On 11 December 1991, a radiation overexposure occurred at an industrial radiation facility in Maryland. The radiation source was a 3-MV potential drop accelerator designed to produce high electron beam currents for materials-processing applications. This accelerator is capable of producing a 25 milliampere swept electron beam that is scanned over a width of 112.5 cm and which emerges from the accelerator vacuum system through a titanium double window assembly. During maintenance on the lower window pressure plate, an operator placed his hands, head, and feet in the beam. This was done with the filament voltage of the electron source turned "off," but with the full accelerating potential on the high voltage terminal. The operator's body, especially his extremities and head, were exposed to electron dark current. In an attempt to reconstruct the accident, radiochromic film and alanine measurements were made with the accelerator operated at two beam currents. Measured dose rates ranged from approximately 40 cGy s-1 inside the victim's shoe to 1,300 cGy s-1 at the hand position. Approximately 3 mo after the accident, it was necessary to amputate the four digits of the victim's right hand and most of the four digits of his left hand. Electron paramagnetic resonance spectrometry, which measures the concentration of radiation-induced paramagnetic centers in calcified tissues, was used to estimate the dose to the victim's extremities. A mean dose estimate of 55.0 +/- 3.5 Gy (95% confidence level) averaged over the mass of the bone was obtained for the victim's left middle finger (middle phalanx).

Removal of Ca++ from the solutions bathing the frog gastric mucosa results in an initial increase in resistance (first phase) and a subsequent marked decrease in resistance (second phase). During the first phase the H+ secretory rate is decreased by 39% and the potential difference (PD) by 10%. During the second phase the measured H+ rate decreased to zero and the PD to near zero. Anoxia or DNP, which ordinarily produce a marked increase in resistance, failed to do so in the absence of Ca++. Comparable effects of Ca++ removal are found with Cl–-free bathing solutions. Replacement of Ca++ to the secretory solution on the nutrient side reversed these effects. Addition of Ca++ to the secretory solution readily reversed the second phase but only partly reversed the first phase. The inability of Ca++ on the secretory side in contrast to Ca++ on the nutrient side to reverse completely the first phase indicates that the secretory membrane may be much less permeable to Ca++ than the nutrient membrane.

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The estimation of fetal dose incurred by patients undergoing various radiologic procedures can be very perplexing. The problem is especially critical for women who do not know that they are pregnant at the time of x-ray exposure. A desciption is offered of efforts to quantitate the fetal dose by after-the-fact calculations. Such conservatively employed calculations may be essential for a clinical decision regarding therapeutic abortion.