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|The aim is to work on a near-infrared multispectral imaging (NIRI) device by the Wolf laboratory. The instrument enables the volumetric imaging of the oxygenation (oxy-, deoxy- and total hemoglobin concentration and oxygen saturation of hemoglobin) in all three dimensions through the simultaneous measurement of the scattering and absorption properties in multiple spectral bands. The aim is to measure tumor oxygenation.||
So far NIRI or optical tomography instruments available have a spatial resolution of only 1-2cm and a temporal resolution of 5-10min (review Hebden & Austin, 2007). This resolution is too low and too slow to assess tumor oxygenation.
In the Wolf lab, a tuneable supercontinuum laser will be used to create ultra-fast pulses, allowing full scanning of the near-infrared spectral (NIR) region. Scattered NIR photons will be labelled in space and time by single photon avalanche photo diode (SPAD) arrays with an unprecedented number of detectors and time to digital converters. Ultra-short laser pulses provide the continuum of high frequency components required for fine spatial sampling and any ambiguity in image reconstruction is largely suppressed by the large number of complementary measurements performed by the SPAD array.
Work package 1: Conducting experiments in vitro in phantoms with a SPAD array that is available, but not optimized for NIRI. The aim is to study objects of known optical properties and initially evaluate image reconstruction techniques. We have already been able to achieve a resolution of 5mm in the laboratory (see Figure Mata Pavia, Charbon & Wolf, 2011). Mathematical simulations show that a higher resolution is feasible.
Work package 2: A novel camera chip is designed that is optimized for NIRI. This means that this camera chip has a high sensitivity in the near infrared spectral range, a high fill factor and thus a high photon detection probability. In addition, the number of time to digital converters is increased to enable measuring arrival times of photons in all pixels. This camera chip is necessary for measurements in humans and is expected to be produced at the end of 2016.
Work package 3: A non-contact, non-invasive instrument (hardware) will be built with a focus on application in mice (transmission and reflection mode) to analyze the oxygenation of tumors in mice. Since mice are small, it is sufficient to employ a normal infrared camera without capability of measuring arrival times of photons. This camera measure the light intensity of NIR light in reflected by and transmitted through the mice and enables to calculate tumor oxygenation. Measurements have successfully been completed.
During all work packages there will be intense collaboration with all the other partners, e.g. accompanying the clinicians during their rounds for the engineers and physicists to gain insights into the clinical reality and to adapt the instrumentation according to the clinical needs.
The novel instrument will be paramount for many research projects within the KFSP Tumor Oxygenation network to non-invasively measure oxygenation.