Device and method for a trackable ultrasound
Inventors
Glossop, Neil David • Wood, Bradford Johns
Assignees
Philips Electronics Ltd Canada • Koninklijke Philips NV • US Department of Health and Human Services
Publication Number
US-9398892-B2
Publication Date
2016-07-26
Expiration Date
2026-06-21
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Abstract
The invention provides a method for adjusting the calibration of a tracked ultrasound device using the measured difference between two sets of fiducial markings in two relative positions of a tracker and an scan head of the device. The invention also provides a trackable ultrasound device that enables repeatable attachment of a tracker to a scan head, thus preserving an initial calibration between the tracker and the scan head. Furthermore, the invention provides a calibration jig that can be used to repeatably attach a tracker to an ultrasound scan head or to measure the difference between two relative positions of a tracker and a scan head.
Core Innovation
The invention provides a trackable ultrasound device and associated methods that enable repeatable attachment of a tracker to the scan head of the device, preserving an initial calibration between the tracker and the ultrasonic transducer. The device includes features such as machined grooves, keyways, divots, alignment pins, or spring-loaded balls, which allow repeatable and accurate alignment of the tracker with the scan head. This prevents the need for recalibration if the tracker is removed and replaced or moved relative to the scan head.
The invention also provides a method for adjusting the initial calibration of the tracked ultrasound device when relative movement occurs between the tracker and the ultrasonic transducer. This adjustment is accomplished by measuring the difference between two sets of fiducial markings—tracker fiducials and scan head fiducials—sampled in two different relative positions, calculating a differential transformation matrix, and applying this to the initial calibration transformation matrix. This avoids time-consuming recalibration, enabling the device to maintain accurate tracking of the scan plane's position and orientation despite repositioning of the tracker.
Claims Coverage
The claims disclose inventive features covering methods for calibration adjustment, details of sensor elements and fiducials, use of calibration jigs, and methods for repeatable tracker replacement on an ultrasound device.
Method of adjusting calibration using fiducial differences
A method of adjusting calibration of a tracked ultrasound device by attaching a tracker to a scan head, calculating an initial calibration transformation matrix relating sensor elements to the scan plane, determining first and second relative positions of tracker fiducials to scan head fiducials in two tracker positions, calculating their difference, and adjusting the initial calibration based on this difference.
Use of electromagnetic or other sensor elements for position determination
The tracker includes one or more electromagnetic sensor elements, or other types such as inertial guidance, ultrasonic, optical, or fiber optic sensors, with corresponding determination of their position and orientation relative to a tracking device.
Sampling fiducial positions using tracked probes or imaging modalities
Determining fiducial relative positions by sampling their positions in the same frame of reference, using tracked probes to touch fiducials or imaging modalities to image the fiducials, or measuring sensor elements known relative to the fiducials.
Calibration using a calibration jig with fiducial markings
Using a calibration jig with calibration fiducials and alignment elements engaging with the tracker and scan head fiducials, allowing determination of relative positions in the first and second tracker positions, with scan head to jig relative position fixed.
Calculating transformation matrices and differential transformation matrix
Calculating primary and secondary transformation matrices relating tracker fiducials to scan head fiducials in first and second tracker positions respectively, and computing a differential transformation matrix representing the difference between these positions, used to adjust calibration.
Method for repeatable tracker replacement using alignment elements and calibration jigs
A method for removing and re-attaching a tracker to an ultrasound scan head such that alignment elements on tracker and scan head correspond, using a calibration jig with calibration alignment elements to return the tracker to the original position, preserving the calibration.
The claims collectively cover the method of adjusting calibration using fiducial differences and transformation matrices, use of various sensor elements for tracking, sampling of fiducials by tracked probes or imaging, employment of calibration jigs, and methods enabling repeatable tracker replacement preserving calibration, thereby maintaining accurate tracking without full recalibration.
Stated Advantages
Enables repeatable and accurate alignment of the tracker with the ultrasound scan head, preserving initial calibration to avoid time-consuming recalibration.
Allows adjustment of initial calibration after relative movement of tracker and ultrasonic transducer, reducing the need for difficult re-calibration procedures.
Minimizes errors caused by lever effects in tracking by placing sensor elements close to the ultrasonic transducer.
Facilitates merging of preoperative images with intraoperative ultrasound data accurately.
Documented Applications
Producing merged images of preoperative scans such as CT, PET, or MR images with intraoperative ultrasound images for image-guided interventions.
Tracking the scan plane of an ultrasonic transducer within a patient's body during surgical procedures.
Performing internal endocavitary calibration using calibration jigs insertable through laparoscopic ports.
Using multiple tracked ultrasound transducers simultaneously for treatment and diagnostic monitoring, including ablative treatment or assisted drug delivery.
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