  Fluorescence-guided surgery has emerged as a vital tool for tumour resection
procedures. As well as intraoperative tumour visualisation, 5-ALA-induced PpIX
provides an avenue for quantitative tumour identification based on ratiometric
fluorescence measurement. To this end, fluorescence imaging and fibre-based
probes have enabled more precise demarcation between the cancerous and healthy
tissues. These sensing approaches, which rely on collecting the fluorescence
light from the tumour resection site and its remote spectral sensing, introduce
challenges associated with optical losses. In this work, we demonstrate the
viability of tumour detection at the resection site using a miniature
fluorescence measurement system. Unlike the current bulky systems, which
necessitate remote measurement, we have adopted a millimetre-sized spectral
sensor chip for quantitative fluorescence measurements. A reliable measurement
at the resection site requires a stable optical window between the tissue and
the optoelectronic system. This is achieved using an antifouling diamond
window, which provides stable optical transparency. The system achieved a
sensitivity of 92.3% and specificity of 98.3% in detecting a surrogate tumour
at a resolution of 1 x 1 mm2. As well as addressing losses associated with
collecting and coupling fluorescence light in the current remote sensing
approaches, the small size of the system introduced in this work paves the way
for its direct integration with the tumour resection tools with the aim of more
accurate interoperative tumour identification.
