Analysis of Myocardial Time-Activity Curves of 123l-Heptadecanoic Acid II. The Acquisition Time

Optimal fitting of a myocardial time-activity curve is accomplished with a monoexponential plus a constant, resulting in three parameters: amplitude and half-time of the monoexponential and the constant. The aim of this study was to estimate the precision of the calculated parameters. The variability of the parameter values as a function of the acquisition time was studied in 11 patients with cardiac complaints. Of the three parameters the half-time value varied most strongly with the acquisition time. An acquisition time of 80 min was needed to keep the standard deviation of the half-time value within ±10%. To estimate the standard deviation of the half-time value as a function of the parameter values, of the noise content of the time-activity curve and of the acquisition time, a model experiment was used. In most cases the SD decreased by 50% if the acquisition time was increased from 60 to 90 min. A low amplitude/constant ratio and a high half-time value result in a high SD of the half-time value. Tables are presented to estimate the SD in a particular case.

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Analysis of Myocardial Time-Activity Curves of 123I-Heptadecanoic Acid I. Curve Fitting

Nuklearmedizin ◽

10.1055/s-0038-1628897 ◽

1987 ◽

Vol 26 (06) ◽

pp. 241-247 ◽

Cited By ~ 1

Author(s):

F. C. Visser ◽

C. M. B. Duwel ◽

P. D. Bezemer ◽

G. Westera ◽

A. J. P. Karreman ◽

...

Keyword(s):

Curve Fitting ◽

Background Activity ◽

Half Time ◽

Time Activity ◽

Time Value ◽

Fitting Method ◽

Activity Curve ◽

Strong Relation ◽

Curve Fitting Method

Myocardial time-activity curves can be described by two or more parameters. To establish the optimal curve fitting method 33 myocardial time-activity curves were analyzed with different curve fitting methods: monoexponential, biexponential and monoexponential plus constant. A background correction was not applied. Biexponential curve fitting resulted in redundancy of parameters. Optimal curve fitting was obtained with monoexponential plus constant. The constant represents the background activity together with the stored radiolabelled lipids and the half-time value represents the wash-out of radioiodide from the myocardium. A strong relation was found between the constant and the half-time value: small errors in the determination of the constant (background activity) resulted in considerable errors of the half-time value. It is concluded that optimal analysis of a myocardial time-activity curve can be performed with a monoexponential plus constant without earlier correction for background activity.

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The Influence of Lactate and Dipyridamole on Myocardial Fatty Acid Metabolism in Man, Traced with 123l-17-lodo-heptadecanoic Acid

Nuklearmedizin ◽

10.1055/s-0038-1629509 ◽

1990 ◽

Vol 29 (01) ◽

pp. 28-34 ◽

Cited By ~ 1

Author(s):

F. C. Visser ◽

M. J. van Eenige ◽

G. Westera ◽

J. P. Roos ◽

C. M. B. Duwel

Keyword(s):

Fatty Acid ◽

Fatty Acid Metabolism ◽

Acid Metabolism ◽

Time Activity ◽

Time Value ◽

Myocardial Fatty Acid Metabolism ◽

Coronary Vasodilatation ◽

Activity Curve ◽

Normal Human ◽

Plasma Lactate Level

Changes in myocardial metabolism can be detected externally by registration of time-activity curves after administration of radioiodinated fatty acids. In this scintigraphic study the influence of lactate on fatty acid metabolism was investigated in the normal human myocardium, traced with 123l-17-iodoheptadecanoic acid (123l-17-HDA). In patients (paired, n = 7) lactate loading decreased the uptake of 123l-17-HDA significantly from 27 (control: 22-36) to 20 counts/min/pixel (16-31; p <0.05 Wilcoxon). The half-time value increased to more than 60 rriin (n = 5), oxidation decreased from 61 to 42%. Coronary vasodilatation, a well-known side effect of lactate loading, was studied separately in a dipyridamole study (paired, n = 6). Coronary vasodilatation did not influence the parameters of the time-activity curve. These results suggest that changes in plasma lactate level as occurring, among other effects, during exercise will influence the parameters of dynamic 123l-17-HDA scintigraphy of the heart.

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Simulation study of a coincidence detection system for non-invasive determination of arterial blood time-activity curve measurements

EJNMMI Physics ◽

10.1186/s40658-020-00297-9 ◽

2020 ◽

Vol 7 (1) ◽

Author(s):

Yassine Toufique ◽

Othmane Bouhali ◽

Pauline Negre ◽

Jim O’ Doherty

Keyword(s):

Simulation Study ◽

Detection System ◽

Coincidence Detection ◽

Time Activity ◽

Time Activity Curve ◽

Non Invasive ◽

Arterial Blood ◽

Activity Curve

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Reliability of radionuclide gastroesophageal reflux studies using visual and time-activity curve analysis: inter-observer and intra-observer variation and description of minimum detectable reflux

Nuclear Medicine Communications ◽

10.1097/00006231-200304000-00012 ◽

2003 ◽

Vol 24 (4) ◽

pp. 421-428 ◽

Cited By ~ 7

Author(s):

M. CAGLAR ◽

B. VOLKAN ◽

R. ALPAR

Keyword(s):

Gastroesophageal Reflux ◽

Observer Variation ◽

Curve Analysis ◽

Time Activity ◽

Time Activity Curve ◽

Activity Curve

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Impulse-response function of splanchnic circulation with model-independent constraints: theory and experimental validation

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.00054.2003 ◽

2003 ◽

Vol 285 (4) ◽

pp. G671-G680 ◽

Cited By ~ 15

Author(s):

Ole L. Munk ◽

Susanne Keiding ◽

Ludvik Bass

Keyword(s):

Portal Vein ◽

Impulse Response ◽

Response Function ◽

Mean Transit Time ◽

Impulse Response Function ◽

Parameter Estimates ◽

Time Activity ◽

Time Activity Curve ◽

Transit Times ◽

Activity Curve

Modeling physiological processes using tracer kinetic methods requires knowledge of the time course of the tracer concentration in blood supplying the organ. For liver studies, however, inaccessibility of the portal vein makes direct measurement of the hepatic dual-input function impossible in humans. We want to develop a method to predict the portal venous time-activity curve from measurements of an arterial time-activity curve. An impulse-response function based on a continuous distribution of washout constants is developed and validated for the gut. Experiments with simultaneous blood sampling in aorta and portal vein were made in 13 anesthetized pigs following inhalation of intravascular [15O]CO or injections of diffusible 3- O-[11C]methylglucose (MG). The parameters of the impulse-response function have a physiological interpretation in terms of the distribution of washout constants and are mathematically equivalent to the mean transit time ( T̄) and standard deviation of transit times. The results include estimates of mean transit times from the aorta to the portal vein in pigs: T̄ = 0.35 ± 0.05 min for CO and 1.7 ± 0.1 min for MG. The prediction of the portal venous time-activity curve benefits from constraining the regression fits by parameters estimated independently. This is strong evidence for the physiological relevance of the impulse-response function, which includes asymptotically, and thereby justifies kinetically, a useful and simple power law. Similarity between our parameter estimates in pigs and parameter estimates in normal humans suggests that the proposed model can be adapted for use in humans.

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