Journal of Medical Physics
ORIGINAL ARTICLE
Year
: 2006  |  Volume : 31  |  Issue : 4  |  Page : 262--268

Empirical formula for the prediction of off axis ratios and isodose curves for a treatment planning system


Surajit Pal1, R Ravishankar2, RP Sharma3, G Muthukrishnan4, Dilip Kr Ray5, SN Roy6, DK Srivastava1 
1 Variable Energy Cyclotron Centre, 1/AF Bidhan Nagar, Kolkata, India
2 Health Physics Unit, VIP Road, Kolkata, India
3 L - 404 VIP Enclave, VIP Road, Kolkata, India
4 B-12, Adhunika Co-operative, 164/3A Lake Gardens, Kolkata, India
5 Chittaranjan National Cancer Institute, Kolkata, India
6 Department of Physics, Visva-Bharati, Santiniketan, India

Correspondence Address:
Surajit Pal
Variable Energy Cyclotron Centre, 1/AF Bidhan Nagar, Kolkata - 700 064
India

A mathematical model has been developed for prediction of off axis ratio (OAR), using Wood - Saxon term used to represent nuclear potential. This method has been satisfactorily applied for predicting OAR in case of 60Co γ -rays and high energy X-rays. Investigations are considered upto a depth of 25 cm in the case of 4MV LINAC for which measurements were carried out in our laboratory using indigenously developed Radiation Field Analyzer. For 60Co γ-rays as well as 6 and 18MV LINAC beams we could get off-axis profiles only upto 20 cm. The shift δ between measured and predicted OAR is within 2 mm except for 20 cm depth near the falling edge of the penumbra, where it is 2.80 mm. Software has been developed in Visual Basic 6 on Windows platform to plot Isodose curves, which is based on the mathematical modeling of OAR and central axis percentage depth dose.


How to cite this article:
Pal S, Ravishankar R, Sharma R P, Muthukrishnan G, Ray DK, Roy S N, Srivastava D K. Empirical formula for the prediction of off axis ratios and isodose curves for a treatment planning system.J Med Phys 2006;31:262-268


How to cite this URL:
Pal S, Ravishankar R, Sharma R P, Muthukrishnan G, Ray DK, Roy S N, Srivastava D K. Empirical formula for the prediction of off axis ratios and isodose curves for a treatment planning system. J Med Phys [serial online] 2006 [cited 2021 Oct 18 ];31:262-268
Available from: https://www.jmp.org.in/article.asp?issn=0971-6203;year=2006;volume=31;issue=4;spage=262;epage=268;aulast=Pal;type=0