What is a PET-CT scan, and When Do You Really Need One

Medical technology has made remarkable strides in recent years, transforming the way doctors diagnose and treat diseases. One such breakthrough is the PET-CT scan, which has become an essential tool in modern healthcare. In fact, studies suggest that more than 2 million PET scans are performed globally every year, helping in the early detection and monitoring of conditions ranging from cancer to neurological disorders.

With its ability to deliver detailed insights into organ function and disease progression, a PET-CT scan empowers doctors to create more precise and personalized treatment plans.

In the following sections, we’ll explore what a PET-CT scan is, how it works, how it compares to other imaging methods, and why it has become such a vital tool in healthcare today.

What is a PET-CT scan?

A Positron Emission Tomography (PET) scan is a powerful imaging test that provides detailed pictures of how your organs and tissues are working, not just how they look. Unlike standard scans that show structure, PET scans reveal the metabolic and biochemical activity inside your body.

The test involves a safe, injectable radioactive substance known as a radiotracer (or tracer). Once injected, the tracer travels through your bloodstream and collects in areas of the body with higher levels of activity. Since diseased or cancerous cells often use more energy than normal cells, they absorb larger amounts of the tracer. This highlights potential health problems, sometimes before they appear on conventional imaging like CT (Computed Tomography) or MRI (Magnetic Resonance Imaging).

Healthcare providers commonly use PET scans to:

• Diagnose and monitor cancer
• Evaluate the effectiveness of cancer treatments
• Assess certain heart conditions
• Investigate brain and neurological disorders

In many cases, PET images are combined with CT or MRI scans to provide even more precise information. A PET-CT scan merges the metabolic detail of PET with the structural clarity of CT, creating a comprehensive 3D image. This combination is especially valuable in cancer care, as it shows both the exact location and the activity level of abnormal cells.

During the procedure, the tracer is typically injected into a vein in your arm or hand. After a short waiting period, you’ll lie on a scanning table while the machine captures images. The scanning itself usually takes 30–45 minutes, though the entire process, from preparation to completion, can take around 2 hours. PET-CT scans are usually done in the radiology department as an outpatient procedure.

Because these scanners are highly specialized, they are often found in major cancer hospitals or advanced diagnostic centres, which may require some patients to travel to access the service.

With its ability to detect disease activity at the cellular level, a PET-CT scan has become an indispensable tool in early diagnosis, treatment planning, and monitoring outcomes in modern medicine.

When Might You Need a PET-CT scan?

Doctors usually recommend a PET-CT scan for conditions that need both structural and functional insight.

Cancer diagnosis and staging – To detect tumours, check if cancer has spread, or assess treatment response.

Heart disease – To evaluate blood flow and detect damaged heart tissue after a heart attack.

Neurological disorders – Helpful in diagnosing Alzheimer’s disease, epilepsy, or brain tumours.

Infections and inflammations – To identify hidden infections or inflammatory conditions.

Planning surgeries or therapies – Ensures precise targeting in radiation therapy or surgical interventions.

What’s the Difference Between a PET Scan, a CT scan, and an MRI?

Medical imaging plays a crucial role in diagnosing and monitoring diseases. While CT scans, MRI scans, and PET scans are all advanced imaging tools, each works differently and serves unique purposes in healthcare.

CT scan (Computed Tomography)

• Uses X-rays to produce detailed cross-sectional images of bones, organs, and tissues.
• Best suited for detecting bone fractures, internal bleeding, or organ damage after trauma.
• Primarily shows the structure and anatomy of the body.

MRI (Magnetic Resonance Imaging)

• Uses powerful magnets and radio waves to create highly detailed images of soft tissues.
• Commonly used to assess the brain, spinal cord, muscles, and joints.
• Focuses on identifying soft tissue injuries and abnormalities, but does not provide information about how those tissues are functioning.

PET Scan (Positron Emission Tomography)

• Uses a small amount of radioactive tracer to track how tissues and organs are working in real time.
• Detects cellular-level changes before they become visible on CT or MRI scans.
• Often combined with CT for a PET-CT scan, which produces a comprehensive 3D image that merges structure with function.

Is a PET-CT scan Safe?

Yes. The amount of radiation is carefully controlled and generally safe, even for repeated use when medically necessary. Your doctor will weigh the benefits against any potential risks before recommending it.

When Should You Consult a Doctor for a PET-CT?

You should consider consulting your doctor for a PET-CT scan if you:

• Have unexplained symptoms that standard tests cannot explain.
• Are undergoing treatment for cancer and need to monitor progress.
• Have been advised for surgery or radiation therapy where precision is critical.
• Have a neurological or cardiac condition requiring detailed assessment.

At Apex Hospitals, our advanced PET-CT technology helps doctors detect diseases early, monitor treatment accurately, and guide precise interventions. With expert radiologists, compassionate staff, and NABH-accredited facilities, we ensure world-class care.