PubMed Health⌕ Search

Biomedical subjects

D R Bednarek

Publications and source records attributed to D R Bednarek.

At least 19 recordsLinked to original sources
PubMed1997

Automatic system for measuring dose-area product (DAP) in ROI fluoroscopy.

A computerized system for monitoring dose-area product (DAP) has been developed for region of interest (ROI) fluoroscopy in which patient exposure is reduced using an x-ray attenuating filter with an aperture. The system includes an IBM compatible computer which is connected through an IEEE-488 interface to an electrometer which measures the charge from a DAP ionization chamber. A digital input/output board connects the computer to the filter placement device to determine whether the filter is in or out of the beam, and to the x-ray generator to determine when the exposure is due to spot filming. The computer logs the DAP from conventional fluoroscopy, ROI fluoroscopy and spot filming separately, applying the appropriate calibration factor for each. Measured DAPs, fluoroscopic DAP rates and exposure times are displayed in real-time. The system has been installed in a GI fluoroscopic room so that the dose-reduction potential of ROI imaging can be evaluated.

Automation↗
PubMed1997

Primary beam exposure outside the fluoroscopic field of view.

Fluoroscopic units can irradiate an area outside the displayed field of view (FOV) which provides no additional information to the fluoroscopist and may significantly increase the integral dose to the patient. This unnecessary exposure can be reduced using region of interest (ROI) filtration techniques to attenuate the x rays peripheral to the ROI as well as outside the displayed FOV [Granger et al., Med. Phys. 23, 1059 (1996)]. A survey was conducted to quantitatively determine the deviation between the total exposed area and the displayed FOV on 18 fluoroscopic x-ray units which have different shaped collimation. A film was taken in fluoroscopic mode and the area of the FOV was determined from the image of markers placed at the edge of the displayed FOV. For each unit, a measurement was made for each magnification mode at various source to image distances. The measured difference between the total exposed area and the area of the displayed FOV ranged between 5% and 32% for units meeting federal compliance standards and between 22% and 48% for units which were found to be out of compliance. The results of the survey and the application of ROI imaging techniques as a possible method to reduce dose due to inexact fluoroscopic collimation are presented.

Evaluation Studies as Topic↗
PubMed1996

Clinical application of region-of-interest techniques to radiologic imaging.

In region-of-interest (ROI) imaging, a filter with a central aperture is used to substantially reduce patient dose outside of an ROI while maintaining or improving image quality within the ROI. The benefits of ROI imaging can be realized by using standard imaging equipment. ROI imaging has been clinically applied to gastrointestinal radiology and interventional procedures. In gastrointestinal procedures, ROI fluoroscopy without image processing can be used without adversely affecting the procedure or interfering with spot radiography. ROI fluoroscopy can reduce the dose-area product by a factor of 1.7 for gastrointestinal procedures. In interventional neuroradiologic procedures, equalized display brightness is achieved with road mapping during fluoroscopy and with standard digital subtraction techniques during angiography. In interventional radiology, ROI filters can generally reduce the patient skin dose to levels below the threshold for skin effects, thus eliminating these effects across more than 85% of the field of view.

Central Nervous System↗
PubMed1996

Application of region-of-interest imaging techniques to neurointerventional radiology.

To reduce radiation exposure to patients and staff during neurointerventional procedures, region-of-interest (ROI) techniques were used with fluoroscopy, road mapping, and digital subtraction angiography in 19 patients. ROI filters, made of multiple layers of gadolinium, were attached to the collimators. Patient skin exposure was reduced by a factor of 3.3-10.0 across 85% of the field of view, and exposures were reduced to below thresholds for skin effects.

Angiography, Digital Subtraction↗
PubMed1996

Increasing the utility of the mammographic phantom image.

To increase the utility of the monthly accreditation mammographic phantom image, the authors added a light sensitometric strip on the same film. The optical densities of the steps on the sensitometric strip with values nearest those of the phantom background and disk were measured, and these optical densities and the density difference were recorded and plotted on a control chart. The ability was increased to determine if changes in the contrast or optical density on an image were due to film and associated processing or to the x-ray source.

Mammography↗
PubMed1995

Implementation of region-of-interest fluoroscopy by using the road mapping mode of a real-time digital radiographic unit.

In region-of-interest (ROI) fluoroscopy, a filter is used to greatly attenuate the x-ray beam outside the ROI and digital image processing is used to equalize the displayed brightness. The method is applicable to real-time imaging procedures such as vascular interventions for which a high-quality image is essential only over an ROI (eg, near the catheter tip), whereas the noise-degraded periphery may be acceptable for visualizing landmarks. Use of ROI fluoroscopy can greatly reduce radiation exposure to the patient and to staff while image quality in the ROI is maintained or improved. Exposure reduction factors greater than 5 were demonstrated for coil placement in a canine aneurysm model by using standard digital angiographic equipment operating in the road mapping mode. Potential applications for which future work will determine the clinical acceptability of ROI fluoroscopy include many of the highest-dose interventional procedures, in addition to general gastrointestinal fluoroscopy.

Animals↗
PubMed1992

Minimizing radiation dose to patient and staff during fluoroscopic, nasoenteral tube insertions.

It is possible to reduce greatly fluoroscopic radiation dose if some image degradation is acceptable. Since the fluoroscopic image during nasoenteral tube placements is used for guidance and not for diagnosis, a lower contrast image with increased quantum mottle can be easily tolerated. The three methods to reduce the radiation dose rate that were investigated consisted of removing the antiscatter grid, increasing the diameter of the optical aperture controlling the percentage of light reaching the television camera from the image intensifier output phosphor, and setting the fluoroscopic mA to the minimum value so that the kVp could be maximized. Fluoroscopic frozen video frames of a clinical tube insertion comparing the images with and without the dose-saving techniques are presented. Measurements of the radiation dose rates using a Plexiglas phantom show that the dose for patient and staff during fluoroscopic-guided nasoenteral tube placements can be reduced by over a factor of 10 without significantly adversely affecting the actual placement procedure.

Adult↗
PubMed1991

Blurred-mask density compression for improved reproduction of radiographs.

A film-based, blurred-mask subtraction technique can be used to reduce the apparent density range of medical radiographs so that a wider range of actual densities can be captured with video digitizers or reproduced on photographic paper for publication. The density compression and the edge enhancement resulting from this process is examined. A good balance between compression and enhancement for small structures was obtained with a 6-mm gap between the subtraction film and the original when producing the mask. As an example, a photographic print of a compressed chest film showed significant condensation of image information within the restricted reflection density scale of the print paper; detail was well demonstrated in the mediastinal, retrocardiac, and subdiaphragmatic regions that was not shown in the noncompressed print.

Humans↗
PubMed1991

Dose reduction during fluoroscopic placement of feeding tubes.

By both increasing the optical iris of the video camera and removing the grid in fluoroscopic procedures involved in placement of a Dubbhoff feeding tube, the radiation dose to patients and staff was reduced by five to seven times. An average expected dose to a patient of about 300 mGy per procedure was reduced by two to three times when the grid was removed and by an additional three times when an iris of increased diameter was used. Because Dobbhoff procedures do not involve obtaining a diagnosis, the image degradation was acceptable and did not affect the total exposure times or ability to conduct the procedure. With the grid out, the difference between the mean exposure times of 5.1 minutes in 96 patient studies done with a normal iris opening and 4.0 minutes in 52 studies done with an enlarged iris was not statistically significant. The importance of reducing patient dose is reinforced by the finding that one-third of the patients underwent repeated procedures, accounting for almost 60% of the total.

Environmental Exposure↗
PubMed1983

Artifacts produced by moving grids.

Anti-scatter grids reduce the amount of secondary radiation contributing to the image and improve the signal-to-noise ratio. However, they may also lead to the creation of linear artifacts representing the shadows of the radiopaque septa. Grid motion perpendicular to the septa during the exposure can cause blurring of the artifacts; however, the wider septa of recently proposed grids increase the difficulty of suppressing the artifacts entirely. Physical characteristics which affect perceptibility of grid-line artifacts and the conditions needed for their elimination are analyzed. Sufficient grid movement can eliminate overlap artifacts, while synchronization of linear grid motion with exposure time can suppress artifacts for relatively small grid movements.

Technology, Radiologic↗
PubMed1983

Reduction of fluoroscopic exposure for the air-contrast barium enema.

In a fluoroscopic imaging system, image quality and patient dose are both affected by the optical system linking the image intensifier with the video camera. The effect on patient exposure of increasing the optical iris aperture size over that required for other procedures performed on the same imaging system was investigated for the air-contrast barium enema examination. Using a large-area transmission ionisation chamber to monitor the Roentgen-area-product of entrance exposure, a decrease in fluoroscopic radiation of greater than 50% was clinically documented for a fluoroscopic system utilising kVp and mA variable automatic brightness control. For this iris change, the video image was of acceptable quality for positioning and monitoring the patient, and no deleterious effect was detected in the conduct of the air-contrast exam. The availability of a variable-sized operator-selectable iris diaphragm would permit this dose-reduction approach to be extended to other fluoroscopic procedures.

Air↗
PubMed1981

Computed tomography of the orbit.

In less than a decade computed tomography (CT scanning) had a profound impact on diagnostic radiology. Radiology of the orbit is no exception. As early as 1973, reports published in the radiological literature indicated that this new noninvasive imaging method was a highly effective way of demonstrating intraorbital mass lesions. As CT scanners became widely available, computed tomography became a significant adjunct to ophthalmological diagnosis. Today the main indications for CT scanning of the orbit are (1) suspected mass lesions, most frequently presenting as exophthalmos, (2) orbital trauma, including foreign bodies, (3) some congenital anomalies, and (4) suspicion of extension into the orbit of extraorbital disease processes. Along with ultrasonography, another new noninvasive imaging technique, CT has replaced a number of more invasive and often less effective diagnostic methods, such as orbital pneumography, venography, and arteriography as major imaging techniques in orbital pathology. The paper discusses current practices in the technique of CT scanning of the orbit including the important aspect of radiation dosimetry and the clinical applications, using a number of cases to illustrate its use.

Eye Foreign Bodies↗
PubMed1980

Improved contrast in special procedures using a rotating aperture wheel (RAW) device.

A new scatter control technology consisting of multiple rotating aperture wheels (RAWs) is being developed to provide improved radiographic contrast and/or reduced patient dose in both single frame and dynamic procedures. The unique geometry of this system allows the conventional source-patient-image receptor geometric relationship to remain unchanged so that the device can be added to existing radiographic, fluoroscopic, and conventional tomographic installations. A prototype RAW device has been used with a rapid film changer for simulated abdominal angiography. The resulting images show improved contrast over those obtained with a standard 12:1 fixed grid.

Angiography↗
PubMedDate not supplied

Method for image equalization of ROI fluoroscopic images using mask localization, selection and subtraction.

In region of interest (ROI) fluoroscopy, a filter is used to drastically reduce the X-ray dose to the patient peripheral to an ROI, and mask subtraction is used to equalize the displayed image brightness. Methods are described for an optimized search to locate the ROI and select or construct a mask image using a descriptor look up table (DLUT) based on ROI size, relative ROI/periphery brightness and ROI shape and orientation. After mask subtraction, the brightness values of the periphery are comparable to those of the ROI providing for equalized display. This method was tested successfully on 50 actual fluoroscopic images of two anthromorphic phantoms. The methodology developed for real-time applications was successfully simulated in PC code and full real-time implementation is underway.

Calibration↗
PubMedDate not supplied

Assessment of patient exposure for barium enema examinations.

Methods are described for the assessment of patient exposure during clinical fluoroscopic procedures. Values of the roentgen-area-product (RAP) and their distribution throughout the examination are presented for both single-contrast and double-contrast barium enema studies. The double-contrast procedure was measured to give 50% more radiation to the patient than the single-contrast procedure when the same size optical aperture is used between the intensifier and TV pick-up tube. However, it was possible to decrease the fluoroscopic RAP value by over a factor of two for the double-contrast procedure without an adverse clinical effect by increasing the area of the aperture diaphragm.

Barium Sulfate↗