Epidemiologic impact of water reuse in Los Angeles County

The importance of recycled wastewater in the pathogenesis of disease has been considered in an ecologic analysis of four geographic areas of Los Angeles County. Two of the areas received recycled wastewater via the groundwater since 1962, while two similar areas served as controls. Of 19 health outcomes included in the analyses, five exhibited statistically significant differences among four areas. In none of these five analyses, however, were the differences in accord with the biologic hypothesis that recycled water causes disease. For only one outcome, deaths due to cancer of the rectum, were differences noted in which the high recycled water area had more excess deaths than the low recycled water area, and both had more excess deaths than the control areas. This positive association was of a low order, however, and might well have been due to chance (P = 0.08). The results of this first stage of our investigation suggest that as of 1969–1971, there were no grossly apparent adverse health effects associated with the use of recycled water. Nonetheless, a cautious interpretation of the study findings is necessary due to the inherent limitations of this type of analysis.     

Pulse sequence optimization for MR imaging using a paramagnetic hepatobiliary contrast agent

Paramagnetic agents enhance contrast between tissues in magnetic resonance (MR) imaging by altering tissue relaxation times. The effect of these changes on MR image intensity depends in part on the choice of operator-controlled pulse sequence parameters. With the newly described paramagnetic hepatobiliary contrast agent, iron(III) ethylenebis-(2-hydroxyphenylglycine), Fe(EHPG)-, an in vivo experimental analysis of pulse sequence optimization was performed on the rat. We compared the enhancement of the liver divided by background noise, EL/N, of standard inversion-recovery (IR) and spin-echo (SE) T1-weighted pulse sequences and several pulse sequences theoretically predicted to have improved EL/N. Optimization of the echo time (TE = TEmin) gave a substantial (greater than 60%) increase in EL/N over the standard IR and SE pulse sequences. Images obtained with optimized repetition rate and inversion time gave only a slight additional improvement. Within the uncertainties of our relaxation measurements, the measured changes in EL/N with pulse sequence optimization corresponded well with theoretical predictions. With the experimental and theoretical data, the importance of using a short echo time to obtain maximal T1 contrast in contrast-enhanced MR imaging and the relative merits of optimized SE versus IR pulse sequences for contrast-enhanced MR imaging are discussed.     

Repair of Tetralogy of Fallot after Aortopulmonary Anastomosis

Thirty-eight corrective operations have been performed in patients with tetralogy of Fallot and a functioning aortopulmonary shunt. There were 3 operative deaths (7.9%) and 1 late death (2.6%), and 3 patients have required reoperation for significant residual defects. Only 1 of 10 patients studied postoperatively by radionuclide scanning has a significant reduction in blood flow to the lung on the side of the closed shunt. We conclude that the presence of an aortopulmonary shunt does not add to the risk of repair in patients with tetralogy of Fallot and that mortality after such operations is related to the complex anatomy often present in patients of this group.