68Ga PET Ventilation and Perfusion Lung Imaging—Current Status and Future Challenges

Gallium-68 (68Ga) is a positron-emitting radionuclide suitable for positron emission tomography (PET) imaging that has a number of convenient features—it has a physical half life of 68 minutes, it is generator produced at the PET facility and needs no local cyclotron, and being a radiometal is able to be chelated to a number of useful molecules for diagnostic imaging with PET. 68Ga has recently been investigated as a radiotracer for ventilation and perfusion (V/Q) lung imaging. It is relatively easy to produce both V/Q radiopharmaceuticals labeled with 68Ga for PET studies, it offers higher spatial resolution than equivalent SPECT studies, the short half life allows for multiple (repeated) scans on the same day, and low amounts of radiotracer can be used thus limiting the radiation dose to the subject. In the usual clinical setting requiring a V/Q scan, that of suspected pulmonary embolism, the role of 68Ga V/Q PET may be limited from a logistical perspective, however, in nonacute applications such as lung function evaluation, radiotherapy treatment planning, and respiratory physiology investigations it would appear to be an ideal modality to employ.