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The Images sidebar allows you to simultaneously display multiple image sets that have been uploaded to the patient. This is especially useful while contouring to be able to view information from multiple image modalities (e.g., CT and MR). To view the available images for the selected patient, click the Images tab located in the right sidebar.
Displaying Multiple Image Sets
The Images sidebar contains two sections, the first lists the currently "Active" image sets in the patient. Active image sets include the primary image set (indicated by a green checkmark in the Browse tab) as well as any secondary image sets (indicated by a blue checkmark in the Browse tab). The second section lists the currently "Inactive" image sets in the patient (if available). An inactive image set will fall into one of the following cases.
- The image set is located in the same coordinate system as the primary image set, as indicated by the DICOM 'Frame of Reference UID' (0020,0052) tag.
- The image set is not located in the same coordinate system as the primary image set, but there is at least one spatial registration object (SRO) available that registers it to the primary image set.
- The image set is not located in the same coordinate system as the primary image set, and there are no spatial registration objects available that register it to the primary image set.
The following screenshot depicts how each of these are displayed in the Inactive section. The first image set in the list ("CT: ABDOMEN_RAD_PLAN mibh") is an example of an image set in the last category. It is not able to be activated by default as indicated by the "not allowed" icon and the lock button on the right. The second image set in the list ("CT: Registered CT output") is an example of an image set in the first category. It's an image set that is already in the same coordinate system as the primary image set. The third image set in the list ("MR: Registered-Everything") is an example of an image set in the second category. In other words, while the coordinate systems differ, a registration object is available to register the secondary MR image set with the primary image set. These image sets are denoted by an asterisk icon on the right.
To activate an inactive image set, simply click on the checkbox to the left of the inactive image set. Similarly, to deactivate an active secondary image set, simply uncheck the checkbox to the left of the active image set. Please note that you can not deactivate the primary image set from the Images sidebar (this can only be done by double-clicking on a different item from the Browse tab).
Unlocking Image Sets in Different Coordinate Systems
The DICOM 'Frame of Reference UID' (0020,0052) tag is how DICOM-compliant systems communicate that one or more objects are in the same coordinate space. If ProKnow DS indicates that two images are not in the same coordinate system, it implies that the source images were not transmitted with the same frame of reference and no registration object is available to register one with the other. However, in some rare cases, the frame of reference may be set incorrectly in the source DICOM files, and the images may actually be in the same coordinate system. To accommodate this scenario, ProKnow DS allows you to unlock an image set in a different coordinate system, allowing it to be displayed simultaneously with the primary image set. In these situations, it is important to understand that even though two image sets may appear to be in the same coordinate system, there may be subtle differences that are difficult to detect. As such, by unlocking an image set in a different coordinate system, you take full responsibility for ensuring that the objects are in the same coordinate system, despite the fact that the files imported to ProKnow DS indicate otherwise.
To unlock an inactive image set that does not share the same coordinate system as the primary image set and does not have a registration object available, you can click the lock icon to the right of the inactive image set. Once unlocked, you can click the checkbox to the left of the unlocked image set to activate. Please note that unlocking an image set in a different coordinate system has the following restrictions:
- It is not possible to view secondary images that are not in the same coordinate system as the primary image set while contouring. Therefore, it is not possible to unlock images while contouring, nor it is possible to start editing a structure set if there are any active patient objects that are not in the same coordinate system.
- The unlocked state of an image set is not saved with the patient state, and any activated secondary image sets that are not in the same coordinate system as the primary image set will be automatically returned to the inactive state upon reloading the patient. This is to ensure that it is not possible for a user to unknowingly view a set of images in different coordinate systems while viewing or analyzing a patient.
In the event that one or more image sets with different frames of reference are indeed in the same coordinate system, it is possible to use the Force Frame of Reference operation from the Patient Browse tab to permanently force the objects to have a consistent frame of reference.
Adjusting Image Set Display Options
Once an image set has been activated, the Images sidebar allows editing the display options for the image set, including:
- Fusion (if the image set is registered to the primary image set via one or more registration objects)
- Style (e.g., Grayscale, Inverted, Glow)
Please note that the Window/Level dropdown available from the Patient toolbar will always reflect the current display options of the primary image set (and not secondary image sets). In addition, with two image sets enabled, it is possible to synchronize the opacity of the two image sets by clicking on the Synchronize Opacity button located on the right side of the Active section header (this option is only available when there are exactly two active image sets).
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