Measurement Of Blood Flow Volume Research Articles

Differentiation Between High-Grade Glioma and Brain Metastasis Using Cerebral Perfusion-Related Parameters (Cerebral Blood Volume and Cerebral Blood Flow): A Systematic Review and Meta-Analysis of Perfusion-weighted MRI Techniques.

Distinguishing high-grade gliomas (HGGs) from brain metastases (BMs) using perfusion-weighted imaging (PWI) remains challenging. PWI offers quantitative measurements of cerebral blood flow (CBF) and cerebral blood volume (CBV), but optimal PWI parameters for differentiation are unclear. To compare CBF and CBV derived from PWIs in HGGs and BMs, and to identify the most effective PWI parameters and techniques for differentiation. Systematic review and meta-analysis. Twenty-four studies compared CBF and CBV between HGGs (n = 704) and BMs (n = 488). Arterial spin labeling (ASL), dynamic susceptibility contrast (DSC), dynamic contrast-enhanced (DCE), and dynamic susceptibility contrast-enhanced (DSCE) sequences at 1.5 T and 3.0 T. Following the PRISMA guidelines, four major databases were searched from 2000 to 2024 for studies evaluating CBF or CBV using PWI in HGGs and BMs. Standardized mean difference (SMD) with 95% CIs was used. Risk of bias (ROB) and publication bias were assessed, and I2 statistic was used to assess statistical heterogeneity. A P-value<0.05 was considered significant. HGGs showed a significant modest increase in CBF (SMD = 0.37, 95% CI: 0.05-0.69) and CBV (SMD = 0.26, 95% CI: 0.01-0.51) compared with BMs. Subgroup analysis based on region, sequence, ROB, and field strength for CBF (HGGs: 375 and BMs: 222) and CBV (HGGs: 493 and BMs: 378) values were conducted. ASL showed a considerable moderate increase (50% overlapping CI) in CBF for HGGs compared with BMs. However, no significant difference was found between ASL and DSC (P = 0.08). ASL-derived CBF may be more useful than DSC-derived CBF in differentiating HGGs from BMs. This suggests that ASL may be used as an alternative to DSC when contrast medium is contraindicated or when intravenous injection is not feasible. Stage 2.

Application of real time shear wave elastography to the differential diagnosis of secondary parathyroid hyperplasia and adenoma.

We aimed to explore the value of ultrasonic elastic imaging in the diagnosis of parathyroid hyperplasia and adenoma in patients with secondary hyperparathyroidism and provide more evidence for clinical treatment. Forty patients who were on dialysis and underwent parathyroid surgery were selected All patients underwent routine ultrasound, ultrasound elasticity examination and blood biochemical examination before surgery, including calcium, phosphorus, parathyroid hormone (PTH), etc. According to postoperative results, adenoma group and hyperplasia group were divided into 2 groups. Receiver operating characteristic curve was drawn to evaluate the diagnostic efficacy and combined diagnostic efficacy of each index. The PTH levels significantly differed between the adenoma and hyperplasia groups (P < .001). The volume and blood flow grades significantly differed between the adenoma and hyperplasia groups (P < .001) The minimum of the adenoma group was 14.62 ± 6.79 kPa, mean was 19.42 ± 6.29 kPa, and maximum was 24.25 ± 6.35 kPa which were significantly different from those in the hyperplasia group (P < .05). The combinations of more than 6 indicators in the diagnosis of parathyroid adenoma resulted in an area under the curve of 0.892 (P < .001), and the sensitivity and specificity were 78.9% and 97.4%, respectively. Shear wave elastography can be used as an effective tool to distinguish secondary parathyroid hyperplasia from adenoma. When combined with PTH, conventional ultrasound blood flow grading and volume measurement, it has higher diagnostic efficacy.

Comparison of carotid and vertebral artery doppler measurements in supine and sitting positions.

Carotid and vertebral Doppler ultrasonography (USG) is the primary diagnostic tool for the detection of extra cranial atherosclerotic disease and measurement of posterior fossa blood flow volume. The examination is performed while the patient lies on supine position. However, in daily practice we occasionally encounter patients who are not able to lie down on supine position for different reasons, such as kyphosis, severe dyspnea, or severe back pain. We aimed to compare the doppler spectral measurements of carotid and vertebral arteries obtained in supine and sitting positions. Fifty-three patients were recorded in the first group, to whom carotid and vertebral (CV) Doppler Ultrasound examination was initially performed while sitting, and another 52 patients were examined as the second group where initial measurements were done in a supine position. Peak systolic velocity (PSV), end diastolic velocity (ED) from each vessel, internal carotid artery (ICA)/common carotid artery (CCA) ratio, and volume flow of vertebral artery (VA) were measured in supine and sitting positions. Also, another 83 patients with a complaint of vertigo were included in the third group but only VA measurements were compared. In the first group, there was a difference between sitting and supine positions in right ICA diastolic, right and left VA diastolic, and left CCA diastolic velocities (P < 0.05). In the second group, there was a difference in sitting and supine positions in right CCA systolic, right CCA diastolic, and left CCA diastolic velocities (P < 0.05). In the third group, there was a difference in sitting and supine positions in right and left VA diastolic velocities, left VA volume flow, and total VA volume flow (P < 0.05). A strong correlation was detected between supine and sitting positions regarding right and left ICA stenoses. Alterations in waveforms were noted in three patients' unilateral VAs, in supine and sitting positions. Our results suggest that CV doppler examinations may be performed in the sitting positions. Examination in the sitting position may be helpful in recognizing pre-steal and retrograde flows.

Intraoperative Blood Flow Analysis of DIEP vs. ms-TRAM Flap Breast Reconstruction Combining Transit-Time Flowmetry and Microvascular Indocyanine Green Angiography.

Background: Vascular patency is the key element for high flap survival rates. The purpose of this study was to assess and compare the blood flow characteristics of deep inferior epigastric perforator (DIEP) and muscle-sparing transverse rectus abdominis musculocutaneous (ms-TRAM) flaps for autologous breast reconstruction. Methods: This prospective clinical study combined Transit-Time Flowmetry and microvascular Indocyanine Green Angiography for the measurement of blood flow volume, vascular resistance, and intrinsic transit time. Results: Twenty female patients (mean age, 52 years) received 24 free flaps (14 DIEP and 10 ms-TRAM flaps). The mean arterial blood flow of the flap in situ was 7.2 ± 1.9 mL/min in DIEP flaps and 11.5 ± 4.8 mL/min in ms-TRAM flaps (p < 0.05). After anastomosis, the mean arterial blood flow was 9.7 ± 5.6 mL/min in DIEP flaps and 13.5 ± 4.2 mL/min in ms-TRAM flaps (p = 0.07). The arterial vascular resistance of DIEP flaps was significantly higher than that of ms-TRAM flaps. The intrinsic transit time of DIEP flaps was 52 ± 18 s, and that of ms-TRAM flaps was 33 ± 11 s (p < 0.05). The flap survival rate was 100%. One DIEP flap with the highest intrinsic transit time (77 s) required surgical revision due to arterial thrombosis. Conclusion: In this study, we established the blood flow characteristics of free DIEP and ms-TRAM flaps showing different blood flow rates, vascular resistances, and intrinsic transit times. These standard values will help to determine the predictive values for vascular compromise, hence improving the safety of autologous breast reconstruction procedures.

In Vivo Preclinical Quantitative Flow Analysis of Arterial Anastomosis Using a Microvascular Anastomotic Coupler and Clinical Application for Extracranial-to-Intracranial Bypass

Although several commercially available sutureless anastomotic techniques are available, they are not routinely used in neurosurgery. We performed an invivo flow analysis of end-to-end anastomosis using a microvascular coupler device in rats. We report our first clinical use of the microvascular anastomotic coupler. Bilateral rat common carotid arteries (CCAs) were exposed, and a microvascular coupler was used to perform 8 anastomoses. A microflow probe provided quantitative measurement of blood-flow volume. Flow augmentation was assessed with end-to-side anastomoses connecting the distal CCA to the jugular vein (JV). A patient with chronic dominant hemisphere atherosclerotic ischemic disease and progressive symptoms refractory to medical management underwent end-to-end cerebral artery bypass using the microvascular coupler. Mean preanastomosis flow in the rat CCA was 3.95 ± 0.45 mL/min; this flow was maintained at 3.99 ± 0.24 mL/min on final measurements 54-96 minutes postanastomosis. Total occlusion time for each rat CCA was 12-19 minutes. After end-to-side anastomosis, with proximal and distal JV patent, CCA flow increased 477% to 22.8 ± 3.70 mL/min (P=0.04, proximal; P= 0.01, distal). After invivo testing, we successfully used the coupler clinically in a superficial temporal artery-to-middle cerebral artery bypass for dominant hemisphere flow augmentation. Invivo quantitative flow analysis demonstrated no flow difference between an unaltered artery and artery with end-to-end anastomosis using a microvascular coupler in rats. A 1-mm coupled anastomosis achieved a 4-fold flow increase with low-resistance venous outflow in rats, simulating increased arterial demand. The coupler was successfully used for extracranial-to-intracranial bypass in a patient.

Measurement of Strial Blood Flow in Mouse Cochlea Utilizing an Open Vessel-Window and Intravital Fluorescence Microscopy.

Transduction of sound is metabolically demanding, and the normal function of the microvasculature in the lateral wall is critical for maintaining endocochlear potential, ion transport, and fluid balance. Different forms of hearing disorders are reported to involve abnormal microcirculation in the cochlea. Investigation of how cochlear blood flow (CoBF) pathology affects hearing function is challenging due to the lack of feasible interrogation methods and the difficulty in accessing the inner ear. An open vessel-window in the lateral cochlear wall, combined with fluorescence intravital microscopy, has been used for studying CoBF changes in vivo, but mostly in guinea pig and only recently in the mouse. This paper and the associated video describe the open vessel-window method for visualizing blood flow in the mouse cochlea. Details include 1) preparation of the fluorescent-labeled blood cell suspension from mice; 2) construction of an open vessel-window for intravital microscopy in an anesthetized mouse, and 3) measurement of blood flow velocity and volume using an offline recording of the imaging. The method is presented in video format to show how to use the open window approach in mouse to investigate structural and functional changes in the cochlear microcirculation under normal and pathological conditions.

Blood Flow Volume Measurement in Cervical and Intracranial Arteries using Quantitative Magnetic Resonance Angiography and Duplex Sonography (Bocaccia) - A Prospective Observational Study.

Cerebral blood flow volume is an important factor for the accurate diagnosis of neurovascular diseases and treatment indication. This study aims to assess correlations of blood flow volume measurements in cervical and intracranial arteries between duplex sonography and quantitative magnetic resonance angiography (qMRA). Consecutive patients with suspicion of cerebral vascular pathology underwent qMRA and duplex sonography of cervical and intracranial arteries with measurement of blood flow volume in bilateral common (CCA), internal (ICA) and external carotid arteries, vertebral and basilar arteries, middle, anterior, posterior cerebral and posterior communicating arteries using 2 different ultrasound machines. Ten patients underwent all examinations twice. Correlations between blood flow volume measurements were evaluated using Spearman's correlation coefficient and inter-class correlation coefficient (ICC). In total, 21 subjects (15 males, mean age: 56.3 ± 6.2years) were included in the study. Duplex sonography inter-investigator correlation was excellent (ICC = 0.972, p < 0.0001) as well as intra-investigator correlations of both qMRA and duplex sonography (ICC ˃ 0.990, p < 0.0001). Mostly high correlations were recorded between qMRA and duplex sonography in particular cervical arteries but only low to moderate correlations were obtained for intracranial arteries. The mean differences between blood flow volume measurements were 10.9 ± 8.1 % in the CCA and its branches when using qMRA and 15.0 ± 11.9 % when using duplex sonography, 13.5 ± 11.8 %/35.4 ± 34.2 % in the ICA siphon and its branches when using qMRA/duplex sonography, and 24.1 ± 19.7 %/44.9 ± 44.0 % in both vertebral arteries and the basilar artery when using qMRA/duplex sonography. Duplex sonography as well as qMRA allow for highly reproducible measurement of blood flow volume in cervical and intracranial arteries in routine clinical practice.

Blood flow rate estimation in optic disc capillaries and vessels using Doppler optical coherence tomography with 3D fast phase unwrapping.

The retinal volumetric flow rate contains useful information not only for ophthalmology but also for the diagnosis of common civilization diseases such as diabetes, Alzheimer's disease, or cerebrovascular diseases. Non-invasive optical methods for quantitative flow assessment, such as Doppler optical coherence tomography (OCT), have certain limitations. One is the phase wrapping that makes simultaneous calculations of the flow in all human retinal vessels impossible due to a very large span of flow velocities. We demonstrate that three-dimensional Doppler OCT combined with three-dimensional four Fourier transform fast phase unwrapping (3D 4FT FPU) allows for the calculation of the volumetric blood flow rate in real-time by the implementation of the algorithms in a graphics processing unit (GPU). The additive character of the flow at the furcations is proven using a microfluidic device with controlled flow rates as well as in the retinal veins bifurcations imaged in the optic disc area of five healthy volunteers. We show values of blood flow rates calculated for retinal capillaries and vessels with diameters in the range of 12-150 µm. The potential of quantitative measurement of retinal blood flow volume includes noninvasive detection of carotid artery stenosis or occlusion, measuring vascular reactivity and evaluation of vessel wall stiffness.

Reliability and characteristics of ultrasound measurement of fetal umbilical venous blood flow volume according to the site of measurement.

This study aimed at assessing the reliability and characteristics of fetal umbilical venous blood flow volume (UVFV) measurement using ultrasound. We conducted a prospective study at our center from November 2017 to July 2019. We performed transabdominal ultrasound examinations at 18-34weeks' gestation in uncomplicated singleton pregnancies. UVFV was calculated using vessel diameter (D) and maximum flow velocity (V) as follows: (D/2)2 × π × V × 0.5 × 60 (Q, mL/min). Two examiners measured each value three times in the free-loop (FL) and intra-abdominal (IA) portions of the umbilical vein. Intra-rater and inter-rater reliability was evaluated by intraclass correlation coefficient (ICC) and a Bland-Altman plot. Two hundred and eight cases were measured by two examiners. The rate of complete measurement at FL and IA was not significantly different (88.5% vs. 79.3%, respectively; p = 0.113). The intra-rater reliability of D and V was high at FL and IA. Regarding inter-rater reliability, the ICC of D, V, and Q was 0.973, 0.582, and 0.963 at FL, and 0.994, 0.912, and 0.989 at IA, respectively. A Bland-Altman plot showed that D and V had greater standard deviation at FL than IA. Regarding Q, the standard deviation at FL was also larger than at IA, and measurement variance at FL increased as the measured value increased, but that at IA did not. UVFV measurement showed high intra-rater and inter-rater reliability at FL and IA, but the variance of measurements at FL became large as the measured value increased. Properties of different measurement sites should be considered when evaluating UVFV.

The experience of pancreas transplantation with isolated splenic artery supply

Aim. To demonstrate the possibility of successful transplantation of pancreaticoduodenal complex with isolated splenic artery supply and to assess the quality of its perfusion. Methods. 6 patients who underwent pancreas transplantation with isolated splenic artery blood supply were examined. The recipients were 3 men and 3 women, the median age was 36.5 [31; 42] years. To evaluate the state, quality of transplant perfusion and their function, the laboratory data, doppler ultrasound, measurement of blood flow volume (CT-perfusion) and treatment outcomes were assessed. Results. Based on the results of investigations, adequate pancreatic graft blood supply through the splenic artery alone was detected. Pancreatic transplant function in all patients was satisfactory, blood glucose levels remained within normal values. Hospital mortality was 0%. Conclusion. Successful transplantation of pancreaticoduodenal complex with isolated splenic artery supply is technically possible due to the presence of intraorganic arterial collaterals.

CAR 5. Carotid Flow Volume Measurement in Doppler Ultrasound as a New Look at the Diagnosis of Internal Carotid Artery Stenosis

Blood flow velocity criteria in the diagnosis of carotid stenosis are well defined; however, there are no reference values concerning blood flow volume. The objective of this work covered assessment of blood flow volume in the internal carotid artery (ICA), external carotid artery (ECA), and vertebral artery (VA) in healthy volunteers and asymptomatic patients with carotid artery disease older than 65 years with the aim of implementation of blood flow volume measurements in clinical assessment of patients with carotid artery disease. There were 303 patients without history of neurologic symptoms included in the examination. The group of 123 healthy volunteers older than 65 years, without comorbidities that may alter cerebral blood flow volume, were examined to determine reference flow volume values in the ICA, ECA, and VA. The flow parameters in this group were compared with the flow in 56 healthy volunteers younger than 65 years. To determine the influence of ICA stenosis on cerebral blood flow volume, the group of 124 patients older than 65 years with asymptomatic ICA stenosis without comorbidities that might influence hemodynamics of blood flow were examined. In all patients, an extensive Doppler ultrasound examination with measurement of blood flow volume in the ICA, ECA, and VA was performed. Cerebral blood flow volume reference values in patients older than 65 years were determined. Gradual decline in cerebral blood flow, caused mainly by the significant reduction of ICA flow volume, was observed in healthy volunteers. A decline in the peak systolic and end-diastolic velocities in the ICA and the peak systolic velocity in the ECA was observed. Two subgroups with ICA stenosis and flow volume changes were identified: patients with compensatory elevation of blood flow volume and those without compensation whose flow volume was lower than reference values. The latter subgroup contained mainly patients with >50% ICA stenosis. Among asymptomatic patients with significant ICA stenosis, there is a subgroup without compensatory elevation of blood flow volume. Those patients may be more vulnerable to cerebral ischemia and featured with increased risk of ischemic stroke.

Blood flow volume measurement in cervical and intracranial arteries using quantitative magnetic resonance angiography and duplex sonography (BOCACCIA) – A prospective observational study

Blood flow volume measurement in cervical and intracranial arteries using quantitative magnetic resonance angiography and duplex sonography (BOCACCIA) – A prospective observational study

Blood flow measurement in cervical and intracranial arteries using quantitative magnetic resonance angiography and duplex sonography (bocaccia) – a prospective observational study

Background Cerebral blood flow volume (BFV) is important factor for accurate diagnosis of neurovascular diseases and treatment indication. Study aims to assess correlations of BFV measurements in cervical and intracranial arteries between quantitative magnetic resonance angiography (qMRA) and duplex sonography. Methods Consecutive patients with suspicion of cerebral vascular pathology were included in prospective study. All patients underwent qMRA and duplex sonography of the cervical and intracranial arteries with measurement of BFV in bilateral common (CCA), internal (ICA) and externa carotid arteries, vertebral arteries (VAs), middle, anterior and posterior cerebral arteries, posterior communicanting arteries and basilar artery (BA). DS was performed using two ultrasound machines by experienced sonographers. Two patients were examined twice. Correlations between BFV measurements were evaluated using Spearman's correlation coefficient and inter-class correlation coefficient (ICC). Results Totally 21 subjects (15 males, mean age 56.3±6.2 years) were included to the study. Duplex sonography inter-investigator correlation was excellent (ICC=0.972) as well as intra-investigator correlations of both qMRA and duplex sonography (ICC˃0.990). Mostly high correlations were recorded between qMRA and duplex sonography BFV measurements in particular cervical arteries but only low to moderate correlations were obtained for intracranial arteries. Mean differences between BFV measurements in CCA and its branches were 10.9±8.1%/15.0±11.9% when using qMRA/duplex sonography, in ICA siphon and its branches 13.5±11.8%/35.4±34.2% when using qMRA/duplex sonography, and in both VAs and BA 24.1±19.7%/44.9±44.0% when using qMRA/duplex sonography, resp. Conclusion Duplex sonography and qMRA are highly reproducible methods for blood flow volume measurement in cervical and intracranial arteries in routine clinical practice. The study was registered at ClinicalTrials.gov. NCT03591523 and supported by the Ministry of Health of the Czech Republic grants No. 16-29148A, 16-30965A, 17-31016A.

Evaluation of physiological effects of AC electromagnetic fields on human body by measurement of FMD and blood flow volume.

Evaluation of physiological effects of AC electromagnetic fields on human body by measurement of FMD and blood flow volume.

A Novel Wireless Photoplethysmography Blood-Flow Volume Sensor for Assessing Arteriovenous Fistula of Hemodialysis Patients

A novel blood-flow volume (BFV) sensor is presented for assessing quality of arteriovenous fistula in hemodialysis patients via noninvasive reflectance-type photoplethysmography (PPG). BFV is nowadays in clinic practices evaluated using an ultrasound Doppler monitor, which is expensive, bulky, and can only be operated by well-trained medical personnels. This study is devoted to develop a low-cost, small-sized, portable, and easy-to-use PPG sensor that is capable of continuous measurement of BFV. New designs of front-end analog circuits, signal processing, and an intelligent neural network calibration method are employed to finally achieve high correlation ( R 2 = 0.7176), as opposed to the ultrasound Doppler monitor, with the root-mean-squared errors successfully controlled under 289 ml/min.

The 4-vessel Sampling Approach to Integrative Studies of Human Placental Physiology In Vivo.

The human placenta is highly inaccessible for research while still in utero. The current understanding of human placental physiology in vivo is therefore largely based on animal studies, despite the high diversity among species in placental anatomy, hemodynamics and duration of the pregnancy. The vast majority of human placenta studies are ex vivo perfusion studies or in vitro trophoblast studies. Although in vitro studies and animal models are essential, extrapolation of the results from such studies to the human placenta in vivo is uncertain. We aimed to study human placenta physiology in vivo at term, and present a detailed protocol of the method. Exploiting the intraabdominal access to the uterine vein just before the uterine incision during planned cesarean section, we collect blood samples from the incoming and outgoing vessels on the maternal and fetal sides of the placenta. When combining concentration measurements from blood samples with volume blood flow measurements, we are able to quantify placental and fetal uptake and release of any compound. Furthermore, placental tissue samples from the same mother-fetus pairs can provide measurements of transporter density and activity and other aspects of placental functions in vivo. Through this integrative use of the 4-vessel sampling method we are able to test some of the current concepts of placental nutrient transfer and metabolism in vivo, both in normal and pathological pregnancies. Furthermore, this method enables the identification of substances secreted by the placenta to the maternal circulation, which could be an important contribution to the search for biomarkers of placenta dysfunction.

Physiologic Reduction of Hepatic Venous Blood Flow by the Valsalva Maneuver Decreases Liver Stiffness.

Liver stiffness increases after intake of food or water, suggesting that hepatic venous blood flow affects the results of elastographic measurements. This study investigated the correlation between in vivo liver stiffness and hepatic blood flow using the Valsalva maneuver for reducing intrahepatic venous blood flow. Intrahepatic changes in venous blood flow were assessed by sonography based on the pulsed wave Doppler velocity, vessel diameter assessment, and blood flow volume measurements in the portal vein and right hepatic vein. Time-harmonic elastography at 7 harmonic driving frequencies (30-60 Hz) was used to measure liver stiffness in the right liver lobe of 15 healthy volunteers. The right hepatic vein diameter, flow volume, and peak pulsed wave velocity decreased during the Valsalva maneuver from mean ± SD values of 8.64 ± 1.85 to 6.55 ± 1.84 mm (P = .002), 0.53 ± 0.23 to 0.37 ± 0.26 L/min (P = .037), and 22.14 ± 4.87 to 17.38 ± 5.41 cm/s (P = .01), respectively. This maneuver decreased liver stiffness in all volunteers by a mean of approximately 13% from 1.71 ± 0.22 to 1.48 ± 0.22 m/s (P = .00006). Our results demonstrate that liver stiffness is sensitive to altered venous blood flow, which is of clinical importance when using elastography for evaluation of portal hypertension. Furthermore, our results indicate that accurate measurement of liver stiffness requires standardized breathing conditions to rule out effects of changes in hepatic blood flow on elastographic findings.

A quantitative imaging biomarker alliance

The Radiological Society of North America (RSNA) created the Quantitative Imaging Biomarker Alliance (QIBA) to convert “imaging systems” with subjective image interpretation to “measurement systems” with objective measurands having actionable numerical values. The goal is to create QIBA protocols and profiles that specify methods for data acquisition, analysis, and interpretation. QIBA profiles also provide specific claims of what can be accomplished by following the QIBA protocol. The intent is to validate the profile across imaging systems in a collaboration between industry, government (NIH, FDA, NIST), Pharma, clinicians, and academics. The RSNA/QIBA effort includes over 850 volunteers worldwide with Biomarker Committees for all major imaging modalities. The effort is expanding with collaborations in Japan (the Japan Radiological Society’s QIBA-Japan) and in Europe (European Institute for Biomedical Imaging Research and the European Imaging Biomarker Alliance; EIBIR—EIBALL). The QIBA ultrasound group began with a committee to investigate and minimize sources of bias and variance in shear wave speed estimates for liver fibrosis assessment. The group has grown to about 200 members and includes committees to advance biomarkers based on measurement of volume blood flow and parameters derived from contrast-enhanced ultrasound. The status and implications of these efforts will be presented.

Caffeine Does Not Reduce Blood Flow Following Arterial Anastomosis in the Rat.

Background Patients are usually advised not to consume caffeine following digital replantation. This study examined the effect of caffeine on blood flow distal to the site of anastomosis in the femoral arteries of rats. Methods A total of 28 Sprague-Dawley rats were used for this study. The femoral arteries were exposed bilaterally and baseline blood volume flow measurements were taken on intact arteries using a transit time flow-meter probe. All rats underwent transection and microvascular anastomosis of the femoral artery on the right side while the left side remained intact to serve as a control. The rats were then divided into two groups. In group 1, caffeine was administered (intraperitoneal injection of 40 mg caffeine/kg of body weight dissolved in saline) and in group 2 no caffeine was given. In both the groups, bilateral flow measurements were then taken at 30 and 60 minutes, respectively, following completion of the anastomosis. Results All anastomoses remained patent during the study time period. Caffeine had no statistical effect on blood flow distal to the anastomosis. Both anastomosed and control arteries demonstrated a statistically significant increase in blood flow at 30 and 60 minutes, respectively, postanastomosis that was independent of caffeine administration. Conclusions Caffeine does not have a statistically significant effect on blood flow distal to the anastomosis following microsurgical repair of the rat femoral artery.

Quantitative agreement between [(15)O]H2O PET and model free QUASAR MRI-derived cerebral blood flow and arterial blood volume.

The purpose of this study was to assess whether there was an agreement between quantitative cerebral blood flow (CBF) and arterial cerebral blood volume (CBVA) measurements by [(15)O]H2O positron emission tomography (PET) and model-free QUASAR MRI. Twelve healthy subjects were scanned within a week in separate MRI and PET imaging sessions, after which quantitative and qualitative agreement between both modalities was assessed for gray matter, white matter and whole brain region of interests (ROI). The correlation between CBF measurements obtained with both modalities was moderate to high (r(2): 0.28-0.60, P < 0.05), although QUASAR significantly underestimated CBF by 30% (P < 0.001). CBVA was moderately correlated (r(2): 0.28-0.43, P < 0.05), with QUASAR yielding values that were only 27% of the [(15)O]H2O-derived values (P < 0.001). Group-wise voxel statistics identified minor areas with significant contrast differences between [(15)O]H2O PET and QUASAR MRI, indicating similar qualitative CBVA and CBF information by both modalities. In conclusion, the results of this study demonstrate that QUASAR MRI and [(15)O]H2O PET provide similar CBF and CBVA information, but with systematic quantitative discrepancies.