title: Multiparametric MRI of solid renal masses: pearls and pitfalls.
abstract: Functional imaging [diffusion-weighted imaging (DWI) and dynamic contrast enhancement (DCE)] techniques combined with T2-weighted (T2W) and chemical-shift imaging (CSI), with or without urography, constitutes a comprehensive multiparametric (MP) MRI protocol of the kidneys. MP-MRI of the kidneys can be performed in a time-efficient manner. Breath-hold sequences and parallel imaging should be used to reduce examination time and improve image quality. Increased T2 signal intensity (SI) in a solid renal nodule is specific for renal cell carcinoma (RCC); whereas, low T2 SI can be seen in RCC, angiomyolipoma (AML), and haemorrhagic cysts. Low b-value DWI can replace conventional fat-suppressed T2W. DWI can be performed free-breathing (FB) with two b-values to reduce acquisition time without compromising imaging quality. RCC demonstrates restricted diffusion; however, restricted diffusion is commonly seen in AML and in chronic haemorrhage. CSI must be performed using the correct echo combination at 3 T or T2* effects can mimic intra-lesional fat. Two-dimensional (2D)-CSI has better image quality compared to three-dimensional (3D)-CSI, but volume averaging in small lesions can simulate intra-lesional fat using 2D techniques. SI decrease on CSI is present in both AML and clear cell RCC. Verification of internal enhancement with MRI can be challenging and is improved with image subtraction. Subtraction imaging is prone to errors related to spatial misregistration, which is ameliorated with expiratory phase imaging. SI ratios can be used to confirm subtle internal enhancement and enhancement curves are predictive of RCC subtype. MR urography using conventional extracellular gadolinium must account for T2* effects; however, gadoxetic acid enhanced urography is an alternative. The purpose of this review it to highlight important technical and interpretive pearls and pitfalls encountered with MP-MRI of solid renal masses.
authors.affiliation: Department of Radiology, The Ottawa Hospital, The University of Ottawa, Civic Campus C1 1053 Carling Avenue, Ottawa, Ontario, Canada, K1Y 4E9.
authors.forename: N K
authors.initials: NK
authors.lastname: Ramamurthy
authors.affiliation: Department of Radiology, The Ottawa Hospital, The University of Ottawa, Civic Campus C1 1053 Carling Avenue, Ottawa, Ontario, Canada, K1Y 4E9.
authors.forename: B
authors.initials: B
authors.lastname: Moosavi
authors.affiliation: Department of Radiology, The Ottawa Hospital, The University of Ottawa, Civic Campus C1 1053 Carling Avenue, Ottawa, Ontario, Canada, K1Y 4E9.
authors.forename: M D F
authors.initials: MD
authors.lastname: McInnes
authors.affiliation: Division of Anatomical Pathology, The Ottawa Hospital, The University of Ottawa, 501 Smyth Road, 4th Floor CCW, Room 4278, Ottawa, Ontario, Canada, K1Y 4E9.
authors.forename: T A
authors.initials: TA
authors.lastname: Flood
authors.affiliation: Department of Radiology, The Ottawa Hospital, The University of Ottawa, Civic Campus C1 1053 Carling Avenue, Ottawa, Ontario, Canada, K1Y 4E9. Electronic address: nschieda@toh.on.ca.
authors.forename: N
authors.initials: N
authors.lastname: Schieda
mesh_terms: D018207:Angiomyolipoma / Q000175:diagnosis; D002292:Carcinoma, Renal Cell / Q000175:diagnosis; D003287:Contrast Media; D003560:Cysts / Q000175:diagnosis / Q000473:pathology; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods; D019786:Gadolinium DTPA; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D007668:Kidney / Q000473:pathology; D007680:Kidney Neoplasms / Q000175:diagnosis* / Q000473:pathology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D012372:ROC Curve; D012680:Sensitivity and Specificity
chemical_list: D003287:Contrast Media; C073590:gadolinium ethoxybenzyl DTPA; D019786:Gadolinium DTPA