[Magnetic resonance in XXXX : a classification based on signal behavior in multiple echo sequences].

@entity808 @entity1313 @entity75 @entity5 @entity4 @entity730 @entity1653 @entity2915 @entity816 @entity977 @entity976 @entity463 @entity2946 @entity3271
MR is generally known to be more sensitive but less specific than CT in the detection of @entity75 . In our opinion multiple echo sequences can markedly improve MR specificity in the diagnosis of @entity5 . We reviewed a series of 343 @entity5 studied with MR using multiple echo sequences and histologically verified. On the basis of the different signal patterns we divided @entity1313 into 5 classes. Class 1: the signal intensity of the @entity5 increases progressively in T2 WI (100% of @entity976 , 21/21; 100% of epidermoid @entity5 , 12/12; 81% of @entity816 (grades I to III), 64/79; 65% of @entity808 , 30/46). Class 2: the signal intensity of the lesion decreases progressively in T2 WI: A) the @entity5 has higher signal intensity than the parenchyma in all echoes (100% of @entity2946 , 14/14; 53% of @entity977 , 15/28); B) the @entity5 has the same signal intensity as the parenchyma in late echo acquisitions (100% of @entity5 , 12/12; 60% of @entity1653 , 25/41). Class 3: the @entity5 has the same signal intensity as the parenchyma in all echoes (34% of @entity1653 , 14/41). Class 4: @entity463 model: one or more cysts of high signal intensity in T2 WI and slightly hyperintense nodules and/or rings and hyperintense @entity4 (73% of @entity463 , 35/48; 72% of metastases, 18/25). Class 5: @entity3271 model: mixed @entity2915 pattern; cyst, @entity730 and @entity4 are very difficult to recognize within the lesion (95% of @entity3271 , 18/19). The signal pattern was sometimes characteristic but never pathognomonic. Nevertheless, this classification proved to be an useful criterion to restrict the number of possible diagnoses. The study of T1 and T2 values seems to be less useful.
