Using total-body PET's sensitivity to cut diagnostic tracer dose, not just scan time

Total-body PET scanners such as the uEXPLORER and PennPET Explorer cover roughly 194 cm of the body in one bed position, versus 15-35 cm for conventional PET, giving them a reported 40-fold gain in overall sensitivity. That extra sensitivity is most often spent on shortening scan time or improving image quality at a standard tracer dose, but it can equally be spent on reducing the injected activity while keeping scan time and image quality constant, which lowers radiation dose to the patient and to staff handling the syringe.

Evidence for the dose-reduction use case exists but is still limited in scale. Phantom studies on the uEXPLORER found contrast recovery for FDG images was preserved down to about 30% of standard injected activity, and healthy volunteers have been imaged with diagnostic-quality results at doses as low as 14.8-25 MBq (roughly 0.4-0.7 mCi), around 5% of a typical 10-20 mCi clinical FDG dose. A retrospective single-centre study of 88 patients with hepatic malignancies found that a tenfold reduction in injected FDG activity (about 0.37 MBq/kg versus the standard 3.7 MBq/kg) produced comparable kinetic and static image quality in both dynamic and static imaging. Total-body PET has also been used to image 68Ga-DOTATATE at roughly one-fifth of the standard clinical dose in at least one reported case, which is relevant given ongoing global gallium-68 generator supply constraints.

This is a distinct proposal from the existing total-body-PET-for-dosimetry idea in this graph, which uses total-body PET's whole-body coverage to personalise therapeutic radioligand dosing; this idea is specifically about lowering the injected activity of diagnostic tracers such as FDG, PSMA or somatostatin-receptor agents while keeping diagnostic accuracy unchanged. No large, prospective, blinded, multi-reader diagnostic-accuracy trial comparing standard-dose against substantially dose-reduced total-body PET has been reported.