Comparative Study Of Ground-glass Opacity Detected By X-ray Film And CT In Skeletal Lesions

Objectives: To evaluate the imaging features of the ground-glass opacityof bone lesions and to observe the constituent ratio of the GGO in differentbone lesions. To assess the value of GGO in the diagnosis of bone diseases byanalyzing the internal structure, CT value, margin and distribution of thelesions.Methods: A retrospective analysis of2386cases with bone lesionsproved surgically or pathologically from July2003to July2010in ourhospital was performed. Of these cases, those with ground-glass opacity(GGO) on X-ray film and meanwhile having CT scan as a contrast werechosen as objects of study. Lesions with ground glass density shown on X-raywere described as the group of ground-glass opacity(GGO), which wascategorized into Group tGGO (true ground-glass opacity, GGO shown on CT)and Group fGGO (false ground-glass opacity, GGO presented not on CT onlyon X-ray).On the basis of the lesion features, those with tGGO weresub-categorized into two groups: pGGO (pure ground-glass opacity) andmGGO (mixed ground-glass opacity). The differences of fibrous dysplasia ofbone and other diseases between group fGGO and tGGO were compared usingchi-squared analysis. According to the proportion of GGO area within asolitary lesion, GGO lesions were further divided into two groups: groupmGGO-A was those with the GGO area not smaller than50%; groupmGGO-B was those with the GGO area smaller than50%. The constituentratio of different diseases in group mGGO-A and group mGGO-B, distributionof lesions with GGO and their values in differential diagnosis were analyzed.CT value of GGO area in different diseases were measured. The incidence andthickness of sclerotic rim around lesions with fGGO, periosteal reaction and callus was observed. Meanwhile, the cause for fGGO was analyzed.Results: Of the2386patients with bone lesions,246contained GGO onX-ray,185contained tGGO on CT.185cases of tGGO lesions,the CT value ranged from140to600Hu inthe tGGO area. The most common lesion in this group was fibrousdysplasia(132cases,71.4%), followed by enchondroma (13,7%),osteosarcoma (9,4.9%), chondroblastoma (7,3.8%), osteosarcoma (5,2.7%),osteoblastoma (3,1.6%), chronic osteomyelitis (2,1%), Chondromyxoidfibroma (2,1%), and other diseases (10,5.4%).52cases with pGGO in decending order were fibrous dysplasia(49,94.2%), enchondroma (2,3.9%), osteosarcoma (1,1.9%).133cases withmGGO were fibrous dysplasia(83,62.4%), enchondroma (11,8.3%),osteosarcoma (9,6.8%), chondroblastoma (7,5.3%), chondrosarcoma (4,3%),osteoblastoma (3,2.3%), and other diseases (16,12%). The data was assessedby chi-square and it showed that the incidence of fibrous dysplasia in grouppGGO was higher than that in group mGGO.95cases in group mGGO-A were fibrous dysplasia (74,77.9%),osteosarcoma (6,6.3%), osteoblastoma (3,3.2%), enchondroma (2,2.1%), andchrondrosarcoma (2,2.1%) and other diseases (8,8.4%).38cases in groupmGGO-B ranked the top three were enchondroma (9.23.7%), fibrousdysplasia(9,23.7%) and chondroblastoma (7,18.4%), followed byosteosarcoma (3,7.9%), chondrosarcoma (2,5.2%), bone cyst (2,5.2%) andother diseases (6,15.8%). Chi-square statistics indicated that the incidenceof fibrous dysplasia in group mGGO-A was higher than that in groupmGGO-B.Among185cases of lesions with tGGO,218foci appeared. The mostcommon location of lesions was the femur with100focuses, including29withpGGO and71with mGGO. Of the100foci,67were fibrous dysplasia. Thenumber of lesions that occurred in craniofacial bone was12, including11withpGGO and1with mGGO. Of the12cases,11cases were fibrous dysplasia, allwith pGGO. The rest of106foci located in other bones. The incidence of pGGO in craniofacial bone was higher. Chi-square assessment displayed theconstituent ratio of fibrous dysplasia with pGGO in craniofacial bone washigher than in other locations.None of the61cases with fGGO showed GGO image on CT, with the CTvalue ranged from14.4to112Hu. The most common lesions in this groupwere fibrous dysplasia in25cases,followed by solitary bone cyst in9,aneurismal bone cyst in4, intraosseous ganglion cyst in4, langerhans cellhistiocytosis in4, nonossifying fibroma in3, giant cell tumor of bone in3,hyperparathyroidism in3, and other diseases in5. Of the61cases,46(75.4%)had sclerotic rim,7(11.5%) had periosteal reaction,4(6.6%) had callus,1hadresidue bone trabecula in the lesion, and3(4.9%) showed no featuresmentioned above.Conclusion: In skeletal lesions, GGO presented on X-ray filmapproximately1/4were not shown on CT. GGO mainly present in fibrousdysplasia, and also show in other lesions. Fibrous dysplasia with GGO hassome characteristic manifestation on CT and it was more reliable to bediagnosed with diffuse GGO in the lesion, especially of cranial bones. GGOwas shown on CT when CT value of the legion ranged from140to600Hu.Besides the large amounts of ossification and calcification in the lesions itself,the factors responsible for GGO on X-ray might be overlapping image causedby annular sclerotic rim around the lesion, periosteal reaction, and obscurecontrastive attenuation of cortex and medullary which occurs in the situationof whole bone density decrease. Thus the differential diagnosis should becombined with other signs and clinical features.