Cardiac catheterization laboratory imaging quality assurance program.

With the recent approval of the National Electrical Manufacturers Association (NEMA) standard for "Characteristics of and Test Procedures for a Phantom to Benchmark Cardiac Fluoroscopic and Photographic Performance," comprehensive cardiac image assurance control programs are now possible. This standard was developed by a joint NEMA/Society for Cardiac Angiography and Interventions (SCA&I) working group of imaging manufacturers and cardiology society professionals over the past 4 years. This article details a cardiac catheterization laboratory image quality assurance and control program that includes the new standard along with current regulatory requirements for cardiac imaging. Because of the recent proliferation of digital imaging equipment, quality assurance for cardiac imaging fluoroscopy and digital imaging are critical. Included are the previous works recommended by the American College of Cardiology (ACC) and American Heart Association (AHA), Society for Cardiac Angiographers and Interventions (SCA&I), and authors of previous image quality subjects.

Telemedicine consultations in congenital heart disease: assessment of advanced technical capabilities.

OBJECTIVE: To assess the value of adding remote pointer and dynamic display capabilities to a telemedicine system designed to provide consultative services for patients with congenital heart disease. MATERIAL AND METHODS: Independent observations by the referring physician and the consulting physician provided the data for the assessment. Fifty-four teleconsultations involving 38 patients with 21 different congenital heart diseases were analyzed. The teleconsultations were based on previously obtained cineangiograms that were digitized and then transmitted by combined satellite and terrestrial-based technology. The observations, recorded by each physician at his workstation at the time of each teleconsultation, were summarized and analyzed statistically. RESULTS: In 108 observations, the pointer was believed to be helpful in 72 (67%), and dynamic display was helpful in 96 (89%). CONCLUSION: This study suggests that use of a pointer and dynamic display enhances teleconsultations for patients with congenital heart disease.

Real-time measurement of radiation exposure to patients during diagnostic coronary angiography and percutaneous interventional procedures.

OBJECTIVES: The aim of this study was to accurately assess the radiation exposure received by patients during cardiac catheterization in a large sample representative of the current state of practice in cardiac angiography. BACKGROUND: Radiation exposure to patients and laboratory staff has been recognized as a necessary hazard in coronary angiography. The effects on x-ray exposure of the increased complexity of coronary angiographic procedures and, in particular, the increasing use of coronary artery stenting, have not been adequately addressed in previous studies. METHODS: X-ray exposure measurements were performed on a consecutive series of 972 patients undergoing 992 diagnostic and interventional studies in the Mayo Clinic catheterization laboratory within an eight week period in late 1997. Data were acquired from 706 diagnostic procedures and 286 interventional procedures using a real-time exposure measurement system to continuously calculate and record the exposure rate and total exposure, reflecting all parameters relevant to the specific patient and procedure situation. RESULTS: The median exposure for all 992 procedures was 41.8 mC/kg (162.1 R); the corresponding values for diagnostic and interventional procedures were 34.9 and 95.6 mC/kg, respectively (135.3 vs. 370.5 R). There were significant differences in the fluoroscopy exposure time between diagnostic and interventional procedures: 4.7 min vs. 21.0 min. Heavier patients (>83 kg) received x-ray exposures at a significantly higher rate than did lighter patients (<83 kg) during both fluoroscopy and cine; 44.9 mC/kg/min (173.9 R/min) vs. 27.9 mC/kg/min (108.3 R/min) for cine exposure rate and 2.3 mC/kg/min (8.8 R/min) vs. 1.5 mC/kg/min (5.8 R/min) for fluoroscopy exposure rate. CONCLUSIONS: Changes in practice have led to higher values for patient x-ray radiation exposures during cardiac catheterization procedures. The real-time display and recording of x-ray exposure facilitates the reduction of exposure in the catheterization laboratory.

Optimization of wide-area ATM and local-area ethernet/FDDI network configurations for high-speed telemedicine communications employing NASA's ACTS.

A high data rate terrestrial and satellite network was implemented to transfer medical images and data. This article describes the a optimization of the workstations and switching equipment incorporated into the network. Topics discussed in this article include tuning of the network software, the configuration of the Sun Microsystems workstations, the FORE Systems asynchronous transfer mode switches, as well as the throughput results of two telemedicine experiments undertaken by Mayo's physician staff. The technical staff was successful in achieving the data throughput needed by the telemedicine software; particularly important was the proper determination of peak throughput and TCP window sizes to ensure optimum use of the resources available on the Sun Microsystems and Hewlett Packard workstations.

Cine film replacement: digital archival requirements and remaining obstacles.

The acceptance of the Digital Imaging and Communication in Medicine (DICOM) standard and the Compact Disk-Recordable (CD-R) as the interchange medium have been critical developments for laboratories that need to move forward on the cine replacement front, while at the same time retain a means to communicate with other centers. One remaining essential component which has not been satisfactorily addressed is the issue of how digital image data should be archived within an institution. Every laboratory must consider the diverse issues which affect the choice of a digital archiving system. These factors include technical and economic issues, along with the clinical routines prevailing in their laboratory. A complete understanding of the issues will lead to the formulation of multiple options which may prove acceptable and will help to overcome the last obstacle which remains for the complete replacement of cine film in the cardiac catheterization laboratory.

Replacement of cinefilm with a digital archive and review network.

The replacement of cinefilm with digital cardiac angiography has accelerated significantly in recent years with the development and widespread adoption of the DICOM standard for interchange of procedure image data. While the acceptance of the Compact Disk-Recordable (CD-R) media has provided the opportunity for numerous laboratories to eliminate cinefilm in all its functions, the task is more complex for larger catheterization laboratories which require the use of high speed networks and automated libraries. The Cardiac Laboratory at the Mayo Clinic has implemented the final stages of a large-scale network and archive which meets a large institution's demanding requirements for access, speed, and storage for high volumes of digital cardiac angiographic images. Initial experience with the system demonstrates that this approach will be a successful one for the elimination of cinefilm and the employment of digital imaging and networking technology. In addition, direct access to digital image records will also facilitate the integration of image data with other clinical information acquired and stored in a digital format.

Does the use of new intracoronary interventional devices prolong radiation exposure in the cardiac catheterization laboratory?

OBJECTIVES: The aim of this study was to compare the duration of radiation exposure associated with new percutaneous coronary interventional devices with that associated with conventional balloon angioplasty. BACKGROUND: Radiation exposure levels have been documented to be higher with coronary balloon angioplasty than with routine diagnostic coronary angiography. However, the effect of new interventional devices on radiation exposure has not been studied. METHODS: Fluoroscopic and cineangiographic data from the Mayo Clinic cardiac catheterization laboratory data base of patients having single-segment coronary intervention during a recent 46-month period were retrospectively analyzed. Of 897 patients studied, 646 underwent balloon angioplasty, 138 directional coronary atherectomy (42 with adjunctive balloon angioplasty), 76 excimer laser angioplasty (50 with adjunctive balloon angioplasty) and 37 placement of an intracoronary stent (16 emergencies). RESULTS: Duration of fluoroscopy during balloon angioplasty was 24 +/- 18 min, which was longer than with directional atherectomy (18 +/- 8 min; p = 0.001). Fluoroscopy time was 25 +/- 17 min with laser angioplasty and 29 +/- 15 min with elective stent placement (neither time was significantly different from that with balloon angioplasty). When atherectomy or laser angioplasty was performed with adjunctive balloon angioplasty or if emergency intracoronary stent placement was performed, the duration of fluoroscopy was significantly prolonged compared with balloon angioplasty alone. CONCLUSIONS: Fluoroscopy duration is not prolonged with the use of new interventional coronary devices compared with conventional angioplasty unless adjunctive balloon angioplasty is used or emergency stent placement is required.

Isn't it time to abandon cine film?

Cine has served our needs well since the early 1950s. For the first time, it allowed recording of motion studies of the cardiac structures on film. The cine technique has been standardized over the years, both the camera and the display. Cine filming techniques, however, have not advanced, except for new film products with faster emulsions and better-quality films. Video electronic imaging has made rapid advancements. These were prompted by the broadcast industry when the requirements for color were developed in the 1960s and by the advent of new recording techniques that provided a very stable video time base from analog tape recorders. The medical field has been able to capitalize on these developments and to produce some of our own that have not been applied in the broadcast world. These include pulsed progressive 525-line video acquisition of cardiac images in the cardiac catheterization laboratory. We also have been able to capitalize on the improved detector technology that the broadcast world has developed, such as the plumbicon pickup tubes, which produce images with very little lag and so provide images with improved resolution. These developments also have enabled us to reduce radiation to both the patient and the laboratory personnel, especially with implementation of the pulsed progressive acquisition, with which the dose has been reduced 50%. With the advent of interventional procedures in the cardiac catheterization laboratory, the need to assess images immediately cannot be fulfilled by cine filming because of the requirement for the processing of the film with its inherent delays. Quantification of cardiac structures is required to assess the outcome of interventional techniques.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of pulsed progressive fluoroscopy on reduction of radiation dose in the cardiac catheterization laboratory.

The increased application of therapeutic interventional cardiology procedures is associated with increased radiation exposure to physicians, patients and technical personnel. New advances in imaging techniques have the potential for reducing radiation exposure. A progressive scanning video system with a standard vascular phantom has been shown to decrease entrance radiation exposure. The effect of this system on reducing actual radiation exposure to physicians and technicians was assessed from 1984 through 1987. During this time, progressive fluoroscopy was added sequentially to all four adult catheterization laboratories; no changes in shielding procedures were made. During this time, the case load per physician increased by 63% and the number of percutaneous transluminal coronary angioplasty procedures (a high radiation procedure) increased by 244%. Despite these increases in both case load and higher radiation procedures, the average radiation exposure per physician declined by 37%. During the same time, the radiation exposure for technicians decreased by 35%. Pulsed progressive fluoroscopy is effective for reducing radiation exposure to catheterization laboratory physicians and technical staff.

Optimal display of the coronary arterial tree with an upscan 1,023-line video display system.

Differences of opinion exist as to whether visualization of the coronary arterial tree is better with 525-line or 1,023-line video imaging systems. The 1,023-line acquisition has been associated with image degradation; 525-line display, however, has prominent raster lines that may also degrade the image. For evaluation of this issue, identical coronary arterial images were obtained with 525-line acquisition and then displayed with either 525-line or 1,023-line display. The 525-line acquisition with digital upscan 1,023-line display had superior image quality compared with 525-line display. With the use of 525-line acquisition and 1,023-line display, video images were similar to or slightly better than the identical cineangiographic images.

Technical consideration for a new X-ray video progressive scanning system for cardiac catheterization.

The widespread growth of interventional angiographic procedures has expanded the use of X-ray video systems. Reduced radiation exposure to the patient and staff has been recently reported by implementing a new pulsed progressive scanning video system. We have shown that this system, which enables the pulsing of the X-ray generator at 30 pulses per second, results in a 50% reduction in radiation exposure. The technical parameters and implementation of a progressive scanning video system are discussed. Image quality, temporal and spatial resolution, and signal-to-noise ratio (SNR) were assessed using conventional interlaced and progressive video scanning. These comparisons documented improved resolution, no degradation of ejection fraction measurements, improved clinical images, and a 1.0-dB improvement in the SNR with the progressive scanning. Progressive scanning video systems reduce radiation exposure and provide an objective improvement in image quality over conventional scanning video systems.

Video x-ray progressive scanning: new technique for decreasing x-ray exposure without decreasing image quality during cardiac catheterization.

A newly developed video x-ray progressive scanning system improves image quality, decreases radiation exposure, and can be added to any pulsed fluoroscopic x-ray system using a video display without major system modifications. With use of progressive video scanning, the radiation entrance exposure rate measured with a vascular phantom was decreased by 32 to 53% in comparison with a conventional fluoroscopic x-ray system. In addition to this substantial decrease in radiation exposure, the quality of the image was improved because of less motion blur and artifact. Progressive video scanning has the potential for widespread application to all pulsed fluoroscopic x-ray systems. Use of this technique should make cardiac catheterization procedures and all other fluoroscopic procedures safer for the patient and the involved medical and paramedical staff.

Fluoroscopic imaging: quantitation of image lag or smearing.

Image lag (smearing or persistence of the image) is a characteristic of video imaging systems that is exhibited when rapidly moving objects are blurred due to motion. Video pick-up tubes can exhibit differing amounts of image lag depending on the age of the tube, the amount of light reaching the tube, the set-up parameters used (e.g., beam current and target voltages, etc.), and the tube type. We describe a new quantitative method for measuring image lag that requires only a storage oscilloscope and an inexpensive shutter. Examples of lag measurements on different systems under varying clinical conditions are given. Suggested limits for clinically acceptable amounts of image lag range from 10% to 50% depending on the particular application.

Clinical evaluation and application of cardiac laboratory high-definition video systems.

This study evaluated a new high line rate (1,023-line) high band-width (10 MHz) system, compared it to our high-definition, 525-line video system, and compared both video systems to 35-mm cine angiography in 117 patients undergoing clinically indicated coronary angiography. The subjective image quality of the 1,023-line video system was not significantly better than that of the 525-line system. High line rate, high band-width systems may have theoretical advantages, but the increased noise level under clinical angiographic conditions reduces their diagnostic quality. Comparison between video (all modes) and cine images resulted in cine being rated as the best modality, but the differences were slight. Radiation levels required for video imaging, however, were significantly less than those required for cine recording. Current clinical and computer interactive uses of video systems in the cardiac laboratory are described. The eventual role and potential replacement of cine recording by video tape systems will depend on continued developments in video recording techniques.

Technical considerations for cardiac laboratory high-definition video systems.

With the expanding use of video systems in diagnostic imaging a significant benefit could be obtained by applying this technology in the cardiac catheterization laboratory. Reduced radiation exposure to the patient and staff, reduced examination cost by the elimination of cine film and equipment (cameras, processors, etc), and instant replay of each injection would result in improved patient care. We discuss the technical parameters of a video system which we have found suitable for diagnostic purposes and describe how this system is used on a day-to-day basis. In addition, the technical aspects of higher bandwidth, higher line rate systems is presented, and we show that these more sophisticated systems provide no advantage over conventional high-definition television and, in fact, degrade the diagnostic quality of the image.