CASES OF THE WEEK - “Radionuclide Imaging In The Diagnosis Of Osteoid Osteoma and Spect-ct Improves Scintigraphic Accuracy Of The Diagnosis” by Dr Shekhar Shikare, Consultant & HOD, Nuclear Medicine, Dr Karim Attara, Consultant Orthopaedics & Dr Milind Raje, Consultant Radiology, NMC Royal Hospital Sharjah

CASES OF THE WEEK - “Radionuclide Imaging In The Diagnosis Of Osteoid Osteoma and Spect-ct Improves Scintigraphic Accuracy Of The Diagnosis” by Dr Shekhar Shikare, Consultant & HOD, Nuclear Medicine, Dr Karim Attara, Consultant Orthopaedics & Dr Milind Raje, Consultant Radiology, NMC Royal Hospital Sharjah

Radionuclide Imaging In The Diagnosis Of Osteoid Osteoma And Spect-ct Improves Scintigraphic Accuracy Of The Diagnosis

A 26-year-old female with a history of right shin and right tibial pain with some swelling of three years duration and seen by several doctors and was given medication but still pain persist. There is no any history of trauma prior to onset of the symptoms. Bone scan revealed focally increased tracer uptakes in mid shaft of right tibia on early and delayed static bone images (as shown with arrows) SPECT images combined with low dose CT revealed uptake at the site of a nidus considered to be osteoid osteoma (Double density sign).

CT images are usually used for attenuation correction in SPECT, to improve anatomic localization and for precise morphologic information (The double density sign, also referred to as the hotter spot within hot area sign, is a bone scan sign of an osteoid osteoma. It refers to a central focus of intense uptake (the nidus) within a surrounding lower, but nonetheless increased uptake, rim.) as shown with arrows.

CT images revealed small osteoid osteoma in the mid shaft of the right tibia anteriorly. The radiolucency may represent the nidus associated with periosteal thickening and sclerosis of the endosteal bone adjacent to the same.

Excision of the tumor and histopathology showed OSTEOID OSTEOMA (Right mid shaft tibia).

Osteoid osteoma is a painful, benign, osteoblastic lesion that occurs in younger patients and affects the extremities or the axial skeleton. While plain film findings may suggest the diagnosis, in complex anatomical regions such as the spine, pelvis, wrist and foot advanced imaging modalities are often required.

A typical nidus surrounded by sclerosis or cortical thickening characterizes osteoid osteoma on plain radiography and CT. MR is the cross-sectional imaging modality of choice for most musculoskeletal disorders. Unfortunately, extensive accompanying bone marrow edema, soft-tissue alterations, difficulty detecting the nidus, and lesion locations close to a joint (with reactive arthritis) may make a confident diagnosis of osteoid osteoma by MR imaging difficult.

Hybrid imaging with bone-seeking tracers such as SPECT/CT with 99mTc-labelled bisphosphonates combines high radionuclide uptake with morphological details and provides accurate diagnosis of osteoid osteoma and additional information for treatment planning.

This case demonstrated that fusion of the SPECT and CT images was useful to arrive at a rapid diagnosis of osteoid osteoma. While MRI is a powerful diagnostic tool, findings in the setting of osteoid osteoma may be inaccurate or misleading. It is less sensitive than CT and can overestimate the aggressiveness of a lesion.

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