Brain tumors account for approximately just 2% of all cancers worldwide, but have a noticeable impact on cancer morbidity and mortality. Removal of brain tumors poses a big challenge for neurosurgeons, pediatricians and neuro-oncologists. An important aspect of this challenge is to adequately differentiate between tumor tissue and healthy brain tissue. Tumors that are located within the eloquent cortex (functional brain cortex and major white matter fiber tracts) pose a particular surgical challenge due to the high risk of postoperative neurological deficits. Together with the In-Body Systems department of Philips Research and the Karolinska Institute in Sweden, the Delft University of Technology is participating in a new research focusing on adding diffuse reflectance spectroscopy in a neurosurgical instrument that can aid in better identifying the brain tumor margin. Previous research has used diffuse reflectance spectroscopy or a combination of diffuse reflectance and tissue fluorescence from endogenous (e.g., NADPH), exogenous (e.g., fluorescein), or exogenously induced fluorophores (e.g., PpIX) to identify spectral differences between healthy brain tissue and brain tumor tissue over a range of 400-900 nm. This master thesis presents the spectral differences between healthy and tumorous tissue over a range of 400-1600 nm, while using a spectroscopic tool, to better determine the demarcation of brain tumor margins with increased accuracy. The differences in optical characteristics in healthy brain tissue (i.e. white and gray matter) and human brain tumor tissue were identified. Furthermore, it was investigated whether the optical characteristics can provide a means to quantify the distinction between healthy and brain tumor tissue. Clear differences were found in the spectra between the different tissues. In the visible region higher values for the absorption coefficient were identified as indicators for tumor tissues. In the near infrared region clear distinctions in the diffuse reflectance spectra were observed between gray matter, tumor tissue and white matter, with gray matter presenting the highest value. The reduced scattering coefficient showed especially a clear distinction for white matter, presenting the highest values, compared to gray matter and tumor tissue. This was in line with the measurements of the scattering parameters and the fat fraction, with white matter presenting the highest value which can be explained due to its myelinated axons. For the other investigated parameters, an increased level of blood concentration and lower levels of StO2 were indicated as biomarkers for the tumor tissues. However, both physiological parameters are likely to change from in vivo to ex vivo settings which require that they should be investigated in in vivo experiments first before statements about their reliability can be made. The study was followed with a clinical workflow analysis, to identify the most promising neurosurgical instrument used during craniotomy in which diffuse reflectance spectroscopy can be integrated. Based on observations at brain tumor surgeries, open interviews with neurosurgeons and an investigation on several instruments, the suction cannula was found to be the most promising neurosurgical instrument to combine with diffuse reflectance spectroscopy. Finally, a prototype was designed and tested. In addition, it was investigated whether different amounts of suction power had an influence on the accuracy of the measured spectra while performing measurements with the prototype on healthy pig brain tissue. Overall, it can be concluded that spectral differences between healthy and tumorous tissue can be observed with the prototype and future research should increase the amount of data to verify these results. Furthermore, in vivo measurements should indicate whether these findings are consistent when the physiology of the tissues changes.