PubMed · 10196671
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K H Chadwick. Mechanisms, dose-effect relationship. Recent data.. https://doi.org/10.1016/s0764-4469(99)80042-0
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A technique is described for treating inguinal nodes when using radiotherapy in the control of pelvic malignancies. A posterior photon field treats the pelvis. A wider anterior photon field treats pelvis and inguinal nodes. An anterior photon boost to nodes is delivered using asymmetric collimator jaws moved across center line. Advantages of this technique include simplicity of setup and treatment (a single isocenter is retained, and no transmission block is needed), minimal dose inhomogeneity, reduced dose to femoral necks reducing the risk of femoral fracture, low risk of nodal underdose, and elimination of dosimetric difficulties inherent in electron beam boosts.
A multileaf collimator (MLC) is compared with conformal blocks for delivering the boost phase of dose-escalated conformal prostate radiotherapy. When using conformal blocks, the volume of rectum irradiated to 90% (V90) is lower (1.4+/-1.3%, 1 SD) for a three-field plan with gantry angles 0 degree, 90 degrees, 270 degrees than for a six-field plan with gantry angles 50 degrees, 90 degrees, 130 degrees, 230 degrees, 270 degrees, 310 degrees (2.1 +/- 1.3%, P = 0.002). However, when using an MLC in which the leaves and wedge are oriented at right angles, V90 is higher (4.7 +/- 3.0%) for a three-field plan than for a six-field plan (2.7 +/- 1.6%, P=0.05). The larger increase in V90 for the three-field plan when changing from conformal blocks to MLC is mainly due to the limitation imposed upon the MLC orientation by the use of wedges.
Radioactive concentrations of (239 + 240)Pu and 238Pu were determined in rainwater samples collected at Badajoz (in a semi-arid zone in the south-west of Spain) from 1992 to 1996. Total plutonium deposition (including dry and wet deposition) was investigated during dry and wet periods. Anomalously high depositions of (239 + 240)Pu ((6.8 +/- 0.4) mBq/m2) and 238Pu ((2.2 +/- 0.2)mBq/m2) were found in the second-half of 1995. The 238Pu/(239 + 240)Pu activity ratio (0.32 +/- 0.04) obtained for that sample was higher than in global fallout.