Quantitative ^99mTc-MDP SPECT/CT as an alternative to ¹⁸F-NaF PET/CT for objective assessment of osteoblastic bone...

To investigate the correlation between the standardized uptake value (SUV) metrics derived from technetium-99m (^99mTc) methylene diphosphonate (MDP) single photon emission computed tomography/computed tomography (SPECT/CT) and fluorine-18 (¹⁸F) sodium fluoride (NaF) positron emission tomography (PET)/CT.

A total of 129 metastatic lesions from 14 patients who underwent both ^99mTc-MDP SPECT/CT and ¹⁸F-NaF PET/CT within one month were included in the analyses. The lesions with markedly increased uptake were semi-automatically segmented into a volume of interest in both SPECT and PET images by taking the 42% of maximum uptake as a threshold. Maximum, average and minimum SUV (namely, SUVmax, SUVmean and SUVmin) were recorded for each lesion. The strength of correlation was evaluated with Pearson's correlation analysis.

The correlation coefficitients for SUVmax, SUVmean and SUVmin derived SPECT and PET images were 0.652, 0.653 and 0.635, respectively (all P<0.001). Lesions with a volume of at least 5cm³ demonstrated a stronger correlation, increasing the correlation coefficients to 0.714, 0.724 and 0.686, respectively (all P<0.001). The strongest correlation was seen in the lesions of the appendicular skeleton, with coefficients for SUVmax, SUVmean and SUVmin being 0.769, 0.791 and 0.761, respectively (all P<0.001).

The SUV metrics derived from ^99mTc-MDP SPECT/CT strongly correlate with ¹⁸F-NaF PET, especially for relatively large lesions located in the appendicular skeleton. Technetium-99m-MDP SPECT/CT could potentially be used as an alternative method to ¹⁸F-NaF PET/CT for quantitative evaluation and objective follow-up of bone metastases.