Quantitative SPECT: the time is now

Abstract

Background: Quantification is one of the key benefits of nuclear medicine imaging. Recently, driven by the demand for post radionuclide therapy imaging, quantitative SPECT has moved from relative and semiquantitative measures to absolute quantification in terms of activity concentration, and yet further to normalised uptake using the standard uptake value (SUV). This expansion of quantitative SPECT has the potential to be a useful tool in the nuclear medicine armoury, but key factors must be addressed before it can meet its full potential.

Discussion: Quantitative SPECT should address an unmet clinical need and give metrics that are clinically meaningful. Using the technique in a similar manner to PET with longitudinal assessments of disease in terms of SUV is one example that meets these criteria. Having metrics that are evaluated to ensure that they are correct, that are optimised to maximise their sensitivity, and that are transferrable to allow multi-centre learning and applicability to all users of the technology are other areas of quantitative SPECT that need to be addressed and that have specific challenges associated with them. Finally, ensuring quantitative SPECT is cost-effective in times when healthcare budgets are being squeezed is also very important.

Conclusion: Quantitative SPECT offers the possibility to continue and expand the potential of quantitative nuclear medicine applications. The time is now to ensure that our community works together to make this potential a reality.

Keywords: Quantification; SPECT; SPECT-CT; SUV.

Fig. 1

Iodine-123 mIBG imaging of a 19-year-old male patient with relapsed neuroblastoma. The upper imaging and result panel are from a post-mIBG therapy study, while the lower imaging and result panel are from pre-therapy imaging. The data from post therapy imaging shows a clear quantitative metabolic response in paravertebral and sacral lesions

Fig. 2

Quantitative bone SPECT of a 69-year-old female patient with a right hip prosthesis who is experiencing bone pain. Data show degenerative changes at the L3 and L4 endplates and elevated SUV