44Sc

Sc 44

4.0 h

β⁺ 1.5...

γ 1157...

Chemical properties

Sc-44 is a rare earth, usually in trivalent state. It can be radiolabelled with macrocyclic chelators, e.g. DOTA or other chelators such as NODAGA, AAZTA, pypa, mpatcn, etc. . The ionic radius is 74.5 pm.

Nuclear properties

Sc-44 decays by β⁺ decay (94.27(5)%) and electron capture (5.73%) with a half-life of 4.042(25) hours to stable Ca-44. It emits a medium energy positron spectrum with 632 keV average energy and 1474 keV maximum energy.

Moreover, Sc-44 emits a hard γ-ray at 1157.0 keV (99.9%) in prompt coincidence (T_1/2=2.7 ps) with every emitted positron.

The mean electron energy emitted per decay is 596 keV, the mean photon energy per decay is 2136 keV .

Production

Sc-44 is produced by proton irradiation of enriched Ca-44 oxide (or carbonate targets) at: Injector 2 at PSI or C30 cyclotron at NCBJ. ARRONAX uses instead deuteron irradiation .

Distribution

The radiochemical separations are performed at ARRONAX (ARRONAX, Nantes, France), PSI Radiochemistry Laboratory (PSI, Villigen, Switzerland) or POLATOM (NCBJ, Otwock-Swierk, Poland). Activity will be shipped from there to the users in form of ScCl₃ (or acetate) solution, ready for labelling of e.g. DOTA-compounds.

Examples of use

Sc-44 has been evaluated preclinically with peptides, PSMA ligands, affibodies and monoclonal antibodies .
Settings of commercial activity meters have been evaluated with Sc-44 .
The preclinical PET imaging performance of Sc-44 has been compared to other positron emitters .
The impact of the prompt γ-ray emission on quantification with preclinical and clinical scanners has been evaluated .
First-in-human applications of Sc-44-DOTATOC and Sc-44-PSMA respectively have been reported with clinical PET/CT imaging up to 23.5 h post injection .
Sc-44-PSMA PET/CT imaging is considered useful to evaluate maximum permissible activity in Lu-177-PSMA therapy .
Sc-44 is considered the prime candidate for 3γ-imaging, also called γ-PET .
Sc-44 is also considered the prime candidate for ortho-positronium mean lifetime imaging .

Purity grades available

research

preclinical

No carrier added (n.c.a.)

Yes

Parameter	Requirements
Production route	Ca-44(p,n)Sc-44 [or Ca-44(d,2n)Sc-44 at ARRONAX]
Decay	Decays to stable Ca-44: 94.3% β⁺, 5.7% EC
Half-life	4.04 h
Processing	1 or 2-step column separation
Primary Container	2.5 mL borosilicate glass V-vial with silicon rubber screw cap
Product Grade	n.c.a.
Physical Form	Liquid
Chemical form	In 0.05 M HCl, 0.1 M HCl, 4.85 M NaCl/0.13 M HCl or 1 M NaOAc
Radioactive Concentration (gamma spectrometry)	n.a.
Appearance	Clear colourless solution
Radionuclide Identification (gamma spectrometry)	1157 keV gamma line and 511 keV annihilation gamma line present
Radionuclidic purity (gamma spectrometry)	99.8% at calibration time (0.2% Sc-44m)
Chemical purity (ICP-OES)
Molar activity (ICP-OES)	>100 GBq/µmol at calibration time (>0.3% of theoretical maximum)
Apparent Molar Activity	Labelling up to 25 MBq/nmol DOTANOC or DOTATATE
Microbiological quality	n.a.
Bacterial endotoxin	n.a.
pH (pH strips)	Depends on chemical form
Additional information
Activity available	Up to 1 GBq
Activity limit for UN2910 (excepted package) shipment	0.5 GBq in dry state or 50 MBq in liquid form
Other information