Although not as accurate as MRI, CT also permits detection of hippocampal atrophy in AD patients [13] but is not recommended as first-line imaging for this purpose because MRI provides higher resolution images. Contrast- enhanced CT head is not recommended because the examination is mainly used to rule out other pathologies that do not typically require contrast for detection. Similarly, dual-phase CT head is not indicated in the evaluation of AD. However, amyloid PET may be positive in cognitively normal subjects who do not develop AD and in patients with other forms of non-AD dementia [22]. Although a negative amyloid PET scan likely means a low probability of AD, the patient may still harbor a non-AD neurodegenerative condition. The Amyloid Imaging Task Force, the Society of Nuclear Medicine and Molecular Imaging, and the Alzheimer's Association has proposed guidelines for the use of amyloid PET [23,24]. The taskforce suggests that amyloid PET may be useful and appropriate in patients with a cognitive complaint and confirmed impairment when AD is in the differential but the diagnosis is uncertain after evaluation by a dementia expert and the knowledge of the presence or absence of amyloid deposition is felt to add to patient care (although currently no treatment can slow AD progression, and the presence of amyloid cannot be sufficiently predictive in many cases). The taskforce cites specific appropriate use criteria in which amyloid PET might be useful: persistent or progressive unexplained MCI, possible AD (unclear clinical presentation, atypical clinical course or etiologically mixed presentation, and Dementia A CMS-convened Medicare Evidence Development and Coverage Advisory Committee that met in 2013 concluded there was low to intermediate confidence that amyloid PET would significantly contribute to the care of these patients. However, in its national coverage decision, CMS concluded that amyloid PET would be covered under a coverage with evidence development program [25].
Dementia. Although not as accurate as MRI, CT also permits detection of hippocampal atrophy in AD patients [13] but is not recommended as first-line imaging for this purpose because MRI provides higher resolution images. Contrast- enhanced CT head is not recommended because the examination is mainly used to rule out other pathologies that do not typically require contrast for detection. Similarly, dual-phase CT head is not indicated in the evaluation of AD. However, amyloid PET may be positive in cognitively normal subjects who do not develop AD and in patients with other forms of non-AD dementia [22]. Although a negative amyloid PET scan likely means a low probability of AD, the patient may still harbor a non-AD neurodegenerative condition. The Amyloid Imaging Task Force, the Society of Nuclear Medicine and Molecular Imaging, and the Alzheimer's Association has proposed guidelines for the use of amyloid PET [23,24]. The taskforce suggests that amyloid PET may be useful and appropriate in patients with a cognitive complaint and confirmed impairment when AD is in the differential but the diagnosis is uncertain after evaluation by a dementia expert and the knowledge of the presence or absence of amyloid deposition is felt to add to patient care (although currently no treatment can slow AD progression, and the presence of amyloid cannot be sufficiently predictive in many cases). The taskforce cites specific appropriate use criteria in which amyloid PET might be useful: persistent or progressive unexplained MCI, possible AD (unclear clinical presentation, atypical clinical course or etiologically mixed presentation, and Dementia A CMS-convened Medicare Evidence Development and Coverage Advisory Committee that met in 2013 concluded there was low to intermediate confidence that amyloid PET would significantly contribute to the care of these patients. However, in its national coverage decision, CMS concluded that amyloid PET would be covered under a coverage with evidence development program [25].