Intracranial Lesion Detection and Artifact Characterization: Comparative Study of Susceptibility and T2*-Weighted Imaging in Dogs and Cats

Abstract

Susceptibility-weighted imaging (SWI), an MRI sequence for the detection of hemorrhage, allows differentiation of paramagnetic and diamagnetic substances based on tissue magnetic susceptibility differences. The three aims of this retrospective study included a comparison of the number of areas of signal void (ASV) between SWI and T2*-weighted imaging (T2*WI), differentiation of hemorrhage and calcification, and investigation of image deterioration by artifacts. Two hundred twelve brain MRIs, 160 dogs and 52 cats, were included. The sequences were randomized and evaluated for presence/absence and numbers of ASV and extent of artifacts causing image deterioration by a single, blinded observer. In cases with a CT scan differentiation of paramagnetic (hemorrhagic) and diamagnetic (calcification) lesions was made, SWI was performed to test correct assignment using the Hounsfield Units. Non-parametric tests were performed to compare both sequences regarding detection of ASV and the effect of artifacts on image quality. The presence of ASV was found in 37 SWI sequences and 34 T2*WI sequences with a significant increase in ASV only in dogs >5 and ≤ 15 kg in SWI. The remaining weight categories showed no significance. CT examination was available in 11 cases in which 81 ASV were found. With the use of phase images, 77 were classified as paramagnetic and none as diamagnetic. A classification was not possible in four cases. At the level of the frontal sinus, significantly more severe artifacts occurred in cats and dogs (dogs, p < 0.001; cats, p = 0.001) in SWI. The frontal sinus artifact was significantly less severe in brachycephalic than non-brachycephalic dogs in both sequences (SWI, p < 0.001; T2*WI, p < 0.001). In conclusion, with the advantages of better detection of ASV in SWI compared with T2*WI and the opportunity to differentiate between paramagnetic and diamagnetic origin in most cases, SWI is generally recommended for dogs. Frontal sinus conformation appears to be a limiting factor in image interpretation.

Ex vivo susceptibility-weighted imaging anatomy of canine brain–comparison of imaging and histological sections

“…In addition to providing high anatomical detail, SWI detects hemosiderin, and therefore microbleeds, with high sensitivity. Recent studies carried out in dogs have demonstrated the superiority of SWI over conventional gradient echo sequences in the detection of microbleeds associated with traumatic brain injury (Noh et al, 2019 ; Weston et al, 2020 ; Wolfer et al, 2021 ). SWI could also improve the diagnosis of other intracranial diseases of the dog, such as cerebral amyloid angiopathy (CAA), a disorder characterized by amyloid accumulation in the walls of cerebral blood vessels that can be accompanied by microbleeds.…”

“…This technique has also been performed in dogs to monitor traumatic brain injury, detect hemorrhage, or identify intracranial venous abnormalities (Noh et al, 2019 ; Weston et al, 2020 ; Wolfer et al, 2021 ). However, no atlas of the canine brain structures revealed by SWI is currently available, even though it is essential for translational research and in veterinary practice.…”

“…In human patients, SWI has mainly been used to detect and monitor (i) microbleeds in traumatic brain injuries (Liu et al, 2012(Liu et al, , 2015, (ii) oxygen saturation changes in stroke and intracranial hypertension (Broderick et al, 1993;Haacke et al, 1997Haacke et al, , 2010Plantinga et al, 2014), and (iii) iron accumulation in neurodegenerative diseases such as Parkinson's disease, multiple sclerosis, Huntington's disease, and neuroferritinopathy (Haacke et al, 2004;Martin et al, 2008;Péran et al, 2010;Langkammer et al, 2012Langkammer et al, , 2016Liu et al, 2015). This technique has also been performed in dogs to monitor traumatic brain injury, detect hemorrhage, or identify intracranial venous abnormalities (Noh et al, 2019;Weston et al, 2020;Wolfer et al, 2021). However, no atlas of the canine brain structures revealed by SWI is currently available, even though it is essential for translational research and in veterinary practice.…”

Susceptibility artifact morphology is more conspicuous on susceptibility‐weighted imaging compared to T2* gradient echo sequences in the brains of dogs and cats with suspected intracranial disease

“…[4][5][6][7][8][9][10][11][12][13][14][15][16][17] In recent years, high-field MRI units have become progressively more widespread in veterinary hospitals and SWI is beginning to be introduced to MRI protocols. [18][19][20][21][22] Based on advice of an MRI Applications Specialist, this sequence was therefore added to our hospital's standard brain imaging protocol in 2019. Only two studies have been published in recent veterinary literature concerning the comparison between SWI and T2*-weighted GE.…”

“…Only two studies have been published in recent veterinary literature concerning the comparison between SWI and T2*-weighted GE. 19,20 Another study explored the diagnostic value of SWI in comparison to conventional MRI sequences. 18 The purposes of this study were therefore to describe 1) the conspicuity and number of ASV based on SWI and T2* weighted GE pulse sequences in a large population of dogs and cats presenting with intracranial signs due to different neurological diseases; and 2) whether SWI will distinguish between tortuous tubular ASV (representing blood vessels in human literature) and amorphous ASV (representing micro or macro-bleedings in human medicine) more readily than T2* weighted GE images.…”