Response of TLD and RPL personal dosimeters in a national inter-comparison test program

Background: Different kinds and models of personal dosimeters are used in individual monitoring by workers. Performance testing as part of approval procedures is carried out to demonstrate that the essential performance specifications are routinely maintained. There are four service providers in Iran which use different luminescence techniques [i. e. TLD and RPL] with various kinds of dosimeter materials/reader instruments in personal dosimetry services. Materials and Methods: A national performance approval tests program was performed for the dosimeters of the service providers in energy range of soft, 660 keV and 1.25 MeV, at the doses values around the recoding, investigation and annual dose limits, and different angle of incidents [e. g. 0, 20, 40 and 60 degree]. Results: The results of this testing satisfies the overall accuracy criteria with 95% confidence levels specified by the ICRP, except that of RPL technique in low energy which overestimates the dose out of the acceptable accuracy band defined as the ICRP trumpet curves. Conclusion: The inter-comparison has proved that the personal dose equivalent quantity, H[p][10], defined by the ICRU and recommended by the IAEA are becoming widely accepted and implemented in most participated laboratories

Proton beam dosimetry by CR-39 track-etched detector

High and intermediate energy protons are not able to form a track in a solid state nuclear track detector [SSNTD] directly. However, such tracks can be formed through secondary particles created during primary radiation nuclear reactions in a SSNTD. The protons with primary energies of 9.6 and 30 MeV available at the cyclotron accelerator with corresponding low LETs of 5.87 and 2.40 keV/ micro m were taken into consideration. The nuclear tracks etch rate ratio V in CR-39 were measured and transformed into LET spectra for the absorbed and equivalent dose measurements. The optimum etching condition of 6 N NaOH solutions at 65 to 70 ?C over a 6-hour period for the CR-39 were found initially. The corresponding bulk etching rate reached a steady rate of about 0.62 to 1.3 um/h after nine hours for an optimum etching condition. Although the LET was low, but the energy range seemed sufficient enough to create secondary particles with much higher LET through the nuclear reactions in CR-39. The relative absorbed dose contribution of the created secondary particles to the primary particles for the 9.6 and 30 MeV protons in CR-39 at 1 Gy entrance dose were 7.5 and 29.6%, respectively. The contribution of the secondary particle increased relatively with the proton energy decrease. This phenomenon could modify the characteristics of the energy transfer process due to secondary particles when such particles are used for radiobiological studies and/or for radiotherapy

Design of a PLC system for automatic I-123 production

Design of the production system for Iodine-123 has begun recently in nuclear research centre of agricultural and medicine [NRCAM]. The production system consists of pipes for xenon gas transfer, equipped with 10 valves, 3 heaters, fluid nitrogen and 2 vacuum pumps. In the first prototype the function of elements was being done manually by an operator. Because dispensing radiopharmaceuticals manually involves receiving radiation dose by operators, therefore, automation is very important step in radiopharmaceutical production. The automatic system for production of Iodine-123 is PLC /135u Siemens, which is designed and installed for the first time in Iran. The PLC was connected to the production system through relays. By programming the CPU of the PLC, start up and control of the production procedure was executed automatically. Automation leads to reduced presence of operator for Iodine-123 production. We were also able to record storage and transfer of materials and minimize risk of error. Automation in production of radiopharmaceutical may lead to reduced radiation dose to personnel and achieved better dispensing precision

[Production, formulation, quality control and primary biological studies of [18F]KF for skeletal PET scanning]

[[18]F]KF, considered as a reference standard for positron emission tomography of the skeletal system, was produced by the bombardment of enriched water [[18O]H2O>95%] with high energy protons in NRCAM cyclotron. After the extraction of fluoride from enriched water as KF, and passing it through microbial filter and fine adjustment of acidity and osmolality, it was converted into an injectable form. Pre-clinical investigations and biological controls were performed to determine radioisotope distribution in laboratory rats, thus suitable information was gathered for imaging in humans. This radiopharmaceutical was proved to be quite safe and of high quality as a result of testing in laboratory rats

Production of [18 F] fluoride with a high-current two layer spherical gold target

Fluoride-18 is the most widely used radioisotope for Positron Emission Tomography [PET]. [18F] 2-flouro- 2-deoxy D-glucose [FDG] has become a standard tool in the area of clinical research. The oxygen-18 enriched water is the most widely used target for the production of fluoride-18. The use of the nuclear reaction 18O [p,n]18F has been found as the most effective method for the production of [18F] fluoride. Materials and methods: Gold is a chemically resistant metal, which has been found wide application in the chemical industry where it is often used in corrosive environments at high temperature.It is also one of the highest thermal conductivity of metals. A two layer-spherical gold chamber design was chosen to obtain a maximum pressure stability under high beam currents. The target body is consisted of two chambers, internal chamber for internal cooling and external chamber for enriched water target. The target is irradiated with 28 MeV protons energy. The incident energy on the target chamber is 18 MeV. This target is operated without external over-pressure and has been tested for beam currents up to 60 micro A. The measured target yield is 2655 MBq/micro Ah. There is found that saturation yield is 8.3 GBq/micro A and shows 80% of theoretical yield. It was observed that gold is a good material for the construction of the target chamber, and also the spherical chambers are the best construction to bearing high pressure under high-current beam condition up to 60 micro A

Production of Ga-67 in Iran

The radioisotope 67Ga [T 1/2=78 h] in extensively used as single photon marker for detecting the presence of malignancy and the diagnosis of inflammatory diseases. The high tumor specificity of carrier-free 67Ga make it one of the most interesting radionuclides in nuclear medicine for in vivo scanning studies. 67Ga is a cyclotron produced radioisotopes and is one of the radiopharmaceuticals which is produced at our center. An enriched 68Zn cyclotron target design has been developed for the large-scale production of carrier-free 67Ga with -<5 percent 66Ga contamination as one of the impurities. The advantage of high 67Ga yield from proton beam bombardment of enriched Zinc is somewhat to our disadvantage due to the high price of enriched Zinc. Due to this problem another alternative method for Ga-67 production was sought. Our theoritical and experimental studies have been resulted to production of 67Ga by irradiating natural Zinc with deuteron beam. The production of the radiopharmaceutical is achieved by two steps. 1] Deuteron bombardment of natural Zinc target in the cyclotron and subsequent production of Ga-67. 2] Chemical processing which involves the separation of 67Ga from target material. After quality control testing, the produced 67GaCI3 is converted to citrate and as a sterile and pyrogen free product, it is ready for human use