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Biomedical subjects

C S Higgins

Publications and source records attributed to C S Higgins.

9 recordsLinked to original sources
PubMed1989

Factors associated with hospital-specific cesarean birth rates.

The variation in hospital-specific cesarean birth rates was examined using a multiple regression analysis in a national data base of deliveries in 1977. This data base included 222,285 singleton births in 282 hospitals representing all regions of the United States. The 32 independent variables included measures of medical risk, technologic sophistication, demographic characteristics and economic incentives. The incidences of medical risk factors, nonwhite race and ratio of obstetricians to fertile women were associated positively with hospital-specific cesarean delivery rates. Participation in health maintenance organizations and numbers of deliveries were correlated negatively with those rates. Hospital-specific cesarean delivery rates were not associated with technologic sophistication, malpractice premiums or reimbursement differences between routes of delivery. Pay source stratified models explained 45-63% of the variation in the hospital-specific cesarean rates. Sensitivity analysis revealed that even a 50% change in the incidence of any independent variable would change the cesarean delivery rate by less than 2%.

Birth Rate↗
PubMed1978

Measurement of regional cerebral blood volume by emission tomography.

The technique of positron emission tomography was used to measure cerebral blood volume (CBV) in 10 normal right-handed human volunteers following inhalation of trace quantities of cyclotron-produced, 11C-labeled carbon monoxide. In scans obtained 4 cm above the orbitomeatal line, CBV was 4.3 ml per 100 gm of tissue, whereas in scans obtained 8 cm above the orbitomeatal line, CBV was significantly less (3.3 ml per 100 gm; p less than 0.001). This difference reflects the greater proportion of gray matter in the lower scan. Furthermore, the CBV was significantly larger (p less than 0.001) in the left cerebral hemisphere in the tomographic scans obtained 4 cm above the orbitomeatal line. These scans include the region of the superior surface of the temporal lobe (planum temporale), which is thought to be larger in individuals with left cerebral dominance for speech. This observation is the first in vivo demonstration of a structural correlate of a known functional difference in the cerebral hemispheres of man.

Blood Volume Determination↗
PubMed1978

Design considerations for a positron emission transverse tomograph (PETT V) for imaging of the brain.

Imaging of the brain by positron emission tomography can be optimized for sensitivity by dedicating the design of the tomograph to this application. We have designed a multislice positron emission tomograph (PETT V) for imaging the human brain and the whole body of small experimental animals. The detector system of PETT V consists of a circular array of 48 NaI(Tl) scintillation detectors, each fitted with two photomultiplier tubes, with one dimensional positioning capability. Suitable sampling is achieved by rotation of the circular array of detectors and by a wobbling motion of the detector circle. The proposed system is capable of providing seven slices simultaneously, with a spatial resolution in the plane of the slice from 7 to 15 mm and with slice thicknesses of 7 and 14 mm. The minimum scanning time is 1 sec. The estimated overall sensitivity of PETT V is 350,000 counts/sec/mCi in a 20 cm diameter phantom for a resolution of approximately 1.5 x 1.5 cm. The system is under construction.

Animals↗
PubMed1978

A multislice positron emission computed tomograph (PETT IV) yielding transverse and longitudinal images.

We designed, built, and tested a positron emission tomograph (PETT IV) capable of providing seven slices of the human body simultaneously. PETT IV utilizes a moving hexagonal array of 48 scintillation detectors placed around the subject. Each detector consists of a cylindrical activated sodium iodide crystal optically coupled to two photomultiplier tubes. The multislice capability is achieved by comparing the light outputs of the two photomultiplier tubes in each detector. The images are displayed either as transverse or as longitudinal tomographic sections. This system provides high sensitivity and resolution, and permits rapid and accurate three-dimensional imaging of the head and body.

Electrons↗
PubMed1977

Determination of radionuclide concentrations with positron CT scanning (PETT): concise communication.

A series of experiments was undertaken to evaluate the response of a positron emission transverse tomograph (PETT) to measured radionuclide concentrations similar to those encountered in human studies. The correlation between the response of the imaging system (mean PETT number/min), and the concentration of the radioactivity producing the output data, was linear with a computed sensitivity of 2720 PETT number/min, per micronCi/ml, per picture element, for a radionuclide (100% beta+) contained in either of two phantoms and imaged with a reduction of 1.5 cm. It was concluded that the output data are essentially independent of the imaged object's physical dimensions for the range of 18-28-cm diam and faithfully reflect the regional radioactivity concentration within the object, provided valid attenuation correction is achieved and the sampled area is not compromised by the imaging system's limitations of spatial resolution.

Computers↗
PubMed1976

Design and performance characteristics of a whole-body positron transaxial tomograph.

A whole-body positron-emission transaxial tomograph (PETT III) is described in detail and evaluated in terms of resolution, accuracy, and efficiency. The PETT III utilizes annihilation coincidence detection to provide spatial resolution; high sensitivity is achieved by using 48 Nal(tl) detectors set in a hexagonal array with a multiple-coincidence logic. The assumptions and approximations made in the reconstruction and their effect on image quality are discussed. Phantom studies shows the depth-independent resolution and response of PETT III, as well as its ability to recover activity distribution quantitatively in the cross section measured. Images obtained with patients and normal volunteers show the potential clinical utility of PETT III.

Evaluation Studies as Topic↗