Quantitative susceptibility mapping of the rat brain after traumatic brain injury

Abstract

The primary lesion arising from the initial insult after traumatic brain injury (TBI) triggers a cascade of secondary tissue damage, which may also progress to connected brain areas in the chronic phase. The aim of this study was, therefore, to investigate variations in the susceptibility distribution related to these secondary tissue changes in a rat model after severe lateral fluid percussion injury. We compared quantitative susceptibility mapping (QSM) and R 2 * measurements with histological analyses in white and grey matter areas outside the primary lesion but connected to the lesion site. We demonstrate that susceptibility variations in white and grey matter areas could be attributed to reduction in myelin, accumulation of iron and calcium, and gliosis. QSM showed quantitative changes attributed to secondary damage in areas located rostral to the lesion site that appeared normal in R 2 * maps. However, combination of QSM and R 2 * was informative in disentangling the underlying tissue changes such as iron accumulation, demyelination, or calcifications. Therefore, combining QSM with R 2 * measurement can provide a more detailed assessment of tissue changes and may pave the way for improved diagnosis of TBI, and several other complex neurodegenerative diseases.

A Novel Rodent Model of Hypertensive Cerebral Small Vessel Disease with White Matter Hyperintensities and Peripheral Oxidative Stress

“…Susceptibility Imaging (SWI): Images were acquired using a fast-low-angle shot (FLASH) sequence, with a flip angle of 30 deg, TE/TR = 45/1090 ms and 8 averages [ 46 , 47 ]. The image matrix and resolution were the same as mentioned above.…”

Astrogliosis mapping in individual brains using multidimensional MRI

“…This neuropathological uniqueness towards astrogliosis presented an opportunity for a targeted study that provided inferences with a good degree of specificity. Conversely, very few studies have directly investigated the effect astrogliosis has on MRI diffusion and relaxation properties, and those who have did so by using animal injury models that always resulted in substantial axonal damage and other major cellular microstructural changes in addition to gliosis [13][14][15][16].…”

“…However, the successful development of noninvasive imaging techniques, primarily ones based upon magnetic resonance imaging (MRI), to make astrogliosis visible has been elusive, mainly because of the failure of conventional MRI methods to detect it, but also, and perhaps more importantly, due to the experimental difficulty of disentangling astrogliosis from the neurological condition(s) that caused it. The latter is especially true in MRI and diffusion tensor imaging (DTI) studies involving TBI animal models that result in axonal injury, demyelination, neurodegeneration, edema, or neuroinflammatory processes that are concurrent with astrogliosis [13][14][15][16]. Studying astrogliosis is particularly difficult because of the challenges of decoupling the response to cellular alterations it generates from the response to the other microstructural and chemical processes that take place due to co-morbidities [17,18].…”

Quantitative MRI susceptibility mapping reveals cortical signatures of changes in iron, calcium and zinc in malformations of cortical development in children with drug-resistant epilepsy

“…This factor was calculated from the point-spread function of the modified dipole kernel used for QSM calculation ( Schweser et al., 2013 ). For the Tikhonov-based regularization, the optimal regularization factor (α = 0.06) was calculated as the average across 10 representative subjects of the individual optimal regularization parameters calculated using the L-curve method ( Chary et al., 2021 , Hansen and O'Leary, 1993 ). Susceptibility mapping data processing is an area of active research and new methods might improve the sensitivity and specificity of the results presented here.…”