Telemetric light delivery and monitoring system for photodynamic therapy based on solid-state optodes

Abstract

Light delivery and optical monitoring during photodynamic therapy (PDT) is often limited by the need for a physical optical link between the light source and detection devices and the treatment volume. This can be critical when sources need to be implanted within the body for extended periods. We report on the latest developments for a telemetric PDT delivery and monitoring device that can dynamically vary the local illumination parameters based on the in-situ fluence rate within the PDT target volume. Local light delivery and collection is achieved using solid-state optodes, microfabricated on a silicon substrate. Photodiodes have been produced using a standard bipolar process. Chip-form LEDs are then assembled into micro-machined pits adjacent to the light fluence rate detectors. The devices (1.2×1.2mm²) are bonded to a flexible PCB together with the remaining electronics. Power coupling and communications are achieved by means of an inductive link while light delivery and fluence rate monitoring are digitally managed using a microcontroller. These devices are being tested in optical phantoms and in pre-clinical models. Our results show that it is possible to manufacture solid-state optodes of suitable dimensions and that it is feasible to telemetrically deliver and control the local fluence rate using them. It can also be concluded from our work that while the optode is sufficiently small to be useful as a light delivery and monitoring device, digital control, read-out electronics and power coupling can benefit from further optimization and miniaturization.