Biomedical subjects

G S Keyes

Publications and source records attributed to G S Keyes.

7 recordsLinked to original sources

PubMed1984

Hybrid intravenous digital subtraction angiography of the carotid bifurcation.

A hybrid digital subtraction angiography technique and noise-reduction algorithm were used to evaluate the carotid bifurcation. Temporal, hybrid, and reduced-noise hybrid images were obtained in right and left anterior oblique projections, and both single- and multiple-frame images were created with each method. The resulting images were graded on a scale of 1 to 5 by three experienced neuroradiologists. Temporal images were preferred over hybrid images (average score = 3.2 and 2.4, respectively). The percentage of nondiagnostic examinations, as agreed upon by two readers, was higher for temporal alone than temporal + hybrid (4 and 1, respectively). In addition, also by agreement between two readers, temporal + hybrid images significantly increased the number of bifurcations seen in two views (87%) compared to temporal subtraction alone (64%).

Aged↗

PubMed1983

Clinical application of hybrid subtraction digital angiography: preliminary results.

The clinical application of hybrid subtraction in digital fluoroscopy of the vasculature is reported in our first 30 patients studied. Hybrid subtraction combines the advantages of temporal and dual energy subtraction techniques to achieve simultaneous elimination of overlying bone, soft tissue, and motion induced artifacts. Hybrid subtraction improved the subjective appearance of an image in 19 of 30 (63%) studies but additional diagnostic information was only revealed in 11 of 30 (37%) patients.

Angiography↗

PubMed1983

Low-dose, high-frame-rate versus regular-dose, low-frame-rate digital subtraction angiography.

Using intravenous digital subtraction angiography for carotid, cerebral, and renal arteries, a comparison was made between a single pulsed image and an integrated image composed of several pulsed images. The single image was generated with a conventional detected dose per frame while the frames composing the integrated image were generated at a lower dose per frame but at a higher frame rate. Comparisons were made for an equivalent detected dose per image. For relatively stationary arteries, the integrated images were equivalent or superior to the single images. When patient motion was present, or if pulsatile vessel motion was significant, the single image was better than the integrated image. A low-dose, high-frame-rate technique has the potential for furnishing physiologic data in addition to high-quality morphologic information.

Angiography↗

PubMed1983

Evaluation of peripheral vascular disease using digital subtraction angiography.

Intravenous digital subtraction angiography (DSA) facilitates imaging of peripheral arteries and bypass grafts on an outpatient basis. Forty-five patients underwent intravenous peripheral angiography, 16 following placement of bypass grafts. Complex oblique and sagittal angulations optimize visualization of bifurcations and overlapping vascular structures. Reprocessing techniques using integrated masks and contrast images allow for diagnostic delineation of fine vascular detail. This is a practical, noninvasive, well tolerated method for both diagnostic screening and follow-up evaluation of patients with peripheral vascular disease.

Angiography↗

PubMed1983

Work in progress: temporal energy hybrid subtraction in intravenous digital subtraction angiography.

A preliminary investigation of the feasibility and practical clinical utility of combined temporal energy (hybrid) subtraction for intravenous digital subtraction angiography (DSA) was performed in 19 selected patients. Studies of carotid, aortic arch, pulmonary, and aortorenal vessels were obtained. Soft-tissue misregistration artifacts were effectively removed with hybrid subtraction. Image integration was used to produce a signal-to-noise ratio equivalent to that of single frame temporal subtraction. Diagnostic improvements were produced in 20% of the examinations. Hybrid subtraction techniques resulted in an average increase of incident radiation dose to the skin of 15%.

Angiography↗

PubMed1982

Intravenous arteriography using digital subtraction techniques.

The application of digital computers to electronic x-ray imaging devices has rejuvenated interest in the field of intravenous arteriography. By utilizing computer image subtraction techniques, digital roentgenographic systems based on fluoroscopy or computed tomography (scanned projection radiography) provide significantly improved vascular imaging compared with conventional film subtraction methods. Digital subtraction angiography schemes isolate contrast media in the vessel by detecting differences in images obtained before and after the injection of contrast medium or changes in the relative attenuation of contrast media at different x-ray energies. Present applications include carotid and peripheral arteriography, thoracic and abdominal aortography, pulmonary arteriography, and ventriculography. Future applications may include intracerebral and coronary arteriography. These systems should provide low-risk outpatient screening arteriography.

Angiography↗

PubMed1981

The effect of varying spatial resolution on the detectability of diffuse pulmonary nodules. Assessment with digitized conventional radiographs.

Detection and discrimination of miliary disease and small pulmonary nodules were tested at six levels of spatial resolution varying between 0.3 and 2.5 l.p./mm, and receiver operating characteristic (ROC) curves were generated. The test images were obtained by digitizing selected normal and abnormal standard film/screen radiographs. Although there was no statistically significant difference in observer performance between 0.5 and 2.5 l.p./mm, the findings may have clinical relevance. Further observer detection studies of different disease processes are planned to help formulate performance standards for an electric digital radiographic device for chest imaging.

Diagnosis, Differential↗