Effect of Acquisition Time and Chemical Fat Suppression on Meningeal Enhancement on MR Imaging in Dogs

Abstract

Our purpose was to characterize meningeal gadolinium enhancement on magnetic resonance (MR) imaging in dogs with inflammatory and neoplastic diseases, and to assess interobserver variability and the impact of delayed acquisition and chemical fat saturation on its conspicuity. Transverse T1-weighted FLAIR images were acquired prior to, and immediately following gadolinium injection (T0), and at 5 (T5) and 15-20 min delay (TD), with and without fat suppression, in 155 consecutive dogs imaged for suspected brain disease. The agreement on meningeal enhancement was globally substantial (kappa = 0.61) and the likelihood of obtaining a definite diagnosis was significantly increased with the use of fat suppression (P < or = 0.004). Meningeal enhancement was judged definitively present by consensus in 46 of 155 (30%) dogs. Of these, meningeal enhancement was characterized qualitatively and quantitatively in 30 dogs with a clinical diagnosis (18 inflammatory, 11 neoplastic, 1 infarct), and image sequences were compared. Meningeal enhancement was more often diffuse and leptomeningeal in animals with inflammation versus neoplasia (50% vs. 42%, and 69% vs. 48%, respectively), but significant associations were not found. Meningeal thickness and contrast ratio were higher with neoplasia (P < or = 0.02), but results did not vary significantly between series for either group. Yet, images with fat suppression were most useful 50% of the time for definite diagnosis and/or characterization of meningeal enhancement. While delayed image acquisition following gadolinium injection does not improve characterization of meningeal enhancement in dogs, fat suppression is beneficial qualitatively.

Exclusion of a Brain Lesion: Is Intravenous Contrast Administration Required after Normal Precontrast Magnetic Resonance Imaging?

“…Results may be dependent on magnetic field strength and sequence parameters 42, 43. The use of contrast‐enhanced FLAIR images,44 digital subtraction images, delayed image acquisition,14, 45, 46, 47 different doses47, 48 or other types of gadolinium‐based contrast media49 also may influence lesion detection. In this study, there was no suggestion that the utility of postcontrast sequences for lesion detection is dependent on low field magnet strength (0.2 T versus 0.23 T) or the use of different contrast agents (gadobenate dimeglumine versus gadobutrol).…”

Value of Fat Suppression in Gadolinium‐enhanced Magnetic Resonance Neuroimaging

“…1). 9 In a study comparing fat‐suppressed and nonsuppressed gadolinium‐enhanced T1‐weighted images of brains of dogs and cats, meningeal enhancement was recognized more confidently with fat suppression 19 …”

Appearance of the Canine Meninges in Subtraction Magnetic Resonance Images

“…T he meninges (dura mater, arachnoid, and pia mater) are affected by a variety of inflammatory and neoplastic conditions in dogs and, therefore, are tissues of importance for radiologists interpreting magnetic resonance (MR) images of the canine head. The lack of a blood–brain barrier in the meninges facilitates accumulation of gadolinium‐chelates, hence use of postgadolinium MR images has been emphasized for clinical examination of the meninges . Numerous clinical reports include descriptions of meningeal lesions in postgadolinium T1‐weighted MR images of dogs …”