Next-generation treatment of port wine stains and vascular lesions.
Next-generation treatment of port wine stains and vascular lesions.
John and Jennifer Barton co-discovered the GLIIRA (Green-Light Induced Infra-Red Absorption) phenomenon in photothermally coagulating blood as part of a study on the effect of laser heating on blood. Under the influence of shock laser heating, at a critical temperature determined by the heating rate and duration (a so-called Arrhenius process), oxy-hemoglobin (oxy-Hb) in the erythrocytes in blood is converted to met-hemoglobin (met-Hb) with very high efficiency. The met-Hb thus formed has a very different optical absorption spectrum in the visible and near-IR regions of the EM spectrum, and, specifically, significantly higher absorption in the near-IR between 700 – 1300 nm. This allows a novel use of two sequenced laser pulses to effect laser photothermal coagulation of blood in cutaneous vascular lesions at lower fluences than would be required by using two independent wavelengths. (Bibliography Barton et al. 2001 – 2006)
Laser-generated MRI contrast agents
Laser-generated MRI contrast agents
An interesting side property of met-Hb formed in the GLIIRA process is that met-Hb is intensely paramagnetic, leading to pronounced changes in the MRI images of photothermally coagulated blood compared to unmodified blood. Since the met-Hb transition temperature can be controlled using the heating rate and duration, it is possible to modify blood to act as an MRI contrast agent while leaving the erythrocyte intact during the process.
