THE CALIBRATION PROCESS OF OSL DETECTORS USED FOR STAFF AND PATIENT DOSIMETRY IN HOSPITAL ENVIRONMENT

TUNÇEL N., KARAYALÇIN B., Koca G.

RPM 2014, Varna, Bulgaria, 30 May - 02 June 2014, vol.2, no.1, pp.388, (Full Text)

  • Publication Type: Conference Paper / Full Text
  • Volume: 2
  • City: Varna
  • Country: Bulgaria
  • Page Numbers: pp.388
  • Akdeniz University Affiliated: Yes

Abstract

The optically stimulated luminescence (OSL-BeO) dosimeter is increasingly being used as a dosimetric technique in various fields such as medical,environmental and spacedosimetry. The in hose calibration process for usage of OSL’s at hospital was arranged according to the encapsulated Iodine-131 radioactive source which is used in nuclear medicine department. This process is helpful for confidence of OSLs used for dosimetry of staff and patients treated with high activity I–131. I–131 is the most frequently used source for thyroid carcinoma therapy. In the fixed activity protocol, a high activity 3.7-7.4GBq(100-200 mCi) I–131 is administered. The beta is often dominant radiation for treatment, although the associated gamma emission gives rise to exposures to other tissues and even to other individuals. In this study high activity (100mCi) encapsulated I-131 was used as calibration source. This source was placed in Plexiglass tube. The measurement point was planned in different radial distances which are 30, 50 and 100cm from source free in air. These positions were used to measure dose rate by Geiger–Muller (GM) detector. On the other hand 3 pieces of OSL with cover carrier which are used in calibration process was placed in the same positions. The irradiation exposure time was one hour for all of OSLs. The OSLs were supplied by a private organization and the reading process performed by them. The standard calibration process was carried on with beta emitter sources like Sr–90.For two type detectors the background values were measured in the room which planned to perform calibration process. The background value was 0.11mR/h. The corrected readings at mentioned positions were 136.9, 54.9 and 15.5mR/h. Also the mean background value of OSLs was 0.12 and 0.11 mSv based on Hp10-Hp007. The corrected OSL Hp10-Hp007 read outs at same distances were 1.67, 0.59 and 0.14mSv and 1.90, 0.77 and 0.18mSv respectively. The measured values in mR/h by GM were converted to mSv. These were 1.19, 0.477 and 0.135mSv for the queue geometric positions. The inverse square law consistency in both measurements was found (R2=0.99). The reliable use of OSLs in dosimetry of staff and particularly patients was provided. In a typical yearly workload, the average annual dose to the whole body for all staff by OSL was 0.80mSv. After administration of 100mCi therapeutic dose to specific patient,this value was 97.5+32.6mSv.