摘要:

Calculated results are presented for a variety of neutron spectra incident on a tissue‐equivalent phantom. The neutron spectra considered are those produced by 35‐ and 50‐MeV deuterons in a thick beryllium target and by 67‐MeV protons in a thick lithium target. Results are presented for the absorbed doses, LET spectra, cell‐survival probabilities, OERs, and RBEs as a function of position in the phantom. The cell‐inactivation calculations were carried out using the model of Katzet al. and parameters for T‐1 kidney cells. In the case of incident neutrons from 35‐MeV2H on Be, experimental and calculated absorbed‐dose data are compared as a function of position in the phantom and are shown to be in good agreement.

ISSN:0269-3127    

DOI:10.1118/1.1637278

出版商:American Association of Physicists in Medicine    

年代:2003

数据来源: WILEY

摘要:

The activity of red cells labeled with51Cr decreases exponentially due to elution of chromium from the cell and any random cell losses which may be present, and decreases linearly due to red‐cell senescence. Red‐cell survival data are fitted to the functiona(t) = ae − kt(1 − t / L), wherea(t)is the activity at timet,ais the initial activity,kis the exponential loss rate, andLis the cell lifetime. With many subjects,a, k, andLas well as the standard errors of the estimate of these parameters may be determined.

ISSN:0269-3127    

DOI:10.1118/1.1637279

出版商:American Association of Physicists in Medicine    

年代:2003

数据来源: WILEY

摘要:

The bremsstrahlung spectra from a 25‐MeV linear accelerator and a 19‐MeV betatron have been measured using a NaI(Tl) spectrometer system. The spectra show a low energy cut‐off at 0.6 and 0.4 MeV, respectively, and the maximum photon energies were 26.8 and 19 MeV, respectively. Cross sections, thin‐ and thick‐target photon spectra and total electron energy losses (collision and radiative) were computed using a digital computer for tungsten (Z = 74) and platinum (Z = 78) targets. The measured spectra were compared to the calculated spectra for thin and thick targets using electron kinetic energies of 26.75 and 19 MeV. The photon spectra from the two therapy units are different; however, depth dose data (10 × 10 cm, 100 cm TSD) are approximately the same. In addition, narrow‐beam attenuation coefficients in lead for the two machines were measured. The effective energy derived from the first HVL was 8.1 MeV for the linear accelerator and 7.8 MeV for the betatron.

ISSN:0269-3127    

DOI:10.1118/1.1637280

出版商:American Association of Physicists in Medicine    

年代:2003

数据来源: WILEY

摘要:

Trace element concentrations in human blood serum have been measured by x‐ray fluorescence and by x‐ray excitation with protons to test the current effectiveness of each technique for routine analysis of biological samples. Results are compared with those obtained from analysis by flame atomic absorption.

ISSN:0269-3127    

DOI:10.1118/1.1637281

出版商:American Association of Physicists in Medicine    

年代:2003

数据来源: WILEY

ISSN:0269-3127    

DOI:10.1118/1.1637282

出版商:American Association of Physicists in Medicine    

年代:2003

数据来源: WILEY

ISSN:0269-3127    

DOI:10.1118/1.1637283

出版商:American Association of Physicists in Medicine    

年代:2003

数据来源: WILEY

摘要:

The downtime for four linear accelerators in clinical radiation therapy has been studied for about four years. The time lost during patient treatment hours is on the average 3% with an in‐house technical service group, which invests approximately 1000 man‐hours per machine and year in preventive maintenance and repair. The time lost decreases significantly with time after installation.

ISSN:0269-3127    

DOI:10.1118/1.1637284

出版商:American Association of Physicists in Medicine    

年代:2003

数据来源: WILEY

ISSN:0269-3127    

DOI:10.1118/1.1637285

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.tb36048.x

出版商:Wiley    

年代:2003

数据来源: WILEY