Single-Photon Emission Computed Tomography (SPECT)

SPECT helps us directly look at cerebral blood flow thus helping us indirectly infer about the brain activity (metabolism). It uses the scanning technology of CT scan reconstruction but instead of X-rays it detects gamma rays. A small amount of radioactive isotope is injected into the patient's vein which runs through the blood stream. The radioactive isotope is readily taken up by the cells in the brain. This isotope keeps degrading and at each step of decay it emits a gamma ray. Thereafter, the SPECT gamma camera rotates slowly around the head. The emitted rays are taken from multiple angles, usually encompassing 180° or 360° with the special crystals in the camera tracing them. Finally a supercomputer reconstructs 3-D images of the brain activity. The figure given below shows the SPECT image of veteran practitioners of Tibetan Buddhism. The image on the left shows decreased activity in the parietal lobe whereas the image on the right shows increased frontal activity. Parietal lobe is responsible for space and time orientation during meditation and frontal lobe is responsible for focusing attention and concentration

SPECT ( Source: Davidson et al. (2003). Alterations in brain and immune function produced by mindfulness meditation. Psychosomatic Medicine, 65, 564-570. )