As you may know, Magnetic Resonance Imaging (MRI) allows exquisite imaging of the brain. Advanced Neuroimaging refers to recent techniques that image beyond the anatomy of the human brain. Our Radiology Department uses some of these techniques on a regular basis to take care of our patients as well as for medical research. In this brief explanation, we will describe functional MRI and perfusion imaging.
Figure 1: Teenage patient who presented with seizures underwent a brain MRI (picture in the left) that showed a mass in the right side of the brain (inside the yellow circle) and surgical removal was recommended. A fMRI was obtained while the patient underwent several language tasks obtained to predict the outcome after surgery (left pictures). This study showed that the centers in control of the language were mostly in the left side of the brain (inside the blue circles). Therefore, the chances of having a language deficit if the mass in the right side of the brain was resected were very low. Patient and family decided to undergo resection of the mass. As predicted with the fMRI, the patient had no language deficit after the surgery.
Functional MRI (fMRI) distinguishes those parts of the brain that consume more oxygen (i.e. are more active) during a specific task, such as moving your fingers. This is useful in many ways, such as predicting the outcome in a patient who needs brain surgery. With this, we can localize the area in the brain that deals with language, movements, and sense of touch among other functions. We work with the surgical team to explain to the patient and family the potential consequences of surgery.
Figure 2: Teenage patient who had weakness and tingling of the right upper extremity underwent a brain MRI (left picture). The study showed a normal shape of the brain. However, the ASL image (right picture) showed a region in the left side of the brain (inside the yellow circle) that was darker when compared to the same region in the right side of the brain. Such finding was concerning for decreased perfusion to this region. This patient was found to have an occlusion of the left middle cerebral artery, one of the main vessels supplying oxygen and nutrients to this region of the brain.
Perfusion refers to the passage of blood through an organ. Patients with various diseases, including sickle cell anemia, may have decreased perfusion to the brain. Quantifying these changes in perfusion permits us to make the appropriate changes in management in order to avoid brain damage and improve the long-term outcome. We can assess brain perfusion using intravenous (IV) contrast and measuring how it goes into the brain through the blood vessels. This requires the use of an IV injection. Arterial spin labeling (ASL) is a technique that provides good information regarding brain perfusion without IV injection. However, it is still an evolving technique that may or may not be useful depending on each particular patient.
In summary, advanced neuroimaging permits us to look beyond the shape of the human brain. We are proud to employ such techniques in our Radiology Department and to provide the medical community with important research regarding this topic.
Contributed by Dr. Enrique Alvarado and edited by Dr. Alexander Towbin.