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Tutorial 1.4 Multi-fraction radiation treatments
How to set up radiation exposure scenarios
Examples 1 through 4 illustrate methods of setting up exposure scenarios to mimic several multi-fraction external beam radiation therapy (EBRT) treatments.  For additional discussion, see Multi-Fraction Radiation Treatments in the Examples section of the manual.
 
Example 1 A multi-fraction radiation treatment (rt1.inp, rt1.out)
 
! 30 daily 2 Gy fractions (total dose = 60 Gy)
! Fractions are delivered in 8 minutes (FDT parameter)
! on weekdays (see WDO parameter in Example 4.3).
XBRT: TD4F=2 NTD=30 FDT=8
 
 
Example 2 A step-and-shoot IMRT treatment example (rt2.inp, rt2.out)
/*
30 daily 2 Gy fractions (total dose = 60 Gy). Fractions are delivered on weekdays as a series of 9 radiation (high dose rate) pulses separated by 3 minutes. The total time to deliver each fraction is approximately
(24 minutes) = (NBD-1)*TTO.
*/
XBRT: TD4F=2 NTD=30
DFDM: ADR=10000 NBD=9 TTO=3
 
Comments:
  • Time required to deliver each of the 9 pulses: DOX=AD/ADR, DOX=(2/9)/10,000=0.08 sec, negligible compared to TTO=3 min.  Therefore, the approximate time to delivery deliver each fraction = (NBD-1)*TTO=24 minutes.
 
Example 3 Step-and-shoot IMRT treatment example with multiple daily fractions (rt3.inp, rt3.out)
                                                            
/*
Treatment baseline scenario calls for 15 treatment including weekends (See WDO option).  Each day consists of two fractional deliveries.
  a) 0.25Gy fraction delivered at 8 a.m.
  b) 1.75Gy fraction delivered at 1 p.m.

Fractions are delivered as a series of 9(high dose rate, 10,000 Gy/h) radiation pulses separated by a 3 minute time interval (TTO=3).  The baseline exposure scenario is repeated 11 times (rescaling) for which the total treatment  dose is varied between 50 and 60 Gy in steps of 1 Gy. OPT=1 achieves the rescaling by multiplying the baseline dose rate by a constant scaling factor to suit the desired treatment dose.
*/
XBRT: NTD=15 TD4F=DD1 TMX=TT1 TTD=DD2 OPT=1 WDO=N
DD1=0.25 1.75 / !0.25 Gy followed by 1.75 Gy
TT1=8 13 / !1st fraction at 8 am, 2nd fraction at 1 pm.
DD2=50 51 52 53 54 55 56 57 58 59 60 /  !total treatment dose
 
! Specify additional details of the way each fraction is delivered.
DFDM: ADR=10000 NBD=9 TTO=3
 
Comments:   
  • Input contains for 11 treatment protocols (50 to 60 Gy total).
 
Example 4 Step-and-shoot IMRT.  The overall treatment design is the same as in Example 4.3.  However in this example, the temporal pattern of the radiation delivered in each fraction is quite different than the one generated in Example 4.3 (rt4.inp, rt4.out).
 
/*
Compare the output file from Example 4.3 to the output file generated by Example 4.4.
*/
XBRT: NTD=15 TD4F=DD1 TMX=TT1 TTD=DD2 OPT=1 WDO=N
DD1=0.25 1.75 / !0.25 Gy fraction then a 1.75 Gy fraction.
TT1=8 13 /      !1st fraction at 8 am, 2nd fraction at 1 pm.
DD2=50 51 52 53 54 55 56 57 58 59 60 /  !total treatment dose
 
!Specify additional details of the way each fraction is delivered.
DFDM: NBD=9 TTO=3 ADR=DR1 BSEQ=SQ1 RBI=BI1
BI1= 1 100 1 1 1 1 1 1 100 / !relative beam intensity
SQ1= 2 9 1 3 4 5 6 7 8 /     !beam sequence
DR1= 100 10000 100 100 100 100 100 100 10000 / !dose rates (Gy/h)
 
! An equivalent method to the one specified above is:
! BI1 = 100 100 1 1 1 1 1 1 1 /         
! SQ1 = 1 2 3 4 5 6 7 8 9 /
! DR1 = 10000 10000 100 100 100 100 100 100 100  /
 
 
Suggested Problems: For all of the sample problems, use RIO to process the input file into an output file.  Verify that the RIO application generates the desired exposure scenario.  Debug as necessary.
  1. Setup an input file to generate a treatment plan that uses 18 treatment days, including weekends. Each daily dose of radiation is delivered in two fractions of 0.9 Gy (total dose per day is 1.8 Gy).  The first fraction is delivered at 9:00 a.m. and the second fraction is delivered at 3:00 p.m. All fractions are delivered at an effective dose rate of 18 Gy/h (0.9 Gy delivered in 3 minutes).
  2. Modify the input file from problem 1 so that a total treatment dose of 60 Gy is delivered over the 30 treatment days.  In this treatment scenario, patients are not treated over the weekend.
  3. Explain why the alternative method specified in Example 4.4 will yield similar results to the method actually used in the example. Setup a input file to generate a similar treatment scenario using a method other than the one used in Example 4.4.
  4. Can the parameters: RBI and ADR be manipulated in example 4.4 such that they result in no differences in the respective RIO output files?
  5. What is the effect of different beam sequences for a chosen fixed set of dose rates and relative beam intensities? Discuss the use of the BSEQ parameter.
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Last updated: 10 June, 2011
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