Laurence A. Spero

Ejection load changes in aortic stenosis. Observations made after balloon aortic valvuloplasty.

To investigate complementarity and competitiveness between the intrinsic and extrinsic components of the total left ventricular systolic load, hemodynamic data from 18 elderly subjects with severe aortic stenosis were analyzed before and after balloon dilation of the stenosed aortic valve. Multisensor micromanometric pressure measurements allowed calculation (simplified Bernoulli equation) of the ejection velocity and aortic input impedance spectra. Despite a 32% increase in the aortic valve area (from 0.56 +/- 0.04 to 0.74 +/- 0.05 cm2 [mean +/- SEM], p < 0.01), the peak left ventricular systolic pressure fell by only 12% (from 189 +/- 10 to 167 +/- 8 mm Hg, p < 0.01). This was accompanied by an increase in the impedance at the same cardiac output. In a subset of patients (n = 9) in whom the peak aortic systolic pressure rose after valvuloplasty (from 115 +/- 10 to 128 +/- 12 mm Hg, p < 0.01), a 40% increase in the aortic valve area was accompanied by a marked increase in the aortic input impedance. In this subset, the steady component of the aortic input impedance increased by 24% (from 960 +/- 96 to 1,188 +/- 134 dyne.sec/ml, p < 0.05), and the characteristic impedance increased by 25% (from 106 +/- 13 to 132 +/- 19 dyne.sec/ml, p < 0.05). Because of an increased aortic impedance acutely following the procedure, the total left ventricular systolic load after balloon dilation of the stenotic valve was only slightly decreased despite a significant increase in aortic valve area. This represents an example of complementarity and competitiveness between the intrinsic and extrinsic components of the total systolic ventricular load. It may explain why improvement in left ventricular performance may be modest acutely following balloon aortic valvuloplasty.

Which media are most likely to solve the archival problem

The clinical application of quantitative methods for coronary arteriography remains limited, due in large part to the absence of a suitable replacement for cinefilm as the procedure record. The extension to the clinical environment of the validated objective methods which have found such widespread acceptance in clinical research studies is difficult to implement if the time-consuming and variable process for digitization of selected cinefilm frames is required. In addition, the complete integration of the angiographic procedure record with other patient records and procedures stored in a digital data format requires that the angiographic data eventually be converted to a digital format as well. Replacement of cinefilm requires that the media chosen for the task provide at least the same capabilities and preferably improved functions as those provided by cinefilm as a display, transport, and archival media. The demanding set of requirements imposed on the replacement options include high capacity, high acquisition rate, high transfer rate, application in a distributed environment, portability between institutions, and low expense. A true digital solution should also provide immediate access to the results of the angiographic procedure, transfer of image data over digital networks, multiple-user viewing capability, and quantitative analysis on a routine basis for all patients. In fact, a single media may not provide all the capabilities listed above but, rather, different media may need to be used for specialized tasks, i.e. the solution for archival may not be the same that will be employed as the portable patient record. Separation of the archival function from the acquisition/display and portable transfer functions increases the likelihood that cinefilm can be replaced in the imminent future by reducing the demands on a single media. Among the archival options available today are: (1) magnetic disks; (2) analog laser optical disks; (3) digital laser optical disks; (4) digital file-based magnetic tape; (5) digital video magnetic tape. In evaluating each of these alternatives, an accounting is required of how each meets the archival requirements along with an approximate breakdown of cost and readiness for implementation as a clinical solution today.

Multiuser environment for the display and processing of digital cardiac angiographic images

The increased application of digital imaging techniques to diagnostic cardiology requires the resolution of several remaining problems involving the transmis sion display and storage of clinical image data. A Digital Imaging Laboratory is being assembled for the purpose of addressing these problems on a routine clinical basis in a high volume environment. The laboratory consists of independent workstations connected over a local area network which can be accessed by different users for display analysis and storage of diagnostic image data. In addition the laboratory is connected to a hospital-wide network providing communication with other clinical laboratories and other digital imaging modalities.© (1990) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Application of quantitative coronary angiography in a cineless environment: In vivo assessment of a fully automated system for clinical use☆

The accuracy and precision of a fully automated quantitative coronary angiography (QCA) algorithm for use in a cineless environment were determined in phantom studies and in an in vivo canine preparation. Imaging studies of 118 coronary segments in six anesthetized dogs were compared with measurements of the diameters of casts of the canine coronary arteries produced in physiologic conditions. Regression analysis of phantom vessel diameters against QCA measurements revealed slopes of 0.94 to 0.96 and r values > 0.99. The results of the in vivo studies showed good correlation with the coronary cast diameter measurements, with a slope of 0.969 and an r value of 0.987 for the sets of measurements. The high degree of accuracy obtained in a model representative of the clinical situation demonstrates that QCA methods can be applied reliably in the clinical arena with current digital imaging technology and without cinefilm.

A multiuser networked system for the large scale study of coronary artery restenosis using quantitative and qualitative coronary angiography

A multi-user system capable of assessing the changes induced from interventional procedures such as coronary angioplasty (PTCA) is assembled using quantitative coronary angiography coupled with the visual assessment of twenty morphological descriptors as input to a relational database, for a large epidemiology study or for use on a routine basis in a high volume clinical environment. Pre- and post-PTCA studies along with six-month follow-up studies from an initial 600 patients have been processed by this system in the initial three months of use. With the creation of the multi-user digital imaging system, quantitative coronary angiography, coupled with a library of defined qualitative lesion descriptors, can be performed rapidly on a large number of patients. Carefully performed analyses of existing patient databases and the acquisition of lesion morphology data coupled with quantitative coronary angiography will provide useful information in determining the efficacy of interventional and pharmacologic procedures in coronary artery disease. This system is suited to define detailed lesion descriptors that impact on either the progression or regression of coronary artery disease over time.<<ETX>>

Design and clinical evaluation of a high-capacity digital image archival library and high-speed network for the replacement of cinefilm in the cardiac angiography environment

An economical and practical digital solution for the replacement of 35 mm cine film as the archive media in the cardiac x-ray imaging environment has remained lacking to date due to the demanding requirements of high capacity, high acquisition rate, high transfer rate, and a need for application in a distributed environment. A clinical digital image library and network based on the D2 digital video format has been installed in the Duke University Cardiac Catheterization Laboratory. The system architecture includes a central image library with digital video recorders and robotic tape retrieval, three acquisition stations, and remote review stations connected via a serial image network. The library has a capacity for over 20,000 Gigabytes of uncompressed image data, equivalent to records for approximately 20,000 patients. Image acquisition in the clinical laboratories is via a real-time digital interface between the digital angiography system and a local digital recorder. Images are transferred to the library over the serial network at a rate of 14.3 Mbytes/sec and permanently stored for later review. The image library and network are currently undergoing a clinical comparison with cine film for visual and quantitative assessment of coronary artery disease. At the conclusion of the evaluation, the configuration will be expanded to include four additional catheterization laboratories and remote review stations throughout the hospital.

Maximum a posteriori optimization-a method for calculation of dynamic changes in ventricular contours from angiographic image sequences

A robust and accurate method for automatic determination of dynamic left ventricular function has been developed for application to sequences of angiographic images. The method employs a maximum a posteriori optimization approach. The shape of the ventricle boundary is modeled by an elliptical Fourier series. The intensity cross section of the ventricle boundary is modeled using a derivative of a Gaussian. Prior knowledge of the probability of a given ventricle shape and temporal behavior is encoded using a distribution on the parameters. This prior knowledge is coupled with the spatial and temporal information in the image sequence using a guided gradient descent technique to estimate the dynamic contour coefficients. The results illustrate the performance of the optimization algorithm on two examples of digital subtraction X-ray ventriculograms.<<ETX>>

An image processing algorithm for the determination of changes in coronary blood flow from digital coronary angiograms

A method for measuring regional variation in coronary blood flow has been developed using image processing techniques applied to sequences of digital coronary angiograms. A series of digital subtraction angiography images is used as a basic data set to form parametric images of blood volume and of contrast arrival time under varying conditions of blood flow. A model relating the image-derived parameters and physiological flow has been developed and validated in animal experiments. The use of rapid image processing methods permits the formation of flow parameter images in a short time, making the method suitable for online assessment of interventional procedures.<<ETX>>

A rapid, user-friendly method for entering lesion morphology data after cardiac catheterization

An expert panel task force of the AHA/ACC reported that determination of lesion morphology was predictive of adverse events after diagnostic/interventional procedures. The authors have developed a coronary artery tree diagramming system that employs a graphical user interface to allow rapid and facile data entry by clinical personnel. In addition to the baseline anatomic descriptors of coronary artery anatomy, lesion morphology descriptors comprising each data element comprising the AHA/ACC class are easily entered. Average time for data entry per tree is 2 min. The system is used on a daily basis at Duke University Medical Center for recording the results of the 20-25 diagnostic and 10-15 interventional procedures. The recording of complex lesion morphology data can now be easily performed as part of routine clinical care in large clinical populations undergoing catheterization procedures.<<ETX>>

Multimodality cardiac image review station using dynamic decompression of JPEG images

A cardiology review station for clinical use has been developed which can decompress, zoom, and display full resolution JPEG-encoded cardiac angiograms and echocardiograms in real- time (30 frames/second). The review station is installed in a network which includes a digital image archival system throughout Duke University Medical Center. The review station consists of a DEC 3000/600 AXP workstation with a DEC J300 sight and sound multimedia board. The J300 is used to decompress up to 45 true color JPEG-encoded frames/sec. at normal (512 X 512) resolution and 30 frames/sec. at 1.5 X zoom. Digitally acquired 512 X 512 X 8 bit monochrome angiograms as well as 600 X 430 X 8 bit color and monochrome echocardiograms are transferred to the workstation where they are JPEG-encoded in real time using the J300 board. A compression factor of approximately 15:1 is being used. A graphical user interface (GUI) developed using OSF/Motif 1.2 enables a clinical user to simultaneously display and control several image sequences. A sequence can be retrieved in under three seconds and displayed dynamically in forward or reverse directions with instantaneous speed control. Utilizing a commercial relational database (Sybase), the GUI organizes image sequences for a patient by image modality, location, time, and view. A schematic representation of cardiac anatomy allows a user to view specific angiographic image sequences by selecting appropriate objects in the anatomic diagram.