Near-infrared optical tomography
In this project we propose a time-resolved approach for functional and anatomical imaging of human brain and other tissues. The core of the proposed imaging system will be an array of single photon detectors fabricated in standard CMOS technology. Thanks to the system’s time resolution and speed, it will be possible to achieve unprecedented resolution and accuracy, thus enabling new and advanced diagnostic tools. The imaging system will be highly miniaturized and low-cost, to be employed in extensive clinical trials, while comparative studies will become more reliable and reproducible due to the inherent quantitative nature of the approach.
Optical imaging of the brain
- Important physiological parameters such as oxy-, deoxy- and total haemoglobin (O2Hb, HHb and tHb) concentration can be measured with a high sensitivity. These reflect cerebral blood circulation, oxygenation and functional activity.
- It is entirely non-invasive, utilizing neither drugs or tracers. The use of non-ionizing radiation makes it suitable for fragile patients and continuous monitoring.
- A spatial resolution on the order of cm allows accurate localisation of the oxygen in the brain for the diagnosis of brain injuries or study of brain function.
- NIROT systems are relatively inexpensive and can be miniaturized.
Towards High speed, High Resolution NIROT
In a collaboration between AQUA and the Biomedical Optics Research Laboratory (BORL) at University Hospital Zurich (USZ), we have been working on a new approach to time-resolved NIROT using arrays of single-photon avalanche diodes (SPADs). Their high time-resolution and ability to integrate thousands of detectors on the same camera chip as the timing electronics makes them the ideal candidate for producing a low-cost, miniaturised NIROT system with unprecedented spatial resolution.
A new camera has also been manufactured which has been optimised, from the photodetector structure through to the chip architecture, for fast acquisition speeds in the NIROT application. The camera has been integrated into a NIROT system, ‘Pioneer’, employing a supercontinuum laser and acousto-optic tuneable filter. The system is currently being validated in laboratory experiments with clinical measurements on the near-term horizon.
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| Pioneer NIROT imaging system | Measurement of silicon phantom compared to simulation of a phantom with same optical properties |