Step 1 – Patient Imaging
The patient tracking system is prepared by attaching 6 sterile retro-reflective marker spheres onto the patient’s abdomen. The region of interest of the patient (i.e. the abdomen) is imaged in the desired resolution using the imaging system (i.e. CT, MRI or the like). The image data is transferred from the hospital PACS system to the CAS-One IR system (network-based DICOM transfer). The image data is loaded into the CAS-One IR system using software based DICOM import dialog. Visualization of the available image data and adjustment of the visualization parameters of the CAS-One IR system, such as magnification, contrast, brightness etc.
Step 2 – Needle placement planning
Planning of needle positions is based on a 2D image data visualization module where multiple needle insertion trajectories can be planned. Image data is imported from the available imaging system and displayed on the navigation screen. Through a touch-screen interface the user defines the needle trajectory by selecting a target (e.g. tumour) and an additional needle entrance position at the surface of the patient body, as visible on the available CT images.
Step 3 – Marker-based patient registration and motion tracking
Markers are delineated in the image data through a semi-automatic procedure. The position measurement system provides real-time measurement of marker positions on the patient. Patient motion is detected by comparing the marker positions between position measurements. By displaying similarity to the initial configuration during respiratory motion, the optimal time point for needle insertion can be determined by the user.
Step 4 – Visualization of patient motion and respiration
In the bottom of the navigation screen, an indicator of the patient deformation as calculated from the marker positions on the patients abdomen is displayed as a temporal signal. This value corresponds to the deviation from the initial scenario and enables the selection of a suitable time point for needle insertion (respiratory gating).
Step 5 – Guidance for needle placement and insertion
In a first step, the user is guided towards the desired entry point on a 3D viewer. Once the needle tip is positioned close the entry point, the targeting viewer is enabled and provides guidance for fine alignment of the needle. The alignment of the needle tip to the center of the targeting area provides feedback that the needle tip is placed on the planned entry location. In a second step, the needle axis is then adjusted until the green circle is aligned with the center of the targeting region. The required needle insertion depth is displayed in the green arrow on the right of targeting area.