Name: PET scan
Creator: Dr Karen Martin
Published: 2023-02-15T08:58:27.455Z

The scanner is large and white, with a hole in the middle where the bed (and patient) passes through. You are laid on the bed for a PET scan, and the bed will move you through the scanner. The radiotracer will be injected into your arm and should not be painful. The scan usually takes up to an hour to complete, and you must lie as still as possible. 

What is the machine like?

The amount of radiation from the radioactive tracer is very small, and your body will excrete the substance over the course of a couple of hours. Still, it can give an extremely small increased risk of developing cancer in the future. It is also best avoided in pregnant people unless it is an emergency.

What about the radioactive tracer?

Chronic pain is one of the toughest conditions to live with – either it’s unrelenting and making it impossible to get normal activities done, or it can come and go unpredictably, forcing you to cancel work or social plans. 

There are no clear figures as to how common chronic pain is but it may affect as many as one in three people. It's defined as persistent or episodic pain lasting more than three months and is a complex problem that isn’t just a simple physical one because it affects our mental health as well. As our nervous system adjusts to chronic pain, sensations become heightened and more widespread, and this complexity comes from our brain processing function, where pain can start to prevent everyday activities and dominate normal life. Our world becomes smaller and with less to distract us - and living in fear of pain - our pain sensation becomes even more heightened and worse. 

Chronic pain is more likely to come about from the slow pain fibers, which are loudly telling you that there’s injury: you should rest and recover by not moving much. This is opposed to the fast pain fibers that let you know your toe has been stubbed and makes you move away from the external threat (with much hopping and howling). But resting for months on end is not likely to serve any useful purpose, and often sets up new problems, both mentally and physically. 

We also now know there are two forms of chronic pain called primary chronic pain and secondary chronic pain. Chronic primary pain may affect around 1-6% of the population, and refers to the pain felt in conditions such as fibromyalgia, complex regional pain and chronic primary headache. Chronic secondary pain is more common and refers to pain from conditions such as low back pain, joint pain and shingles pain. 

An X-ray is a type of scan that uses very small amounts of radiation to create a 2D black and white image of the inside of your body. X-rays send small amounts of radiation energy through the body and detect the amount that has passed through to the other side. 

Different tissues block or absorb different amounts of the X-rays depending on how dense they are. The denser the matter, the more radiation it will block and the lighter it will appear. For example, bone shows up as white as it blocks a large amount of the radiation, whereas air in the lungs allows more to pass through and shows up as much darker.

A memory test gives a snapshot of different aspects of how you process and remember things.

There are different types of memory – think of recalling what you watched on TV last night (short-term memory) to reminiscing about a childhood holiday (long-term memory), or adding up your share of a restaurant bill (working memory). The memory test may assess other thinking or cognitive skills, such as abstract representation using shapes, language and communication skills, your concentration and attention skills, and general knowledge questions.

Some of the questions can seem quite basic or easy, and some seem confusing – just go with the flow. Great if you know the answer, and don't worry if you don't.

Cancer occurs when cells in the body multiply out of control, producing lots of abnormal cells. These abnormal cells don't function like they should and can invade tissues or organs and sometimes spread to other parts of the body. Different cancers are due to different types of cells multiplying out of control. The most common types in the US are breast, prostate, lung, and bowel cancer, but there are many other types of cancer.

Approximately 40% of people will develop cancer in their lifetime, which is a scary fact, but the treatments for cancer have improved tremendously over the years. Many cancers can be cured completely, particularly if caught early, so it's important to know about the signs to look out for and to seek medical advice early if you notice these.

Any cancer fits into four stages, depending on the tumor size, whether it has spread, and how far. These are used to guide what treatment would be best. In Stage 1, the cancer is small and has not spread anywhere. Stage 2 is when the tumor is larger but hasn't spread. In Stage 3, the cancer is larger and has spread to nearby areas. Stage 4 is when the cancer has spread to other body parts and is known as metastatic cancer.

Sarcoma is a rare cancer affecting any part of the body. The most common type are soft tissue sarcomas which develop in muscle, nerves, fatty tissue, and blood vessels. The other types are bone sarcoma and gastrointestinal stromal tumors.

**Over 10,000 people a year in the US are diagnosed with sarcoma**, making it a rare cancer that affects men and women equally.

## Types of Sarcomas

### Bone Sarcomas

Bone sarcomas are a diverse group of malignancies that originate from bone tissue, comprising several distinct subtypes with varying characteristics and treatment approaches. The main types of bone sarcomas include osteosarcoma, Ewing sarcoma, and chondrosarcoma.

**Osteosarcoma** is the most common type of primary bone cancer, typically arising in the long bones of the arms and legs. It predominantly affects children and young adults, with a peak incidence during adolescence. Osteosarcoma often presents as a painful swelling or mass near the affected bone and may be associated with pathological fractures. Diagnosis is confirmed through imaging studies, such as [X-rays](https://www.healthwords.ai/us/article/x-ray-scan!25a5be1d-b5c2-4ab2-b2a0-97d37d719aeb), [CT scans](https://www.healthwords.ai/us/article/ct-scan!5eb369a3-51a9-4240-849d-7e42ef661475), or [MRI](https://www.healthwords.ai/us/article/mri-scan!530e8c89-82b9-4792-8f71-d93dc2f4fe36), followed by biopsy for histological examination. Treatment typically involves a combination of surgery, chemotherapy, and sometimes radiation therapy, aimed at achieving local control and preventing metastases.

**Ewing sarcoma** is a rare type of bone cancer that primarily affects children and young adults. It commonly arises in the pelvis, femur, or ribs, although it can occur in any bone. Ewing sarcoma is characterized by aggressive growth and a propensity for metastases to other bones or organs. Symptoms may include pain, swelling, and occasionally, fever. Diagnosis involves imaging studies and biopsy for histological analysis. Treatment usually consists of chemotherapy, surgery, and/or radiation therapy, depending on the extent of the disease and the presence of metastases.

**Chondrosarcoma** is a malignant tumor that arises from cartilage cells within bones. It typically occurs in older adults and commonly affects the pelvis, femur, or shoulder. Chondrosarcoma is characterized by slow growth and a tendency to recur locally, although it has a lower risk of metastases than osteosarcoma and Ewing sarcoma. Diagnosis is established through imaging studies and biopsy. Treatment involves surgical resection of the tumor, with adjuvant therapy such as chemotherapy or radiation therapy in some cases.

### Soft Tissue Sarcomas

Soft tissue sarcomas are a diverse group of cancers that arise from various soft tissues in the body, including muscles, fat, nerves, blood vessels, and connective tissues. These tumors encompass a wide range of subtypes, each with unique histological, molecular, and clinical features.

**Liposarcoma** is the most common type of soft tissue sarcoma, arising from fat cells (adipocytes). It typically occurs in the extremities, retroperitoneum, or trunk. Liposarcoma is classified into several subtypes, including well-differentiated, dedifferentiated, myxoid, and pleomorphic variants, each with distinct characteristics and prognosis.

**Leiomyosarcoma** originates from smooth muscle cells and can arise in various locations, including the uterus, gastrointestinal tract, and soft tissues of the extremities. It is characterized by aggressive growth and a propensity for metastases.

**Fibrosarcoma** arises from fibroblasts, which are cells that produce collagen and other structural proteins in connective tissue. It commonly affects the extremities, trunk, or head and neck region. Fibrosarcoma is characterized by a high recurrence rate and potential for metastases.

**Synovial sarcoma** is a rare soft tissue sarcoma that typically arises near joints, especially in the extremities. Despite its name, it does not originate from synovial tissue. Synovial sarcoma is characterized by a unique chromosomal translocation and tends to affect young adults. It has a propensity for local recurrence and metastasis.

The letters MRI stand for magnetic resonance imaging and it is a way of scanning that uses a magnetic field and radio waves to create accurate images of the inside of your body. The different densities in your body show up as different shades of gray to white in the images produced. MRI is one of the safest forms of scanning and is pain-free. Unlike [X-ray](https://www.healthwords.ai/us/article/x-ray-scan!25a5be1d-b5c2-4ab2-b2a0-97d37d719aeb) and [CT scans](https://www.healthwords.ai/us/article/ct-scan!5eb369a3-51a9-4240-849d-7e42ef661475), it does not cause any radiation exposure. It can be used to look at any part of the body but is particularly useful for looking at the brain, spine, blood vessels, and heart.

CT stands for computed tomography and it is a way of scanning that uses multiple X-rays to create accurate 3D images of the inside of your body. X-rays send small amounts of radiation energy through the body and detect the amount that has passed through to the other side.

Different tissues block or absorb different amounts of the X-rays depending on how dense they are. The more dense the matter, the more radiation it will block and so the whiter it appears on the image. So, for example bone shows up as bright white as it blocks a large amount of the radiation, whereas air, in the lungs, allows more to pass through and shows up as much darker.

Every woman in the US is entitled to breast cancer screening. This starts from the age of 50, and continues up to your 74th birthday. You’ll be invited every two years, and they'll use your age and contact details from your doctor's records.

Breast cancer is the most common cancer in the US, and every 1 in 8 women is diagnosed in their lifetime. The risk grows with age, hence the screening starting at 50. It can occur in men, as they have breast tissue too, but it’s much rarer, so they are not included in the screening program.

An ultrasound scan (USS) uses sound waves to create accurate 3D images of small areas inside your body. The sound waves bounce off tissues inside your body, and how they bounce back from surfaces that are measured creates the image. The sound waves are extremely high frequency, so you cannot hear them.

Ultrasound scanning is extremely safe, pain-free, and does not use radiation (unlike [X-ray](https://www.healthwords.ai/us/article/x-ray-scan!25a5be1d-b5c2-4ab2-b2a0-97d37d719aeb), PET, and [CT scans](https://www.healthwords.ai/us/article/ct-scan!5eb369a3-51a9-4240-849d-7e42ef661475)). Ultrasound scanning can be used for looking at many areas of the body, in particular, monitoring a baby’s progression in pregnancy, looking at certain organs or lumps to help with diagnosing, and looking at muscle, joint, and tendon injuries.

A brain tumor occurs when a cluster of cells grows abnormally in the brain. These can affect you in different ways. It may not contain cancerous cells, in which case it is termed benign, but it may grow to a size that presses on important areas of the brain to cause symptoms. Alternatively, it may contain cancerous cells, in which case it disrupts the normal function of an area of the brain, even if it is a small size, and this is called a malignant tumor.   

If a benign tumor remains small and slow-growing, it may not cause any symptoms at all.  

Brain tumors can affect anyone at any age but are more common in adults than children. About 25,000 new cases of brain cancer are diagnosed in the US each year. On average, the 5-year survival rate is 32% after diagnosis.  

Dr Karen Martin

Pharmacist and Head of US Content

PET stands for positron emission tomography, a way of creating 3D images of the inside of your body and showing how well certain parts of the body are working. During the scan, a slightly radioactive substance (known as a radiotracer) is injected into your bloodstream. It can then be detected as it moves around your body and is taken up by different cells or parts of your body. It shows which cells are more active and which are less. It is usually used with CT or MRI scanning to provide detailed images.  

Your body then excretes the radiotracer over the course of a couple of hours after the scan, so it does not stay in your system. PET scanning is particularly useful for helping diagnose cancer, looking at its spread or response to treatment, and looking at conditions that affect the brain.

PET scan

What is the machine like?

What about the radioactive tracer?

Related topics

Chronic pain relief

X-ray scan

What happens in a memory test?

Cancer

Sarcoma

MRI scan

CT scan

Breast cancer screening

Ultrasound scan

Brain tumor in adults