Temperature control and light penetration in a feedback interstitial laser thermotherapy system

P. H. Möller, L. Lindberg, P. H. Henriksson, B. R.R. Persson, K. G. Tranberg

Research output: Contribution to journalArticlepeer-review


The aim of this study was to describe the performance of a closed loop interstitial laser thermotherapy system in processed liver and to demonstrate its suitability for treating a vascularized tumour in vivo. The thermotherapy system consisted of an Nd:YAG laser and a temperature feedback circuit including an automatic thermometry system and thermistor probes. Experiments in processed liver were performed with a sapphire probe and temperature control at a distance of 10 mm. In most experiments at 1-2 W, and in half of the experiments at 3 W, there was no carbonization, a moderate change in the light penetration and excellent control of the temperature. In experiments with output powers of 4-5 W there was carbonization with rapid deterioration of light penetration and impaired control of the temperature. Carbonization affected the distribution of temperatures, which were lower below, and higher above, the laser tip in experiments with carbonization as compared to experiments without carbonization. Treatment of an adenocarcinoma implanted into rat liver was performed at 2 W with a bare fibre and without blood inflow occlusion. The feedback thermistor probe was placed 3 mm outside the margin of the tumour (largest diameter 9.5 ± 0.3 mm (mean ± SEM)). Temperature control and light penetration characteristics were similar to those found in vitro. No tumour could be demonstrated at sacrifice 6 days later. It is concluded that a closed loop feedback system can produce stable and reproducible local hyperthermia, that it performs better when carbonization is avoided and light penetration is preserved and that it has a great potential for interstitial thermotherapy of malignant tumours.

Original languageEnglish
Pages (from-to)49-63
Number of pages15
JournalInternational Journal of Hyperthermia
Issue number1
Publication statusPublished - 1996 Jan 1

Subject classification (UKÄ)

  • Other Engineering and Technologies not elsewhere specified
  • Surgery

Free keywords

  • Adenocarcinoma
  • Bare fibre
  • Interstitial hyperthermia
  • Nd-YAG laser
  • Rat
  • Sapphire probe


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