Table 1.

Normal tissue constraints for single- and multi-fraction regimens. Multi-fraction dose constraints were calculated to be biologically equivalent to single-fraction dose constraints, assuming alpha/beta of 2

	Single-fraction	Multi-fraction (2 fraction)
Spinal Cord Planning Risk Volume*	V14 Gy < 0.03 cc V10 Gy < 0.35 cc	V19 Gy < 0.03 cc V13.5 Gy < 0.3 cc
Esophagus	V14 Gy < 2.5 cc V12 Gy < 3.8 cc V20 Gy < 0.03 cc	V19 Gy < 2.5 cc V16.5 Gy < 3.8 cc V27.5 Gy < 0.03 cc
Bowel (colon, stomach, small bowel)	V15 Gy < 0.03 cc	V20 Gy < 0.03 cc
Each kidney	Mean < 6 Gy
Each lung	V20 Gy < 3–5%; V10 < 10%; V5 Gy < 35%; mean < 5 Gy
Cauda	V16 Gy < 0.03 cc V12 Gy < 0.35 cc	V22 Gy < 0.03 cc V16.5 Gy < 0.35 cc
Nerve root/plexus	Limit D0.03cc < 105–110% of prescription dose	Limit D0.03cc < 105–110% of prescription dose

*Planning risk volume is spinal cord plus 0–2 mm margin depending on treatment platform

Abbreviations: cubic centimeter (cc), Gray (Gy), volume receiving X Gy (VX Gy), maximum dose (D0.03 cc)