Maximum-likelihood reconstruction with ordered subsets in bone SPECT.
This study was aimed at determining whether the ordered-subset expectation maximum (OSEM) is more effective than filtered backprojection (FBP) for bone SPECT in the routine clinical context.


METHODS
Fifty-seven consecutive bone SPECT studies were analyzed. They included pelvic and lumbar spine, thoracolumbar spine, head and neck, feet and shoulders. A 64-projection SPECT study was acquired over 360 degrees by single-head cameras 2-3 h after the injection of 750 MBq 99mTc-methylene diphosphonate. Three observers compared the OSEM and FBP reconstructed images.


RESULTS
Streak artifacts, always present with FBP, were rarely generated with the OSEM. When present (n = 24), artifacts associated with negative values near hyperactivities in FBP were not generated with the OSEM in 67% of the cases (n = 16), permitting a satisfactory interpretation of these regions. In half of the other cases (17%, n = 4/24), interpretation was precluded. In only one case did the three observers agree that more hyperactivities were seen with the OSEM. Ninety-six percent of the OSEM pictures were superior or equal to FBP for anatomic resolution and were clearly better in 12% of the cases. The extent of the lesion with the OSEM seemed better or equally defined in 96% and clearly better in 14% of the cases. The low-activity regions were better or equally visualized in all cases and were clearly better seen in 23% of the cases. The quality of the pictures was found to be better or superior with the OSEM in 98% of the cases and definitely better in 65% of the cases.


CONCLUSIONS
Replacement of FBP by the OSEM in bone SPECT would be beneficial to clinical practice.
Blocklet
D
D
Hôpital Universitaire Erasme, Radioisotopes, Université Libre de Bruxelles, Brussels, Belgium.
Seret
A
A
Popa
N
N
Schoutens
A
A
D016477:Artifacts; D001847:Bone Diseases / Q000000981:diagnostic imaging; D001842:Bone and Bones / Q000000981:diagnostic imaging*; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D016013:Likelihood Functions; D019275:Radiopharmaceuticals; D013669:Technetium Tc 99m Medronate; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods*
D019275:Radiopharmaceuticals; D013669:Technetium Tc 99m Medronate