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The experiment demonstrates the performing of blood flow examinations by means of the ultrasonic Doppler method.
Doppler sonography is based on the effect of the frequency shift between the sent and the received ultrasonic signal in a sender-transmitter system in which transmitter and receiver are moving in relation to each other. In the experiment, blood flow is investigated by means of a Doppler probe at a realistic arm phantom.
In addition to continuous mode the pump used can also be operated in a pulsatile mode to simulate arterial blood flow.
The measurement software provides different windows for the analysis and visualisation of the recorded Doppler signals.
Introduction Mechanisms of controlled release Intelligent controlled release DDS Examples Recent advances References. Targeted delivery It has goal of delivering the drug to specific cell types, tissues or organs. Modulated release Release of drug at a variable rate controlled by Environmental conditions, Biofeedback, Sensor input External control device.
Diffusion controlled release system (monolithic matrix device) In monolithic devices, the drug is uniformly dispersed or dissolved in the polymer, and it is released by diffusion from the polymer as shown in Figure.

Combined reservoir – monolithic system Initially the active agent must diffuse across the membrane, as the time passes the outer layers of the monolithic reservoir are depleted, the agent travels through the monolithic material and the membrane sequentially.
COMBINED RESERVOIR-MONOLITHIC SYSTEMS Monolithic Matrix (phase II) Outer membrane (phase I) Agent loaded Matrix layer Agent depleted Matrix layer Initially the release rate of diffusion through the phase 1,as the time progress,a layer depleted from the active agent is generated in phase 11 reservoir material immediately adjacent to the membrane layer.
Matrix dissolution control In this approach drug is dispersed in slow dissolving matrix consisted of polymer. DIFFUSION & DISSOLUTION CONTROLLED SYSTEMS Release rate is dependent on surface area diffusion coefficient of drug though pore in coating conc. WATER PENETRATION CONTROLLED SYSTEMS rate control is obtained by penetration of water into the system.
SWELLING CONTROLLED SYSTEM The system is initially dry & when placed into any body fluid, it absorbs the fluid & swells.
The differences between continuous venous and pulsatile arterial flow are presented using a realistic arm phantom.
A narrowing of the vessels is built into the arm phantom to simulate the influence of a stenosis. In the experiment, the influence of the stenosis and air chamber function upon pulsatility is investigated.

The example screen shots of the measurement software show in comparison the typical Doppler spectral images for a continuous venous flow (Fig. The rate of penetration of dissolution fluid in to the matrix determines the drug dissolution and subsequent release. This swelling increases the aqueous solvent content within the formulation & also polymer mesh size & so make the drug to diffuse through the swollen network into the external environment.
Experimental setup for measuring blood flow at an arm phantom by means of Doppler ultrasound. Furthermore, the influence of a stenosis and the air chamber function on pulsatility is investigated.
In this way, differences between healthy and altered vessels can be clearly presented in the spectral image.

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