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Bone Marrow Transplant




Dosimetry/Physics Principles

It is important to ensure:

  • Reproducibility:  immobilization and patient comfort
  • Homogeneity:  leukemic cells anywhere, including skin.  Dose variability within the patient +/- 5% excellent and +10% acceptable
  • Dose rate :
    • has a significant effect on long term toxicity: especially to lung and kidneys.  (Dose rate limiting)
    • Total Dose:  total dose has a significant effect on immunosuppresion and     leukemic cell kill

If single dose exceeds 10 Gy, need low dose rate to decrease risk of interstitial pneumonitis

  • if high dose rate, need to decrease total dose
  • for fractionated TBI, dose rate less important, ex: 1.5 Gy fractions or less, dose rate from 0.05-0.18 Gy/min


  • Lung attenuation
  • Bolus where it is necessary to compensate for shallower depths






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