(A) Schematic depicting the effects of radiation energy on bone marrow injury with calculated average energies of the radiation spectra, ratios of photoelectric effect to Compton scattering in compact bone and soft tissue, and LD50 from each irradiation source. (B) Kaplan-Meier survival curves from experiments with whole-body irradiation of mice using orthovoltage X-rays with 1 mm Cu filtration, (C) orthovoltage X-rays with Thoraeus filtration, or (D) Cs-137 γ-rays. (n≥10/group; Results pooled from several experiments.) (E) Mean weight loss (%) following whole body irradiation with orthovoltage X-rays with 1 mm Cu filtration, (F) orthovoltage X-rays with Thoraeus filtration, or (G) Cs-137 γ-rays. (H) Logit analysis of 30-day survival using each radiation modality. (I) Kaplan-Meier curve comparing 7.0 Gy with each modality. 95% confidence intervals (dotted line). (J) Comparison of weight loss (%) following 7 Gy whole-body irradiation with each radiation modality. Data is represented as mean ± SEM. HVL: Half-Value Layer.