Intrauterine light delivery for photodynamic therapy of the human endometrium

Photodynamic therapy is currently being evaluated as a minimally invasive procedure for endometrial ablation not requiring anaesthesia, Light penetration depths at 630, 660 and 690 nm and the optimal configuration of intrauterine light-diffusing fibres were determined in 14 human uteri to assist in the design of a light intrauterine device, Postmenopausal ex-vivo uteri showed a significantly lower light penetration depth than pre-menopausal uteri, With a single central diffusing fibre inserted, the fluence rate measured in the uterine wall at the most remote point of the cavity decreased to 1.1 +/- 0.4% of that measured at closest proximity, whereas it decreased to only 40.0 +/- 9.0% with three fibres, Distension of the uterine cavity with 2 ml of an optically clear fluid increased the fluence rate at the fundus between the fibres at a depth of 2 mm by a factor of 4, We conclude that in normal-sized pre-menopausal uterine cavities, three diffusing fibres will deliver an optical dose above the photodynamic threshold level at a depth of 4 mm, even in the most remote areas, in <30 min without causing thermal damage, For distorted and elongated cavities, either slight distension of the cavity or the insertion of a fourth diffusing fibre is required.