Conventional brain imaging modalities are limited in that they image o
nly secondary physical manifestations of brain injury, which may occur
well after the actual insult to the brain and represent irreversible
structural changes, A real-time continuous bedside monitor that images
functional changes in cerebral blood flow or oxygenation might allow
for recognition of brain tissue ischemia or hypoxia before the develop
ment of irreversible injury. Visible and near infrared light pass thro
ugh human bone and tissue in small amounts, and the emerging light can
be used to form images of the interior structure of the tissue and me
asure tissue blood flow and oxygen utilization based on light absorban
ce and scattering. We developed a portable time-of-flight and absorban
ce system which emits pulses of near infrared light into tissue and me
asures the transit time of photons through the tissue. Images can then
be reconstructed mathematically using either absorbance or scattering
information. Pathologic brain specimens from adult sheep and human ne
wborns were studied with this device using rotational optical tomograp
hy. Images generated from these optical scans show that neonatal brain
injuries such as subependymal and intraventricular hemorrhages can be
successfully identified and localized. Resolution of this system appe
ars to be better than 1 cm at a tissue depth of 5 cm, which should be
sufficient for imaging some brain lesions as well as for detection of
regional changes in cerebral blood flow and oxygenation. We conclude t
hat light-based imaging of cerebral structure and function is feasible
and may permit identification of patients with impending brain injury
as well as monitoring of the efficacy of intervention. Construction o
f real-time images of brain structure and function is now underway usi
ng a fiber optic headband and nonmechanical rotational scanner allowin
g comfortable, unintrusive monitoring over extended periods of time.