Simulation
Cardiac Ultrasound
The use of simulators for training in echocardiography is not novel. The
use of simulator for measuring technical (psychomotor) skill in surgery is also
not novel.
The feature that we introduce is using simulation to measure competence
in the technical skill of image acquisition. Current practice is for faculty to
visually gauge trainee competence in ultrasound. The simulator now permits
quantitative and objective measurement of technical skill in acquiring images.
Cognitive skill in making the correct diagnosis from images can also be
evaluated.
Left: The simulator
comprises a mannequin, a mock transducer, and a computer. In this first
version, the transducer position and orientation on the mannequin are tracked
using a magnetic field system.
As a user ŇscansÓ the mannequin, a three-dimensional (3D) ultrasound
data set is cut into a two-dimensional (2D0 ultrasound cine loop at the plane
that corresponds to the position of the transducer on the mannequin. Each 3D
data set was previously recorded from a patient and registered to the
mannequin. The 2D image is displayed on the computer monitor. For training, a
3D reconstruction of the patientŐs heart chambers is also displayed to help
users understand the anatomy they are seeing in their 2D images. The 3D display
also shows where the transducer is scanning in the heart.
Left: Example of 2D
ultrasound image cut from a 3D data set, with inset showing the mannequin, 3D
heart reconstruction, and pointer to the view plane. In the reconstruction, the
left atrium and left ventricle are in red and the right atrium and right
ventricle are in blue. The pointer indicates the position and orientation of
the mock transducer. In this example, the parasternal long axis view that was
acquired (light blue plane) differs from the correct, anatomically defined view
(green plane) by only 0.7 mm in location but the angular error is 29.1ˇ.
The competence assessment measures the positional accuracy of each view
plane in terms of location and angle. The correct view plane is defined using
anatomic landmarks from the 3D reconstructions. For example, the 4-chamber view
is the plane that contains the centroid of the mitral annulus, the centroid of
the tricuspid annulus, and the apex of the left ventricle. Error in location is
measured as distance in the center of the view between the acquired view and
the correct view.
Left: The acquired
image is displayed side by side with the optimal image for each view for visual
comparison.
Image interpretation is performed after the user has finished imaging
the heart, as is the clinical routine. The images are displayed for review, and
questions on findings and diagnoses are presented.
This simulator was developed with funding from:
The Edward J. Stemmler, MD, Medical Education
Research Fund of the National Board of Medical Examiners
and
The Coulter Foundation for Translational Research
Orthopedic Surgery
The objective of this project was to develop a method to measure
procedural competence in an objective and quantitative manner. The procedure
targeted was osteotomy for repair of femoral malunion, a condition in which the
femur failed to heal properly following a fracture and the patient is left with
a deformed and dysfunctional leg.
The training interface presents a clinical case to the user along with antero-posterior (AP) and lateral x-rays of the leg. The
first task is to measure the deformity in terms of the angular deviation from
the contralateral leg, which is assumed to be normal.
Left: User interface for calculating angle of deformity.
The user then performs the osteotomy on a simulated bone by sawing out a
wedge. The plane of the cut is measured from a three-dimensional (3D)
reconstruction of the bone generated by imaging laser lines projected onto the
cut bone while rotating the bone.
Left: Imaging
apparatus. The bone is secured in a vertical position on a rotating stage. The
laser and camera are behind the door.
Left: Surface mesh of cut bone with plane of cut identified at top (gray
plane). The anatomically defined correct cut is also shown (red plane). Error
is measured in terms of the difference between the planes in angle and
position.
All images, text, and captions ©1998 - 2016 University of Washington, except where otherwise noted.