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A Journal on Nuclear Medicine and Molecular Imaging
Affiliated to the and to the International Research Group of Immunoscintigraphy
Indexed/Abstracted in: Current Contents/Clinical Medicine, EMBASE, PubMed/MEDLINE, Science Citation Index (SciSearch), Scopus
Impact Factor 2,413
Online ISSN 1827-1936
THE REPRODUCTIVE SYSTEM
Guest Editors: Freeman L. M., Bombardieri E.
Etchebehere E. C. S. C. 1,2, Macapinlac H. A. 1, Gonen M. 3, Humm K. 1, Yeung H. W. D. 1, Akhurst T. 1, Scher H. I. 4, Larson S. M. 1
1 Nuclear Medicine Service, Department of Radiology, Memorial Sloan-Kettering Cancer Center, New York, USA
2 Division of Nuclear Medicine, Department of Radiology School of Medical Sciences, Campinas State University Unicamp, Campinas, Brazil
3 Department of Epidemiology and Biostatistics, and
4 Genito-Urinary Oncology Service, Department of Medicine Memorial Sloan Kettering Cancer Center, New York, USA
Background. Recently, iterative reconstruction with segmented attenuation corrections (IRSAC) has been introduced for reconstruction of 18F-FDG PET images. IRSAC produces images that are more pleasing to the eye, but qualitative and quantitative comparisons between IRSAC and filtered back projection (FBP) have not been reported for metastatic cancer. Since quantitative data has been widely used as an adjunct to interpretation of PET scans, comparison between IRSAC and FBP is needed. The purpose of this study was to compare image quality and the maximum standardized uptake value (SUVmax) obtained with FBP and with IRSAC in metastatic lesions from prostate cancer.
Methods. Twenty 18F-FDG PET scans (10 baseline and 10 follow-up) were performed in 10 patients with prostate cancer (ages 66-85 yrs, mean 73.6 yrs). Acquisition began 45 min after injection of 370 MBq of 18F-FDG. Images were reconstructed using FBP and IRSAC, and submitted to visual and quantitative analysis. SUVmax was obtained for all metastases, on FBP and IRSAC. A Jaszczak phantom study was also performed.
Results. IRSAC images showed better image quality than FBP especially in regions of high activity concentrations. IRSAC detected 106 lesions on both baseline and follow-up scans, while FBP detected 100 and 95 lesions on baseline and follow-up scans, respectively. Therefore, 17 more lesions were seen on IRSAC. The mean SUVmax values on baseline scans for FBP and IRSAC were systematically different, at 4.46±1.99 and 5.13±2.67, respectively. On follow-up scans values were 3.89±1.72 for FBP and 4.29±1.93 for IRSAC. Comparison of FBP with IRSAC on baseline and follow-up scans were statistically significant (baseline: paired “t”-test p=0.0017; follow-up: paired “t”-test p=0.0008). Phantom studies reveal that these differences can be explained by the type of reconstruction filters used, and IRSAC was more accurate than FBP.
Conclusions. IRSAC detects smaller volumes in phantoms, patient images are easier to interpret and more metastatic lesions were detected. In addition, IRSAC provides reproducible quantitative data, comparable to data provided by FBP. IRSAC SUV and FBP SUV are in close agreement but there was a statistically significant difference between the two, and therefore threshold values of SUV will probably need to be re-determined with IRSAC, and are likely to be 10 to 19% higher than currently reported.