Influence of attenuation correction by integrated low-dose CT on somatostatin receptor SPECT

Nucl Med Commun. 2007 Oct;28(10):782-8. doi: 10.1097/MNM.0b013e3282efa1a9.


Aim: Somatostatin receptor scintigraphy (SRS) is well-established in neuroendocrine tumour (NET) imaging. This study evaluated the impact of attenuation correction (AC) on SRS SPECT data in patients examined by SPECT-CT.

Methods: Planar scintigraphy and SPECT-CT of 17 patients (10 men, seven women; age, 40-74 years; mean, 62 years) suffering from NET were included. For the visual assessment of AC, the intensity and contrast of foci classified as pathological were rated in both the non-attenuation corrected (NAC) and the attenuation corrected (AC) SPECT images using a 5-point score. The change in signal intensity after AC was semiquantified two-fold for each focus in both SPECT(AC) and SPECT(NAC): firstly by using tumour-to-background (TB) ratios (defined as T(max)/B(mean)) for the determination of a TB(AC)/TB(NAC) ratio. Secondly, by a T(max,AC)/T(max,NAC) ratio. Both ratios were correlated to the focus depth.

Results: A total of 46 pathological foci were found. Focus contrast and intensity significantly increased in 14/46 foci (30%) after AC (mean, 3.7-4.0) in the visual analysis (P<0.001). While TB ratios increased only in 24/46 foci after AC and no correlation between the T(BAC)/T(BNAC) ratio and focus depth (r=0.027; P=0.856) was found, T(max) was higher after AC in all foci and the T(max,AC)/T(max,NAC) ratio showed the expected correlation to focus depth (r=0.650; P<0.01), indicating the superiority of the Tmax approach for the demonstration of the effects of attenuation correction on focal uptake.

Conclusion: Attenuation correction of SRS SPECT data by SPECT-CT results in visually more clearly contrasted foci. Moreover, as focus intensity increases, especially in the more centrally localised foci, CT-based AC has a potential to further improve the sensitivity of SRS SPECT.

MeSH terms

  • Adult
  • Aged
  • Artifacts*
  • Female
  • Humans
  • Image Enhancement / methods*
  • Male
  • Middle Aged
  • Neuroendocrine Tumors / diagnosis*
  • Neuroendocrine Tumors / metabolism
  • Radiation Dosage
  • Radiopharmaceuticals / pharmacokinetics
  • Receptors, Somatostatin / metabolism*
  • Reproducibility of Results
  • Sensitivity and Specificity
  • Somatostatin / analogs & derivatives*
  • Somatostatin / pharmacokinetics
  • Subtraction Technique
  • Tomography, Emission-Computed, Single-Photon / methods*
  • Tomography, X-Ray Computed / methods*


  • Radiopharmaceuticals
  • Receptors, Somatostatin
  • Somatostatin
  • pentetreotide