Improving production of [sup 11]C to achieve high specific labelled radiopharmaceuticals

Abstract

Abstract. Molecular imaging is usually based on the recognition by the radiopharmaceuticals of specific sites which are present in limited number or density in the cells or biological tissues. Thus is of high importance to label the radiopharmaceuticals with high specific activity to be able to achieve a high target to non target ratio. The presence of carbon dioxide (CO 2 ) from the air containing 98,88% of 12 C and 1,12% 13 C compete with 11 CO 2 produced at the cyclotron. In order to minimize the presence of these isotopes along the process of irradiation, transferring and synthesis of radiopharmaceuticals labelled with 11 C, we applied this method: previous to the irradiation the target was 3-4 times flushed with He (5.7) as a cold cleaning, followed by a similar conditioning of the line, from the target up to the module, and finally a hot cleaning in order to desorb 12 CO 2 and 13 CO 2 , this was performed by irradiation during 1 min at 5 uA (3 times). In addition, with the aim of improving quality of gases in the target and in the modules, water traps (Agilent) were incorporated in the inlet lines of the target and modules. Target conditioning process (cold and hot flushings) as well as line cleaning, allowing the desorption of unlabelled CO 2 , together with the increasing of gas purity in the irradiation and in the synthesis, were critical parameters that enable to achieve 11 C-radiopharamaceuticals with high specific activity, mainly in the case of 11 C-PIB.

Boron Nitride Nanotube Cyclotron Targets for Recoil Escape Production of Carbon-11

“…Boron nitride nanotube (BNNT) nanomaterials [1][2][3][4][5] can be used in a recoil escape target to produce 11 C for incident proton energy at or below 11 MeV. This would enable 11 C production for economical low-energy cyclotrons [6][7][8][9], and it could be used to increase production from conventional 11 C gas targets on MiniTrace and RDS-111 cyclotrons. Preliminary experiments have demonstrated recoil escape production and recovery of small quantities of 11 CO 2 , and there has been a continued effort to develop a target design and platform that can be used to produce viable yields for a commercial system.…”

“…This would enable 11 C production for economical low-energy cyclotrons [6][7][8][9], and it could be used to increase production from conventional 11 C gas targets on MiniTrace and RDS-111 cyclotrons. Preliminary experiments have demonstrated recoil escape production and recovery of small quantities of 11 CO 2 , and there has been a continued effort to develop a target design and platform that can be used to produce viable yields for a commercial system. Conventional gas targets for 11 C production operate by proton bombardment of nitrogen gas [10][11][12][13].…”

“…Preliminary experiments have demonstrated recoil escape production and recovery of small quantities of 11 CO 2 , and there has been a continued effort to develop a target design and platform that can be used to produce viable yields for a commercial system. Conventional gas targets for 11 C production operate by proton bombardment of nitrogen gas [10][11][12][13]. However, due to the low nuclear cross-section of the 14 N(p,α) 11 C nuclear reaction below 11 MeV, this production method is not commercially viable for accelerators with proton energy in the range of 7-10 MeV.…”

“…Conventional gas targets for 11 C production operate by proton bombardment of nitrogen gas [10][11][12][13]. However, due to the low nuclear cross-section of the 14 N(p,α) 11 C nuclear reaction below 11 MeV, this production method is not commercially viable for accelerators with proton energy in the range of 7-10 MeV. Adding BNNT nanomaterials to the target allows for an additional production route via the 11 B(p,n) 11 C nuclear reaction, which has a higher cross-section at all proton energies, as shown in Figure 1 [14,15].…”

“…However, due to the low nuclear cross-section of the 14 N(p,α) 11 C nuclear reaction below 11 MeV, this production method is not commercially viable for accelerators with proton energy in the range of 7-10 MeV. Adding BNNT nanomaterials to the target allows for an additional production route via the 11 B(p,n) 11 C nuclear reaction, which has a higher cross-section at all proton energies, as shown in Figure 1 [14,15]. If the produced 11 C can be effectively recovered from the target, the total yield of 11 C will be greater than currently achievable using a conventional gas target.…”