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Biomedical subjects

P L Carson

Publications and source records attributed to P L Carson.

At least 73 records · Page 4Linked to original sources
PubMed1983

A tissue-equivalent upper abdominal phantom.

The first prototypes of an abdominal phantom have been constructed. The phantom is intended for eventual use in training diagnostic ultrasound personnel and in demonstrating commercial equipment. It is constructed from plastics believed to be stable and approximately tissue-equivalent at room temperature. Abdominal structures are formed from a dispersion of a polystyrene butadiene plastic in mineral oil. Polyvinyl chloride particles are incorporated to provide the desired attenuation coefficients and scattering levels. B-scans of the phantom produced realistic images, although problems associated with scanning technique and somewhat high phantom attenuation were noted. Very useful phantoms should result from relatively simple improvements in construction techniques.

Abdomen↗
PubMed1982

Anthropomorphic breast phantoms for assessing ultrasonic imaging system performance and for training ultrasonographers: part I.

Three prototype anthropomorphic breast phantoms are discussed. The phantoms were constructed using ultrasonically tissue-mimicking materials; these materials mimic various tissue parenchymae in terms of attenuation, speed of sound, density, and scatter level. Realistic artifacts related to refraction and reflection at interfaces between different simulated parenchymae are produced. The phantoms represent premenopausal breasts, and they complement one another. Two of them represent the dense breasts of women under 30 years of age, and one represents that of a woman between 35 and 40 years of age. Of the former two, one produces what is apparently above-average refraction effects in the region of the peripheral fat layer; the other produces more typical refraction effects. Simulated tumors, cysts, and calcifications of various sizes are suspended in the glandular regions. Such phantoms are valuable for use in developmental testing of state-of-the-art ultrasound machines, quality assurance testing of clinical machines, and training of sonographers in breast imaging.

Adult↗
PubMed1982

Anthropomorphic breast phantoms for assessing ultrasonic imaging system performance and for training ultrasonographers: part II.

Three prototype anthropomorphic breast phantoms are discussed. The phantoms were constructed using ultrasonically tissue-mimicking materials; these materials mimic various tissue parenchymae in terms of attenuation, speed of sound, density, and scatter level. Realistic artifacts related to refraction and reflection at interfaces between different simulated parenchymae are produced. The phantoms represent premenopausal breasts, and they complement one another. Two of them represent the dense breasts of women under 30 years of age, and one represents that of a woman between 35 and 40 years of age. Of the former two, one produces what is apparently above-average refraction effects in the region of the peripheral fat layer; the other produces more typical refraction effects. Simulated tumors, cysts, and calcifications of various sizes are suspended in the glandular regions. Such phantoms are valuable for use in developmental testing of state-of-the-art ultrasound machines, quality assurance testing of clinical machines, and training of sonographers in breast imaging.

Adult↗
PubMed1981

Breast imaging in coronal planes with simultaneous pulse echo and transmission ultrasound.

Clear delineation of breast architecture was achieved with compound pulse echo ultrasound imaging in which the images were acquired in the coronal planes used for quantitative transmission ultrasonic computed tomography. Since most connective tissue planes in the breast radiate toward the nipple, compound scans from the sides of the breast record normal interfaces more consistently and reveal greater symmetries in normal portions of relatively full breasts than do conventional scans in sagittal or transverse planes. Simultaneous acquisition of the pulse echo images and images representing the local ultrasound attenuation coefficient and speed of ultrasound suggested complementary role for reflection and through-transmission images in breast cancer detection. The high quality of pulse echo images in coronal planes provides the potential for more complete pulse echo diagnosis and the basis for spatial correlation of lesions viewed in pulse echo and ultrasonic computed tomograms. These observations may permit routine ultrasonic computed tomography of the breast in the clinical setting.

Breast↗
PubMed1978

Transport phenomena in laminar flow of blood.

Recently it has been shown experimentally that transport of heat and gas (specifically oxygen and helium) are augmented in the laminar flow of aqueous suspensions of polystyrene spheres 50 and 150 micrometer in diameter. In this report, data on heat and gas transport are correlated. Application of this correlation to flowing blood leads to the following conclucions. There is no significant augmentation of oxygen and heat transport in flowing blood even at shear rates much higher than physiological shear rates; an observation which is in accord with the experimental results. The augmentation of the diffusion coefficient of plasma proteins in flowing blood, though not very high, appears to be measurable. Of the total measured augmentation of about 6000--30 000% in platelet diffusivity in flowing blood, quoted from the literature, about 500% is attributable from this correlation to fluid mechanical forces, and the balance is hypothetically attributed to other forces (electrical or biochemical) present in blood.

Biological Transport↗
PubMed1977

Performance survey of ultrasound instrumentation and feasibility of routine monitoring.

Short quality control tests for ultrasound instruments were developed based on the AIUM standard 100mm test object and procedures recommended for its use. While demonstrating the tests of technologists on their instruments, the authors obtained performance data on instruments in 22 hospitals. Subsequent quality control testing on the same instruments demonstrated that manufacturer's servicemen usually had improved performance significantly in the rather large number of cases in which adjustments were indicated by initial tests. Technologists in several hospitals, as well as the authors, performed the tests routinely for extended periods of time, with a moderately high yield for detection or demonstration of malfunctions.

Equipment and Supplies, Hospital↗
PubMed1977

A modeled study for diagnosis of small anechoic masses with ultrasound.

Hemispherical holes created in the bases of uniform natural sponges were imaged in water to determine how anechoic masses fill in with echoes at increased gains. The increase in gain, from the threshold for outlining a hole, to the fill-in of the hole with echoes, was obtained for a range of hole diameters and imaging conditions. These gain changes fit on a smooth curve when plotted against the hole diameter divided by the ultrasound beam width. The main sources of fill-in, beam width and multiple reverberations, appear to behave similarly in vivo. Understanding these effects may help reduce diagnostic errors.

Cysts↗
PubMed1976

Rapid evaluation of many pulse echo system characteristics by use of a triggered pulse burst generator with exponential decay.

A pulse burst generator is utilized in which the pulses are triggered by the transmitter pulse of the ultrasound system being tested. The pulses are spaced the equivalent of every 2 mm in the body, and their amplitude decays with 0, 1.25, or 2.5 dB/cm over greater than a 50 dB dynamic range. By replacing the ultrasound transducer with the pulse generator, one can record quite easily the accuracy of depth gain compensation (DGC) and of distance measurements in A mode and B mode. If the DGC on the ultrasound unit can be turned to zero, the unit's A mode display characteristic and B mode gray scale curve can be determined rapidly and the receiver gain control or attenuator can be calibrated. Measurement of a receiver signal-to-noise ratio is possible, and more quantitative imaging should be facilitated as well.

Evaluation Studies as Topic↗
PubMed1975

Cross-sectional anatomic images by gamma ray transmission scanning.

60Co gamma-ray transmission data were measured along linear scan paths at a number of angular orientations with respect to the patient and submitted to a computer software program. Reconstructed images are displayed as digital density printouts and as isodensity contours on an x-y plotter or oscilloscope screen. Image resolution is limited primarily by factors such as collimation and the amount of transmission data collected; with the rather rudimentary apparatus at disposal, a spatial resolution better than 5 mm has been achieved.

Computers↗
PubMedDate not supplied

Hepatic imaging: positron emission tomography, digital angiography, and nuclear magnetic resonance imaging.

Major advances in diagnostic imaging of the human body have been made in recent years. Positron emission tomography, a technique founded on advances in radiopharmaceuticals and radionuclide imaging apparatus, permits imaging regional metabolism, metabolite distribution, and flow. Thus far, its major applications have been in the study of the brain, and to a lesser extent, the heart; however, it is also finding a role in the study of the liver. Digital angiography is being applied to fluoroscopic systems which permits visualization of relatively low doses of intravascular iodinated radiographic contrast media. Imaging of the major arteries is possible using simple intravenously administered contrast media; digital techniques also increase the diagnostic yield in intraarterial studies. Nuclear magnetic resonance (NMR) imaging is an outgrowth of laboratory NMR spectroscopy; the interaction of radiofrequency signals with nuclei in strong magnetic fields permits imaging the distribution and certain chemical properties of various isotopes. Hydrogen NMR imaging is proving most useful for clinical diagnosis. The techniques used to image hydrogen are also being applied to NMR spectroscopy in vivo of various isotopes, including carbon-13, phosphorus-31, and hydrogen-1.

Angiography↗
PubMedDate not supplied

Determination of sample time for T1 measurement.

In spin-lattice relaxation time measurements, the relaxation time T1 is estimated from measuring the longitudinal magnetization during its return to thermal equilibrium from an initial (nonequilibrium) state. T1 estimation error depends on a number of factors, including the sample spacing, number of sample points, target T1 range, etc. We describe here a sample-time determination method based on the principles of optimal experimental design. A two-parameter model and a more general three-parameter model of the general T1 measurement experiment are used in this study. Both linear and power-law sample spacing strategies are evaluated. The proposed method formulates the sample-time determination problem in closed form expressions that allow for easy calculation of optimum sample times, if a prior T1 estimate or a probable T1 distribution over the target range is given. Valuable insights can be gained from evaluation of these expressions concerning the relationship of T1 estimation error and the sample spacing, number of sample points, target T1 range, etc.

Humans↗