MOD PLAN

The complete quality control requires three scanner acquisitions:

• The first with a wide field of vision sufficient to view the entire OTP-PLAN test object set up in contact with the examination couch whose flatness is being tested;
• Followed by two acquisitions in which the phantom is aligned on the external lasers. It is first performed with a narrow field of view centred around the central cube of the test object. The second tests the angular alignment of the external lasers on the scanner and is performed with a wide field of view in order to capture the entire OTP-PLAN test object.

The automated analysis consists in detecting in the scanner images:

• From the first and the third and last acquisition, the 4 centring crosses contained in the 4 cubes of the OTP-PLAN phantom to compare their respective positions in the images with their actual positions in the test object. The flatness of the examination couch, the CT scanner’s respect of the distances in the cross-sectional slice, and the alignment of the external lasers with the CT scanner can then be derived from the comparisons.
• From the second zoomed acquisition, the centring cross of the central cube of the OTP-PLAN phantom in order to derive the precise alignment of the origin of the external positioning lasers on the origin of the CT-scanner slices.