Ⅲ-3. Radiochemistry & Nuclear Chemistry

RIKEN Accel. Prog. Rep. 56 (2023)
RIKEN
Accel. Prog. Rep. 56 (2023)

44m

Sc-DOTA-TATE imaging with a cancer disease mouse model for
multiple-isotope PET imaging

T. Fukuchi,∗1 Y. Kanayama,∗1 Y. Nakatani,∗1 A. Nambu,∗2 S. Usuda,∗2 Y. Shigekawa,∗2 X. Yin,∗2 H. Haba,∗2and Y. Watanabe∗1
Positron emission tomography (PET) is a powerful tool for the visualization of radiotracer distribution
used for imaging diagnosis in medical and fundamental
life sciences. However, standard PET is only useful forsingle-tracer imaging because of the energy constancyof annihilation photons, which are utilized for PETimaging. To enhance the usefulness of PET, we developed a new PET system that can be used for simultaneous multi-tracer PET imaging, named multipleisotope PET (MI-PET).1,2)
A positron emitter 44m Sc is one of the MI-PET nuclides. MI-PET utilizes a prompt γ-ray to identify
the tracer nuclide in addition to coincidence measurement of positron-electron annihilation photons, whichis used for conventional PET systems. 44m Sc is a betaplus decay nuclide with a half-life of 58.6 h and emits
1157 keV prompt γ-ray successively after positronemission. As a preliminary study for future multitracer imaging, we conducted single-tracer PET imaging experiment using a cancer mouse model with 44m Sc
labelled drug.
For future multi-tracer imaging, we synthesized atracer labelled by an MI-PET nuclide 44m Sc (positron
prompt γ-ray emitter) and tested for accumulation
on cancer cells. For the experiment, we synthesized a 44m Sc labelled DOTA-TATE (DOTA-[Tyr3 ]octreotide), which is a compound containing tyrosine3 octreotate and somatostatin receptor for numerous
malignancies.
The labelling protocol was basedon a method developed by Huclier-Markai et al.3,4)
DOTA-TATE was purchased from BACHEM (Switzer44m
Sc was produced via the reaction ofland).
44Ca(d, 2n)44m Sc with a 24-MeV deuteron beam at theRIKEN AVF cyclotron and puriﬁed by ion-exchanges.
The produced 44m Sc was transported to the RIKEN
Kobe campus for the drug synthesis. A total of0.2 nmol of DOTA-TATE and 5 MBq of 44m Sc wereadded into NaOH 95◦ C for 30 min with shaking. Afterincubation, 1.1 MBq of 95◦ C for 30 min with shaking.
After incubation, 1.1 MBq of 44m Sc labelled DOTATATE was puriﬁed using a C18 solidphase extraction
column. The labelling ratio for 44m Sc-DOTA-TATE
was approximately 30%.
We prepared an 8-week-old immunodeﬁcient male
mouse transplanting pancreatic tumoral cell (AR42J)5)
as a cancer disease animal model. For the imaging
experiment, 1.1 MBq of 44m Sc-DOTA-TATE was administered via the tail vein. After 1 min from admin∗1∗2RIKEN Center for Biosystems Dynamics ResearchRIKEN Nishina Center- 160 -istration, a 90-min scan of the mouse abdomen wasperformed under anaesthesia using the MI-PET system.1) The experimental setting for the mouse imaging is shown in Fig. 1. All animal experiments in thisstudy received ethical approval by the institutional review board of RIKEN and were performed in accordance with the guidelines for care and use of laboratory
animals.

Fig. 1. Experimental setting for the mouse imaging using
MI-PET system.

Figure 2 shows a photograph and reconstructed image of a mouse. In this reconstructed image, weFig. 2. A photograph (left) and reconstructed image (right)of a mouse administrated with 44m Sc-DOTA-TATE.
Image is reconstructed by conventional PET events,
namely coincidence measurement of the annihilation
photons without prompt γ-ray detection.

Ⅲ-3. Radiochemistry & Nuclear Chemistry

RIKEN Accel. Prog. Rep. 56 (2023)

can clearly observe the accumulation of 44m Sc-DOTATATE in AR42J cancer. In the future, we will perform imaging experiments for multi-drug comparisonon animal disease models using 44m Sc-DOTA-TATE
and other PET tracers, such as 18 F-FDG.
References
1) T. Fukuchi et al., Med. Phys. 40, 2257 (2017).
2) T. Fukuchi et al., J. Instrum. 16, P01035 (2021).
3) S. Huclier-Markai et al., Nucl. Med. Biol. 41, e36 (2014).
4) T. Fukuchi et al., RIKEN Accel. Prog. Rep. 55, 142(2022).
5) J. Christophe, Am. J. Physiol. 266, G963 (1994).

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