Parkinson’s and Alzheimer’s diagnostic imaging

 

Diagnostic imaging isn’t only used to allow doctors to see the internal structures of the body. It is also increasingly being used to guide and deliver treatments to very specific parts of the body, including the brain.

X-rays, computed tomography (CT), ultrasound, magnetic resonance imaging (MRI), and positron emission tomography (PET) are all used to provide images that help locate and diagnose diseases and trauma. Different types of diagnostic imaging are used for different purposes. For example, x-rays are often used to determine whether bones are broken, while MRI is often used to detect abnormalities in the brain. Ultrasound is used in a range of procedures, from fetal imaging to measuring heart function. Various types of diagnostic imaging are helping physicians develop new methods for treating diseases of the brain, including Parkinson’s disease and Alzheimer’s disease.

Parkinson’s Disease and Alzheimer’s Disease

Parkinson’s disease is a progressive central nervous system disorder that primarily affects movement. The disease develops gradually, often starting with very minor hand tremors, and progressing to stiffness and slowed movement. It may cause speech difficulties as well, and the disease becomes more severe with time. Doctors may diagnose Parkinson’s disease by using a drug called 18F DOPA along with PET diagnostic imaging. This allows the PET images to show exactly where changes occur in a patient’s brain’s dopamine system.

Alzheimer’s disease is the most common type of dementia, and is a progressive disease that eventually leads to death. Early symptoms may appear to be nothing more than typical aging effects, like short-term memory loss. Usually diagnosed in people over age 65, Alzheimer’s disease affects around 27 million people worldwide. Diagnostic imaging using ultrasound is now being used in the treatment of Parkinson’s and Alzheimer’s because it can help drugs reach specific areas of the brain affected by these diseases.

Delivery of Drugs to the Brain

The blood brain barrier is a permeable barrier that separates the body’s general blood circulation system from the fluid surrounding the brain. The blood brain barrier allows the passage of gases, water, fat-soluble molecules, glucose and amino acids into the brain, while preventing the entry of many other substances, including neurotoxins. By allowing smaller molecules like oxygen, glucose, and hormones to pass through while keeping larger molecules out, the blood brain barrier protects the brain from many harmful substances.

Some drugs used to treat Parkinson’s disease and Alzheimer’s disease have difficulty crossing the blood brain barrier, and for this reason they may be given in high doses to patients, increasing the risk of harmful side effects. However, researchers are discovering ways to selectively open the blood brain barrier to larger molecules (including drugs), so that these drugs may be able to be given in smaller doses and more accurately pinpoint the parts of the brain that they benefit most.

Ultrasound Used to Selectively Open Blood Brain Barrier

When molecules are encased in “bubbles” coated with protein or lipid shells, ultrasound beams can be used to make the bubbles oscillate or collapse. When the microbubbles collapse, they can penetrate the blood brain barrier. Ultrasound beams can also be used to target specific regions of the brain so that medications inside microbubbles can be delivered to where they are needed most, making them more effective at lower doses and potentially decreasing harmful side effects.

Professor Elisa Konofagou of Columbia University’s Fu Foundation School of Engineering and Applied Science, along with her research team, found that ultrasound beams with different acoustic pressures could be used to help specific molecules accumulate in a region of the brain called the hippocampus. The hippocampus plays vital roles in the consolidation of information from short term to long term memory. Konofagou and her colleagues specifically found that higher acoustic pressures led to larger molecules accumulating in the hippocampus, and lower acoustic pressures led to accumulation of smaller molecules. All of this is done non-invasively, unlike current drug delivery systems for the brain, which require surgery or drilling into the brain.

Guided Ultrasound and Parkinsons’ Treatment

Focused ultrasound shows new promise for delivery of drugs to targeted areas of the brain, but it can also be used to perform ablation to specific brain structures without surgery in Parkinson’s patients. A focused ultrasound beam, guided by magnetic resonance imaging allows physicians to direct a beam of acoustic energy through the scalp, skull, and brain to destroy highly targeted tissues without damaging nearby tissues or the tissues through which the ultrasound beam passes.

Once the target area of the brain is identified, high temperatures can be delivered directly to the target area, destroying tissues responsible for many of the motor problems that Parkinson’s patients suffer. Because it’s noninvasive, risk of infection is greatly reduced, and since electrodes and needles aren’t used, collateral damage to brain tissues is minimized.

Guided Ultrasound and Alzheimer’s Treatment

Amyloid-beta is part of an amino acid that is a prime component of the amyloid “plaques” found in the brains of Alzheimer’s patients, and antibodies against amyloid-beta can be used to reduce these plaques in the brain. High doses of amyloid-beta have to be given to be sure that enough reaches the areas of the brain where it helps, but this can cause severe side effects.

However, focused ultrasound can be used to selectively open the blood brain barrier and allow the antibodies against amyloid-beta to more easily enter the brain and bind to amyloid plaques. So far, studies in humans have been limited, but the technique appears promising in reducing plaque size and plaque surface area. It could allow antibody therapy to be more effective at lower doses, providing better treatment while reducing side effects.

Conclusion

Diagnostic imaging is no longer limited to diagnostics, but is now being used to more effectively target drug delivery. When focused ultrasound is used to allow very specific molecules to cross the blood brain barrier, drugs can be given in lower doses, and MRI guidance can be used to direct drugs to the exact area of the brain where they are needed.

SteleRAD is owned, operated, and managed by board certified radiologists like Dr. Kenneth P. Morrison, a highly trained specialist in ultrasound technology. SteleRAD provides unparalleled expertise in diagnostic imaging for hospitals, imaging centers, and physician groups across a broad range of specialties. To find out more about SteleRAD’s service contact us online or call 954-358-5250.