[en] External supervoltage radiation is now an accepted form of treatment for adenocarcinoma of the prostate but the tumor response cannot be predicted. We hope in the future that accurate clinical staging coupled with a biological staging of the tumor cells with catalase activity will enable us to predict this response. Ionizing radiations act by producing active radicals, hence the rationale of studying the tissue catalase activity in conjunction with the histological grading may provide a more accurate index of patients who would gain the most benefit from radiotherapy

[en] The study demonstrates that the sensitivity of endothelial cells to irradiation in vitro is significantly affected by the microenvironmental conditions under which the experiment is carried out. When irradiated plateau phase bovine aortic endothelial cells were assayed for colony formation on top of uncoated plastic of standard culture dishes, the dose survival curves showed Do values of [mean(S.D.)]107(6) cGy and Dq of 63(28) cGy (calculated according to the single-hit multitarget model). When assayed in dishes precoated with the autologous natural basement membrane-like extracellular matrix (BAEC/ECM), the curves showed a similar Do [106 (2) cGy], but the Dq was 194 (8) cGy, indicating that components of natural ECM confer in endothelial cells an improved capacity to repair radiation lesions and to restore the clonogenic capacity. However, when the natural but biologically unrelated HR9-bFGF/ECM was used, a decreased repair capacity was noted with Dq of 156(30) cGy (P <0.05 compared with BAEC/ECM). The data demonstrate the high specificity of the repair function to interactions with autologous matrix components, and emphasise the need to select relevant experimental conditions when parameters of the radiation response in vitro are used to predict the response in vivo. (Author)

[en] Vibroacoustic behaviour of a power transformer was characterized prior to employing active noise control (ANC) to control transformer noise. The effect of changes in temperature and loading conditions on the vibration pattern of the transformer tank received particular attention. The transformer quieting technology has been developed and implemented by QuietPower Systems of New York and Noise Cancellation Technologies Inc., of Maryland. Results of the study will be used to ensure that actuator placement is appropriate for each of the seasons experienced throughout the year, as well as to build boundary element and finite element models of the tank vibration and the associated radiated noise. Boundary element results show that the first four harmonics are the primary contributors to radiated noise. The finite element model used to examine the modal response of the tank structure showed high modal densities, even around the lower order harmonics (120 Hz). This can be interpreted to mean that statistical techniques normally associated with high frequency noise problems may be applicable here because of the high modal density. Results of the completed summer and winter measurements permit an evaluation of the effects of loading conditions, temperature and other environmental factors on transformer noise. Appendix B contains the results of numerical simulations on a 250 MVA transformer. 3 refs., 72 figs., 2 appendices

[en] Background: Fluoroscopy during endoscopic retrograde cholangiopancreatography (ERCP) has a logarithmic relationship with radiation exposure, and carries a known risk of radiation exposure to patients and staff. Factors associated with prolonged fluoroscopy duration have not been well delineated. Objectives: To determine the specific patient, physician and procedural factors that affect fluoroscopy duration. Methods: A retrospective analysis of 1071 ERCPs performed at two tertiary care referral hospitals over an 18-month period was conducted. Patient, physician and procedural variables were recorded at the time of the procedure. Results: The mean duration of 969 fluoroscopy procedures was 4.66 min (95% CI 4.38 to 4.93). Multivariable analysis showed that the specific patient factors associated with prolonged fluoroscopy duration included age and diagnosis (both P<0.0001). The endoscopist was found to play an important role in the duration of fluoroscopy (ie, all endoscopists studied had a mean fluoroscopy duration significantly different from the reference endoscopist). In addition, the following procedural variables were found to be significant: number of procedures, basket use, biopsies, papillotomy (all P<0.0001) and use of a tritome (P=0.004). Mean fluoroscopy duration (in minutes) with 95% CIs for different diagnoses were as follows: common bile duct stones (n=443) 5.12 (3.05 to 4.07); benign biliary strictures (n=135) 3.94 (3.26 to 4.63); malignant biliary strictures (n=124) 5.82 (4.80 to 6.85); chronic pancreatitis (n=49) 4.53 (3.44 to 5.63); bile leak (n=26) 3.67 (2.23 to 5.09); and ampullary mass (n=11) 3.88 (1.28 to 6.48). When no pathology was found (n=195), the mean fluoroscopy time was 3.56 min (95% CI 3.05 to 4.07). Comparison using t tests determined that the only two diagnoses for which fluoroscopy duration was significantly different from the reference diagnosis of 'no pathology found' were common bile duct stones (P<0.0001) and malignant strictures (P<0.0001). Conclusions: Factors that significantly affected fluoroscopy duration included age, diagnosis, endoscopist, and the number and nature of procedures performed. Elderly patients with biliary stones or a malignant stricture were likely to require the longest duration of fluoroscopy. These identified variables may help endoscopists predict which procedures are associated with prolonged fluoroscopy duration so that appropriate precautions can be undertaken. (author)