Abstract
BackgroundRoutine single-photon emission computed tomography (SPECT) currently lacks quantitative information on regional activity concentration (ACC) of the injected tracer (e.g. kBq/ml). Furthermore, little is known on the skeletal absolute concentration of 99mTc-DPD after intravenous injection in bone scintigraphy. The aim of this study is to determine ACC in the healthy lumbar vertebrae of patients using a recently published quantitative SPECT/computed tomography (CT) protocol.MethodsLumbar vertebrae ACC estimates were performed in 50 female patients (mean age 69.88 ± 13.73 years) who had been administered 562.84 ± 102.33 MBq of 99mTc-DPD and had undergone SPECT acquisition 4 h after the injection. The SPECT/CT system was calibrated against a well counter. Images were reconstructed with Flash3D. ACC and CT tissue density were measured in volumes of interest drawn over the spongious bone tissue of the three lower lumbar vertebral bodies when these exhibited no focal CT or SPECT pathology.ResultsAverage ACC measured in the normal spongious bone tissue was 48.15 ± 13.66 kBq/ml (95% confidence interval (CI) 45.81 to 50.50 kBq/ml). This corresponds to a mean standardised uptake value (SUV) of (5.91 ± 1.54) (95% CI (5.64 to 6.17) SUV). SUV correlated significantly with Hounsfield units (HU) (r = 0.678, p < 0.0001). Significant negative correlations were observed between age and HU (r = −0.650, p < 0.0001) and between age and SUV (r = −0.385, p < 0.0001).ConclusionsThe SUVs determined for 99mTc-DPD uptake 4 h post injection are in the same range as those reported for [18F]fluoride in positron emission tomography. The strong correlation of SUV with bone CT density underlines the physiological significance of this variable. Our data suggest further investigation of the potential value of ACC measurement in the diagnosis of pathological conditions such as osteoporosis or in following up osseous metastases under therapy.
Highlights
Routine single-photon emission computed tomography (SPECT) currently lacks quantitative information on regional activity concentration (ACC) of the injected tracer
Statistical analysis In the ‘Results’ subsection, we report various quantitative measures, including bone density expressed in Hounsfield units (HU) and tracer ACC expressed in kilobecquerel per millilitre and standardised uptake value (SUV)
Mean vertebral volumes of interest (VOIs) ACC for the patient group was 48.15 ± 13.66 kilobecquerel per millilitre (kBq/ml) or 5.91 ± 1.54 SUVBW
Summary
Routine single-photon emission computed tomography (SPECT) currently lacks quantitative information on regional activity concentration (ACC) of the injected tracer (e.g. kBq/ml). Rosenthal et al predicted in 1995 that estimates of absolute SPECT tracer concentration would enter the clinical arena in the near future [1]. To date, their prediction has not come true as only few approaches to QSPECT have been established in clinical practice (for reviews, see Ritt et al [2] and Bailey et al [3]). One of the first QSPECT protocols validated in humans was reported by Willowson et al [7] who quantified the concentration of 99mTc in the cardiac cavity of patients studied by radionuclide ventriculography. As well as that by Willowson et al, involves the use of coregistered data from X-ray computed tomography (CT) to correct for attenuation and a window subtraction approach (dual energy window) to correct for scattered counts
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
