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

Efforts to characterise the factors that affect the accuracy of image based quantification in nuclear medicine imaging and the development of methods tocorrect for them are often based inthe 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 isnotincommon use innuclear medicine. We presentasimple method to manufacture radioactive PVA cryogel test objects using moulds designed and made inhouse. Six spherical test objects were produced with diameters ranging from 0.5 to4 cmwithout the need for an outer layer of attenuating material. The test objects were made using 10% PVA solution mixed with 177Lutogiveanactivity concentrationofapproximately 0.3 MBq ml-1. The mixture was injected into the moulds and frozen atapproximately -20 °C for approximately14 hthen allowed tothaw for approximately6 h.SPECT/CT imagesofthe test objects were acquired bothinair and with the test objects inserted intoatorso phantom. The images obtained demonstrate the feasibilityofour method for the productionofanatomically relevant phantoms for testing image quantification and functional volume segmentation regimes.