Preserving Preclinical PET Quality During Intratherapeutic Imaging in Radionuclide Therapy with Rose Metal Shielding Reducing Photon Flux

• Performing PET imaging during ongoing radionuclide therapy can be a promising method to follow tumor response in vivo. However, the high therapeutic activity can interfere with the PET camera performance and degrade both image quality and quantitative capabilities. As a solution, low-energy photon emissions from the therapeutic radionuclide can be highly attenuated, still allowing sufficient detection of annihilation photons in coincidence. Methods: Hollow Rose metal cylinders with walls 2-4 mm thick were used to shield a 22Na point source and a uniform phantom filled with 18F as they were imaged on a preclinical PET camera with increasing activities of 177Lu. A mouse with a subcutaneous tumor was injected with 18F-FDG and imaged with an additional 120 MBq of 177Lu and repeated with shields surrounding the animal. Results: The addition of 177Lu to the volume imaged continuously degraded the image quality with increasing activity. The image quality was improved when shielding was introduced. The shields showed a high ability to produce stable and reproducible results for both spatial resolution and quantification of up to 120 MBq of 177Lu activity (maximum activity tested). Conclusion: Without shielding, the activity quantification will be inaccurate for time points at which therapeutic activities are high. The suggested method shows that the shields reduce the noise induced by the 177Lu and therefore enable longitudinal quantitative intratherapeutic imaging studies.

Ämnesord

MEDICIN OCH HÄLSOVETENSKAP  -- Klinisk medicin -- Radiologi och bildbehandling (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Clinical Medicine -- Radiology, Nuclear Medicine and Medical Imaging (hsv//eng)

NATURVETENSKAP  -- Fysik -- Annan fysik (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences -- Other Physics Topics (hsv//eng)

Nyckelord

count losses

PET

radionuclide therapy

shielding

small-animal imaging

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