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1

Assessment of the staff absorbed dose related to cyclotron operation and service in the production of 18F radiopharmaceuticals

Sadat-Eshkevar S. M., Karimian A., Mirzaii M.

Nukleonika

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2012

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Vol. 57, No. 3

407-410

EN

Cyclotron accelerators are used to produce medical radioisotopes. One of the most important problems which may be encountered is malfunction of a part of the target or beam line which requires stopping of the bombardment and making a repair. The decision about doing the repair depends on the whole body dose rate in a target room. In this work, dosimetric conditions related to the production of 18FDG radiopharmaceutical were simulated by the Monte Carlo (MC) method. Independently, the dose rates were measured by 7 ICRU spherical body phantoms placed inside the liquid target room and the maze of the cyclotron. The radiation dose rate inside the target room depends on the duration of the bombardment and the time passed after stopping the bombardment. The correlation between duration of the bombardment and required time after stopping the bombardment to reach the absorbed dose rate less than 25 mi Sv/h, was calculated for the presence and absence of the irradiated target. The results showed that the repair can be started immediately after stopping of the proton bombardment only if the target has been ejected from the target room and the duration of bombardment has not taken more than 10 min.

2

Computer simulation of temperature distribution on a solid target for 201Tl production

Aboudzadeh Rovais M. R., Yousefi K., Ardaneh K., Mirzaii M.

Nukleonika

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2011

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Vol. 56, No. 4

283-289

EN

Thallium-201 is of great interest in nuclear medicine for diagnostic purposes. It is produced by the 203Tl(p,3n)201Pb nuclear reaction. Since the target for 201Tl production is a solid target and the maximum beam current for the irradiation has a direct relation with its temperature surface, therefore, the control of temperature during the irradiation is essential. Designing a proper cooling system is one of the important and determining parameters in radionuclide production efficiency. Non-controlled temperature would cause melting and consequently loss of target materials that could be very costly especially when an isotopically enriched material is used. In this study, the heat transfer and temperature distribution on the target has been simulated based on a computational fluid dynamics (CDF) code for the thermal behavior of the target during the irradiation and under the different beam currents, cooling flow rates and target designing. The results on the routinely used target for the production of 201Tl in AMIRS, showed that there was a good linearity between proton beam currents (in the range of 100–350 mi A) and maximum temperature on the thallium target (345–458 K). The results also showed that the flow rate of the cooling water can be brought down (from routinely used 45 L/min) to 15 L/min without any risk of melting of target material.

3

Design and manufacture of krypton gas target for 81Rb production at a 30 MeV cyclotron

Rovais M.R.A., Mirzaii M., Kiyomarsi M., Yousefi K., Shadanpour N., Ensaf M. R.

Nukleonika

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2010

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Vol. 55, No. 2

225-231

EN

The cyclotron of nuclear medicine research group at the Agricultural, Medical and Industrial Research School (AMIRS) has been producing several radionuclides such as 201Tl, 67Ga, 18F and 81Rb for nuclear medicine centers. Gas targets are utilized in a variety of cyclotron producing radionuclides which are used in nuclear medicine centers. We report a method for the design and manufacture of a cyclotron gas target which facilitates both the collection and processing of the krypton gas target as well as the desired 81Rb. In this study a gas target was designed for routine production of 81Rb (for a 81Rb/81mKr generator) through the nuclear reaction natKr(p,2n)81Rb → 81mKr. The incident energy of protons on the target was 26.5 MeV. The gas target was made of stainless steel. The length of the target was 251 mm with double titanium windows, 20 μm in thickness. A production yield of 3.18±0.27 mCi/μA·h was obtained which was more than 80% of the calculated yield (4.1 mCi/μA·h).

4

Biological evaluation of [18F]-nifedipine as a novel PET tracer for L-type calcium channel imaging

Sadeghpour H., Jalilian A. R., Akhlaghi M., Shafiee A., Mirzaii M., Miri R., Saddadi F.

Nukleonika

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2008

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Vol. 53, No. 4

151-154

EN

Due to interesting role of dihydropyridines in cardiovascular diseases and drug resistance studies and lack of a fluorine-18 labeled imaging agent for L-type calcium channel studies, this study was designed. [18F]Dimethyl 2-(fluoromethyl)-6-methyl-4-(2-nitrophenyl)-1,4-dihydropyridine-3,5-dicarboxylate 2 was prepared in no-carrier-added (n.c.a.) form from a starting brominated compound in one step at 80°C in Kryptofix2.2.2/[18F]. Compound 2 was administered to normal rats via their tail veins for preliminary biodistribution studies and the ID/g% of the labeled compound was determined up to 3 h post injections. Coincidence images were obtained in rats 5 to 120 min. Radiofluorination on bromo precursor gave a fluorinated compound in 95% radiochemical purity and a 8% yield shown by RTLC and HPLC. Biodistribution studies showed that the tracer is accumulated in the heart in the first few minutes, followed by metabolism resulting in very soluble 18F-containing metabolites eliminated through the urinary tract. In coincidence images, the target organ was shown to be the heart. Lung had high accumulation possibly due to the presence of Ca2+ channels and/or hydrolyzing enzymes showing a significant myocardial uptake at 120 min. The data demonstrates a significant agreement with the reported L-type calcium channels throughout the animal body. To our knowledge, this is the first example of 18F-DHPs in the literature.

5

Production, quality control and initial imaging studies of [82mRb]RbCl for PET studies

Rowshanfarzad P., Jalilian A., Kiyomarsi M., Sabet M., Karimian A., Moradkhani S., Mirzaii M.

Nukleonika

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2006

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Vol. 51, nr 4

209-215

EN

Rubidium-82m was prepared via 15.4 MeV proton irradiation of a krypton-82 gaseous target (30% enrichment). Washing the target chamber with hot water yielded a Rb-82m containing solution, which was further purified using short column chromatography in order to remove organic/inorganic impurities. The flowthrough was formulated in normal saline for injection. Radionuclide, radiochemical and chemical purity tests were performed prior to administration to rats for imaging (radiochemical yield: 95-97%, radiochemical purity > 97%). Preliminary dual-head coincidence studies were performed to determine the distribution of [82mRb]Rb in normal rats. For biodistribution studies, Rb-81 was injected to rats and tracer accumulation in heart, GI and bladder was determined after sacrification in time intervals. A yield of 1.3 GBq at EOB, 235.7 MBq/mAh was obtained.

6

Development of 111In-DTPA-human polyclonal antibody complex for long-term inflammation/infection detection

Jalilian A., Rowshanfarzad P., Shafaii K., Kamali-Dehghan M., Moafian J., Akhlaghi M., Babaii M., Rajabifar S., Mirzaii M.

Nukleonika

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2005

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Vol. 50, nr 3

91-96

EN

Human polyclonal antibody (HIgG) was successively labeled with 111In-indium chloride after residulation with freshly prepared cyclic DTPA-dianhydride. The best results of the conjugation were obtained by the addition of solid DTPA-dianhydride (0.1 0.3 mg) to 100 mi l of the HIgG solution (0.2 0.4 mg/ml) at pH = 6 in phosphate buffer media at 25°C with continuous stirring for 30 min. Radio-thin-layer chromatography showed an overall radiochemical yield of 96 99% at optimized conditions (specific activity = 300 500 MBq/mg, radiochemical purity >98%). The final isotonic 111In-DTPA-HIgG complex was checked by radio-TLC to ensure the formation of only one species followed by filtration through a 0.22 mi filter. Preliminary long-term in vivo studies in turpentine-oil induced inflammation in rat model was performed to determine late complex distribution of the radioimmunoconjugate. The target/skin and target/ blood ratios were 27 and 51 after 24 h, and 23 and 51 after 110 h, showing a high selectivity of the radiopharmaceutical for inflammatory lesions.

7

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

Mirzaii M., Afarideh H., Hadji-Saeid S., Aslani G., Ensaf M.

Nukleonika

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2004

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Vol. 49, nr 1

23--27

EN

A new automated target for high yield production of aqueous [18F] fluoride at high beam currents has been constructed for a cyclotron at NRCAM in Karaj (Cyclone 30). It consists of one small golden sphere inside another target chamber, mounted into a special holder, which provides rapid cooling by water flow around and inside the sphere. The target is irradiated with 28 MeV protons. The incident energy on the target chamber is 18 MeV. This target is operated without external overpressure and has been tested for beam currents up to 60 ěA. The measured target yield is 80% of the theoretically calculated yield of 18F, which is used for the synthesis of [18F] 2-fluoro-2-deoxy-D-glucose.