Medical Physics Research Today is a free monthly online journal that collates and summarizes the latest research about Medical Physics, including details on medicine, radiotherapy, biomechanics, medical imaging. | ||||||||
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Enhancement patterns of focal liver masses: discordance between contrast-enhanced sonography and contrast-enhanced CT and MRI.Wilson SR, Kim TK, Jang HJ, Burns PN Department of Medical Imaging, Toronto General Hospital, 585 University Ave., Toronto, ON, Canada, M5G 2N2. stephanie.wilson@uhn.on.ca OBJECTIVE: The purpose of this study was to investigate the origin of the infrequent discordance between the contrast enhancement patterns of liver lesions on sonography and those on CT and MRI. Forty-four discordant cases were reviewed retrospectively. CONCLUSION: Four categories of discordance were identified, one of which is unexplained. Contrast agent diffusion caused portal venous phase discordance in malignant tumors (n = 6) whereby CT and MRI contrast material diffused through the vascular endothelium into the tumor interstitium, concealing washout. Sonographic microbubbles were purely intravascular and showed washout. Arterial phase timing discordance occurred in metastatic lesions (n = 10) with hypervascularity and rapid washout on contrast-enhanced sonography. CT arterial imaging performed later showed hypovascularity. Rapidly enhancing hemangiomas (n = 7) exhibited hypervascularity on CT when contrast-enhanced sonography also showed peripheral nodules and fast centripetal progression. Discordance caused by fat in lesions (n = 4) or liver (n = 10) reflected the inherent echogenicity of fat on sonography compared with its low attenuation on CT and low signal intensity on MRI. Infrequent cases of discordance remain unexplained. Recognition of the cause of the infrequent disagreement in enhancement patterns on contrast-enhanced sonography with those on CT and MRI improves diagnostic interpretation. Published 20 June 2007 in AJR Am J Roentgenol, 189(1): W7-W12.
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