How are CPRs Created?
Creating a CPR typically begins with automated tools that can quickly generate a basic reformat of a vessel. This process starts by selecting a seed point, which acts as the reference from which the software maps the vessel or structure. Proper placement of the seed point is important; it should be located within the lumen or along the structure’s main axis to guide the software accurately. Strategic seed point placement, especially in complex regions, can help prevent errors in the automation like jumping across vessels or cutting corners.
Manual adjustments are often necessary to enhance the precision of CPRs. By placing seed points at critical junctions and adjusting anchor points, users can correct any inaccuracies, ensuring the CPR accurately represents the vessel’s path. This combination of automation and manual editing is typical for producing accurate CPRs in a timely manner.
Figure A: An automated tool demonstrating how quickly CPRs can be created of vessels in the brain.
Example 1: Right Carotid Artery
Figure B: Selecting a seed point along the right carotid artery to generate an automated CPR.
Figure C: Manual adjustment of CPR anchor points to correct any inaccuracies from the automated tool.
The video clips above show the automated creation of a CPR for the right carotid artery. This vessel is often easier to work with because it typically follows a predictable anatomical path and is well-defined in imaging. To assist with accurate CPR creation for the right carotid artery, follow these steps:
- Seed point placement: Strategically place a seed point at a sharp corner to guide the software along the correct path and prevent cutting corners.
- Verify the path: After the CPR is generated, carefully inspect the path for any discrepancies.
- Adjust for curves: Pay close attention to curves and corners, ensuring they accurately represent the vessel’s anatomy. Use anchor points to correct any areas where the CPR is not centered within the vessel.
Example 2: Vertebral Arteries
Figure D: Selecting a seed point for automated creation of a vertebral artery CPR.
Figure E: Adjusting the anchor points in some of the more tortuous regions of the basilar artery.
The vertebral arteries pose a challenge for automated CPR creation due to the high signal interference from surrounding bone and vein structures. Automation might struggle to find the correct path, requiring manual intervention. Below are some steps that may assist with ensuring accuracy of a vertebral artery CPR:
- Seed point placement: Strategically place a seed point at a sharp corner to guide the software along the correct path and prevent cutting corners.
- Verify the path: After the CPR is generated, carefully inspect the path for any discrepancies.
- Manual techniques: Manual addition and manipulation of anchor points will be vital to guide the tool through the complex curves of the vertebral arteries.
- Distortion and mirror artifacts: Be aware of distortions and mirroring, as CPRs can sometimes present misleading visuals. Correct any abnormalities to ensure accuracy.
Advanced Techniques
Creating custom-path CPRs can be effective for creating unique anatomical views that standard, center-aligned CPRs might miss. These manually-defined CPRs allow clinicians to gain different perspectives, such as side views of vessels branching from the aorta, which can be important in complex cases. CPRs can be used to better visualize structures like bone, providing a clearer understanding of the relationships between various anatomical features and aiding in more accurate diagnoses and treatment planning.
Advanced CPR Example: Mandible
CPRs are not limited to vascular structures and can also be effectively applied to bony structures like the mandible. This is achieved by manually creating a CPR, where anchor points are placed along the curvature of the mandible in an axial view. This technique visualizes the entire length of the mandible in one image, which i can help reveal subtle fractures or anomalies that might be missed in traditional cross-sectional imaging.
Figure F (Right): Manual creation of a CPR by placing anchor points along the curvature of the mandible.
Advanced CPR Example: Aortic Arch
The vessels of the aortic arch are not aligned on a single plane, which makes them challenging to visualize in traditional 2D imaging. The aortic arch follows a curved path as it loops from the heart, and its branching vessels—such as the brachiocephalic artery, left common carotid, and left subclavian—extend at different angles. Standard views (axial, coronal, or sagittal) often slice through these vessels, providing only partial information. A custom-defined CPR creates a single view showing all of these vessels and their relationships, aligning them in a single, continuous plane for an uninterrupted view.
Figure G (Right): Manual creation of a CPR by placing anchor points along the aortic arch.
