Clearing Up Common Misconceptions About Scans

Medical Scans: Clearing Up the Most Common Misconceptions

Imaging scans can feel worrying as you fear they may reveal something serious. Find out why doctors order scans, and why it is safer than you think.

It started with a regular check-up you did not think much about. Your doctor mentioned a persistent symptom, perhaps a lingering headache or a cough. Then came the words that made your heart drop: “I’d like you to go for a scan.”

For some patients, that sentence could trigger anxiety. Is it cancer? Is it serious? Will the radiation harm me? Fear of the unknown often eclipses the relief of finding answers.

Anxiety surrounding medical imaging is common. To separate fact from fiction, we turned to Dr M Yogendra Praveen, Associate Consultant, Department of Radiology, and Mr Andrew Tan Wei, Medical Physicist, from Sengkang General Hospital (SKH) to debunk common myths about medical imaging and explain why your next scan is nothing to fear.

Why Your Doctor Orders Scans

Think of medical imaging as looking inside your house without opening the walls. If something is wrong—a leak in the ceiling, a crack in the foundation—you cannot always see it from the outside. That is exactly what scans do for your body.

Understanding Different Types of Scans

Not all scans are the same. Each type serves a specific purpose. Choosing the right one depends on what your doctor needs to see.

Radiography (X-ray): Quick and Simple

Radiography is the foundation of diagnostic imaging. X-rays are quick, widely available, and effective for examining bones and lungs. A chest X-ray takes about five minutes and exposes you to minimal ionising radiation—roughly 3 days of natural background radiation living in Singapore.

Ultrasound: Safe for Everyone

Ultrasound uses sound waves, not ionising radiation. It is completely safe for pregnant women, children, and repeated scans. The same technology is used by doctors to monitor your unborn child’s health in the womb.

Computed Tomography (CT): Detailed Cross-Sections

CT scans combine X-rays with computer processing to create detailed cross-sectional images. They are faster than MRI and excellent for detecting internal injuries, bleeding, or tumours.

While CT uses more radiation than standard X-rays, the radiation dose is tailored to each patient and kept as low as possible without compromising imaging quality.

Magnetic Resonance Imaging (MRI): Highly Detailed Images

MRI uses powerful magnets and radio waves to capture exceptional detail of soft tissues like the brain and joints, without any radiation. Scans can take up to an hour and get noisy, so earplugs are provided. However, the strong magnetic field means it may not be suitable for patients with devices like older heart pacemakers or cochlear implants.

The Radiation Question Everyone Asks

“How much radiation will I be exposed to?”

That is the most common concern Dr Praveen hears from patients.

To put this in perspective, radiation is not just found in a hospital. We are exposed to natural background radiation daily – from the sun, cosmic rays, and even foods like bananas. In Singapore, this natural exposure adds up to about 2.4 milliSieverts (mSv) per year just from living our daily lives.

With the baseline in mind, here is how radiation from common medical scans measure up:

The radiation from a diagnostic scan is carefully controlled and follows strict Singapore regulatory standards set by the Ministry of Health. Modern imaging equipment uses the lowest effective doses. Furthermore, radiographers are specially trained to minimise your radiation exposure.

Myths That Need Clearing Up

1.    Myth: "All scans expose you to harmful radiation."

Ultrasound and MRI uses no ionising radiation. Only radiography (X-ray), CT, and nuclear medicine involve ionising radiation—and even then, at very low and controlled levels.

Curious to see how these numbers stack up in real life? Watch as we break down the science:

[VIDEO 1: "Do MRIs have radiation? | SKH Health Bites]

2.    Myth: "Scans are only needed when you have symptoms."

Scans are a vital part of preventive care. Procedures like mammograms, bone density scans, and low-dose CTs for lung cancer are designed to detect diseases in their silent stages, when treatment is most effective.

3.    Myth: "The contrast dye is dangerous."

Most people tolerate contrast agents very well. If you have kidney issues or allergies, your doctor will take extra care or choose a dye-free alternative.

4.    Myth: "Radiation from scans causes cancer."

Whilst high or repeated doses of ionising radiation can increase risk of cancer over time, the amount from a single scan is extremely low. The risk of missing a serious diagnosis far exceeds the tiny radiation risk.

What Happens During Common Scans

For an X-ray:
Depending on the area being scanned, you might be asked to stand, sit, or lie down. You might also be asked to briefly hold your breath. It takes just 5 minutes, and you can go about your day immediately afterwards.

For an ultrasound:
Simply relax on a bed while a water-based gel is applied to your skin. A handheld scanner is then moved over the area being examined – it is completely painless and takes 15–30 minutes.

For a CT scan:
This involves lying on a table that moves through a large doughnut-shaped scanner. You might be asked to hold your breath for 10–15 seconds during imaging. If contrast dye is used, you may feel a warm sensation for a few seconds. Scan itself takes just 5–15 minutes.

For an MRI:
Rest on a table that slides into a tunnel-like machine. Staying still is key. Since the machine makes loud knocking sounds, earplugs are provided. Scan takes 15–60 minutes depending on the body part.

Wondering what happens from the moment you step in? We take you through the entire journey here:

[VIDEO 2: "What to expect for an MRI scan? | SKH Radiology"]

When Should You Get Scans?

Here is a key principle: don't delay scans that your doctor recommends.

The "wait and see" approach might seem reasonable for minor symptoms, but it can be dangerous for:

• Symptoms that could indicate stroke, heart problems, or internal bleeding
• Persistent pain without a clear cause
• Unexplained weight loss or fatigue
• Any symptom your doctor says requires imaging

Some conditions are time-sensitive. Early detection through scans can mean the difference between simple treatment and complex, invasive procedures later.

If your doctor suggests a scan, feel free to ask the following questions:

• What are you looking for with this scan?
• What could happen if we wait/delay?
• How urgent is this?
• What symptoms should prompt me to come back immediately?

Special Considerations for Certain Groups

Pregnant Women

Pregnancy calls for extra caution. Doctors avoid radiation scans, particularly in the first trimester when the sensitivity is highest. Safe alternatives like ultrasound or MRI are usually offered first. If a different scan is recommended, it is because they need specific information that cannot be obtained through ultrasound or MRI.

Children

Special care is taken to minimise radiation exposure in children. Hospitals strictly tailor the settings to a child’s size, using low-dose techniques to keep exposure as low as possible.

Older Adults

Many older patients worry their bodies "can’t handle" the radiation. However, diagnostic scans use very low doses. A chest X-ray gives about the same amount of radiation as 8 days of natural background radiation in Singapore.

Your age doesn't make scans more dangerous. In fact, early detection through imaging becomes more valuable as we age.

Information Equals Empowerment

Medical imaging is not something to fear; it is a vital tool that gives you answers. Delaying a scan will not make a condition disappear but detecting it early makes treatment more effective. That appointment you have been dreading could be key to staying healthy.

The next time a scan is suggested, remember: it is not a sign that something is seriously wrong. It is a sign that your doctor is being thorough.