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1、,Osteoid osteoma is a benign bone tumor that occurs most frequently in men and boys between 7 and 25 years old .Most patients experience pain that worsens at night and is promptly relieved by the administration of salicylates 。,第1页/共33页,Typical radiographic findings of osteoid osteoma include an int
2、racortical nidus, which may display a variable amount of mineralization, accompanied by cortical thickening and reactive sclerosis in a long bone shaft.,第2页/共33页,At CT, the nidus is well defined and round or oval with low attenuation (Fig 2). An area of high attenuation may be seen centrally, a find
3、ing that represents mineralized osteoid (Fig 3).,第3页/共33页,第4页/共33页,MR imaging depicts not only the nidus and accompanying sclerosis but also adjacent bone marrow and articular abnormalities 。The nidus has low to intermediate signal intensity on T1-weighted images and variable signal intensity on T2-
4、weighted images, depending on the amount of mineralization present in the center of the nidus.,第5页/共33页,Edema in adjacent bone marrow and soft tissue and joint effusion also may be seen (Fig 3) 。Several studies have shown that, compared with CT, MR imaging is of limited value in depicting the nidus
5、。MR imaging sometimes fails to depict small nidi, because the signal in the nidus often is similar to that in cortical bone (Fig 4).,第6页/共33页,第7页/共33页,第8页/共33页,Intraarticular Osteoid Osteoma,Intraarticular osteoid osteoma, which occurs within or near a joint, is considered a separate clinical entity
6、 。The most commonly involved joint is the hip. The ankle, elbow, wrist, and knee are less commonly affected 。,第9页/共33页,Imaging findings of intraarticular osteoid osteoma differ from those of intracortical osteoid osteoma. With intraarticular osteoid osteoma, reactive cortical thickening is minimal o
7、r absent, a finding believed to be due to a lack of cambium, the inner layer of the periosteum.,第10页/共33页,第11页/共33页,第12页/共33页,Uncommon Locations of Osteoid Osteoma,Osteoid osteoma is most common in the femur and tibia; more than 50% of cases occur in these locations. Approximately 30% of osteoid ost
8、eomas occur in the spine, hands, or feet 。The least common locations are the skull, scapula, ribs, pelvis, mandible, and patella (Fig 7) 。,第13页/共33页,第14页/共33页,The most common location of spinal osteoid osteoma is the lumbar segment (Fig 8), followed by the cervical segment and the thoracic segment.
9、The sacrum is the least commonly affected spinal segment (Fig 9) 。,第15页/共33页,第16页/共33页,In the hands and feet, cancellous osteoid osteoma occurs in the carpal and tarsal bones, and all types of osteoid osteoma may occur in the metacarpal, metatarsal, and phalangeal bones (Fig 10).,第17页/共33页,第18页/共33页
10、,Confusing Imaging Findings,When osteoid osteoma is accompanied by severe inflammatory changes such as a prominent periosteal reaction, exaggerated synovial hypertrophy and joint effusion, and extensive bone marrow and soft-tissue edema, it may be difficult to reach a diagnosis 。,第19页/共33页,第20页/共33页
11、,第21页/共33页,Stress Fracture,A stress fracture appears as an infraction in the center of an area of cortical thickening, whereas osteoid osteoma appears as a round nidus (Fig 13) In a stress fracture, the extent of cortical thickening varies from a focal cortical ridge to extensive thickening that is
12、bidirectional to the periosteal and endosteal aspects. In osteoid osteoma, the extent of cortical thickening depends on the transverse and longitudinal location of the tumor in bone, but no prominent cortical ridges are present.,第22页/共33页,第23页/共33页,Intracortical Abscess,it is easier to differentiate
13、 between the two conditions at CT. In osteoid osteoma, the inner side of the nidus is smooth, and a round calcification is seen in the center of the nidus. In an intracortical abscess, the inner margin is irregular, and an irregularly shaped sequestrum is seen eccentrically (Fig 14),第24页/共33页,第25页/共
14、33页,Other Tumors and Tumorlike Lesions,Intracortical HemangiomaA typical radiographic finding of intracortical hemangioma is an intracortical osteolytic lesion with cortical thickening or periostitis (Fig 15).,第26页/共33页,第27页/共33页,Chondroblastoma.A chondroblastoma is an uncommon benign chondroid tumo
15、r that is usually less than 4 cm long. Similar to osteoid osteoma, it frequently occurs in the young and is aggressive, with periosteal reaction and extensive bone marrow edema seen at imaging 。,第28页/共33页,An epiphyseal and intramedullary location may help differentiate a chondroblastoma from an oste
16、oid osteoma, which is commonly diaphyseal and intracortical (Fig 16),第29页/共33页,第30页/共33页,OsteoblastomaAt imaging, osteoblastoma usually appears more expansile, is larger than 2 cm, and has less reactive sclerosis surrounding the mass than osteoid osteoma does (Fig 17),第31页/共33页,第32页/共33页,谢谢！,第33页/共33页,
