Syntax:
    SDRX: TOD={time interval between fractions}
Example:
    SDRX: TOD=0.25                         !Dose delivered in 15 minutes (0.25 hour)
    SDRX: TOD=DD1                         !Pointer to an array dose delivery times
    DD1=0.01 0.25 0.5 1 2 5 12 24 /   !Array of dose delivery times (hour)

Purpose: Set the time when the second dose fraction is delivered.
Data Type: real
Unit: Gy/hour
Default: none
Comments:  The time interval between fractions (the TBD parameter) equals the time of deliver (TOD) minus the 0.5*{total delivered dose (TAD)}/{dose rate (ADR)}.  For an alternate method of specifying the time interval between fractions, see the TBD parameter.  Fractions are delivered at the same dose rate, and fraction size is 1/2 the total delivered dose (TAD).  To gain more control over dose fraction delivery, use the RADX: keyword.  With the RADX: keyword, multiple fractions of different sizes can be specified and a different dose rate can be used to deliver each fraction.