Biomedical subjects

Gregory S Fischer

Publications and source records attributed to Gregory S Fischer.

3 recordsLinked to original sources

PubMed2006

MRI image overlay: applications to arthrography needle insertion.

Magnetic Resonance Imaging (MRI) has unmatched potential for planning, guiding, monitoring and controlling interventions. MR arthrography (MRA) is the imaging gold standard to assess small ligament and fibrocartilage injury in joints. In contemporary practice, MRA consists of two consecutive sessions: 1) an interventional session where a needle is driven to the joint space and gadolinium contrast is injected under fluoroscopy or CT guidance. 2) A diagnostic MRI imaging session to visualize the distribution of contrast inside the joint space and evaluate the condition of the joint. Our approach to MRA is to eliminate the separate radiologically guided needle insertion and contrast injection procedure by performing those tasks on conventional high-field closed MRI scanners. We propose a 2D augmented reality image overlay device to guide needle insertion procedures. This approach makes diagnostic high-field magnets available for interventions without a complex and expensive engineering entourage.

Arthrography↗

PubMed2005

Electromagnetic tracker measurement error simulation and tool design.

Developing electromagnetically (EM) tracked tools can be very time consuming. Tool design traditionally takes many iterations, each of which requires construction of a physical tool and performing lengthy experiments. We propose a simulator that allows tools to be virtually designed and tested before ever being physically built. Both tool rigid body (RB) configurations and reference RB configurations are configured; the reference RB can be located anywhere in the field, and the tool is virtually moved around the reference in user-specified pattern. Sensor measurements of both RBs are artificially distorted according to a previously acquired error field mapping, and the 6-DOF frames of the Tool and Reference are refit to the distorted sensors. It is possible to predict the tool tip registration error for a particular tool and coordinate reference frame (CRF) in a particular scenario before ever even building the tools.

Computer Simulation↗

PubMed2005

Image overlay guidance for needle insertion in CT scanner.

We present an image overlay system to aid needle insertion procedures in computed tomography (CT) scanners. The device consists of a display and a semitransparent mirror that is mounted on the gantry. Looking at the patient through the mirror, the CT image appears to be floating inside the patient with correct size and position, thereby providing the physician with two-dimensional (2-D) "X-ray vision" to guide needle insertions. The physician inserts the needle following the optimal path identified in the CT image rendered on the display and, thus, reflected in the mirror. The system promises to reduce X-ray dose, patient discomfort, and procedure time by significantly reducing faulty insertion attempts. It may also increase needle placement accuracy. We report the design and implementation of the image overlay system followed by the results of phantom and cadaver experiments in several clinical applications.

Biopsy↗