Journal of Medical Physics
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   1996| April-June  | Volume 21 | Issue 2  
    Online since April 24, 2009

 
 
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Dosimetric Aspects Of Electron ARC Therapy
J.S Avadhani, D.D Deshpande, R.M Nehru, S Sakar, P.S Viswanathan
April-June 1996, 21(2):60-63
Electron arc is a special technique very useful in may clinical situations. Detailed measurements and planning were carried out for standardizing electron arc technique at our center. An electron arc cone of appropriate thickness is fabricated to give an area of 5 cm x 35 cm at isocenter. The central axis depth dose data were generated using parallel plate chamber and profiles were generated with cylindrical type chamber at multiple depths using computer controlled water phantom dosimetric system. This data was fed into treatment planning system through a digital interface which avoids manual feeding errors, if digitizer or key board is used. A cylindrical wax phantom was constructed with necessary holes for placement of 0.6 cm3 ion chamber at appropriate depths for energies between 6 MeV and 20 MeV electrons. The monitor units per cGy per degree were determined for various source-to-skin distances. The in vivo measurements were also carried out in phantom and patient and the results were found to match within + 5% of expected value.
[ABSTRACT]   Full text not available  [PDF]
  579 102 -
Two New Formulae For Estimating The Output Of X-Ray Units
Pratik Kumar, Rashmi Kaul, M.M Rehani, Bhawna Sethi, M Berry
April-June 1996, 21(2):64-70
The radiation output from different X-ray machines varies considerably. For a given kVp and mAs, this variation results from voltage waveform from the generator, tube-age and filtration. In routine practices, no exposure meter is fitted in the controls of X-ray machines. The most appropriate way to know entrance skin exposure (ESE) to the patient is by using the standard formulae. But, as yet, no one has evaluated the different formulae available in the literature, for their validity when applied to different machines. In the present study, we have first measured the ESE for seven X-ray machines and then estimated the % error between experimental and calculated values with five formulae and nomogram available in literature. Since all these formulae gave errors exceeding # 35% of the actual value, we have evolved two new formulae and developed appropriate computer programs. These two formulae are able to provide an estimate of ESE within a mean % error of -3.9 + 14.5 and 0.7 + 19.4 respectively, for seven X-ray machines included in the study
[ABSTRACT]   Full text not available  [PDF]
  483 146 -
Practice Of Diagnostic Radiology And Radiotherapy And Radiation Exposure Therefrom : A Synoptic View Of Worldwide Scenario (Summary Of Unscear 1993 Data)
A.R Reddy, A Nagaratnam, S.C Jain, M.M Gupta
April-June 1996, 21(2):45-52
The 1993 Report of the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) has provided extensive data on medical radiation exposures worldwide and exposures therefrom. The present paper summarises the data from UNSCEAR 1993 as relevant to diagnostic radiology and radiotherapy. Data for India are separately indicated. Countries have been categorised into four levels of health care, based on the population per physician, (India is in level 11). Data have been grouped into three time periods, 1975-79, 1980-84 and 1985-88. Data are provided for the frequencies of different types of diagnostic examinations, average patient doses therefrom, annual collective effective doses (in man-Sv), and per caput effective doses. Similar data are discussed for radiotherapy (both teletherapy and brachytherapy). Temporal and regional trends and variations in dose for given procedures for each level of health care, as well as for the world as a whole are discussed. Occupational exposures in diagnostic radiology and radiotherapy are finally discussed.
[ABSTRACT]   Full text not available  [PDF]
  536 89 -
Development Of A Teletherapy Treatment Planning Software
B Paul Ravindran, C.A Jayachandran
April-June 1996, 21(2):53-59
In spite of using a sophisticated computer, if the data and algorithms used were poor and inaccurate, then the result would be poor. This situation is referred to as the 'Ostrich syndrome'. The objective of the present work is to avoid the 'Ostrich syndrome'. A software has been developed for generating the total dose distribution using (i) experimental data based on Fan-line method, and (ii) analytical method based on Cunningham's equation. The Cunningham's equation for off-axis ratio was modifed to fit our experimental data for 60Co beams. For electron beams, only the Fan-line algorthm has been used. The dose distribution obtained with the software developed was compared with that obtained by manual planning.
[ABSTRACT]   Full text not available  [PDF]
  507 95 -
Analysis Of Overexposure Cases For Female Radiation Workers In Medical And Research Institutions In India
Jayashri M Mahajan, O.P Massand, G Venkataraman
April-June 1996, 21(2):71-73
Radiation Protection Services Division, BARC conducts countrywide personnel monitoring service for 40,000 radiation workers, of which about 22,000 radiation workers are from industrial, medical and research institutions. The number of female radiation workers constitute about 5% of the total radiation workers monitored. Basis for control of occupational exposures of women are same as that for men except for pregnant women (foetus). Equivalent dose above 10 mSv in a service period is investigated as to the causes of exposure-whether the exposure was really received by the worker (genuine) or only the monitoring badge received the exposure due to other reasons (non-genuine) and necessary remedial actions are taken. Analysis of overexposure cases in female radiation workers as a group has been done for the period of four years (1 930-1 993) and, the conclusions are presented.
[ABSTRACT]   Full text not available  [PDF]
  457 74 -
Diagnostic Imaging : Quality Assurance
M.M Rehani
April-June 1996, 21(2):74-75
Full text not available  [PDF]
  297 145 -
 
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