PMID- 18777917
OWN - NLM
STAT- MEDLINE
DCOM- 20081105
LR  - 20170214
IS  - 0094-2405 (Print)
IS  - 0094-2405 (Linking)
VI  - 35
IP  - 8
DP  - 2008 Aug
TI  - Accuracy of TomoTherapy treatments for superficial target volumes.
PG  - 3565-73
AB  - Helical tomotherapy is a technique for delivering intensity modulated radiation 
      therapy treatments using a continuously rotating linac. In this approach, fan 
      beams exiting the linac are dynamically modulated in synchrony with the motion of 
      the gantry and couch. Helical IMRT deliveries have been applied to treating 
      surface lesions, and the purpose of this study was to evaluate the accuracy of 
      dose calculated by the TomoTherapy HiArt treatment planning system for 
      superficial planning target volumes (PTVs). TomoTherapy treatment plans were 
      developed for three superficial PTVs (2-, 4-, and 6-cm deep radially by 90 
      degrees azimuthally by 4-cm longitudinally) contoured on a 27-cm diameter 
      cylindrical white opaque, high-impact polystyrene phantom. The phantom included 
      removable transverse and sagittal film cassettes that contained bare Kodak EDR2 
      films cut such that their edges matched the phantom surface (+/-0.05 cm). The 
      phantom was aligned to the machine's isocenter (+/-0.05 cm) and was irradiated 
      according to the treatment plans. Films were scanned with a Vidar film digitizer, 
      and optical densities were converted to dose using a calibration determined from 
      a 6 MV perpendicular film exposure. This perpendicular calibration required that 
      axial film doses (parallel irradiation) be scaled by 1.02 so that mid-arc depth 
      doses matched those measured in the sagittal plane (perpendicular irradiation). 
      All film readings were scaled by 0.935 to correct for over-response due to 
      phantom Cerenkov light. Measured dose distributions were registered to calculated 
      ones and compared. Calculated doses overpredicted measured doses by as much as 
      9.5% of the prescribed dose at depths less than 1 cm. At depths greater than 1 
      cm, calculated dose distributions showed agreement to measurement within 5% in 
      the high-dose region and within 0.2 cm distance-to-agreement in the dose falloff 
      regions. In the low-dose region posterior to the PTVs (<10% of the prescribed 
      dose), the dose algorithm underpredicted the dose by 1%-2% of the prescribed 
      dose. Clinically, it is recommended that 1 cm of bolus be used on the surface to 
      ensure that cancerous tissues less than 1 cm depth are not underdosed.
FAU - Cheek, Dennis
AU  - Cheek D
AD  - Mary Bird Perkins Cancer Center, Baton Rouge, Louisiana 70809, USA. 
      dcheek@billingsclinic.org
FAU - Gibbons, John P
AU  - Gibbons JP
FAU - Rosen, Isaac I
AU  - Rosen II
FAU - Hogstrom, Kenneth R
AU  - Hogstrom KR
LA  - eng
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
PL  - United States
TA  - Med Phys
JT  - Medical physics
JID - 0425746
RN  - 0 (Polystyrenes)
SB  - IM
MH  - Algorithms
MH  - Calibration
MH  - Humans
MH  - *Phantoms, Imaging
MH  - Polystyrenes
MH  - *Radiation Injuries/prevention & control/radiotherapy
MH  - Radiometry/instrumentation
MH  - Radiotherapy Dosage
MH  - Radiotherapy, Computer-Assisted/instrumentation/*methods/standards
MH  - Sensitivity and Specificity
EDAT- 2008/09/10 09:00
MHDA- 2008/11/06 09:00
CRDT- 2008/09/10 09:00
PHST- 2008/09/10 09:00 [pubmed]
PHST- 2008/11/06 09:00 [medline]
PHST- 2008/09/10 09:00 [entrez]
AID - 10.1118/1.2952362 [doi]
PST - ppublish
SO  - Med Phys. 2008 Aug;35(8):3565-73. doi: 10.1118/1.2952362.