Vizamyl Dosage

Negative VIZAMYL Scan

Negative scans show more signal in white matter than in gray matter, creating clear gray-white matter contrast.

Specifically, a negative scan would have the following characteristics:

frontal, lateral temporal, and inferolateral parietal lobes: gradual gradient from bright intensity of the white matter to lower intensity at the periphery of the brain; distinct sulci with concave surfaces (white matter sulcal pattern),

and

posterior cingulate and precuneus: gray matter uptake below 50% to 60% of peak intensity; gap of lower intensity separates two hemispheres on coronal view,

and

striatum: approximately 50% of peak intensity or lower in the region between the higher intensities of the thalamus and frontal white matter (striatal "gap").

A negative scan indicates sparse to no neuritic plaques. In patients being evaluated for AD and other causes of cognitive decline who have not been treated with amyloid beta-directed therapy, a negative scan is inconsistent with a neuropathological diagnosis of AD at the time of image acquisition and reduces the likelihood that a patient's cognitive impairment is due to AD. A negative scan result does not preclude the accumulation of amyloid beta in the brain in the future.

Positive VIZAMYL Scan

Positive scans show at least one cortical region with reduction or loss of the normally distinct gray-white matter contrast. These scans have one or more regions with increased cortical gray matter signal (above 50% to 60% peak intensity) and/or reduced (or absent) gray-white matter contrast (white matter sulcal pattern is less distinct). A positive scan may have one or more regions in which gray matter signal is as intense or exceeds the intensity in adjacent white matter.

Specifically, a positive scan would have the following characteristics:

frontal, lateral temporal, or inferolateral parietal lobes: high intensity seen to the periphery of the brain, with sharp reduction of intensity at the brain margin; sulci may not be distinct due to fill-in by high intensity gray matter resulting in a convex appearance of the surface at the edge of the brain,

or

posterior cingulate and precuneus: gray matter uptake above 50% to 60% of peak intensity; high gray matter intensity that closes the gap between the two hemispheres on coronal view,

or

striatum: intensity above 50% to 60% of peak intensity; gap between thalamus and frontal white matter not distinct.

If any one of the brain regions systematically reviewed for signal intensity is positive in either hemisphere, then the scan is considered positive. Otherwise, the scan is considered negative.

A positive scan establishes the presence of moderate to frequent neuritic plaques. Neuropathological examination has shown that moderate to frequent amyloid beta neuritic plaques are present in patients with AD, but may also be present in patients with other types of neurologic conditions as well as older people with normal cognition.

Figures 1, 2, and 3 provide examples of negative and positive scans.

Figure 1: Axial View of Negative (left) and Positive (right) VIZAMYL Scans. The axial slices that cut through the frontal pole and inferior aspect of the splenium are shown using a rainbow color scale. The left image shows a white matter sulcal pattern at the frontal (f) and lateral temporal (lt) regions with a color intensity that tapers to the periphery, as well as less signal intensity in the striatal region(s). The right image shows absence of the white matter sulcal pattern with intensity radiating to a sharply defined convex edge, as well as more signal intensity in the striatum. In both the frontal and lateral temporal regions, the intensity is higher in the gray matter regions of the right image compared to those of the left image.

Figure 2: Sagittal View of Negative (left) and Positive (right) VIZAMYL Scans. The sagittal slices are slightly off midline in one hemisphere and shown using a rainbow color scale. In the posterior cingulate (pc) region, which is superior and posterior to the corpus callosum (cc), the left image shows signal intensity below 50% of peak intensity whereas the right image shows intensity above 60% of peak intensity. The pons (p) is set to approximately 90% of the maximum intensity.

Figure 3: Coronal View of Negative (left) and Positive (right) VIZAMYL Scans. The coronal slices are located posterior to the corpus callosum. The left image shows a white matter sulcal pattern in the inferior parietal (ip) regions that is not evident in the right image. Relative to the left image, the right image shows increased signal intensity in the posterior cinguli (pc) and increased radial extent of high intensity to the lateral surfaces of the parietal lobes particularly evident in the inferior parietal regions.