Search PubMed⌕ Search

Biomedical subjects

C Kimme-Smith

Publications and source records attributed to C Kimme-Smith.

At least 37 records · Page 2Linked to original sources
PubMed1992

Fetal exposure from endovaginal ultrasound examinations in the first trimester.

Ultrasonic obstetrical examinations during the first trimester are now often performed endovaginally with higher-frequency (5-7.5 MHz) transducers operating closer to the fetus than for transabdominal examinations. To estimate exposure to the fetus, propagation distances were obtained from a retrospective study of 100 normal first-trimester endovaginal B-mode examinations. No significant dependence of attenuation on gestational age was observed. The range of the attenuation estimates was 1.8-10.4 dB. A mean attenuation of 5.0 dB at 5 MHz for an average depth of 2.8 cm resulted in an attenuation coefficient of .36 dB/cm/MHz. Exposure (ISPTA) to the fetus at each gestational week from three ultrasound units was very similar: worst-case values of the 100 cases ranged from 1.2-1.9 mW/cm2, well within the Food and Drug Administration (FDA) guidelines of 94 mW/cm2 for derated focused transducers. Energy density deposited to the anterior surface of the fetus during a typical examination, assuming that the transducer is kept stationary over one area for the entire period of the examination (which is unlikely), ranged from 143-217 mJoules/cm2, within the American Institute of Ultrasound in Medicine (AIUM) recommendations.

Female↗
PubMed1992

Effect of poor control of film processors on mammographic image quality.

With the increasingly stringent standards of image quality in mammography, film processor quality control is especially important. Current methods are not sufficient for ensuring good processing. The authors used a sensitometer and densitometer system to evaluate the performance of 22 processors at 16 mammographic facilities. Standard sensitometric values of two films were established, and processor performance was assessed for variations from these standards. Developer chemistry of each processor was analyzed and correlated with its sensitometric values. Ten processors were retested, and nine were found to be out of calibration. The developer components of hydroquinone, sulfites, bromide, and alkalinity varied the most, and low concentrations of hydroquinone were associated with lower average gradients at two facilities. Use of the sensitometer and densitometer system helps identify out-of-calibration processors, but further study is needed to correlate sensitometric values with developer component values. The authors believe that present quality control would be improved if sensitometric or other tests could be used to identify developer components that are out of calibration.

Humans↗
PubMed1992

A new electronically enhanced biopsy system: value in improving needle-tip visibility during sonographically guided interventional procedures.

Sonographically guided fine-needle biopsy procedures are hampered by poor visibility of the needle tip. This study was performed to evaluate a new system for placing needles under sonographic guidance. The Biosponder needle (Advanced Technology Laboratories, Bothell, WA) incorporates a specialized stylet with a passive sensor at its tip. When an ultrasound pulse is detected by the sensor, an electrical signal is transmitted to the sonographic unit by a battery-powered electronic module connected to the stylet and to the scanner. This signal is converted into a bright, flashing marker on the screen at the precise location of the needle tip. The Biosponder system, which uses 20- or 22-gauge needles, was compared with a 20-gauge Turner needle (Cook, Bloomington, IN) in 18 patients with masses or fluid collections and two patients requiring nephrostomy tube placement. The tip of the Turner needle could not be localized precisely in any patient. The shaft of the Turner needle was seen clearly in 13 patients, poorly in three, and was not visualized at all in four patients. Excluding four instances of mechanical failure, the Biosponder system allowed precise localization of the needle tip in every patient and was consistently rated as easier to use than the Turner needle. We conclude that the Biosponder needle, with its precise tip localization and ease of use, is a valuable tool for sonographically guided needle placement.

Biopsy, Needle↗
PubMed1992

Radiation dose.

Explore the source record for details and available documents.

Adult↗
PubMed1992

New and future developments in screen-film mammography equipment and techniques.

Two improvements in mammography equipment during the last 4 years will greatly affect the practice of mammography during the next decade: dose reduction and improved testing equipment for monitoring the quality of mammography. The increased use of digital radiography has stimulated studies comparing digital mammography with screen-film mammography. Some digital algorithms for detecting clusters of calcifications may have application in screening mammography within the next decade.

Female↗
PubMed1991

Increased radiation dose at mammography due to prolonged exposure, delayed processing, and increased film darkening.

Four single-emulsion films introduced over the past 2 years--Du Pont Microvision, Fuji MiMa, Konica CM, and Eastman Kodak OM--were compared with Eastman Kodak OM SO-177 (Min-RE) film to evaluate their varying effects on mean glandular dose of reciprocity law failure due to prolonged exposure, delayed processing, and increased film darkening as a result of increased radiation exposure to improve penetration of glandular tissue. Exposures over 1.3 seconds led to increased radiation doses of 20%-30%. Delays in processing of 6 hours decreased processing speed by 11%-32% for all films except Du Pont Microvision. Optical density increases of 0.40 required 20%-30% more skin exposure for all five films. Optimal viewing densities were also evaluated and found to be different for each of the five films. Mammographers need to be aware of these differences in mammographic films to achieve maximum contrast at mammography.

Breast↗
PubMed1991

Endoluminal catheter-assisted transcervical US of the human embryo. Work in progress.

To enhance visualization of anatomic structures of the human embryo, the authors used a commercially available catheter-based ultrasound (US) transducer (12.5 MHz) introduced through the cervix and into the endometrial cavity of seven women about to undergo voluntary termination of first-trimester pregnancy. The authors term this technique endoluminal catheter-assisted transcervical (ELCAT) sonography. In none of the patients did the US catheter rupture the fluid-filled chorionic/amniotic cavity. The duration of pregnancy ranged from 5.2 to 10.0 menstrual weeks. The most prominent anatomic structures visualized were the heart and neural tube. As an investigational technique, ELCAT US can be used to image anatomic structures of the developing human embryo.

Catheterization↗
PubMed1991

Breast sonography.

Sonographic equipment for breast imaging has continued to improve, and the role of breast sonography has evolved to that of an indispensable adjunct to mammography. Breast sonography is not useful for screening for breast cancer in any age group. Its main use is for the differentiation of cystic vs solid palpable and mammographically visible masses. If strict sonographic criteria are used for a simple cyst, the diagnostic accuracy approaches 100%. Sonographic diagnosis of a simple cyst precludes the need for further workup, including aspiration, biopsy, or followup. This article emphasizes the technical aspects of breast sonography, especially those factors that alter the diagnostic information on the images. These factors can be especially problematic in differentiating cysts and solid masses, the most common diagnostic use of breast sonography. Selection of equipment depends largely on the requirements of a specific practice. Optimally, the sonographic equipment is located close to where mammography is performed, and the sonographic and mammographic findings are interpreted together.

Breast Neoplasms↗
PubMed1991

Detection of renal stones with real-time sonography: effect of transducers and scanning parameters.

Three experiments with a variety of transducers and scanning parameters were designed to investigate if renal stones could be detected with greater certainty by using particular transducers or scanning parameters. First, the lateral resolution, derived from the -6-dB size of the beam profile, was measured at various depths for five transducers commonly used for renal sonography. Second, an in vitro test object was constructed from bovine liver, porcine kidneys, and two renal calculi to access gray-scale map effects on shadow visibility before and after storage in the digital scan converter. The third experiment combined 15 lithotripsy patients with known renal stones with 16 patients in whom the results of renal sonography and other radiographic procedures suggested renal calculi. The group of 15 patients was scanned several times with the transducers and gray-scale maps studied earlier, and the group of 16 patients was scanned only with one transducer and one gray-scale map. On radiographs, 12 of the 16 patients did not have renal calculi. Sonograms of the test object showed that low-contrast images were best for detection of posterior shadows. Three radiologists interpreted the 31 sonograms with a sensitivity of 81% and a specificity of 86% for detecting renal stones. For the 15 cases of renal stones scanned with a variety of transducers, the three radiologists found that annular-array transducers depicted stone shadowing with less ambiguity than mechanical sector transducers did 81% of the time.

Animals↗
PubMed1990

Inter- and intra-observer variability of Doppler peak velocity measurements: an in-vitro study.

To determine the variability of pulsed Doppler peak velocity measurements, four radiologists with differing experience were tested using a calibrated flow phantom. Two ultrasound units, three probes and eight velocity rates varying between 40.5 and 78 cm/sec were studied, with a total of 303 measurements. The results were normalized against a set of 106 separate measurements made under highly-controlled conditions. The residual error standard deviation (not attributable to any systematically varied factor, including the velocity rate) was 6.8 cm/sec, with most of the remaining variation due to changing transducer or machine. Observer/equipment interactions accounted for 15.8% of the observed variability. The duration of the radiologist's Doppler experience had no significant effect.

Blood Flow Velocity↗
PubMed1990

Assurance of consistent peak-velocity measurements with a variety of duplex Doppler instruments.

To assess the need for quality control when measuring peak velocities with Doppler ultrasonography, 17 duplex Doppler instruments from six manufacturers were compared by using a flow phantom that had been calibrated for peak velocities ranging from 23 to 75 cm/sec. Variations in peak-velocity measurements among machines averaged 23% when tested at the same flow rate with a Doppler flow phantom, indicating that scientific articles that document peak velocities for various disease processes should be accompanied by equipment calibration data. Doppler string and flow phantoms were compared, and each was found to have deficiencies. Techniques for quality assurance procedures for Doppler measurements are given that should achieve consistent peak-velocity measurements on serial scans of patients undergoing treatment for vascular conditions.

Blood Flow Velocity↗
PubMed1990

New mammography screen/film combinations: imaging characteristics and radiation dose.

Five types of film (Kodak OM, Kodak OM-SO177, Konica CM, Dupont Microvision, and Fuji MiMa) exposed in combination with seven different intensifying screens (Min R, Min R Medium, Siemens Orthox MA, Kyokka HR Mammo Fine, Agfa Gevaert Detail S (old and new), and Konica Monarch) were processed for either 90 sec (at 33.3 degrees C) or 3 min (at 35.0 degrees C). The films imaged a Computerized Imaging Reference System phantom with additional detail test objects placed on its surface to produce four groups of objects with which to evaluate resolution and contrast. For objects that tested resolution, the Kyokka HR Mammo Fine (Fuji) screen was statistically significantly superior; for objects that tested contrast, the Konica Monarch screen was statistically significantly superior. Extended processing did not affect Dupont and Kodak OM film as much as it affected the other films. It did affect contrast for the other films tested. The mean glandular doses from gridless exposures ranged from 32 to 80 mrad (0.32-0.80 mGy) over all film/screen/processing combinations for a 4.5-cm-thick test object. Several new film/screen combinations can provide images superior to the Kodak Min R/OM combination at a reduced radiation dose. The Kyokka HR Mammo Fine (Fuji) screen was found statistically superior in radiographic resolution of mammographic test objects and the Konica Monarch screen was found to be superior in defining contrast.

Mammography↗
PubMed1989

Digital mammography. A comparison of two digitization methods.

A preliminary study of 40 different radiodense breasts digitized with a Fuji high resolution BAFBr:EU2+ imaging plate enabled us to establish acceptable enhancement procedures with a Fuji Computer Radiology 201 system. Screen-film images of 36 of these breasts were also digitized and enhanced on a Damon DETECT TV system. Three radiologists specializing in mammography reviewed each pair of images. For the 20 normal examinations, both digital methods were considered equivalent in image quality, while for the 16 cases containing pathology (masses and/or calcifications) the TV system was considered to provide the best image quality twice as often as the laser scanned system. The radiologists rejected both methods of enhancement for 8% of the images. Despite cost differences between the two systems, both have equal capability in penetrating dense breasts. However, both systems have several significant deficiencies which preclude their clinical use. At the present time, there is no objective justification for using either system for breast imaging other than in an experimental capacity.

Female↗
PubMed1989

Frequency measurements in real-time US equipment: variations from expected values.

The frequency responses of nine real-time mechanical probes and two pulsed Doppler probes from four manufacturers were measured. The reflected frequency was measured in a clinical environment by evaluating the pulser, transducer assembly, and receiver as a system. Two independent systems were used for these measurements: a spectrum analyzer and a data acquisition system that computed the fast Fourier transform of the reflected waveform. Results showed that probe frequency (calibrated by the manufacturer in the transmit mode with a hydrophone) was as much as 30% higher than that found by means of frequency measurement procedures with the probe attached to the ultrasound system and evaluated in the receive mode. Such large discrepancies indicate that if acceptance testing of the frequency spectrum is not performed at a clinical facility, prolonged clinical evaluation of new equipment should be arranged.

Ultrasonics↗
PubMed1989

Mammographic film-processor temperature, development time, and chemistry: effect on dose, contrast, and noise.

Six different combinations of film-processor temperature (33.3 degrees C, 35 degrees C), development time (22 sec, 44 sec), and chemistry (Du Pont medium contrast developer [MCD] and Kodak rapid process [RP] developer) were each evaluated by separate analyses with Hurter and Driffield curves, test images of plastic step wedges, noise variance analysis, and phantom images; each combination also was evaluated clinically. Du Pont MCD chemistry produced greater contrast than did Kodak RP chemistry. A change in temperature from 33.3 degrees C (92 degrees F) to 35 degrees C (95 degrees F) had the least effect on dose and image contrast. Temperatures of 36.7 degrees C (98 degrees F) and 38.3 degrees C (101 degrees F) also were tested with extended processing. The speed increased for 36.7 degrees C but decreased at 38.3 degrees C. Base plus fog increased, but contrast decreased for these higher temperatures. Increasing development time had the greatest effect on decreasing the dose required for equivalent film darkening when imaging BR12 breast equivalent test objects; ion chamber measurements showed a 32% reduction in dose when the development time was increased from 22 to 44 sec. Although noise variance doubled in images processed with the extended development time, diagnostic capability was not compromised. Extending the processing time for mammographic films was an effective method of dose reduction, whereas varying the processing temperature and chemicals had less effect on contrast and dose.

Female↗
PubMed1989

Diagnosis of breast calcifications: comparison of contact, magnified, and television-enhanced images.

Matched contact and microfocal-spot-magnified images of 31 breasts, each containing a cluster of microcalcifications within a biopsy-proved benign (n = 21) or malignant (n = 10) lesion, were evaluated. Each matched set consisted of one image magnified 1.5 or 2.0 times by a microfocal spot; one contact film-screen mammogram; and one television-digitized, enhanced, and optically magnified contact film-screen mammogram. Three experienced mammographers and three senior diagnostic radiology residents with 2 weeks of training in mammography interpreted the calcifications. The average area under the receiver-operating-characteristic curve for the experienced mammographers was 0.60 for contact radiographs, 0.61 for the television-digitized images, and 0.69 for the microfocal-spot-magnified radiographs. The less experienced senior residents scored below a random choice, 0.44, for the television-digitized images; 0.51 for contact radiographs; and 0.69 for the microfocal-spot-magnified radiographs. We conclude that when evaluating microcalcifications, radiologists without extensive experience in mammography should not substitute television-digitized and enhanced contact mammograms for microfocal-spot-magnified mammograms; rigorous clinical evaluation is needed before this system is accepted for clinical use.

Analysis of Variance↗