PVA cryogel test objects for image-based quantification and functional volume segmentation in nuclear medicine

Abstract

Efforts to characterise the factors that affect the accuracy of image based quantification in nuclear medicine imaging and the development of methods to correct for them are often based in the first instance on phantom experiments using radioactive test objects. Poly-vinyl alcohol (PVA) cryogel is a tissue-equivalent material that sees widespread use as a medical imaging phantom material in other imaging modalities but is not in common use in nuclear medicine. We present a simple method to manufacture radioactive PVA cryogel test objects using moulds designed and made in house. Six spherical test objects were produced with diameters ranging from 0.5 to 4 cm without the need for an outer layer of attenuating material. The test objects were made using 10% PVA solution mixed with 177Lu to give an activity concentration of approximately 0.3 MBq ml−1. The mixture was injected into the moulds and frozen at approximately −20 °C for approximately 14 h then allowed to thaw for approximately 6 h. SPECT/CT images of the test objects were acquired both in air and with the test objects inserted into a torso phantom. The images obtained demonstrate the feasibility of our method for the production of anatomically relevant phantoms for testing image quantification and functional volume segmentation regimes.