The Imaging Features Of Osseous Langerhans Cell Histicytosis

Object To study the X-ray, CT and MRI features of osseous Langerhans Cell Histicytosis(LCH) especially the MRI manifestation, and to investigate the diagnostic value of different imaging methods.Methods The X-ray, CT and MRI findings of 12osseous LCH proved by surgery and phathology were analyzed to observe their features and compared to each other, and the diagnostic value of different imaging methods were studied.Results The X-ray, CT features: lesions which were not located in spine appear lytic.2 patients had slightly sclerostic margins. 4 lesisons contained sequestra on CT and weren't visible on X-ray.Surrounding zones of bone sclerosis were seen in 2 patients and 1 of them coupled with periosteal new bone formation.3 lesions eroded cortex and had extraosseous sofe tissue extensions.Soft tissue edema was seen in 1 patient. All lesions in spine located in vertebra bodies and collapsed to produce the appearance of vertebra plana with different degrees. The intervertebral disk spaces were isodense . 3 skull lesions and 2 spinal lesions were at incipient phase, the other lesions were at mid-phase.MRI features: signal intensities of 3 lesions which were not located in spine were low and 5 were intermediate on T1-weighted imaging.The signal intensities of the lesions of 4 lesions on T2WI were high.Hemogenicity of signal was denonstrated on both T1WI and T2WI. All lesions were hyperintense on fat-suppressed sequence,and 3 lesions had peripheral hypointense rims 1 of which had sclerotic margins on CT. 5 lesions had peritumoral edemata and were at incipient and mid-phase, 2 of them had surrounding zones of bone sclerosis, 1 had stripe-like periosteal new bone formation. Sofe tissue edema was seen in 6 patients 5 of which hadn't been seen on CT.Soft tissue extension in 3 lesions on CT were seen clearly on MRI. 9 of 11 spinal lesions had appearance of vertaebra plana with different degrees.The signal intensity of adjacent intervertebral disks was homogeneous.9 intervertebral spaces were presersved, and 12 were slightly widened.Conclusions Radiographic appearance of osseous LCH depends on site of involvement and phase of the disease.During the early phase,there is a more aggressive pattern of moth-eaten or permeative osteolysis with poorly defined borders.When the cortex is destroyed the lesion extends into the soft tissue coupled with periosteal new bone formation and pathologic fracture.With the lesions progressing, the borders get clear and form expanded appearance, the periostitis resolves. The lesions may resolve completely without treatment or have a sclerotic appearance due to periosteal new bone formation. On MRI, osseous LCH appear as areas of marrow replacement, giving intermediate signal intensity on T1WI and high or most high signal intensity on T2WI, and the signal intensities are either homogenous or heterogenous.The hypointense rims don't relate to sclerotic margins on CT and suggest reparative bone formation and reflect a healing stage and good prognosis.The bone marrow edema surrouding the lesions is hypointense on T1WI and hyperintense on T2WI with poorly-defined or well-defined margins, and often couples with adjacent sofe tissue edema. The peritumoral marrow and soft tissue edema is non-specific inflammatory response to the primary osseous insult suggesting the lesion is at early phase and has aggressive appearance.Different imaging methods have their own advantages and disadvantages and can't be replaced with each other. The correct diagnosis can be made by combining the different imaging findings and the clinical data.