MRI for Thyroid Cancer Detection

A thyroid MRI (magnetic resonance imaging) is a non-invasive imaging test that provides high-resolution images of the thyroid gland and adjacent neck structures, making it a valuable tool in modern thyroid disease assessment. This procedure is particularly helpful in staging known or suspected thyroid malignancy, monitoring for recurrence, and evaluating complex cases such as large goitres, cysts, or nodules when other imaging modalities such as ultrasound or computed tomography (CT) are insufficient¹.

Why You Might Need a Thyroid MRI

A thyroid MRI might be recommended for several clinical reasons:

Evaluating the Extent of Large Substantial Goitres

• MRI has excellent sensitivity for evaluating the extent of goitres, which might be compressing nearby structures².

Thyroid Cancer Staging

• After a diagnosis of thyroid cancer, an MRI helps determine the extent of disease by visualising local structures and detecting invasion beyond the thyroid capsule³. 
• This guides treatment planning and surgical decision-making.

Concern for Local Invasion

• When there is a suspicion that a thyroid mass is invading nearby critical structures (like the trachea, oesophagus, carotid arteries, or recurrent laryngeal nerve)⁴.
• MRI offers superior soft tissue contrast for defining the relationship of the mass to these organs.

How to Prepare for Your Thyroid MRI

Here are a few tips to help you prepare for your MRI⁵:

• Take your usual medications and eat normally, unless instructed to fast for sedation or contrast. Avoid heavy caffeine intake and stay hydrated.
• Inform staff about any metal implants or devices, and bring safety cards for “MR-Conditional” implants, such as pacemakers or aneurysm clips.
• Remove all metal items, including jewellery, hairpins, dental plates, and transdermal patches with foil, to prevent image distortion.
• Wear comfortable, metal-free clothing; ask about earplugs, music, or mirror goggles if you’re claustrophobic.
• If contrast is planned, fast for 4–6 hours prior to the procedure. Inform staff about any kidney issues or past reactions to contrast agents, as safer alternatives may be available.
• Arrange an escort home if you need sedation for claustrophobia.

You can read more about preparation for Ezra’s MRI Scan with Spine here.

What Happens During the Thyroid Scan?

Upon arrival for your MRI, you will need to check in and complete a screening form. This will allow you to confirm the presence of implants, allergies, and whether you might need any anxiety medication.

During the scan, you will lie down on a sliding table. A dedicated surface or phased-array coil is typically placed over the limb or region of interest⁶. Your head will be nestled in a small cushion that will keep you still. The scan typically lasts 30-45 minutes of actual “table time”, during which the technician may acquire multiple sequences (settings). Expect loud knocking noises (up to 110 dB); earplugs or headphones are provided to reduce discomfort. It’s normal to feel mild table vibrations.

You’ll stay in touch with the team via a two-way intercom and a squeeze bulb, allowing you to communicate or pause the scan if needed. If contrast is required, it’s injected halfway through, possibly causing a brief cool sensation. After the final sequence, the coil is removed, and you’re free to go. 

At Ezra, our MRI Scan with Spine scan takes around 60 minutes total, with 45 minutes of table time. Earplugs or headphones are available.

After the scan, you will be contacted by a medical provider working with Ezra within roughly a week. On the day of the appointment, you will receive a copy of your report and access to your scanned images through the online portal.

MRI Safety, Risks, & Side Effects

MRI is generally considered very safe when proper screening and protocols are followed, but certain risks and side effects should be understood:

• Metal and implants: The strong 3-Tesla magnet can pull or heat older pacemakers, aneurysm clips, or metal fragments⁷. Most modern “MR-Conditional” devices (like cochlear implants or pain pumps) are safe after screening, but all implants must be checked before scanning⁸.
• Gadolinium contrast: Macrocyclic gadolinium agents (e.g., gadobutrol) have an extremely low risk of allergic reactions or nephrogenic systemic fibrosis (NSF) when kidneys are healthy⁹. However, gadolinium can accumulate in tissues, and rare side effects such as headaches or skin changes have been reported. Many centres now offer contrast-free alternatives for routine follow-up¹⁰. You can read more about gadolinium contrast side effects here.
• Incidental findings: Large retrospective studies have found that thyroid incidentalomas are reported in approximately 3.5 per cent of neck or cervical spine MRIs¹¹.
• Claustrophobia: Anxiety inside the scanner is common. Wide-bore scanners, music, mirror goggles, or a single dose of oral sedative can help alleviate symptoms. Open MRI is an option if image detail can be sacrificed.
• Zero Ionising Radiation: MRI uses magnetic fields and radio waves, not X-rays, so there is no ionising radiation exposure, making it safer for repeated scans compared to CT scans¹².
• Minor Sensations: Expect loud knocking, mild table vibration, and a brief cool flush if contrast is injected. Rare side effects include headaches, fatigue, or mild skin heating.

A deeper dive into possible side effects (such as heat, headaches, and gadolinium deposition) is available in our full guide.

At Ezra, we employ a contrast-free approach using wide-bore T3 machines to deliver a comfortable scanning experience.

Terms You Might See in Your MRI Report (And What They Mean)

MRI reports of the thyroid include specific terms that help clinicians assess the nature of a lesion or condition. Some common terms (and their meanings) include: 

Heterogeneous Signal: Indicates the nodule or thyroid tissue has mixed signal intensity, often due to the presence of different tissue types. This can raise suspicion for malignancy, but is nonspecific¹³.

Extrathyroidal Extension (ETE): Refers to the spread of a tumour beyond the thyroid gland itself into surrounding tissues, which is typically a sign of more aggressive disease.

Apparent Diffusion Coefficient: A numerical value from diffusion-weighted imaging (DWI); low ADC values are often associated with cancer because malignant tissue tends to restrict water movement.

Restricted Diffusion: Seen when water molecule movement is limited within a lesion, suggesting high cellularity, which is suspicious for malignant nodules.

Enhancement: Refers to how a thyroid lesion absorbs contrast dye. Malignant tissue often enhances more than benign tissue, suggesting increased vascularity or abnormal tissue behaviour.

Mass Effect: Indicates that a thyroid lesion is exerting pressure on or displacing adjacent structures, which may signify substantial size or aggressive growth.

Ezra provides a radiologist-reviewed report in a non-technical and easy-to-understand format on your dashboard.

After the MRI Scan

After the MRI scan, you will be free to go home and continue with your day without any precautions¹⁴. If you received a sedative, you will need another person to pick you up. You will also not be able to drive, consume alcohol, or operate heavy machinery 24 hours after the sedative. 

A team of experts will review your results and determine whether a follow-up is necessary and recommend the appropriate treatment if needed. If abnormalities are found, you may undergo ongoing monitoring every 2-3 months to track recurrence. You can receive support in the form of counselling and advice on how to handle aspects like claustrophobia. 

If you have a scan with us here at Ezra, you will receive your report within five to seven days and have the option to discuss it with a medical practitioner. You can also access your scan images through the online portal.

What MRI Can Show About Thyroid Cancer

MRI is a valuable tool in thyroid imaging, offering detailed insights into nodule composition, tumour spread, invasion of surrounding tissues, and lymph node involvement. It can detect imaging characteristics that help differentiate malignant from benign thyroid nodules.

Solid, Cystic, or Mixed Nodules

MRI can show whether a thyroid nodule is solid, cystic, or mixed¹⁵. This distinction is foundational to risk assessment, as solid elements raise concern for cancer, while purely cystic nodules are almost always benign.

Extrathyroidal Extension

MRI accurately detects extrathyroidal extension, which means the tumour has spread beyond the thyroid gland itself into surrounding tissues like muscle or fat^1,15. This finding signifies a more advanced or aggressive disease and affects treatment plans significantly.

Invasion of Adjacent Structures

MRI can clarify whether cancer is invading key structures near the thyroid, such as the windpipe, nerves, and major blood vessels, which is critical for surgical planning and prognosis^1,16.

Lymph Node Evaluation

MRI is sensitive in detecting suspicious lymph nodes in the neck^1,15,16. Enlarged or abnormal appearing nodes may indicate metastatic spread, necessitating further evaluation or biopsy.

Tissue Characteristics Suggesting Malignancy

Tissue features like restricted diffusion and pronounced contrast enhancement often suggest malignancy in a thyroid lesion¹⁵. Malignant tumours typically show lower ADC values and greater enhancement compared to benign nodules.

Types of Thyroid Tumours and MRI Appearance

MRI can distinguish between different types of thyroid tumours by revealing their structural and signal characteristics. Each tumour type displays specific features helpful for diagnosis and management decisions.

• Papillary Thyroid Carcinoma (PTC)

PTC is the most common thyroid cancer. On MRI, it usually appears as a solid mass with irregular margins, showing restricted diffusion (low ADC values) and is sometimes associated with lymph node metastasis. The solid components often display a hypointense signal on T2-weighted images compared to benign nodules. Ill-defined margins and extrathyroidal extension are also frequent.

• Follicular Carcinoma

Follicular carcinomas often appear brighter than normal thyroid tissue on T2-weighted scans and tend to stand out after contrast is given. The shape may be irregular, with edges that are not clearly defined. Sometimes you may see a thin dark rim around the tumour, but if this rim is incomplete or broken, it suggests the tumour has pushed through its capsule and may also show areas where it is invading blood vessels^18,19. These changes help doctors distinguish follicular carcinoma from less harmful lumps, even when their signal is otherwise similar.

• Anaplastic Carcinoma

The solid components of anaplastic thyroid carcinoma frequently show hyperintensity on T2-weighted images compared to the spinal cord¹⁷. It also often presents with ill-defined margins and shows a higher incidence of extension out of the thyroid, tracheal, and oesophageal invasion, vascular invasion, and venous thrombosis, reflecting their aggressive nature.

• Benign Nodules

Benign thyroid nodules are usually well-defined, homogenous lesions that do not enhance (or only mildly enhance) after contrast administration¹⁵. Simple cystic nodules have very high T2 signal intensity and lack solid components or invasive features. Solid benign nodules show higher T2 signal and ASC values than malignancies, reflecting their lower cellularity.

Ezra screens for over 500 conditions, including the brain.

Types of MRI Scans Used in Thyroid Cancer Detection

There are several types of MRI scans, each providing unique information to help visualise the thyroid gland and detect cancer^3,15. 

• T1-weighted images provide detailed anatomical views of the thyroid and surrounding structures, making it easier to identify a tumour and any bleeding within the gland. This scan highlights differences in tissue composition and helps outline the boundaries of the thyroid.
• T2-weighted imaging is particularly effective for distinguishing fluid-filled or cystic areas within the thyroid from solid components. It can reveal whether a nodule is mostly solid, making cancer more likely, or contains fluid, which often suggests a benign process.
• DWI detects how water molecules move through the thyroid tissues. If movement is restricted (seen as low ADC values), this may point toward malignancy as cancer cells tend to pack tightly together, blocking normal water flow. 
• Contrast-enhanced MRI uses a special dye to highlight vascular patterns and tumour invasion in the thyroid. Cancers often absorb more contrast than normal tissue, making them easier to spot and assess for spread into blood vessels or nearby soft tissue. 

Cost

Ezra’s MRI Scan with Spine costs £2,395 and is currently available at their partner clinic in Marylebone, London and in Sidcup, with more locations planned in the future. No referral is required, so you can book your scan directly without consulting a GP or specialist first. Most people pay out-of-pocket, as insurance typically does not cover self-referred scans, but you may be able to seek reimbursement depending on your policy. 

Frequently Asked Questions

Is MRI better than ultrasound for thyroid cancer?

Ultrasound is usually the first and most cost-effective test for thyroid cancer, but MRI can provide extra detail for larger or complex cases, especially involving invasion outside the thyroid.

Will I need a biopsy even after an MRI?

A biopsy is still needed to definitively diagnose thyroid cancer, even if MRI findings are suspicious.

Is MRI safe for repeated use?

MRI does not use radiation and is considered safe for repeated use.

Key Takeaways

• Thyroid MRI is an important tool for accurately detecting and staging thyroid cancer, especially when assessing how far the disease has spread and guiding treatment decisions.
• MRI provides highly detailed images of the thyroid and nearby tissues, which is especially useful for spotting tumour invasion, lymph node involvement, and planning surgery.
• The procedure requires little preparation, is non-invasive, and is considered very safe, even for repeated scans, as it does not use radiation.
• Knowing how to understand your MRI report can help you make more informed choices with your healthcare team and have greater confidence in your care pathway.