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The IMRT phantom offers simple, highly reliable dose validation of complex 3D treatment plans.
The principle behind the IMRT phantom is to create a film spiralgram of the treatment dose along a mathematically precise path to obtain a three dimensional sampling of a treatment plan.
The phantom design is based on research conducted in the Departments of Human Oncology and Medical Physics at the University of Wisconsin**.
For verification, apply the treatment plan for the patient to the phantom. Load the film into the spiral of the phantom and execute the treatment plan. When the film is developed, compare it to the predicted treatment plan.
The phantom is enclosed in a light-tight cassette incorporating a locating pin to register the phantom with the CT or linear accelerator coordinate system and lines to ensure proper alignment. A 7 x 43 cm strip of film is loaded into the phantom by sliding it into the slot from the locating pin position until it contacts the ion chamber adapter.
The phantom has provisions for an optional adapter for a customer-specified cylindrical ion chamber. A blank plug is included if the use of an ion chamber is not desired.
**Paliwal, Bhudatt, Wolfgang Tome, Susan Richardson and T. Rockwell Mackie. A spiral phantom for IMRT and tomotherapy treatment delivery verification. Medical Physics, November 2000: 2503-2507.
OTHER MATERIAL/EQUIPMENT NEEDED
Laser alignment tools
Densitometer or laser film digitizer
Computer with spreadsheet software
Metric ruler or caliper
Light box
Biopsy needle or other sharp implement for marking film
Kodak EDR2 film (or equivalent)
RIT® or other software for final analysis
Spreadsheet program
Specifications
Phantom Construction
Cassette cover indexes to insert and is marked with scribe lines at 90° intervals for alignment purposes
Fiducial film marking system to indicate relationship to circumferential scan plane and to properly scale the exposed photographic film
Matrix Material: Solid Water® water equivalent material
Cylindrical Insert Dimensions: 14.4 cm diameter x 7.0 cm thick
Cassette Dimensions: 18.0 cm diameter x 8.0 cm thick
Plug Dimensions: 2 cm diameter x 7.5 cm long
Spiral Slot Dimensions: 0.4 mm slot width x 7 cm slot depth
Film Location Accuracy: ±0.5 mm, relative to external coordinate markers
Phantom/Cassette Weight: 4.68 lbs.(2.12 kg)
Operating Temperature Range: 15°C to 35°C (59°F to 95°F)
Storage Temperature Range: -30°C to 50°C ( -22°F to 122°F)
Film Requirements
Film Type: Kodak EDR2 recommended, cut to appropriate dimensions
Film Dimensions: 7.0 cm x 43.0 cm
Optional Accessories
Ion Chamber Adapter Dimensions: 2 cm diameter x 7.5 cm long, fits most common thimble-type ion chambers and default center of active volume is at center of phantom.
Phantom stand for CT and Linac setup
Phantom carrying case
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