Differentiation Of Osteogenic Bone Metastases Of Bronchogeniccarcinoma And Bone Islands Using Monochromatic CT Value From Single-source Dual-energy CT

PURPOSE： To evaluate the diagnostic efficacies of single-energy CT andsingle-source Dual-energy CT in the identification of osteogenic bone metastases andbone islands.METHOD AND MATERIALS： In this retrospective study,45lesions ofosteoblastic metastases in22patients with pathologically proven malignant tumor and43lesions of bone islands in28patients were confirmed by two experiencedradiologists and one nuclear medicine physician via CT, MR and single-photonemission computed tomography (SPECT). The diameter of all lesions were0.5-1.5cm.All subjects underwent dual-energy spectral CT imaging using a highdefinition CT (Discovery CT750HD, GE). The means of140kVp-quality check (QC)CT values and SD values, virtual monochromatic (40-140keV) CT values and SDvalues, slopes (k=(HU40keV-HU100keV)/60) of the spectral curves, bone(water) andwater(bone) densities,bone (fat) and fat (bone) densities of osteogenic metastases andbone islands were measured and compared with independent-samples t-test. The lesioncenter was selected as ROI(15-55mm2）. ROC curves were used to compare thediagnostic efficacies of QC CT values and monochromatic CT values in theidentification of osteogenic bone metastases and bone islands. Z test was used tocompare areas under Roc curves.RESULTS：1. The spectral curves of the bone islands and osteoblastic bone metastases bothshowed decreasing attenuation with increasing keV values, but the slop (k) of curve ofosteoblastic metastases were significantly lower than that of bone islands.（p<0.05）。2. The mean mono-energy CT values (40-140keV) and QC CT value of osteoblasticmetastases were all significantly lower than that of bone islands (p <0.05). The area under the ROC curve for the100-140keV SD value was0.873, which was significantlyhigher than the area under the ROC curve for SD value in QC(0.791) and areas underthe ROC curve for CT values （0.696-0.741）（p<0.05）. The SD values at100-140keVhad the highest diagnostic value in differentiating BMs from SNs.3. The bone(water) density, water(bone) density, bone(fat) density and fat(bone)density of osteoblastic metastases were all significantly different from that of boneislands.（p<0.05）.The water（bone）density（223.28±270.25mg/ml） and fat(bone)density （201.17±243.43mg/ml）of osteoblastic metastases were significantly higherthan that of bone islands（-46.57±327.45、-41.89±294.94ml）.The bone(water) density（1208.07±380.82mg/ml） and bone(fat) density （1230.76±353.69mg/ml） ofosteoblastic metastases were significantly lower than that of bone islands（1579.68±469.80、1574.91±436.86mg/ml）（p<0.05）.CONCLUSION：1. Bone islands and osteoblastic metastases both showed similar spectral curve ofdecreasing type, but with different location and shape. The slope of curve in40-100keV(k) of bone islands was higher than that of osteoblastic metastases.2. The CT value and SD value of140kVp image and40-140keV monochromaticimages would be reliable in differential diagnosis of osteogenic bone metastases andbone islands. The SD values at100-140keV had the highest diagnostic value.3. The bone(water) density, water(bone) density, bone(fat) density and fat(bone)density of osteoblastic metastases were all significantly different from that of boneislands. The material decomposition image is useful in differential diagnosis ofosteoblastic metastases and bone islands.