Dosimetric and qualitative analysis of kinetic properties of millennium 80 multileaf collimator system for dynamic intensity modulated radiotherapy treatments.

The aim of this paper is to analyze the positional accuracy, kinetic properties of the dynamic multileaf collimator (MLC) and dosimetric evaluation of fractional dose delivery for the intensity modulated radiotherapy (IMRT) for step and shoot and sliding window (dynamic) techniques of Varian multileaf collimator millennium 80. Various quality assurance tests such as accuracy in leaf positioning and speed, stability of dynamic MLC output, inter and intra leaf transmission, dosimetric leaf separation and multiple carriage field verification were performed. Evaluation of standard field patterns as pyramid, peaks, wedge, chair, garden fence test, picket fence test and sweeping gap output was done. Patient dose quality assurance procedure consists of an absolute dose measurement for all fields at 5 cm depth on solid water phantom using 0.6 cc water proof ion chamber and relative dose verification using Kodak EDR-2 films for all treatment fields along transverse and coronal direction using IMRT phantom. The relative dose verification was performed using Omni Pro IMRT film verification software. The tests performed showed acceptable results for commissioning the millennium 80 MLC and Clinac DHX for dynamic and step and shoot IMRT treatments.

Environmental monitoring of radon, thoron and their progeny in some dwellings of northern Haryana (India).

The problem of randon is an important global problem of radiation hygiene concerning the world population. Radon and its progeny are the major contributors in the radiation dose received by general population of the world. Keeping this in mind, the environmental monitoring of radon, thoron and their progeny in some dwellings of northern part of Haryana state of India has been carried out. The radon thoron twin dosimeter cups were used for the study. Three pieces of LR-115 solid-state nuclear track detectors were fixed in the dosimeters and were suspended in the dwellings for three months during a season. The first detector indicated radon, thoron and progeny concentration, the second showed radon and thoron concentration, while the third detected only the radon concentration. The aim of study was to carry out possible health risk assessment in the dwellings under consideration. During summer season, the radon concentration in northern region of Haryana varied from 66-97 Bq m(-3), while the thoron concentration in the same dwellings varied from 27-65 Bq m(-3). During winter season, radon concentration in northern region of Haryana varied from 73-104 Bq m(-3) with an average of 88 + 7 Bq m(-3), while the thoron concentration in the same dwellings varied from 35-69 Bq m(-3) with an average of 55 +/- 8 Bq m(-3). The radon-thoron progeny levels and annual doses received by the inhabitants in the dwellings under study have also been calculated.