PMID- 15708278
OWN - NLM
STAT- MEDLINE
DCOM- 20050324
LR  - 20220330
IS  - 0360-3016 (Print)
IS  - 0360-3016 (Linking)
VI  - 61
IP  - 3
DP  - 2005 Mar 1
TI  - Adequate margins for random setup uncertainties in head-and-neck IMRT.
PG  - 938-44
AB  - PURPOSE: To investigate the effect of random setup uncertainties on the highly 
      conformal dose distributions produced by intensity-modulated radiotherapy (IMRT) 
      for clinical head-and-neck cancer patients and to determine adequate margins to 
      account for those uncertainties. METHODS AND MATERIALS: We have implemented in 
      our clinical treatment planning system the possibility of simulating normally 
      distributed patient setup displacements, translations, and rotations. The 
      planning CT data of 8 patients with Stage T1-T3N0M0 oropharyngeal cancer were 
      used. The clinical target volumes of the primary tumor (CTV(primary)) and of the 
      lymph nodes (CTV(elective)) were expanded by 0.0, 1.5, 3.0, and 5.0 mm in all 
      directions, creating the planning target volumes (PTVs). We performed IMRT dose 
      calculation using our class solution for each PTV margin, resulting in the 
      conventional static plans. Then, the system recalculated the plan for each 
      positioning displacement derived from a normal distribution with sigma = 2 mm and 
      sigma = 4 mm (standard deviation) for translational deviations and sigma = 1 
      degrees for rotational deviations. The dose distributions of the 30 fractions 
      were summed, resulting in the actual plan. The CTV dose coverage of the actual 
      plans was compared with that of the static plans. RESULTS: Random translational 
      deviations of sigma = 2 mm and rotational deviations of sigma = 1 degrees did not 
      affect the CTV(primary) volume receiving 95% of the prescribed dose (V(95)) 
      regardless of the PTV margin used. A V(95) reduction of 3% and 1% for a 0.0-mm 
      and 1.5-mm PTV margin, respectively, was observed for sigma = 4 mm. The V(95) of 
      the CTV(elective) contralateral was approximately 1% and 5% lower than that of 
      the static plan for sigma = 2 mm and sigma = 4 mm, respectively, and for PTV 
      margins <5.0 mm. An additional reduction of 1% was observed when rotational 
      deviations were included. The same effect was observed for the CTV(elective) 
      ipsilateral but with smaller dose differences than those for the contralateral 
      side. The effect of the random uncertainties on the mean dose to the parotid 
      glands was not significant. The maximal dose to the spinal cord increased by a 
      maximum of 3 Gy. CONCLUSIONS: The margins to account for random setup 
      uncertainties, in our clinical IMRT solution, should be 1.5 mm and 3.0 mm in the 
      case of sigma = 2 mm and sigma = 4 mm, respectively, for the CTV(primary). Larger 
      margins (5.0 mm), however, should be applied to the CTV(elective), if the goal of 
      treatment is a V(95) value of at least 99%.
FAU - Astreinidou, Eleftheria
AU  - Astreinidou E
AD  - Department of Radiotherapy, University Medical Center Utrecht, Heidelberglaan 
      100, 3584 CX Utrecht, The Netherlands. e.astreinidou@azu.nl
FAU - Bel, Arjan
AU  - Bel A
FAU - Raaijmakers, Cornelis P J
AU  - Raaijmakers CP
FAU - Terhaard, Chris H J
AU  - Terhaard CH
FAU - Lagendijk, Jan J W
AU  - Lagendijk JJ
LA  - eng
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
PL  - United States
TA  - Int J Radiat Oncol Biol Phys
JT  - International journal of radiation oncology, biology, physics
JID - 7603616
SB  - IM
MH  - Head and Neck Neoplasms/radiotherapy
MH  - Humans
MH  - Oropharyngeal Neoplasms/pathology/*radiotherapy
MH  - Radiotherapy Dosage
MH  - Radiotherapy Planning, Computer-Assisted/*methods
MH  - Radiotherapy, Conformal/*methods
MH  - Tomography, X-Ray Computed
MH  - Uncertainty
EDAT- 2005/02/15 09:00
MHDA- 2005/03/25 09:00
CRDT- 2005/02/15 09:00
PHST- 2004/05/27 00:00 [received]
PHST- 2004/11/02 00:00 [revised]
PHST- 2004/11/09 00:00 [accepted]
PHST- 2005/02/15 09:00 [pubmed]
PHST- 2005/03/25 09:00 [medline]
PHST- 2005/02/15 09:00 [entrez]
AID - S0360-3016(04)02855-X [pii]
AID - 10.1016/j.ijrobp.2004.11.016 [doi]
PST - ppublish
SO  - Int J Radiat Oncol Biol Phys. 2005 Mar 1;61(3):938-44. doi: 
      10.1016/j.ijrobp.2004.11.016.