Delineation of Femoral Lytic Lesions with xSPECT Bone in a Patient with Multiple Myeloma
Data courtesy of University of Erlangen, Erlangen, Germany
Author: Partha Ghosh, MD, Molecular Imaging Business Unit, Siemens Healthcare
A 75-year-old man with a history of multiple myeloma presented with pain in the thighs, bilaterally. Patient was referred for a 99mTc MDP bone xSPECT/CT study. Conventional 3D iterative SPECT with attenuation correction (AC) and xSPECT Bone* imaging were both performed. A thinslice diagnostic CT of the femur was performed as an integrated procedure.
xSPECT Bone showed a large lytic lesion in the upper half of the left femoral shaft and a smaller lesion just below the larger lesion. The central photopenic area with peripheral hypermetabolism is typical of a lytic lesion with peripheral bone erosion. Another similar lesion was also visualized in the lower third of the right femoral shaft. Compared to 3D iterative reconstruction, xSPECT Bone shows sharper delineation of the hypermetabolic edges of the lytic bone lesion, as well as improved delineation of the normal cortical bone of the femoral shaft and marrow cavity. Transverse reconstruction in the xSPECT* study shows improved delineation of the hypermetabolic medial margin of the lesion involving the upper part of the left femoral shaft.
CT images show lesions in the upper part of the left femoral shaft and lower third of the left femoral shaft, both of which show erosion of the inner cortical table with absence of bony expansion and without irregularities of the outer cortical surface or periosteum. No soft tissue involvement or swelling is visualized. The inner cortical table erosion without any osteoblastic activity, calcification or sclerosis within the marrow suggests a marrow lesion within filtration into and eroding the inner cortical bone. This is typical of multiple myeloma. CT also shows a small secondary lesion just below the large lesion in the left femur.
Fusion of CT and xSPECT Bone images show exact coregistration of the hypermetabolic peripheral margin of the myeloma lesions arising from the marrow to the erosion of the inner cortical table typical of the myeloma lesions. The sharp definition of the hypermetabolic rim of the lesions by xSPECT Bone helps its exact coregistration with the erosion. Focal hyperintensities in regions of the hypermetabolic peripheral rim suggest cortical zones with significantly more active erosion, which may be at risk of fracture.
Since myeloma or plasmacytomas arise from the plasma cells of bone marrow and do not show new bone formation, bone scanning has not been widely recommended for multiple myeloma work-up. X-ray, CT and MRI are the major modalities currently used. However, some cases may be associated with reactive bone changes. For example, this study shows an erosion of the inner table of the femoral shaft’s cortex; this is caused by myeloma, which causes reactive hypermetabolism as defined on xSPECT Bone. Skeletal scintigraphy plays a role in identification of such reactive changes. In patients presenting with bone pain in which skeletal scintigraphy is performed, such lesions may be unearthed.
Value of xSPECT Bone Imaging
Characterizing the reactive nature of the hypermetabolism that was seen on the rim of the lytic femoral shaft lesions, secondary to bony erosion, was made possible by the exact coregistration of the erosion in the inner cortical table with the hypermetabolic rim, which was sharply defined by xSPECT Bone. The focal areas of hyperintensity within the hypermetabolic lesional margin, defined sharply by xSPECT Bone, defined the cortical zones with exaggerated erosion that have potential for fracture.
Scanner: Symbia Intevo™* 6
Injected dose: 20 mCi 99mTc MDP
Scan delay: 3 hours post injection
Parameters: 32 frames, 25 sec/frame, 3D iterative SPECT (AC) and xSPECT Bone reconstruction
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