Surgical Robot Restricted Volume via Registration Phantom
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Solution Overview
Problem
Existing methods for defining a prohibited volume for surgical robotic systems are inadequate, especially with X-ray cone beam computed tomography (CBCT) imaging systems, and often require additional steps or materials.
Innovation Solution
A method and system that utilize a registration phantom with radiopaque fiducials to define a restricted access volume for a surgical robotic system, using 2D X-ray images to establish a phantom coordinate system and compute the envelope of the restricted access volume, which includes the region of interest and prohibits the robotic system from entering specific sub-volumes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a camera on robotic arm is used to visually scan patient skin to define prohibited volume, then the prohibited volume can be defined, but additional step and extra material are required
Solution Approach 1:
The system uses the existing X-ray imaging system and registration phantom to automatically define the prohibited volume without requiring additional cameras or manual scanning steps. The registration phantom with radiopaque fiducials serves itself by providing both the coordinate system reference and the boundary definition through its geometric envelope computation.
Solution Approach 2:
The registration phantom serves multiple functions: it provides radiopaque fiducials for localization, defines the patient skin surface geometry, and establishes the coordinate system for the prohibited volume. This eliminates the need for separate components for each of these functions.
2Reliability
If skin surface identification is performed using X-ray CBCT images, then the prohibited volume can be defined, but the grey value variation makes skin surface identification difficult
Solution Approach 1:
The registration phantom acts as an intermediary object that bridges the gap between the X-ray images and the prohibited volume definition. Instead of directly identifying the patient's skin surface from variable grey values, the system uses the phantom's radiopaque fiducials and known geometry to infer the skin surface position and define the prohibited volume envelope.
Solution Approach 2:
The registration phantom uses radiopaque materials that appear as distinct high-contrast regions in X-ray images, creating a clear visual signal that contrasts with the variable grey values of the patient's skin. This allows reliable identification and tracking of the phantom's position and orientation.
3Ease of operation
If tracker is rigidly attached to surgical robotic system instead of surgical tool, then indirect localization is enabled, but safety is compromised due to potential geometric errors and tracking failures
Solution Approach 1:
The system applies preliminary countermeasures by defining a prohibited volume that preemptively prevents the robotic arm from entering dangerous regions. This volume is calculated based on the registration phantom position and includes safety margins, creating a protective barrier before any potential tracking errors or failures can occur.
Solution Approach 2:
The system continuously monitors the registration phantom position through X-ray imaging and updates the prohibited volume definition in real-time. This feedback mechanism ensures that the prohibited volume adapts to any changes in phantom position, maintaining safety even when tracking conditions deteriorate.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enhances the safety of robotically assisted surgical procedures by accurately defining prohibited volumes, ensuring the robotic system operates within safe boundaries, and is applicable with any X-ray imaging system without requiring additional steps or materials.
Implementation Method 1
acquiring at least one 2D X-ray image containing the region of interest and the set of fiducials of the registration phantom
Data Source
Figure 1
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Figure 4A
AI summary
The invention relates to a method for determining a restricted access volume for a surgical robotic system comprising a robotic arm and an end-effector, a registration phantom comprising a set of radiopaque fiducials, the registration phantom being located in proximity to the region of interest, the method comprising the following steps: acquiring at least one 2D X-ray image containing the region of interest and the set of fiducials of the registration phantom by an imaging system; defining a phantom coordinate system attached to the registration phantom using the acquired at least one 2D X-ray image; determining a pose of the phantom coordinate system in a chosen coordinate system; defining the restricted access volume in the chosen coordinate system to include the region of interest, an envelope of said restricted access volume being computed based on the determined pose of the phantom coordinate system in the chosen coordinate system. The invention also relates to a system implementing this method to treat a region of interest of a patient's body.