Evaluation of hippocampus dose for patients undergoing intensity-modulated radiotherapy for nasopharyngeal carcinoma.

OBJECTIVE: To evaluate the dose received by the hippocampus among patients undergoing intensity-modulated radiotherapy (IMRT) for nasopharyngeal cancer. METHODS: 10 patients with biopsy-proven, locally advanced nasopharyngeal cancer constituted the study population. The total prescribed dose to the planning target volume (PTV) was 70 Gy (D95%) delivered in 2.12-Gy daily fractions using IMRT. Using established anatomical guidelines, MRI co-registration and the assistance of a board-certified neuroradiologist, the right and left hippocampi were delineated on axial imaging from the CT scan obtained at simulation for each patient beginning at the most anterior portion of the lateral ventricle. IMRT treatment plans were generated without dose-volume constraints to the hippocampus. A range of dose-volume statistics was calculated. RESULTS: The mean hippocampus volume was 6.01 ± 2.61 cm(3). The mean V20 was 72.2%; V40 was 22.0%; V50 was 10.2%; and V60 was 5.5%. The average mean, minimum and maximum hippocampus doses were 30.27 Gy (range, 19.08-47.99 Gy); 17.54 Gy (range, 11.66-33.17 Gy); and 54.95 Gy (range, 35.59-75.57 Gy), respectively. The hippocampus received a maximum dose exceeding 70 Gy in 30% of cases. CONCLUSION: Our dosimetric analysis suggests that, for patients undergoing IMRT for nasopharyngeal cancer, the hippocampus routinely receives significantly high doses. ADVANCES IN KNOWLEDGE: The hippocampus receives a fair amount of incidental radiation during treatment for nasopharyngeal cancer. Given the importance of this structure with respect to memory and neurocognitive function, consideration should be given to identifying the hippocampus as a critical organ at risk in the IMRT optimization process.

Study of genotoxicity and antigenotoxicity of the Cotinus coggygria Scop. methanol extract by Drosophila melanogaster sex-linked recessive lethal test.

The genotoxic and antigenotoxic effects of Cotinus coggygria Scop. methanol extract was investigated using the Drosophila sex-linked recessive lethal (or SLRL) test. The results presented here show that the methanol extract of Cotinus coggygria in a concentration of 5% and artificial chemical agent ethyl methanesulfonate EMS (0.75 ppm) induce recessive lethal mutations on X-chromosome on Drosophila melanogaster in all broods (I, II and III). Post-treatment with lower concentration of the methanol extract of Cotinus coggygria (2%) was effective in reducing genotoxicity ofmutagen.

Quantitative schlieren visualization.

Using a closed circuit television camera (CCTV), a method is developed to obtain quantitative sound pressure measurements directly from the sound field imaged in a schlieren system. By using the exact time format of the composite video signal and a series of time delay circuits, it is possible to take vertical intensity scans of a schlieren image at any position on the TV raster. The method uses the camera's horizontal blanking pulse to trigger a broadband, high-speed sample-hold amplifier. This amplifier is triggered to sample each horizontal scan line at a selected time in the horizontal scan sweep and to feed this value into a transient recorder. The signal is digitized, and a continuous analog voltage signal corresponding to the black-white information from a schlieren image is displayed on a scope. The same analog signal is also plotted on an X-Y recorder. The schlieren system can be operated using only a single calibration curve at each frequency. The curves plotted applied transducer voltage against the video output level. Thus, by comparing the video output levels for several vertical image intensity scans on a schlieren image, relative sound pressure measurements are routinely obtained.