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Imaging of 212Pb in mice with a clinical SPECT/CT
Monika Kvassheim1,2, Anna Julie Kjøl Tornes3,4,5, Asta Juzeniene4,6
1Division of Radiology and Nuclear Medicine, Department of Physics and Computational Radiology, Oslo University Hospital, Oslo, Norway. mokvas@ous-hf.no.
Introduction:
212Pb is a promising radionuclide for targeted alpha therapy. Here, the feasibility of visualising the tumour uptake and biodistribution of 212Pb-NG001 in mice with a clinical SPECT/CT scanner was investigated.
Methods:
A mouse phantom with 212Pb was imaged with a clinical- and a preclinical SPECT/CT scanner. Different acquisition and reconstruction settings were investigated on the clinical system (Siemens Symbia Intevo Bold). Two athymic nude mice carrying PC-3 PIP prostate cancer tumours of 235-830 μl received 1.44 MBq of 212Pb-NG001 and were imaged 2, 6, and 24 h post-injection on the clinical SPECT/CT with a Medium Energy collimator and a 40% energy window centred on 79 keV. All acquisition times were 30 min, except the mouse imaging 24 h post-injection which was 60 min. After the final imaging, the organs were harvested and measured on a gamma counter to give an indication of how much activity was present in organs of interest at the last imaging time point.
Results:
Four volumes in the mouse phantom of ~ 300 μl with 246-303 kBq/ml of 212Pb were distinguishable on images acquired with the clinical SPECT/CT with a high number of reconstruction updates. With the preclinical SPECT, the same volumes were easily distinguished with 49 kBq/ml of 212Pb. Clinical SPECT/CT images of the mice revealed uptake in tumours and bladders 2 h after injection and in tumours containing down to approximately 15 kBq/ml at 6 and 24 h after injection.
Conclusion:
Although the preclinical scanner should be used preferentially in biodistribution studies in mice, the clinical SPECT/CT confirmed uptake in small volumes (e.g. ~ 300 μl volume with ~ 250 kBq/ml). Regardless of system, the resolution and sensitivity limits should be carefully determined, otherwise false negative or too low uptakes can be wrongly interpreted.
Insights
This study investigated visualizing 212Pb-NG001 tumor uptake in mice using clinical SPECT/CT. Clinical SPECT/CT successfully visualized tumor uptake, demonstrating its potential for targeted alpha therapy research.
Area of Science:
- Medical Imaging
- Nuclear Medicine
- Radiopharmaceutical Therapy
Background:
- Lead-212 (212Pb) is a promising radionuclide for targeted alpha therapy.
- Assessing the biodistribution and tumor uptake of 212Pb-based radiopharmaceuticals is crucial for clinical translation.
Purpose of the Study:
- To evaluate the feasibility of visualizing 212Pb-NG001 tumor uptake and biodistribution in mice using a clinical single-photon emission computed tomography/computed tomography (SPECT/CT) scanner.
- To compare the performance of a clinical SPECT/CT system with a preclinical SPECT/CT system for imaging 212Pb.
Main Methods:
- A mouse phantom containing 212Pb was imaged using both clinical and preclinical SPECT/CT scanners.
- Acquisition and reconstruction parameters were optimized on the clinical SPECT/CT system.
- Athymic nude mice bearing PC-3 PIP prostate cancer xenografts were injected with 212Pb-NG001 and imaged at various time points (2, 6, and 24 hours post-injection).
Main Results:
- The clinical SPECT/CT system could distinguish small volumes (~300 μl) of 212Pb in a phantom, although a preclinical system showed higher sensitivity.
- Tumor and bladder uptake of 212Pb-NG001 was visualized in mice.
- The clinical SPECT/CT detected tumor uptake down to approximately 15 kBq/ml at 6 and 24 hours post-injection.
Conclusions:
- Clinical SPECT/CT can visualize tumor uptake of 212Pb-NG001 in small volumes in mice, supporting its use in targeted alpha therapy research.
- While preclinical systems offer higher sensitivity, clinical SPECT/CT demonstrates feasibility for biodistribution studies.
- Careful determination of resolution and sensitivity limits is essential to avoid misinterpretation of uptake data.
