Introduction Krypton-81m is a radioactive gas with a half-life of 13 s, and found to be useful in many applications in nuclear medicine, particularly for lung perfusion studies and ventilations. Due to high demands for 81mKr, we have developed an automated Krypton system to be installed in one of the Cyclotron’s beamlines at King Faisal Specialist Hospital and Research Centre (KFSH&RC) and to deliver large activity of the radioactive gas. Material and Methods The effective cross section of producing 81Rb is between 15 and 30 MeV [1]. Therefore, range and stopping power of the effective cross section were calculated with respect to gas density of 0.0185 g/cm3. This value is equivalent to gas density at 5.0 bars at room temperature. SRIM calculations resulted in a range of 589 mm. However, due to limitation in fabricating such long target chamber, the target length is chosen to be 250 mm. Attached to the end of target body is a special water circulating flange ‘back-pool’, its purpose is to absorb the rest of the energy and protons Bragg peak. The target body is made of Aluminum with the inner part being electroplated with nickel. The target body is of conical shape. The target body is electrically isolated from other parts to allow accurate beam current reading. Full access to the target loading/unloading steps is made through touch screen technology (FIG. 2) for user access. Additionally, the target control system is designed to be protected through chain of interlock steps. The production cycle of 81Rb is explained as follow. Target is evacuated to approximately 10−3 mbar before being filled with natKr at pressure of 5 bars. At the end of bombardment, recovery of natKr is done via cryogenic vessel. Finally, the radioactivity is washed with KCl and pushed to Hotcells through the nitrogen gas for chemistry processing. Irradiation time was approximately 30 min. Results and Conclusion Experimental results clearly showed a fairly good activity of 81mKr as shown in TABLE 1. In all experiments, the radionuclidic purity of 81mKr was above 99.59%. 79mKr and 79Kr were also measured with a percentage of, respectively, 0.34 and 0.07 %. Special attention has to be drawn to last experiment where the yield significantly in-creased, due to the period where the KCl left inside the target (10 min) before pushing the solution to the Hotcells

Introduction Nitrogen [13N] NH3 is a liquid radioisotope, produced by medical cyclotrons for nuclear medicine application and widely applied for evaluation of myocardial perfusion in clinical assessments [1,2]. Owing to its short half-life (10 minutes), the unloading procedure of the radio-active solution of [13N]NH3 from the target is crucial in saving the activity produced for patient. Therefore, an efficient technique in un-loading the radioactive solution from the target body was developed using COMSOL Multiphysics. The new design of the target with improved unloading technique resulted in 30% increase of the available 13N activity. In our experiments, 13N was produced by the 16O(p,α)13N reaction. The energy of proton beam was 16.5 MeV. Material and Methods A 2D model was developed using COMSOL Multiphysics to simulate the inner geometry of [13N] Ammonia target. In the 2D model, water and aluminum were used as materials for the inner body and outer boundary (walls), respectively. The physical equations used to solve the problem of allocating proper place for the loading/unloading opening is turbulent, k-ε Module being extracted from fluid flow module. FIGURE 1 shows the result of simulating water flow on the target water channels. The entrance of the pushing solution (for unloading) was designed to create a turbulent flow inside the target body and, hence, to collect most of the activity inside the target. FIGURE 2 shows the setup for 13N production. A peristaltic pump is used to push the solution after irradiation to the hotcell at 6 ml/min flowrate. The distance from the target to the hotcell is approximately 30 meters. Results and Conclusion FIGURE 3 presents activity produced in milicurie (mCi) for several patient runs. The activity obtained in some experiments reached up to 330 mCi when we irradiated the target with 25 μA for 15 min. This was satisfactory for delivery to the patient at the nuclear medicine department. Moreover, purity of [13N] purity was above 95 % what meets the standard regulation for administration to a patient.

Introduction Krypton-81m is a radioactive gas with a half-life of 13 s, and found to be useful in many applications in nuclear medicine, particularly for lung perfusion studies and ventilations. Due to high demands for 81mKr, we have developed an automated Krypton system to be installed in one of the Cyclotron’s beamlines at King Faisal Specialist Hospital and Research Centre (KFSH&RC) and to deliver large activity of the radioactive gas. Material and Methods The effective cross section of producing 81Rb is between 15 and 30 MeV [1]. Therefore, range and stopping power of the effective cross section were calculated with respect to gas density of 0.0185 g/cm3. This value is equivalent to gas density at 5.0 bars at room temperature. SRIM calculations resulted in a range of 589 mm. However, due to limitation in fabricating such long target chamber, the target length is chosen to be 250 mm. Attached to the end of target body is a special water circulating flange ‘back-pool’, its purpose is to absorb the rest of the energy and protons Bragg peak. The target body is made of Aluminum with the inner part being electroplated with nickel. The target body is of conical shape. The target body is electrically isolated from other parts to allow accurate beam current reading. Full access to the target loading/unloading steps is made through touch screen technology (FIG. 2) for user access. Additionally, the target control system is designed to be protected through chain of interlock steps. The production cycle of 81Rb is explained as follow. Target is evacuated to approximately 10−3 mbar before being filled with natKr at pressure of 5 bars. At the end of bombardment, recovery of natKr is done via cryogenic vessel. Finally, the radioactivity is washed with KCl and pushed to Hotcells through the nitrogen gas for chemistry processing. Irradiation time was approximately 30 min. Results and Conclusion Experimental results clearly showed a fairly good activity of 81mKr as shown in TABLE 1. In all experiments, the radionuclidic purity of 81mKr was above 99.59%. 79mKr and 79Kr were also measured with a percentage of, respectively, 0.34 and 0.07 %. Special attention has to be drawn to last experiment where the yield significantly in-creased, due to the period where the KCl left inside the target (10 min) before pushing the solution to the Hotcells

Introduction Nitrogen [13N] NH3 is a liquid radioisotope, produced by medical cyclotrons for nuclear medicine application and widely applied for evaluation of myocardial perfusion in clinical assessments [1,2]. Owing to its short half-life (10 minutes), the unloading procedure of the radio-active solution of [13N]NH3 from the target is crucial in saving the activity produced for patient. Therefore, an efficient technique in un-loading the radioactive solution from the target body was developed using COMSOL Multiphysics. The new design of the target with improved unloading technique resulted in 30% increase of the available 13N activity. In our experiments, 13N was produced by the 16O(p,α)13N reaction. The energy of proton beam was 16.5 MeV. Material and Methods A 2D model was developed using COMSOL Multiphysics to simulate the inner geometry of [13N] Ammonia target. In the 2D model, water and aluminum were used as materials for the inner body and outer boundary (walls), respectively. The physical equations used to solve the problem of allocating proper place for the loading/unloading opening is turbulent, k-ε Module being extracted from fluid flow module. FIGURE 1 shows the result of simulating water flow on the target water channels. The entrance of the pushing solution (for unloading) was designed to create a turbulent flow inside the target body and, hence, to collect most of the activity inside the target. FIGURE 2 shows the setup for 13N production. A peristaltic pump is used to push the solution after irradiation to the hotcell at 6 ml/min flowrate. The distance from the target to the hotcell is approximately 30 meters. Results and Conclusion FIGURE 3 presents activity produced in milicurie (mCi) for several patient runs. The activity obtained in some experiments reached up to 330 mCi when we irradiated the target with 25 μA for 15 min. This was satisfactory for delivery to the patient at the nuclear medicine department. Moreover, purity of [13N] purity was above 95 % what meets the standard regulation for administration to a patient.