Neutron dose precision using LiF TLD.
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Lithium↗
Biomedical subjects
G H Zeman
Publications and source records attributed to G H Zeman.
Xeromammographic automatic exposure termination.
A method of automatic exposure termination (AET) for xeromammography has been devised, significantly reducing the rate of repeat exposures due to poor choice of manual exposure factors. AET images are of good quality and are reliably produced. The concept of AET is based on the existence of an optimal transmitted exposure to the selenium plate, which is easily determined experimentally. In routine clinical xeromammography, a repeat rate of 20% was eliminated by the use of AET.
Mammography↗
Negative-mode soft-tissue xeroradiography.
Positive-mode xeroradiography is an excellent method of visualizing soft-tissue structures in mammography and other procedures; however, toner deletions over a large area may preclude adequate delineation of the soft tissues near high-density structures such as bone. Use of the negative mode in the development cycle provides excellent demonstration of the soft tissues without toner deletions and requires only about 70% of the exposure needed in the positive mode. Negative-mode images also exhibit greater changes in radiographic contrast than those observed with the positive mode. The extent of achilles tendon lacerations was shown particularly well by this technique.
Achilles Tendon↗
Evaluation of xeroradiographic image quality.
A theory of edge enhancement has been developed to describe xeroradiographic images of linear step objects. The theory is shown to give an accurate description of the relationship between edge enhancement, subject contrast, radiation exposure, selenium charging potential and developer bias potential. An optimal transmitted x-ray exposure exists which gives the maximum edge enhancement. For low contrast structures, this same optimal exposure was found to yield the most acceptable images as judged subjectively. This finding has led to the successful application of automatic exposure termination in mammographic examinations using xeroradiography.
Mammography↗
A circular test pattern for evaluating x-ray tube focal spots.
The design and use of a circular x-ray resolution test pattern is presented. This pattern is shown to yield equivalent focal spot dimensions equal to those obtained with the more commonly used star pattern. The advantage of using the circular pattern is that it obviates the necessity of positioning the pattern strictly along the x-ray beam central axis. A major source of experimental error in making focal spot measurements is therefore circumvented, especially in the case of x-ray tubes with a small target angle.
Mathematics↗
Asymmetric distribution of aspartate in ganglia and single neurons of Aplysia.
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Animals↗
Collimator misalignment in high energy therapy machines.
Measurements of the intensity distribution of a 60-Co beam revealed a significant field distortion caused by minor misalignment of the collimator assembly which was not detected by routine methods. Accurate monitoring of radiation intensity distribution and periodic visual inspection of collimators are suggested for early detection of this problem.
Absorptiometry, Photon↗