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Diagnosis and tests

Imaging

When an X-ray, ultrasound, CT, MRI or PET scan is ordered for someone with leukemia, people often ask: “Will they see the leukemia on the scan?” This topic calmly explains why and when imaging is needed in leukemia, which questions it answers and which it does not.

Last updated: ~5 min read
A translucent human silhouette on a dark navy background with horizontal layers of light passing through it, softly showing the lungs, heart, liver and spleen; no facial features.
Figure 1.Concept: imaging is looking inside the body with light.

01Short answer

Leukemia is a disease of the blood and bone marrow, so it is diagnosed with tests, not scans. But imaging is used for several important purposes: a chest X-ray or CT to look for a mass in the middle of the chest (especially in T-ALL); finding lung infections, particularly fungal ones when immunity is low; ultrasound to measure the spleen, liver and lymph nodes; a CT or MRI of the brain when there are neurological symptoms; targeted scans for bone pain or complications; and vein ultrasound when a central line is placed. In CLL and some specific situations, CT or PET-CT may be used to assess the extent of disease or when a change to a more aggressive form is suspected. An echocardiogram is also a form of imaging and is needed before some drugs. The benefits and possible risks of each scan (radiation, contrast dye) are weighed by the doctor.

02Simple explanation

Leukemia cells are spread through the blood and marrow rather than gathered in one place as a “tumour”. So leukemia cannot be found on a scan — tests show it.

Imaging helps to see what is happening inside the body: whether the spleen is enlarged, whether there is a lung infection, whether there is a mass in the chest.

When immunity is low, lung infections can be hidden. A CT scan shows them earlier than an X-ray.

Ultrasound is radiation-free and painless: an easy way to look at the spleen, liver, lymph nodes and veins.

The doctor orders each scan for a specific question. It is completely normal to ask, “Which question will this scan answer?”

03Scientific explanation

The chest and T-ALL. According to the ACS, in ALL — especially T-cell ALL — there may be a mass in the middle of the chest (the mediastinum), around the thymus. It can press on the airways and large blood vessels, so a chest X-ray or CT is done at diagnosis. This also matters for the safety of anaesthesia or sedation.

Infections. During neutropenia, lung infections — especially fungal ones such as Aspergillus — may show up late on an X-ray. According to IDSA guidelines, a chest CT is used during prolonged neutropenia with persistent fever to pick up early signs of fungal infection. Imaging of the sinuses, abdomen and other organs is chosen according to symptoms.

Organs and extent of disease. Ultrasound or CT shows the size of the spleen, liver and lymph nodes. In CLL, CT is not always needed for a standard diagnosis but is used in clinical trials or certain situations. When a change from CLL to a more aggressive lymphoma (Richter transformation) is suspected, PET-CT can help choose where to take a biopsy.

Safety. According to RadiologyInfo, X-rays and CT use ionising radiation; the dose from CT is higher than from an X-ray, so the scan is done only when the benefit is clear. Ultrasound and MRI use no radiation. Iodine- or gadolinium-based contrast agents rarely cause allergy or affect the kidneys.

04What happens in the body?

Imaging does not find leukemia, but it helps

Leukemia cells are spread throughout the marrow and blood. So in most cases “leukemia” is not visible on a scan. Imaging shows the state of the organs, complications and infections — and that matters for keeping treatment safe.

The chest: a mass in T-ALL

In T-ALL there may be enlarged tissue in the middle of the chest. It can cause a cough, breathlessness and swelling of the face and neck. An X-ray or CT finds it, and doctors make decisions about anaesthesia, sedation and how urgent the situation is.

A translucent chest on a dark navy background; between the lungs, above the heart, an area of enlarged tissue is highlighted in soft warm light; no frightening details.
Figure 2.In T-ALL there can be a mass in the middle of the chest.

The lungs: seeing infection early

When neutrophils are very low during treatment, a lung infection can begin with very few symptoms. If a fever does not settle, a chest CT shows areas of infection early and helps choose the right antibiotic or antifungal medicine.

A layered cross-section of translucent lungs on a dark navy background; a small, soft amber spot in the right lung is marked with a ring of light.
Figure 3.CT can show a lung infection early.

The abdomen: spleen, liver, kidneys

Ultrasound shows the size of the spleen and liver, the state of the kidneys and lymph nodes in the abdomen. An enlarged spleen is common in CML and CLL; its shrinking during treatment can be one sign of response.

The head and nervous system

With a severe headache, changes in vision, seizures or weakness, a CT or MRI of the brain is done to rule out bleeding, infection or a build-up of leukemia cells. Checking the spinal fluid requires a lumbar puncture.

05The questions imaging answers

Each scan is for a specific question.

Chest — Is there a mass? Are the lungs healthy?1ChestIs there a mass? Are the lungs healthy?
Infection — Where is the hidden source of fever?2InfectionWhere is the hidden source of fever?
Organs — Are the spleen and liver enlarged?3OrgansAre the spleen and liver enlarged?
Brain — The cause of neurological symptoms.4BrainThe cause of neurological symptoms.
Safer treatmentComplications are found in time.
Early infection detectionThe right medicine is chosen quickly.
A clear pictureThe state of the organs is known.

06Imaging in leukemia: when and why

ScanCommon purposeRadiation
Chest X-rayMediastinal mass, pneumonia, position of a lineSmall
Chest CTFungal and other lung infections, size of a massYes (more than an X-ray)
Abdominal ultrasoundSpleen, liver, kidneys, lymph nodesNone
Brain CT or MRIHeadache, seizures, weakness, suspected bleedingCT: yes; MRI: none
PET-CTIn selected cases: suspected transformation in CLLYes
EchocardiogramHeart function before some drugsNone

* Only the treating team decides which scan is needed. Not every scan is done for every leukemia.

07Key terms

Imaging
Tests that show the inside of the body as pictures or video.
Mediastinum
The middle of the chest, the space between the lungs.
Contrast dye
A special liquid that makes vessels and organs show up more clearly.
Ionising radiation
The radiation used in X-rays and CT.
Splenomegaly
Enlargement of the spleen.
Richter transformation
A change from CLL to a more aggressive lymphoma.
Echocardiogram
An ultrasound scan of the heart.
Aspergillosis
An infection caused by the Aspergillus fungus, often in the lungs.

08Key points

  • Leukemia is diagnosed with tests, not scans.
  • Imaging checks organs, infections and complications.
  • In T-ALL there may be a mass in the chest.
  • CT shows lung infections earlier than an X-ray.
  • Ultrasound and MRI involve no radiation.
  • Mention allergies, kidney problems and implants beforehand.
  • It is normal to ask what each scan is for.

09Frequently asked questions

Why am I not having a CT? Do they not need to see the leukemia?

Leukemia spreads through the blood and marrow, so CT is not the main way to diagnose it or to measure the response to treatment. Blood, marrow and MRD tests are used for that. A CT is ordered only for a specific question.

Is the radiation from CT dangerous?

CT does involve radiation, but doctors order it only when the benefit clearly outweighs the risk — for example, when looking for a serious infection. You can ask why each scan is needed.

What should I know before contrast dye is given?

Say if you have ever had a reaction to contrast, have kidney problems or take metformin for diabetes. After the scan, drinking plenty of fluids is often advised unless your doctor has limited your fluids.

My platelets are low. Is the scan dangerous?

X-rays, ultrasound, CT and MRI do not cause bleeding themselves. Giving contrast into a vein needs only a simple needle. Invasive procedures such as biopsies are planned according to the platelet count.

What if a child cannot keep still during an MRI?

Young children sometimes have light sedation or a general anaesthetic. If there is a chest mass in T-ALL, anaesthesia is planned with particular care.

10Questions for your doctor

Take these questions to your appointment. The ones you save are collected on the “My questions” page and stay on this device only.

  1. Why am I not having a CT? Do they not need to see the leukemia?

  2. Is the radiation from CT dangerous?

  3. What should I know before contrast dye is given?

  4. My platelets are low. Is the scan dangerous?

  5. What if a child cannot keep still during an MRI?

My questions

12Sources

  1. American Cancer Society. Tests for Acute Lymphocytic Leukemia
  2. American Cancer Society. Tests for Acute Myeloid Leukemia (AML)
  3. American Cancer Society. Tests for CLL
  4. American Cancer Society. Imaging (Radiology) Tests for Cancer
  5. National Cancer Institute (NCI). Adult Acute Lymphoblastic Leukemia Treatment (PDQ®) — Patient Version
  6. National Cancer Institute (NCI). Computed Tomography (CT) Scans and Cancer
  7. NHS. Acute myeloid leukaemia — Tests and next steps
  8. NHS. Acute lymphoblastic leukaemia — Tests and next steps
  9. MedlinePlus (U.S. National Library of Medicine). Aspergillosis
  10. MedlinePlus (U.S. National Library of Medicine). Spleen Diseases
  11. RadiologyInfo.org (RSNA and ACR). Radiation Dose in X-Ray and CT Exams
  12. Clinical Infectious Diseases (IDSA), 2016. Practice Guidelines for the Diagnosis and Management of Aspergillosis: 2016 Update by the IDSA
Medical disclaimerThis information is for educational purposes only and does not replace medical advice.
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