Beam Toolbar

Upon creating or selecting a beam from the plan toolbar, the beam toolbar is displayed. The user must first pick the treatment machine with the provided option menu. Thereafter the treatment machine may not be changed. On the toolbar the plan name is shown to the right of the return button. An option menu is next shown for the beam. A different beam may be selected with this option menu among beams in the plan. An option menu follows showing the treatment machine, but other choices are grayed out once a machine is selected. Next is an active toggle button. The beam may be selected to be inactive (out), in which case the beam is not displayed or computed. The energy is next selected with an option menu. Be careful to select the energy desired for dual energy treatment machines.

Move

Under the Move pulldown are controls to set the isocenter position, the couch, gantry, and collimator angles, and depth of isocenter or source to surface distance.

Move Isocenter

Move Isocenter Popup Control

The move isocenter popup provides control for setting the isocenter in terms of couch coordinates. Couch lateral corresponds to the IEC accelerator X axis. Couch longitudinal corresponds to the Y axis and couch height to the Z. Each control has a coarse wheel that changes the coordinate in increments of 1 cm, a fine wheel that changes in increments of 0.1 cm, and a text field where the coordinate can be typed but must be completed by hitting the Enter key. The wheels have areas at each end where they may be moved in single increments with a mouse click, and a home button that resets to zero or the default value for that coordinate.

While the coordinates are changed, the beam will be drawn in frames that are displaying the plan.

A pulldown menu is provided to set the isocenter at the location of another beam in the same plan.

Move Angles

Move Angles Popup Control

The gantry, collimator, and couch angles may be set here. Also, an arc may be set by setting the Gantry Arc control to a non-zero value.

A pulldown menu is provided to set the current beam parallel opposed to an existing beam (including itself) in the same plan.

Set Depth and SSD

A control is provided set the depth of isocenter or the source surface distance (SSD) of the beam. When specifying the depth or SSD, isocenter will slide along the present central ray to meet the depth or SSD specification. In order for this to happen the central ray must intersect the body skin boundary volume. If the central axis ray does not intersect the body outline, the depth and SSD text fields will be blank. When this control is up, the SSD and depth will be reported as the beam is otherwise moved.

Set Depth and SSD Popup Control

Visual Aid

The visual aid will show the accelerator in its current rotated state and serves as an aid in understanding the geometry of a particular beam. The skin boundary is displayed on the couch top. The name of the beam is in the lower left hand corner.

Options

Options for the Dosimetry Check program include to select the measured field to be associated with the beam. Also, the color used to draw the beam can be changed. The color is used when the beam’s toolbar is not displayed. For moving the beam the overlay color used for all drawing is used (if 24 plane graphics, XOR operation is used). BEV and computed radiographs are also available.

Read Measured Field

Upon retrieving a plan, a plan function will run to search for field dose files for beams not associated with a field dose. The program looks for files that have the beam name in the file name. If a file could not be found or you need to change the field dose, you can reselect the field dose file here. Note below that you can also read in more than one field dose file to add. In search for the beam name in the file name, -, _ and spaces are not considered, nor case.

The current choices are to read a field dose array file written by the Field Dose function or other functions that result in a field dose file, such as utilities that read EPID integrated image files or other electronic devices such as the PTW 729 ion chamber array or the MapCheck diode array. Here images have been located in beam’s eye view coordinates and converted to relative monitor units using a calibration curve or constant. An exception is made for images from an EPID that does not rotate with the collimator angle. For those devices, the program will set the collimator angle back to zero upon reading of the Field Dose file here, since the data is in the un-rotated position.

You may select more than one field dose file for a beam. Doing so will result in the two files being added together. This option is provided for the case as when a carriage shift might be required with the Varian MLC and each shift is integrated separately. The field dose files to add must all have the same pixel size, distance, and image size.

The program will create a screen of empty frames to display the field dose images unless you pre-select an empty frame. On the file selection popup, select the field dose file for the current beam. If you hit the apply button, the field dose will be displayed in the currently selected empty frame, then the beam toolbar will be set to the next beam and the next empty frame will be selected. Continue to hit the apply button after selecting the field dose image file, but be sure to check that you are selecting the correct file for the currently selected beam as shown on the beam’s toolbar option menu. Hitting the OK button instead of the apply will end the selection process after the current selection.

Show Field

There is also an option to redisplay this field dose image again by first selecting an empty frame and then selecting the Show Field function under the Options menu pulldown.

Show Field Information

Selecting this option will display information about the field fluence as to what files were read and the calibration and deconvolution parameters.

Computed Radiograph and BEV

A computed radiograph and BEV may be selected to be displayed. A BEV is a solid model 3D perspective with the eye at the source of x-rays. A computed radiograph may be in the background or may appear by itself. If the beam is moved, the computed radiograph will be erased.

The computed radiograph is selected under the Options pulldown.

Computed Radiograph Toolbar

Select an empty frame (by clicking the mouse on the large button occupying an empty frame). You can create a screen of empty frames with the Screen Control button (lower right and side of the main program window).

The contrast enhancement slider will raise CT numbers to the power selected to simulate photoelectric effect. Four is a good choice. You can add the computed radiograph (or DRR for Digitally Reconstructed Radiograph) to an existing BEV for the beam, or create a new BEV with the computed radiograph as background, or you can show the DRR by itself.

Example DRR for an oblique field.

An example DRR is shown below, with corresponding outlined regions of interest.

The Frame Control at the bottom of the 3D frame may be used to control objects being drawn.

Utilities

A utility exist to dump a 3D dose matrix for the beam to a file. This binary file will have the dose matrix in beam’s eye view coordinates, in the units of centiGray. The file is used by program AnalyzeBeam to compare computed dose to that measured with scanning equipment. Computed and measured beam profiles may then be plotted together for comparison purposes. This option is generally used for quality control purposes.

Machine Geometry File

The geometry of the treatment machine is specified in the Geometry file in the subdirectory of the treatment machine. All machines are stored in the directory specified by the BeamData.loc file in the program resources directory. Each machine occupies a subdirectory under that directory and contains a Geometry file.

The Geometry file contains information about the treatment machine. An example file is shown in the section on BeamData. Of importance here is the definition of directions and coordinates for the treatment machine parameters. For example, the gantry angle at which the machine points at the floor and the direction of rotation that represents an increase in that angle. This file should be edited to fit your machine. The beam coordinates are stored in IEC coordinates and the Geometry file is used to translate those coordinates to the user interface. Changing the definitions of the accelerator’s coordinates system will not change the location of existing beams.