A general method to calculate dose to spine in opposing anterior posterior treatment setup without CT

The spinal cord is usually part of the treatment volume in the treatment of the thorax and abdomen areas using antero-posterior (AP) and postero-anterior (PA) ports. Thus it is necessary to know the dose the spinal cord would receive. One needs to locate the spine to calculate the dose at that location. In the absence of CT, a set of orthogonal films is taken at simulation to aid in locating the spine. The relative point dose then is calculated using irregular field point dose calculation mode of the treatment planning system. The data needed for the calculation are the x and y coordinates of the spine in the coronal plane, air gap, and depth in tissue. Correct entry of these is thus important to obtain the dose accurately. Planning systems assume that the spine is close to the beam axis. There could be possible mislocation of the spine when this assumption is not valid. This presentation describes a procedure to obtain the needed numbers for a general location without any assumptions. To obtain x and y coordinates the suggestion is made to solve numerically using successive approximation series for the coordinates, the series continued until mutually consistent values are obtained. The other parameters, g and d, are obtained from the source to skin distance (SSD) above the spine point, with the use of multiple transaxial contours in association with the principle of linear interpolation.(ABSTRACT TRUNCATED AT 250 WORDS)

Temperature dependence of the electron spin-lattice relaxation rate from pulsed EPR of CUA and heme a in cytochrome c oxidase

This work shows the feasibility of using pulsed, saturation recovery EPR to study directly the magnetic relaxation properties of metal centers in cytochrome c oxidase in the 1.5-20 K range. Heme a and CuA both showed remarkably similar Tn temperature dependences in their spin-lattice relaxation rates. Either both are in environments with very similar protein backbone configurations (Stapleton, H.J., J.P. Allen, C.P. Flynn, D.G. Stinson, and S.R. Kurtz, 1980, Phys. Rev. Lett., 45:1456-1459; Allen, J.P., J.T. Colvin, D.G. Stinson, C.P. Flynn, and H.J. Stapleton, 1982, Biophys. J., 38:299-310), or the CuA is relaxed by nearby heme a. Spin-lattice relaxation of the nitrosylferrocytochrome a3 center in mixed valence oxidase showed enhancement of relaxation by a nearby paramagnetic center, most likely heme a.

Perfluorinated organic liquids and emulsions as biocompatible NMR imaging agents for 19F and dissolved oxygen

Emulsions of fluorocarbons are finding considerable use in physiology for intravascular oxygen transport. Their wide clinical application as blood substitutes, anti-shock, and anti-ischemic agents seems imminent. Whole body NMR imaging is rapidly gaining clinical application and may one day almost completely supplant X-ray imaging. All of the 19F compounds used in biocompatible fluorocarbon emulsions give 19F signals identical to those in the corresponding neat liquid. In concentrations of 10% w/v they are readily imaged. The paramagnetic oxygen molecule reduces T1 in such a way as to make possible whole body imaging of oxygen. T1 typically decreases from 1-4 to 0.3-0.5 seconds and is an inverse linear function of oxygen tension. Spin-lattice relaxation times versus oxygen tensions from 0 to 600 torr have been obtained for F-decalin, F-tributylamine, and F-44E. The usefulness of these 19F effects in clinical NMR imaging depends upon the sensitivity of the method and the tolerable dose. The 19F signal may find use in monitoring 19F compounds as vapors or gases dissolved in plasma or in perfluorocarbons in neat liquid or particle form.

Effects of ozone on meiotic chromosomes of Vicia faba

All of the levels of ozone used in these experiments caused morphological damage to plants of Vicia faba L., but only the dose of 200 parts per hundred million for 4 h or 8 h caused chromosomal damage in the microsporocytes. Significant chromosomal damage appeared 24 h after fumigation in metaphase I and anaphase I - telophase I but no significant damage was found in anaphase II - telophase II. This observation suggests that chromosomes are more susceptible to ozone during early stages of meiosis than at later stages. Chromosomal damage was of two types: physiological, as suggested by chromosome stickiness and physical, as indicated by bridges, fragments, and micronuclei.