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PubMedDate not supplied

Quantification of technetium 99m-labeled sestamibi single-photon emission computed tomography based on mean counts improves accuracy for assessment of relative regional myocardial blood flow: experimental validation in a canine model.

BACKGROUND: Quantification of single-photon emission computed tomographic (SPECT) images is generally based on determination of maximal counts on radial sectors of short-axis slices. We hypothesized that analysis of mean counts may reduce estimation error. METHODS AND RESULTS: We compared quantitative 99mTc-labeled sestamibi (MIBI) SPECT based on maximal myocardial counts with that based on mean myocardial counts for accuracy of quantifying relative regional myocardial perfusion in a canine model of permanent left anterior descending coronary artery occlusion. MIBI and radiolabeled microspheres were injected during left anterior descending coronary artery occlusion. Relative microsphere myocardial blood flow was expressed as a percentage of normal (left circumflex coronary artery territory) blood flow. SPECT imaging was performed in vivo and ex vivo. Relative MIBI uptake on SPECT short-axis slices was quantified with normalized circumferential profiles based on maximal and mean counts. In vivo and ex vivo SPECT relative myocardial count density was compared to relative myocardial blood flow in six dogs. In the comparisons, percent errors in estimating the relative blood flow and relative flow deficit with MIBI SPECT imaging were calculated. There was an excellent correlation between absolute myocardial tissue MIBI activity and regional myocardial blood flow for each of the six dogs (r = 0.90 to 0.98). The correlations between relative myocardial count density on SPECT and relative blood flow for individual sectors were similar for maximal and mean count profiles (maximal, 0.79 to 0.83; mean, 0.77 to 0.82). Comparing the nadirs of in vivo and ex vivo circumferential count profiles, the correlations were slightly better (maximal, 0.82 to 0.91; mean, 0.87 to 0.91). Average percent errors in assessing relative blood flow and relative flow deficit were decreased significantly by use of mean count profiles (p < 0.05). CONCLUSIONS: Relative SPECT count density with either maximal or mean count profiles correlated well with relative myocardial blood flow. Compared with maximal count profiles, quantification with mean count profiles improved estimation of relative flow.

Animals↗

PubMed2003

Spotting and quantification of phosphoproteins purified by gel electrophoresis and laser ablation-element mass spectrometry with phosphorus-31 detection.

Laser ablation inductively coupled plasma-mass spectrometry (ICP-MS) with (31)P detection has been used for spotting of phosphoproteins after one-dimensional polyacrylamide gel electrophoresis (1-D PAGE) and membrane transfer. By analyzing a mixture of myoglobin, alpha-casein and reduced fibrinogen it is demonstrated that phosphoproteins are specifically recognized by this method. A special washing step was found to be necessary to remove phosphate noncovalently bound to proteins. The (31)P signal was found to contain quantitative information both with respect to relative and absolute amounts of phosphorus present in phosphoproteins. Normalizing the (31)P signal from a single laser ablation trace by the total amount of phosphoprotein applied to the gel, a detection limit of 5 pmol of phosphorus is estimated.

Blotting, Western↗

PubMed2004

Quantification of Jkappa signal end breaks in developing B cells by blunt-end linker ligation and qPCR.

Introduction of a double-strand DNA break at the junction between a rearranging gene segment and its flanking recombination signal sequence (RSS) is the first step of V(D)J recombination. Such DNA breaks can be detected by either Southern blot hybridization or ligation-mediated PCR. While Southern blotting is easily quantifiable, it is often insufficiently sensitive and while LM-PCR is far more sensitive, it is poorly quantifiable. Reported here is a LM-qPCR assay which relies on real-time qPCR to provide an absolute measure of recombinase-mediated, or any other specific, double-strand DNA break in genomic DNA. The efficiency of the initial ligation reaction was found to be relatively low with just 3% of potential targets undergoing linker ligation. Using this assay, approximately 16% of murine bone marrow pre-B cells were determined to contain a dsDNA break adjacent to the Jkappa1 gene segment. In addition, the kinetics of Jkappa1 dsDNA breaks in a temperature-sensitive cell line induced to recombine its kappa locus was determined.

Animals↗

PubMed1995

Quantification of the Contribution of CO2, HCO3-, and External Carbonic Anhydrase to Photosynthesis at Low Dissolved Inorganic Carbon in Chlorella saccharophila.

An equation has been developed incorporating whole-cell rate constants for CO2 and HCO3- that describes accurately photosynthesis (Phs) in suspensions of unicellular algae at low dissolved inorganic carbon. At pH 8.0 the concentration of CO2 available to the algal cells depends on the rate of supply from, and the loss to, HCO3- and the rate of use by the cells. At elevated cell densities (>30 mg chlorophyll [Chl] L-1), at which CO2 use by the cells is high, the slope of a graph of absolute Phs versus Chl concentration approaches the rate of Phs on a milligram of Chl basis because of HCO3- use alone. The slope of a graph of Phs versus HCO3- will be the rate constant for HCO3-, and for Chlorella saccharophila it was 0.16 L mg-1 Chl h-1. The difference between the constants for dissolved inorganic carbon (measured in cells with external carbonic anhydrase) and HCO3-1 is the constant for CO2, which was 26 L mg-1 Chl h-1. This difference causes the half-saturation constant for Phs to increase 5- to 6-fold at high cell densities. The increase in CO2 use as a result of external carbonic anhydrase is described mathematically as a function of cell density.

Journal Article↗

PubMed1975

[Objective grading of stenosing coronary artery processes through the quantification of pathological-anatomical data their relations 1. Basic methodical concept and 1st results].

Proceeding from an estimation of the hitherto known models of the judgement of the coronary arteriosclerosis and the achieved degree of quantificability methodic principles are developed to quantify the influence of pathologo-anatomical parameters on the myocardial infarction with the help of mathematical methods using electronic data processing. With the help of the comparison of evaluation schemata according to Herzog/Schoenmackers and Romaniuk/Schroder on the basis of 174 hearts coronarographed post mortem a possibility is demostrated to estimate objectively the efficiency of evaluation schemata. The improvement of the evaluation after inclusion of the absolute mass of the heart is demonstrated. Herzog/Schoenmackers's valuation after the mathematical judgement of the probationers examined results in a wrong coordination of altogether 15 per cent, Romaniuk/Schroder's valuatiom results in 12.6 per cent. After the inclusion of the abolute mass of the heart into this valuation a decrease of the malcoordination to 10.3 per cent was achieved.

Coronary Disease↗

PubMed2005

Optimization of the determination of polybrominated diphenyl ethers in human serum using solid-phase extraction and gas chromatography-electron capture negative ionization mass spectrometry.

A simple, rapid, sensitive and reproducible method based on solid-phase extraction (SPE) and acidified silica clean-up was developed for the measurement of 12 polybrominated diphenyl ethers (PBDEs), including BDE 209, and 2,2',4,4',5,5'-hexabromobiphenyl (BB 153) in human serum. Several solid-phase sorbents (Empore C(18), Isolute Phenyl, Isolute ENV+ and OASIS HLB) were tested and it was found that OASIStrade mark HLB (500 mg) gives the highest absolute recoveries (between 64% and 95%, R.S.D.<17%, n=3) for all tested analytes and internal standards. Removal of co-extracted biogenic materials was performed using a 6 ml disposable cartridge containing (from bottom to top) silica impregnated with sulphuric acid, activated silica and anhydrous sodium sulphate. PBDEs and BB 153 were quantified using a gas chromatograph coupled with a mass spectrometer (MS) operated in electron-capture negative ionization mode. The method limits of quantification (LOQ) ranged between 0.2 and 25 pg/ml serum (0.1 and 4 ng/g lipid weight). LOQs were dependent on the analyte levels in procedural blanks which resulted in the highest LOQs for PBDE congeners found in higher concentrations in blanks (e.g. BDE 47, 99 and 209). The use of OASIS HLB SPE cartridge allowed a good method repeatability (within- and between-day precision<12% for all congeners, except for BDE 209<17%, n=3). The method was applied to serum samples from a random Belgian population. The obtained results were within the range of PBDE levels in other non-exposed population from Europe.

Chemical Fractionation↗

PubMed1999

High prevalence of sensitization to cat allergen among Japanese children with asthma, living without cats.

BACKGROUND: Cat allergy is common among children with asthma. Many cat-allergic patients in Japan and elsewhere do not keep cats, but nonetheless become sensitized through environmental exposure to cat allergen. OBJECTIVE: To assess the frequency of cat allergy and cat-specific immunoglobulin E (IgE) and immunoglobulin G (IgG) antibody responses in young Japanese patients with asthma in relation to self-reported cat exposure and Fel d 1 levels in dust samples. METHODS: Cat dander-specific IgE antibody was measured in sera from asthma patients using the CAP system. IgE and IgG antibody to Fel d 1 was measured by antigen binding radioimmunoassay and by chimeric enzyme immunoassay. Fel d 1 levels in dust samples from a subset of patients' homes were measured by monoclonal antibody-based enzyme immunoassay. RESULTS: Cat-specific IgE (CAP class>/=2) was found in sera from 70% of 44 patients who kept cats and 34% of 394 patients who had never kept cats. The prevalence of sensitization increased progressively to age 6 years (40%: positive), and then increased gradually to age 16 years (approximately 60%: positive) in patients who had never kept cats. There was an excellent correlation between cat CAP values and IgE levels to Fel d 1. The absolute amount of IgE antibody to Fel d 1 ranged from 0.01 to 15.6% of total IgE. Most patients who did not keep cats were exposed to Fel d 1 levels ranging from 0.07-8 microg/g dust. CONCLUSIONS: Sensitization to cat allergen is common among young asthmatic patients in Japan, even among patients who do not keep cats. Use of CAP and the chimeric enzyme-linked immunosorbent assay allows accurate diagnosis of cat allergy and quantification of specific IgE antibody levels.

Adolescent↗

PubMed1989

Separation and quantification of serum alkaline phosphatase isozymes in the rat by affinity electrophoresis.

The purpose of this study was to examine the possibility of separation and quantification of serum alkaline phosphatase (ALP) isozymes in rats by wheatgerm lectin affinity electrophoresis. Cellulose acetate electrophoresis of the liver and bone ALPs without lectin results in overlapping bands, but in the presence of lectin, the mobility of the band of bone enzyme was retarded and well separated from the liver enzyme band. With this affinity electrophoretic method, we determined the serum ALP isozymes in fed and fasting rats grouped by age. As a result, the absolute activity of bone isozyme showed a downward trend with age in the fed and fasting rats. The serum ALP activity was steadily higher in fed rats than in fasting rats, and the increase was due to intestinal ALP isozyme. There was low activity bordering complete absence in liver isozyme under both nutritional conditions. The affinity electrophoretic method provided a rapid, reproducible, and relatively simple technique for further clinical characterization of ALP isozyme in the rat serum.

Alkaline Phosphatase↗

PubMed1999

Theory of the BOLD effect in the capillary region: an analytical approach for the determination of T2 in the capillary network of myocardium.

This article presents an analytical approach for the quantification of the blood oxygen level dependent (BOLD) effect in the capillary region. The capillary geometry of myocardium is considered. The relaxation rate R*2 is determined as a function of the capillary radius Rc, the intracapillary volume fraction RBV, and the diffusion coefficient D. When the intracapillary volume fraction is small, the approximation R*2 = RBV x tau(-1) x (square root of (1+(taudeltaomega)2)-1) is valid, with the correlation time tau = (Rc2/4D) x (absolute value (ln RBV)/(1 - RBV)). The predictions of this model agree well with numerical simulations and experimental data of others and with data recently measured by our group.

Animals↗

PubMed2006

[Variance of identification of femoral epicondyles in navigated total knee arthroplasty].

BACKGROUND: The aims of this study were the quantification of the accuracy of registration of the epicondylar axis (EA) in navigated total knee arthroplasty (TKA) and the identification of presumed factors influencing this accuracy. METHODS: A total of 32 navigated TKAs were performed and the surgical EA registered. Postoperatively, the difference from the surgical EA determined by computed tomography was calculated. Presumed factors influencing the accuracy were sex, preoperative malalignment, stability and range of motion, operated side, body mass index, and component size. RESULTS: The absolute error was calculated to be 1.4+/-1.3 degrees . Alignment according to the intraoperatively defined axes would have resulted in three outliers (>3 degrees malalignment). The operated side was the only factor showing a significant effect on the accuracy. The absolute error in left knee joints was calculated to be 0.9+/-0.7 degrees (max. 2.4 degrees ) and in right knee joints to be 2.0+/-1.5 degrees (max. 5 degrees, p=0.021). CONCLUSIONS: The surgeon stood on the patient's right side in every case, so that right knee joints were operated from the lateral and left ones from the medial side. A medial position of the surgeon to the knee joint during registration of EA is recommended because it results in a higher accuracy than a lateral position.

Arthroplasty, Replacement, Knee↗

PubMed2000

A simple procedure for quantification of neurite outgrowth based on stereological principles.

The molecular mechanisms controlling formation and remodelling of neuronal extensions are of considerable interest for the understanding of neuronal development and plasticity. Determination of neurite outgrowth in cell culture is a widely used approach to investigate these phenomena. This is generally done by a time consuming tracing of individual neurites and their branches. We have used stereological principles to determine the length of neurites. The total neuritic length per cell was estimated by counting the number of intersections between neurites and test lines of an unbiased counting frame superimposed on images of cell cultures obtained by conventional computer-assisted microscopy. The absolute length, L, of neurites per cell was subsequently estimated from the number of neurite intersections, I, per cell by means of the equation L=(pid/2)I describing the relationship between the number of neurite intersections and the vertical distance, d, between the test lines used. When measuring neurite outgrowth from PC12 cells and primary hippocampal neurons, data obtained by counting neuritic intersections correlated statistically significantly with data obtained using a conventional tracing technique. However, information was acquired more efficiently using the stereological approach. Thus, using the described set-up, the stereological procedure was approximately five times less time consuming than the conventional method based on neurite tracing. The study shows that stereological estimation of neuritic length provides a precise and efficient method for the study of neurite outgrowth in cultures of primary neurons and cell lines.

Animals↗

PubMed2006

Widespread distribution and high abundance of Rhizobium radiobacter within Mediterranean subsurface sediments.

Eastern Mediterranean sediments are characterized by the occurrence of distinct, organic-rich layers, called sapropels. These harbour elevated microbial numbers in comparison with adjacent carbon-lean intermediate layers. A recently obtained culture collection from these sediments was composed of 20% of strains closely related to Rhizobium radiobacter, formerly classified as Agrobacterium tumefaciens. To prove and quantify the in situ abundance of R. radiobacter, a highly specific quantitative polymerase chain reaction (PCR) protocol was developed. To convert quantification results into cell numbers, the copy number of rrn operons per genome was determined. Southern hybridization showed that our isolates contained four operons. Finally, quantitative PCR was applied to 45 sediment samples obtained across the eastern Mediterranean. Rhizobium radiobacter was present in 38 of 45 samples indicating an almost ubiquitous distribution. In total, 25-40 000 cells per gram of sediment were detected, corresponding to 0.001-5.1% of the bacterial cells. In general, the relative and absolute abundance of R. radiobacter increased with depth and was higher in sapropels than in intermediate layers. This indicates that R. radiobacter forms an active population in up to 200 000 years old sapropels. The present study shows for the first time that a cultivated subsurface bacterium is highly abundant in this environment.

Agrobacterium tumefaciens↗

PubMed1992

The ability of gingival crevicular fluid acute phase proteins to distinguish healthy, gingivitis and periodontitis sites.

3 acute phase proteins, from the local gingival inflammatory response, were examined for their ability to distinguish healthy, gingivitis and periodontitis sites. Indirect competitive immunoassays were developed for the quantification of alpha 2-macroglobulin (alpha 2-M) and transferrin (TF), and for alpha 1-antitrypsin (alpha 1-AT), a double antibody sandwich assay was produced. Healthy (25), gingivitis (31) and periodontitis (28) sites were sampled with filter paper strips (2 x 13 mm) and the volume assessed with the Periotron 6000. The samples were eluted in phosphate-buffered saline and analyzed for alpha 2-M, alpha 1-AT and TF. The results were expressed as absolute amounts per sample (ng/30 s) and on a concentration basis (ng/microliter of GCF). Higher GCF absolute amounts of alpha 2-M, alpha 1-AT and TF were consistently obtained from diseased (gingivitis and periodontitis) sites than healthy sites (p less than 0.005). Absolute amounts of GCF alpha 2-M, alpha 1-AT and TF were increased in periodontitis sites over gingivitis sites, although these differences were not statistically significant (p greater than 0.1). When the results were expressed on a concentration basis, alpha 2-M levels from diseased sites were significantly higher than healthy sites (p less than 0.01). In addition, GCF TF concentration was increased in periodontitis compared to healthy sites (p = 0.03).

Enzyme-Linked Immunosorbent Assay↗

PubMed1997

Approaches to determine stoichiometry of viral assembly components.

Due to the rapidity of biological reactions, it is difficult to isolate intermediates or to determine the stoichiometry of participants in intermediate reactions. Instead of determining the absolute amount of each component, this study involved the use of relative parameters, such as dilution factors, percentages probabilities, and slopes of titration curves, that can be more accurately quantified to determine the stoichiometry of components involved in bacteriophage phi29 assembly. This work takes advantage of the sensitive in vitro phage phi29 assembly system, in which 10(8) infectious virions per ml without background can be assembled from eight purified components. It provides a convenient assay for quantification of the stoichiometry of packaging components, including the viral procapsid, genomic DNA, DNA-packaging pRNA, and other structural proteins and enzymes. The presence of a procapsid binding domain and another essential functional domain within the pRNA makes it an ideal component for constructing lethal mutants for competitive procapsid binding. Two methods were used for stoichiometry determination. Method 1 was to determine the combination probability of mutant and wild-type pRNAs bound to procapsids. The probability of procapsids that possess a certain amount of mutant and a certain amount of wild-type pRNA, both with an equal binding affinity, was predicted with the binomial equation [EQUATION IN TEXT] where Z is the total number of pRNAs per procapsid, M is the number of mutant pRNAs bound to one procapsid, and (ZM) is equal to [FORMULA IN TEXT]. With various ratios of mutant to wild-type pRNA in in vitro viral assembly, the percent mutant pRNA versus the yield of virions was plotted and compared to a series of predicted curves to find a best fit. It was determined that five or six copies of pRNA were required for one DNA-packaging event, while only one mutant pRNA per procapsid was sufficient to block packaging. Method 2 involved the comparison of slopes of curves of dilution factors versus the yield of virions. Components with known stoichiometries served as standard controls. The larger the stoichiometry of the component, the more dramatic the influence of the dilution factor on the reaction. A slope of 1 indicates that one copy of the component is involved in the assembly of one virion. A slope larger than 1 would indicate multiple-copy involvement. By this method, the stoichiometry of gp11 in phi29 particles was determined to be approximately 12. These approaches are useful for the determination of the stoichiometry of functional units involved in viral assembly, be they single molecules or oligomers. However, these approaches are not suitable for the determination of exact copy numbers of individual molecules involved if the functional unit is composed of multiple subunits prior to assembly.

Bacillus Phages↗

PubMed1998

Assessing information in T2-weighted MRI scans from secondary progressive MS patients.

BACKGROUND: Magnetic resonance imaging is used routinely for diagnosing MS and for objective assessment of the extent of disease as a marker of treatment efficacy in MS clinical trials. Nevertheless, in many clinical studies only weak correlations have been reported between MRI findings and clinical outcome measures. PURPOSE: The purpose of this study is to compare clinical outcome measures (neurologic scales) with MRI findings (evaluation of T2-weighted MRI scans using a semiautomated quantitative technique and with an independent assessment by a neurologist) in the context of a randomized clinical trial evaluating the efficacy of cladribine for treatment in secondary progressive MS. METHODS: Baseline, 6-month, and 12-month scans from 41 secondary progressive MS patients were examined and ranked in terms of lesion burden from the quantitative assessment and independently in terms of severity by neurologic evaluation. Comparison is made to monthly Expanded Disability Status Scale (EDSS) and Scripps Neurologic Rating Scale (SNRS) determinations in these patients with a nonparametric statistical procedure. RESULTS: Average rank correlations between any of the MRI assessment procedures and either clinical outcome measure were less than 0.15 in absolute magnitude. The average rank correlation between the two MRI assessment procedures was 0.10. There is only a weak degree of association between the MRI assessment procedures and the clinical parameters, although the study has statistical power in excess of 0.90 to find even a moderate level of association between them. CONCLUSIONS: Disease-related activity in T2-weighted scans of secondary progressive MS patients is a multidimensional construct, and is not summarized adequately solely by quantification of overall lesion burden or by assessment of severity. Neither method of summarizing information from T2-weighted scans is strongly related to measures of the clinical course of disease as assessed by the EDSS or SNRS.

Disease Progression↗

PubMed1999

[Quantification of functional retinal damage in branch retinal vein thromboses].

PURPOSE: Branch retinal vein occlusion (BRVO) induces variable functional deficits depending on the grade of vascular occlusion and its localisation. Theses deficiences are not easily defined by visual acuity measurements. However, microperimetry offers topical mapping of retinal function, allowing precise documentation of the intensity and dimension of retinal functional loss in BRVO. METHODS: Retinal sensitivity was examined using a Rodenstock Scanning Laser Ophthalmoscope (SLO). A standardized grading system of stimuli ranging from 0 to 32 dB was used to document the retinal threshold in three different areas: regions presenting vascular occlusion, the collateral edematous zone and adjacent areas with intact perfusion. Absolute and relative scotomas as well as the fixation behavior were studied. RESULTS: Forty-two patients with isolated BRVO within the vascular arcades were examined with microperimetry and angiography. At initial presentation with BRVO the retinal sensitivity in the area of occlusion on average diminished to 4.1 dB. In the collateral edematous zone retinal threshold was reduced to 21.5 dB; area with intact perfusion demonstrated a threshold of 23.2 dB. Within the occluded area itself defects of significantly differing intensity were found which only partially correlated with the angiographic evidence. Intense scotomas (0 dB) were observed in 59% of the eyes examined: angiographically nonperfused areas or extended intraretinal hemorrhage were present. Relative scotomas (12.1 dB) were seen in 19.1% and minimal, non-significant defects (19.5 dB) were documented in 21.4% of the BRVO. The level of angiographically documented leakage did not correlate with the functional deficits present in these two groups. Measurements performed after 6-8 weeks revealed noticeable spontaneous recovery of retinal sensitivity, unless an additional progressive closure occurred. The average functional improvement in the area of leakage found after laser therapy was less than the results shown in spontaneous resolution of edema. CONCLUSIONS: BRVO may lead to significant reductions of central and paracentral retinal function. Angiographically observed leakage is not always directly correlated to the magnitude of retinal sensitivity loss. As spontenous remission is frequent in one group and intact retinal function can be shown in areas of angiographic leakage, therapeutic interventions, e.g., laser treatment, should be carefully considered. Scanning laser ophthalmoscopy provides additional information for precise evaluation and follow-up of the retinal damage in BRVO.

Adult↗

PubMed2006

Simultaneous tracing of 76Se-selenite and 77Se-selenomethionine by absolute labeling and speciation.

Nutritional selenocompounds are transformed into the assumed common intermediate selenide, which is utilized for the synthesis of selenoenzymes or transformed into methylated metabolites for excretion. Hence, selenocompound metabolites can be traced only with labeled selenium. Here we applied a new tracer method for the metallomics of biometals using simultaneous speciation of each metallome labeled with different homo-elemental isotopes to metabolism and availability of selenium. Rats were depleted of endogenous natural abundance selenium by feeding a single selenium stable isotope ((82)Se-selenite) and then administered (76)Se-selenite and (77)Se-selenomethionine ((77)Se-SeMet)simultaneously. Biological samples were subjected to quantification and speciation analysis by HPLC-ICPMS. Metabolites of the labeled (76)Se and (77)Se and interaction with endogenous selenium were traced and examined without interference from the corresponding endogenous natural abundance isotopes. Differences in the distribution and metabolism among organs and between the two nutritional selenocompounds were compared under exactly identical biological and analytical conditions: (1) selenite was distributed more efficiently than SeMet in organs and body fluids except the pancreas. (2) SeMet was taken up by organs in its intact form. (3) Selenium of SeMet origin was distributed selectively in the pancreas and mostly bound to a protein together with intact SeMet. (4) Selenosugars A and B but not trimethylselenonium (TMSe) were detected in the liver. (5) Selenosugar B and TMSe were detected in the kidneys.

Animals↗

PubMed1990

Noninvasive quantification of regional myocardial perfusion with rubidium-82 and positron emission tomography. Exploration of a mathematical model.

Positron emission tomography (PET) centers without cyclotrons use generator-produced rubidium-82 (82Rb) for assessment of myocardial perfusion. The aim of the present study was to determine whether myocardial blood flow could be assessed quantitatively with 82Rb and PET. Because the myocardial extraction fraction of 82Rb varies inversely and nonlinearly with flow and cannot be measured conveniently with PET, we used an experimentally derived mathematical function defining the relation between single-pass extraction fraction of 82Rb and flow to obviate the necessity of measuring the extraction fraction directly. Myocardial blood flow in absolute terms (ml/g/min) was estimated from dynamic PET scans after intravenous administration of 82Rb in intact dogs and compared with flows measured with radiolabeled microspheres. In 36 comparisons in 13 dogs studied at rest, or after coronary occlusion, reperfusion, or after coronary hyperemia induced with intravenous dipyridamole, over the flow range from 0.2 to 2.0 ml/g/min, estimates of perfusion with rubidium correlated well with flows measured concomitantly with microspheres, although there was a slight underestimation of flow with rubidium (flow by 82Rb = 0.92 x flow by microspheres-0.021, r = 0.83). In general, estimates of flow in ischemic regions were less reliable than estimates for regions with normal flow. Thus, although the relation between myocardial extraction and retention of 82Rb and flow can vary under a variety of physiological and pathophysiological conditions, this study demonstrates the ability to obtain quantitative estimates of myocardial blood flow with 82Rb and PET under carefully defined conditions without measuring the extraction fraction directly.

Animals↗