Pet Scan of Alzheimers Disease

Perhaps the most important and effective use of Positron Emission Tomography (PET) technology is its use in diagnosing and treating Alzheimer’s disease. Alzheimer’s disease is a progressive, irreversible neurological disorder that is the most common of a group of disorders known as dementias. The disease attacks brain cells and causes memory loss, confusion, impaired judgment, personality changes, difficulty with reason, language problems (the loss of understanding language and creating sentences), and sometimes an inability to form new memories. A disease for which there is no cure and some confusion over how to care for it, there is an estimated 4.5 million cases of Alzheimer’s disease in the United States of America. Currently, it is estimated that half of all nursing home residents suffer from Alzheimer’s disease or a related disorder.

About Alzheimer’s Disease

Alzheimer’s Disease is the eighth leading cause of death in the United States of America and in the year 2001 was responsible for 53,852 deaths. A neurological disorder that is the most common of dementias, Alzheimer’s disease is a progressive, irreversible neurological disorder that attacks brain cells. A disease that affects approximately 4.5 million Americans, Alzheimer’s disease is a complex disease that currently has no cure and still remains a bit of a mystery to medical practitioners. Alzheimer’s disease is a severe disease that most commonly affects individuals 65 years of age or older, although it can occur in individuals in their 40’s and 50’s. A disease first described by the German physician Dr. Alois Alzheimer in 1906, Alzheimer’s disease first affects the areas of the brain responsible for memory and thinking. However, as the disease progresses it affects cells in the other regions of the brain. Eventually, Alzheimer’s patients require complete care and the loss of brain function caused by Alzheimer’s will eventually lead to death.

A long-term, incurable disease that is part of the dementia group of disorders (a catchall term used to describe diseases that cause a decline in thinking skills), Alzheimer’s disease attacks brain cells and causes memory loss, confusion, impaired judgment, personality changes, difficulty with reason, language problems (the loss of understanding language and creating sentences), and often the ability to form new memories. In its later stages, Alzheimer patients lose their ability to perform most of their normal functions and therefore require 24-hour care for feeding, personal hygiene, and bathroom needs. A disease that can last between 3 to 20 years, Alzheimer’s disease is a major concern for health care practitioners as it is believed that by the mid-twenty-first century that without a cure or more effective preventative techniques, approximately 14 million Americans will suffer from Alzheimer’s disease.

Although there are a number of different manners to distinguish between the different forms of Alzheimer’s disease, the most common grouping of Alzheimer’s are:

  • Early-onset Alzheimer’s:
    A rare form of Alzheimer’s disease that is present in less than 10% of all Alzheimer’s disease patients. This form of Alzheimer’s occurs in individuals before they reach the age of 65.
  • Late-onset Alzheimer’s:
    The most common form of Alzheimer’s disease that is also known as late-onset dementia. This form of Alzheimer’s occurs in individuals who are 65 years of age and older.
  • Familial Alzheimer’s disease (FAD):
    An extremely rare form of Alzheimer’s disease that is present in less than 1% of all Alzheimer’s disease patients. This form of Alzheimer’s is entirely hereditary and FAD patients can document members of at least two generations of having Alzheimer’s.

Regardless of the type, Alzheimer’s disease is a condition where there is little concrete information about its specifics available. Currently the cause of Alzheimer’s disease is unknown, however, there have been a number of risk factors associated with an increased susceptibility to this disease. These risk factors include:

  • Advanced age:
    Alzheimer’s disease is a condition that usually affects individuals that are 65 years and older. The risk of Alzheimer’s disease only increases with age as 1 out of every 10 individuals that are 65 years and older have Alzheimer’s disease, approximately 20% of individuals that are between 75 and 84 years of age have Alzheimer’s disease, and almost 50% of individuals who are 85 years of age and older suffer from Alzheimer’s disease.
  • Genetics:
    Recent medical studies have shown that early-onset Alzheimer’s disease is genetic in origin. Although some researchers theorize that late-onset Alzheimer’s disease is linked with a mutation on chromosome 19, this relationship is still not clear.
  • Previous Medical Conditions:
    Recent medical studies have shown that individuals with previous traumatic head injury or who have had a heart attack are more susceptible to Alzheimer’s disease development.
  • Gender:
    Statistics show that Alzheimer’s disease is more common to women than men.
Symptoms of Alzheimer’s Disease

Alzheimer’s disease is a condition in which there is little known of it. The cause of, the cure to, and preventative measures against Alzheimer’s disease are still not clear. However, it is known that early diagnosis of Alzheimer’s disease allows the Alzheimer’s patients to make full use of new drug therapies that have been developed in recent years to delay the progression of Alzheimer’s disease.

Alzheimer's disease has three major stages that can act as markers to alert friends and relatives of the onset of Alzheimer's.

The earliest symptoms are often mistaken for normal signs of aging, however Stage 1 (the earliest stage of Alzheimer's) includes the following symptoms:

  • Recent (or short term) memory loss: This can include forgetting things that occurred yesterday and having trouble remembering the names of common objects and familiar people.
  • Confused about the month or season.
  • Forgetting parts of their daily routine (e.g. brushing their teeth)
  • Walking may become harder
  • Trouble making decisions that once were easy
  • Loss of interest in pastimes

Stage 2 of Alzheimer's disease can include symptoms such as:

  • Problems accomplishing the chores of daily living
  • Personal hygiene may no longer seem important
  • Fail to recognize friends and relatives
  • May become loud, violent, and hard to control.
  • Trouble with sleeping
  • Begin wandering off.
  • May seem especially anxious, restless, and agitated in the late afternoon
  • Find it hard to recall words or talk in normal sentences

Stage 3 of Alzheimer's disease can include symptoms such as:

  • Loss of all memory and speech
  • Decline in muscular control
  • Extreme hostility
  • Loss of control
  • Aggression and destructiveness
  • Loss of all ability to care for themselves
PET and Alzheimer’s Disease Detection

One of the most effective uses of Positron Emission Tomography (PET) is in the diagnosis of Alzheimer’s disease. A progressive, irreversible neurological disorder, Alzheimer’s disease currently has no cure and is a condition that attacks brain cells. Memory loss, confusion, impaired judgment, personality changes, difficulty with reason, language problems, and the inability to form new memories are just some of the common conditions found in Alzheimer’s patients. A disease that leaves its victims unable to perform most normal functions and requiring 24-hour care, Alzheimer’s is a frightening disease.

Although there is currently no cure for Alzheimer’s disease, there are now new drug therapies that have been developed to delay the progression of Alzheimer’s disease in affected individuals. However, to make full use of these new therapies, early detection of Alzheimer’s is required.

PET scans and Alzheimer’s disease are therefore related as PET imaging has been cited as being the most accurate predictor of Alzheimer’s disease out of all of the different types of medical diagnostic imaging procedures available. A PET scan image of Alzheimers is able to show a physician the biological changes in the brain caused by Alzheimer’s disease. A recent study taken at UCLA, the California based university, have shown that PET imaging improves a doctor’s ability to forecast a patient’s future cognitive functions by up to 30%. This find relates to Alzheimer’s detection as PET imaging increases the ability of a physician to predict, in patients with early memory complaints, whether this condition will significantly worsen in the years following the initial exam.

PET scans for Alzheimer’s disease involves the administration of a radioactive tracer that is a combination of a radioisotope (a radioactive compound whose movements are detectable by a PET scanner) with a natural body compound. In Alzheimer’s diagnosis, the radioactive tracer used in the Positron Emission Tomography procedure is Fluorodeoxyglucose (FDG), which combines the natural body compound glucose with the radioisotope Fluorine-18. This radioactive tracer, or radiopharmaceutical, is used in Alzheimer’s diagnosis as the radioactive compound that it uses has a short half-life and will disappear from the body within hours. Therefore, PET scans for Alzheimer’s are safe and the patient should not have any worry about the radiation content of this procedure.

Additionally, Alzheimer’s PET scans use FDG as it contains the body compound glucose. The use of FDG, which shares a similar structure to glucose, is important, as the absorption of glucose is effective in determining the metabolic activity of the brain. In Alzheimer’s disease and other forms of dementia, the brain produces a metabolic pattern that is significantly different from the metabolic pattern of healthy brain cells. As PET imaging examines the metabolic activity of brain cells by tracing how FDG is absorbed, it is able to detect Alzheimer’s disease and other forms of dementia.

Additionally, recent studies have confirmed the effectiveness of Positron Emission Tomography in distinguishing Alzheimer’s disease from other forms of dementia. This is because Alzheimer’s disease has a metabolic abnormality (bilateral temporoparietal hypometabolism) that is significantly different from metabolic abnormalities found in other forms of dementia.

PET scan of Alzheimer’s have increased in recent years as PET imaging provides a noninvasive, painless way for physicians to confirm the presence of Alzheimer’s in patients. Traditionally, autopsy or biopsy was considered the only methods to absolutely confirm the presence of Alzheimer’s disease. With PET technology, it is now possible to identify Alzheimer’s in its early phase and subsequently use new drug therapies to delay its progression.

Recent medical studies have pointed to the possible effectiveness of using PET scanning of the hippocampus as a way to detect Alzheimer’s disease while in its early stages. It is a well-known medical fact that the hippocampus, a region of the bran that is instrumental in learning and short-term memory, is affected in the early stages of Alzheimer’s disease. It is believed that through a PET scan of hippocampus that it will be possible to see the first signs of Alzheimer’s disease long before it has spread to the cerebral cortex, which damages cognitive function and impairs the memory. Future studies on the viability of a PET scan of hippocampus have been undertaken to further the use of PET scanning for detecting Alzheimer’s disease.



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