Purpose To develop an anomalous (non-Gaussian) diffusion model for characterizing skeletal muscle perfusion using multi-b-value DWI.Theory and methods Fick's first law was extended for describing... Show morePurpose To develop an anomalous (non-Gaussian) diffusion model for characterizing skeletal muscle perfusion using multi-b-value DWI.Theory and methods Fick's first law was extended for describing tissue perfusion as anomalous superdiffusion, which is non-Gaussian diffusion exhibiting greater particle spread than that of the Gaussian case. This was accomplished using a space-fractional derivative that gives rise to a power-law relationship between mean squared displacement and time, and produces a stretched exponential signal decay as a function of b-value. Numerical simulations were used to estimate parameter errors under in vivo conditions, and examine the effect of limited SNR and residual fat signal. Stretched exponential DWI parameters, alpha and D, were measured in thigh muscles of 4 healthy volunteers at rest and following in-magnet exercise. These parameters were related to a stable distribution of jump-length probabilities and used to estimate microvascular volume fractions.Results Numerical simulations showed low dispersion in parameter estimates within 1.5% and 1%, and bias errors within 3% and 10%, for alpha and D, respectively. Superdiffusion was observed in resting muscle, and to a greater degree following exercise. Resting microvascular volume fraction was between 0.0067 and 0.0139 and increased between 2.2-fold and 4.7-fold following exercise.Conclusions This model captures superdiffusive molecular motions consistent with perfusion, using a parsimonious representation of the DWI signal, providing approximations of microvascular volume fraction comparable with histological estimates. This signal model demonstrates low parameter-estimation errors, and therefore holds potential for a wide range of applications in skeletal muscle and elsewhere in the body. Show less
Background and Purpose: Delayed cerebral ischemia (DCI) is a major contributor to the high morbidity in patients with aneurysmal subarachnoid hemorrhage (aSAH). Spreading depolarizations may play a... Show moreBackground and Purpose: Delayed cerebral ischemia (DCI) is a major contributor to the high morbidity in patients with aneurysmal subarachnoid hemorrhage (aSAH). Spreading depolarizations may play a role in DCI pathophysiology. Because patients with migraine are probably more susceptible to spreading depolarizations, we investigated whether patients with aneurysmal subarachnoid hemorrhage with migraine are at increased risk for DCI. Methods: We included patients with aneurysmal subarachnoid hemorrhage from 3 hospitals in the Netherlands. We assessed lifetime migraine history with a short screener. DCI was defined as neurological deterioration lasting >1 hour not attributable to other causes by diagnostic work-up. Adjustments were made for possible confounders in multivariable Cox regression analyses and adjusted hazard ratios (aHR) were calculated. We assessed the interaction effects of age and sex. Results: We included 582 patients (mean age 57 years, 71% women) mostly with mild to moderate aneurysmal subarachnoid hemorrhage of whom 108 (19%) had a history of migraine (57 with aura). Patients with migraine were not at increased risk of developing DCI compared with patients without migraine (22% versus 24%, aHR, 0.89 [95% CI, 0.56-1.43]). Additionally, no increased risk was found in patients with migraine with possible aura (aHR, 0.74 [95% CI, 0.39-1.43]), in women (aHR, 0.88 [95% CI, 0.53-1.45],P-interaction=0.859), or in young patients aged <50 years (aHR, 1.59 [95% CI, 0.72-3.49]), although numbers in these subgroups were limited. We found an interaction between migraine and age with an increased risk of DCI among young patients with migraine (P-interaction=0.075). Conclusions: Patients with migraine are in general not at increased risk of DCI. Future studies should focus in particular on young SAH patients, in whom there might be an association between migraine history and development of DCI. Show less
