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

Fluoroscopic image quality in the film and filmless eras: a standardized comparison performed in coronary interventional facilities

One hundred and one coronary interventional systems (45 primarily film-based predigital systems, labeled group 1; and 56 filmless digital systems, labeled group 2) were examined over a 5-year period using a standardized imaging phantom. Fluoroscopic image intensifier input dose, high-contrast spatial resolution, low-contrast sensitivity, and static and dynamic low-contrast resolution were assessed under several conditions simulating patient body habitus. The distribution of spatial resolutions in group 2 facilities favored higher line pair resolution over group 1 (P = 0.01). Contrast sensitivity (smallest-diameter hole visualized) was consistently and significantly enhanced with the use of digital imaging under both medium (P = 0.001) and large (P = 0.002) patient habitus simulations. Low-contrast video resolution (number of wires seen) under static (P = 0.007) and dynamic (P = 0.002) conditions was also improved in the digital facilities. However, image intensifer input dose was similar in both groups (group 1 median dose, 23 mR/min; group 2 median dose, 26 mR/min; P = NS). Fluoroscopic spatial resolution in digital filmless laboratories was significantly improved when compared to predigital, film-based laboratories. Low-contrast sensitivity and low- contrast video resolution under both static and dynamic conditions were also significantly improved in the digital laboratories. Notably, the input dose of radiation required to produce these improved fluoroscopic images was similar between groups.

X-ray fluoroscopy spatio-temporal filtering with object detection

One potential way to reduce patient and staff X-ray fluoroscopy dose is to reduce the quantum exposure to the detector and compensate the additional noise with digital filtering. A new filtering method, spatio-temporal filtering with object detection, is described that reduces noise while minimizing motion and spatial blur. As compared to some conventional motion-detection filtering schemes, this object-detection method incorporates additional a priori knowledge of image content; i.e. much of the motion occurs in isolated long thin objects (catheters, guide wires, etc.). We create object-likelihood images and use these to control spatial and recursive temporal filtering such as to reduce blurring the objects of interest. We use automatically computed receiver operating characteristic (ROC) curves to optimize the object-likelihood enhancement method and determine that oriented matched filter kernels with 4 orientations are appropriate. The matched filter kernels are simple projected cylinders. We demonstrate the method on several representative X-ray fluoroscopy sequences to which noise is added to simulate very low dose acquisitions. With processing, we find that noise variance is significantly reduced with slightly less noise reduction near moving objects. We estimate an effective exposure reduction greater than 80%

Model for perception of pulsed fluoroscopy image sequences

Pulsed fluoroscopy at reduced frame rates can be used to lower x-ray dose with equivalent detection (hereafter called equivalent perception) of low-contrast, stationary objects. Experimentally average dose savings of 22%, 38%, and 49%, for pulsed fluoroscopy at 15, 10, and 7.5 acquisitions per second, respectively, are documented. Dose savings depend on object size, with fewer savings for smaller objects. To explain these data, we extend the framework of an ideal observer with three models for the spatiotemporal response of the human visual system (HVS). They are model 1, separable; model 2, nonseparable; and model 3, nonseparable with internal observer noise. With no free parameters, model 1 predicts the average dose savings within a 3% difference but does not describe the effect of object size. Models 2 and 3 explain the influence of size, and model 3, with a single free parameter, fits the measurements best. Perception of pulsed fluoroscopy is thus well described in terms of spatiotemporal processing by the HVS.

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.

Balloon angioplasty of chronic total coronary artery occlusions: what does it cost in radiation exposure, time, and materials?

Coronary angioplasty of chronic total occlusions is known to have a lower success rate and higher frequency of restenosis than angioplasty of subtotal stenoses, but there are no data describing the additional time, resources, and radiation exposure associated with this procedure. The purpose of this study was to compare these features in 90 consecutive patients who underwent angioplasty of a total occlusion (group 1) to those of 100 consecutive patients who underwent angioplasty of a subtotal stenosis (group 2). Angioplasty was successful in 60% of group 1 and in 94% of group 2 patients. Procedures were longer in group 1 and significantly more guide catheters, angioplasty balloon catheters, and guide wires were required per patient compared to group 2. The volume of contrast media used in each group was similar. Estimates of radiation entry exposure, calculated from fluoroscopy exposure times and using data from phantom studies, were 53 R (roentgen) per patient in group 1 vs. 34 R in group 2. These procedures were performed using pulsed progressive fluoroscopy; radiation exposure would be considerably higher using conventional fluoroscopic systems. Cineangiographic radiation exposures were similar for each group and accounted for an average additional exposure of 14-22 R for each procedure. Total radiation exposure was reduced in both groups when the angioplasty procedure was combined with the diagnostic angiogram. These observations should be considered when dilation of a total occlusion is planned. Efforts to reduce the amount of radiation exposure should remain a priority in interventional catheterization laboratories.

Advances in interventional cardiology

The field of interventional cardiology is growing widely. This growth is the result of improvements in existing technology, development of new technology, and expansion of criteria for the selection of patients. Percutaneous transluminal coronary angioplasty (PTCA) remains the mainstay and is used to treat an increasing number of patients with coronary artery disease that manifests as stable or unstable angina or acute myocardial infarction. Atherectomy is being used to "debulk" lesions and remove atheromatous plaque as well as to remove intimal flaps after PTCA. The insertion of an intracoronary stent is a strategy designed to treat intimal dissections and acute closure as well as to attempt to decrease the incidence of restenosis. Finally, intracoronary laser therapy--independently or in combination with PTCA--is being evaluated as a treatment approach for more diffuse disease, acute occlusion, and prevention of restenosis.

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.