Image-to-World Registration Using World Spatial Map

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Solution Overview

Problem

Current image-guided medical procedures face challenges with traditional 'outside-in' registration methods, which are invasive, disrupt workflow, and provide limited depth information, requiring surgeons to mentally visualize and inaccurately position anatomical structures using fluoroscopic images.

Innovation Solution

An 'inside-out' image-to-world registration system using a world spatial map and optical see-through head-mounted displays (HMDs) for medical augmented reality, allowing for precise linking of image frames to the surgical environment, enabling visualization of three-dimensional anatomical structures from two-dimensional fluoroscopic images.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional outside-in registration methods are used, then image guidance is achieved, but the procedure becomes invasive and workflow is disrupted

Engineering Contradiction:

Improveimage guidance accuracyVSAvoidworkflow continuity

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The patent inverts the traditional registration approach by switching from outside-in (tracking patient/tools) to inside-out (tracking imaging system relative to world). The C-arm fluoroscope becomes the tracked object with a rigidly attached tracker, and images are registered to a pre-acquired world spatial map rather than tracking patient anatomy directly. This inversion eliminates the need for invasive fiducials and continuous optical tracking of surgical tools.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The system performs preliminary acquisition of a world spatial map using the C-arm fluoroscope before the surgical procedure begins. This pre-acquired map serves as the reference framework for all subsequent image registrations, eliminating the need for continuous tracking and registration adjustments during surgery. The tracker is rigidly attached to the C-arm in advance, establishing the coordinate transformation relationships beforehand.

Inventive Principle:

Principle #10Preliminary action

2Loss of information

If fluoroscopic images are used alone, then radiation exposure is minimized, but depth information and spatial localization are insufficient

Engineering Contradiction:

Improvespatial depth informationVSAvoidradiation exposure

Core Design Contradiction:

Loss of informationVSObject-affected harmful factors

Solution Approach 1:

The patent merges 2D fluoroscopic images with 3D world spatial map data in an augmented reality display. The HMD overlays registered 3D anatomical structures and imaging information onto the surgeon's view of the actual surgical field, combining the advantages of both 2D imaging and 3D spatial understanding without requiring additional radiation-exposing scans.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The world spatial map acts as an intermediary that bridges the gap between 2D fluoroscopic images and 3D surgical reality. By registering images to this pre-acquired 3D map rather than directly tracking patient anatomy, the system provides depth information and spatial context without requiring additional ionizing radiation exposure during the procedure.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Speed

If optical registration methods are used, then real-time tracking is achieved, but line of sight is blocked and setup complexity increases

Engineering Contradiction:

Improvetracking response timeVSAvoidregistration system setup

Core Design Contradiction:

SpeedVSDevice complexity

Solution Approach 1:

The patent extracts the tracking function from the surgical field and places it on the C-arm fluoroscope itself. A tracker is rigidly attached to the C-arm, and the world spatial map is acquired from the C-arm's perspective. This removes optical trackers from the surgical field, eliminating line-of-sight blockage issues and reducing setup complexity while maintaining real-time tracking capability through the registered image stream.

Inventive Principle:

Principle #2Taking out (Extraction)

4Measurement precision

If multiple fluoroscopic planes are acquired to determine depth, then spatial position is localized, but radiation exposure increases and time is consumed

Engineering Contradiction:

Improvespatial position accuracyVSAvoidprocedure time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The system performs preliminary acquisition of the world spatial map and establishes all coordinate transformation relationships before the surgical procedure begins. This pre-computation of the 3D reference framework eliminates the need for multiple intraoperative fluoroscopic acquisitions for spatial localization, providing immediate depth information through the registered AR display without additional radiation exposure or time loss.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS20200275988A1Image to world registration for medical augmented reality applications using a world spatial map

Publication Date: 2020.09.03 JOHNS HOPKINS UNIVERSITY

AI summary

The present invention is directed to a system and method for image to world registration for medical reality applications, using a world spatial map. This invention is a system and method to link any point in a fluoroscopic image to its corresponding position in the visual world using spatial mapping with a head mounted display (HMD) (world tracking). On a projectional fluoroscopic 2D image, any point on the image can be thought of as representing a line that is perpendicular to the plane of the image that intersects that point. The point itself could lie at any position in space along this line, located between the X-Ray source and the detector. With the aid of the HMD, a virtual line is displayed in the visual field of the user.