranial pressure or adverse systemic hemodynamic side effects were observed during adenosine infusion. The increase in CBF after adenosine lasted only for the duration of drug infusion. In conclusion, the transient cerebrovascular effects of intracarotid adenosine make it suitable for a trial of intraarterial vasodilator therapy and for controlled manipulation of cerebrovascular resistance. Using a real-time cerebral blood flow (CBF) measurement technique, we evaluated the acute cerebrovascular effects of intracarotid adenosine in anesthetized baboons. The increase in CBF lasted only for the duration of the adenosine infusion. Adenosine might be a suitable drug for trial as an intraarterial vasodilator for the treatment of cerebral vasospasm.