The use of opposed-phase chemical shift MRI in the diagnosis of renal angiomyolipomas.
OBJECTIVE
The objective of our study was to determine the reliability of the location of the india ink artifact and signal loss on opposed-phase chemical shift MRI to differentiate angiomyolipomas from solid renal masses and from hemorrhagic-proteinaceous renal cysts.


METHODS
Twenty-three angiomyolipomas, 24 hemorrhagic-proteinaceous cysts, and 23 solid renal masses (nonangiomyolipomas) were retrospectively evaluated at 1.5 T with chemical shift MRI using TEs of 2.1-2.7 msec (opposed phase) and 4.8-5.3 msec (in phase). Two independent observers reviewed the MR images for signal loss on opposed-phase images and for the presence or absence of india ink artifact. An angiomyolipoma was diagnosed if the india ink artifact was identified at the interface of the mass and the kidney or was present within the renal mass.


RESULTS
Twenty-three (100%) of the 23 angiomyolipomas showed india ink artifact within the mass or at its interface with the kidney, and 18 (78.3%) of the 23 angiomyolipomas showed signal loss on opposed-phase MR images. In 24 (100%) of the 24 hemorrhagic-proteinaceous cysts, india ink artifact was not present within the mass or at its interface with the kidney. No signal loss was seen in hemorrhagic-proteinaceous cysts on opposed-phase MR images. In one (4%) of the 23 solid (nonangiomyolipoma) renal masses, the india ink artifact was identified at the interface of the mass with the kidney, and in two (9%) of the 23 masses, loss of signal was identified on the opposed-phase MR images.


CONCLUSIONS
The presence of india artifact at a renal mass-kidney interface or within a renal mass is indicative of angiomyolipoma.
Israel
Gary M
GM
Department of Radiology, New York University Medical Center, 560 First Ave., HW202, New York, NY 10016, USA. gary.israel@yale.edu
Hindman
Nicole
N
Hecht
Elizabeth
E
Krinsky
Glenn
G
D000368:Aged; D018207:Angiomyolipoma / Q000175:diagnosis*; D016477:Artifacts; D002244:Carbon; D005260:Female; D006801:Humans; D007281:Ink; D007668:Kidney / Q000473:pathology; D052177:Kidney Diseases, Cystic / Q000175:diagnosis; D007680:Kidney Neoplasms / Q000175:diagnosis*; D008279:Magnetic Resonance Imaging; D008297:Male; D012189:Retrospective Studies
C028433:chinese ink; D002244:Carbon