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Biomedical subjects

M G Ort

Publications and source records attributed to M G Ort.

8 recordsLinked to original sources
PubMed1977

Subtraction radiography: techniques and limitations.

Subtraction radiography permits the use of 7-10 times less contrast material than is required without subtraction techniques. The first-order, second-order, and composite mask techniques are described and evaluated. While the second-order technique gives more complete cancellation of common structures, the more commonly used first-order technique was found to be adequate for most clinical uses. The smallest change in contrast which can be detected using subtraction radiography is limited by inherent background film noise in the original radiographs and not by statistical fluctuations in the x-ray quanta.

Subtraction Technique↗
PubMedDate not supplied

Designing a wax phantom to simulate a flat tumor with diffuse edges.

A suitable was phantom was designed for evaluating various film techniques used in subtraction radiography. Holes are drilled in a slab of wax and filled with various concentrations of iodinated wax, producing disk-shaped regions with diffuse borders. The technical details of construction and a representative application are described.

Models, Structural↗
PubMedDate not supplied

Radiographic quality, tube potential, and patient dose.

Measurements were made to determine if there was an optimal kVp that would maximize radiographic contrast for various materials while minimizing average patient dose. Radiographs were made of a 17-cm-thick plexiglass phantom (to simulate a typical abdomen) with added regions of plexiglass, hydroxyapatite, and iodine with peak kilovoltages from 40 to 150 kVp and 2 mm A1 added filtration. Radiographs were also made of a 4-cm-thick plexiglass phantom to simulate a typical breast, with added regions of plexiglass, hydroxyapatite, and fat at a peak kilovoltage from 35 to 100 kVp and with 1 mm added filtration. For the thicker phantom it was found that the contrast per average absorbed dose for the added plexiglass, hydroxyapatite, and iodine increased by about 3, 2, and 0.4, respectively, when going from 50 to 150 kVp. Contrast was measured relative to a reference region on the phantom. Similar data for the thinner phantom showed an increase of about 35% in contrast per average absorbed dose for plexiglass and fat but a decrease by about 30% for hydroxyapatite as the kVp changes from 35 to 100 kVp.

Humans↗