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PubMedDate not supplied

The AAPM/RSNA physics tutorial for residents: fluoroscopy: optical coupling and the video system.

In fluoroscopic/fluorographic systems, an image intensifier is optically coupled to recording cameras. The optical distributor is responsible for transmitting a focused image from the output phosphor of the image intensifier to the focal planes of the cameras. Each camera has an aperture, which is used to control the level of light reaching its focal plane. The aperture setting determines the patient x-ray exposure level and the image noise level. Increasing the x-ray exposure reduces image noise; reducing the x-ray exposure increases image noise. Fluoroscopic/fluorographic systems always include a video camera. The functions of the video system are to provide for multiple observers and to facilitate image recording. The camera head contains an image sensor, which converts the light image from the image intensifier into a voltage signal. The device used to generate the video signal is a pickup tube or a charge-coupled device sensor. The method used is raster scanning, of which there are two types: progressive and interlaced. The vertical resolution of the system is primarily determined by the number of scan lines; the horizontal resolution is primarily determined by the bandwidth. Frame rate reduction can be a powerful tool for exposure reduction.

Angiography, Digital Subtraction↗
PubMed1980

Clinical applications of computerized fluoroscopy: the extracranial carotid arteries.

Preliminary results obtained with a new computerized fluoroscopic apparatus in examination of the extracranial carotid arteries are described. All patients had clinical signs of symptoms of extracranial occlusive vascular disease. In most cases, image quality was sufficient to display patency of the internal carotid arteries, with excellent correlation between intravenous and conventional angiography. While the new technique is not totally noninvasive, it does eliminate many of the risks and costs of conventional arteriography.

Arterial Occlusive Diseases↗
PubMed1982

Simultaneous bi-plane digital video-fluoroscopy.

A prototype system for digital subtraction angiography that is capable of acquiring digitized video-fluoroscopic images simultaneously from both anterior and lateral imaging chains of a conventional bi-plane system was developed. A hardware module that takes images from both the anterior and lateral video cameras and displays them both on a single video image prior to digitization was designed and constructed. The three-dimensional information provided by a digital bi-plane images should improve the accuracy of cardiac-ventricular function studies. In addition, bi-plane imaging should reduce the need for additional views and the associated repeated injections of contrast media. With this technique, digital bi-plane imaging can be carried out with commercially available systems without duplication of the digital-processing chain.

Animals↗
PubMed1982

The elimination of grids during intensified fluoroscopy and photofluoro spot imaging.

Grids can significantly increase the contrast of diagnostic radiologic images, but they increase the dose to the patient and staff by a factor of two or more. Image quality with and without grids for fluoroscopic and photofluoro spot imaging of lower gastrointestinal studies has been examined. The authors show that dose reductions between one-third and one-half can be obtained with little or no degradation in contrast and diagnostic image quality if grids are not used for gastrointestinal examinations involving image intensifiers.

Digestive System↗
PubMed1983

Work in progress: hybrid temporal-energy subtraction in digital fluoroscopy.

Initial clinical results using a digital fluoroscopic implementation of the combined time-energy ("hybrid") subtraction technique are described, with emphasis on carotid and renal imaging. Where patient motion artifacts are due to soft-tissue motion alone, hybrid subtraction can remove them. Due to the need for a finite separation time between high- and low-energy pairs, however, the present implementation of the hybrid technique is not completely immune to soft-tissue motion. The intrinsic signal-to-noise ratio of hybrid imaging is less than that of conventional temporal subtraction. However, since the low-energy temporal subtraction images are included in the hybrid data set, the diagnostic quality of the examination is not compromised.

Analog-Digital Conversion↗
PubMed1984

Fluoroscopy in children: low-exposure technology.

A fluoroscopic system was modified to achieve a 95-98% reduction in radiation exposure and dosage to patients compared with other systems that reduce fluoroscopic radiation dosage. This reduction was accomplished by custom selection of a high conversion-factor, triplemode image intensifier; custom design of a variable-dose rheostat, allowing maximum operator control of video camera gain; installation of an erbium rare-earth beam filter on the x-ray tube; and addition of a digital noise reducer (recursive filter). A total of 1,577 fluoroscopic examinations has been performed on this system, with excellent results. Contrast resolution was increased, while spatial resolution was maintained. Noise (quantum mottle) has been reduced by the addition of a digital image processor. Advantages of the ultra-low-dose system include: all fluoroscopic work is performed in a smooth, continuous real-time mode; the radiation exposure and dose saving is significantly greater than with pulsed and other proposed low-dose fluoroscopic systems; and the system automatically adapts for the wide variation in patient size routinely encountered in pediatric and adult radiology. The image quality is now such that this system could be used routinely for both adults and children.

Adult↗
PubMed1985

Tenckhoff peritoneal dialysis catheters: the use of fluoroscopy in management.

Manipulation of the Tenckhoff catheter under fluoroscopic guidance is a useful procedure in patients who undergo chronic ambulatory peritoneal dialysis (CAPD). We reviewed 50 manipulations in 28 patients. There were no significant complications attributable to the procedure. Ten per cent of the manipulations were performed for visceral pain, 40% for malfunction within the first two weeks of catheter placement, and the remaining 50% for malfunction after two weeks of adequate dialysate flow. Overall, an initial success rate of 88% was recorded, and, after long term study, a durable success rate of 58% was demonstrated. Early malfunction (i.e., within the first two weeks) is a more ominous prognostic indicator than previously realized, with only 30% of these manipulations ultimately succeeding vs. 60% of manipulations in late onset catheter failure. Nevertheless, at least one attempt is warranted in manipulation of a malfunctioning Tenckhoff catheter.

Catheterization↗
PubMed1989

Incarcerated obturator hernia: case diagnosed at barium enema fluoroscopy.

Incarcerated obturator hernia is an uncommon entity that on occasion may produce specific radiographic findings and clinical signs (Howship-Romberg sign) that permit diagnosis prior to celiotomy. A case is reported in which the diagnosis was suggested when pain in the thigh was elicited during the course of a barium enema examination.

Aged↗
PubMed1991

Exposure rates in high-level-control fluoroscopy for image enhancement.

High-level fluoroscopic boost options that exceed conventional exposure limits are available as a means of reducing quantum mottle during angiography. Federal law does not specify exposure limits for such high-level controls but requires specific means of activation to safeguard against inadvertent use. The American Association of Physicists in Medicine recently recommended that high-level exposure rates not exceed 2.58 mC/kg/min (10R/min). At six institution surveyed, maximum exposure rates ranged from 5.42 to 24 mC/kg/min (21-93 R/min). Activation of high-level capability varied from a simple foot switch to a keyed interlock requiring a second operator to engage. There appears to be no industry coherence in high-level control exposure limits as yet, although the Center for Devices and Radiological Health recently initiated an investigatory program.

Environmental Exposure↗
PubMed1999

Severe skin reactions from interventional fluoroscopy: case report and review of the literature.

Some patients with certain preexisting health conditions may be at elevated risk for unusually intense radiation-induced skin reactions and late tissue damage from high-dose interventional procedures. The authors present a case report of a patient with mixed connective tissue disease and non-insulin-dependent diabetes mellitus who developed an unusual complication after placement of a transjugular intrahepatic portosystemic shunt. On the basis of a review of the literature, the following experiences may help identify patients at increased risk: previous high-dose procedures, connective tissue disease, diabetes mellitus, and homozygosity for ataxia telangiectasia.

Diabetes Mellitus, Type 2↗