73mm Cube, Acrylic with One 2mm Titanium Ball

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73 mm Cube, Acrylic with One 2 mm Titanium Marker

This Cube can be used to do a modified Winston-Lutz test for lmage Guided Radiation Therapy (IGRT) accuracy.  The phantom will provide a means to test the isocenter coincidence from CT scan to treatment planning system to treatment delivery.

The accuracy of radiation isocenter relative alignment and couch shift process is of fundamental importance in the accuracy of delivered dose in IGRT. Item 710-032, the 73 mm Cube, has one central axis titanium ball for the testing and verification of predetermined measurable couch shifts.  This phantom can be used to test the accuracy of CBCT alignment and couch shift in a simple and efficient manner. Images can be transferred to the treatment planning system to check coincidence of treatment planning system to couch shifts.

It is, therefore, critical to ensure the coincidence of these two coordinate systems for different clinical needs of image-guided radiation therapy procedures. The QA item “imaging and treatment coordinate coincidence” is aimed to test this coincidence and is applicable for each of the imaging systems considered. In addition, each system performing patient positioning and/or repositioning based on in-room imaging systems, either 2D or 3D, relies upon vendor software that compares and registers on-board images and reference images.  Quality assurance of this process could be easily done by a phantom study with known shifts and is recommended for each system used clinically. The accuracy of this process should be tested on the daily basis, especially for SRS/SBRT.

Like the original Winston-Lutz test, the isocenter coincidence test is an end-to-end QA procedure in that it must start with the planning imaging process and end with the treatment step. In this case the last step is the use of the treatment beam to both irradiate and image the markers using the treatment beam.

The 73 mm Cube is made of acrylic with three sides each having a white vinyl label with the alignment markings as seen above. The titanium ball can be seen on the other three sides.

Specifications
Ball Marker Location in Cube: at isocenter: X; Y; Z=0
Ball Marker Diameter: 2 mm
Ball Marker Material: Titanium
Alignment Markings
            Central axis: 4 mm long dashes
            X, Y, and Z: At 1 cm and 2 cm from central axis, 1 cm long dashes
Cube Material: Acrylic, with white vinyl and matte silver polyester labeling
Cube Size: 2.875 x 2.875 x 2.875 in (73 x 73 x 73 mm)

Related Items
710-033   Winston-Lutz 73 mm Acrylic Cube with 6 mm Tungsten Ball
710-034   Winston-Lutz 73 mm Acrylic Cube with 6.35 mm Titanium Ball
710-036   73 mm Acrylic Cube with Three 2 mm Titanium Markers