The pulsatility curve : the relationship between mean intracranial pressure and pulsation amplitude

The amplitude of cardiac-related pulsations in intracranial pressure has recently been suggested as useful for selecting patients for shunt surgery in hydrocephalus. To better understand how shunting affects these pulsations, we aim to model the relationship between mean pressure and pulsation amplitude in a wide range, including low pressures typically found after shunt surgery. Twenty-five patients with probable idiopathic normal pressure hydrocephalus were examined with lumbar constant pressure infusion investigations including drainage of cerebrospinal fluid. Mean pressure and pulsation amplitude were determined for consecutive 1.5 s intervals, starting at peak pressure (ca 35 mmHg), after infusion, continuing during spontaneous return to baseline and drainage to 0 mmHg. The amplitude versus pressure relationship revealed a linear phase at higher pressures (14-32 mmHg, lack of fit test: p = 0.79), a transitional phase and an essentially constant phase at low pressures (0-10 mmHg, slope = -0.02, lack of fit test: p = 0.88). Individual patients' baseline values were found in all three phases. The model and methodology presented in this paper can be used to preoperatively identify patients with potential for postoperative amplitude decrease and to predict how much the amplitude can be reduced

EPR dosimetry intercomparison using smart phone touch screen glass

This paper presents the results of an interlaboratory comparison of retrospective dosimetry using the electron paramagnetic resonance method. The test material used in this exercise was glass coming from the touch screens of smart phones that might be used as fortuitous dosimeters in a large-scale radiological incident. There were 13 participants to whom samples were dispatched, and 11 laboratories reported results. The participants received five calibration samples (0, 0.8, 2, 4, and 10 Gy) and four blindly irradiated samples (0, 0.9, 1.3, and 3.3 Gy). Participants were divided into two groups: for group A (formed by three participants), samples came from a homogeneous batch of glass and were stored in similar setting; for group B (formed by eight participants), samples came from different smart phones and stored in different settings of light and temperature. The calibration curves determined by the participants of group A had a small error and a critical level in the 0.37-0.40-Gy dose range, whereas the curves determined by the participants of group B were more scattered and led to a critical level in the 1.3-3.2-Gy dose range for six participants out of eight. Group A were able to assess the dose within 20 % for the lowest doses (<1.5 Gy) and within 5 % for the highest doses. For group B, only the highest blind dose could be evaluated in a reliable way because of the high critical values involved. The results from group A are encouraging, whereas the results from group B suggest that the influence of environmental conditions and the intervariability of samples coming from different smart phones need to be further investigated. An alongside conclusion is that the protocol was easily transferred to participants making a network of laboratories in case of a mass casualty event potentially feasible