Brain scans and cancer
Brain scans are essential diagnostic tools used to detect abnormalities in the brain, particularly tumors or masses associated with cancer. Two primary imaging techniques are computed tomography (CT) and magnetic resonance imaging (MRI). CT scans utilize X-rays and ionizing radiation to produce images, making them faster, more accessible, and generally less expensive compared to MRI scans, which use non-ionizing radio waves and provide superior detail, especially for soft tissue. For cancer detection, CT scans can reveal the presence of tumors, and a contrast dye may be used to enhance clarity. MRI scans, often involving the injection of gadolinium, can highlight cancer cells, facilitating more precise evaluations.
Additionally, positron emission tomography (PET) scans are employed to identify active cancer cells by tracking their energy usage, often in conjunction with CT scans for improved clarity. While both CT and MRI are valuable, the choice between them typically depends on patient factors and specific diagnostic needs. It's important for patients to prepare for these scans by following specific instructions regarding food, drink, and metal items. Although these imaging procedures are generally safe, they do carry some risks, particularly associated with radiation exposure in CT scans, making careful consideration essential, especially for pregnant women. After the scans, results are analyzed by a neuroradiologist and discussed with the patient's physician.
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Brain scans and cancer
DEFINITION: Computed tomography (CT) scan and magnetic resonance imaging (MRI) are two widely used methods of scanning the brain to distinguish normal tissue from abnormal tissue (tumors or masses). The CT scanner uses X-rays and ionizing radiation (dye) to acquire images of bone and tissue. MRI acquires images using nonionizing radio-frequency signals and is best suited for noncalcified (soft) tissue. CT and MRI scanners generate multiple two-dimensional cross-sections, or “slices,” of tissue and produce three-dimensional reconstructions. For purposes of brain tumor detection and identification, MRI is generally superior. However, CT is typically more available, faster, and much less expensive, and it may be less likely to require the person to be sedated or anesthetized. It can also be performed on people with medical implants such as cochlear implants.
If cancer is suspected, then the CT scan will provide X-ray images of the brain or other internal organs to detect masses or tumors. A dye may be injected into a vein or swallowed to help the organs or tissues appear more clearly. A computer combines the images by “stacking” them on top of each other to offer an exact three-dimensional rendering.
MRI is a procedure that uses magnets and radio waves to send a series of detailed brain images to a computer. A computer then produces cross-sectional or three-dimensional images for evaluation. A substance called gadolinium may be injected into the patient through a vein. The gadolinium collects around the cancer cells so that they show up brighter in the picture. This procedure is also called nuclear magnetic resonance imaging (NMRI).
Other imaging techniques used to detect abnormalities in the brain include positron emission tomography (PET) scans and combined PET/CT scans. Brain PET scans use radioactive sugar to locate and image cells taking up the most energy, thereby helping diagnose and monitor the progression of disease. Sometimes, PET and CT scans are combined to provide a clearer picture of where a tumor is.
Cancers diagnosed:Brain tumor, metastasized cancer
Why performed: Physicians order brain scans to offer the most precise information available about the brain. The method of scanning depends on the patient's history and examination and the physician's choice of diagnostic testing.
Patient preparation: If the brain scan involves injecting or ingesting a dye, the patient may be asked to avoid eating or drinking for several hours before the exam. All jewelry and metal items must be removed before the brain scan.
Steps of the procedure: The patient will be asked to lie down, place the head in a stabilizer, and remain very still. If contrast (dye) is required, it will be injected through the intravenous (IV) line placed by a radiology nurse or technologist before the exam. During the injection, it is normal for patients to experience a warm sensation throughout the body and a metallic taste in the mouth. Only the head will be covered by the scanner, and those who experience claustrophobia generally do not have problems with a brain scan.
After the procedure: Patients are not restricted after this procedure and may eat and drive as standard.
Risks: The MRI examination poses almost no danger to the average patient; however, if sedation is necessary, a nurse or technologist will monitor vital signs to avoid excessive sedation. The magnetic field is not harmful to the patient, but metal devices nearby can cause malfunctions in the MRI. If dye is injected, there is a rare risk of mild allergic reaction.
In a 2024 article, the National Cancer Institute advised potential recipients of CT scans of the risks, although they are small. There is a risk to an unborn fetus; therefore, CT scanning is not recommended for pregnant women. Nursing mothers must wait twenty-four hours after injecting the dye to return to nursing. There is always a slight chance of cancer from radiation exposure, but the benefit of an accurate diagnosis far outweighs the risk.
Results: A neuroradiologist will read the brain scan, and the results will be shared with the physician for discussion with the patient.
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