Feasibility of automating the micronucleus assay.

The results of a feasibility study on the automation of the micronucleus assay in whole blood cultures of human lymphocytes are reported. The assay requires determination of the number of lymphocytes with micronuclei among the proliferating population. Using an in-house-assembled image analysis system, a prototype software package was developed that addressed two problems: micronuclei identification and discrimination of nonproliferating cells from proliferating lymphocytes (the only ones that can give rise to micronuclei). The results of manual verification of automated micronucleus scoring showed that 70% of all digitized micronuclei were extracted from the images and 90% of them were correctly classified and paired with a parent nucleus by an "affinity function". The discrimination between proliferating and nonproliferating cells was carried out by linear discriminant analysis of simple nuclear features extracted from Feulgen-stained cells. Among the Feulgen-stained nuclei that were identified by autoradiography as proliferating or not, 85% were correctly classified by a six-feature discriminant function.

Low-cost digital teleradiology systems.

The proliferation of digital imaging methods creates a need for systems that facilitate storage and retrieval of these images. Several low-cost systems with the capability to store, retrieve, and transmit digital images from the medical center to distant general-purpose desktop microcomputers over standard telephone lines were investigated. Using error checking and nonlinear gray scales, both bistable and gray scale display systems were able to transmit and reproduce diagnostic quality images. The major limitations are the lack of low-cost digital mass-storage devices and relatively slow transmission times.

Advantage of underweight.

Exposure measurements made during a diagnostic radiological study revealed that heavy set patients pay a higher price in absorbed dose than lighter people.

Absorbed dose in the presence of contrast agents during pediatric cardiac catheterization.

Administration of x-ray contrast agents during heart catheterization examination increases the absorbed radiation dose in tissue. To estimate the dose absorbed by the blood of children undergoing diagnostic heart catheterization and angiocardiography, a number of measurements and calculations were conducted. First, entrance and exit exposures to the patient were measured with thermoluminescent dosimeters calibrated for the diagnostic x-ray energy range. Second, a dose enhancement factor was calculated from mass energy absorption coefficients for various concentrations of the contrast media and at selected x-ray energies. Third, the dose enhancement factor was estimated from survival of peripheral blood lymphocytes suspended in varying concentrations of the contrast agent during exposure to graded doses of x-rays. Fourth, a mean absorbed dose to the patient's blood was calculated using (a) the dose enhancement factor determined above, (b) an estimate of the mean exposure in the irradiated body volume calculated from the entrance and exit exposure measurements, (c) an effective iodine concentration in the blood during the exposure time, and (d) a ratio correcting for the distribution and circulation of the blood. For eight pediatric patients monitored, absorbed doses to the blood ranged between 3 and 12 rad. These values were two to three times greater than the expected dose without administration of a contrast agent.