A Simple Method for 2-D In Vivo Dosimetry by Portal Imaging.

Purpose: To improve patient safety and treatment quality, verification of dose delivery in radiotherapy is desirable. We present a simple, easy-to-implement, open-source method for planar dosimetry of conformal radiotherapy by electronic portal imaging device (EPID).

Methods: Correlation ratios, which relate dose in the mid-depth of slab phantoms to transit EPID signal, were determined for multiple phantom thicknesses and field sizes.

Portal Imaging Dosimetry Identifies Delivery Errors in Rectal Cancer Radiotherapy on the Belly Board Device.

Purpose: We recently developed a novel, open-source dosimetry that uses the electronic portal imaging device to detect dose delivery discrepancies. We applied our method on patients with rectal cancer treated on a belly board device.

Methods: dosimetry was performed on 10 patients with rectal cancer treated prone on the belly board with a 4-field box arrangement.

Identification of neurovascular changes associated with cerebral amyloid angiopathy from subject-specific hemodynamic response functions.

Cerebral amyloid angiopathy (CAA) is a small-vessel disease preferentially affecting posterior brain regions. Recent evidence has demonstrated the efficacy of functional MRI in detecting CAA-related neurovascular injury, however, it is unknown whether such perturbations are associated with changes in the hemodynamic response function (HRF). Here we estimated HRFs from two different brain regions from block design activation data, in light of recent findings demonstrating how block designs can accurately reflect HRF parameter estimates while maximizing signal detection.

Two-dimensional in vivo dose verification using portal imaging and correlation ratios.

The electronic portal imaging device (EPID) has the potential to be used for in vivo dosimetry during radiation therapy as an additional dose delivery check. In this study we have extended a method developed by A. Piermattei and colleagues in 2006 that made use of EPID transit images (acquired during treatment) to calculate dose in the isocenter point.

Effects of aging on the association between cerebrovascular responses to visual stimulation, hypercapnia and arterial stiffness.

Aging is associated with decreased vascular compliance and diminished neurovascular- and hypercapnia-evoked cerebral blood flow (CBF) responses. However, the interplay between arterial stiffness and reduced CBF responses is poorly understood. It was hypothesized that increased cerebral arterial stiffness is associated with reduced evoked responses to both, a flashing checkerboard visual stimulation (i.

Neurovascular decoupling is associated with severity of cerebral amyloid angiopathy.

Objectives: We used functional MRI (fMRI), transcranial Doppler ultrasound, and visual evoked potentials (VEPs) to determine the nature of blood flow responses to functional brain activity and carbon dioxide (CO2) inhalation in patients with cerebral amyloid angiopathy (CAA), and their association with markers of CAA severity.

Methods: In a cross-sectional prospective cohort study, fMRI, transcranial Doppler ultrasound CO2 reactivity, and VEP data were compared between 18 patients with probable CAA (by Boston criteria) and 18 healthy controls, matched by sex and age. Functional MRI consisted of a visual task (viewing an alternating checkerboard pattern) and a motor task (tapping the fingers of the dominant hand).

Metabolic correlatives of brain activity in a FOS epilepsy patient.

The correlation and the interactions between neuronal activity and underlying metabolic dynamics are still a matter of debate, especially in pathological conditions. This study reports findings obtained on a subject suffering from fixation-off sensitivity (FOS) epilepsy, exploited as a model system of triggerable anomalous electrical activity. Functional Magnetic Resonance Spectroscopy was used to investigate the metabolic response to visual spike-inducing stimuli in a single voxel placed in the temporo-occipital lobe of a FOS epilepsy patient.

Metabolic alteration transients during paroxysmal activity in an epileptic patient with fixation-off sensitivity: a case study.

The purpose of this study was to investigate short-time metabolic variations related to continuous epileptic activity elicited by fixation-off sensitivity (FOS). Time-resolved magnetic resonance spectroscopy was performed on a patient on whom previous clinical findings clearly indicated presence of FOS. The epileptic focus was localized with a simultaneous electroencephalographic and functional magnetic resonance imaging study.