摘要:

In general, the dimensions of the effective focal spot of an x‐ray tube vary with tube current and voltage. This dependence on tube operating conditions has been noted in the literature but has not been investigated in detail. Star phantom measurements of seven focal spots for four x‐ray tubes operated at a variety of tube voltages and currents show that effective focal‐spot size varies asIV − 3 / 2. This dependence may be suppressed for the focal‐spot dimension perpendicular to the tube axis, however, because of auxiliary electrostatic focusing. Experimental data are presented with a theoretical explanation of the relationship between effective focal‐spot size and tube operating conditions.

ISSN:0269-3127    

DOI:10.1118/1.1637286

出版商:American Association of Physicists in Medicine    

年代:2003

数据来源: WILEY

摘要:

Clinical symptoms and performance were evaluated after shuttlebox‐trained miniature pigs received two 4400‐rad doses separated by time intervals of 10 − 4‐30 min. The doses were delivered to the head by 45‐MeV electrons from the AFRRI electron linear accelerator (LINAC). There was no significant difference in neurological symptons (Convulsions, coma, ataxia) or in performance after the second dose between animals that received the two doses 10 − 4or 0.3 min apart. As the time interval between doses was increased from 0.3 min, however, neurological symptoms declined and performance improved markedly after the second dose. When the doses were 30 min apart, the pigs showed no decrease in performance within the intial 30‐min postirradiation. It was concluded that more than physiochemical processes were involved in the increased radioresistance to the second dose of radiation.

ISSN:0269-3127    

DOI:10.1118/1.1637287

出版商:American Association of Physicists in Medicine    

年代:2003

数据来源: WILEY

摘要:

A collimator for exposures of portions of small animals to 15‐MeV neutrons is described. The radiation field behind the collimator was mapped with various detectors that determined dose, neutron spectra, and fluxes.

ISSN:0269-3127    

DOI:10.1118/1.1637288

出版商:American Association of Physicists in Medicine    

年代:2003

数据来源: WILEY

摘要:

Radiation‐induced thermally activated currents (RITAC) in ultra‐high‐purity dielectrics provide a radiation dosimetry technique which is practical for applications at room temperature and is much more sensitive than other more well known, solid state dosimetry effects. The essential requirement for producing high‐radiation‐sensitivity RITAC readout, either in polarization or conductance modes of operation, is selective purification of the dosimetry material. Simple methods exist for monitoring the active impurity levels for fabrication of highly sensitive reproducible RITAC effect devices.

ISSN:0269-3127    

DOI:10.1118/1.1637289

出版商:American Association of Physicists in Medicine    

年代:2003

数据来源: WILEY

摘要:

We show measurement of thermally stimulated conduction (TSC) in high‐purity sapphire to be a potentially useful technique for ionizing radiation dosimetry. The TSC thermogram, conduction current vs temperature or time, has current peaks that are proportional in height to irradiation. The peak height response to x rays is: (1) linear with doses from 10 mR to 100 R (60Co energy); (2) useful from 10 mR to 104R (60Co energy); (3) reusable with no additional treatment for exposures less than 1000 R; (4) exposure rate independent from at least 0.12 mR/sec to 3.2 R/sec; (5) stable; and (6) reasonably similar to tissue response as a function of energy. The stability of response, simplicity of instrumentation requirements, and dependable supply of materials at competitive price with other dosimetry systems favor application of this technique.

ISSN:0269-3127    

DOI:10.1118/1.1637290

出版商:American Association of Physicists in Medicine    

年代:2003

数据来源: WILEY

摘要:

A proportional gas counter and a radioisotope excitation source are used to demonstrate the simplicity and efficiency of the x‐ray fluorescence (XRF) method in quantitative analysis of blood iron.

ISSN:0269-3127    

DOI:10.1118/1.1637291

出版商:American Association of Physicists in Medicine    

年代:2003

数据来源: WILEY

摘要:

A simple, easily constructed extrapolation chamber is described for the calibration of Β‐ray applicators.

ISSN:0269-3127    

DOI:10.1118/1.1637292

出版商:American Association of Physicists in Medicine    

年代:2003

数据来源: WILEY

ISSN:0269-3127    

DOI:10.1002/j.2473-4209.1974.tb36049.x

出版商:Wiley    

年代:2003

数据来源: WILEY