The magnetic resonance (MR) images of the knees and hips of children with systemic diseases involving bone marrow were correlated with their marrow histology and compared with the images of asymptomatic normal children. In normal children the intensity of the MR signal from the bone marrow of the knees and hips was uniform throughout the metaphyses and diaphyses. In contradistinction the MR signal was uniformly diminished for the hypercellular marrow of patients with sickle cell anemia, was similar to normal for the hypocellular hyperfatty marrow of untreated aplastic anemia, and was nonuniform and patchy for leukemic marrow.

Adolescent↗

PubMedDate not supplied

Focal spot size measurements with pinhole and slit for microfocus mammography units.

Many mammography units now have microfocal spots ranging in size from 0.09 to 0.4 mm for magnification radiography. On site measurements of these focal spots are not possible without invasive procedures if National Equipment Manufactures Association (NEMA) specifications are to be followed. This paper describes a method to perform such measurements expeditiously (1.5 h) and noninvasively. We describe how this method differs from NEMA test specifications, and report the test results of 22 units from ten manufacturers. Six of the focal spots were larger than the manufacturer's specifications which were based on current NEMA standards. Emphasis is placed on the need for verifiable standards for mammography x-ray systems.

Female↗

PubMedDate not supplied

A review of mammography test objects for the calibration of resolution, contrast, and exposure.

Mandated and voluntary accreditation and quality control programs for mammography require the use of standardized mammography test objects. We evaluated eleven commercially available test objects and three prototype test objects, comparing them with respect to their resolution targets, contrast targets, and the dose they required when imaged by the same automatic exposure meter. Ion chamber and/or thermoluminescent dosimeter measurements of exposure were made with each test object, while attenuation was measured for seven. Measurements of dosage using acrylic (5 test objects) and tissue equivalent epoxy (9 test objects) showed as much as a 400% variation in the radiation supplied by the same automatic exposure device when differences in thicknesses of test objects were normalized. Speck visibility was as dependent on the composition of the specks and of the surrounding material as on the size of the specks. Contrast targets were adequate in only three test objects. Optical density differences between images of a 4-cm-thick breast and of different test object materials, also 4 cm in thickness, exposed to the same radiation, imply that untested acrylic or epoxy resin materials should not used in the calibration of automatic exposure controls.

Evaluation Studies as Topic↗