## 2 Cyclotron-Produced \({}^{68}\)Ga Using a Solid Target
### \({}^{68}\)Ga Production Using a Solid Target with ACSI Cyclotron  
The ACSI cyclotron, namely TR-19 and TR-24, has the ability to provide a variable energy spectrum without entirely relying on an energy degrader. [PERSON] and group [33] and [PERSON] and group [27] studied the production of \({}^{68}\)Ga using a solid target and the TR-19/TR-24 cyclotrons ACSI utilizing a pressed target, as presented in Table 2. To prepare the target, [PERSON] and co-workers used a few steps in which the target was pressed with 250 mg of enriched \({}^{68}\)Zn at 17,600 psi for 5 min before being inserted into a magnetic target carrier [33]. On the other hand, [PERSON] and group [27] used 100 mg of hydraulically pressed, enriched \({}^{68}\)Zn at 35 kN to produce a 400 \(\upmu\)m thick pellet, which was then sintered at 350 \({}^{\circ}\)C for 5 h before being placed on a silver support. The target was then pressed with 20 kN at 120 \({}^{\circ}\)C for 30 s to achieve a target density of 3.18 g/cm\({}^{3}\)[27]. [PERSON] and co-workers [33] used a 400 \(\upmu\)m aluminum integrated degrader to decrease the proton beam from 17.2 MeV to 13-14 MeV on the target material, while [PERSON] and group [27] used a 250 \(\upmu\)m silver degrader to decrease the proton beam from 17 to 12.5 MeV. The saturation yield (8.7 GBq/\(\upmu\)A) produced by [PERSON] and co-workers was higher than that of other studies presented in this review. Remarkably, the mass of the enriched \({}^{68}\)Zn in their experiment was only 3.39 mg to produce 1 GBq of \({}^{68}\)Ga. Thus, this method may be the most cost-effective, as it uses only pressed targets, and an irradiation time of 30 min is required to produce 68.8 GBq. Pressed targets are usually less time-consuming to produce. However, [PERSON] and their group found traces of \({}^{107}\)Cd and long-lived \({}^{109}\)Cd related to the activation of silver backing. Metallic impurities other than Gallium isotopes can be removed during the separation of target material and purification. Nevertheless, the co-production of \({}^{66}\)Ga and \({}^{67}\)Ga was less than 0.1% of total radioactivity 4 h post-irradiation. Furthermore, they validated the silver disc pellet for 10 irradiations without significant degradation, limiting the time required to prepare the silver disc [27]. Solid Target Dissolution, Target Material (\({}^{68}\)Zn) Separation and Purification, and \({}^{68}\)GaCl\({}_{3}\) Formulation  
Following irradiation, the solid target is transferred using a pneumatic transfer system for dissolution. The dissolution of the target is another important aspect related to the final activity obtained, and in the case of the short half-life of \({}^{68}\)Ga, the time required for purification and its AMA are crucial. Thus, an automated procedure for target material (\({}^{68}\)Zn) separation and purification, and [\({}^{68}\)Ga]GaCl\({}_{3}\) formulation using one-, two-, and three-column strategies has been reported. The typical steps of preconditioning and loading, washing, and eluting with an appropriate solution are performed on each column. This is to achieve low-volume and low-molarity of [\({}^{68}\)Ga]GaCl\({}_{3}\), which in turn results in either high AMA, similar or improved from post-processing of the \({}^{68}\)Ge/\({}^{68}\)Ga generator eluate [40; 41; 42; 43; 44; 45]. The dissolution of the solid target and purification of [\({}^{68}\)Ga]GaCl\({}_{3}\) using TR-19 and TR-24 cyclotrons is presented in Table 3. The typical dissolution solution would be using a concentrated HCl of 7 M or more to form [\({}^{68}\)Ga]GaCl\({}_{3}\). This is imperative to ensure maximum dissolution and the right molarity for optimized retention. In contrast, [PERSON] and co-workers used a different approach using 7 M HNO\({}_{3}\)[33]. This proceeds by adjusting the pH using ammonium formate (NH\({}_{4}\)HCO\({}_{2}\)) to retain up to 97% of the EOB activity in the hydroxamate resin. The group also noted a dark red (ferric hydroxamate) on the top of the hydroxamate resin.