CONTROL ALGORITHM

The control unit contains the Intelligent Control Algorithm (ICA), as shown in Figure 8, which fuses data from various sensing resources and makes effective decisions to control the delivery of chemotherapeutic agents. Based on the principle of homeostasis, the ICA achieves a stable state of equilibrium that limits the tumor growth without endangering the tissues surrounding the tumor site. The ICA is programmed inside the microcontroller with inputs from sensors such as for VEGF spectrometer, pressure and pH. This information pertaining to tumor growth is extracted to determine the progress of treatment based on the parameters in the “lookup table”. The sensor information is also used to calculate the internal states which permit adaptation of the system to achieve the desired parameters. The “lookup table” produces actuation parameters to control the pumps that affect the conditions in the tumor site. The internal states can be updated based on external inputs from the physician via the wireless transceiver.

The control unit also contains a smart energy management algorithm (SEMA) to manage the various components and minimize the energy usage. Delivery of medication is expected to occur just a few times per day. Therefore, nearly all the electronics can be shut off most of the time. The control unit’s hardware components are activated from software only when needed. 

In addition, SEMA contains an advanced patient context (motion) classification algorithm interfaced with a triaxial accelerometer. This motion classification algorithm permits the implant control unit to intelligently deliver biological response modifier medication based on the patient’s motion and orientation states. Some conditions we plan to explore are whether it is more effective to operate the pumps only when the patient is lying down (i.e., no height difference between the reservoirs located at the chest and tumor site in the brain) or adjust the pump rate based on orientation to compensate for pumping against gravity.