A scanned film image can be imported into a project in the myQA Film Panel. Before importing, the image can be calibrated and registered in the myQA Film Panel window.
Radiation response, optical density, and film calibration
The radiation response of a film, ADC (Analog to Digital Conversion), can be read as pixel values at certain positions. The software converts the ADC into optical density (OD). The OD is calculated from the ADC value from the following formula:
OD = -log10(ADC_irr/ADC_unirr),
where ADC_irr is the intensity of the pixel value for an irradiated film and ADC_unirr is the pixel intensity
value for an un-irradiated film or for an empty scan.
The Film calibration converts the optical density to dose distribution, and it is displayed as a curve of dose
as a function of OD.
Empty scan image
To compute the OD, it is possible to select an ‘Empty Scan’. This selected film can be either a scan image taken without a film inside the scanner or an un-irradiated film. Without any film selected, the software will use a default value 2bit – 1, where 2bit is the bit depth of the image.
Dose reference image
An image with several dose exposures serves for creating the calibration curve, Dose vs. OD.
Lateral correction
A scan image, named, background.tiff, or any name starting with “background”, is used for lateral
correction.
Markers on film
WARNING: MARKERS ON FILM
Markers for identification, orientation, or positioning may overlap or interfere with optical density due to radiation. Mark the films outside the region where the dose will be determined:
1. Mount the films into the phantom.
2. Mark the films (for later alignment and positioning).
Open myQA Film Panel
The myQA Film Control Panel window can be opened in the Project Explorer in two ways:
- Select a folder, click Import Film Panel in the Home ribbon in the Verification Compare workspace, or
- Right-click one of the folders in Project Explorer > select Import Film... in the sub-menu of Import new field.
In the myQA Film Panel window, the film to be imported can be opened, calibrated, registrated, and
imported into the selected folder in Project Explorer.The myQA Film Panel window includes:
1: Menu bar
2: Task Panel - contains two tabs for the two groups of tasks that can be executed for films:
o Registration - provides functions for modification of data:
o Calibration - contains functions for correction of scanner artifacts and film.
3: Display Panel - displays the selected image
4: Info Panel - contains parameters and functions related to an opened image.
5: Film List - displays thumbnails of the opened images and the Send button for sending the selected image in opened image list to the opened project.
Please see myQA Patients Reference Guide for detailed information about the myQA Film Panel.
General Procedure for Film Import
- Define the parameters in Edit > Options
Open the relevant films:
- Scan for lateral correction, e.g., background.tiff
- (Optional) empty scan image (to apply it, right-click it in the Film List, and then select Empty Scan).
If empty scan image is used, it should be used throughout the complete procedure and all relevant
images to be calibrated. - Dose reference image containing at least three known dose exposures
- Images to be calibrated.
Note: the image can be opened in the step when it is used.
Perform film registration. The available functions are:
- Defining the film orientation (Section 3.3.1)
- To flip/rotate/invert the film, click Flip/Rotate/Invert and click the desired options
- Cropping the film (Section 3.3.2)
- Film alignment (Section 3.3.3)
- Setting origin (Section 3.3.4)
Calibration:
- Create lateral correction (Section 3.4.1)
- Create film calibration (Section 3.4.2)
- Apply the calibration to the films (Section 3.4.3)
- Import the calibrated and registered film into the currently opened project (Section 3.5).
Film Registration
Define Film Orientation
- In the Film orientation section (1): Select an orientation of the films relative to the phantom.
- Enter the name of the phantom in the Name box (2).
- In the Phantom position (Rotation angle) section (3): select the rotation angle. The IEC coordinate system is used.CAUTION: CHANGE THE POSITION OF THE MARKER IF THE PHANTOM IS ROTATED
The default orientation of the body phantom is as shown in the screenshot above. If
the phantom is rotated, the position of the marker should also be changed. - Under Distance from phantom origin to film markers (4), enter the coordinates of the phantom origin and film markers (alignment points (1stAP and 2nd AP)
Crop
- Select the Crop button. A square appears on the image.
- Define the cropping area by dragging the corners of the square or enter the desired values in the X, Y, W, and H boxes.
- Select Apply.
Align
Manual definition of the alignment points
- Click Align(1); Set First Point (2) becomes green. Move the cursor to the first point on the image and press and release the mouse. The Set Second Point (3) becomes green (see screenshot above left). In the same way, select the second alignment point. The rotation angle and direction to align the two points appears (see screenshot above right). Use the Zoom function to improve precision.
- Click Rotate to the right/left (4) according to the direction shown (see screenshot above right); the
image will be rotated accordingly.
Automatic Setting of Alignment Points
- Check mark the check-box Search for registration points in Registration > Task Panel > Options.
Define the search area in Search area square side.
If the check-box Crop the rotated image is marked, the aligned film will be cropped to original size. - Search for the alignment points by clicking in the area surrounding them. The points with the lowest ADC values will be detected.
- Rotate to the right/left in the Align box: Select the rotation direction.
Set Origin
- Select by clicking Set Origin (1) or use the shortcut key, <Ctrl-O>
- Move the cursor to the desired origin in the image, and the press and release the mouse; the new origin is defined.
- Click Apply (2) or use the shortcut key <Ctrl-Shift-O>
Calibration
Calibration tab
IMPORTANT NOTICE: COLOR CHANNELS MUST BE MATCHED FOR CALIBRATION
The color channel of a calibration must match the color channel of the film. It is the
user’s responsibility to choose an appropriate calibration. For a greyscale film, only
use a greyscale calibration. For an RGB film, the ExtractChannel option must match
the calibration channel, e.g., if the red channel is extracted, only use a red channel
calibration. It is recommended to use the multi-channel calibration for an RGB film.
Create Lateral Correction
- In myQA Film Panel > Film list, click to select the image e.g., background_multiChannel.tif.
- Normally, there is area on the edge of the film not clean or not covered by the image. This area must be excluded with the Crop function (see Section 3.3.2), see an example:
A background before crop
After crop
WARNING: CLEAN IMAGE FOR LATERAL CORRECTION
Make sure the background image for lateral correction is clean. Crop it if necessary.
Otherwise, the lateral correction cannot be correctly applied. - In Task Panel and under Calibration > Lateral correction > Correction Matrix, click Calculate
correction matrix. The fitted curve and normalized curve are displayed.
Apply the lateral correction to the films
- Select the image if applying to one image or tick the checkbox of images in the Film List panel.
- Click Apply corrections. After the correction is done, the filename turns to green color.
IMPORTANT NOTICE. LATERAL CORRECTION
If lateral correction should be applied, it should be done before performing film
calibration. Lateral correction should also be applied to the dose reference scan.
Correction matrix
When clicking anywhere inside Calculate correction matrix, the fitted curves of correction factor vs.
lateral-axis pixels are generated for the selected channels.
Double-clicking anywhere inside Display Panel moves the correction curve back to Calibration tab.
Lateral correction curve, Normalized factor vs. film horizontal pixels, left: displayed in the Calibration tab, right: in Display Panel.
Note that when changing the channels, the channel tabs in the Correction Matrix box will be only updated after applying Calculate correction matrix.
Create Film Calibration
To perform film calibration, it can be chosen either using multiple films exposed to various dose levels or a single film exposed to multiple various dose levels, covering the range of interest.
WARNING: SENSITIVITY MAY VARY FROM FILM TO FILM
The sensitivity of radiographic films is strongly dependent on parameters such as
type, age, batch, or storage conditions. Perform a film calibration when using films
where one or more of the above parameters differ from the film used for the current
film calibration.
Mark the points on the scanned film where the dose is known. The points will be added in the film
calibration table with the optical density value.
IMPORTANT NOTICE: MEASUREMENT POINTS
For a valid calibration you need at least three measurement points.
- In the myQA Film Panel window, click File > Open, and then browse and open the film with known dose values for Calibration (e.g., Film Cal1_MC.tif) if it is not yet opened.
- Enter a value in the Task Panel > Calibration > Options > Measure area square side box.CAUTION: SIZE OF MEASURING AREAAfter the film is imported into the myQA Film Panel, an average filter is applied. Makesure that a suitable size for Measure area square side is set in Calibration > Options.
- In Used Calibration Info tabs click New calibration in the Task Panel. The current date is automatically entered in Calibration Info.
- Enter the proper information in the following text fields and optionally comments in the Comments box:
- Enter the film type, the batch ID, and the name of the operator.
- Select the channel(s) to be calibrated (e.g., multi channels)
- Optional: Enter additional information in the Comments field.
- (Optional) in Film List, right-click the empty scan image and select Empty Scan.
- Right-click in the image and select Show cursor in the context menu.
- Define steps: position the cursor at the point where you want to define the dose. Select Add new step. A square appears and shows the area for averaging value. The OD value is displayed in the OD column in the Calibration Data table. Repeat for each point. More points can be added by opening another dose reference image if available.
- Enter the dose value for each field in the Dose column.
- Click Save calibration to save thecalibration data as *.cal file in myQA Film Panel. To save data in the
myQA database, see Section 3.5.
IMPORTANT NOTICE: RECALIBRATION
Recalibration on a regular basis is recommended, due to variation in film quality, and especially due to variation when developing the film.
IMPORTANT NOTICE: PREVIOUSLY SAVED FILMS
Recalibration will not change the measurement values on previously scanned and saved films.
Apply Calibrations
The currently loaded calibration can be applied to non-calibrated film.
- If the film calibrations have not been loaded yet, in the Task Panel, click Calibration > Load calibration to load the desired calibration file.
CAUTION: USE CORRECT CALIBRATION FILE
The channel of a calibration must match the imported channel of film. For a greyscale film, only use a greyscale calibration. If an RGB film is imported, the ExtractChannel option must match the calibration channel, e.g., if the red channel is extracted, only use a red channel calibration. It is recommended to use multi-channel calibration for an RGB film. - Check mark the film(s) to be calibrated in the Film List panel and click Apply the current calibration to the selected non-calibration films for applying the calibrations to the selected films in the Task Panel:
To apply the current calibrations simultaneously to all films in the Film List, click Apply the current
calibration to all the films in the list.IMPORTANT NOTICE: CHECK LOADED CALIBRATION
When the Film Panel is opened, the calibrations for the selected scanner and film will be displayed in the Task Panel. Ensure that the correct calibration is loaded before applying it to the film.
WARNING: RISK OF UNPREDICTABLE RESULTS
Applying a different calibration table on an already calibrated film, a caution message will pop up. It can produce unpredicted results.
Import films to the opened project
- Check mark the film in the Film List and then click Send.
- If there are films out of range or not calibrated, a popup message will appear. Click Yes/No if they should be/not be imported:
In the Project Explorer, a new folder with the name of the import time will be created in the Import
folder containing the imported images from the myQA Fim Panel. - The properties of an imported film can be viewed with right-clicking on the image and then clicking
Properties of Film > Custom in the context menu.