Photodynamic therapy is currently being evaluated as a minimally invas
ive procedure for endometrial ablation not requiring anaesthesia, Ligh
t penetration depths at 630, 660 and 690 nm and the optimal configurat
ion of intrauterine light-diffusing fibres were determined in 14 human
uteri to assist in the design of a light intrauterine device, Postmen
opausal ex-vivo uteri showed a significantly lower light penetration d
epth than pre-menopausal uteri, With a single central diffusing fibre
inserted, the fluence rate measured in the uterine wall at the most re
mote 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 th
ree fibres, Distension of the uterine cavity with 2 ml of an optically
clear fluid increased the fluence rate at the fundus between the fibr
es at a depth of 2 mm by a factor of 4, We conclude that in normal-siz
ed pre-menopausal uterine cavities, three diffusing fibres will delive
r 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 therm
al damage, For distorted and elongated cavities, either slight distens
ion of the cavity or the insertion of a fourth diffusing fibre is requ
ired.