title: Correlation of real-time haemoglobin oxygen saturation monitoring during photodynamic therapy with microvascular effects and tissue necrosis in normal rat liver.
abstract: Photodynamic therapy (PDT) requires a photosensitising drug, light and oxygen. While it is known that the haemoglobin oxygen saturation (HbSat) can be altered by PDT, little has been done to correlate this with microvascular changes and the final biological effect. This report describes such studies on the normal liver of rats sensitised with aluminium disulphonated phthalocyanine. In total, 50 J of light at 670 nm, continuous or fractionated at 25 or 100 mW, was applied with a single laser fibre touching the liver surface. HbSat was monitored continuously 1.5-5.0 mm from the laser fibre using visible light reflectance spectroscopy (VLRS). Vascular shutdown was assessed by fluorescein angiography 2-40 min after light delivery. Necrosis was measured at post mortem 3 days after PDT. In all treatment groups at a 1.5 mm separation, HbSat fell to zero with little recovery after light delivery. At 2.5 mm, HbSat also decreased during light delivery, except with fractionated light, but then recovered. The greatest recovery of fluorescein perfusion after PDT was seen using 25 mW, suggesting an ischaemia/reperfusion injury. Necrosis was more extensive after low power and fractionated light than with 100 mW, continuous illumination. We conclude that VLRS is a useful technique for monitoring HbSat, although the correlation between HbSat, fluorescein exclusion and necrosis varied markedly with the light delivery regimen used.
authors.affiliation: National Medical Laser Centre, Academic Division of Surgical Specialities, Royal Free and University College Medical School, University College London, Charles Bell House, 67-73 Riding House Street, London W1W 7EJ, UK. j.woodhams@ucl.ac.uk
authors.forename: J H
authors.initials: JH
authors.lastname: Woodhams
authors.forename: L
authors.initials: L
authors.lastname: Kunz
authors.forename: S G
authors.initials: SG
authors.lastname: Bown
authors.forename: A J
authors.initials: AJ
authors.lastname: MacRobert
mesh_terms: D000818:Animals; D005260:Female; D005451:Fluorescein Angiography; D006454:Hemoglobins / Q000032:analysis*; D007211:Indoles / Q000008:administration & dosage*; D007511:Ischemia; D008099:Liver / Q000098:blood supply / Q000473:pathology / Q000502:physiology*; D009336:Necrosis; D009942:Organometallic Compounds / Q000008:administration & dosage*; D010100:Oxygen / Q000032:analysis*; D010477:Perfusion; D010778:Photochemotherapy; D017319:Photosensitizing Agents / Q000008:administration & dosage*; D051381:Rats; D017208:Rats, Wistar; D013057:Spectrum Analysis
chemical_list: D006454:Hemoglobins; D007211:Indoles; D009942:Organometallic Compounds; D017319:Photosensitizing Agents; C064331:aluminum phthalocyanine disulfonate; D010100:Oxygen