scholarly journals Two-Compartment Exchange Model for Perfusion Quantification Using Arterial Spin Tagging

2001 ◽  
Vol 21 (4) ◽  
pp. 440-455 ◽  
Author(s):  
Jinyuan Zhou ◽  
David A. Wilson ◽  
John A. Ulatowski ◽  
Richard J. Traystman ◽  
Peter C. M. van Zijl
Keyword(s):  
Signal Intensity ◽  
Water Exchange ◽  
Compartment Model ◽  
Intensity Difference ◽  
Tissue Water ◽  
Spin Tagging ◽  
Tissue Space ◽  
Perfusion Quantification ◽  
The Individual ◽  
Limited Water Exchange

The original well-mixed tissue model for the arterial spin tagging techniques is extended to a two-compartment model of restricted water exchange between microvascular (blood) and extravascular (tissue) space in the parenchyma. The microvascular compartment consists of arterioles, capillaries, and venules, with the blood/tissue water exchange taking place in the capillaries. It is shown that, in the case of limited water exchange, the individual FAIR (Flow-sensitive Alternating Inversion Recovery) signal intensities of the two compartments are comparable in magnitude, but are not overlapped in time. It is shown that when the limited water exchange is assumed to be fast, flows quantified from the signal-intensity difference are underestimated, an effect that becomes more significant for larger flows and higher magnetic field strengths. Experimental results on cat brain at 4.7 T comparing flow data from the FAIR signal-intensity difference with those from microspheres over a cerebral blood flow range from 15 to 150 mL 100 g−1 min−1 confirm these theoretic predictions. FAIR flow values with correction for restricted exchange, however, correlate well with the radioactive microsphere flow values. The limitations of the approach in terms of choice of the intercompartmental exchange rates are discussed.

Influence of stable iodine on the uptake of the thyroid – model vs. experiment

2001 ◽  
Vol 40 (01) ◽  
pp. 31-37 ◽  
Author(s):  
U. Wellner ◽  
E. Voth ◽  
H. Schicha ◽  
K. Weber
Keyword(s):  
Time Course ◽  
Compartment Model ◽  
The Body ◽  
Iodine Uptake ◽  
Model Calculations ◽  
Physiological Conditions ◽  
Iodine Supply ◽  
Predicted Values ◽  
The Individual ◽  
Stable Iodine

Summary Aim: The influence of physiological and pharmacological amounts of iodine on the uptake of radioiodine in the thyroid was examined in a 4-compartment model. This model allows equations to be derived describing the distribution of tracer iodine as a function of time. The aim of the study was to compare the predictions of the model with experimental data. Methods: Five euthyroid persons received stable iodine (200 μg, 10 mg). 1-123-uptake into the thyroid was measured with the Nal (Tl)-detector of a body counter under physiological conditions and after application of each dose of additional iodine. Actual measurements and predicted values were compared, taking into account the individual iodine supply as estimated from the thyroid uptake under physiological conditions and data from the literature. Results: Thyroid iodine uptake decreased from 80% under physiological conditions to 50% in individuals with very low iodine supply (15 μg/d) (n = 2). The uptake calculated from the model was 36%. Iodine uptake into the thyroid did not decrease in individuals with typical iodine supply, i.e. for Cologne 65-85 μg/d (n = 3). After application of 10 mg of stable iodine, uptake into the thyroid decreased in all individuals to about 5%, in accordance with the model calculations. Conclusion: Comparison of theoretical predictions with the measured values demonstrated that the model tested is well suited for describing the time course of iodine distribution and uptake within the body. It can now be used to study aspects of iodine metabolism relevant to the pharmacological administration of iodine which cannot be investigated experimentally in humans for ethical and technical reasons.

scholarly journals The triangular fibrocartilage complex on high-resolution 3 T MRI in healthy adolescents: the thin line between asymptomatic findings and pathology

2021 ◽  
Author(s):  
Anne-Sophie van der Post ◽  
Sjoerd Jens ◽  
Frank F. Smithuis ◽  
Miryam C. Obdeijn ◽  
Roelof-Jan Oostra ◽  
...  
Keyword(s):  
Signal Intensity ◽  
Sagittal Plane ◽  
Articular Surface ◽  
Triangular Fibrocartilage Complex ◽  
Ulnar Variance ◽  
Observer Agreement ◽  
Mri Findings ◽  
Mri Features ◽  
Triangular Fibrocartilage ◽  
The Individual

Abstract Objective The objective of the study is to provide a reference for morphology, homogeneity, and signal intensity of triangular fibrocartilage complex (TFCC) and TFCC-related MRI features in adolescents. Materials and methods Prospectively collected data on asymptomatic participants aged 12–18 years, between June 2015 and November 2017, were retrospectively analyzed. A radiograph was performed in all participants to determine skeletal age and ulnar variance. A 3-T MRI followed to assess TFCC components and TFCC-related features. A standardized scoring form, based on MRI definitions used in literature on adults, was used for individual assessment of all participants by four observers. Results per item were expressed as frequencies (percentages) of observations by all observers for all participants combined (n = 92). Inter-observer agreement was determined by the unweighted Fleiss’ kappa with 95% confidence intervals (95% CI). Results The cohort consisted of 23 asymptomatic adolescents (12 girls and 11 boys). Median age was 13.5 years (range 12.0–17.0). Median ulnar variance was −0.7 mm (range − 2.7–1.4). Median triangular fibrocartilage (TFC) thickness was 1.4 mm (range 0.1–2.9). Diffuse increased TFC signal intensity not reaching the articular surface was observed in 30 (33%) observations and a vertical linear increased signal intensity with TFC discontinuation in 19 (20%) observations. Discontinuation between the volar radioulnar ligament and the TFC in the sagittal plane was seen in 23 (25%) observations. The extensor carpi ulnaris was completely dislocated in 10 (11%) observations, more frequent in supinated wrists (p = 0.031). Inter-observer agreement ranged from poor to fair for scoring items on the individual TFCC components. Conclusion MRI findings, whether normal variation or asymptomatic abnormality, can be observed in TFCC and TFCC-related features of asymptomatic adolescents. The rather low inter-observer agreement underscores the challenges in interpreting these small structures on MRI. This should be taken into consideration when interpreting clinical MRIs and deciding upon arthroscopy.

Limited water exchange production systems for freshwater ornamental fish

2003 ◽  
Vol 34 (11) ◽  
pp. 937-941 ◽  
Author(s):  
Lena Asano ◽  
Harry Ako ◽  
Eri Shimizu ◽  
Clyde S Tamaru
Keyword(s):  
Water Exchange ◽  
Production Systems ◽  
Ornamental Fish ◽  
Limited Water Exchange

scholarly journals One-tissue compartment model for myocardial perfusion quantification with N-13 ammonia PET provides matching results: A cross-comparison between Carimas, FlowQuant, and PMOD

2021 ◽  
Author(s):  
Sergey V. Nesterov ◽  
Roberto Sciagrà ◽  
Luis Eduardo Juarez Orozco ◽  
John O. Prior ◽  
Leonardo Settimo ◽  
...  
Keyword(s):  
Myocardial Perfusion ◽  
Compartment Model ◽  
Regional Level ◽  
Maximum Difference ◽  
Global Level ◽  
Significant Variability ◽  
Tissue Compartment ◽  
Software Packages ◽  
Perfusion Quantification ◽  
Pet Scans

Abstract Purpose To cross-compare three software packages (SPs)—Carimas, FlowQuant, and PMOD—to quantify myocardial perfusion at global, regional, and segmental levels. Materials and Methods Stress N-13 ammonia PET scans of 48 patients with HCM were analyzed in three centers using Carimas, FlowQuant, and PMOD. Values agreed if they had an ICC > 0.75 and a difference < 20% of the median across all observers. Results When using 1TCM on the global level, the agreement was good, and the maximum difference between 1TCM MBF values was 17.2% (ICC = 0.83). On the regional level, the agreement was acceptable except in the LCx region (25.5% difference, ICC = 0.74) between FlowQuant and PMOD. Carimas-1TCM agreed well with PMOD-1TCM and FlowQuant-1TCM. Values obtained with FlowQuant-1TCM had a somewhat lesser agreement with PMOD-1TCM, especially at the segmental level. Conclusions The global and regional MBF values (with one exception) agree well between the different software packages. There is significant variability in segmental values, mainly located in the LCx region and segments. Out of the studied tools, Carimas can be used interchangeably with both PMOD and FlowQuant for 1TCM implementation on all levels—global, regional, and segmental.

Pharmacokinetics and Tissue Residues of Sulfathiazole and Sulfamethazine in Pigs

1994 ◽  
Vol 57 (9) ◽  
pp. 796-801 ◽  
Author(s):  
LIEVE S. G. VAN POUCKE ◽  
CARLOS H. VAN PETEGHEM
Keyword(s):  
Intravenous Injection ◽  
Half Life ◽  
Intramuscular Injection ◽  
Compartment Model ◽  
Absolute Bioavailability ◽  
Pharmacokinetic Parameters ◽  
Tissue Concentrations ◽  
Single Intravenous Injection ◽  
The Individual ◽  
Residue Study

The plasma pharmacokinetics and tissue penetration of sulfathiazole (ST) and sulfamethazine (SM) after intravenous and intramuscular injection in pigs were studied. Following a single intravenous dose of 40 mg ST/kg of bodyweight or 80 mg SM/kg of bodyweight, the plasma ST and SM concentrations were best fitted to a two-compartment model. The areas under the curve were 447 ± 39 and 1485 ± 41 mg/h/L, clearances were 0.090 ± 0.007 and 0.054 ± 0.001 L/kg/h, volumes of distribution were 1.16 ± 0.16 and 0.77 ± 0.06 L/kg, half-lifes in distribution phase were l.18 ± 0.57 and 0.23 ± 0.16 h and half-lifes in eliminations phase were 9.0 ± l.6 and 9.8 ± 0.6 h. When the two compounds were administered simultaneously as a single intravenous injection, the pharmacokinetic parameters for ST were not significantly different. The values for SM show statistical differences for some important parameters: α, β and the AUC0–&gt;∞ were significantly decreased and t1/2α, Vd and CIB were significantly increased. It can be concluded that after a single intravenous injection of 40 mg/kg, sulfathiazole has a high tl/2β resulting in higher tissue concentrations. This half-life, which is higher than what is reported in the literature, is not influenced by the simultaneous presence of sulfamethazine. The tl/2β for sulfamethazine after a single intravenous injection of 80 mg/kg is comparable to the data from the literature and is not influenced by the presence of sulfathiazole. Sulfathiazole and SM were also administered simultaneously as an intramuscular injection to healthy pigs at a dosage of 40 and 80 mg/kg bodyweight. Pharmacokinetic experiments were conducted on three pigs. From this pharmacokinetic study it can be concluded that upon a single intramuscular administration of 40 mg/kg of ST and 80 mg/kg of SM the absolute bioavailability in pigs is 0.92 ± 0.04 for ST and l.01 ± 0.07 for SM. Six pigs received five intramuscular im) injections as a single dose of ST and SM every 24 h for five consecutive days for the residue study. The pigs were slaughtered at different times after the last dose was given and samples were taken from various tissues and organs. Concentrations were determined by a microbiological method and a HPTLC method. No edible tissue contained more than 100 μg/kg of the individual sulfonamides after 10 days of withdrawal. It means that adult animals which have a shorter half-life and thus lower tissue concentrations will certainly meet the economic community EC) maximum residue limits after a 10 days withdrawal period.

scholarly journals WATER EXCHANGE IN THE ESTUARY OF THE RAZDOLNAYA RIVER (AMUR BAY, JAPAN SEA) IN THE ICE COVERED PERIOD

2019 ◽  
Vol 196 ◽  
pp. 123-137 ◽  
Author(s):  
P. Yu. Semkin ◽  
P. Ya. Tishchenko ◽  
V. B. Lobanov ◽  
Yu. A. Barabanshchikov ◽  
T. A. Mikhailik ◽  
...  
Keyword(s):  
Water Exchange ◽  
Salt Water ◽  
Groundwater Discharge ◽  
River Mouth ◽  
Japan Sea ◽  
Bottom Layer ◽  
Additional Source ◽  
Flow Through ◽  
Limited Water Exchange ◽  
Annual Discharge

Environmental conditions in the Razdolnaya/Suifen Estuary and adjacent marine area were monitored from 2008 to 2018, by seasons, including winter observations in January 2014 and January 2018. The river discharge in winter was low: 6 m3 /s (mean annual discharge is 73 m3 /s). The estuary was covered by ice. The cline of salt water at the bottom was traced upstream up to 28 km from the river mouth. The currents in the estuary changed in tidal cycle. Increasing of salinity and temperature (> 2о ) at the bottom was observed in the distance 20–24 km from the river bar (this area was distinguished by relatively thin ice, 20 cm, against 40–70 cm in the rest of estuary). Modeling of the water balance in the estuary showed an additional source of salt water in the internal estuary, beyond the direct exchange with the sea over the river bar, that was presumably the water flow through the aquifer. This groundwater discharge was responsible for supporting of the salted bottom layer and for temperature and salinity increasing in the internal estuary during the ebb phase in conditions of limited water exchange by two-layered estuarine circulation because of ice cover at the river mouth.

Design and clinical application of the ‘styloidectome’ styloid process cutter

2006 ◽  
Vol 120 (9) ◽  
pp. 753-758 ◽  
Author(s):  
W Zhibin ◽  
J Min
Keyword(s):  
Blood Loss ◽  
General Anaesthesia ◽  
Local Anaesthesia ◽  
Styloid Process ◽  
Morphological Data ◽  
Clinical Use ◽  
Deep Tissue ◽  
Tissue Space ◽  
Oral Approach ◽  
The Individual

A styloid process (SP) cutter was developed and put into clinical use. The design of components of the ‘styloidectome’ was based on the principles of mechanics. The measurements of the individual parts were determined on the basis of morphological data of the oropharynx from 40 subjects undergoing tonsillectomy under general anaesthesia. Experiments showed that the instrument could be used to transect the SP and excise the amputated bones from the deep tissue space. We used the instrument for the resection of elongated SPs, via an oral approach, in seven in-patients (involving 10 SPs) under general anaesthesia and in two out-patients (involving three SPs) under local anaesthesia. The length of the resected SP ranged from 0.8 to 2.5 cm and the stump of the SP was smooth. The removal lasted only seconds and blood loss was minimal, without any complications. The styloidectome was reliable, easy to use and could be used for the resection of an elongated SP under general or local anaesthesia.

scholarly journals O09 Drug delivery kinetics of intravenous gentamicin in a population of neonates

2019 ◽  
Vol 104 (6) ◽  
pp. e4.2-e4
Author(s):  
G Salis ◽  
N Medlicott ◽  
D Reith
Keyword(s):  
Drug Delivery ◽  
Time Lag ◽  
Medical Science ◽  
Compartment Model ◽  
Pharmacokinetic Parameters ◽  
List Type ◽  
First Order ◽  
Model Drug ◽  
The Individual ◽  
Kinetics Of

BackgroundGentamicin is commonly used in the NICU setting and is often administered via long lines, which increases variability in the rate of administration. We aimed to model drug delivery pharmacokinetic parameters for intravenous gentamicin administered via umbilical venous catheters (UVCs).MethodsData was modelled from infusion simulations of gentamicin delivery using UVCs with a background flow rate of 0.5 ml/h.1 Different combinations of dose (2 mg, 5 mg) were given by bolus injection over 3–5 minutes, followed by a normal saline flush (1 ml, 2 ml). Gentamicin levels were measured at 5 minute intervals over an hour via high pressure liquid chromatography.Phoenix Certara (version 8.1) was used for modelling. An extravascular model with clearance removed was used to predict parameters: absorption constant (Ka), time lag (Tlag), and bioavailability (F). F was used to enable an estimate of the variability in dose administered. Different error models were tested to ascertain which best described the data.ResultsAn extravascular one compartment model with first order absorption and additive error best described the data. Estimates for the model with a 2 mg dose and 1 ml flush were Ka 0.34L/min, Tlag 1.28min, F 0.97, standard deviation (stdev) 0.14. For 2 mg, 2 ml flush, estimates were Ka 0.86L/min, Tlag 3.01min, F 0.87, stdev 0.01. For 5 mg, 1 ml flush, estimates were Ka 0.48L/min, Tlag 3.13min, F 1.03, stdev 0.12. For 5 mg, 2 ml flush, estimates were Ka 0.83L/min, Tlag 3.29min, F 1.09, stdev 0.02. For each model epsshrinkage and nshrinkage for Tlag and F were low, however nshrinkage for ka was 0.9999.ConclusionThis is the first known modelling of gentamicin delivery kinetics. The studies all had high nshrinkage for Ka, therefore the individual estimates of ka may be unreliable. Further studies with a higher number of replicates would provide more favourable data for estimating Ka.ReferenceLala AC ( 2016). Variability in neonatal gentamicin administration influencing drug delivery kinetics (Thesis, Master of Medical Science). University of Otago.Disclosure(s)No conflict of interest declared. Funding for research via the Freemasons Society of New Zealand.

Non–steady State Analysis of the Pharmacokinetic Interaction between Propofol and Remifentanil

2002 ◽  
Vol 97 (6) ◽  
pp. 1350-1362 ◽  
Author(s):  
Thomas Bouillon ◽  
Joergen Bruhn ◽  
Lucian Radu-Radulescu ◽  
Edward Bertaccini ◽  
Sang Park ◽  
...  
Keyword(s):  
Pharmacokinetic Interaction ◽  
Compartment Model ◽  
Significant Degree ◽  
Volume Of Distribution ◽  
Gas Chromatography Mass Spectrometry ◽  
Effect Compartment ◽  
Drug Concentrations ◽  
Time Courses ◽  
Elimination Clearance ◽  
The Individual

Background The pharmacokinetics of both propofol and remifentanil have been described extensively. Although they are commonly administered together for clinical anesthesia, their pharmacokinetic interaction has not been investigated so far. The purpose of the current investigation was to elucidate the nature and extent of pharmacokinetic interactions between propofol and remifentanil. Methods Twenty healthy volunteers aged 20-43 yr initially received either propofol or remifentanil alone in a stepwise incremental and decremental fashion a target controlled infusion. Thereafter, the respective second drug was infused to a fixed target concentration in the clinical range (0-4 microg/ml and 0-4 ng/ml for propofol and remifentanil, respectively) and the stepwise incremental pattern repeated. Frequent blood samples were drawn for up to 6 h for propofol and 40 min for remifentanil after the end of administration and assayed for the respective drug concentrations with gas chromatography-mass spectrometry. The time courses of the measured concentrations were fitted to standard compartmental models. Calculations were performed with NONMEM. After having established the individual population models for both drugs and an exploratory analysis for hypothesis generation, pharmacokinetic interaction was identified by including an interaction term into the population model and comparing the value of the objective function in the presence and absence of the respective term. Results The concentration-time courses of propofol and remifentanil were described best by a three- and two-compartment model, respectively. In the concentration range examined, remifentanil does not alter propofol pharmacokinetics. Coadministration of propofol decreases the central volume of distribution and distributional clearance of remifentanil by 41% and elimination clearance by 15%. This effect was not concentration-dependent in the examined concentration range of propofol. Conclusions Coadministration of propofol decreases the bolus dose of remifentanil needed to achieve a certain plasma-effect compartment concentration but does not alter the respective maintenance infusion rates and recovery times to a clinically significant degree.

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