Outlines requirements and time allocation 4.Periosteal new bone formation 15min Which is a nonspecific response of the periosteum to a variety of causes:it may be focal or diffuse. In particular a spiculated"sunburst"pattem with undercutting of the margins possible causes including physiological,congenital.infective.inflammatory. traumatic.metabolic.neoplastic and idiopathic. The radiographic appearance may (Codmans triangle)suggests a primary bone malignancy:lkewise a laminated"onion skin"pattem can be seen with an aggressive lesion. 5、Sequestrum 15min .Sequestrum is a fragment of necrotic bone that becomes separated from healthy bone. Sequestra may occur in various conditions.such as osteomyelitis,tuberculous arthritis,tropical ulcer and non-Hodgkin's lymphoma a sharply marginated bone lesion is seen as radiodense bone spicules caused by osseous necrosis.The sequestrum frequently lies in a space surrounded by granulation tissueOutlines, requirements and time allocation 4、Periosteal new bone formation ⚫ Which is a nonspecific response of the periosteum to a variety of causes; it may be focal or diffuse. ⚫ In particular a spiculated "sunburst" pattern with undercutting of the margins possible causes including physiological, congenital, infective, inflammatory, traumatic, metabolic, neoplastic and idiopathic. ⚫ The radiographic appearance may (Codmans triangle) suggests a primary bone malignancy; likewise a laminated "onion skin" pattern can be seen with an aggressive lesion. 5、Sequestrum ⚫ Sequestrum is a fragment of necrotic bone that becomes separated from healthy bone. ⚫ Sequestra may occur in various conditions, such as osteomyelitis, tuberculous arthritis, tropical ulcer and non-Hodgkin's lymphoma ⚫ a sharply marginated bone lesion is seen as radiodense bone spicules caused by osseous necrosis. The sequestrum frequently lies in a space surrounded by granulation tissue. 15min 15min