Isocenter Registration Panel Overview

• Fiducial are assigned after acquiring an image using the ‘Fiducial management’ tool of the ‘Image viewer and editor’.
• Registration is carried out using ‘Fiducial fit’ tool of the ‘Image comparer’.

Fiducial management

Fiducial marks are assigned to the dose map scan using ‘Image Viewer and Editor’ tool and the registration is carried out using the ‘Image Comparer’ tool.

The tool items are as follows:

1. Detect fiducials: Starts fiducial detection process
2. Only show all fiducials: Shows fiducial only, no editing possible
3. Set and modify fiducials: Enables fiducial editing
4. Image fiducial type: Selects the fiducial type used to create new fiducials, if a fiducial is currently selected the type is changed accordingly. Available fiducial types depends on the type of the selected image
5. Rotate, flip fiducials: Rotates and flips all fiducials relative to the image center.
6. Copy, paste fiducials:
   Copy fiducials: Copies fiducial data to clip board to be pasted either in FilmQA Pro or as CSV table (e.g. Excel)
   Paste fiducial data: Pastes fiducial data using selected scaling mode relative to the image the fiducials are pasted in.
7. Delete: Deletes all fiducials or all fiducials of a specified type.
8. Known fiducial pattern: List of known fiducial pattern. Allows to add current fiducials as pattern to a list or to select a fiducial pattern from this list. List can be save to a file. The fiducial pattern list is saved together with the configuration of the control.
9. Known registration templates: List of known registration templates. Allows to add current registration template to a list or to select a registration template from this list. List can be save to a file. The registration template list is saved together with the configuration of the control.
10. Configure registration template algorithm: Start fiducial registration template editor.
11. Load registration template: Load registration template from file.
12. Save current registration template: Save registration template to file. Template is save as list with a single entry, i.e. it can also be loaded as known registration template list.
13. Options: Select what fiducials are displayed and when they are displayed.
14. Options image fiducials: Set fiducial properties like color, line and marker width.

To assigning fiducials click with the tip of the mouse cursor at the marks in the target film.

The following fiducial types can commonly used:

general fiducial, data are fitted in x and y direction,

horizontal fiducial, data are fitted in y direction,

vertical fiducial, data are fitted in x direction.

marker fiducial,

axis origin, used to set coordinate origin in charts

isocenter, marks isocenter position (projection)

Tip: To move a fiducial select it and use the Ctrl+Arrow keys, to delete select a fiducial then press Del key.

Image registration

Select the Image comparer tool in the case data selector. By default (auto select), the assigned fiducials are fitted to the isocenter marked by the blue/black dashed lines.

The tool items are as follows:

1. Fit fiducials horizontally, vertically and rotationally: Matches fiducials to isocenter adjusting offset in x and y direction and rotation angle. This is most general case for a fit.
2. Other fiducials fits: Reduced fitting configurations.
3. Fiducial auto fit: Sets conditions when fiducial are fitted automatically and what fit is carried out.
   Tip: If the auto fit overwrites current settings use the undo button to regain previous registration
4. Registration type:
   Fit registrant fiducials to isocross of reference: Vertical, horizontal and general fiducials of the registrant are fitted to the isocross lines of the reference (plan). Example below shows fit of fiducials to isocross (blue/black dashes).
   
   Fit registrant fiducial pattern to pattern of reference: If registrant and reference image have similar fiducial pattern (same number of general fiducials and markers) registrant is rotated and shifted so that offset between pattern is minimized. Example below shows fitted Accuray Ball-Cube fiducial pattern including 4 general fiducials.Adjust isocenter offset only: Shifts isocenter of the registrant to match the isocenter of the reference image (plan) - there is no rotational adjustment.
   Auto switch: Switches to applicable registration type, i.e. if both registrant and reference image have similar pattern (same number of general fiducials and markers) pattern fit is applied. Otherwise fiducials are fitted to the isocenter or if only isocenters are available the offset is adjusted.

The registrations results are displayed underneath the middle section in the control area.

Beside the fiducial based registration of the registrant image, the registration can be adjusted manually, e.g. to find the best shift and rotation of the dose map compared to the plan so that the offset between fiducials and isocenter is minimized.

A: Rotates the registrant around set rotation pole (use the button to modify rotation pole). Current rotation angle is shown in B.
Tip: Select wheel, than use arrow keys to change rotation angle stepwise.

B: Registration offset (shift) and rotation. Measurement unit same as axis unit above.

C: Shifts registrant by fixed amount.
Tip: Select pad, than use arrow keys to shift stepwise.

D: Maximum (and minimum) of the dose range of the reference image (plan). When changed the plan scaling is changed, this should Not be necessary in general!

E: average offset of the fiducials vs the isocenter are displayed at the as ’Δ fiducials’; using the same units as used at chart axis (see above). Right click for additional options:

Fiducial Zero reference: Uses current registrant as zero reference, i.e. any displayed offset will be with respect to this registration.

Show offset angle / Show offset norm: Toggles display between angle (direction) of registration offset or norm (absolute length) of registration offset.

Toggle between big ands small step size of rotation whell and step pad. Right click for more options (step size selection).

Rotates and flips registrant image (dose map) relative to reference image (plan). Isocenter match always includes 8 solutions that can be generated using horizontal and vertical flip and 90° rotation.

Save, select, lock or reset current registration.

Keep coordinate system when image unregistered: When selected, previous registrations settings are used for new (unregistered) image.

Lock coordinate system: Current registration settings are locked and no change is possible.

Registrant image scaling: Chart axis are assigned using registrant image (dose map) units (e.g. pixel)

Reference image scaling: Chart axis are assigned using reference image (plan) units Undo and redo last registration change. Right click undo or redo multiple steps or select options.