Apparent dose rate effect at low dose thermal neutron irradiation

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An interesting effect was observed when V-79 Chinese hamster cells were irradiated with thermal neutrons to test the effect of delivering radiation at low dose rates compared to high. In these studies, the reactor power was changed to accommodate dose rate. The length of the irradiation interval, in units of actual time, was used to assure a thermal fluence unburdened by complexities associates with dose delivery from a nuclear reactor. Cells from the same flask, were irradiated at reactor powers of 250 kW, 500 kW, and 1 MW for varying periods of time. A biphasic component to the cell survival curve was observed at the 250 kW power. The phenomenon was studied by irradiating cells at 250 kW for 6, 12, 18, 24, 48 and 72 minutes. The shorter (6-18 min.) and longer (24-72) irradiations, each with an independent control, showed very different responses to the neutrons. Group I (short) evidenced a linear, high LET type damage; Group II evidenced a large shoulder typifying repair. For purposes of analysis, the groups were considered as separate entities since each had its own control. A RBE of 1.9 was found for the shorter irradiations. Clinical trials in boron neutron capture therapy (BNCT) are currently using higher reactor powers (∼3 MW) for patient irradiations. The implication of these low dose rate thermal neutron studies is that, in BNCT, sparing of surrounding normal tissues might result if patient irradiations were to be carried out at reduced reactor powers and lengthier exposure times.

Original languageEnglish
Article number68
Pages (from-to)879
Number of pages1
JournalAnnual International Conference of the IEEE Engineering in Medicine and Biology - Proceedings
StatePublished - 1 Jan 2000
Externally publishedYes

ASJC Scopus subject areas

  • Signal Processing
  • Biomedical Engineering
  • Computer Vision and Pattern Recognition
  • Health Informatics


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