Amyloid PET•CT Imaging in Patients with Suspected Alzheimer's Disease

Comparison of amyloid imaging PET and glucose metabolism PET studies

Ruth Tesar

Case study data provided by Northern California PET Imaging Center, Sacramento, Calif., USA


 |  Tue Jun 18 00:00:00 CEST 2013

Case 1: History
An 82-year-old male presented with a history of cognitive symptoms, including mild loss of short-term memory associated with occasional headaches. There was no motor or attention deficit. Mini Mental State Exam (MMSE) scores were borderline abnormal. The patient came to the memory clinic because of concerns of his wife and daughter about his short-term memory loss. The patient underwent an MRI study of the brain, which demonstrated a small peri-falcine meningioma. There was no significant cortical or hippocampal atrophy. Both lateral ventricles were normal sized with mild periventricular hyperintensities related to mild small-vessel disease.

In view of the memory loss and suspicion of Alzheimer’s disease, the patient subsequently underwent an amyloid imaging PET•CT scan to evaluate presence of cerebral amyloid plaque. The study was performed on a BiographTM mCT with the industry's finest volumetric resolution* of 87 mm3. An amyloid imaging PET•CT was acquired with 10-minute single-bed position PET acquisition. The PET images were reconstructed using using the OptisoHD hi-rez 400x400 matrix in order to achieve the highest volumetric resolution.*

The patient also underwent a traditional glucose metabolic imaging PET•CT study performed on Biograph mCT using a 10-minute, single-bed position study. Reconstruction was also performed using the OptisoHD 400x400 matrix.

The amyloid PET data was further evaluated using syngo®.PET Amyloid Plaque** software to determine global and segmental cortico-cerebellar SUV ratios.

The cortico-cerebellar ratios of the six key cerebral segments are listed below:

ROIRatioMean
Frontal Lobe1.331.80
Precuneus1.351.77
Anterior Cingular Gyrus1.532.07
Posterior Cingular Gyrus1.421.92
Parietal Lobe1.271.72
Temporal Lobe1.421.92
Average1.21 

The global cortico-cerebellar ratio was 1.21, while that for the Posterior Cingulate Gyrus was 1.42. The global value (1.21) was higher than the value considered the lower limit of abnormal (1.18) as per the study of Fleisher et al1 derived from post mortem analysis of brains of patients with Alzheimer’s disease. Elevated global and segmental ratios also support the impression of increased cortical amyloid plaque deposits in this patient.
Cortico-cerebellar ratio analysis using syngo.PET Amyloid Plaque aims to support visual evaluation of amyloid PET imaging and provide additional diagnostic information.
 

Analysis
In view of the amyloid PET findings of high cortical amyloid plaque burden in a patient with cognitive symptoms including short term memory loss, the presence of Alzheimer’s disease could not be ruled out. In view of the absence of cortical and hippocampal atrophy, normal cortical glucose metabolism and high cortical amyloid levels, early Alzheimer’s disease was deemed a possibility.

Fig. 3: Amyloid and glucose metabolism PET images at the same levels show increased cortical amyloid uptake with normal cortical glucose uptake. The normal level of retention of amyloid tracer in the white matter is clearly defined as is the increased glucose metabolism uptake in the basal ganglia. CT slices at the same level shows normal ventricular size and absence of significant cortical atrophy.

Case 2: History
A 71-year-old female patient presented with progressive memory dysfunction to her neurologist. She underwent brain MRI, which demonstrated subtle hippocampal atrophy along with mild diffuse cortical atrophy. Lateral ventricles were within normal limits with small periventricular hyperdensities suggestive of mild subcortical small vessel disease.
In view of the suspicion of Alzheimer’s disease, the patient underwent an amyloid imaging PET•CT study for evaluation of the extent of cerebral amyloid plaque in order to rule out the disease.
The study was performed on a Biograph mCT with a 10-minute, single-bed position PET study following CT. The PET images were reconstructed at 400x400 matrix. The high volumetric resolution* achieved with Biograph mCT when combined with 400x400 matrix reconstruction is able to improve the physicians ability to differentiate between tracer uptake in the white matter, considered normal, and uptake in the grey matter, which can signal the presence of amyloid plaques.
The patient further underwent traditional glucose metabolism PET•CT, which was performed on Biograph mCT with similar acquisition and reconstruction parameters.
 

Analysis
Presence of a high amount of cortical amyloid plaque in this patient with neurologically documented progressive memory dysfunction was suggestive of the possibility of Alzheimer’s disease. Mild hippocampal atrophy on MRI and bilateral parietal hypometabolism seen on glucose metabolism PET provided reinforcement to the possibility of Alzheimer’s disease.

 

Reference

Fleisher et al. Arch Neurol 2011; 68(11):1404-1411

*Based on competitive information available at time of publication. Data on file.
**syngo.PET Amyloid Plaque is intended for use only with approved amyloid radiopharmaceuticals in the country of use. Users should review the drug labeling for approved uses.

The statements by Siemens customers described herein are based on results that were achieved in the customer's unique setting. Since there is no "typical" hospital and many variables exist (e.g., hospital size, case mix, level of IT adoption) there can be no guarantee that other customers will achieve the same results.