Image-intensified Fluoroscopy Research Articles

Effectiveness of Flat-Panel Fluoroscopy in Direct Anterior Total Hip Arthroplasty: A Comparison to Image Intensifier Fluoroscopy With Radiopaque Grid

IntroductionThe use of traditional, image intensifier fluoroscopy with a radiopaque grid during direct anterior total hip arthroplasty (DA THA) has demonstrated reduced variability in component positioning and operative time compared to fluoroscopy without a grid. A disadvantage of image intensifier fluoroscopy is spatial distortion, particularly compared to flat-panel fluoroscopy systems. The purpose of this study is to determine whether flat-panel fluoroscopy decreases variability in component positioning during DA THA compared to the use of traditional grid fluoroscopy. MethodsWe retrospectively reviewed 70 consecutive DA THAs between February 2020 and February 2021: 36 using flat-panel fluoroscopy, and 34 using traditional fluoroscopy with a grid. Radiographs were independently reviewed by 2 authors to identify components exceeding goal parameters: cup abduction of 40 ± 10 degrees, as well as offset and limb lengths within 10 mm of the contralateral side. Binary values for goal parameter achievement were assigned for each THA. ResultsNo significant difference was observed in the number of hips that met goals for cup abduction (100% vs 97%, P = 1.00), hip offset (88% vs 88%, P = 1.00), limb length (91% vs 94% [ ±10 mm], P = .669, 65% vs 72% [±5 mm], P = .498), or for the number of hips that met all 3 component goals (79% vs 80%, P = 1.00). No significant difference in operative time was noted between the 2 groups (110.2 minutes vs 100.9, P = .76). ConclusionsWe demonstrated no significant difference in component positioning in DA THAs utilizing flat-panel fluoroscopy as compared to using traditional fluoroscopy with a grid.

Are We Being Fooled by Fluoroscopy? Distortion May Affect Limb-Length Measurements in Direct Anterior Total Hip Arthroplasty

BackgroundDistortion is an intrinsic phenomenon associated with image-intensified fluoroscopy that is both poorly understood and infrequently appreciated by orthopedic surgeons. Little information exists regarding its potential influence on intraoperative parameters during orthopedic surgery, let alone during direct anterior (DA) total hip arthroplasty (THA). The purpose of this study was to quantify the amount of potential error caused by fluoroscopic distortion during DA THA. MethodsIntra-operative fluoroscopic pelvic images from 74 DA THAs were reviewed by two independent readers. All images were obtained using the same fluoroscopic C-arm unit with a radiopaque grid attached to the image intensifier. The vertical distortion from a straight central horizontal line at the peripheries of images were measured and summed to yield the combined vertical distortion similar to how a surgeon calculates a side to side comparison of limb lengths. Simple linear regression was used to evaluate associations between total distortion and patient demographics, operating theaters, and various operative parameters. ResultsThe average combined distortion was 10.0mm (range 2.0-20.0mm). There was a significant difference in the average distortion observed in different theaters (P < .001). There was no association between distortion and patient demographics or fluoroscopic time (all, P > .05). ConclusionFluoroscopic distortion is unpredictable and can cause a substantial amount of error when comparing limb lengths during DA THA. This is a critical finding as this amount of inaccuracy could lead to unintended implant positioning and limb-length discrepancies if unaccounted for.

Comparison of image quality and radiation dose between an image-intensifier system and a newer-generation flat-panel detector system — technical phantom measurements and evaluation of clinical imaging in children

Many image-intensifier fluoroscopy systems have been replaced by flat-panel detectors in recent years. To compare the level of contrast, image resolution and radiation dose between an image-intensifier and a newer-generation flat-panel detector system in a pediatric radiology unit. We compared two systems — a conventional image intensifier and a newer-generation flat-panel system. We measured image quality and radiation dose using a technical phantom. Additionally, we retrospectively compared age-matched fluoroscopic pediatric voiding cystourethrography (n = 15) and upper gastrointestinal investigations (n = 25). In phantom studies image contrast was equal while image resolution was higher and mean radiation dose lower using the flat-panel system (P < 0.0001). In pediatric investigations, mean dose area product was significantly reduced on the flat-panel system for upper gastrointestinal investigation (45 ± 38 μGy*m2 vs. 11 ± 9 μGy*m2; P < 0.0001) and for voiding cystourethrography (18 ± 20 μGy*m2 vs. 10 ± 12 μGy*m2; P = 0.04). The newer flat-panel system performs at lower dose levels with equal to better image quality and therefore seems to be the more suitable technique for pediatric fluoroscopy in comparison to image-intensifier systems.

A preliminary clinical evaluation of the “greater trochanter-head contact point” method for the intraoperative torsional control of femoral fractures

PurposeIn a previous study, our group introduced a simple non-invasive method for the intraoperative control of femoral torsion during closed nailing of femoral fractures using the shape of the greater trochanter and its relation to the femoral head. The aim of this study was to verify the results of our cadaveric study and transfer them into a clinical setup. We answered the questions: [1] How much time is needed to perform the greater trochanter-head contact point method (GT-HCP)? [2]. How long is the radiation time? MethodsWe examined 15 patients with femoral shaft fractures, to evaluate the GT-HCP method in a clinical setup. Using a standard fluoroscopic image intensifier (Ziehm, Erlangen, Germany), the greater trochanter-head contact angle was measured for both sides. All patients received a postoperative computer tomography (CT) to check the rotational malalignment. The mean of the CT results was then compared to the measurements of the GT-HCP method. The examiners performing the CT measurements were not aware of the GT-HCP results and vice versa. ResultsNo statistical significance could be detected between the CT and the GT-HCP method (p = 0.853). Eleven patients had very good results (≤5°), three had good results (6–10°) and one had poor results (>10°). The mean difference between CT and GT-HCP method was 3.7 ± 3.3°, which is acceptable. The radiation dose needed for the method was not large (0.2 ± 0.1 min), and could be lowered with the gaining experience of the examiners. Similarly, the overall time needed (12.1 ± 4.9 min) for the GT-HCP method could be reduced with the experience of the team. ConclusionOur study showed that the GT-HCP method is a precise and not particularly time consuming method for controlling anteversion during closed femoral nailing. Further clinical trials including a larger number of patients are required to establish this method in clinical practice.

Volar Plating for Distal Radius Fractures—Do Not Trust the Image Intensifier When Judging Distal Subchondral Screw Length

The use of the volar plate to treat distal radius fractures is increasing but despite the theoretical advantages of a volar approach there have been reports of extensor tendon ruptures due to prominent screw tips protruding past the dorsal cortex. The valley in the intermediate column between Lister tubercle and the sigmoid notch of the distal radius makes it difficult to rely on fluoroscopy to judge screw length. Our aim was to quantify the dimensions of this valley and to demonstrate the danger of relying on intraoperative image intensification fluoroscopy to determine lengths of distal screws. We measured the depth of this valley in the intermediate column of the distal radius in 33 patients with computed tomographic (9 patients) or magnetic resonance image (24 patients) scans of the wrist. There was a consistent valley in all images examined [average 1.8 mm (95% confidence interval, 1.6-2.0 mm)]. Thirty-nine percent of wrists had a valley depth of at least 2 mm. Standard lateral views or rotation of the forearm to obtain oblique views does not identify prominent screw tips; and whatever the rotation of the forearm, screw tips protruding beyond dorsal cortex may look as if it is within the bone when in fact it is out. When drilling we suggest noting the depth at which the drill bit just penetrates dorsal cortex and routinely downsize the distal screw length by 2 mm. We caution against relying on flourosocopy when judging the length of the distal subchondral screws.

Device setting modifications for 3D flatpanel imaging in skull base surgery

To evaluate the image quality and clinical implementation after setting modification of a three-dimensional isocentric C-arm fluoroscopic image intensifier system combined with a digital flatpanel detector as a new tool for sinus and petrous bone surgery. Image acquisition was performed using two cadaveric heads. Experimental design was oriented to the clinically sensible intraoperative setup. Different tube currents and orbital movements of the C-arm system were evaluated for image quality by three otolaryngological surgeons using predetermined landmarks. Modification of the X-ray intensity did not attain statistically significant values compared to the X-ray-intensity predetermined by producer (12.0-18.5 mA, p > 0.05) for either sinus or for petrous bone scans. Elliptical orbital movement resulted in significantly superior image quality than data sets acquired by circular orbital movement (3.194 vs. 2.809, p < 0.0001). New C-arm systems with 3D-capabiltity offer a promising tool for intraoperative near real-time image guidance. Image quality of the skull base can be improved significantly with optimized system settings.

AAPM/RSNA Physics Tutorial for Residents: Physics of Flat-Panel Fluoroscopy Systems

This article reviews the design and operation of both flat-panel detector (FPD) and image intensifier fluoroscopy systems. The different components of each imaging chain and their functions are explained and compared. FPD systems have multiple advantages such as a smaller size, extended dynamic range, no spatial distortion, and greater stability. However, FPD systems typically have the same spatial resolution for all fields of view (FOVs) and are prone to ghosting. Image intensifier systems have better spatial resolution with the use of smaller FOVs (magnification modes) and tend to be less expensive. However, the spatial resolution of image intensifier systems is limited by the television system to which they are coupled. Moreover, image intensifier systems are degraded by glare, vignetting, spatial distortions, and defocusing effects. FPD systems do not have these problems. Some recent innovations to fluoroscopy systems include automated filtration, pulsed fluoroscopy, automatic positioning, dose-area product meters, and improved automatic dose rate control programs. Operator-selectable features may affect both the patient radiation dose and image quality; these selectable features include dose level setting, the FOV employed, fluoroscopic pulse rates, geometric factors, display software settings, and methods to reduce the imaging time.

A simple technique for the placement of Schanz screws into bone using minimal radiologic control

The insertion of Schanz screws into the bone during external-fixation procedures in trauma and elective orthopaedic surgery is usually done under röentgenologic control. In order to minimize irradiation exposure for the patients, as well as surgeons, we describe a simple method of Schanz screw placement. The röentgenologic control of the position of the half-pins is only necessary at the beginning and the end of the procedure. This technique is simple, shortens the operating time and reduces the amount of radiation exposure to both the patient and surgeon. It is a valuable technique in many resource-poor environments who do not have the facilities for an image intensifier fluoroscopy or C-arm as well as in austere situations such as during military operations.

WE‐A‐210A‐01: Fluoroscopic Imaging Equipment: Guidelines for Detector Input Dose Settings and Image Optimization

Modern fluoroscopy imaging equipment is designed to simultaneously monitor x‐ray generator parameters, detector exposure rate, contrast‐to‐noise ratio, and x‐ray tube loading. Under programmed control, fluoroscopy systems automatically make adjustments to the parameters controlling x‐ray production, beam filtration, detector signal output, digital image processing, and image presentation. Any means intended to reduce patient dose should be implemented in a way that preserves image quality.For the clinical medical physicist, optimization of fluoroscopic equipment performance begins with an understanding of the variable system parameters, and the identification of the trigger points for changes in these parameters. Secondly, an understanding of how system parameters affect each other, affect image quality, and affect patient dose can lead to better choices in how the system should be set up for specific applications.A necessary requirement is an understanding of what detector input dose one should expect with an image intensifier fluoroscopy system, and how the detector dose should change when a flat panel detector is utilized. It is also necessary to understand how operational settings on the equipment can obviate superior detector performance as determined by detector type and metrics. This presentation will use imaging examples from installed systems to explore these issues. Also, a clear, concise guideline for determining the appropriate fluoroscopy detector input dose rate for both image intensifier and flat panel detectors will be presented.Learning Objectives:1. Provide an understanding of modern fluoroscopic imaging system component design and functionality2. Determine the appropriate fluoroscopy detector input dose rate for image intensifier and flat panel detectors3. Describe specific ways in which equipment settings can enhance or detract from optimum performance.

Assessment of performance of a new digital image intensifier fluoroscopy system

The aim of this study is to assess the physical properties of a recently installed digital fluoroscopy unit, Axiom Iconos R200 unit (Siemens, Germany), including image quality and patient dose. Image quality parameters and patient doses were measured at various fields of view (FOV) and frame rates. The entrance surface dose rate (ESDR) was measured using standard 30 x 30 cm2 polymethylmethacrylate (PMMA) phantom with different thicknesses. The ESDR was measured using a 20 cm PMMA and largest FOV ranged from 1.1 to 8.2 mGy min(-1) for different frame rates available. The low-contrast sensitivity varied from 1.8 to 6.6%, as the limiting spatial resolution changes from 1.25 to 2.24 ln mm(-1) for the different magnifications, frame rates and phantom thicknesses. This study shows the weak points of the standard quality control protocols. The additional image quality and dose assessments revealed the existing potential for optimisation of the system.

Laparoscopically Assisted Retrieval of Lost IUCD/Foreign Bodies

Migration of therapeutically implanted intrauterine contraceptive devices and foreign bodies pose challenges in accurate localization and removal through the least invasive method. Laparoscopic removal is the desired method of treatment due to the lessened surgical and anesthetic morbidity and accurate and rapid localization of the devices are imperative in aiding an endoscopic removal. Difficulties in locating the device leads to prolonged intraoperative times and at times culminate in a laparotomy with its attendant increased morbidity. We present a case series where rapid and accurate localization of the devices was achieved by intraoperative usage of the fluoroscopic image intensifier. The image intensifier can view images in real time and can be used intraoperatively, increasing the diagnostic accuracy. We propose that intraoperative imaging by the fluoroscopic image intensifier is a cost effective, rapid, and accurate method of localizing a migrated contraceptive device, thus enabling optimal endoscopic treatment.

Radiography and image-intensified fluoroscopy of barium passage through the gastrointestinal tract in six healthy Amazon parrots (Amazona aestiva).

Gastrointestinal contrast studies were performed in six clinically healthy blue-fronted Amazon parrots (Amazona aestiva) using radiography and image-intensified fluoroscopy. During examination, the birds were confined in a perspex cage. The quality of the lateral radiographs was adequate for assessment of the contrast medium-filled gastrointestinal tract. Thirty minutes after administration of 20 mL/kg of a 25% barium sulphate suspension directly in the crop, in all birds the ventriculus was totally outlined by barium. After 60 min, the small intestine was filled in five of six birds. After 180 min, the crop was empty in all birds. The barium-outlined ventriculus had differences in shape on radiographs of individual birds and also between birds. The colon and cloaca had further filling after 120 to 300 min. With image-intensified fluoroscopy, gastrointestinal motility was evaluated. Contractions of the crop were seen, and boluses of contrast medium passing through the esophagus toward the proventriculus were easily identified. Proventricular contractions were rarely noted, but ventriculus motility was present and clearly defined. The ventriculus had a mean of 3.7 contraction cycles/min. In the duodenum and small intestine, rapid antegrade and retrograde peristaltic movements in combination with segmental contractions were seen. In the colon, occasionally very slow peristaltic activity, mainly of segmental nature, was present. During the examinations, no defeacation was recorded. Confinement in a small perspex cage provides an adequate and handy radiological set-up for evaluation of gastrointestinal passage and motility in birds, minimizing the influences of stress and anesthesia.

整形外科手術における看護婦，麻酔科医の放射線被曝量についての検討

We report the radiation exposure dose received by the anesthesiologist and nurse in the orthopaedic operating room, when a fluoroscopic image intensifier is in use. This study was done in 12 femoral neck fracture operations performed from January to May 1995. Radiation was monitored with the MYDOSE MINIX PDM 107 made by Aloka Co. which were attached in front and behind the nurse's lead apron, in front of the lead apron of the anesthesiologist. The average imaging time was 9.78min. The average radiation dose in front of the anesthesiologist is lead apron was 2.08μ SV, and in front and behind the nurse's lead apron were 5.67μ SV, 0.08μ SV respectively. This study and review of the literature indicate that the operating room anesthesiologist and nurse receive a lower exposure than the orthopaedist. We can disregard the problem of radiation exposure to the anesthesiologist and nurse during an orthopaedic operation when they wear lead aprons and stand far from the patient.

Radiologic evaluation of the liver and gastrointestinal tract in rats infected with Taenia taeniaeformis

Summary In rats infected with the cestode Taenia taeniaeformis, hepatomegaly results from development of parasitic cysts in the liver. Diffuse nodular mucosal hyperplasia in the glandular region (corpus and antrum) of the stomach, and gross thickening of the intestinal mucosa also result. Between postinfection days (PID) 21 and 84, radiologic observations were made after oral administration of a barium sulfate suspension in T taeniaeformis-infected rats and in age/sex-matched controls. There was radiographic evidence of hepatic enlargement at PID 21. Enlargement of the gastric folds was first observed along the greater curvature of the stomach at PID 35. Fimbriation of small intestinal mucosal surfaces resulted from thickening of the intestinal villi and was observed in the duodenum at PID 21. Intestinal motility was assessed, and contractions were counted, using image intensification fluoroscopy, then were recorded on videotape. There were no significant differences between control and infected rats for gastric emptying time, intestinal transit time, and number of intestinal contractions per minute. Barium contrast radiography clearly indicated large gastric folds, thickening of the small intestinal villi, and hepatic enlargement, and was useful for assessing gastrointestinal motility.

CT-fluoroscopy link-up (CTF): potential for special procedures

Some interventional radiological procedures call for unrestricted axial vision and monoplanar fluoroscopy at different angles. We have mounted a fluoroscopic image intensifier in front of the gantry of a CT scanner to assess whether the combination would be useful. This link-up has been tested in a variety of situations and, even with the shortcomings of makeshift equipment, the combination filled some gaps in our vision of what is going on inside the patient, especially before an invasive procedure. It also proved useful in the planning of multiple procedures in a single session, especially when they had to be performed under general anesthesia in children or in the management of critical cases. We feel that the possibilities afforded by CTF (computed tomography plus fluoroscopy) need further exploration prior to the construction of purpose-built equipment. The interim information supplied suggests that it will be worth developing.

Book reviewsMeasurement of the Performance Characteristics of Diagnostic X-Ray Systems used in Medicine. Part VI. Image Intensifier Fluorography Systems. HPA report TGR32. pp. 20, 1984 (Hospital Physicists' Association, London), £6.00. ISBN 0–904181–30–8

The subject of this report is image intensifier fluorography in its various formats, which is probably a less well known subject than image intensifier fluoroscopy. If this is true then it follows that there is a need for good information both to educate and to standardise work in the field.

Computerized fluoroscopy: New technique for the noninvasive evaluation of the aorta, coronary artery bypass grafts, and left ventricular function

A computerized fluoroscopy system has been developed on the basis of real-time digital processing of x-ray transmission data from traditional image-intensified fluoroscopy equipment. High-quality visualization of any part of the arterial system is obtained following intravenous injection of 0.5 to 0.75 ml/kg of iodinated contrast materials. This report describes the use of this technique to evaluate the aortic arch, left ventricular function, and coronary artery bypass graft patency. Fifty intravenous studies were performed in 25 patients. Among 20 patients with coronary artery bypass grafts, computerized fluoroscopy correctly identified 11 of 15 patent grafts and 11 of 11 occluded grafts as confirmed by standard coronary arteriography in 11 of these patients. Unlike computerized tomography, our technique gives a longitudinal view of the bypass graft much like direct coronary angiography. Aortic arch studies included demonstration of a right aortic arch with a small left subclavian artery, a coarctation, and a normal aortic arch in a trauma patient with a wide mediastinum. Segmental wall motion abnormalities were clearly identified by a modification of the technique which produces a negative outline on the ventriculogram in dyskinetic segments. Ejection fractions may be calculated by determining the amount of iodine in the ventricle in systole and diastole. This technique may also be used to evaluate carotid disease and peripheral vascular disease in patients undergoing coronary artery bypass procedures. Computerized fluoroscopy, therefore, allows evaluation of the entire cardiovascular system by the relatively noninvasive technique of intravenous angiography.

Intrajejunal absorption of liposomally entrapped insulin in normal man [proceedings

Since the discovery of insulin, many investigators have explored the possibility of developing a n effective method for its oral administration. Attempts t o secure absorption of insulin from the gastrointestinal tract using adjuvants have been unsuccessful from a therapeutic point of view, but it has become generally accepted that insulin can be absorbed from the intestine of mammals and some hypoglycaemic activity of the absorbed insulin observed (Laskowski et al., 1959; Inouye & Mars, 1962; Speth & Christian, 1963; Engel et al., 1968; Galloway & Root, 1972). Patel & Ryman (1976, 1977) and Dapergolas et al. (1976) have demonstrated that liposomally entrapped insulin, when given orally, produces hypoglycaemia in both diabetic and normal rats. Thus liposomes not only seem t o protect insulin from proteolytic degradation in the stomach and intestine, but also act as structurally organized vehicles with endocrine therapeutic potential. This has led us t o investigate whether absorption of liposomally entrapped insulin occurs in the intestine of normal man. Liposomes containing insulin were prepared by the method of Patel & Ryman (1976) with the following modifications. Neutral liposomes were prepared by dissolving egg phosphatidylcholine/cholesteroI (1 : 5, w/w) in chloroform. To the dry lipid was added a mixture of crystalline ox insulin (2mg/ml) and bovine serum albumin (1 mgiml), prepared in 10mM-potassium phosphate containing 80m~-NaC1, p H 7.4 (phosphate/saline buffer). Liposomes thus formed were sonicated for 8 min, with cooling, a t 4°C using a 19mm titanium probe at 0.15nm in an MSE 150W sonicator. The sonicated liposomes were passed through a Sepharose 6B column, equilibrated with the phosphate/saline buffer, and the lipid fractions with insulin associated were collected and stored under N2 at 4°C. Preparations were transported from London t o Glasgow by rail and were received on the day of preparation and used shortly afterwards. For this pilot study, volunteers were healthy male medical graduates, who acted as their own controls. Liposomally entrapped insulin (20-200 units) a t body temperature were administered quickly into the jejunum by syringe through a radio-opaque tube 1.5mm in diameter. This tube was taken orally, retained by a small mercury-filled terminal balloon and located in the jejunum by image-intensified fluoroscopy. Each intubation was performed between 08:30 and 09:30h, the subject having fasted for 10h previously. Samples of venous blood were withdrawn and collected in lithium-heparin tubes. Blood glucose was assayed by the glucose oxidase method, and plasma insulin by immunoassay using Wellcome reagents. In the first subject 22 units of liposomally entrapped insulin were administered intrajejunally and there appeared to be a small but progressive rise in concentration of plasma immunoreactive insulin, but no significant change in blood glucose concentration. The following five subjects were given up to 200 units of liposomallyentrapped insulin. Again a small increase in the concentration of plasma immunoreactive insulin was observed, but generally insignificant changes were seen in blood glucose concentration. Control liposomes (without insulin) had no effect upon the concentration of either plasma immunoreactive insulin or of blood glucose. We have estimated that about 1 of the administered dose of insulin appears in the plasma by 60min in our normal subjects. This study used a range of insulin doses known to be effective parenterally and has not yielded overt clinical hypoglycaemia. Nevertheless, indications are that insulin is taken up by normal males from the liposomal complexes, but presently acts a t too

A roentgenographic method for measuring nasal mucous velocity.

Nasal mucous velocity was estimated by following the motion of radiopaque discs of Teflon by means of a fluoroscopic image intensifier. From 5 to 10 discs were deposited on the superior surface of the inferior turbinate with a forceps. No local anesthesia was employed and the subjects experienced no discomfort. The linear velocity of the discs was obtained by playing the videotape onto a television monitor, measuring distance with a ruler, and dividing by elapsed time. Duplicate runs of 1-2 min, 15 min apart were very reproducible but runs at 4-h intervals or daily over a 5-day period had a coefficient of variation of 30%. Average nasal velocity for individual ranged from 0 to 22.5 mm/min and group means ranged from 6. 8 to 10.8 mm/min. There was no statistically significant difference in nasal mucous velocity between young and elderly subjects nor was there a sexual difference. The saccharin test of nasal mucous transport was unsatisfactory because of inability to repeat the test more often than 1-2 h and its propensity to produce mild discomfort in a significant number of subjects. Saccharin times did not correlate significantly with values of nasal mucous velocity.

A new roentgenographic method for estimating mucous velocity in airways.

A new roentgenographic method is described for the estimation of mucous velocity in airways. Radiopaque discs of teflon mixed with bismuth trioxide were deposited in the trachea, and their motion was observed by a fluoroscopic image intensifier. Simultaneous measurements of disc movement were obtained by a previously reported cinebronchofiberscopic method and by the roentgenographic method in 6 anesthetized dogs. Mean +/- SD tracheal mucous velocity was 8.5 +/- 7.3 mm per min by the roentgenographic method, and 7.6 +/- 7.1 mm per min by the cinebronchofiberscopic method. Discrepancies between the 2 methods for individual disc velocities could be accounted for by the cumulative errors of both methods. The roentgenographic method was also used in 7 normal volunteers who did not have topical anesthesia of the tracheobronchial tree. The discs were blown through the inner channel of a bronchofiberscope, the tip of which was located just above the vocal cords. Placement of the discs on the tracheal mucosa generally did not produce coughing. Tracheal mucous velocity ranged from 7.4 to 19.4 mm per min as estimated from videotape recordings of the image intensifier images. There was no consistent difference in velocity between the erect or supine position, or after topical anesthesia with lidocaine.