The extent, time course, and fraction size dependence of mouse spinal cord recovery from radiation injury

Journal Article · Sat Oct 15 04:00:00 EDT 1994 · International Journal of Radiation Oncology, Biology and Physics

DOI:https://doi.org/10.1016/0360-3016(92)90947-G· OSTI ID:96095

Lavey, R S; Taylor, M G; Tward, J D ^[1]

---

1. Univ. of California, Los Angeles, CA (United States); and others

This experiment was designed to assess: (a) the influence of fraction size and time interval between fractions on the tolerance of the spinal cord to high cumulative doses of radiation; and (b) the influence of the long-term recovery process on the tolerance of the spinal cord to reirradiation. The T10-L2 level of the spinal cord of C3Hf mice was irradiated using a conventionally fractionated regimen of 2.0 Gy once daily, a prolonged fractionated regimen of 1.2 Gy once daily, a hyperfractionated regimen of 1.2 Gy twice daily, or a single dose of 12 Gy followed 0-190 days later by a second dose of 5-20 Gy. Mice in the multifractionated regimen groups were given a single 15 Gy top-up- dose 24 h after reaching a cumulative fractionated dose of 24-70 Gy. Hind limb strength was measured weekly for 2 years after the completion of irradiation. Paralysis occurred in a bimodal time distribution, with peaks at 5-10 months and 15-23 months after the completion of irradiation. The cumulative radiation dose was directly associated with the incidence of paralysis in each radiation schedule (p<0.0001) and inversely associated with the time to onset of paralysis in the 1.2 Gy b.i.d. (p = 0.0001) and 2.0 Gy q.d. schedules (p = 0.03). The median latency of paralysis in each group was inversely associated with the incidence of paralysis in that group (p =<0.001). Decreasing the fraction size from 2.0 to 1.2 Gy once daily markedly increased the radiation tolerance of the spinal cord (p <0.0001), consistent with a very small alpha-beta value of -0.30 Gy ({approximately}95% confidence interval -0.72, +0.18) in the linear-quadratic model. Decreasing the time interval from 24 h to alternating 8 and 16 h periods produced an offsetting diminuation in cord tolerance (p <0.0001). 36 refs., 5 figs., 6 tabs.

• Sponsoring Organization: USDOE
• OSTI ID: 96095
• Journal Information: International Journal of Radiation Oncology, Biology and Physics, Journal Name: International Journal of Radiation Oncology, Biology and Physics Journal Issue: 3 Vol. 30; ISSN IOBPD3; ISSN 0360-3016
• Country of Publication: United States
• Language: English

Related Subjects

56 BIOLOGY AND MEDICINE
APPLIED STUDIES
CUMULATIVE RADIATION EFFECTS
DOSE-RESPONSE RELATIONSHIPS
FRACTIONATED IRRADIATION
MICE
SPINAL CORD
TIME DEPENDENCE
TOLERANCE