Attenuation correction of somatostatin receptor SPECT by integrated low-dose CT: is there an impact on sensitivity?
OBJECTIVE
Somatostatin receptor scintigraphy (SRS) is an established imaging modality for neuroendocrine tumors (NET). Additional single photon emission computed tomography (SPECT-CT) not only permits image fusion but also attenuation correction (AC) of SPECT data. This study evaluated whether attenuation corrected SPECT-images (SPECT[AC]) are more sensitive than nonattenuation corrected SPECT-reconstructions (SPECT[NAC]) for the detection of NET lesions.


METHODS
The imaging data (planar In-111-octreotide scintigraphy and SPECT-CT) of 50 consecutive patients (28 male; 22 female; age, 34-80; mean, 65 years) with NET were included in this retrospective analysis. SPECT data were reconstructed with and without integrated CT-based AC and then analyzed by 2 experienced readers for the presence of pathologic uptake in a blinded consensus reading. Fused SPECT-CT, contemporary CT/MRI, and clinical as well as imaging follow-up served as a reference standard. All foci were rated in both the SPECT(NAC)- and SPECT(AC)-reconstructions for intensity and contrast using a 6-point-score ("0 = no uptake/no delineation from surrounding tissue" to "5 = very high uptake/very strong delineation from surrounding tissue"). The scores were analyzed in a 6 x 6 contingency table using the McNemar Bowker test.


RESULTS
A total of 222 pathologic foci were detected by SPECT(NAC) and 227 foci by SPECT(AC), respectively. In 67 of 227 foci (29.5%), focus intensity/contrast increased after AC, whereas only 5 foci showed a decrease (P < 0.001). Sensitivity increased by 2.2% (P = 0.025; 95% CI: 0.02%-4.1%) as 5 foci were detected only by SPECT(AC). However, as these 3 patients were already diagnosed with systemic disease, there was no influence on the therapeutic strategy chosen.


CONCLUSIONS
Attenuation correction of somatostatin receptor scintigraphy-SPECT significantly improves focus visualization and, albeit slightly, also significantly increases sensitivity.
Klinik für Strahlenheilkunde, Charité Centrum 6 für Diagnostische und Interventionelle Radiologie und Nuklearmedizin, Campus Virchow-Klinikum, Charité-Universitätsmedizin Berlin, Berlin, Germany.
Ingo G
IG
Steffen
Sebastian
S
Mehl
Friederike
F
Heuck
Florian
F
Elgeti
Christian
C
Furth
Holger
H
Amthauer
Juri
J
Ruf
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016477:Artifacts; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D008297:Male; D008875:Middle Aged; D018358:Neuroendocrine Tumors / Q000175:diagnosis* / Q000378:metabolism; D015282:Octreotide / Q000031:analogs & derivatives* / Q000493:pharmacokinetics; D011829:Radiation Dosage; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D017481:Receptors, Somatostatin / Q000378:metabolism; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013382:Subtraction Technique; D018511:Systems Integration; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods*; D014057:Tomography, X-Ray Computed / Q000379:methods*
D019275:Radiopharmaceuticals; D017481:Receptors, Somatostatin; C094279:indium-111-octreotide; D015282:Octreotide