Your oncologist wants you to go for a CT and PET scan and an abdominal ultrasound. You’ve only ever had an x-ray of your hand at age 11 when you fell off a jungle gym, so this feels quite daunting. Why do you need these tests, who interprets them and what information will they provide to your doctor? Read more to get these questions and others answered.

Cancer imaging tests allow doctors to see what is going on inside your body. These machines send different forms of energy (x-rays, sound waves, radioactive particles, or magnetic fields) through your body. Your body tissues change the energy patterns to create a picture or image. These images are then interpreted and reported on by radiologists, doctors who have specialised in imaging techniques. These reports are then sent to and examined by your treating doctor e.g. oncologist, surgeon or other specialist.

Cancer imaging tests are used by doctors to: ¹

• Screen for cancer i.e. detect early stages of cancer before symptoms appear
• Help diagnose, classify and stage cancer i.e. where is the tumour, does it look benign or malignant, has it spread and where has it spread to?
• Plan cancer treatments e.g. identify where radiation therapy beams need to be focussed
• Monitor cancer treatment - has the tumour shrunk, stayed the same or grown after treatment?
• Monitor you during remission - has the tumour come back (recurred) after treatment?

There are many different types of scans that are used in oncology medicine. The tests your doctor recommends may depend on where the tumour is, what type it is, your age, gender and overall health, your preference and affordability. This article will look at the some of the most commonly performed imaging tests.

Mammography ²

A mammogram is an x-ray examination of the breast that is used to screen for or to diagnose breast diseases such as benign tumours, cysts and breast cancer. Mammography cannot prove that an abnormal area (a mass, area of calcification or increased density) is cancer, but if it raises a significant suspicion then a tissue biopsy will be performed to confirm the diagnosis. Technical advances in mammography have greatly improved the technique and quality of the images without exposing the patient to too much radiation.

Ultrasound ³

An ultrasound machine creates images by sending sound waves through your body that bounce off organs and tissues and create echoes. The machine turns these echoes into real-time pictures on a computer screen that show organ structure and movement and even blood flow through vessels. Ultrasound has the following uses in oncology diagnostics:

• It is better at getting images of soft tissue diseases that don’t show up well on X-rays.
• It can differentiate a fluid-filled cyst from a solid tumour without exposing a person to radiation and within a short time frame.
• It can be used to guide a needle during a biopsy.
• Colour dopplers can be used to see if the cancer has spread into blood vessels, especially in the liver and pancreas.

Ultrasound images are however, not as detailed as those from CT or MRI scans and they cannot be used for lung or bone tissue imaging as the sound waves cannot pass through air.

CT (computed tomography) scan ⁴

CT scans show a slice or cross-section of the body in which the bones, organs and soft tissues are shown much more clearly than with a standard X-ray. Where X-rays use a single angle broad beam of radiation to create an image, CT scans used multiple pencil-thin beams from different angles to create a slice or even a 3-D image. CT scans can show a tumour’s shape, size, and location as well as the blood vessels supplying the tumour.

Other uses for CT scans include:

• Guided needle tissue biopsies.
• Guided needle administration for radiofrequency ablation (a cancer treatment that uses heat to destroy a tumour).
• Treatment monitoring - by comparing CT scans over time, doctors can see if a tumour is responding to treatment or if it has come back after treatment.
• Virtual endoscopy - advances in CT scan technology allow for 3-D images of the inside lining of the lungs or colon, without having to insert an endoscope (tube camera) into these areas.

MRI (magnetic resonance imaging) scan ⁵

MRIs also creates cross-section pictures of the inside of your body, but it uses strong magnets instead of radiation. This strong magnetic force and a burst of radiofrequency is used to create the images. Because of this, it is very important that you let your doctor and radiographer (person who performs the test) know if you have any metal in your body. An MRI with contrast dye is the best way to find cancers in the brain and spinal cord.

Other uses include:

• Distinguishing between benign tumours and cancer.
• Looking for cancer metastases i.e. tumour that has spread to other parts of the body.
• Helping doctors to plan for surgery or radiation therapy.

Nuclear medicine scans (bone scan, PET or PET-CT scan, thyroid scan) ⁶

Nuclear scans make pictures based on the body’s chemistry rather than on physical shapes and forms. These scans use liquid substances called radionuclides (tracers) that release low levels of radiation. Some are swallowed while others are injected into veins or inhaled as a gas. They can then take seconds to days to collect in the parts of the body that are being tested. Tissues affected by cancer cells will either absorb more or less of these radionuclides than normal tissue. Special cameras then pick up the pattern of radioactivity released from these tracers to create pictures to show where they have travelled and collected.

Tumours can show up on the pictures as either a “hot spot” (an area of increased cell activity and uptake) or a “cold spot” (an area of decreased uptake and less cell activity). Because nuclear scans don’t provide very detailed images on their own, they are often used along with other imaging tests e.g. if a bone scan shows hot spots it is usually followed by X-rays for more detail on the bone structure.

Different types of nuclear medicine scans used for cancer include:

Bone scans:  These look for cancer that may have spread to the bone from other parts of the body. They can often find bone changes much earlier than regular X-rays.

PET (positron emission tomography) and PET-CT scans: This scan makes use of a form of radioactive sugar that is taken up in large amounts by rapidly growing cancer cells. Learn more about Life Healthare's PET-CT services here.

Thyroid scans: Here, radioactive iodine that is swallowed collects in the thyroid gland and is used to find thyroid cancers. This test cannot be done if you are allergic to iodine.

Although imaging tests can be very helpful, they aren’t perfect. Sometimes they may miss cancer if it is in the very early stages (small number of cancer cells) or they can show something that looks like cancer, but further testing may prove no cancer is present. If you are going for any of the above imaging tests, download and print out Diagnostic scans: What you need to know prior to your appointment to help you get ready. If you have any further questions or concerns about an imaging test speak to your doctor or the radiographer prior to having the examination.

About Life Oncology 

Life Oncology is a dedicated oncology and radiotherapy service under the Life Healthcare network. Our prime objective is to revolutionise the cancer treatment journey by embracing a patient-centric and value-based model, supporting our patients and their families throughout their treatment journeys. To support this journey, we ensure that our care is coordinated, integrated, and personalised.

Check the download section on the Life Oncology page here for more cancer educational information.

The information is shared on condition that readers will make their own determination, including seeking advice from a healthcare professional. E&OE. Life Healthcare Group Ltd does not accept any responsibility for any loss or damage suffered by the reader as a result of the information provided.

 

Reference

1. American Cancer Society. Imaging (Radiology) Tests for Cancer. [online] 2015 Nov 30 [cited 2022 Jul 18]. Available from: URL: https://www.cancer.org/treatment/understanding-your-diagnosis/tests/imaging-radiology-tests-for-cancer.html.
2. John Hopkins Medicine. Mammogram Procedure. [online] [cited 2022 Jul 18]. Available from: URL: https://www.hopkinsmedicine.org/health/treatment-tests-and-therapies/mammogram-procedure.
3. American Cancer Society. Ultrasound for Cancer. [online] 2015 Nov 30 [cited 2022 Jul 18]. Available from: URL: https://www.cancer.org/treatment/understanding-your-diagnosis/tests/ultrasound-for-cancer.html.
4. American Cancer Society. CT Scan for Cancer. [online] 2015 Nov 30 [cited 2022 Jul 18]. Available from: URL: https://www.cancer.org/treatment/understanding-your-diagnosis/tests/ct-scan-for-cancer.html.
5. American Cancer Society. MRI for Cancer. [online] 2019 May 16 [cited 2022 Jul 18]. Available from: URL: https://www.cancer.org/treatment/understanding-your-diagnosis/tests/mri-for-cancer.html.
6. American Cancer Society. Nuclear Medicine Scans for Cancer. [online] 2019 Aug 29 [cited 2022 Jul 18]. Available from: URL: https://www.cancer.org/treatment/understanding-your-diagnosis/tests/nuclear-medicine-scans-for-cancer.html.