title: 3D SPECT/CT fusion using image data projection of bone SPECT onto 3D volume-rendered CT images: feasibility and clinical impact in the diagnosis of bone metastasis.
abstract: OBJECTIVE
  We developed a method of image data projection of bone SPECT into 3D volume-rendered CT images for 3D SPECT/CT fusion. The aims of our study were to evaluate its feasibility and clinical usefulness.
  
  
  METHODS
  Whole-body bone scintigraphy (WB) and SPECT/CT scans were performed in 318 cancer patients using a dedicated SPECT/CT systems. Volume data of bone SPECT and CT were fused to obtain 2D SPECT/CT images. To generate our 3D SPECT/CT images, colored voxel data of bone SPECT were projected onto the corresponding location of the volume-rendered CT data after a semi-automatic bone extraction. Then, the resultant 3D images were blended with conventional volume-rendered CT images, allowing to grasp the three-dimensional relationship between bone metabolism and anatomy. WB and SPECT (WB + SPECT), 2D SPECT/CT fusion, and 3D SPECT/CT fusion were evaluated by two independent reviewers in the diagnosis of bone metastasis. The inter-observer variability and diagnostic accuracy in these three image sets were investigated using a four-point diagnostic scale.
  
  
  RESULTS
  Increased bone metabolism was found in 744 metastatic sites and 1002 benign changes. On a per-lesion basis, inter-observer agreements in the diagnosis of bone metastasis were 0.72 for WB + SPECT, 0.90 for 2D SPECT/CT, and 0.89 for 3D SPECT/CT. Receiver operating characteristic analyses for the diagnostic accuracy of bone metastasis showed that WB + SPECT, 2D SPECT/CT, and 3D SPECT/CT had an area under the curve of 0.800, 0.983, and 0.983 for reader 1, 0.865, 0.992, and 0.993 for reader 2, respectively (WB + SPECT vs. 2D or 3D SPECT/CT, p < 0.001; 2D vs. 3D SPECT/CT, n.s.). The durations of interpretation of WB + SPECT, 2D SPECT/CT, and 3D SPECT/CT images were 241 ± 75, 225 ± 73, and 182 ± 71 s for reader 1 and 207 ± 72, 190 ± 73, and 179 ± 73 s for reader 2, respectively. As a result, it took shorter time to read 3D SPECT/CT images than 2D SPECT/CT (p < 0.0001) or WB + SPECT images (p < 0.0001).
  
  
  CONCLUSIONS
  3D SPECT/CT fusion offers comparable diagnostic accuracy to 2D SPECT/CT fusion. The visual effect of 3D SPECT/CT fusion facilitates reduction of reading time compared to 2D SPECT/CT fusion.
authors.affiliation: Department of Diagnostic Radiology, School of Medicine, Keio University, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Ogata
authors.affiliation: Department of Diagnostic Radiology, School of Medicine, Keio University, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan. nakahara@rad.med.keio.ac.jp.
authors.forename: Tadaki
authors.identifier: http://orcid.org/0000-0002-7382-0806
authors.initials: T
authors.lastname: Nakahara
authors.affiliation: Department of Diagnostic Radiology, School of Medicine, Keio University, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan.
authors.forename: Kenichi
authors.initials: K
authors.lastname: Ode
authors.affiliation: Department of Diagnostic Radiology, School of Medicine, Keio University, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan.
authors.forename: Yohji
authors.initials: Y
authors.lastname: Matsusaka
authors.affiliation: Department of Diagnostic Radiology, School of Medicine, Keio University, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan.
authors.forename: Mari
authors.initials: M
authors.lastname: Katagiri
authors.affiliation: Department of Diagnostic Radiology, School of Medicine, Keio University, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan.
authors.forename: Yu
authors.initials: Y
authors.lastname: Iwabuchi
authors.affiliation: Department of Diagnostic Radiology, School of Medicine, Keio University, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan.
authors.forename: Kazunari
authors.initials: K
authors.lastname: Itoh
authors.affiliation: Department of Diagnostic Radiology, School of Medicine, Keio University, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan.
authors.forename: Akira
authors.initials: A
authors.lastname: Ichimura
authors.affiliation: Department of Diagnostic Radiology, School of Medicine, Keio University, 35 Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Jinzaki
mesh_terms: D000368:Aged; D019540:Area Under Curve; D001859:Bone Neoplasms / Q000000981:diagnostic imaging* / Q000378:metabolism / Q000556:secondary*; D001842:Bone and Bones / Q000000981:diagnostic imaging* / Q000378:metabolism; D005240:Feasibility Studies; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008297:Male; D015588:Observer Variation; D010363:Pattern Recognition, Automated; D012372:ROC Curve; D000072098:Single Photon Emission Computed Tomography Computed Tomography / Q000379:methods*; D051598:Whole Body Imaging / Q000379:methods
keywords: Bone metastasis; Image fusion; SPECT/CT; Three-dimensional; Volume rendering