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We conducted a preliminary evaluation of a digital fluoroscopy system for general applications, including gastrointestinal imaging, venography, myelography, and genitourinary fluoroscopy. We describe the system, present examples of images obtained in a variety of applications, and assess the performance of the system.
Since 1992, the U.S. Food and Drug Administration (FDA) has received reports of radiation-induced injuries to the skin in patients who had undergone fluoroscopically guided interventional procedures. The reports were investigated to determine the procedure- or equipment-related factors that may have contributed to the injury. The injuries ranged in severity from erythema to moist desquamation to tissue necrosis that required skin grafting. They occurred after a variety of interventional procedures that required extended periods of fluoroscopy compared with those of typical diagnostic procedures. Medical facilities and physicians should be aware of the magnitude of radiation doses to the skin that can result from the long exposure times required by complex interventional procedures. The FDA recommends several steps for reducing these injuries, including establishing protocols for each procedure, determining radiation dose rates for specific fluoroscopy systems and operating modes, and monitoring cumulative absorbed doses to areas of the skin.
A digital fluoroscopy system is most commonly configured as a conventional fluoroscopy system (tube, table, image intensifier, video system) in which the analog video signal is converted to and stored as digital data. Other methods of acquiring the digital data (eg, digital or charge-coupled device video and flat-panel detectors) will become more prevalent in the future. Fundamental concepts related to digital imaging in general include binary numbers, pixels, and gray levels. Digital image data allow the convenient use of several image processing techniques including last image hold, gray-scale processing, temporal frame averaging, and edge enhancement. Real-time subtraction of digital fluoroscopic images after injection of contrast material has led to widespread use of digital subtraction angiography (DSA). Additional image processing techniques used with DSA include road mapping, image fade, mask pixel shift, frame summation, and vessel size measurement. Peripheral angiography performed with an automatic moving table allows imaging of the peripheral vasculature with a single contrast material injection.
Fluoroscopic procedures (particularly prolonged interventional procedures) may involve high patient radiation doses. The radiation dose depends on the type of examination, the patient size, the equipment, the technique, and many other factors. The performance of the fluoroscopy system with respect to radiation dose is best characterized by the receptor entrance exposure and skin entrance exposure rates, which should be assessed at regular intervals. Management of patient exposure involves not only measurement of these rates but also clinical monitoring of patient doses. Direct monitoring of patient skin doses during procedures is highly desirable, but current methods still have serious limitations. Skin doses may be reduced by using intermittent exposures, grid removal, last image hold, dose spreading, beam filtration, pulsed fluoroscopy, and other dose reduction techniques. Proper training of fluoroscopic operators, understanding the factors that influence radiation dose, and use of various dose reduction techniques may allow effective management of patient dose.
The purpose of this study was to evaluate the feasibility of using an open-configuration magnetic resonance (MR) imaging system with MR fluoroscopic guidance to perform percutaneous transthoracic fine-needle aspiration biopsy in patients with lung masses. Percutaneous transthoracic aspiration biopsies were performed with MR fluoroscopic guidance in 14 patients. The masses were 2-7 cm in diameter (mean, 4.1 cm). The needle was positioned by using a free-hand technique with MR fluoroscopic guidance. The needle tip reached the target lesion, and biopsy was performed. Analysis of the biopsy specimens facilitated a specific diagnosis in all patients. Pneumothorax was noted in two patients (14%) with chronic obstructive pulmonary disease. Study results showed that the described MR fluoroscopy-guided transthoracic biopsy technique can be used safely and successfully for lung masses. MR fluoroscopy can be used to reach the target lesion easily and accurately.
A bellows-based breath-hold monitoring and feedback system was developed and evaluated for use in intermittent-mode computed tomographic (CT) fluoroscopy-guided biopsy procedures in the lung or upper abdomen. The bellows system is described, and its feasibility is demonstrated in studies with a respiratory phantom and human volunteers. Results are reported for seven patients who underwent bellows-assisted biopsy. Breath-hold monitoring and feedback with the bellows system allow the patient to perform reliable breath holding at a preselected level. This optimizes intermittent-mode CT fluoroscopy-guided biopsies by allowing consistent visualization of the target lesion throughout the procedure.
A method for lower-extremity venography using remote-control fluoroscopy and radiography, as well as pressure infusion of contrast media, is described. This technique combines the advantages of fluoroscopically-timed and positioned radiographs with the improved image and size of overhead views. There is less radiation exposure to the patient, radiologist, and technologist than with venography performed with conventional fluoroscopy.
The usefulness of full-size radiographs obtained with the overhead tube following fluoroscopy was evaluated based on an analysis of 306 biphasic upper gastrointestinal studies that included follow-up postfluoroscopy views. In 32 studies with abnormal findings, the postfluoroscopy images were normal. In one case, the postfluoroscopy images revealed an abnormality not seen on spot views. The confidence levels rose in only 19 cases (6.2%) when postfluoroscopy images were used. In the appropriate setting, routine postfluoroscopy views after an upper gastrointestinal series are of little value. Nonetheless, in a teaching hospital, these images should be obtained when fluoroscopy is performed by junior residents.
Stimulation of the phrenic nerve by applying an electrical impulse to the neck during fluoroscopy or real-time ultrasound (sonoscopy) of the diaphragm allows more precise functional evaluation than fluoroscopy and/or sonoscopy alone. This is especially true of patients who are unable to cooperate because they are on a ventilator, unconscious, or very young. The authors cite cases in which diaphragmatic paralysis was diagnosed by conventional methods but stimulation of the phrenic nerve demonstrated good diaphragmatic motion, leading to a change in prognosis in some cases and a change in therapy in others.
Synchronous video tape fluoroscopy and manometry of the esophagus was performed in 11 subjects (seven men and four women; mean age, 49 years). Four had normal and seven had abnormal esophageal motility (diffuse esophageal spasm, n = 4; nonspecific esophageal motility disorder, n = 3) that was shown by previous manometry. A digital timer appeared on the video tape recording and marked the manometric tracing synchronously. Alternate 5-mL and 10-mL barium boluses were recorded for a total of 10 swallows per patient. Video tape examinations were reviewed prospectively, and the status of primary peristalsis and presence and severity of tertiary activity were noted. A total of 98 swallows (58 normal, 40 abnormal) were correlated, and a 96% agreement was found in assessing primary peristalsis. Overall results of fluoroscopic examinations of each subject during all swallows showed complete agreement with those of manometry; segregating the swallows into groups of five showed 92% concordance. Severe tertiary activity was invariably seen with abnormal primary peristalsis at fluoroscopy.
A method was developed to estimate tissue doses from the upper gastrointestinal fluoroscopy examination. It involved measuring the technical parameters of the clinical examination, partitioning the dynamic examination into a set of discrete x-ray fields, and generating corresponding tissue does tables with an existing computer program. Knowledge of the radiation exposures associated with each of the fields enabled the calculation of tissue doses for the entire dynamic examination. In this limited sample (eight patients), fluoroscopy times ranged from 108 to 183 seconds. Radiation exposures ranged from 2.3 to 7.2 mC/kg (9.1-28 R), thyroid doses from 0.15 to 3.5 mGy (15-350 mrad), uterine doses from 0.16 to 1.0 mGy (16-100 mrad), lung doses from 0.90 to 4.2 mGy (90-420 mrad), and active bone marrow doses from 0.81 to 5.4 mGy (81-540 mrad).
A recently developed real-time computed tomography (CT) fluoroscopy system, which provides effective real-time reconstruction and display of CT images, was used to monitor nonvascular interventional procedures performed in 57 patients. Biopsy of thoracic lesions (n = 38), biopsy or drainage of pelvic lesions (n = 6), drainage or aspiration of intracranial hematomas (n = 9), and other procedures (n = 4) were performed. CT fluoroscopy successfully depicted the entire procedure in all patients. In thoracic lesions, a mean 1.3 passes was necessary to gain access to the lesion. Sufficient cytologic samples were obtained in 32 of 33 pulmonary lesions with a mean diameter of 26 mm.
The radiation dose to physicians' hands without and with use of needle holders was determined at 10 computed tomography (CT) fluoroscopy-guided transthoracic needle biopsies. As measured with ionization chambers (tube voltage, 80 kVp; tube current, 30 mA), the mean absorbed dose rate without and with holders was 1.14 mGy/sec +/- 0.02 (standard deviation) and 0.019 mGy/sec +/- 0.001, respectively. The mean duration of CT fluoroscopy was 59 seconds in 10 biopsies performed with a holder and 82 seconds in 10 biopsies performed without a holder (difference not statistically significant). The needle holders did not cause any artifacts that interfered with the biopsy procedure.
PURPOSE: To determine the average abdominal entrance air kerma, low-contrast sensitivity, and spatial resolution in upper gastrointestinal tract fluoroscopy in the United States. MATERIALS AND METHODS: A random sample of fluoroscopic facilities was selected to be surveyed for the Nationwide Evaluation of X-ray Trends program. Measurements were performed by using a newly developed fluoroscopic phantom. The surveys were conducted by state radiation control personnel. RESULTS: Average air kerma rates 1 cm above the tabletop, free in air, were 43 mGy/min (n = 340). The rate increased to 64 mGy/min when a 1.6-mm-thick copper filter, which simulated the use of barium contrast medium, was added to increase attenuation. The average entrance air kerma, free in air, for radiographs was 3.4 mGy, and an average of 12 radiographs were obtained per examination. Of 352 facilities surveyed, 306 (87%) were able to resolve wire mesh with 20 or more lines per inch. Of 339 facilities for which percentage contrast could be calculated, 192 (57%) had minimum percentage contrast values of 4% or more. CONCLUSION: Spatial resolution for fluoroscopy is adequate for most of the facilities surveyed, but a substantial proportion of facilities could not visualize low-contrast test objects, which strongly suggests image quality problems.
PURPOSE: To estimate patient dose and personnel exposure from phantom measurements during computed tomographic (CT) fluoroscopy, to use the estimates to provide users with dose information, and to recommend methods to reduce exposure. MATERIALS AND METHODS: Surface dose was estimated on a CT dosimetric phantom by using thermoluminescent dosimetric (TLD) and CT pencil chamber measurements. Scatter exposure was estimated from scattered radiation measured at distances of 10 cm to 1 m from the phantom. Scatter exposures measured with and without placement of a lead drape on the phantom surface adjacent to the scanning plane were compared. RESULTS: Phantom surface dose rates ranged from 2.3 to 10. 4 mGy/sec. Scattered exposure rates for a commonly used CT fluoroscopic technique (120 kVp, 50 mA, 10-mm section thickness) were 27 and 1.2 microGy/sec at 10 cm and 1 m, respectively, from the phantom. Lead drapes reduced the scattered exposure by approximately 71% and 14% at distances of 10 and 60 cm from the scanning plane, respectively. CONCLUSION: High exposures to patients and personnel may occur during CT fluoroscopy-guided interventions. Radiation exposure to patients and personnel may be reduced by modifying CT scanning techniques and by limiting fluoroscopic time. In addition, scatter exposure to personnel may be substantially reduced by placing a lead drape adjacent to the scanning plane.
A method has been developed for the measurement of lung water dynamics and regional aeration of the lung in anesthetized newborn lambs by use of X-ray fluoroscopy, video recording, and digital image processing. After cesarean section and before the first breath fetal lambs under halothane-oxygen were placed on an X-ray table and connected to a volume-cycled respirator. X-ray fluoroscopy commenced before the initiation of respiration, and the images were recorded on video tape. X-ray transmission through the thorax increased as the lung was aerated. The enhanced transmission was compared with the values obtained from a calibration water wedge from which an equivalent path length through water can be estimated. In testing this method, it was demonstrated that X-ray transmission was linearly related to the wet lung weight-to-body weight ratio and to the product of the wet-to-dry weight ratio multiplied by anatomic thickness of frozen lung blocks. Calibrated values were also linearly related to this product and to the actual measured height of the fluid and tissue in the fluid-filled lung.
The management of children with upper airway obstruction (UAO) in whom previous airway surgeries or concomitant craniofacial or neuromuscular abnormalities exist is complicated by potential obstruction at multiple sites. Sleep fluoroscopy (SF) provides a dynamic representation of relative degrees of obstruction at multiple levels of the pediatric airway. Fifty-five SF studies were performed on 50 infants and children to localize obstructive sites. Correlation was assessed with findings on direct laryngoscopy and bronchoscopy under spontaneous ventilation. In 24 (44%), endoscopic and SF findings correlated exactly. The SF studies identified a site of UAO in 11 patients with normal findings on endoscopic examination and multiple sites of UAO in 16 others. Two thirds of these occurred at the hypopharynx and tongue base. The SF studies failed to detect 5 airway abnormalities in 4 patients. The sensitivity of SF for endoscopically verified laryngotracheal lesions was lowest for glottic (67%) and subglottic (70%) locations and higher for tracheal (92%) and supraglottic (100%) sites. Sleep fluoroscopy altered the course of treatment in 26 (52%) children. It appears to be a valuable adjunct to endoscopy in the identification and management of pediatric UAO when hypopharyngeal collapse or multiple levels of obstruction are suspected.
Fluoroscopy for determination of femoral neck anteversion was evaluated in 24 patients (48 hips) aged 5 to 15 years. The measurements of the anteversion angle of the femoral neck obtained by the fluoroscopic method were compared with those determined by the biplanar method of Dunlap/Rippstein. It is concluded that fluoroscopy incorporates errors to such a degree that the method is not reliable for clinical work.