Experimental and Monte Carlo study of the effect of the presence of dry air, cortical bone inhomogeneities and source position on dose distribution of the mHDR-v2 source.
BACKGROUND
Recently it was data wise established that there is a considerable dose difference due to source position from the surface of the patient, and due to the presence of inhomogeneities.


OBJECTIVE
It aims at to find out the dose difference due to source position, and inhomogenieties in water phantom of high dose rate (HDR)(192) Ir mHDR-v2 source by experiment and by Monte Carlo (MC) simulation GEANT4 code.


METHODS
The measured study of the source was done using an in-air ionization chamber, water phantom while the calculated study was done by modeling the water phantom and its water, inhomogeneities, position of source, and points of calculation.


RESULTS
The measured and calculated dose differences are 5.48 to 6.46% and 5.43 to 6.44% respectively higher in the presence of dry air and 4.40 to 4.90% and 4.38 to 4.88% respectively lower in the presence of cortical bone. However, for the study of the effect of source position on dose distribution, when the source was positioned at a 1 cm distance from the surface of water phantom, the near points between 1 cm and 2 cm are 2 to 3.5% and 2.1-3.7% underdose and for distant points from 3 cm to 8 cm from the source are 4 to 15% and 4.1 to 15.8% underdose for measured and calculated studies, respectively, to the dose when the source was positioned at midpoint of water phantom.


CONCLUSIONS
These results can be used in the treatment planning system.
Department of Radiotherapy, Pt JNM Medical College & Dr BRAM Hospital, Raipur, India. rakemohachan@rediffmail.com
Rakesh M
RM
Chandola
Samit
S
Tiwari
Manjula
M
Beck
Pradeep Kumar
PK
Chandrakar
Suresh Kumar
SK
Thakur
D000388:Air; D001842:Bone and Bones / Q000528:radiation effects*; D006801:Humans; D007496:Iridium Radioisotopes / Q000627:therapeutic use; D009010:Monte Carlo Method; D019047:Phantoms, Imaging; D011829:Radiation Dosage
D007496:Iridium Radioisotopes