A flow calorimetric method of determining electron beam energy.

The construction of an adiabatic flow calorimeter using water as the working substance is described. It is shown that at high dose rates the heat defect due to chemical reactions in water is small (of the order of 0-3%) and that under high dose rate conditions flow calorimetry can be used as a method of measuring the energy of high intensity electron beams. Measurements made with a 15 MeV linear accelerator are reported and compared with magnetic measurements.     

A rapid method for electron microscopic examination of blood cells.

A method is described whereby the time required for the processing of white blood cells for electron microscopy can be shortened from 36 to 3 1/2 hours. Because cells of the peripheral blood are not attached to each other, fixation, dehydration, and infiltration of the embedding medium is more rapid. This makes it possible for clinicians to use fine structural data for diagnosis as illustrated in three cases.     

A rapid method for reprocessing paraffin sections for diagnostic electron microscopy

A rapid method for re-embedding paraffin sections into epoxy resin for diagnostic electron microscopy is described. The method requires a relatively shorter time than the traditional block retrieval technique and produces a reasonable retrieval technique and produces a reasonable quality of ultrastructure for diagnostic purposes.     

Daily check instrument for photon and electron beam quality assurance of medical linacs

An instrument for daily beam checks of medical accelerators is described. Using three silicon diodes, the instrument provides information about calibration, beam symmetry, flatness, and energy variation for both photon and electron beams. Operating characteristics of the instrument and the electronic circuit design permit simple and reliable measurements.     

A fast non-invasive beam check for mammography x-ray units

A prototype instrument is presented for the indirect evaluation of the main physical parameters characterizing a mammographic x-ray beam. The instrument consists of an x-ray probe with four filtered solid-state detectors connected to a signal-conditioning electronic circuitry and a high-speed digitizer interfaced to a portable personal computer. The system, governed by an ad hoc developed software, can measure kVp, kV waveform, ripple, HVL, exposure time and exposure in a single shot of the x-ray beam with good accuracy. The system should prove very useful to any quality-control programme for mammography.     

A direct method to determine the electron energy spectrum of a 4 MeV linear accelerator beam

The most fundamental characterisation of the electron beam of a linear accelerator is the distribution of incident electrons differential in energy, angle and position. The simplest way to determine an electron spectrum would be to use a scintillation detector. However, the amount of electrons produced in the accelerator is too high to be counted in such a detector. One way to overcome this problem is to reduce the electrons to an extent that is suitable for the detector, without affecting, the electron spectrum. This paper describes such a procedure and presents an electron spectrum from a linear accelerator. Parameters from the obtained energy spectrum were compared with results obtained from normal depth dose curves. The results show good agreement of the mean and the most probable energies between the two methods.     

全身皮肤电子线放疗中快速确定机架角度的方法

目的：为双机架角多野全身皮肤电子线放疗技术提供一种快速确定机架角度的方法。方法：引入一个与治疗时辐射场几何条件关联的新因子F,F与机架角度、准直器大小和源皮距相关。查阅以往相关文献,归纳总结出不同几何条件下因子F的规律,然后建立根据F快速推算机架角度的方法,再用两组试验验证该方法的有效性。结果：分析以往文献中的数据后发现,因子F的值稳定在一个固定值左右,F的平均值为0.79,标准差为0.05。新建立的快速计算方法可将机架角度搜索范围从一般方法推荐的15°缩小到5°左右。在两组试验中,最佳照射时的机架角度均能快速而准确地确定。结论：在双机架角多野全身皮肤电子线放疗技术中,因子F的引入和新的计算方法能够有效提高确定照射机架角度的效率。     

Detecting electron beam energy shifts with a commercially available energy monitor

Routine electron beam quality assurance requires an accurate, yet practical, method of energy characterization. Subtle shifts in beam energy may be produced by the linac bending magnet assembly, and the sensitivity of a commercially available electron beam energy-monitoring device for monitoring these small energy drifts has been evaluated. The device shows an 11% change in signal for a 2 mm change in the I50 energy parameter for low energy electron beams (in the vicinity of 6 MeV) and a 2.5% change in signal for a 2 mm change in the I50 energy parameter for high energy electron beams (in the vicinity of 22 MeV). Thus the device is capable of detecting small energy shifts resulting from bending magnet drift for all clinically relevant electron beams.     

Wide-field electron microscopy. A rapid method for the study of histologic material that provides a bridge between light and electron microscopy.

Wide fields of tissue can be rapidly examined by electron microscopy by use of Formvar films for the support of ultrathin sections on slot grids. The intervention of the grid bars of conventional mesh grids is avoided, and a continuous micrograph of the specimen at scanning magnifications can be obtained. Enough material is sublimed from the section and the supporting film by deliberate exposure to the electron beam to permit one to obtain an image with good contrast. This method of examination, which takes in all about two hours, permits examination of an extensive area of tissue in relation both to its topography at low magnifications and to its ultrastructural detail, and accordingly adds to electron microscopy a dimension characteristic of the lower powers of the light microscope. It offers the histopathologist the option of using micrographs taken during the scanning survey of a tissue to detect regions that can be readily re-examined at high magnification in the same ultrathin section.     

A numerical method for electron transport calculations.

A numerical algorithm for calculating the penetration of electrons in dense media is presented. The numerical algorithm is intended for future application to radiotherapy dose calculations. The method is generic in the sense that it may be used with different theoretical models describing the angular scattering of electrons with depth. It is also general enough that it may be applied to electron dose calculations in heterogeneous as well as homogeneous media. The assumptions used in the algorithm are examined and equations describing the evolution of the distribution of electrons with depth are presented. Calculations have been performed for 10 MeV broad beams and pencil beams incident on water. It is shown that the Fermi-Eyges analytical solutions are recovered if the angular scattering process is assumed to be a Gaussian Markov process and the cumulative angle of electron travel remains small. In the case where the small angle approximation is not imposed, the numerical method qualitatively reproduces, at large depths, the wide angle scattering 'tails' seen in Monte Carlo generated profiles.     

Verification data for electron beam dose algorithms.

The Collaborative Working Group (CWG) of the National Cancer Institute (NCI) electron beam treatment planning contract has performed a set of 14 experiments that measured dose distributions for 28 unique beam-phantom configurations that simulated various patient anatomic structures and beam geometries. Multiple dose distributions were measured with film or diode detectors for each configuration, resulting in 78, 2-D planar dose distributions and one, 1-D depth-dose distribution. Measurements were made for 9- and 20-MeV electron beams, using primarily 6 x 6- and 15 x 15-cm applicators at several SSDs. Dose distributions were measured for shaped fields, irregular surfaces, and inhomogeneities (1-D, 2-D, and 3-D), which were designed to simulate many clinical electron treatments. The data were corrected for asymmetries, and normalized in an absolute manner. This set of measured data can be used for verification of electron beam dose algorithms and is available to others for that purpose.     

Betatron electron beam characterisation for dosimetry calculations.

Parameters have been specified for electron beams with energies 5--45 MeV from a Brown Boveri betatron for use in computerised dosimetry calculations. A semi-empirical equation is given for the dose at any point at various depths in water. This equation is a modification to Kawachi's predictive model which was based on solutions of a general age--diffusion equation. The depth doses and isodose curves are predicted as a function of the practical range, source skin distance (SSD) and field size. Depth dose accuracy requirements of +/-2% above 50% depth dose and +/-5% at lower doses, relative to maximum dose, have been set and achieved. Also, the shape of the isodose curves with the constrictions at higher doses and bulging at lower values are accurately predicted. Computer calculated beams have been used to generate summed isodose distributions for certain clinical situations.     

A rapid method for purification of herpesvirus DNA.

A rapid and reliable method for purification of herpesvirus DNA from cell cultures is described. The method is based on the isolation of virus particles and/or nucleocapsids by differential centrifugation and exploits the solubilizing and denaturing capabilities of cesium trifluoroacetate during isopycnic centrifugation, so that phenol/chloroform extractions can be omitted. The method was used for the purification of DNA from several members of the Alfaherpesvirinae subfamily.     

A rapid method for reading migration inhibition tests.

This article describes how the extent of cell-migration can be read directly using the Field iris of a microscope.