Titanium is strong, lightweight, and relatively compatible with bodily fluids and tissues. That's why biomedical engineers at Arrow International, Walpole, Mass., chose it for the housing of its Model3000 Constant Flow Implantable Pumps. The contoured circular housing has smooth sloping edges thatwere hydroformed at Hudson Tool & Die, Ormond Beach, Fla. The housing, which measures up to 86.4 mm indiameter and 27.4 mm thick, also has a raised area used for refilling.

Pain-controlling drugs orchemotherapy agents are stored in an expandable reservoir. They are metered out via a thin tube usingcapillary action and pressure from a propellant gas inside the housing. A safety valve lets doctorsinject large doses of drugs directly into the patient using special needles.