CT scan FAQs

Can a CT scan help to diagnose chronic headaches or migraines?

A doctor may be able to make use of a CT scan to diagnose specific types of headaches and their root causes. This is very useful in formulating effective treatment measures.

If you suffer from headaches almost every day or you experienced a sudden and severe headache, a doctor may recommend a CT scan to assess what may be causing you such discomfort and pain. Migraines, however, are not likely to be diagnosed using a CT scan though.

Potential headache causes a doctor will be able to see can include:

• An abscess or infection in the brain
• Tumours in the brain
• Fluid build-up (hydrocephalus)
• Injury
• A sinus blockage
• An aneurysm (weakened artery in the brain) or bleeding in the brain

What is a CT angiogram?

A CT angiogram, or computed tomography angiogram also uses X-rays to provide detailed images of the inside of the body. This scanning test is usually recommended when it is necessary to focus on the functions of the heart, and blood vessels that link with the heart, lungs, kidneys, brain, neck, head and limbs (arms and legs).

If a doctor suspects that you may have narrowed blood vessels (stenosis) or potential blockages, such as the build-up of fatty tissue (plaque or cholesterol) or an aneurysm (bulge), this test may be strongly recommended to either rule out or diagnose a potential internal problem.

The testing process is much the same and can also include the administration of contrast material (typically through a vein in the arm or hand – IV). You may also be given a beta-blocker to slow down your heart rate if your heart and coronary arteries are the focal point of your test.

Radiologists and doctors will be on the lookout for other internal problems such as:

• Pericarditis (a build-up of fluid around the heart)
• Damage or injury to the heart valves
• Dissection (tears) in the aorta (large blood vessel carrying blood from the heart to the remainder of the body)
• Pulmonary embolism (blood clots in the lungs)
• Abnormal blood vessels patterns (this could indicate tumours in the body)
• Peripheral arterial disease (narrowing or arteries)

This scan is not as invasive as a standard angiogram which involves threading a catheter (thin tube) through an artery in your arm or leg and guiding it to your heart. A CT angiogram does not involve any tubes at all. If any abnormalities are discovered, however, more invasive testing procedures may be necessary. Your doctor will discuss any possibilities with you ahead of time to ensure you are as prepared as is necessary.

Results of the scan are usually ready within a day or two. Your doctor will contact you to discuss these in person and take any necessary next steps.

What is the difference between a CT scan and an MRI?

An MRI (magnetic resonance imaging) scan is an entirely different imaging test to a CT scan. One distinct difference is that a CT scan uses radiation and an MRI scanning procedure does not.

A CT scanner takes multiple images, recording different levels of density in tissues, organs and bones using X-ray exposure. The average scanner today uses less radiation exposure than what most airline passengers are likely to experience on long haul flights across the globe. Newer scanners have been developed to decrease the image taking time and thus considerably reduce radiation exposure risk.

MRI scanners make use of very powerful magnetic fields and radio frequency pulses instead of radiation X-rays. These magnetic fields and pulses effectively produce highly detailed and clear images as well. Internal body structures, organs and tissues are also typical areas of interest during a scan. Sometimes images are significantly clearer on an MRI image result than on a CT.

An MRI scan does take a little more time than that of a CT and a patient will likely experience a bit more noise in the scanning process.

Both tests show up the same parts of the body, using different techniques. Your doctor will make a selection based on your specific symptoms and possible diagnosis needs.

The most distinctive differences (other than radiation) between the two testing methods are:

• Uses: A CT is particularly useful for looking at bones and soft tissues. An MRI is very useful for detecting even the slightest of differences in the body’s soft tissues.
• Cost of the test: A CT scan is normally less expensive than an MRI. If you have health insurance that covers the cost of scans, it is best to double check that you are fully covered before having either test done.
• Testing time: A CT scan is typically done in a quicker period of time (sometimes within 5 minutes). The time necessary for either test does typically depend on the area/s of the body being assessed. An MRI can range from as little as 15 minutes up to 2 hours.
• Patient comfort: Scanning machines are similar for both tests, in that you will need to lay flat on a table and be moved inside a round / doughnut shaped machine. A CT scanner, is more open than that of an MRI, so any fears about being in confined spaces is less intense than if you were experiencing an MRI (which is narrower and enclosed).
• Adverse reactions: Allergic reactions are rare for both testing procedures but can happen, especially with those who have had problems with their kidneys or who are already treating conditions such as diabetes (this is related to the contrast material used). If a person is very dehydrated at the time of a scan, this could also lead to feeling unwell during and after a scan.
• Limitations: Scanners are generally set at a specific size in most hospital and clinic facilities, and this may be limiting for an obese person (more than 300 pounds or 136 kilograms). If a CT is necessary, a larger patient may be sent to a facility that is equipped with a larger scanner that can handle their weight. In the case of an MRI, a larger person may be offered an open MRI machine as an alternative (if available). Metal objects, such as those implanted in the body, or even tattoos (some tattoo inks contain iron, which conducts electricity generated during the scan and may lead to burns) can prevent any person from being able to safely have an MRI.

When it comes to making a choice as to which scan is best, doctors will consider the following:

• CT scan: Abdominal pain, particularly in emergency situations, emergency trauma (assessing blood and organ injury or bone fractures and the brain, especially when a stroke is suspected), and the chest (examining of lung tissue).
• MRI scan: The spinal cord and nerves, the brain (when assessing causes of dementia, brain cancer or tumours, neurological diseases etc.) and joints (showing up ligaments and tendons more clearly).

Both scanner types are built to help medical professionals determine a problem source and help clarify a possible solution (course of action or treatment). Many factors will play a role in the choice of scan and depends largely on the objective of the test in the first place. Your doctor will select the test that best benefits you and allows for the most accurate diagnosis to be made.