The standardised uptake value (SUV) has been used as an index of glucose me
tabolism to classify malignant tumours. To date, calculation of SUVs has be
en restricted to dedicated PET. The aim of this study was to investigate th
e feasibility of SUV calculation with attenuation-corrected hybrid PET, app
lying a singles count rate-related calibration method. Calibration factors
for hybrid PET at different singles count rates were determined by phantom
studies. SUVs were determined for hot spheres in a phantom study as well as
for 68 malignant lesions in 56 patients. Recovery coefficients calculated
for hot spheres were applied to SUVs of malignant lesions to correct for pa
rtial volume and recovery effects. At a sphere-to-background ratio of 10:1,
SUVs of spheres with diameters from 34 to 16 mm varied from 5.0 to 1.5 for
hybrid PET, and from 8.0 to 4.3 for dedicated PET. SUVs of malignant lesio
ns calculated by hybrid and dedicated PET showed a strong correlation (r=0.
95, P<0.001), with a mean percentage difference of 36%. SUVs calculated by
hybrid PET were significantly lower than SUVs calculated by dedicated PET (
6.2+/-4.3 vs 8.5+/-5.3, P<0.001). Application of recovery coefficients reve
aled an SUV of 12.2+/-7.3 for hybrid PET versus 10.8+/-6.3 for dedicated PE
T, with a significant reduction in the mean percentage difference (22%, P<0
.01). In conclusion, singles count rate-related calibration factors allow c
alculation of SUVs with hybrid PET for lesions with a diameter larger than
15 mm. Correction for partial volume and recovery effects is needed to impr
ove the agreement of SUVs of lesions determined by hybrid PET and dedicated
PET.