Brain scanners, often called “scanner cerebral,” provide a non-invasive window into the brain’s complex structures and functions. These instruments produce detailed images, used for diagnosing and understanding a wide array of neurological conditions and diseases. By offering precise visual data, brain scanners help healthcare professionals assess brain health, monitor disease progression, and guide treatment strategies.
Common Brain Imaging Technologies
Medical imaging of the brain primarily utilizes several distinct technologies, each offering unique insights. Magnetic Resonance Imaging (MRI) employs strong magnetic fields and radio waves to generate detailed anatomical images of the brain. Computed Tomography (CT) scans utilize X-rays to create cross-sectional images of brain structures. Positron Emission Tomography (PET) scans use radioactive tracers to visualize metabolic activity within the brain.
What Brain Scanners Detect
Brain scanners identify various medical conditions and neurological disorders. They detect structural abnormalities such as brain tumors, cysts, and the effects of strokes, including areas of bleeding or infarction. Conditions like multiple sclerosis, characterized by demyelination, are also visible. Scanners further aid in diagnosing neurodegenerative diseases like Alzheimer’s disease by revealing brain atrophy or the presence of specific protein plaques.
Brain injuries from trauma, inflammation, and infections are identified, allowing for timely intervention. Beyond structural issues, functional brain activity can be observed, which is useful in understanding cognitive processes or locating the source of seizures for epilepsy surgery planning. Scanners also detect hydrocephalus and vascular abnormalities such as aneurysms or malformations.
How Brain Scanners Operate
Magnetic Resonance Imaging (MRI)
Magnetic Resonance Imaging (MRI) machines generate a magnetic field that aligns protons in water molecules within tissues. Radiofrequency currents are then pulsed through the patient, displacing these aligned protons. When the radiofrequency field is turned off, the protons relax and emit energy, which is detected by the MRI sensors. This released energy and the time it takes for protons to realign vary depending on the tissue type, allowing a computer to construct detailed images based on these magnetic properties.
Computed Tomography (CT)
Computed Tomography (CT) scans use X-rays and computer processing to create images. An X-ray tube rotates around the patient’s head, emitting a fan-shaped beam of X-rays that pass through the brain from multiple angles. Detectors on the opposite side measure the amount of X-rays absorbed by different tissues. A computer then processes this attenuation data to reconstruct detailed cross-sectional or 3D images of the brain’s internal structures.
Positron Emission Tomography (PET)
Positron Emission Tomography (PET) scans involve injecting a radiotracer into the bloodstream. This tracer travels through the blood and accumulates in areas of high metabolic activity, such as cancer cells or active brain regions. As the radiotracer decays, it emits positrons, which collide with electrons in the body, producing two gamma rays. The PET scanner detects these gamma rays, and a computer uses this information to create three-dimensional images that illustrate the tracer’s distribution and concentration, revealing metabolic and physiological processes within the brain.
Undergoing a Brain Scan
Preparing for a brain scan involves specific instructions to ensure image clarity and patient safety. Patients must remove all metal objects, including jewelry and piercings, as metal can interfere with image production, especially for MRI scans. For some scans, particularly PET scans and CT scans with contrast, a period of fasting may be required, though water intake is usually permitted. It is also important to inform staff about any medical history, including allergies, diabetes, or claustrophobia, as these factors may necessitate special considerations or pre-scan medication.
During the procedure, patients lie on a table that slides into the scanner, which can resemble a large tube or doughnut-shaped opening. Remaining still throughout the scan is important to prevent blurred images, and the duration can range from 15 minutes to over an hour depending on the type of scan. Patients may hear loud tapping, buzzing, or clicking noises, especially during an MRI, and are provided with earplugs or headphones to mitigate the sound. Communication with the technologist, who operates the machine from a separate room, is maintained via an intercom system. After the scan, patients can resume normal activities, though drinking extra fluids may be recommended to help flush any contrast agents or tracers from the body.
Safety and Important Considerations
Brain imaging procedures are considered safe, but certain precautions are observed. For MRI scans, the magnetic field necessitates the removal of all ferromagnetic metal objects, as they can become dangerous projectiles or interfere with implanted medical devices like pacemakers or aneurysm clips. While MRI does not use ionizing radiation, contrast agents are sometimes used and should be administered with caution in pregnant individuals or those with kidney issues.
CT scans involve exposure to ionizing radiation, though the dose for a single brain scan is low and the risk of long-term effects like cancer is minimal. Pregnant women are advised to avoid CT scans unless medically necessary due to potential risks to the fetus. Contrast dyes may be used with CT scans and can cause allergic reactions, so patients with known allergies or certain conditions like diabetes or kidney disease require careful monitoring.
PET scans utilize a radioactive tracer, and while the exposure is minimal and the tracers have short half-lives, pregnant or breastfeeding individuals are advised against these scans. After a PET scan, patients may be advised to limit close contact with pregnant women or young children. Across all imaging modalities, open communication with healthcare providers about medical history, implants, allergies, and pregnancy status is important to ensure patient safety and optimize the procedure.