Signal intensity versus time curves

Fig. 1.2.2a,b. Functional evaluation for 3-month-old boy shown in Figure 1.2.1. a Relative signal intensity versus time curve showing curves for the aorta and both kidneys. Note the symmetric parenchymal curves with equivalent perfusion, concentration and excretion of contrast agent, b The Patlak plot is used as an index of the individual kidney GFR. The slope of each plot reflects the GFR of each kidney (12.7 ml/min on left and 12.1 ml/min on right). They intercept represents the fractional blood volume of each kidney. The body surface area corrected Patlak (BSA Patlak) is 102 ml/min. The Patlak DRF is calculated at 50 50... 

The parameters routinely assessed by MR urography include the overall anatomic diagnosis, vDRF and pDRF, renal and calyceal transit times, signal intensity versus time curves and individual GFR index for each kidney. 

An optical cell for pressures of up to 200 MPa and temperatures to 200°C is presented in Chapter 4.3.4. The cell can be coupled with a commercial Raman spectrometer to measure the course of the intensity of a bond s signal with time. By calibration, the intensity versus time curve can be converted into a concentration versus time curve, from which the rate of reaction and kinetic parameters can be evaluated. The method is explained in Chapter 3.3.2, considering the decomposition of an organic peroxide. 

The "add-to-memory" signal averaging method currently available to us distorts fluorescence intensity versus time plots when the fluorescence intensity is a non-linear function of incident laser energy and the laser energy varies from shot to shot. For this reason we have not attempted detailed kinetic modelling of the observed fluorescence intensity decay curves recorded at high 532 nm laser fluence. 

CTP is a relatively recent development in acute stroke imaging that is already in routine clinical use in many centers. CTP and MRP are similar in that both techniques are based on rapid serial image acquisition during intravenous injection of a bolus of contrast material. In both techniques, measurements of density over time (for CTP) or signal intensity over time (for MRP) are converted to contrast agent-versus-time curves, and these are processed in similar ways to yield the same perfusion measurements (most often CBV, CBF, and MTT). Example CTP images are shown in Figure 2.12. 

Alternatively, the signal can be injected as a pulse (ideally infinitely narrow so that its width = 0 while its area = 1), the broadening of which is observed when, with a certain delay, the dyed zone has reached the vessel output. The formalized plot of the observed concentrations C versus time is called a C curve, and its shape characterizes the type of flow (Fig. 3.2 ). For plug flow the input and output pulses have the same shape for mixed flow, after an abrupt rise, the color intensity decreases expo-... 

If one were to start with a greater amount of target DNA, a significant increase in fluorescence signal will appear more quickly, which would be reflected by a lower C, value. The curve of fluorescence intensity versus cycle number for standard samples of known concentrations can be used to generate data that can be used to determine the starting concentrations of unknown samples. This technique is termed real-time quantitative PCR, or qPCR. 

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