Appeal No. 1999-2230
Application 08/465,236
Discussion
The present invention relates to the preparation of ultrasound contrast agents
comprising hollow microcapsules, used to enhance ultrasound imaging techniques. More
specifically, the invention relates to hollow microcapsules enclosing a gas- or vapor-filled
space essentially without solid material therein, where more than 30% of the
microcapsules have a diameter within a 2 :m range and at least 90% have a diameter
within the range 12.0-25.0 :m. The microcapsules are suitable for intra-arterial
administration, and are capable of being dried to form a powder of such microcapsules.
The present invention further relates to a process for preparing such microcapsules, and to
pharmaceutical compositions comprising the microcapsules.
Prior art echocontrast agents suffer from several drawbacks making them
unsuitable for perfusion mapping of the myocardium or similar capillary beds, including
poorly controlled size distribution, low pressure resistance, and weak echogencity. In
contrast, the microcapsules of the present invention possess unique properties which
make them particularly advantageous for use as a deposit echocontrast agent to delineate
under-perfused areas of microcirculation. The novel microcapsules are produced by a
spray-drying process wherein the median size and size distribution of the microcapsules
are tightly controlled. Applicants have discovered that by manipulating the parameters of
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