Vanadium-48: A renewable source for transmission scanning with PET

A 68Ge (t1/2=271 d) source is normally used to produce transmission images for PET studies. New PET scanners utilize two or three 10-15 mCi 68Ge sources for this purpose. 48V (t1/2=15.98 d) has been investigated as an alternative to 68Ge for routine transmission scanning in PET. A target system has been developed to produce nearly homogeneous (+/- 10%) sources of 1 mCi/cm (10 mCi over 10 cm) using the 48Ti(p, n)48V reaction (Ep=17 MeV). The target consists of a small diameter (3.17 mm) Ti tube (>99.99% Ti, 73.7% 48Ti) oriented at 6 to the incident proton beam and held rigidly within a water cooled aluminum target body. The Ti tube wall presents an effective target thickness of 8.5 mm to the grazing proton beam. The Ti tube is water cooled. Typical irradiations of 20 μA for 120 min on the tube yield 10 mCi sources. Short-lived 47V (t1/2=32.6 min) and 46V (t1/2=422 ms) impurities are allowed to decay prior to utilizing the source for routine PET transmission scanning. Ti tubes are reused to produce new sources each week. (orig.)