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At least 523 records · Page 29Linked to original sources
PubMed2003

Prosthetic mitral valve thrombosis: can fluoroscopy predict the efficacy of thrombolytic treatment?

BACKGROUND: Thrombolysis (T) is an effective therapy for prosthetic valve thrombosis (PVT). Debate still exists as to which clinical or noninvasive finding best predict the result of T. The aim of the study was to investigate the role of fluoroscopy (F) to predict efficacy of T in pts with mitral PVT. METHODS: We evaluated 17 consecutive pts with bileaflet mitral PVT. F criteria for PVT were: abnormal disc motion and calculated opening angle >25 degrees. T was carried out with tissue-type plasminogen activator (tPA; 100 mg over 3 hours followed by heparin infusion for 24 hours) and was considered successful when normalization of leaflet motion and opening angle occurred. Results were evaluated according to symptom duration (<21 days, early PVT; >21 days, late PVT) and to F pattern of PVT (blocked leaflet versus hypomobile leaflet). RESULTS: F showed disc motion alteration in 24 of 34 leaflets: 8 leaflets were blocked, whereas 16 were hypomobile. Early (12.7+/-6.1 days, range 3-21) and late (113+/-114 days, range 28-365) PVT was present in 8 and 7 pts, respectively. Thrombolysis was successful in 20 of 24 leaflets. Blocked leaflet fully recovered only in early PVT (n=4) pts, whereas they remained blocked in late PVT (n=4). On the contrary, in all of the cases with hypomobile leaflet, disc motion normalized regardless duration of symptoms and extent of disc motion reduction. Interestingly, 4 leaflets with late PVT was diagnosed as blocked by trans-thoracic (TTE). F showed a residual disc movement in all: they fully recovered after T. Two pts with late PVT had both leaflets affected (1 blocked +1 hypomobile); although blocked leaflet did not respond to T, the normalization of hypomobile significantly improved clinical condition. CONCLUSIONS: F can predict result of T in mitral PVT. PVT with F evidence of hypomobile leaflet always recovers regardless of symptom duration and extent of disc motion reduction, suggesting that the small amount of thrombus needed to interfere with discs motion in bileaflet prostheses remains sensitive to T even after a long time. PVT with F evidence of blocked leaflet has a favorable response to T only in case of early PVT. Late PVT with blocked leaflet does not respond to T, suggesting a larger and stratified thrombus and the coexistence of pannus and, in our series, always required surgery. However, if a hypomobile leaflet coexists, T may be used to restore normal movement of hypomobile leaflet so that to improve patient clinical and hemodynamic condition before operation.

Echocardiography, Doppler↗
PubMed2000

Global right atrial mapping of human atrial flutter: the presence of posteromedial (sinus venosa region) functional block and double potentials : a study in biplane fluoroscopy and intracardiac echocardiography.

BACKGROUND: Previous studies of atrial flutter have found linear block at the crista terminalis; this was thought to predispose the patient to the arrhythmia. More recent observations, however, have demonstrated crista conduction. We sought to characterize the posterior boundary of atrial flutter. METHODS AND RESULTS: Patients with counterclockwise flutter (n=20), clockwise flutter (n=3), or both (n=5) were studied using two 20-pole catheters. Biplane fluoroscopy determined catheter positions. During counterclockwise flutter, craniocaudal activation occurred along the entire lateral and posterior right atrial walls. Septal activation proceeded caudocranially. In all patients, a line of block was seen in the posteromedial (sinus venosa) right atrium; this was manifested by the presence of double potentials where the upward and downward activations collided. Anatomic location was confirmed by intracardiac echocardiography in 9 patients. In patients with clockwise flutter, the line of block and double potentials were seen in the same location during counterclockwise flutter, but the activation sequence around the line of block was reversed. Pacing near the site of double potentials during sinus rhythm excluded a fixed line of block, and premature atrial complexes demonstrated functional block with manifest double potentials. In 2 patients, posterior ectopy organized to subsequently initiate isthmus-dependent atrial flutter. CONCLUSIONS: (1) A functional line of block is seen at the posteromedial (sinus venosa region) right atrium during counterclockwise and clockwise atrial flutter. (2) All lateral wall right atrial activation can be uniform during flutter, without linear block or double potentials in the region of the crista terminalis. (3) Activation at the site of posteromedial right atrial functional block can organize to subsequently initiate isthmus-dependent atrial flutter.

Adult↗
PubMed1979

Percutaneous transperitoneal fluoroscopy-guided fine-needle biopsy of lymph nodes.

After lymphography from the foot, with uncertain findings, fine-needle biopsy during fluoroscopy was performed in 107 patients. In 69 patients with possible metastases, involvement was demonstrated in 46, confirmed in 43 at operation. Lymph node involvement by general lymphatic disease was suggested in 38 patients, with biopsy confirmation in 12. In metastatic disease non-representative material was obtained in only 2 patients, in general lymphatic disease in 10. No significant complications occurred, and the side effects were small.

Biopsy, Needle↗
PubMed1980

Fluoroscopy without the grid: a method of reducing the radiation dose.

The anti-scatter grid has been removed from the fluoroscopic set during the course of over 80 contrast examinations performed routinely during the ordinary workload of a busy paediatric radiology department. This manoeuvre approximately halves the radiation dose to the patient during both fluoroscopy and radiography. Our experience suggests that the degree of loss of contrast consequent on the abandonment of the grid is diagnostically acceptable during many examinations performed on children (of all ages), when balanced against the lower radiation dose received. In addition, an assessment has been made of the "contrast improvement factor" of the grids in two fluoroscopic sets in common use, using tissue-equivalent phantoms of various thicknesses. Although the contrast is significantly improved by the use of the grid, to a degree dependent on various factors, the relevance of this improvement in clinical radiology will depend on exactly what information is being sought. It is recommended that radiologists should use the grid with discretion when performing fluoroscopic examinations on children and that the apparatus for such examinations should have the capability for easy removal and reintroduction of the grid.

Adolescent↗
PubMed1983

Gastrointestinal fluoroscopy: patient dose and methods for its reduction.

The aim of this study was to demonstrate a method which could be used to identify factors which contribute to the radiation exposure to patients from fluoroscopy during contrast examinations of the gastro-intestinal tract. Measurements of exposure made at the level of the X-ray tube collimator were extrapolated to obtain entrance exposure at the centre of the field and used as an index of the integral dose to the patient. Such data have heretofore been unavailable. The population studied included 65 patients ranging in age from 1 month to 21 years. In an initial study, median entrance exposure at the field centre for barium swallow examinations ranged from 0.98 to 1.7 mC/kg (3.8 to 6.6 R); barium meal: 1.9-5.7 mC/kg (7.4-22 R); barium meal with small bowel: 1.4-7.7 mC/kg (5.3-30 R); barium enema: 0.93-7.7 mC/kg (3.6-41 R). Gonadal dose, measured in males, ranged from undetectable to 0.71 mGy (71 mrad). The presence of contrast medium in the fluoroscopic field increased the exposure from a single 100 mm spot film, taken with automatic exposure control, by a factor of up to 16, and fluoroscopic exposure rate, using automatic brightness control, by a factor of 2 or more. We recommend modifications in the operation and design of fluoroscopic equipment, especially when fitted with brightness and exposure controls, for the reduction of patient exposure. Implementation of two modifications, a high/low dose switch, and a variable aperture iris diaphragm, reduced patient exposure from 1.4 to 3.4 times.

Adolescent↗
PubMed1985

A set of X-ray test objects for quality control in television fluoroscopy.

The history of performance testing in Leeds of television fluoroscopic systems is briefly outlined. Using the visual, physical and technological requirements as a basis, a set of nine test objects for quality control in television fluoroscopy is described. The factors measured by the test objects are listed in the introduction; the test objects and their function are fully described in the remainder of the paper. The test objects, in conjunction with a television oscilloscope, give both subjective and objective information about the X-ray system. Three of the test objects enable the physicist or engineer to adjust certain aspects of the performance of the X-ray system. The set of nine test objects is available commercially.

Fluoroscopy↗
PubMed1993

Radiation doses to paediatric patients undergoing less common radiological procedures involving fluoroscopy.

A semi-automated dosimetry survey has been undertaken to monitor the radiation doses to patients in a paediatric fluoroscopy room. The doses were assessed using large area Diamentor ionization chambers to measure dose x area product, and by means of thermoluminescent dosemeters attached to the patient's skin in various places. Details of patients and examinations were entered into a computer, all information being stored on a data base. Many radiological examinations have been monitored, including renal and jejunal biopsies, nephrostograms, loopograms, tracheograms and fistulograms. Patients included in the study have been divided into three age bands for dose assessment. Radiation doses for different types of examination have been compared, including more common examinations for which data have been previously presented.

Adolescent↗
PubMed1995

Radiation dose reduction in paediatric fluoroscopy using added filtration.

Studies on a water phantom indicate that the insertion of extra tube filtration combined with the removal of the antiscatter grid can reduce the total energy imparted from paediatric fluoroscopy by a factor of more than four when automatic exposure control is used. The omission of the grid is responsible for up to 40% of the reduction while the addition of 0.7 mm steel filtration is found to account for a further reduction in energy imparted of between 57% and 70%, for depths of water simulating small patients of 6-16 cm thickness. For all contrast paediatric examinations the reduction in image quality was considered to be small and the diagnostic information unimpaired with the filter in place.

Child↗
PubMed1996

Short communication: use of the output video signal for dynamic range, brightness control and image memory assessment in X-ray fluoroscopy.

The output video signal from three X-ray fluoroscopy machines was recorded with a storage oscilloscope to calculate the dynamic range of their image intensifier television camera chains. The two MERATE MTH90 and MGR50hf machines employed the same imaging chain but the response of the former to exposure was significantly lower because of a three channel light distribution optical system which was installed but not used. The CGR Stenoscope machine was found to have a very narrow dynamic range to the extent that it was not usable. Additional measurements on the CGR machine showed that the image intensifier brightness control mechanism would produce stabilized brightness in less than 0.4 s and it proved to be faster than the manual selection of exposure parameters. The quality of the image stored in the memory device on the same system was compared with the original by subtracting the two video signals on the oscilloscope and thus acquiring a quantitative measure of their difference.

Fluoroscopy↗
PubMed2001

Influence of radiologists' sex and training on fluoroscopy doses during barium enema.

Variables influencing radiation exposure were studied using analysis of covariance in 523 double contrast barium enemas performed by 21 radiology residents (12 female, 9 male). Dose-area products (DAPs) (ns), number of exposures per patient (p < 0.05) and screening times (p < 0.05) were higher for female residents (mean 52.0 Gy cm2, 9.55 exposures and 4.02 min, respectively) than for male residents (mean 41.7 Gy cm2, 8.26 exposures and 3.20 min, respectively). The number of lectures on radiation protection attended by the resident (range 0-20) had no significant effect on these radiation-related variables. Other factors explaining these variables were patient age, diagnosis and anteroposterior thickness. Radiologists' use of ionizing radiation during fluoroscopy may be sex-related. Traditional lecture-based education on radiation protection was not effective with this group; thus, improved methods should be developed to control doses.

Adult↗
PubMed2002

A practical demonstration of improved technique factors in paediatric fluoroscopy.

Dose incurred with fluoroscopic procedures accounts for a significant proportion of medically induced diagnostic exposure. Children are particularly vulnerable and it is therefore important to minimize exposure where practicable. A recent theoretical study has highlighted the potential for X-ray equipment to produce significant dose savings during paediatric fluoroscopy without incurring loss of diagnostic image quality. This is achieved by hardening the beam with additional copper (Cu) filtration (approximately 0.2 mm Cu) and biasing exposure factors towards low tube potential, high tube current output. In practice, this method will have limited applicability because the high powered and programmable generator characteristics required are not commonly available in installations used for paediatric imaging. However, we describe a simple experiment in which our clinical equipment was modified to approximate desired low dose performance by altering the filtration and automatic exposure control characteristics of ordinary clinical equipment in the Sheffield Children's Hospital. This enabled us to obtain significant savings in dose. We performed a comparative study (normal dose vs low dose) using water phantoms to simulate patient attenuation in the age range 0-15 years. The Leeds N2 contrast sensitivity phantom was used to provide a measure of image quality. Dosimetric measurements recorded up to 40% reduction in dose rate with only marginal loss of image quality when 0.1-0.2 mm Cu filtration was used with the modified settings. This is a strong indication that significant dose reduction is achievable on routine clinical equipment without compromising image quality. Such simple and cost effective methods of dose reduction should be considered for wider implementation.

Adolescent↗
PubMed2002

Does cardiologist- or radiographer-operated fluoroscopy and image acquisition influence optimization of patient radiation exposure during routine coronary angiography?

The operator of radiation exposure during coronary angiography varies between different centres. The purpose of this study was to explore whether radiation dose was lower during cardiologist- or radiographer-controlled radiation exposure and to determine if the grade of cardiologist performing angiography influenced radiation dose. Patients were randomly allocated either to cardiologist- or radiographer-controlled radiation exposure during coronary angiography. Screening time and radiation dose during fluoroscopy and image acquisition, measured by dose-area product meter, were recorded. Mean radiation dose during cardiologist-controlled radiation exposure (n=176) of 15.6 Gy cm(2) (95% confidence interval (CI), 14.4-16.8) was significantly lower than that produced by the radiographer-controlled group (n=192) of 17.3 Gy cm(2) (95% CI, 16.2-18.6) (p<0.044). There was no significant difference in screening times produced by the two groups of radiation exposure operators. The difference in radiation dose produced by the two operator groups was principally owing to exposure produced at image acquisition. Irrespective of radiation exposure operator, consultant cardiologists produced significantly lower screening times and radiation doses compared with registrars. During routine coronary angiography, radiographer-controlled radiation exposure does not reduce screening time or radiation dose. Senior cardiologists produce the lowest radiation doses during coronary angiography when they are responsible for radiation exposure.

Body Height↗
PubMed2003

Factors influencing fluoroscopy time and dose-area product values during ad hoc one-vessel percutaneous coronary angioplasty.

X-ray exposure during radiologically guided interventional procedures may have some deleterious effects. The aim of our study was to analyse the factors affecting patient dose during percutaneous coronary angioplasty (PTCA). We evaluated radiation dose during coronary angiography followed by one-vessel PTCA in 402 consecutive patients who were treated by three experienced physicians using both femoral and radial techniques. Fluoroscopy time (t) and patient dose measured by a dose-area product (DAP) meter were recorded. A good correlation was observed between t and the DAP (r=0.78, p<0.001). To assess the factors affecting radiation exposure, we studied the differences between operators, arterial catheterization access and stenting strategy. Median (25th to 75th percentiles) values for t were 19 (13 to 26) min and for DAP were 191 (145 to 256) Gy cm(2) for operator 3 compared with t=12 (9 to 18) min and DAP=137 (91 to 208) Gy cm(2) for operator 2 (p<0.005 versus operator 3) and t=13 (9 to 17) min, and DAP=134 (93 to 190) Gy cm(2) for operator 1 (p<0.001 versus operator 3). Differences between the radial and the femoral techniques were: t=17 (13 to 24) min versus 12 (8 to 17) min, (p<0.001) and DAP=175 (128 to 246) Gy cm(2) versus 138 (93 to 197) Gy cm(2), (p<0.001). In comparison with stenting without pre-dilation, direct stenting significantly reduced t and DAP [t=12 (9 to 16) min versus 16 (11 to 22) min, (p<0.001) and DAP=130 (95 to 186) Gy cm(2) versus 163 (119 to 230) Gy cm(2), respectively, (p<0.01)]. Radiation exposure to patients and staff are strongly dependent on operators, stenting strategy and the arterial access chosen for ad hoc one-vessel PTCA.

Aged↗
PubMed2006

A review of current local dose-area product levels for paediatric fluoroscopy in a tertiary referral centre compared with national standards. Why are they so different?

A prospective single centre study has been performed to assess dose-area product (DAP) values in children having fluoroscopic examinations and to revise local diagnostic reference levels (DRLs). DAP measurements for 2658 examinations performed in a dedicated fluoroscopy room over a period of 21 months were analysed. Data for the eight most commonly performed examinations (2215 cases) are presented. DAPs (75th centile) for upper gastrointestinal studies and micturating cystograms are substantially lower (by a factor of between x 5 and x 25) than the current national reference doses (NRDs), with some of the median values being 50 times lower. The small DAP values in all examinations demonstrate the substantial reduction in dose and consequent risk that can be achieved when both equipment performance and operator technique are optimized. Whilst we recognize that different institutions will have differing practices, it is important that practitioners are aware of the range of DAPs achievable and that NRDs do not necessarily represent best practice, and may falsely reassure.

Adolescent↗
PubMed2004

Optimization of variable temporal averaging in digital fluoroscopy.

In modern X-ray fluoroscopy systems, the amount of temporal averaging (i.e. persistence) applied to the image is often user selectable. The objective of this work is to quantify the effect of variable temporal averaging on the detection of low contrast test objects moving at a range of known speeds within the digital fluoroscopic image. An image intensifier system with a short-persistence television camera was used to record image sequences of a moving threshold contrast-detail diameter test object onto broadcast-standard U-matic videotape. The image sequences were replayed through an image processing system allowing different amounts of temporal averaging to be applied. The test images were scored by an experienced observer. The temporal averaging time constants produced by the added image processing were measured using a method based on noise correlation. Results are presented showing the trends of threshold contrast with test detail diameter and movement speed. The optimum value of temporal averaging time constant is presented as a function of detail diameter for a range of speeds. By comparison with the limited information available in the literature on organ movement, it is tentatively concluded that for the organ movement speeds expected in the abdomen, the optimum imaging system persistence time constant should be approximately 0.15 s. For the much greater speeds associated with cardiac motion no additional frame averaging, i.e. just the persistence provided by the observer's visual system, appears to be optimal.

Algorithms↗
PubMed2006

Six years experience in intracoronary brachytherapy procedures: patient doses from fluoroscopy.

Typical patient dose levels during intracoronary brachytherapy (ICB) procedures using beta sources were determined across a sample of 221 treatments. Dose-area product values, fluoroscopy time and number of frames per procedure, with median values of 62 Gy cm2, 17.0 min and 1493 images, respectively, resulted in a 20% to 50% increase in the values measured for percutaneous transluminal coronary angioplasty procedures in the same medical centre (median values 41 Gy cm2, 14.3 min and 1078 images). Likely reasons for this increase include the additional complexity of ICB, the need for recording and reporting every step of the treatment, getting the essential parameters for the volume determination of the lesion and therapeutic radiation dose calculation and, finally, the learning curve for this kind of procedure. A high concentration skin dose distribution during ICB procedures was measured and in 12% of the patients peak skin doses higher than 1.5 Gy were confirmed. 10 patients were submitted to clinical follow-up and skin injuries were not identified.

Angioplasty, Balloon, Coronary↗
PubMed2003

Comparison of canine heartworm removal rates using flexible alligator forceps guided by transesophageal echocardiography and fluoroscopy.

Fluoroscopy (FS)- or transesophageal echocardiography (TEE)-guided heartworm removal was carried out using flexible alligator forceps to compare the rate of worm removal. As a result, the worm removal rates were similar between the two procedures. However, the TEE-guided procedure does not involve radiation exposure, and facilitates observation of worms in the cardiac chamber and pulmonary artery. Therefore, the TEE-guided procedure is thought to be more useful than the FS-guided procedure in clinical setting.

Animals↗
PubMed1978

Sialography of salivary gland tumors with fluoroscopy and tomography.

Sialography with fluoroscopy and tomography has increased the accuracy of detecting and delineating mass lesions of the parotid gland. Lesions which are small, at the periphery of the gland, or in the deep lobe are often most clearly visualized on tomographic sections. Often differentiation of benign from malignant tumors is not possible.

Adenolymphoma↗