PMID- 20071767
OWN - NLM
STAT- MEDLINE
DCOM- 20100311
LR  - 20131121
IS  - 1361-6560 (Electronic)
IS  - 0031-9155 (Linking)
VI  - 55
IP  - 3
DP  - 2010 Feb 7
TI  - Stereotactic fields shaped with a micro-multileaf collimator: systematic 
      characterization of peripheral dose.
PG  - 873-81
LID - 10.1088/0031-9155/55/3/021 [doi]
AB  - Despite the highly localized doses that may be delivered via stereotactic 
      radiotherapy, a small dose is nonetheless delivered to out-of-field regions, 
      which may cause detriment to the patient. In this work, a systematic set of dose 
      measurements have been undertaken up to a distance of 45 cm from the isocentre, 
      for stereotactic fields shaped by a BrainLAB mini-multileaf collimator (MMLC) 
      mounted on a Varian 600C linear accelerator. A range of treatment parameters were 
      varied so as to determine the factors of greatest influence and establish 
      relationships with dose. The commercial treatment planning software (TPS) 
      miscalculates the dose to out-of-field regions. Measured dose decreases 
      consistently out to 45 cm, whereas the TPS decreases out to 10-15 cm, at which 
      point the predicted dose is constant. At the 5-10 cm off-axis distance (OAD), 
      measurements indicate doses of about 5-10% of the dose at the isocentre, 1% at 15 
      cm OAD and 0.1% at 45 cm OAD. There are several observed trends. Greater MMLC 
      field sizes (with static jaw) result in higher out-of-field dose, as do shallower 
      depths. The source-to-surface distance does not greatly influence peripheral 
      dose. However, the results given in this work do indicate that simple treatment 
      arrangements, such as preferable collimator rotation, would in certain cases 
      reduce out-of-field dose by an order of magnitude. Peripheral dose raises 
      questions of treatment optimization, particularly in cases where patients have a 
      long life expectancy in which secondary effects may become manifest, such as in 
      the treatment of paediatric patients or those with a non-malignant primary. For 
      instance, for a 20 Gy hypo-fractionated treatment, dose to out-of-field regions 
      is of the order of cGy-a substantial dose in radiation protection terms.
FAU - Taylor, M L
AU  - Taylor ML
AD  - School of Applied Science, RMIT University, GPO Box 2476, Melbourne, Victoria 
      3000, Australia. michael.taylor@rmit.edu.au
FAU - McDermott, L N
AU  - McDermott LN
FAU - Johnston, P N
AU  - Johnston PN
FAU - Haynes, M
AU  - Haynes M
FAU - Ackerly, T
AU  - Ackerly T
FAU - Kron, T
AU  - Kron T
FAU - Franich, R D
AU  - Franich RD
LA  - eng
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
DEP - 20100114
PL  - England
TA  - Phys Med Biol
JT  - Physics in medicine and biology
JID - 0401220
RN  - 059QF0KO0R (Water)
SB  - IM
MH  - Humans
MH  - Particle Accelerators/instrumentation
MH  - Phantoms, Imaging
MH  - Radiometry/*methods
MH  - Radiosurgery/*instrumentation
MH  - *Radiotherapy Dosage
MH  - Radiotherapy Planning, Computer-Assisted/instrumentation/*methods
MH  - Software
MH  - Water
EDAT- 2010/01/15 06:00
MHDA- 2010/03/12 06:00
CRDT- 2010/01/15 06:00
PHST- 2010/01/15 06:00 [entrez]
PHST- 2010/01/15 06:00 [pubmed]
PHST- 2010/03/12 06:00 [medline]
AID - S0031-9155(10)29996-7 [pii]
AID - 10.1088/0031-9155/55/3/021 [doi]
PST - ppublish
SO  - Phys Med Biol. 2010 Feb 7;55(3):873-81. doi: 10.1088/0031-9155/55/3/021. Epub 
      2010 Jan 14.