An optical imaging device and system can be used to visualize and/or provide a quantitative measure of changes in patient vasculature, for example, to monitor responsiveness of a tumor to a particular chemotherapy treatment. A plurality of detectors (e.g., two) are spaced from a plurality of substantially monochromatic light sources (e.g., four) on an interrogation face of the handheld device. Wavelengths of light in the near-infrared range are used to measure the content of hemoglobin, water, and lipid of the tissue that the interrogation face comes in contact with. The light can be modulated so that the effect of ambient light is not minimized or at least reduced. The detected signal is amplified, filtered, and digitized within the device by appropriate electronics. In embodiments, handheld device can include a wireless communication module, such as a Bluetooth device, for wireless transmission of data to/from the remote processor or computer.
