In 2010, Sood et al [3] proposed a secure dynamic identity based authentication scheme using smart cards. They claimed that their scheme is secure against various attacks. In this paper, we improve their scheme for outsider attack as well as insider attack. To remedy these security flaws, an improved scheme is proposed to withstand these attacks. [1] Introduction With the rapid increasing need ...

The impact of chronic cerebral hypoperfusion on resting-state blood oxygen level-dependent signal fluctuations remains unknown. We aimed to determine whether chronic ischemia induces changes in amplitude of low-frequency fluctuations (ALFF) and to investigate the correlation between ALFF and perfusion-weighted magnetic resonance imaging (PWI) parameters in patients with moyamoya disease (MMD). ...

Pediatric choroid plexus papillomas and carcinomas are highly vascularized neoplasms, which are difficult to distinguish with conventional imaging. We aimed to analyze the diagnostic accuracy of PWI, by using both pseudocontinuous arterial spin-labeling and DSC-PWI. We reviewed the PWI of 13 children with choroid plexus neoplasms (7 papillomas and 6 carcinomas). We quantified CBF, relative CBF,...

The aortic stiffness has been found to be a useful independent indicator of several cardiovascular diseases such as hypertension and aneurysms. Existing methods to estimate the aortic stiffness are either invasive, e.g. catheterization, or yield average global measurements which could be inaccurate, e.g., tonometry. Alternatively, the aortic pulse wave velocity (PWV) has been shown to be a reli...

The spatiotemporal evolution of stroke lesions, from acute injury to final tissue damage, is complex. Diffusion-weighted (DWI) and perfusion-weighted (PWI) imaging is commonly used to detect early ischemic changes and attempts to distinguish between permanently damaged and salvageable tissues. To date, 2D and 3D measures of diffusion/perfusion regions at individual timepoints have been widely u...

INTRODUCTION. Many approaches have been applied to evaluate brain perfusion in neonates: brain ultrasound, near-infrared spectroscopy, and positron emission tomography (PET). However perfusion weighted imaging (PWI) MRI has been shown to enable in vivo direct measurements of brain perfusion in different brain regions. Recent advances have lead to the development of non-contrast agent based Arte...

BACKGROUND AND PURPOSE In ischemic stroke, MR perfusion-weighted imaging (PWI) and diffusion-weighted imaging (DWI) mismatch represents tissue at risk for infarction. Infarct growth should only take place in the presence of mismatch, although there have been reports of this occurring. We hypothesized that this observation may be attributable to the presence of undetected "hidden mismatch," whic...

OBJECTIVE To assess the evidence for the use of diffusion-weighted imaging (DWI) and perfusion-weighted imaging (PWI) in the diagnosis of patients with acute ischemic stroke. METHODS We systematically analyzed the literature from 1966 to January 2008 to address the diagnostic and prognostic value of DWI and PWI. RESULTS AND RECOMMENDATIONS DWI is established as useful and should be consider...

BACKGROUND AND PURPOSE Emergent neurovascular imaging holds promise in identifying new and optimum target populations for thrombolysis in stroke. Recent research has focused on patients with diffusion-weighted MRI (DWI)-perfusion-weighted MRI (PWI) mismatch as a marker of tissue at risk of infarction and a means to select the most suitable candidates for thrombolysis. The present study sought t...

INTRODUCTION: Arterial Spin Labeling (ASL) uses magnetically labeled water protons as an endogenous tracer. This makes ASL difficult to apply in case of prolonged transit times from the labeling region to the image region, as often seen in stroke patients, because the label vanishes with the T1 of blood. In addition, the low signal-to-noise ratio in ASL experiments necessitates long averaging w...