It is important for all users of ClearCanvas Vetstation (hereafter, the "software" or "workstation") who will be involved in any capacity in the treatment or diagnosis of patients to fully read and understand these instructions. Failure to read these instructions and any other documentation cited in this section could result in incorrect usage of the software, which could ultimately affect patient outcome.
In general, before beginning any form of diagnosis or treatment, an assessment of whether or not the data presented is complete and correct should be performed by the user. If there is any question as to whether or not the data being presented is complete and correct, the user must take appropriate steps to ensure that it is before continuing. This may include, for example, verifying the number of images reported by the software versus the number on a PACS for the same imaging study, or contacting a PACS administrator to resolve the issue.
Hardware and Software
Make sure you follow all instructions in the Installation section of this guide, and only install the software on systems that meet or exceed the minimum system requirements. Display devices, including printers, must be clinical grade and must undergo evaluation in their intended configuration before being used. The evaluation, and any required calibration or maintenance steps, should be performed at regular intervals. Any changes to the display configuration should be followed by an immediate re-evaluation.
Exclusions from Diagnostic Use
This section discusses certain types of images that, although the software can display them, should not be used for diagnostic purposes.
Enhanced MR/CT Images
The software should not be used for primary diagnosis on Enhanced MR and CT images. Although these images can be opened for display, the per-frame data (in multi-frame functional groups) is not read by the software, and therefore the information presented will be incomplete. An example would be the information on the text overlay, which will be incomplete for all Enhanced CT or MR images.
Lossy Compressed Images
Lossy compressed images displayed by the software will show the text "LOSSY" in yellow on the text overlay, along with the compression ratio(s). Images can be lossy compressed generally for one of 2 reasons:
|1.||the modality that originally created them stored them in a lossy compressed format.|
In this situation, whether or not the images are appropriate for diagnosis is dependent on the intended use of the modality and the images it produces.
|2.||the images have been lossy compressed by a storage device, such as a PACS system.|
Such images should never be used for diagnosis, but rather the original images should be used. This includes images that were originally lossy compressed, and have been compressed further by a storage device.
See "Indications for Use" on the Welcome page.
Measurements performed on images in the Vetstation are entirely dependent on the calibration of the acquisition modality. If there is any question as to whether or not a modality has been properly calibrated, or it has not undergone regular quality control tests and maintenance, the images it produces should not be used for diagnostic purposes.
Manually Calibrated Images
Images whose pixel size have been altered from their original values, either from within the software or by some other means, should not be used for diagnosis. The ability to perform manual calibration exists within the software and is discussed in more detail in a later section. This operation, even with the use of fiducials in the image, is subject to human error and the reported values are to be used at the user's own risk.
Values reported by any measurement or Region of Interest (ROI) tools (e.g. Ruler, Ellipse, Rectangle, Polygon) use the pixel size in calculating the reported values, and hence when such tools are used with manually calibrated images, the reported values are to be used at the user's own risk.
Although the software is capable of creating and displaying fused images, the software currently lacks some tools that are necessary for primary diagnosis, such as MIP/MinIP and Standardized Uptake Value measurements.
The software is capable of producing "key images" with burned in measurements and annotations that can be recalled later for review. For the purposes of diagnosis, key images should never be used, but rather the original images from which they were derived should be used. Although key images may contain "burned in" statistics for ROIs, these values are considered informational only, and any diagnosis should be done by performing such measurements on the source images.
Before attempting to use the DICOM Print feature, ensure you read and fully understand the documentation in this guide.
Images are rendered in the same manner as they are for display in the software (8 bit only) and no additional processing is applied before being sent to the printer. Image quality is dependent not only on the ClearCanvas Vetstation software, but also on the physical printer itself and the media on which it prints images. For each printer in use, the proper configuration must be determined, and image quality thoroughly evaluated. Otherwise, printed images should not be used for diagnosis.
The option to print "True Size" is also dependent on the capabilities of the printer, in that it must properly support the "Requested Image Size" DICOM attribute. Before using the "True Size" option in the treatment of patients, a thorough evaluation of accuracy should be performed. Even after evaluation, it is highly recommended that the image scale overlay not be turned off when printing "True Size" images, and the user should verify that the images are indeed true size by measuring the distance between the scale's minor tick marks on the printed film. The distance between minor tick marks is exactly 1cm.
Image Storage and Retrieval
This section discusses parts of the software that have to do with image storage and retrieval. Although these functions should operate as expected under normal conditions, it is possible for errors to occur in transport of images across the network, or on import into the Vetstation's local store. Users should never assume that these operations have completed successfully, but rather they should verify the success of the operation before beginning any form of diagnosis or treatment involving the use of patient imaging studies.
When a patient study is sent to the Vetstation from another DICOM device (e.g. PACS auto-route), the Vetstation is unable to determine whether or not it received all the images, due to limitations in DICOM.
In the situation where a user has manually initiated a retrieval of one or more imaging studies from another DICOM device to the Vetstation, it is important to check the Receive Queue:
|•||For any errors that may have occurred during transfer.|
|•||To make sure no failures have occurred, and that all images have been received and imported into the local store. This is indicated by the "Failed", "Received" and "Available" columns in the Queue, respectively. Again, because of limitations in DICOM, it is difficult for the software to accurately determine whether or not all images have been received successfully in all situations.|
For these reasons, the software never indicates whether or not all images have been received and imported successfully, but rather it provides what information it can to allow the user to make that determination. The user is ultimately responsible for ensuring that all images have been successfully received and imported before using them for treatment or diagnosis.
When importing images into the local store, the user should always check in the Import Activity Monitor to ensure that the import operation is complete and that all the images were imported successfully before using them.
Reindex Local Data Store
The user should never simply assume that the reindex operation has completed successfully, but rather should always check the Reindex Activity Monitor to make sure no failures have occurred. Also, the user is able to continue to use the Vetstation while a reindex is occurring, but it is not advisable to perform any diagnostic activities during this time, as studies that are currently being re-indexed will be incomplete if opened for viewing, and the images will not appear in the viewer as the reindex proceeds. The user must wait for the study to be complete in "My Studies" before opening the study for viewing.
This section discusses specific functions within the viewer portion of the software that may require additional explanation in order to be used safely and effectively. However, it is important for the user to read the entire contents of this manual in order to fully understand the software and its functions.
The display of mammography images is automatically normalized with respect to flips and rotations depending on the laterality and patient orientation of the anatomy imaged regardless of how the pixel data is stored. For lateral views (including MLO and LMO), the standard display is with the head towards the top and the posterior either towards the left (for the left breast) or towards the right (for the right breast). For cranial-caudal views, the standard display is with the patient's arms towards the top, the patient's median towards the bottom, and the posterior either towards the left or right (again, left and right breast, respectively). Additionally, overlay text will be positioned in the corners opposite the posterior so as to avoid occluding anatomy.
Despite these functions, it remains imperative that the standardized and consistent positioning of physical lead markers be used as part of the imaging protocol in order to ensure correct viewing of the images. The ACR requirements are for this marker to be placed near the patient's axilla (armpits), which translates to a position near the tops of the images when displayed according to the previously described normalized views. Extreme discretion should be exercised if there is any discrepancy between this placement and the display of the image and/or the text overlay, as it indicates the presence of errors in the laterality and/or patient orientation information encoded in the image.
Pixel size information stored in the image headers are used by the Vetstation to support features like ROI measurements and true size printing. In cross-sectional modalities (e.g. CT, MR, PT, etc.), these values will correspond to the actual anatomical size. In projection modalities (e.g. CR, DX, MG, etc.), these values value may represent either the physical size of detector elements (i.e. in the plane of the detector), or the anatomical size after some form of correction (either by assuming the anatomy of interest is at a particular depth, or by using fiducials located at the same depth as the anatomy of interest). Therefore, when making measurements on such images, it is imperative that the text overlay be consulted to determine which calibration method, if any, was used by the modality. Discretion should be exercised if the calibration method is unknown.
If the pixel size has not been specified by the modality, this function may be used to manually set the pixel size. Once this is done, the user can then make other measurements within the image and statistics will be reported in physical units (cm) rather than pixels. It is important to note that:
|•||Even within the same series/display set, each image must be calibrated separately. The calibration will not be applied to other images because it is unreasonable for the software to assume that every image in the series has the same pixel size.|
|•||For an image that has been calibrated, the calibration will apply everywhere that image appears, but only within a single viewing session. Calibration is a temporary function, and the underlying DICOM image(s) are not modified in any way.|
Multi-planar Reconstruction (MPR)
MPR images are generated by first constructing a volume and reslicing the volume from different perspectives at a regular interval. By default, this interval is automatically calculated based on the size of voxels in the constructed volume.
If the user has any concerns that the default spacing is too large and that an important part of the anatomy might be missed, the spacing can be adjusted by the user as a multiple of the source image pixel size. This value can be expressed as a fraction less than 1, if desired. The user must close the MPR workspace and re-open it for this change to take effect.
Images are fused by first constructing a volume from the PT series and re-slicing it at the same location within the patient for each CT image on which a PT image is to be overlaid. The software does not perform any kind of image registration in order to fuse images, but rather it relies entirely on the information provided in the image headers with regards to the position and orientation of images in the patient space. Therefore, It is very important to make sure the modality is accurately calibrated.
As discussed here, sometimes PT and CT images will indicate that the images were acquired in different frames of reference, usually because they are actually acquired by different physical devices that have simply been configured to work together. The software will still fuse such images, but there will be a yellow indicator on the text overlay of fused images indicating that the 2 frames of reference don't match. It is up to whomever is responsible for the configuration and maintenance of the acquisition device(s) to ensure they are properly calibrated. Otherwise, fused images will not appear correctly in the Vetstation.
ClearCanvas Vetstation - User's Guide
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