Zinc-68 Isotope: The High-Abundance Stable Target Material Leading the Revolution in Next-Generation Medical Radionuclide Production
BY Tao, Published Dec 14, 2025
With more enquiries on Zinc-68 Isotope from web, I would like to share my production experience and operation these year to more end users who are interested. As a nuclear staff with more than 5 years of hands-on experience in stable and radioactive isotope research and production, I have witnessed the entire evolution of medical radionuclide supply chains. Few developments have excited me as much as the rapid rise of enriched zinc-68 (⁶⁸Zn) as the cornerstone target material for gallium-68 (⁶⁸Ga) production. Today, ⁶⁸Zn is no longer just one option among many — it is the enabling technology that is finally breaking the bottleneck of ⁶⁸Ga supply and making truly decentralized, high-volume production of next-generation PET tracers a reality.
Zn 68
1. Basic Nuclear Properties of Zinc-68 — Why Nature Chose It
Zinc has five stable isotopes. ⁶⁸Zn has the second-highest natural abundance at 18.50–18.80 % (the highest is ⁶⁴Zn at ~49 %). This apparently modest number becomes a huge practical advantage when we need to produce ⁶⁸Ga via the ⁶⁸Zn(p,n)⁶⁸Ga reaction.
Key nuclear data that matter in daily production:
- Natural abundance: 18.50 % (IAEA 2022 update)
- Recommended enrichment level for modern solid targets: ≥99.0 %, typically 99.2–99.8 %
- Nuclear reaction: ⁶⁸Zn(p,n)⁶⁸Ga
- Optimum proton energy window: 13–14 MeV incident → 8–10 MeV on target (after degraders)
- Theoretical thick-target yield (13.5 MeV): ~280 MBq/µAh with natural Zn, >1,500 MBq/µAh with >99 % ⁶⁸Zn
- Half-life of daughter ⁶⁸Ga: 67.83 minutes
- Decay mode: 89 % positron emission (Eβ⁺max = 1.92 MeV), perfect for PET
These numbers explain why every major supplier — Eckert & Ziegler, ITG, IRE ELiT, and now Asian manufacturers — has moved to highly enriched ⁶⁸Zn solid targets in the past five years.
2. The Historical Bottleneck: Generator-Dependent ⁶⁸Ga Supply
Until ~2018, >95 % of the world’s clinical ⁶⁸Ga came from ⁶⁸Ge/⁶⁸Ga generators. These generators rely on ⁶⁸Ge (T½ = 270.95 d) produced by high-energy proton spallation of molybdenum or rubidium, followed by elaborate chemical separation. The process is expensive, centralized, and limited to a few facilities worldwide (Brookhaven, Los Alamos, iThemba, ARRONAX).
Consequences for clinics:
- Generator cost: 35,000–55,000 USD per unit
- Maximum elution activity: ~1.85 GBq at calibration
- Only 2–8 patients per day possible in most centers
- Cold-chain logistics and customs delays common outside Europe/North America
The breakthrough came when cyclotron groups demonstrated that low-energy medical cyclotrons (16–19 MeV) could produce clinically relevant amounts of ⁶⁸Ga directly using enriched ⁶⁸Zn pressed or electroplated solid targets. A single 60–90 minute irradiation at 30–50 µA now routinely yields 40–90 GBq of ⁶⁸Ga — enough for 50–100 patient doses.
Zn 68 Isotope applications
3. Modern Solid-Target Production Technology Using ⁶⁸Zn
The current gold-standard target is the “coin” or “plate” design:
- Target material: 99.8 % ⁶⁸Zn metal (typical mass 300–800 mg)
- Backing: niobium or molybdenum body with helium cooling
- Plating method: molten-salt electrodeposition (Asia Isotope patented process) or cold pressing + vacuum sintering
- Beam parameters: 14.5 MeV incident, 40–60 µA, 90–120 min irradiation
- Typical end-of-bombardment activity: 70–110 GBq
- Dissolution: 7–10 M HCl at 90–110 °C, 15–20 min
- Purification: single-column hydroxamate or ZR resin process (recovery >95 %, processing time <25 min)
Result: GMP-grade [⁶⁸Ga]GaCl₃ ready for labeling in <45 minutes after EOB, with molar activity routinely exceeding 500 GBq/µmol.
4. Quantitative Comparison: Generator vs. Enriched ⁶⁸Zn Cyclotron Route
| Parameter | ⁶⁸Ge/⁶⁸Ga Generator (50 mCi) | Enriched ⁶⁸Zn Solid Target (90 min, 50 µA) |
|---|---|---|
| Initial activity available | 1.85 GBq | 80–110 GBq |
| Patients per day (3 GBq/dose) | 2–8 | 25–35 |
| Cost per GBq (approx.) | 8,000–12,000 USD | 300–600 USD |
| Geographic availability | Limited | Any hospital with 16–19 MeV cyclotron |
| Radionuclidic purity at EOS | >99.9 % | >99.9 % |
| Long-lived waste (⁶⁸Ge) | Yes | Negligible |
The economic and logistical superiority is overwhelming.
5. Global Supply Chain of Enriched Zinc-68 (Current Situation 2025)
Major certified suppliers of ≥99.0 % ⁶⁸Zn:
- Asia Isotope Development (China) – currently the largest volume supplier globally
- Eckert & Ziegler Eurotope (Germany)
- Isoflex (Russia/USA)
- Trace Sciences International (Canada)
Asia Isotope Development achieved >98 % enrichment routinely at multi-hundred-gram scale , driving the price from ~2,500 USD/g (2019) down to ~700–780 USD/g (2025 contract price for >100 g orders). This price collapse is the single most important enabler of widespread adoption.
6. Emerging Trends: Liquid Targets and Automated Solid Target Systems
Although pressed solid targets dominate today, two innovations are gaining traction:
- Liquid zinc nitrate targets (70Zn/68Zn blend in nitric acid)
Advantages: no target recovery, very high current (>100 µA) possible
Status: clinical batches already performed at University of Alabama and Rigshospitalet Copenhagen. - Fully automated solid-target transfer and dissolution systems
IBA Synthera, Trasis AllinOne, and Asia Isotope’s own Generation-III module now allow push-button production with <15 mSv exposure to staff.
7. Future Outlook: From ⁶⁸Ga to Theranostic Pairs Using Zinc Isotopes
The same enriched ⁶⁸Zn targets can produce copper-64 via ⁶⁸Zn(p,αn)⁶⁴Cu at slightly higher energy (30–40 MeV), though dedicated ⁶⁴Ni targets remain preferred. More interestingly, enriched ⁷⁰Zn is emerging as the optimal target for no-carrier-added ⁶⁷Ga production for SPECT — completing the zinc isotope family contribution to nuclear medicine.
8. Conclusion
Enriched zinc-68 has single-handedly transformed gallium-68 from a niche, generator-constrained radionuclide into the most widely used positron emitter after fluorine-18. The combination of high natural abundance, straightforward enrichment, excellent nuclear reaction cross-section, and mature solid-target technology has created what I confidently call the “third pillar” of modern PET — alongside ¹⁸F-FDG and ¹¹C tracers.
Any nuclear medicine department with a modern low-energy cyclotron can now produce its own ⁶⁸Ga in quantities that were unimaginable five years ago. This is not evolution; this is revolution — and zinc-68 is the material that made it possible.
Would you like a deeper dive into any specific technical parameters or applications?
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