Incomplete repair

If repair takes longer than the interval between the fractions, then the approach described in the page devoted to the simple fractionation conversion is not applicable. The following table (data taken from Basic Clinical Radiobiology) gives repair time for the normal tissues.

Table 3. Repair half time for normal tissues
EndpointRepair half time, h
Erythema, skin0.35 and 1.2
(two repair components)
Mucositis, head and neck2–4
Laryngeal oedema4.9
Radiation myelopathy> 5
Skin telangiectasia0.4 and 3.5-3.8
(two repair components)
Subcutaneous fibrosis4.4
Temporal lobe necrosis> 4
Various pelvic complications1.5–2.5

For the interval between the fractions significantly longer than the time given in the table we can assume that a complete repair took place. However, for shorter interfractional intervals complete repair does not take place leading to effectively higher dose per fraction and, therefore, worse side effects.

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