The purpose of this manuscript is to provide the reader an overview of the currently available technology and some of the preliminary clinical results of the various devices and procedures within the field of endovascular surgery, i.e. vascular endoscopy, intraoperative balloon angioplasty, laser angioplasty, atherectomy, and stents. It is beyond the scope of this manuscript to cover all the developmental and research studies. For an idepth coverage of these topics, the reader is referred to the textbook, Endovascular Surgery.

Endoscopic holography or endoholography combines the features of endoscopy and holography. The purpose of endoholographic imaging is to provide the physician with a unique means of extending diagnosis by providing a life-like record of tissue. Endoholographic recording will provide means for microscopic examination of tissue and in some cases may obviate the need to excise specimens for biopsy. In this method holograms which have the unique properties of three-dimensionality large focal depth and high resolution are made with a newly designed endoscope. The endoscope uses a single-mode optical fiber for illumination and single-beam reflection holograms are recorded in close contact with the tissue at the distal end of the endoscope. The holograms are viewed under a microscope. By using the proper combinations of dyes for staining specific tissue types with various wavelengths of laser illumination increased contrast on the cellular level can be obtained. Using dyes such as rose bengal in combination with the 514. 5 nm line of an argon ion laser and trypan blue or methylene blue with the 647. 1 nm line of a krypton ion laser holograms of the stained colon of a dog showed the architecture of the colon''s columnar epithelial cells. It is hoped through chronological study using this method in-vivo an increased understanding of the etiology and pathology of diseases such as Crohn''s diseases colitis proctitis and several different forms of cancer will help to their control. 1.

The field of photodynamic therapy or' PDT" has been the subject of a number of recent comprehensive review articles and books (for example the 1 989 publication by CRC press17). Thus in spite of my title I will give a review which is in no way comprehensive but which deals in some depth with the dosimetry of PDT.

As more advanced therapeutic procedures are performed on coronary arteries during open chest surgery more advanced diagnostic procedures will be required to define the location and severity of coronary artery disease. This manuscript describes our preliminary experiences in identifying human coronary artery stenoses using epicardial two-dimensional color flow Doppler. Once the lesions were identified we used standard echo Doppler and imaging techniques to define their severity. The accuracy of stenotic cross sectional area calculated using the continuity equation and pressure gradient calculated using the Bernoulli equation were defined using a pulsatile flow model of the coronary circulation. Suggestions about further hardware development required to allow easy clinical application of this technique are described. 1 - CLINICAL NEED FOR INTRA-OPERATIVE EVAUJATION OFCORONARY ARTERIES The severity of coronary artery disease in adults who require coronary bypass surgery has changed significantly in the last ten years. More effective medications used to control angina pectoris and the wide use of percutaneous y artery angioplasty have delayed the timing of surgery until atherosclerotic involvement is more extensive. In addition patients who have had initial coronary bypass operations are now reaching ages at which atherosclerotic involvement of their bypass grafts and native vessels has progressed and reoperation is required. To meet the challenge of coronary arteries with multiple lesions or diffuse disease intraoperative angioplasty devices are being developed. Whether bypass surgery for advanced lesions or reoperation of

Over the past 3 years we have developed a percutaneous ultrasonic angioplasty device and recently applied it in human peripheral arteries. This paper describes some of the background preceding the development of intravascular ultrasound for arterial recanalization. The chronology of our development of ultrasonic angioplasty is discussed from in vitro studies on atherosclerotic plaque to in vivo studies in canine models with differing types of arterial occlusions (thrombotic fibrotic calcific-atherosclerotic) and to initial human application. SPIE Vol. 1321 Modern Technologies Applied to Medical Practice (1989) / 69

Experimental results for the optical properties of ocular tumors in the red to near infrared region from 600-900 nm and at the near infrared wavelength of 1064 nm are presented. The tumor models have been human retinoblastoma heterotransplanted in athyinic mice and B16 melanotic melanoma in athymic mice. The steady state retinal and tumor temperature rise during 1064 nm laser irradiation have been examined in vivo in normal albino and pigmented rabbits eye and in Greene''s melanoma inoculated in the retinachoroidal layers. 2.

Optical sensors are a new type of device that employ the ability of optical fibers, also known as fiber optics, to transmit light very efficiently over long distances. The operating principles behind these sensors and their applications are the subject of the initial sections of this paper. We will first consider the properties of optical fibers and then move to a discussion of how these fibers can be c0nverted into sensors. A more practical discussion of medical applications for continuous clinical monitoring will follow along with a discussion of the issues that are of particular concern for medical applications.

Multidimensional tomographic image processing can be used to provide the surgeon useful information on volume, size, shape, location and anatomical relationships of intracranial lesions. Using a reference system this information can be used to "simulate" and interactively optimize different treatment modalities such as surgery, radiation therapy, photodynamic therapy, hyperthermia, etc. Finally, this computer generated data can be transposed accurately on the "real" physical world or can be used to drive instruments such as microscopes, lasers, etc., leading to automation of neurosurgical procedures. Computer reconstruction of image data (CT, MRI, DA) acquired under stereotactic conditions allows three—dimensional and multiplanar representation of a target volume and surrounding anatomy. Target vOlume definition is the common step of any "volume"—dependent procedure, including diagnostic histological mapping, resection or internal decompression of lesions, radiation, hyperthermia, photodynamic therapy, etc. (6, 8, 13, 19, 28,31, 34, 36). An image—based surgical treatment planning system has been developed to provide an interactive "real time" three-dimensional and multiplanar stereotactic neurosurgical planning that allows target volume definition, rotation, reconstruction in arbitrary planes, selection of surgical trajectory and optimization of surgical approach (36, 37). Real time computation allows surgical target and trajectories to be selected, displayed, and optimized in 3D and 2D multiplanar views; at the same time this preplanning can be "mathematically" transposed into intraoperative stereotactic space, and therapy can be directed to this volumetric information. Diagnostic and therapeutic stereotactic procedures can be accomplished accurately using these image-generated data to guide endoscopes, microscopes, lasers or other surgical instruments. Image-based stereotactic preplanning is the first step in automated surgical procedures (36, 37); these computerized data can also he used to deliver highly focused energy from specific components of the electromagnetic spectrum (gamma radiation, visible light, microwaves, etc.) or derived from heavily charged particles (protons, etc.). The common factor in these procedures is accurate target volume definition and space localization. This short-course notes describe our current hardware and software configuration currently used in our institution to support image "guided" or "directed" neurosurgical stereotactic procedures. The final goal is optimization of neurosurgical procedures for intracranial lesions. Performance of image-guided stereotactic neurosurgical procedures can be divided into four successive steps: 1. Stereotactic Image Data Acquisition 2. Computerized Pornographic Image Processing for Planning 3. Transposition of "Simulated" Planning into Physical World 4. Diagnostic or Therapeutic Neurosurgical Procedure