Mukesh Gobind Harisinghani MD, Abstract Co-Author: Nothing to Disclose

Kiran Patel MD, Presenter: Nothing to Disclose

Many lesions on CT scan are “indeterminate;” distinguishing benign malformations in the liver form metastatic disease remains difficult. The purpose of this study is to evaluate the efficacy of MRI in characterizing such lesions as benign or malignant, stratified according to size of lesion on presenting CT.

We identified a group of 86 non-cirrhotic patients in whom focal indeterminate liver lesion(s) were detected on a 4- or 16- slice MDCT. Lesions were categorized based upon size, i.e. 2 cm.. All patients had a subsequent MRI within 6 weeks of the initial CT. MR imaging diagnoses were classified as confidently benign, confidently malignant, or equivocal. A final diagnosis was established for all lesions either by histopathology, follow-up imaging over a period of at least 6 months, PET scan correlation, or imaging features on initial MR deemed definitely benign or malignant (i.e. requiring no follow-up).

Of 104 indeterminate lesions detected on CT, 87 lesions were benign, and 17 were malignant. The corresponding reported MR diagnoses included benign lesions (n=73), lesions that remained indeterminate (n=19), and metastatic lesions (n=12), making the overall efficacy of MR in elucidating a confident diagnosis 82%. Of 19 equivocal lesions, 14 were deemed benign, and 5 malignant. The sensitivity for the differentiation of benign from metastatic lesion is overall 84%, and in lesions 2 cm., 88%. When the definite and equivocal categories for malignancy are combined, the specificity is virtually 100%. The PPV and NPV are 100% and 55%, respectively.

Overall, MR is highly effective in the characterization of CT indeterminate liver lesions, with mild progressive increased efficacy with size of lesion. Benign MR characteristics are highly reliable - a 100% (PPV) predictor of benignity. Combined MR diagnoses of maligancny or equivocalicty yielded a 100% specificity, showing MR to be accuracte in the surveillance of malignancy.

Benign features on MR in fact reveal benignity, and malignant or equivolent features include all malignant lesions.

Harisinghani, M, Patel, K, Stratified Efficacy of MRI Diagnosis of "Indeterminate Lesions on CT.  Radiological Society of North America 2007 Scientific Assembly and Annual Meeting, November 25 - November 30, 2007 ,Chicago IL. http://archive.rsna.org/2007/5009066.html