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Biomedical subjects

F G Sommer

Publications and source records attributed to F G Sommer.

At least 55 records · Page 3Linked to original sources
PubMed1986

Mammographic microcalcifications: detection with xerography, screen-film, and digitized film display.

Pulverized bone specks and aluminum oxide specks were measured by hand into sizes ranging from 0.2 mm to 1.0 mm and then arranged in clusters. These clusters were superimposed on a human breast tissue phantom, and xeromammograms and screen-film mammograms of the clusters were made. The screen-film mammograms were digitized using a high-resolution laser scanner and then displayed on cathode ray tube (CRT) monitors. Six radiologists independently counted the microcalcifications on the xeromammograms, the screen-film mammograms, and the digitized-film mammograms. The xeromammograms were examined with a magnifying glass; the screen-film images were examined with a magnifying glass and by hot light; and the digitized-film images were examined by electronic magnification and image processing. The bone speck size that corresponded to a mean 50% detectability level for each technique was as follows: xeromammography, 0.550 mm; digitized film, 0.573 mm; and screen-film, 0.661 mm. We postulate that electronic magnification and image processing with edge enhancement can improve the capability of screen-film mammography to enhance the detection of microcalcifications.

Breast Diseases↗
PubMed1986

Some applications for a personal computer data-base system in radiology.

Applications for a personal-computer-based relational data-base system in an academic radiologist's office are described. These include archival and flexible retrieval of desired cases from clinical-case and teaching-file data bases and data-base management of a transparency-slide collection and radiology journal articles. All applications were implemented by using commercially available software that was specially adapted for each purpose. These data-base systems have been effective organizing tools over the past 4 years.

Computers↗
PubMed1985

Dual-energy projection radiography in the evaluation of femoral neck strength, density, and mineralization.

Two different dual-energy projection radiography techniques were utilized in an attempt to predict femoral neck strength, bone density, and bone mineral content in 19 pairs of cadaver specimens. Positive simple linear correlation was observed between dual-energy scanned projection measurements and dry density, ash fraction, cross-sectional cortical bone area and, to a lesser degree, force required for fracture, but not trabecular bone volume, failure time, or Singh trabecular grade. Dual-energy film radiography was found to be a less reliable indicator of femoral neck strength, density, and mineral content. Dual-energy scanned projection results related linearly to mineral-equivalent solution (K2HPO4) concentration, and demonstrated long-term reproducibility in repeated specimen studies. Correction factors derived to account for differences in femoral size and rotation were shown to be reliable over a moderate range of neck projections. Although bone mineral measurement at other sites may provide comparable or greater information concerning hip fracture risk, dual-energy scanned projection radiography appears to be a useful technique for assessment of bone density, mineral content, and strength in the femoral neck.

Absorptiometry, Photon↗
PubMed1985

Scatterer-induced frequency variations in reflected acoustic pulses: implications for tissue characterization.

A Hilbert transform approach to the detection of the instantaneous center frequency of reflected ultrasonic pulses was performed for simulated reflected ultrasonic pulses, and digitized ultrasonic waveforms from tissue phantoms. Considerable center frequency modulation was observed for both simulated and recorded ultrasonic waveforms. This phenomenon of frequency modulation can be explained with the aid of a phasor model, in which variations in instantaneous frequency results from the interaction of a multitude of overlapping ultrasonic pulses arising from different scattering centers in tissue. The observed frequency modulation of ultrasonic signals has important implications for tissue characterization techniques, including the measurement of attenuation by the determination of the shift in ultrasonic center frequency.

Mathematics↗
PubMed1985

Digital processing of film radiographs.

Initial clinical experience with a system for the digitization, processing, and display of film radiographs is described. Film is digitized using a high-intensity laser scanner; the recorded image data may then be subjected to a wide variety of processing options, with display of processed images on television monitors. The possibilities of clinical applications to processing and display of chest radiographs and film mammograms are described. A comparison of conventional analog subtraction and digitized film subtraction angiography indicated equivalent diagnostic capability, with the advantage of flexible, interactive image processing with the digital technique. A specially designed, energy-selective cassette permits dual-energy imaging from two films effectively exposed to different x-ray energy spectra. Dual-energy imaging may be capable of the characterization of body materials, including lung nodules, and useful for eliminating obscuring radiographic shadows overlying regions of interest.

Angiography↗
PubMed1985

Bone mineral density in the femoral neck: quantitative assessment using dual-energy projection radiography.

Two different dual-energy projection radiography techniques were used to quantitate bone mineral density in the femoral neck. A heterogeneous population of normal aging individuals of both genders was studied. Using a dual-energy scanned projection method, femoral neck mineralization was shown to decline with age in men and women with normal endocrine status, and to correlate positively with serum calcium level in women and both genders combined. No significant relation to incidence and severity of vertebral body compression fractures, the Singh trabecular index, glomerular filtration rate, urinary calcium excretion, plasma levels of vitamin D, parathyroid hormone, or alkaline phosphatase was demonstrated. According to both methods, femoral neck density tended to be higher in taller and heavier subjects. Although it may not be possible to predict accurately the occurrence of femoral neck fracture in a given individual, dual-energy scanned projection radiography appears to be useful in determining mineral status of the site at risk.

Adult↗
PubMed1985

Dual-energy scanned projection radiography of osseous metastatic disease.

Dual-energy scanned projection radiography was used to evaluate eight patients with both lytic and blastic metastatic disease in the axial skeleton. The ability to selectively cancel obscuring soft-tissue structures from images resulted in improved conspicuity of involved sites, compared with conventional radiographic studies, despite greater quantum noise and lower inherent spatial resolution. Other desirable features of the technique include a projected format, image enhancement by contrast and brightness optimization, rapid data acquisition, convenient image storage and retrieval, and low radiation dose. Since the majority of osseous metastases involve axial sites, dual-energy scanned projection radiography may be a useful adjunctive modality in the management of oncology patients.

Bone Neoplasms↗
PubMed1984

Digital film processing: applications to the musculoskeletal system.

A prototype digital film processing system was systematically evaluated for specific applications to the musculoskeletal system. Test objects included a line pair resolution phantom and specimens designed to simulate lytic cortical and both lytic and sclerotic cancellous bone lesions. Clinical radiographs from a wide variety of osseous and soft tissue disorders were studied. Although digitization cannot improve the inherent resolution and information content of film, it is capable of enhancing contrast and visualization of detail. As a result, digital processing carries significant potential for improved diagnosis in musculoskeletal radiology.

Bone Diseases↗
PubMed1984

Renal colic: the role of ultrasound in initial evaluation.

A prospective sonographic study of 21 patients with suspected renal colic was undertaken to detect the presence or absence of urinary tract calculi. The presence of calculi was diagnosed sonographically by visualization of the calculus and/or unilateral hydronephrosis in all 18 cases in which presence of a calculus was subsequently proved by surgery, spontaneous passage and recovery, or intravenous urography. In the two cases in which the sonographic examination demonstrated neither calculi nor unilateral obstruction, further evaluation confirmed the absence of calculi. There was one false-positive examination in which unilateral hydronephrosis was detected secondary to a retroperitoneal tumor. There were no false-negative examinations. The results of this study support the use of ultrasound in the initial evaluation of renal colic.

Adult↗
PubMed1984

Spleen structure in Hodgkin disease: ultrasonic characterization. Work in progress.

Ultrasonic waveforms backscattered from human spleens in vivo were recorded for 10 normal subjects and 21 patients with Hodgkin lymphoma prior to staging laparotomy. A measure of the structure of splenic tissue, the "mean scatterer spacing" was calculated for each subject from the recorded data. Comparison of these measurements with the results of staging laparotomy indicated that spleens involved with lymphoma are generally characterized by increased scatterer spacing compared with normal splenic tissue. The observed histologic differences between normal and lymphomatous spleens appear to account for the measured differences in tissue structure.

Adult↗
PubMed1984

Measurement of attenuation and scatterer spacing in human liver tissue: preliminary results.

A study measuring two quantitative parameters of human liver in vivo was performed to assess the reliability of measurement of the two parameters, and to evaluate their potential for diagnosing and grading diffuse fibrotic liver disease. The parameters measured were attenuation and "mean scatterer spacing," a measure of tissue structure. Components of variance analysis demonstrated that variation in the measured parameters was a function of the subject being examined, with significant variation noted between data acquisition sessions performed the same day. There was no significant additional variation of the measurements from week to week over a one-month period. A good correlation of the parameters with the severity of liver disease indicates that the technique may be useful in the clinical evaluation of diffuse liver disease.

Analysis of Variance↗
PubMed1983

Duplex ultrasound scanning of the carotid arteries with velocity spectrum analysis.

Duplex ultrasound examination of the carotid arteries using high-resolution realtime imaging and pulsed Doppler flow measurements with velocity spectrum analysis was performed on a series of 50 consecutive patients (100 vessels), and findings were compared with findings of conventional carotid arteriography. The criteria for an abnormal duplex examination included: a velocity ratio of 1.5 or more (ratio of the maximum internal carotid artery [ICA] flow velocity to the maximum common carotid artery flow velocity); turbulence, as indicated by an ICA velocity spectral width of 40 cm per second or more; visible plaque that produced an ICA stenosis of 50% or more; a maximum ICA velocity of 100 cm per second or more; and inability to detect ICA flow. A flow-limiting stenosis was defined arteriographically as a 50% or greater stenosis of the diameter of the arterial lumen. The velocity ratio was the best single duplex criterion, with an overall accuracy of 88%. The sensitivity or specificity of the duplex examination was as high as 97%, depending on the number of duplex criteria that were abnormal.

Arteriosclerosis↗
PubMed1983

Image processing to reduce ultrasonic speckle.

The most significant source of noise in contemporary ultrasonic images is ultrasonic speckle, a phenomenon relating to random interference of ultrasonic waveforms in transducer sample volumes. Averaging of a number of ultrasonic images, which are slightly spatially shifted with respect to one another, leads to image improvement via speckle reduction. Such processing may provide a useful improvement of clinical ultrasonic images.

Humans↗
PubMed1982

Stochastic frequency-domain tissue characterization: application to human spleens "in vivo'.

Ultrasonic waveforms backscattered from normal and pathologic human spleens were recorded in vivo using a high-speed digital data acquisition system. A frequency-domain analysis was performed for 50 digitized waveforms from each spleen, in which autocorrelations of frequency spectra were employed to measure the mean spacing among adjacent tissue scatterers. Mean scatterer spacing for normal spleens averaged 1.10 +/- 0.14 mm, whereas abnormal, diffusely of these measurements are in accord with those expected from splenic histology. The techniques described may be valuable in ultrasonic diagnosis of the spleen and other organs.

Adult↗
PubMed1982

Contrast resolution of line-scanned digital radiography.

Contrast resolution of a prototype system for line-scanned digital radiography was evaluated using a phantom simulating low contrast tumors within the body. Simulated tumors having radiographic contrast as low as 0.5% were detectable in these studies. The results of these digital radiographic studies compare favorably to those of computed tomography in terms of both low contrast detectability and radiation dosage. Dual energy projection radiographic techniques show promise for eliminating obscuring shadows caused by overlying structures from digital radiographs, thus permitting clinical utilization of the excellent contrast resolution of the line scanned projection system.

Models, Structural↗
PubMed1982

Renal imaging with dual energy projection radiography.

Applications of dual energy radiography to renal imaging were evaluated using an experimental system for line-scanned projection radiography. This system combines digital radiographs simultaneously obtained at two differing x-ray energies (85 and 135 kVp) to create images in which materials of a desired mean atomic number are selectively cancelled. A preliminary evaluation of the technique was performed for three renal imaging problems: detection and characterization of renal masses of low radiographic contrast, evaluation of renal artery stenosis and unilateral renal ischemia, and detection of renal calculi. In all three applications, the dual energy technique produced results indicating potential advantages over conventional radiographic studies.

Adenocarcinoma↗