Evaluation of dose prediction errors and optimization convergence errors of deliverable-based head-and-neck IMRT plans computed with a superposition/convolution dose algorithm.
The purpose of this study is to evaluate dose prediction errors (DPEs) and optimization convergence errors (OCEs) resulting from use of a superposition/convolution dose calculation algorithm in deliverable intensity-modulated radiation therapy (IMRT) optimization for head-and-neck (HN) patients. Thirteen HN IMRT patient plans were retrospectively reoptimized. The IMRT optimization was performed in three sequential steps: (1) fast optimization in which an initial nondeliverable IMRT solution was achieved and then converted to multileaf collimator (MLC) leaf sequences; (2) mixed deliverable optimization that used a Monte Carlo (MC) algorithm to account for the incident photon fluence modulation by the MLC, whereas a superposition/convolution (SC) dose calculation algorithm was utilized for the patient dose calculations; and (3) MC deliverable-based optimization in which both fluence and patient dose calculations were performed with a MC algorithm. DPEs of the mixed method were quantified by evaluating the differences between the mixed optimization SC dose result and a MC dose recalculation of the mixed optimization solution. OCEs of the mixed method were quantified by evaluating the differences between the MC recalculation of the mixed optimization solution and the final MC optimization solution. The results were analyzed through dose volume indices derived from the cumulative dose-volume histograms for selected anatomic structures. Statistical equivalence tests were used to determine the significance of the DPEs and the OCEs. Furthermore, a correlation analysis between DPEs and OCEs was performed. The evaluated DPEs were within +/- 2.8% while the OCEs were within 5.5%, indicating that OCEs can be clinically significant even when DPEs are clinically insignificant. The full MC-dose-based optimization reduced normal tissue dose by as much as 8.5% compared with the mixed-method optimization results. The DPEs and the OCEs in the targets had correlation coefficients greater than 0.71, and there was no correlation for the organs at risk. Because full MC-based optimization results in lower normal tissue doses, this method proves advantageous for HN IMRT optimization.
Mihaylov
I B
IB
Department of Radiation Oncology, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205, USA. ibmihaylov@uams.edu
Siebers
J V
JV
D000465:Algorithms; D006258:Head and Neck Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D006801:Humans; D009010:Monte Carlo Method; D011237:Predictive Value of Tests; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*
Phys Med Biol. 2007 Oct 7;52(19):N439-47
17881794
Med Phys. 1998 Jun;25(6):867-78
9650174
Med Phys. 1998 Jan;25(1):1-11
9472820
Med Phys. 2001 Apr;28(4):582-9
11339755
Phys Med Biol. 2000 Sep;45(9):2483-95
11008950
Phys Med Biol. 2004 May 7;49(9):1671-87
15152923
Med Phys. 2003 Jul;30(7):1909-13
12906209
Phys Med Biol. 2000 Aug;45(8):2163-83
10958187
Phys Med Biol. 2005 Mar 7;50(5):869-78
15798261
Med Phys. 2002 Jun;29(6):952-9
12094990
Int J Radiat Oncol Biol Phys. 2001 Aug 1;50(5):1339-49
11483347
Med Phys. 2007 Apr;34(4):1244-52
17500456
Phys Med Biol. 2000 Jul;45(7):1731-40
10943915
Phys Med Biol. 2000 Dec;45(12):3601-13
11131187
Med Phys. 2007 Jul;34(7):2853-63
17821993
Med Phys. 2000 Apr;27(4):701-11
10798692
Int J Radiat Oncol Biol Phys. 2004 Oct 1;60(2):374-87
15380569
Med Phys. 2002 Jul;29(7):1514-27
12148734
Med Dosim. 2001 Summer;26(2):157-68
11444518
Int J Radiat Oncol Biol Phys. 2006 Mar 1;64(3):968-77
16458782
Phys Med Biol. 1999 Dec;44(12):3009-26
10616151
Int J Radiat Oncol Biol Phys. 2005 Jan 1;61(1):239-49
15629617
Phys Med Biol. 2002 Sep 7;47(17):3225-49
12361220
Acta Oncol. 1987 Jan-Feb;26(1):49-56
3109459
Med Phys. 1997 Apr;24(4):505-17
9127300
Med Phys. 1999 Oct;26(10):2133-43
10535630
Med Phys. 2006 Nov;33(11):4033-43
17153383
Int J Radiat Oncol Biol Phys. 2003 Jun 1;56(2):573-85
12738335
Phys Med Biol. 2005 Mar 7;50(5):817-30
15798257
Phys Med Biol. 2005 Mar 7;50(5):879-90
15798262
Phys Med Biol. 2002 Feb 7;47(3):391-407
11848119
Radiother Oncol. 1988 Mar;11(3):239-48
3283850
Med Phys. 2002 Nov;29(11):2705-17
12462739
Med Phys. 2006 Apr;33(4):828-39
16696458
Med Phys. 1995 May;22(5):503-24
7643786
Radiother Oncol. 1984 Dec;2(4):275-92
6522641