title: Influence of attenuation correction by integrated low-dose CT on somatostatin receptor SPECT.
abstract: OBJECTIVE
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Klinik für Strahlenheilkunde, Charité, Centrum 6 für diagnostische und interventionelle Radiologie und Nuklearmedizin, Charité--Universitätsmedizin Berlin, Germany. juri.ruf@charite.de
authors.forename: Juri
authors.initials: J
authors.lastname: Ruf
authors.forename: Ingo
authors.initials: I
authors.lastname: Steffen
authors.forename: Sebastian
authors.initials: S
authors.lastname: Mehl
authors.forename: Christian
authors.initials: C
authors.lastname: Rosner
authors.forename: Timm
authors.initials: T
authors.lastname: Denecke
authors.forename: Ulrich-Frank
authors.initials: UF
authors.lastname: Pape
authors.forename: Michail
authors.initials: M
authors.lastname: Plotkin
authors.forename: Holger
authors.initials: H
authors.lastname: Amthauer
mesh_terms: D000328:Adult; D000368:Aged; D016477:Artifacts; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D008297:Male; D008875:Middle Aged; D018358:Neuroendocrine Tumors / Q000175:diagnosis* / Q000378:metabolism; D011829:Radiation Dosage; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D017481:Receptors, Somatostatin / Q000378:metabolism*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013004:Somatostatin / Q000031:analogs & derivatives* / Q000493:pharmacokinetics; D013382:Subtraction Technique; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods*; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D019275:Radiopharmaceuticals; D017481:Receptors, Somatostatin; D013004:Somatostatin; C081788:pentetreotide