CT Scan: Complete Guide to Computed Tomography

What Is a CT Scan and How Does It Work?

A CT scan (computed tomography) is a diagnostic imaging procedure that uses rotating X-ray beams to create detailed cross-sectional images of your body. Unlike regular X-rays that produce flat images, CT creates "slices" that can be combined to form 3D views of organs, bones, blood vessels, and soft tissues.

Computed tomography, commonly known as a CT scan or CAT scan (computed axial tomography), represents one of the most significant advances in medical imaging since the discovery of X-rays. The technology was developed in the 1970s and has been continuously refined to provide increasingly detailed images with lower radiation doses. Today, CT scanning is an essential diagnostic tool used in hospitals and imaging centers worldwide to diagnose a vast range of medical conditions.

The fundamental principle behind CT scanning involves passing X-ray beams through the body from multiple angles as the scanner rotates around you. Detectors on the opposite side of the scanner measure how much radiation passes through different tissues. Dense structures like bones absorb more radiation and appear white on the images, while air-filled spaces like lungs absorb very little and appear black. Soft tissues appear in various shades of gray depending on their density.

A computer processes these measurements using sophisticated algorithms to reconstruct cross-sectional images, often called "slices." Modern CT scanners can acquire hundreds of slices in just seconds, and these can be combined to create detailed three-dimensional reconstructions of virtually any body structure. This capability makes CT invaluable for surgical planning, trauma assessment, and detecting abnormalities that might be invisible on conventional X-rays.

Different Types of CT Scans

CT scans can examine virtually any part of the body, and the specific type of scan is often named after the body region being examined. Head CT scans are commonly used to evaluate stroke, bleeding, tumors, and head injuries. Chest CT scans can detect lung cancer, pulmonary embolism, infections, and other lung diseases. Abdominal and pelvic CT scans examine organs including the liver, kidneys, pancreas, spleen, and intestines, helping diagnose conditions from appendicitis to cancer.

Specialized CT techniques include CT angiography (CTA), which uses contrast material to visualize blood vessels and detect blockages or aneurysms. CT colonography, sometimes called virtual colonoscopy, provides detailed images of the colon to screen for polyps and cancer. Cardiac CT can assess coronary artery disease and heart structure. Each application has specific protocols optimized for the diagnostic question being asked.

Why CT Instead of Other Imaging Methods?

Your doctor chooses CT scanning when it offers the best combination of image quality, speed, and diagnostic information for your specific clinical situation. CT excels at showing bone detail, detecting bleeding, and examining the lungs and abdomen. It's faster than MRI, more widely available, and can be performed on patients with certain metal implants that would prevent MRI scanning.

However, CT does involve ionizing radiation, which is why alternative imaging methods without radiation, such as ultrasound or MRI, may be preferred when they can provide equivalent diagnostic information. Your healthcare team carefully weighs the benefits of obtaining important diagnostic information against the small radiation risks, following the principle of using imaging only when medically necessary and using the lowest effective radiation dose.

How Do You Prepare for a CT Scan?

CT scan preparation varies by examination type but commonly includes removing metal objects and jewelry, potentially fasting for 4-6 hours if contrast is used, staying hydrated, and informing staff about allergies, kidney problems, diabetes medications, or pregnancy. You'll receive specific instructions from your imaging center before your appointment.

Proper preparation for your CT scan helps ensure the highest quality images and the safest possible examination. The preparation requirements depend on which part of your body is being scanned and whether contrast material will be used. Your healthcare provider or the imaging facility will give you specific instructions tailored to your examination, but understanding the general principles can help you prepare effectively.

One of the most important preparation steps is removing all metal objects before the scan. This includes jewelry such as necklaces, earrings, rings, and watches, as well as body piercings, metal hair clips, belts with metal buckles, and clothing with metal buttons or zippers. Metal can create artifacts on the images that obscure important details and may require the scan to be repeated. Some facilities provide secure storage for valuables, while others recommend leaving jewelry at home.

Depending on which body area is being examined, you may need to change into a hospital gown. For head scans, you typically can remain in your own clothing as long as there's no metal. For chest, abdominal, or pelvic scans, you'll usually need to remove at least some clothing. Underwire bras should always be removed for chest scans. Being prepared to change and wearing comfortable, loose-fitting clothing without metal fasteners can make the process smoother.

When Contrast Material Is Used

Many CT scans require contrast material to enhance the visibility of certain structures. If your scan involves intravenous (IV) contrast, you'll typically need to fast for 4-6 hours beforehand, though you can usually drink clear fluids. Staying well-hydrated is actually important because it helps your kidneys process the contrast material after the scan. Some facilities may ask you to increase your fluid intake in the days before the exam.

Before receiving contrast, you'll be asked about allergies, particularly any previous reactions to contrast dyes or iodine. You'll also be asked about kidney function, as contrast material is processed by the kidneys. If you have known kidney disease or are at risk for kidney problems, blood tests to check kidney function may be required before contrast is given. Certain diabetes medications, particularly metformin, may need to be temporarily stopped before and after contrast administration, as your doctor will advise.

Informing Your Healthcare Team

Open communication with your healthcare team is essential for a safe and effective CT examination. Always inform the staff if you are pregnant or think you might be pregnant, as X-ray radiation can potentially affect a developing fetus. Women of childbearing age may be asked to confirm they are not pregnant or to take a pregnancy test before certain scans.

Tell the staff about any medications you're taking, previous allergic reactions to contrast material or iodine, current or recent illnesses, and any medical conditions such as heart disease, asthma, diabetes, kidney disease, or thyroid problems. This information helps the team adjust the examination or take precautions as needed. If you experience claustrophobia or anxiety about medical procedures, discuss this in advance so accommodations can be made.

How Are Children Prepared for CT Scans?

Children undergoing CT scans benefit from age-appropriate preparation including explaining the procedure using simple terms, visiting the facility beforehand if possible, bringing comfort items, and sometimes using sedation for young children or those who have difficulty staying still. Pediatric protocols use specially adjusted, lower radiation doses.

Preparing children for CT scans requires additional consideration and planning to help ensure a successful examination. Children may feel anxious about unfamiliar medical environments, large equipment, and being separated from parents. Taking time to prepare your child can significantly reduce anxiety and improve cooperation, potentially avoiding the need for sedation and repeat scans.

Age-appropriate explanations help children understand what to expect. For young children, you might describe the CT scanner as a "big donut-shaped camera" or use picture books about medical imaging. Explain that the machine doesn't touch them and that they'll hear some humming sounds. Emphasize that the procedure doesn't hurt and that you'll be nearby the whole time. For older children and teenagers, more detailed explanations including the reasons for the scan can help them feel more in control.

Many imaging facilities offer child life specialists who are trained to help children cope with medical procedures. Some allow families to visit the facility before the scan appointment so children can see the equipment and meet the staff in a low-pressure situation. Bringing a favorite toy, blanket, or stuffed animal can provide comfort, though items with metal components should be avoided. Some facilities have child-friendly decor or allow children to watch videos during the scan.

Sedation for Children

Young children, particularly those under 5-6 years old, may have difficulty lying completely still for the duration of the scan. Movement during scanning creates blurry images that may be uninterpretable. For children who cannot remain still or who experience significant anxiety, sedation may be recommended. This typically involves mild oral sedation or, in some cases, IV sedation administered by an anesthesiologist.

If sedation is planned, your child will need to fast for a specified period beforehand, typically 4-8 hours for solid food. After sedation, children need to be monitored until they're fully awake, and you should plan for your child to take it easy for the rest of the day. An adult will need to accompany your child home, and driving should be avoided until sedation effects have completely worn off. Your healthcare team will provide specific instructions based on the type of sedation used.

What Happens During a CT Scan?

During a CT scan, you lie on a motorized table that slides through a large, donut-shaped opening in the scanner. The X-ray tube rotates around you while detectors capture images. Each scan takes about 10 seconds, during which you must lie completely still and may need to hold your breath. A technologist monitors you and communicates through a microphone throughout the procedure.

Understanding what happens during a CT scan can help alleviate anxiety and ensure you're prepared for the experience. The CT scanner looks like a large machine with a circular opening in the middle, often described as resembling a giant donut. Unlike MRI machines, CT scanner openings are relatively wide and short, which most people find less confining. The scanner room is typically kept cool to maintain the equipment, so you may want to mention if you feel cold.

When you arrive for your appointment, you'll check in and complete any necessary paperwork. If contrast material is needed, an IV line may be placed in your arm or hand. You'll then be positioned on the CT table, which is a narrow, padded bed that moves in and out of the scanner opening. Depending on the body area being examined, you'll typically lie on your back with your arms positioned either alongside your body or above your head. Cushions or straps may be used to help you maintain the correct position.

The technologist operating the scanner sits in an adjacent control room with a window looking into the scan room. You'll be able to communicate with them through an intercom system throughout the procedure. Many patients find it reassuring to know they can speak to the technologist at any time and that they're being constantly monitored. The technologist will tell you when scanning is about to begin and give you any necessary instructions.

The Scanning Process

Once you're properly positioned, the table will slowly slide into the scanner opening. The X-ray tube and detectors rotate around you, and you may hear a soft humming or whirring sound during this process. The scanner doesn't touch you at any point. Each individual scan typically takes about 10 seconds, during which you must lie completely still to prevent image blurring. Movement, even slight breathing motion, can create artifacts that obscure important details.

For most CT scans, you'll be asked to hold your breath briefly during image acquisition. This is particularly important for chest and abdominal scans where breathing motion can affect image quality. The technologist will tell you when to take a breath and hold it, typically for 10-20 seconds, and when you can breathe normally again. Some scanners have an automated voice that gives these instructions. If you have difficulty holding your breath, inform the staff before the scan begins so they can adjust the protocol if possible.

If contrast material is being given intravenously, you may notice some effects as it's injected. Many people experience a warm sensation that spreads through the body, sometimes described as feeling like warmth or mild flushing. You may also notice a metallic taste in your mouth or a sensation of needing to urinate. These effects are normal and temporary, typically lasting only a minute or two. The contrast allows blood vessels and certain organs to show up more clearly on the images.

Specific Examination Protocols

Some CT examinations have specific requirements beyond the standard procedure. For CT scans of the colon (CT colonography), the colon needs to be inflated with air or carbon dioxide to provide clear images. This is done by inserting a small, flexible tube into the rectum through which gas is gently introduced. The gas slowly distends the colon, which may cause some cramping similar to gas pain. This discomfort is temporary and the gas passes naturally within 5-10 minutes after the procedure.

For small bowel CT examinations, you may need to drink a contrast solution before the scan. This oral contrast takes time to travel through the digestive system, so there may be a waiting period of 15 minutes to 4 hours between drinking the contrast and having the scan, depending on which portion of the intestines needs to be visualized. The contrast solution may have a slightly unpleasant taste, but it's generally well-tolerated.

How Long Does a CT Scan Take?

The actual CT scan typically takes 5-20 minutes in the scanner, while the complete appointment including preparation can range from 10 to 90 minutes. Factors affecting duration include the body area being scanned, whether contrast is needed and how it's administered, and whether multiple scan series are required.

One of the advantages of CT scanning compared to other imaging modalities like MRI is its speed. The time you spend in the actual scanner is relatively brief, though the total appointment time may be longer depending on preparation requirements. Understanding the timeline helps you plan your day and reduces anxiety about how long you'll need to be at the imaging facility.

For straightforward scans without contrast, such as a head CT for headache evaluation or a chest CT without contrast, you might be in and out of the facility in 15-30 minutes. These quick scans are one reason CT is often the imaging method of choice in emergency situations where rapid diagnosis is critical. A trauma CT that examines the head, chest, abdomen, and pelvis can be completed in just minutes, providing crucial information to guide emergency treatment.

When contrast material is required, the appointment takes longer. If you need IV contrast only, the additional time is modest, mainly for placing the IV line and performing both pre-contrast and post-contrast scan sequences. If you need to drink oral contrast, there may be a substantial waiting period of up to several hours for the contrast to reach the portion of the digestive system being examined. The imaging facility will inform you of expected timing when you schedule the appointment.

After the Scan

Once the scan is complete, you can usually leave immediately and resume normal activities. There are typically no lingering effects from the CT scan itself. If you received IV contrast, you'll be encouraged to drink plenty of fluids over the next 24 hours to help your kidneys flush the contrast from your system. Most imaging facilities will ask you to wait briefly after contrast injection to ensure you don't have any immediate adverse reactions.

If you received sedation, you'll need to remain at the facility until you're sufficiently awake, which may take 30-60 minutes or longer. You should not drive, operate machinery, or make important decisions for the rest of the day after sedation. Arrange for someone to drive you home and stay with you. Similarly, if you received medications that affect your eyes (such as dilating drops for an orbital CT), you should not drive until your vision returns to normal.

Is CT Scan Radiation Safe?

CT scans use ionizing radiation, but modern scanners employ the lowest effective dose while maintaining diagnostic image quality. The radiation exposure from a typical CT scan equals 1-10 years of natural background radiation depending on the scan type. The diagnostic benefits of medically necessary CT scans typically far outweigh the small radiation risks.

Understanding radiation safety is important for making informed decisions about CT imaging. CT scans do use X-ray radiation, which is a form of ionizing radiation that can potentially cause cellular damage. However, the relationship between radiation dose and health risk is well-studied, and the medical imaging community has developed extensive guidelines to minimize radiation exposure while maintaining diagnostic image quality.

The radiation dose from a CT scan varies considerably depending on the body part examined and the specific protocol used. A head CT delivers a relatively low dose, while a full abdominal-pelvic CT delivers a higher dose because more tissue is being examined. To put these doses in perspective, they can be compared to natural background radiation that everyone receives from cosmic rays and radioactive materials in the environment. A head CT equals approximately 8 months of background radiation, while an abdominal CT equals about 3-5 years.

Modern CT technology has made significant advances in reducing radiation dose while maintaining image quality. Techniques such as automatic exposure control, iterative reconstruction algorithms, and low-dose protocols can reduce radiation by 50% or more compared to older techniques. Radiologists and technologists follow the ALARA principle (As Low As Reasonably Achievable), meaning they use the minimum radiation dose necessary to answer the clinical question.

Weighing Benefits and Risks

The decision to perform a CT scan always involves weighing the diagnostic benefits against the potential risks. For most medically indicated CT examinations, the benefits of accurate diagnosis substantially outweigh the small theoretical radiation risks. A CT scan that detects an early-stage cancer, identifies the cause of acute abdominal pain, or diagnoses a stroke allows for timely treatment that can be lifesaving.

Your healthcare team considers several factors when deciding whether CT is appropriate: the clinical question that needs to be answered, whether alternative imaging methods without radiation could provide equivalent information, the urgency of the diagnosis, and your individual factors such as age and previous radiation exposure. CT scans are not performed casually, these decisions involve careful clinical judgment by physicians trained in appropriate imaging use.

Special consideration is given to children and pregnant women. Children are more sensitive to radiation effects and have longer remaining lifetimes for potential effects to manifest. Pediatric CT protocols use substantially lower radiation doses adjusted for child size. For pregnant women, CT is generally avoided unless absolutely necessary, and alternative imaging methods are preferred when possible. However, if a CT scan is medically necessary, such as for evaluating a life-threatening condition in a pregnant woman, it can be performed with appropriate precautions.

What Is Contrast Material and Why Is It Used?

Contrast material (contrast dye) is a substance containing iodine that enhances the visibility of blood vessels, organs, and abnormalities on CT images. It can be given orally, intravenously, or as an enema depending on the examination. Common side effects include temporary warmth and metallic taste; serious allergic reactions are rare but possible.

Contrast material, also called contrast dye or contrast agent, is one of the most valuable tools in CT imaging. While CT can produce excellent images without contrast, adding contrast material often provides crucial additional information by highlighting structures and abnormalities that might otherwise be difficult to see. Understanding how contrast works and what to expect can help you feel more comfortable if your scan requires it.

The most common CT contrast materials contain iodine, which absorbs X-rays much more effectively than body tissues. When iodine-based contrast circulates through blood vessels or accumulates in certain organs, these structures become much brighter on the CT images. This enhanced visibility helps radiologists detect tumors, which often have abnormal blood supply patterns; identify blood clots in vessels; assess organ function; and characterize abnormalities more precisely than would be possible without contrast.

The route of contrast administration depends on which body structures need to be visualized. Intravenous (IV) contrast is injected into a vein, typically in the arm, and quickly circulates throughout the body. It's used for most body CT scans when contrast is needed. Oral contrast is drunk and travels through the digestive tract, making the stomach and intestines more visible. It's commonly used for abdominal CT examinations. Rectal contrast (given as an enema) may be used for specific examinations of the colon.

What Contrast Feels Like

When IV contrast is injected, most people notice distinct sensations. A warm feeling often spreads through the body, sometimes quite intensely. This warmth typically starts in the arm where the injection is given and spreads to the chest, abdomen, and throughout the body over several seconds. Many people also notice a metallic or salty taste in their mouth. Some people feel as though they're urinating, though this is just a sensation; actual urination doesn't occur. All these effects are normal and usually fade within a minute or two.

The injection itself may cause brief discomfort similar to having blood drawn. The contrast is typically injected relatively quickly using a power injector, which may create a cool or pressure sensation as the fluid enters the vein. If you notice pain, burning, or swelling at the injection site during the injection, tell the technologist immediately, as this could indicate that contrast is leaking out of the vein into surrounding tissue.

Contrast Reactions and Safety

Most people tolerate contrast material without any problems beyond the temporary sensations described above. However, allergic-type reactions can occur, ranging from mild to severe. Mild reactions include hives, itching, or nausea and typically resolve without treatment or with simple antihistamines. Moderate reactions may include more extensive hives, facial swelling, or wheezing and usually respond well to prompt treatment.

Severe allergic reactions (anaphylaxis) are rare, occurring in approximately 1 in 10,000 to 1 in 50,000 contrast administrations, but can be life-threatening. Symptoms may include difficulty breathing, significant drop in blood pressure, and loss of consciousness. Imaging facilities are equipped and staff are trained to recognize and treat severe reactions immediately. If you have had a previous reaction to contrast material, inform your healthcare team, as premedication with steroids and antihistamines can reduce the risk of repeat reactions.

Contrast material is processed by the kidneys and excreted in urine. In people with normal kidney function, this happens without problems. However, in people with pre-existing kidney disease, contrast can potentially cause temporary or permanent worsening of kidney function. This is why kidney function is checked before giving contrast to at-risk individuals, and why adequate hydration before and after the scan is important. In most cases, even with reduced kidney function, the diagnostic benefits of contrast-enhanced CT outweigh the risks when the scan is medically necessary.

When Will I Get My CT Scan Results?

CT scan results are typically available within 1-2 weeks after the examination. A radiologist analyzes the images and sends a report to your referring doctor, who will discuss the results with you. In emergency situations, preliminary results may be available within hours. You can receive results through a follow-up appointment, phone call, patient portal, or letter.

After your CT scan is complete, the images are sent to a radiologist, a physician who specializes in interpreting medical images. The radiologist carefully reviews all the images, often hundreds of individual slices, comparing findings to your clinical history and any previous imaging studies. This analysis requires expertise and cannot be rushed, which is why results aren't typically available immediately except in emergency situations.

The radiologist documents their findings in a formal report that is sent to the physician who ordered your CT scan. This report describes what was seen on the images, interprets the significance of the findings, and often includes recommendations for further evaluation or follow-up imaging if needed. Your ordering physician reviews this report and integrates it with your overall clinical picture to determine what the findings mean for your care.

You'll typically receive your results from the physician who ordered the scan, not directly from the radiologist or imaging facility. This is because your physician can explain the findings in the context of your overall health situation and discuss what the results mean for your treatment plan. Results may be communicated through various channels: a scheduled follow-up appointment, a phone call, an electronic patient portal message, or sometimes a letter.

Understanding Turnaround Times

Routine outpatient CT scans typically have results available within a few days to two weeks. The exact timing depends on factors including the imaging facility's workload, the complexity of the examination, whether comparison with previous imaging is needed, and the practices of your referring physician's office. If you haven't heard about your results within the expected timeframe, it's appropriate to contact your doctor's office to follow up.

In emergency or urgent situations, CT results are prioritized. Emergency room CT scans are often read immediately or within hours, with findings communicated directly to the treating emergency physician. Inpatient hospital CT scans similarly receive expedited interpretation. If your physician has indicated that your scan is urgent, the imaging facility can often expedite the reading.

If you have questions about your CT results or the report contains terms you don't understand, don't hesitate to ask your healthcare provider for clarification. The radiology report is a technical document written primarily for physician communication, and it's normal for patients to need explanation of the findings and their significance. Understanding your results helps you participate actively in decisions about your healthcare.

Can I Have a CT Scan If I'm Pregnant or Breastfeeding?

CT scans during pregnancy are generally avoided due to X-ray radiation exposure to the fetus, and alternative imaging methods are preferred when possible. However, if a CT scan is medically necessary for a serious condition, it can be performed with appropriate precautions. Breastfeeding does not need to be interrupted after CT scans, even with contrast material.

Pregnancy requires special consideration for any imaging study involving ionizing radiation. The developing fetus is more sensitive to radiation effects than adults, particularly during the first trimester when organs are forming. For this reason, healthcare providers carefully weigh the necessity of any CT scan during pregnancy and consider alternative imaging methods that don't use radiation.

If you are pregnant or think you might be pregnant, always inform your healthcare provider and the imaging staff before any CT scan. Many facilities have policies requiring pregnancy confirmation testing for women of childbearing age before certain CT examinations. This isn't meant to be intrusive but rather to ensure appropriate decision-making about the safest imaging approach for both you and your baby.

When CT is medically necessary during pregnancy, the examination can be performed with several modifications to minimize fetal radiation exposure. The scanning area may be limited to the essential region, avoiding the pelvis when possible. Radiation dose optimization techniques are applied. The abdomen may be shielded if it's not in the scanning area. It's important to understand that when a CT scan is truly necessary to diagnose a serious condition in a pregnant woman, such as pulmonary embolism or appendicitis, the risk of not making the diagnosis typically far exceeds the radiation risk to the fetus.

CT Scans and Breastfeeding

If you are breastfeeding, CT scans pose no concern for your baby, and you do not need to interrupt breastfeeding after a CT scan. Neither X-ray radiation nor iodinated contrast material affects breast milk in a way that could harm your nursing infant. The radiation doesn't remain in your body after the scan and cannot be passed through breast milk. Although small amounts of contrast material may be excreted in breast milk, less than 1% is absorbed by the infant's digestive tract, resulting in negligible exposure.

Despite this safety data, you may encounter conflicting advice about breastfeeding after contrast administration. Some older guidelines recommended pumping and discarding breast milk for 24 hours, but this is no longer considered necessary based on current evidence. Major medical organizations including the American College of Radiology state that breastfeeding can continue normally after receiving iodinated contrast material. If you have concerns or receive conflicting advice, discuss this with your healthcare provider.

What Is the Difference Between CT and MRI?

CT uses X-rays and excels at imaging bones, detecting bleeding, and examining the lungs and abdomen, with scans taking 5-20 minutes. MRI uses magnetic fields without radiation and provides superior soft tissue detail for the brain, spine, and joints, taking 30-60 minutes. The best choice depends on the clinical question being asked.

Patients often wonder about the differences between CT scans and MRI (magnetic resonance imaging), and which is "better." The truth is that neither is universally superior; each technology has distinct strengths that make it the preferred choice for different clinical situations. Understanding these differences helps you appreciate why your doctor chose a particular imaging method for your situation.

The fundamental difference lies in how the images are created. CT uses X-rays, a form of ionizing radiation, to generate images. MRI uses powerful magnetic fields and radio waves, without any ionizing radiation. This distinction makes MRI preferable when equivalent diagnostic information can be obtained, particularly for patients who need repeated imaging or for children. However, CT's faster acquisition speed and superior bone imaging make it the better choice in many situations.

CT excels at imaging dense structures and is the preferred method for evaluating bones and detecting fractures, for identifying acute bleeding in the brain or elsewhere, for examining the lungs and detecting conditions like pneumonia or lung cancer, and for many abdominal conditions. CT is also much faster than MRI, making it essential for emergency situations where rapid diagnosis is needed. Patients with certain metal implants that cannot undergo MRI safely may have CT as their only cross-sectional imaging option.

When MRI Is Preferred

MRI provides superior soft tissue contrast, making it the preferred choice for examining the brain for many conditions including tumors and multiple sclerosis, for evaluating the spinal cord and detecting herniated discs or spinal tumors, for assessing joints including the knee, shoulder, and hip, and for imaging the heart in certain situations. MRI can often distinguish between different types of soft tissue abnormalities more precisely than CT.

MRI has limitations that make CT preferable in some situations. MRI takes significantly longer, typically 30-60 minutes compared to 5-20 minutes for CT. The MRI scanner requires patients to lie in a more confined tube-shaped space, which can cause claustrophobia. The strong magnetic field means patients with certain implants (pacemakers, cochlear implants, some older aneurysm clips) cannot undergo MRI. MRI is also more sensitive to patient movement, making it difficult for patients who cannot lie still.

Cost and availability also factor into imaging decisions. CT scanners are more widely available and the examinations typically cost less than MRI. In situations where both CT and MRI could provide needed information, these practical considerations may influence the choice. Your healthcare team considers all these factors when recommending the most appropriate imaging study for your situation.