An imaging apparatus is disclosed. The imaging apparatus includes a source of electromagnetic radiation that is configured to emit electromagnetic radiation at two or more wavelengths through an imaging volume. The imaging apparatus also includes an ultrasound transducer that is configured to direct ultrasound waves through the imaging volume such that electromagnetic radiation passing through the imaging volume is modulated at the frequency of the ultrasound waves. The imaging apparatus further includes one or more electromagnetic radiation detectors that are configured to detect the modulated electromagnetic radiation from the imaging volume.