* Cardiovascular Imaging Laboratory *
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Physician Photo
Nikolaos Tsekos, Ph.D.
Assistant Professor of Radiology and Biomedical Engineering
Office: East Building 1308
Tel: 314.747.3873
Fax: 314.747.3882
tsekosn@mir.wustl.edu
 
Dept of Radiology
Washington University
Campus Box 8225
510 S. Kinshighway Blvd
St. Louis, MO 63130

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Research: Vascular Intervention MRI
The main research directive of our group is the development of methodology to perform MRI-guided vascular interventions and currently our effort is focused on the development and optimization of MRI-guided coronary interventions. This effort is supported by the National Heart, Lung and Blood Institute (NHLBI) grant R01HL067924 (Abstract of the Grant).

At this stage we are working on two aspects of the project:

  1. The development of an MRI protocol to perform real time imaging of the coronary vessels. Our challenge is to overcome the low inherent sensitivity of the nuclear magnetic resonance modality. To address this issue we are developing a new MR pulse sequence and we combine it with intravascular infusion of Gd-based contrast agent (manuscript on fast coronary imaging with intracoronary administration of Gd (pdf)). This sequence is based on the acquisition of a limited portion of the k-space that is suitable for imaging of the targeted anatomy.

  2. The implementation and validation of a family of catheters that are suitable for concurrent and/or selective visualization of the coronary tree and the interventional instrumentation.

Below are representative coronary MRA images collected during intracoronary infusion of Gd. The contrast agent was infused via catheter that was inserted into the Left Anterior Descending or the Left Circumflex coronary arteries of a canine. These studies were performed on a Sonata Siemens scanner.

Four slices, out of six, from a dynamic cMRA (1SegmSR; 130ms/ image; 1.4x2.8 mm2; triggered multislice) during IC infusion Gd in the left main. These multislice frames were selected from a time series of 180 frames collected with the dynamic sequence (LAD: left anterior descending, LCx= left circumflex, OM= obtuse marginals).

Four time-frames from a dynamic cMRA (178 ms/image;TI=70ms; 0.89x0.98 mm2; non-triggered) during intracoronary infusion of Gd in the LCx of a dog heart. The bifurcation to a branch can be observed (red arrow).

A time-frame from a dynamic 2D cMRA (210 ms/image; TI=70ms; SL = 30 mm; 1.5x1.5 mm2; non-triggered), immediately after injection of Gd. Partition from 3D images of the LCx from (A) contrast enhanced cMRA (0.9x0.8x1.5 mm 3; Slab = 20mm) and (B) scout (no Gd) 3D cMRA. The slab (A) and the partitions (B, C) are at approximately the same spatial position. The 2D, which collects a thicker slab than the 3D, depicts a longer portion of the LCx (white arrow).

Research: MRI Robotics
The goal of this project is to develop a versatile remotely controlled manipulator for performing interventions inside cylindrical MR scanners with real-time MR guidance. Primary reasons for pursuing such devices are the need to reach the patient inside the confined space of a cylindrical MR scanner for real-time guidance, as well as the improved accuracy and steadiness in positioning and holding diagnostic or therapeutic interventional tools. Integration of manipulators with real-time MR imaging is also advocated as a new paradigm of performing diagnostic imaging, biopsies and/or minimally invasive therapeutic procedures during the same session.

"Design of a Robotic Stereotactic Device for Biopsy and Minimally Invasive Interventions in the Breast with Real Time MRI Guidance"
2002 Best Paper Award of the American Society of Mechanical Engineers Committee



MR images collected at 4 Tesla showing the compression of the breast phantom with the robotic device. The yellow circles indicate the position of the MR-visible markers. No signal is detected from the device and the compression plates are depicted with an open red box (stationary) and a solid red box (movable). The yellow arrow points to a lesion that appears in the depicted slice at a higher degree of compression, because compression changes the shape and the position of structures inside the breast.

MR images collected at 4 Tesla showing the insertion of a needle into the breast phantom with the robotic device. The distal portion of the needle (red arrow) was filled with MR contrast agent. The red circle indicates the targeted lesion.

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