The effect of geometric and recording system unsharpness in mammography.

Modulation transfer functions (MTFs) and test object radiographs were used to study the effect of geometric and recording system unsharpness in mammography with the CGR Senographe x-ray unit. Results show that geometric unsharpness can be a significant factor in the detection of microcalcifications within the breast, depending on the size and shape of the focal spot, the focal spot-to-recording system distance, and the object-to-recording system distance (o.r.d.). A new recording system for mammography, the DuPont Lo-dose system, requires approximately 1/15th the exposure of a direct x-ray film, such as Kodak RP/M, to provide mammograms with comparable photographic density. With the Lo-dose system, geometric unsharpness can be reduced by use of a specially designed long cone with an increased focal spot-to-recording system distance. This cannot be accomplished with direct x-ray films because the x-ray unit is operating at near-maximum output conditions even when short cones are used. Although direct x-ray films have a higher resolution than the Lo-dose system, at certain o.r.d.s total resolution is found to be affected more significantly by geometric unsharpness than by the Lo-dose recording system. In several cases, clinical results show improved detection of microcalcifications at larger o.r.d.s by the Lo-dose system with a long one, combined with a reduction by a factor of 15 in patient exposure.

The radiographic manifestations of pseudolymphoma of the stomach.

Pseudolymphoma of the stomach is a benign proliferation of lymphoid tissue which can be mistaken histologically for malignant lymphoma. The etiology is unknown but in most cases it is believed to be a reaction to chronic peptic ulcer disease. The clinical records and radiographs of 18 patients with pseudolymphoma of the stomach were reviewed. The radiographic findings fell into 3 relatively distinct groups: tumor masses, enlarged gastric rugae, and well-defined benign-appearing ulcers. All but 2 cases demonstrated ulcers radiographically and all cases had ulcers or erosions on pathological examination.

Splenic mobility and its effect on estimates of splenic mass.

In 47 patients the posterior radionuclide views of the spleen in supine and prone positions were evaluated for difference in splenic contour and calculated splenic weight as the patient's position was changed from supine to prone. A significant change in splenic contour was found in almost 50% of the cases. Values for the mass of the spleen varied by a mean of 36% with a range of plus 195 to minus 79%. The differences are attributed primarily to changes in the position of the spleen and liver within the abdomen.

The effect of x-ray spectra from molybdenum and tungsten target tubes on image quality in mammography.

The measured x-ray spectra from a molybdenum anode Senographe mammography unit and a tungsten anode unit were used to calculate the x-ray energy spectra transmitted through various thicknesses of fat and water (breast-equivalent materials). The dependence of subject contrast and patient exposure on (a) x-ray spectra, (b) attenuation properties of two breast-equivalent materials, and (c) thickness of breast-equivalent material was predicted. Radiographs of resected breast tissue confirmed these predictions and demonstrated the general relative effects of x-ray beam quality on image contrast in mammography.

Distribution of hypertrophic pulmonary osteoarthropathy.

Radionuclide bone scanning is a sensitive detector of new bone formation. It offers the possibility of more complete description of the distribution of hypertrophic pulmonary osteoarthropathy. The scintigraphic findings in 48 confirmed cases of hypertrophic pulmonary osteoarthropathy (HPO) are described. Several new observations about the involvement of bones and distribution pattern have been made: the skull (mandible and/or maxillae) was involved in 42% of cases, the scapulae in 67%, and the patellae in 50%. Clavicles were involved in 33% of cases. With the exception of the humerus, the proximal and distal portions of each long bone were involved with equal frequency. Involvement of the extremities was invariably present, and disease almost always appeared more active in the lower than in the upper extremities. Asymmetric involvement of the extremities was noted in 17% of cases, and there was irregular involvement in 15%. Differentiation of metastatic disease from HPO by bone scanning is generally not difficult, since the most frequent patterns of distribution of these two conditions are entirely different.