David Swenson MD, Presenter: Nothing to Disclose

Damian E. Dupuy MD, Abstract Co-Author: BSD Medical, Board of Directors

Peter T. Evangelista MD, Abstract Co-Author: Consultant, BioMimetic Therapuetics, Inc

The CT vascular groove was recently reported as a moderately sensitive and highly specific sign of osteioid osteoma. This study was performed to determine how frequently this sign was present in a different cohort of patients with both typical and atypical imaging features of osteioid osteoma. Comparison with MRI images was performed to assess if a correlate of the CT vascular groove sign could be identified, providing a possible complimentary finding in this increasingly common imaging modality for the younger patient population.

The study included 24 patients who either had biopsy proven osteioid osteoma (18/24), or who had both classic clinical symptoms and typical imaging features, whose symptoms resolved after thermal ablation of the lesion (6/24). Two readers scored both CT and available MRI studies for the presence or absence of a vascular groove sign. The sign was defined on CT as thin hypodense grooves that either coursed through the surrounding sclerotic bone toward the nidus, or that clearly stood out from the background trabeculation within the medullary cavity. On MRI, the sign was defined as narrow, T1 hypointense lines seen coursing toward the nidus that demonstrated enhancement post contrast. The frequency of these findings was recorded by each reader, and interobserver agreement values were calculated.

The study involved 13 males and 11 females, with a mean age of 15 years. Of the 24 lesions, there were 16 cortical and 8 intramedullary. The vascular groove sign was identified in 73.9% of cases by reader 1, and in 78.3% by reader 2. Interobserver agreement was substantial, with a kappa value of 0.64. Only 9 patients had MRI available for comparison. An MR correlate to the vascular groove sign was identified in 55.5% of cases by reader 1, and in 33.3% by reader 2. The vascular groove sign was seen both in cortical lesions with sclerosis and in medullary based lesions without sclerosis.

This study (1) confirms that osteoid osteoma is frequently associated with a CT vascular groove sign, and (2) demonstrates that similar findings are often seen on MRI.  Further, vascular grooves may be seen not only in both cortically-based lesions with abundant reactive sclerosis, and with intramedullary lesions that lack significant sclerosis.

This study further eludicates the recently described CT vascular groove sign for osteoid osteoma, and describes MRI correlation.

Swenson, D, Dupuy, D, Evangelista, P, Osteoid Osteoma: Assessing the Vascular Groove Sign as a Characteristic Finding on Both CT and MRI.  Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, November 26 - December 2, 2011 ,Chicago IL. http://archive.rsna.org/2011/11013736.html