MR Angiography Facilitates the Differentiation of Aneurysmal from Unicameral Bone Cysts.

OBJECTIVES: The objective of this work was to evaluatethe incremental value of magnetic resonance angiography over plain radiographs and MRIfor the differentiation of aneurysmal bone cysts (ABC) from unicameral bone cysts (UBC).

METHODS: Thirty-six juvenile patients with histologically secured primary ABCs or UBCs were included in this retrospective study.Two radiologists assessed all obtained imagesin a blinded fashionusing a catalogue of previously suggestedimaging findings.A second readout with supplementary MR angiography images was performed after eight weeksto prevent observer recall bias.Diagnostic accuracy parameters were calculated for individual imaging findings, and overall diagnostic accuracy and diagnostic confidence were assessed for allreadouts. ROC curve comparison was used to determine the incremental value of MR angiography.

RESULTS: Of sixteen imaging features, only abnormal vascularization in MR angiography provided significant diagnostic accuracy for the identification of ABCs.Other imaging features such as fluid-fluid levels and internal septations were insufficient for the differentiation of UBCs from ABCs. Availability of MR angiography images significantly increased diagnostic accuracy (94.4 vs 75.0 and 83.3vs 69.4%, respectively, p < 0.05) and diagnostic confidence (4.5 vs 3.7, p < 0.05) of reading radiologists.

CONCLUSIONS: The presence of arterial feeders in magnetic resonance angiography can accurately discriminate primary aneurysmal bone cysts from unicameral bone cysts and increases the diagnostic accuracy and diagnostic confidence of reporting radiologists.

ADVANCES IN KNOWLEDGE: Radiographic differentiation of cystic bone lesions such as ABCs and UBCs remains challenging. We demonstrate that MR angiography provides incremental value and suggest inclusionin standard examination protocols.