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a National Medical
Laser Centre, Department of Surgery, University College London Medical
School, London, UK, b Department of Thoracic Medicine,
University College London Hospitals, London, UK, c Department of Histopathology,
Imperial Cancer Research Fund, London, UK
Correspondence to: Dr D I Fielding, Department of Respiratory Medicine, Princess Alexandra Hospital, Ipswich Road, Woolloongabba, Brisbane, Queensland 4102, Australia.
Received 15 December 1997; Returned to authors 22 January 1998; Revised version received 17 March 1998; Accepted for publication 3 April 1998
BACKGROUND
Management
of peripheral lung tumours may be risky in patients with poor lung
function or in the elderly. A new possibility is interstitial laser
photocoagulation (ILP) in which tumours are gently coagulated using
thin laser fibres placed percutaneously under radiological guidance.
This could have a useful palliative role in selected patients, but to
be safe the effects on normal lung parenchyma must first be understood.
This paper describes the creation and healing of ILP lesions in the
normal rat lung.
METHODS
ILP was
performed using single laser fibres placed percutaneously in the left
lung of normal rats under general anaesthetic with radiological
guidance (laser power 1-3 W at 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 treatment, the bursting pressure was
measured, and any complications noted.
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 congestion and
perforation, respectively. Pneumothorax was seen in 6% of cases.
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 technique using multiple fibres in a
larger animal model is warranted to see if 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 patients who are
unsuitable for surgery or palliative radiotherapy.
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