MCNPX estimates acceptably present activity levels of 46Sc and 60Co as confirmed by activity measurements, but underestimates activity for the rest of the neutron induced radionuclides in the wall. Activity measurements have revealed the inhomogeneity of wall concrete atomic composition since large differences in activity values were found in two near wall surface locations with similar neutron flux. Such inhomogeneity cannot be modeled with the program that considers the material composition homogeneous. Highest specific activities estimated in a 10 yr operation are under exemption limits and therefore the cyclotron vault can be discarded as radioactive waste.

No abstract

The dose-area product was higher with the digital system than with the conventional system in 13 of the 15 groups. To reduce the patient dose in vascular interventional radiology procedures, the training of personnel and the frequent use of conventional fluoroscopy and low-dose imaging are required.

Open-tip and liquid ion-exchanger microelectrodes were used to study the effects of cAMP (6mM, added to the serosal medium) on apical membrane potential (Em) and intracellular sodium, potassium, and chloride activities (alphaiNa, alphaiK, alphaiCl) in Necturus gallbladder under open-circuit conditions. Transepithelial potential difference (ETr) was also measured. In the presence of cAMP, alphaiCl fell from about 1.5 times its equilibrium value to a level that corresponded to electrochemical equilibrium across the apical and basolateral cell membranes. Under these conditions alphaiNa decreased and alphaiK increased, Em was unchanged and ETr increased from virtually zero to a small but significant serosal positive value. The cAMP-induced increase in alphaiK was abolished when Cl- -free incubation media were used. Addition of the Ca++-ionophore A23187 (0.5 microgram/ml) to the serosal medium had no effect on Em, ETr, or alphaiCl. When A23187 was added to the mucosal medium, Em and the basolateral membrane potential hyperpolarized by about 20 mV and an increase in the outwardly directed electrochemical driving force for Cl- was observed. These results indicate that cAMP inhibits coupled transapical Na-Cl entry into epithelial cells of Necturus gallbladder and suggest that this inhibition may not be mediated by an increase in intracellular Ca++ concentration.

The objective of this work was to estimate patient doses (dose-area product, organ dose, effective dose and entrance surface dose) for barium procedures. A total of 175 procedures, in 175 patients, for five different examination categories was analysed. Dose-area product was determined using a transmission ionization chamber. Organ dose and effective dose were assessed using a knowledge of the examination and the software. For all patients, the contribution of fluoroscopy to the total dose was greater than that from radiography. Dose-area product from double contrast barium enema, enteroclysis and intestinal tract procedures was higher than that obtained for the other procedures. The average effective dose was 1.04 mSv and 13.99 mSv for oesophageal tract and enteroclysis examinations, respectively. Entrance surface dose in the oesophageal tract was 16 mGy, 10 times lower than for the other four procedures. Patient dose reduction in barium procedures may be achieved by improved training of resident radiologists, senior radiologists and other specialists in radiation protection.