Intracranial pressure telemetry system. I. Hardware development

Results in the development of intracranial pressure(ICP) telemetry systems are reported. Included are a single-channel ICP system and a two-channel ICP and temperature system. The unit used hybrid-integrated circuits housed in a Kovar flatpack and packaged with polyurethane or Hysol epoxy. Battery and radio frequency (RF) induction power supplies were tested. The two-channel systems used RF power at 3.5 MHz and transmitted signals around 120 MHz. The package measures 3 x 2 x 0.8 cm and weighs 9 g. The pressure range is -20 to +100 mm Hg with accuracy to 1.0 mm Hg. The implant measures absolute pressure and has a baseline stability of better than +/- 2 mm Hg/month. 17 dogs and 4 goats were used for in vivo evaluation. A summary of results is presented. Detailed evaluation is given in section II of this paper.