Michael A. Martinelli

Intraluminal ultrasound guidance of transverse laser coronary atherectomy

Catheter systems for laser atherectomy in peripheral and coronary arteries are subject to many design constraints. Ideal mechanical, laser and imaging requirements for these systems are proposed, and compared to the design features of a laser atherectomy system currently under development by Intra-Sonix. This system uses high resolution ultrasound for real-time guidance and control and is potentially capable of characterizing lesions and imaging critical structures in the coronary arteries, to guide physicians in the application of laser therapy. Precise catheter location and rotational direction can be provided continuously as the therapeutic intervention proceeds. Examples are given of the imaging modes and ultrasound images of an artery produced by the Intra-Sonix system.

Ultrasound guidance of laser atherectomy

Intravascular ultrasound imaging catheters and forward firing laser atherectomy systems are both being used in the coronary vascular tree of man. When used in conjunction, ultrasound imaging may reduce the probability of perforation and dissection related to laser atherectomy. A novel system is presented which combines ultrasound imaging and laser atherectomy capabilities on the same catheter. The system incorporates a holmium YAG laser directed perpendicular to the long axis of the catheter along with a co-directional ultrasound sensor. Ultrasound images are assembled by computer using the angle of the catheter tip and its linear advance associated with each ultrasound echo signal.In vivo experimental results are presented.

Reduction of acoustic transients generated in liquid media and in tissue by pulsed 2-um lasers

We are testing the acoustic response of Ho:Tm:YAG and Tm:YAG laser pulses absorption in water and in tissue using a broadband ultrasound PVDF transducer. A clear acoustic signature of the cavity formation as well as its collapse is obtained. The cavity collapse echo carries higher amplitudes and can be eliminated or reduced in tissue by direct fiber-tissue contact. The laser pulse temporal profile--smooth or spiky--has a rather small acoustic impact. Smoother pulses generate somewhat lower acoustic amplitudes during the cavity formation phase.

Intraluminal laser atherectomy with ultrasound and electromagnetic guidance

The MagellanTM coronary laser atherectomy system is described. It uses high- resolution ultrasound imaging and electromagnetic sensing to provide real-time guidance and control of laser therapy in the coronary arteries. The system consists of a flexible catheter, an electromagnetic navigation antenna, a sensor signal processor and a computer for image processing and display. The small, flexible catheter combines an ultrasound transducer and laser delivery optics, aimed at the artery wall, and an electromagnetic receiving sensor. An extra-corporeal electromagnetic transmit antenna, in combination with catheter sensors, locates the position of the ultrasound and laser beams in the artery. Navigation and ultrasound data are processed electronically to produce real-time, transverse, and axial cross-section images of the artery wall at selected locations. By exploiting the ability of ultrasound to image beneath the surface of artery walls, it is possible to identify candidate treatment sites and perform safe radial laser debulking of atherosclerotic plaque with reduced danger of perforation. The utility of the system in plaque identification and ablation is demonstrated with imaging and experimental results.

Ultrasonic Imaging Of Coronary Arterial Thickness & Ultrasonic Signature Typing Of Internal Abnormalities

This paper describes experimental results of tests performed on cadaver arteries using a pulsed ultrasonic imaging transducer. Computer generated three-dimensional hidden line images based on pulsed data show the artery thickness both in normal areas and in areas with complex plaque. Thin fatty deposits on the interior artery wall are also imaged. A series of ultrasonic echo images were taken on human aorta plaque deposits and the corresponding set of histological sections prepared. A side-by-side presentation is made in which specific plaque features and internal structures are identified ultrasonically and verified on the histological section. The performance of the ultrasonic transducer is consistent with an ability to perform ultrasonic signature arterial tissue typing. The transducer is sized to allow mounting within a 0.8 mm catheter that is equipped with a guide wire and a laser delivery system.

Ultrasonic Imaging Suitable For Coronary Arteries Featuring Depth Profile Of Abnormalities

Ultrasonic images of cadaver arteries are presented in this paper. The images were produced from within the arteries by a pulsed transducer capable of being mounted on a 0.8 mm catheter equipped with both a guide wire and a laser delivery system. The image data were acquired, processed, and displayed by a computer based real-time system. Example images show some of the display formats which are available for elucidating the internal structure of arteries with this imaging modality. Transverse and radial sections of the artery are shown in both A-Scan and B-Scan modes. Derived thickness images are also presented. In each mode the internal artery structure, including plaque areas, is clearly apparent. Histologic sections are shown beside ultrasonic data to verify the utility of these images.