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Biomedical subjects

F G Sommer

Publications and source records attributed to F G Sommer.

At least 19 recordsLinked to original sources
PubMed1992

The pelvis: T2-weighted fast spin-echo MR imaging.

Fast spin-echo (SE) T2-weighted magnetic resonance (MR) imaging provides images with highly T2-weighted contrast in substantially reduced imaging times. In a prospective evaluation, fast SE T2-weighted imaging of the pelvis was compared with conventional SE T2-weighted imaging in 30 consecutive patients in whom pelvic pathologic conditions were suspected. Three reviewers independently analyzed the images for (a) overall image quality, (b) pelvic organ definition, (c) conspicuity of pelvic fluid, and (d) conspicuity of pelvic pathologic conditions. Fast SE images were rated superior to conventional SE T2-weighted images in 60% (54 of 90) of the case reviews for overall image quality, in 69% (62 of 90) for pelvic organ definition, in 63% (57 of 90) for conspicuity of pelvic fluid, and in 68% (43 of 63) for conspicuity of pelvic pathologic conditions. The fast SE examinations were typically three to four times faster than conventional SE T2-weighted examinations. No pathologic findings seen on conventional SE T2-weighted images were undetected on fast SE images. Fast SE images may replace conventional SE T2-weighted images in MR imaging of the pelvis.

Abdomen↗
PubMed1991

Gynecologic vascular abnormalities: diagnosis with Doppler US.

The authors describe the use of duplex and/or color Doppler ultrasonography of the pelvis in three women to demonstrate the presence of venous malformations. One patient with a pulsatile vaginal mass was shown to have an arteriovenous malformation of the vaginal wall. The second patient was shown to have an unsuspected venous angioma in the endometrial cavity. The third patient was shown to have adnexal varices that closely mimicked hydrosalpinx. In the latter two cases, the duplex and color flow capabilities of an endovaginal probe were especially important.

Adult↗
PubMed1991

Prostatic MR imaging performed with the three-point Dixon technique. Work in progress.

The three-point Dixon technique is an enhancement of the original Dixon method for the creation of water- and fat-proton magnetic resonance (MR) images. With the three-point Dixon technique, three measurements of phase shift at 0, pi, and -pi between the fat and water resonances are employed. Compensation for B0 inhomogeneity leads to an error-free decomposition into water- and fat-proton images; an accurate B0 map is also created. The lack of chemical shift artifact in the water- and fat-selective MR images permits the application of narrow receive bandwidth for the creation of T2-weighted images with a high signal-to-noise ratio. The technique was applied in vivo with four healthy subjects, seven patients with prostatic carcinoma, and one patient with benign prostatic hypertrophy and compared with conventional T2-weighted imaging. The three-point technique yielded images with improved definition of normal intraprostatic structures and zonal anatomy and, in some cases of prostatic carcinoma, provided better visualization of extraprostatic spread of tumor.

Adult↗
PubMed1989

Characterization of splenic structure in Hodgkin disease by using narrow-band filtration of backscattered ultrasound.

A preliminary study was performed to evaluate the effectiveness of narrow-band filtration of backscattered ultrasound for the detection of splenic involvement in patients with Hodgkin disease. Regions of interest were identified in the spleens of 14 normal volunteers and eight Hodgkin disease patients before staging laparotomy. An analysis of the narrow-band-filtered waveforms showed that the mean amplitudes of the filtered ultrasonic signals received correlated with the presence of extensive splenic involvement with Hodgkin disease (defined as more than four grossly visible nodules on cut section) (p = .0004). Conversely, mean amplitudes of unfiltered ultrasonic backscatter, employed in conventional sonographic imaging, did not correlate with splenic involvement (p = .5). Phantom studies were performed to develop a tissue model for the observed phenomena; images of the phantoms and of the involved and uninvolved spleens were made by using techniques involving narrow-band filtration of backscattered ultrasound. Our results indicate that narrow-band-filtered sonography holds promise for detecting lymphomatous involvement of the spleen, although larger studies, with equipment allowing real-time implementation of narrow-band filtering, are needed.

Acoustics↗
PubMed1988

Noise reduction in magnetic resonance imaging.

This paper describes a noise-reduction technique applicable to multiple-measurement systems. This method, known as measurement-dependent filtering (or MDF), can be used to advantage in a number of MRI applications. We present the general theory for one of these applications, material-canceled projection imaging. We discuss and show the results of MDF for material-canceled images as well as for heavily T2-weighted spin-echo images and computed T2 images. Significant improvements in SNR are demonstrated while spatial resolution is preserved.

Electricity↗
PubMed1987

The abnormal prostate: MR imaging at 1.5 T with histopathologic correlation.

Thirteen patients with biopsy-proved adenocarcinoma were prospectively examined with magnetic resonance (MR) imaging with use of a 1.5-T superconducting magnet. All patients subsequently underwent radical prostatectomy and careful, axial, histologic mapping of prostatic disease. Histologic findings were recorded on serial, axial diagrams to ensure precise pathologic correlation with the MR images. MR permitted identification of eight of 12 (67%) adenocarcinomas as hypointense foci (relative to the surrounding, higher intensity, peripheral zone); but tumor volume was under-estimated with MR imaging in five of eight cases (63%). Nodules of prostatic hyperplasia were identified correctly in only one of nine patients (11%). These findings suggest that, despite that fact that high field strength MR imaging currently does not depict all pathologic foci within the prostate, it may be of predictive value in the differential diagnosis of prostatic abnormalities when their locations are demonstrable.

Adenocarcinoma↗
PubMed1987

Frequency diversity speckle processing.

Ultrasonic waveform data from a tissue-mimicking phantom containing low contrast targets was digitized, stored and processed prior to creating and displaying ultrasonic images. Speckle reduction was performed by digital filtering of the waveform data with appropriately spaced and weighted digital filters, prior to both coherent and incoherent image averaging. The resultant images showed increased signal-to-target boundaries was noted in the processed, compared to unprocessed, images. Incoherent and coherent processing were investigated, and appeared to be equivalent.

Humans↗
PubMed1986

Removal of air from liver specimens via vacuum.

Fresh liver specimens have been ultrasonically imaged in vitro in order to evaluate specimen air content before the acquisition of ultrasonic waveform data for tissue characterization studies. It was found necessary to expose liver slices to vacuum for about 16 h in order to remove enough air to acquire waveform data from air-free regions of interest in these slices. Larger portions of liver, and whole liver, were found to retain large amounts of air even after 16 h of exposure to vacuum.

Air↗
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

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↗