Background-Management of peripheral lung tumours may be risky in patie
nts with poor lung function or in the elderly. A new possibility is in
terstitial laser photocoagulation (ILP) in which tumours are gently co
agulated using thin laser fibres placed percutaneously under radiologi
cal guidance. This could have a useful palliative role in selected pat
ients, but to be safe the effects on normal lung parenchyma must first
be understood. This paper describes the creation and healing of ILP l
esions in the normal rat lung. Methods-ILP was performed using single
laser fibres placed percutaneously in the left lung of normal rats und
er general anaesthetic with radiological guidance (laser power 1-3 W a
t 805 nm, treatment time 250-1000 s). The lesion size and healing were
studied in rats killed at times from three days to six months after t
reatment, the bursting pressure was measured, and any complications no
ted. Results-Zones of necrosis up to 12 mm in diameter were produced,
the size depending on the laser power and treatment time. Histological
examination showed typical thermal effects with complete healing with
fibrosis by two months. The effect was very localised with remarkably
little effect on the structure and function of the rest of the lung.
Adverse effects in the lung parenchyma only occurred if the ILP lesion
involved the hilar vessels or the oesophagus, causing pulmonary conge
stion and perforation, respectively. Pneumothorax was seen in 6% of ca
ses. Conclusions-ILP with a single fibre can produce a localised zone
of necrosis in normal lung parenchyma which heals safely and which has
Little effect on the rest of the lung. Further study of this techniqu
e using multiple fibres in a larger animal model is warranted to see i
f it is feasible and safe to produce a large enough volume of necrosis
to be of value in the treatment of small peripheral lung tumours in p
atients who are unsuitable for surgery or palliative radiotherapy.