Added Value of SPECT/CT Fusion in Assessing Suspected Bone Metastasis: Comparison with Scintigraphy Alone and Nonfused Scintigraphy and CT

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Abstract
To evaluate retrospectively if there is additional diagnostic value of fused single photon emission computed tomographic (SPECT) and computed tomographic (CT) images in assessing possible bone metastases. Institutional review board approval was obtained, and each patient provided written informed consent. Bone scintigraphy--including planar and SPECT imaging-and CT were performed with a combined SPECT/CT system in 45 oncologic patients (24 men, 21 women; mean age, 64.7 years +/- 8.7), with a total of 42 metastatic bone foci and 40 benign foci. The reference standard was follow-up radiologic imaging. Two independent readers first analyzed only bone scintigraphic images and next analyzed two separate sets of bone scintigraphic and CT images. They then analyzed bone scintigraphic, CT, and fused images and focused on the additional value of fused images. Diagnostic confidence for each lesion was scored. The three analyses were performed 7 days apart, and the images were presented in random order at each session. The value of additional fused images was assessed by using receiver operating characteristic analysis. After review of fused images to classify indeterminate lesions, reviewer 1 became more confident in diagnosis of the 15 benign lesions and two metastases, and reviewer 2 became more confident in diagnosis of the seven benign lesions and one metastasis. The area under the receiver operating characteristic curve for reviewer 1 was 0.589 for scintigraphic images, 0.831 for separate data sets of scintigraphic and CT images, and 0.947 for fused images. The corresponding areas under the receiver operating characteristic curve for reviewer 2 were 0.771, 0.885, and 0.968, respectively. Results demonstrate the increased diagnostic confidence obtained with fused SPECT/CT images compared with separate sets of scintigraphic and CT images in differentiating malignant from benign bone lesions.