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P Sprawls

Publications and source records attributed to P Sprawls.

At least 19 recordsLinked to original sources
PubMed1996

Optimization of radiation dose and image quality in mammography: a clinical evaluation of rhodium versus molybdenum.

Mammography was done with a conventional molybdenum anode/filter combination and either a molybdenum/rhodium (Mo/Rh) or rhodium/rhodium (Rh/Rh) combination to compare the contrast characteristics and penetrating ability of the different techniques. Each pair was rated as being equal, one slightly better than the other, or one much better than the other. The "preferred" image was also selected. The entrance surface exposure and the mean glandular dose were determined for each exposure. Mo/Mo was compared with Mo/Rh in 26 patients and to Rh/Rh in 23. Mo/Mo was judged to produce better or equal contrast and penetration in all cases except one using the Mo/Rh combination. Mo/Rh was the preferred image only once and Rh/Rh not at all. In comparison to the conventional Mo/Mo technique, the average dose was reduced by approximately 25% with Mo/Rh and by 50% with Rh/Rh.

Electrodes↗
PubMed1996

Optimum processing of mammographic film.

Underprocessing of mammographic film can result in reduced contrast and visibility of breast structures and an unnecessary increase in radiation dose to the patient. Underprocessing can be caused by physical factors (low developer temperature, inadequate development time, insufficient developer agitation) or chemical factors (developer not optimized for film type; overdiluted, underreplenished, contaminated, or frequently changed developer). Conventional quality control programs are designed to produce consistent processing but do not address the issue of optimum processing. Optimum processing is defined as the level of processing that produces the film performance characteristics (contrast and sensitivity) specified by the film manufacturer. Optimum processing of mammographic film can be achieved by following a two-step protocol. The first step is to set up the processing conditions according to recommendations from the film and developer chemistry manufacturers. The second step is to verify the processing results by comparing them with sensitometric data provided by the film manufacturer.

Female↗
PubMed1992

AAPM tutorial. CT image detail and noise.

Two important characteristics of the computed tomographic (CT) image that affect the ability to visualize anatomic structures and pathologic features are blur and noise. Increased blurring reduces the visibility of small objects (image detail); increased visual noise reduces the visibility of low-contrast objects. Sources of blurring in CT include the size of the sampling aperture (which can be regulated by the focal spot size and the detector size), the size of the voxels, and the reconstruction filter selected. Noise is caused by the variation in attenuation coefficients between voxels. Use of small voxels and edge-enhancing filters helps reduce blurring and improve visibility of fine details. However, small voxels absorb fewer photons and therefore result in increased noise. Noise can be reduced by using large voxels, increasing radiation dose, or using a smoothing filter, but this filter increases blurring. An optimized protocol for a specific clinical study must take these physical principles into account and be adjusted to give proper balance among detail, low noise, and patient exposure.

Radiographic Image Enhancement↗
PubMed1988

The geometry of triple-balloon dilation.

Triple-balloon dilation (TBD) of a variety of luminal structures has been successfully, though infrequently, used. A mathematical model is presented for the selection of balloon sizes, and equations and tables are derived that allow the user to estimate more accurately the size of balloons needed for TBD of structures with large lumina. With TBD, an approximately circular lumen can be formed. Also, TBD allows smaller, higher-pressure balloons to be used instead of single, low-pressure, large balloons. However, multiple puncture sites may be required for TBD.

Angioplasty, Balloon↗
PubMed1987

60 minutes of MRI.

Explore the source record for details and available documents.

Appointments and Schedules↗
PubMed1984

Enhanced-image mammography.

A blurred-mass subtraction technique has been developed for mammography, which enhances small-object contrast and visibility throughout the breast area. The procedure is easy to implement and requires no additional exposure. Perception of low-contrast objects is improved by eliminating extreme light- and dark-image areas. Contrast of structures within certain portions of the breast is increased by compression into the high-contrast portion of the film characteristic curve. Detail visibility is also increased by the edge enhancement produced by this process. This paper describes the enhancement process and gives an analysis of its capabilities and limitations.

Breast Neoplasms↗
PubMed1984

Maternity lead apron.

A maternity lead apron that provides 1.0-mm lead-equivalent shielding to the fetus is described. Wearing this apron provides an 80% reduction in fetal exposure.

Female↗
PubMed1983

Grids in mammography.

A special soft-tissue grid reduced scattered radiation to the receptor and resulted in improved contrast and visibility of small structures to the degree that increased kVp could be used during screen-film mammography. The reduction in radiation to the skin that is associated with the more penetrating higher kVp technique more than compensated for the Bucky factor of the grid. This technique allowed for better penetration of the base of large, dense breasts without the use of vigorous compression. Results that were obtained with a faster (2X) film are also presented and discussed.

Female↗
PubMed1983

Enhanced image mammography.

A blurred mass subtraction technique has been developed for mammography that will enhance small object contrast and visibility throughout the breast area. The procedure is easy to implement and requires no additional exposure. Perception of low-contrast objects is improved by eliminating extreme light and dark image areas. Contrast of structures within certain parts of the breast is increased by compression into the high-contrast part of the film characteristic curve. Detail visibility is also increased by the edge enhancement produced by this process. This paper describes the enhancement process and gives an analysis of its capabilities and limitations.

Breast Neoplasms↗
PubMed1982

Effectiveness of CT in evaluating intrathoracic masses.

To compare the effectiveness of computed tomography (CT) with conventional radiography and conventional tomography for evaluating masses in the thorax, 168 masses, 154 of which were histologically verified, which had been examined with CT were reviewed. In 74 instances (44%) CT provided important additional information compared with conventional radiography. Compared to conventional tomography, CT added important information in 15 (23%) of 65 cases. In no case did CT fail to demonstrate pathology shown with the other two methods. Average radiation dose to the chest was 1.3 rad (0.013 Gy) with CT and 0.4 rad (0.004 Gy) with linear tomography. Although CT is associated with slightly greater radiation dose and cost, this review indicates it should be performed directly after plain film examination instead of conventional tomography when further investigation of an intrathoracic mass is indicated.

Adolescent↗
PubMed1978

A film changer for small animals.

A 70mm spot-film camera was modified for use in small-animal studies. The film is exposed directly by x rays and yields a high-quality image.

Animals↗