Spongy particles soak up bubbles

September 25, 1991

Two researchers at the University of Rochester in Rochester, NY,have applied for patents on a particle technology for use as anultrasound contrast agent. The technology involves trapping airwithin sub-micron-sized particles of iodipamide ethyl ester

Two researchers at the University of Rochester in Rochester, NY,have applied for patents on a particle technology for use as anultrasound contrast agent. The technology involves trapping airwithin sub-micron-sized particles of iodipamide ethyl ester (IDE).

IDE, a derivative of the x-ray contrast agent iodipamide, hasbeen under development at Rochester since the 1970s, said MichaelViolante, an associate professor of radiology. Violante is oneof the inventors of the technology.

The researchers first developed a solid sub-micron IDE particle,which was used as a liver CT contrast agent, he said. Patentshave been granted on this technology. The more recent breakthroughinvolved development of a spongy version of IDE that traps microscopicair bubbles. Air bubbles reflect and enhance ultrasound signals.

Unlike ultrasound agents under development by Schering (seepreceding story) and Molecular Biosystems (MBI), the air is trappedwithin particles that are solid enough to survive changes in heartpressure. Since the IDE "bubbicles" can make it pastthe heart, they are able to image the liver and other organs,Violante told SCAN.

This solidity is paid for, however, in a lower signal strength,he said.

"The Schering and MBI agents are bubbles that are moreflexible and have a very strong signal. Our signal strength islower, but we have more stability," he said.

Liver tumors appear darker than surrounding healthy tissueon an ultrasound image with the contrast agent, since tumor tissuedoes not absorb the bubbicles from the blood and healthy tissuedoes.

Violante developed the agent with Kevin Parker, an associateprofessor of electrical engineering and radiology and directorof the Rochester Center for Biomedical Ultrasound. Violante isalso managing director of Medisperse of Rush, NY, a company setup to license and commercialize the IDE technology.

Medisperse is seeking collaboration with a major pharmaceuticalcompany to develop the particles for both imaging and therapeuticpurposes, Violante said. If sufficient support is obtained, theultrasound agent might reach the preclinical investigation stagein about a year, he said.

BRIEFLY NOTED:

  • Researchers working with Molecular Biosystems (MBI) ofSan Diego showed preliminary results at the Society of MagneticResonance in Medicine meeting in San Francisco last month indicatingthe firm's albumin microsphere technology may be effective asan MRI blood flow agent.

Albunex, MBI's ultrasound contrast agent under premarket approvalapplication with the Food and Drug Administration, is the company'sfirst and major use of its air-filled albumin microspheres. Thesame technology appears to influence MRI signal intensity--creatinga signal void--since air is not susceptible to magnetic fields.

Dr. Michael Mosely and colleagues at the University of Californiaat San Francisco performed the MRI research.

MBI also licensed a new type of MRI contrast agent from JohnsHopkins University, the firm reported this month. The labelingtechnology involves use of a compound called perfluoro-tert-butyl(PFTB) that can be attached to a variety of naturally occurringmolecules involved in metabolism.

"We see this approach using PFTB as a method that givesnot only anatomical information from MRI, but also physiologicalinformation by viewing the metabolism of naturally occurring moleculesin the body," said Kenneth J. Widder, MBI chairman and CEO."If one can obtain functional information, as well as visualizeorgans, that would be a major advancement in MRI use."

  • GE Medical Systems will award up to six fellowships annuallyworth $50,000 each to academic radiology researchers who pursueprojects in the area of radiology socioeconomics. The GE radiologyresearch academic fellowship program will fund nontraditionalradiology research in the areas of:

--technology assessment;

--health and economic outcomes; and

--decision analysis and quality of care.

"Today's emphasis on health outcomes and technology assessmentis challenging radiology's influence and control over clinicaldiagnostic imaging," said Bobby Bowen, GE vice president.

Nominations for the award must be submitted by U.S. academicradiology departments no later than Oct. 31. Fellowships willbe chosen by a board of review chaired by Dr. Albert Moss, radiologychairman at the University of Washington and president of theAssociation of University Radiologists.