Several molecular subtypes of sporadic Creutzfeldt–Jakob disease have been identified and electroencephalogram and cerebrospinal fluid biomarkers have been reported to support clinical diagnosis but with variable utility according to subtype. In recent years, a series of publications have demonstrated a potentially important role for magnetic resonance imaging in the pre-mortem diagnosis of sporadic Creutzfeldt–Jakob disease. Magnetic resonance imaging signal alterations correlate with distinct sporadic Creutzfeldt–Jakob disease molecular subtypes and thus might contribute to the earlier identification of the whole spectrum of sporadic Creutzfeldt–Jakob disease cases. This multi-centre international study aimed to provide a rationale for the amendment of the clinical diagnostic criteria for sporadic Creutzfeldt–Jakob disease. Patients with sporadic Creutzfeldt–Jakob disease and fluid attenuated inversion recovery or diffusion-weight imaging were recruited from 12 countries. Patients referred as ‘suspected sporadic Creutzfeldt–Jakob disease’ but with an alternative diagnosis after thorough follow up, were analysed as controls. All magnetic resonance imaging scans were assessed for signal changes according to a standard protocol encompassing seven cortical regions, basal ganglia, thalamus and cerebellum. Magnetic resonance imaging scans were evaluated in 436 sporadic Creutzfeldt–Jakob disease patients and 141 controls. The pattern of high signal intensity with the best sensitivity and specificity in the differential diagnosis of sporadic Creutzfeldt–Jakob disease was identified. The optimum diagnostic accuracy in the differential diagnosis of rapid progressive dementia was obtained when either at least two cortical regions (temporal, parietal or occipital) or both caudate nucleus and putamen displayed a high signal in fluid attenuated inversion recovery or diffusion-weight imaging magnetic resonance imaging. Based on our analyses, magnetic resonance imaging was positive in 83% of cases. In all definite cases, the amended criteria would cover the vast majority of suspected cases, being positive in 98%. Cerebral cortical signal increase and high signal in caudate nucleus and putamen on fluid attenuated inversion recovery or diffusion-weight imaging magnetic resonance imaging are useful in the diagnosis of sporadic Creutzfeldt–Jakob disease. We propose an amendment to the clinical diagnostic criteria for sporadic Creutzfeldt–Jakob disease to include findings from magnetic resonance imaging scans.

An empirical equation for the magnetization transfer (MT)FLASH signal is derived by analogy to dual-excitation FLASH, introducing a novel semiquantitative parameter for MT, the percentage saturation imposed by one MT pulse during TR. This parameter is obtained by a linear transformation of the inverse signal, using two reference experiments of proton density and T 1 weighting. The influence of sequence parameters on the MT saturation was studied. An 8.5-min protocol for brain imaging at 3 T was based on nonselective sagittal 3D-FLASH at 1.25 mm isotropic resolution using partial acquisition techniques (TR/TE/ ␣ ‫؍‬ 25ms/4.9ms/5°or 11ms/4.9ms/15°for the T 1 reference). A 12.8 ms Gaussian MT pulse was applied 2.2 kHz off-resonance with 540°flip angle. The MT saturation maps showed an excellent contrast in the brain due to clearly separated distributions for white and gray matter and cerebrospinal fluid. Magnetization transfer (MT) is a contrast mechanism in tissue that is based on cross-relaxation or chemical exchange between protons in bulk water and rotationally immobilized macromolecules (1,2). In clinical MRI, MT contrast is invoked by application of a T 2 -selective RF pulse applied prior to slice excitation. The "MT pulse" saturates specifically the macromolecular magnetization, and MT is then observed as a reduction in image intensity. Its normalized value, the MT ratio (MTR), is commonly taken as a measure for the strength of the MT effect, and hence interpreted as a surrogate parameter for macromolecular content or myelination. However, the MTR is not an absolute measure, but depends on the sequence parameters and is influenced by T 1 relaxation and flip angle inhomogeneities.This limitation can be overcome by quantitative Z-spectroscopy measurements to obtain parameter estimates for the binary spin-bath (BSB) model and suitable absorption line shapes (3,4). On clinical MR systems, pulsed MT is combined with spoiled gradient echo sequences (FLASH, fast low angle shot) and suitable adaptations of Henkelman's continuous wave model (5-7). Alternatively, pulsed MT experiments can be approximated by instantaneous events of saturation separating intervals free of irradiation (8). Since brain tissue is characterized by conditions of fast-exchange, this "free" evolution can be described by two exponential time courses, the common T 1 relaxation and the MT. The latter is observed as a reduction of the longitudinal magnetization of free water subsequent to the MT pulse (9). This MT-related saturation increases in time until the exchange equilibrium in the BSB model is restored.The concept of separating T 1 relaxation and MT has been previously applied to progressive partial saturation by repetitive MT pulses (10). Here, it is transferred to the MT-w(eighted) FLASH sequence. A phenomenological signal equation is derived by analogy from a FLASH experiment with two interleaved excitations and recovery times. This equation represents the effects of excitation and relaxation during TR, while any additional saturation du...

Background and Purpose-We aimed to determine the diagnostic value of perfusion computed tomography (PCT) and CT angiography (CTA) including CTA source images (CTA-SI) in comparison with perfusion-weighted magnetic resonance imaging (MRI) (PWI) and diffusion-weighted MRI (DWI) in acute stroke Ͻ6 hours. Methods-Noncontrast-enhanced CT, PCT, CTA, stroke MRI, including PWI and DWI, and MR angiography (MRA), were performed in patients with symptoms of acute stroke lasting Ͻ6 hours. We analyzed ischemic lesion volumes on patients' arrival as shown on NECT, PCT, CTA-SI, DWI, and PWI (Wilcoxon, Spearman, Bland-Altman) and compared them to the infarct extent as shown on day 5 NECT. Results-Twenty-two stroke patients underwent CT and MRI scanning within 6 hours. PCT time to peak (PCT-TTP) volumes did not differ from PWI-TTP (Pϭ0.686 for patients who did not undergo thrombolysis/Pϭ0.328 for patients who underwent thrombolysis), nor did PCT cerebral blood volume (PCT-CBV) differ from PWI-CBV (Pϭ0. Pϭ0.0047, rϭ1.0/Pϭ0.0046, rϭ0.819). Conclusions-In hyperacute stroke, the combination of PCT and CTA can render important diagnostic information regarding the infarct extent and the perfusion deficit. Lesions on PCT-TTP and PCT-CBV do not differ from lesions on PWI-TTP and PWI-CBV; lesions on CTA source images do not differ from lesions on DWI. The combination of noncontrast-enhanced CT (NECT), perfusion CT (PCT), and CT angiography (CTA) can render additional information within Ͻ15 minutes and may help in therapeutic decision-making if PWI and DWI are not available or cannot be performed on specific patients.