PubMed Health⌕ Search

Biomedical subjects

D D Tolbert

Publications and source records attributed to D D Tolbert.

14 recordsLinked to original sources
PubMed1977

A tissue compensation source-to-skin measurement system.

An easy to use, low-cost system for measuring the source-to-skin distance used in determining tissue compensation requirements is described. These measurements can be performed with accuracy and precision for any treatment field size and at any treatment beam angle. The system can be used in conjuction with several different tissue compensation methods.

Humans↗
PubMed1975

Ultrasound B-scans for clinical evaluation of neoplastic neck nodes.

As an attemp to improve the quantitative and qualitative evaluation of neoplastic neck nodes, we are evaluating ultrasound B-scans. Clinical examples are presented to demonstrate how "B-scans" may be used to evaluate lymph node size and response to therapy. Qualitatively, such scans may also be of value as a means of establishing lymph node boundaries and position with respect to other neck structures.

Carcinoma, Squamous Cell↗
PubMed1975

Accessory beam flattening filter for the varian clinac-4 linear accelerator.

An accessory beam flattening filter (brass disk with critical angles) attaches to the shadow tray of the clinac-4 linear accelerator, intercepts the x-ray beam, and eliminates higher dose areas at the edges of large fields near the skin surface. This improves the x-ray beam dose distribution within the patient and results in a reduction of dose to normal tissues near the surface.

Radiotherapy, High-Energy↗
PubMed1975

A projection system for effective utilization of ultrasound echogram information in radiation therapy.

A system employing an opaque projector mounted on a steel-framed cart was constructed to provide full-scale enlargement of ultrasound echograms for use in radiation therapy planning. Anatomical outlines from the enlarged echograms are traced directly into a minicomputer. Life-sized isodose curves for a selected treatment plan are overlayed on the enlarged echogram to produce a permanent record for treatment field adjustments and retrospective analysis.

Humans↗
PubMedDate not supplied

Analysis of in vivo volume measurements obtained with diagnostic ultrasound.

A study was carried out to investigate the errors involved in obtaining volumes by means of ultrasound echograms and a small computer. The work was done on live pigs' kidneys (130-200 cm3). The errors include those associated with the scanner itself, those invloved in the interpretation of the contour boundaries, and those relating to the algorithms used to determine the volumes from the contours. An average deviation of 25.4 cm3 from actual volumes was found, while 58% of the measurements were within +/-10%. Computer programs allowing for the display of contours and intercepts of corresponding orthogonal scan planes were used to reanalyze the data resulting in an average deviation of 14.7 cm3 with 78% of the data resulting inan average deviation of 14.7 cm3 with 78% of the measurements with "/-10%.

Animals↗
PubMedDate not supplied

Characteristics of Clinac-18 wedged fields for 10-MV x rays.

The characteristics of wedged fields which affect their clinical use have been examined for the 10-MV x-ray beam from the Clinac-18. The methods used for obtaining and analyzing the wedged-field data are discussed. These characteristics have been examined in terms of (a) the wedge angle, (b) the variation of the wedge angle with field size, (c) the variation in the angle through which isodose curves between the approximate depths of 5 and 15 cm are turned relative to the central axis as a function of depth, and (d) the variation of wedge central-axis transmission factor with field size. Analysis of the data pertinent to these categories is presented for the 15-, 30-, 45-, and 60-deg wedges. In addition, the effect of the 60-deg wedge upon the position of maximum dose on the central axis was determined.

Particle Accelerators↗