Response Time and Flow Sensitivity of Detectors for Gas Chromatography

Schmauch, L. J.

doi:10.1021/ac60146a021

Cited by 82 publications

(23 citation statements)

References 8 publications

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“…ROI data were fitted by means of a nonlinear regression analysis method based on Marquardt algorithm, according to an exponentially modified Gaussian (EMG) equation, to generate fitted time-intensity curves (fTICs) (9,13,14): The EMG equation serves as a distribution fitting function, used in pharmacokinetic theories for ''narrow peak'' or ''broaden peak'' signal data, most widely applied in chromatography and flow injection analysis for the diffusion of a tracer in a two-compartment model (15,16). Considering marrow perfusion, EMG can be viewed as a sharp and narrow width Gaussian pulse function when contrast perfuses into the plasma (bolus phase), it reshapes in time with a broadened exponentially modified Gaussian shape when contrast perfuses from plasma to the extravascular-extracellular space (EES) (wash-in phase) and then from the EES to the plasma (wash-out phase).…”

Section: Mri Data Handling and Image Analysismentioning

confidence: 99%

Degenerative endplate changes of the lumbosacral spine: Dynamic contrast‐enhanced MRI profiles related to age, sex, and spinal level

Savvopoulou

Maris²,

Κουρέας

et al. 2011

Magnetic Resonance Imaging

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Purpose: To investigate differences in perfusion profiles between degenerative endplate marrow changes and normal vertebral marrow in relation to spinal level, age, and sex with dynamic contrast-enhanced magnetic resonance imaging (DCE MRI).Materials and Methods: Ninety-two consecutive patients referred for evaluation of low back pain or sciatica, without history of malignant or chronic disease, underwent conventional and DCE MRI of the lumbosacral spine. Fifty-two of them demonstrated degenerative endplate marrow changes. Regions of interest were placed on sites of normal marrow (group A) and degenerative changes (group B) on subtracted images. Fitted time-intensity curves (fTICs) were generated and evaluated for curve pattern. Both groups were stratified into upper (L1-L2) and lower (L3-I1) levels, males and females younger or older than 50 years. Perfusion parameters were calculated and statistically compared for both groups and subgroups. Receiver operator curve (ROC) analysis was also performed.Results: Two fTIC patterns were identified. Perfusion parameters of degenerative changes and normal marrow differed significantly, even when groups were stratified for spinal level, age, and sex (P < 0.05). A time to peak value >108 seconds was characteristic for degenerative changes with sensitivity 69.5% and specificity 84.6%.Conclusion: DCE MRI profiles of degenerative endplate marrow changes of the lumbosacral spine differ significantly from normal marrow regardless of spinal level, age, or sex.

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Section: Mri Data Handling and Image Analysismentioning

confidence: 99%

Degenerative endplate changes of the lumbosacral spine: Dynamic contrast‐enhanced MRI profiles related to age, sex, and spinal level

Savvopoulou

Maris²,

Κουρέας

et al. 2011

Magnetic Resonance Imaging

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“…This value was used as a threshold for the estimation of goodness of each fit. EMG function (Equation [1]) fits in most pharmacokinetic theories, and it is basically applied to signal data present in chromatography and flow injection analysis for the diffusion of tracers or markers (22,23). EMG (Equation [1]) initially starts forming a ''narrow-peak'' Gaussian impulse function which corresponds to the first seconds arterial bolus phase with the paramagnetic tracer inside the blood plasma.…”

Section: Mri Quantitative Image and Data Analysismentioning

confidence: 99%

Perfusion parameters analysis of the vertebral bone marrow in patients with Ph¹⁻ chronic myeloproliferative neoplasms (Ph^negMPN): A dynamic contrast‐enhanced MRI (DCE‐MRI) study

Courcoutsakis

Spanoudaki

Maris

et al. 2011

Magnetic Resonance Imaging

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Purpose: To evaluate perfusion parameters of the vertebral bone marrow in patients with Philadelphia negative chronic myeloproliferative neoplasms (Ph neg MPN) using dynamic contrast-enhanced MRI (DCE-MRI). Materials and Methods:The study enrolled 24 patients with Ph neg MPN: 12 patients with myelofibrosis (Group A), 6 with essential thrombocythemia (ET), and 6 with polycythemia vera (PV) (Group B) who underwent DCE-MRI of the lumbosacral spine. Twelve normal individuals served as control group (Group C). Wash-in (WIN), wash-out (WOUT), maximum contrast-enhancement (CE max ), timeto-peak (TTPK), time-to-maximum slope (TMSP), and the WIN/TMSP ratio (WTSP) were calculated.Results: WIN, CE max , and WTSP parameters were higher in Group A than in Group C (P < 0.05). These parameters were significant (P < 0.0001) in discriminating patients with myelofibrosis from normal individuals with sensitivities 74.14%, 87.93%, 74.14%, and specificities 91.07%, 83.93%, 91.07%, respectively. WIN, WOUT, CE max , and WTSP parameters were higher in Group A than in Group B (P < 0.05). Group B exhibited no differences in perfusion parameters as compared with Group C with the exception of WOUT. Conclusion:Patients with myelofibrosis exhibited increased perfusion parameters in vertebral bone marrow, which could be consisted with increased vascularity, probably related to neoangiogenesis as opposed to ET or PV patients showing no increased perfusion. DCE-MRI may be of value in discriminating subgroups of Ph neg MPN patients and in indicating those progressing to myelofibrosis.

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“…Isto se deve à velocidade finita com a qual o circuito eletrônico responde a uma variação do sinal proveniente do transdutor [11,[32][33][34] . Uma vez que grande parte do circuito elétrico é composta de resistores associados com capacitores (circuitos RC), como mostrado na Figura 4, tais circuitos responderão a um estí-mulo elétrico de forma exponencial.…”

Section: Dispersão No Detectorunclassified

Cromatografia líquida capilar: 2. Alargamento das bandas por efeitos extracoluna

Coutinho¹,

Lanças

2011

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ResumoO alargamento da banda é um fator altamente indesejável em todas as técnicas cromatográficas, uma vez que diminui a eficiência da coluna (menor número de pratos, N) e deteriora a resolução (menor Rs). Este efeito é particularmente crítico na cromatografia líquida capilar (c-LC) devido aos pequenos volumes da instrumentação, conexões, colunas, etc., empregados na técnica. Como parte de uma série de artigos a respeito da c-LC, neste trabalho serão abordados os principais fatores que ocasionam o alargamento das bandas cromatográficas em c-LC, assim como a maneira de evitá-lo. Palavras-chaveCromatografia líquida capilar; alargamento de bandas; fatores extra coluna; micro LC; LC capilar. Capillary liquid chromatography: 2. Band broadening due to extracolumn effects AbstractBand broadening is one of the major factors to be avoided in chromatographic techniques, once it decreases the column efficiency (the number of plates, N) and deteriorates the Resolution (Rs). This effect is particularly critical in capillary liquid chromatography due to the very low volumes, instrumentation, connections and columns employed in this technique. As a part in a series of papers dealing with c-LC, this work describes the major factors responsible for band broadening in chromatography, as well as the ways to minimize it.

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Response Time and Flow Sensitivity of Detectors for Gas Chromatography

Cited by 82 publications

References 8 publications

Degenerative endplate changes of the lumbosacral spine: Dynamic contrast‐enhanced MRI profiles related to age, sex, and spinal level

Degenerative endplate changes of the lumbosacral spine: Dynamic contrast‐enhanced MRI profiles related to age, sex, and spinal level

Perfusion parameters analysis of the vertebral bone marrow in patients with Ph¹⁻ chronic myeloproliferative neoplasms (Ph^negMPN): A dynamic contrast‐enhanced MRI (DCE‐MRI) study

Cromatografia líquida capilar: 2. Alargamento das bandas por efeitos extracoluna

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Response Time and Flow Sensitivity of Detectors for Gas Chromatography

Cited by 82 publications

References 8 publications

Degenerative endplate changes of the lumbosacral spine: Dynamic contrast‐enhanced MRI profiles related to age, sex, and spinal level

Degenerative endplate changes of the lumbosacral spine: Dynamic contrast‐enhanced MRI profiles related to age, sex, and spinal level

Perfusion parameters analysis of the vertebral bone marrow in patients with Ph1− chronic myeloproliferative neoplasms (PhnegMPN): A dynamic contrast‐enhanced MRI (DCE‐MRI) study

Cromatografia líquida capilar: 2. Alargamento das bandas por efeitos extracoluna

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Perfusion parameters analysis of the vertebral bone marrow in patients with Ph¹⁻ chronic myeloproliferative neoplasms (Ph^negMPN): A dynamic contrast‐enhanced MRI (DCE‐MRI) study