From the Guidelines
Doppler ultrasound is the preferred type of thyroid ultrasound for diagnosing Graves' disease. This specialized ultrasound technique measures blood flow within the thyroid gland, which is typically increased in Graves' disease due to the hypermetabolic state and increased vascularity of the gland 1. During the examination, the radiologist will look for specific findings including diffuse thyroid enlargement, heterogeneous echogenicity, and most importantly, significantly increased blood flow throughout the gland (known as "thyroid inferno" pattern).
The procedure is non-invasive, painless, and takes approximately 15-30 minutes to complete. While Doppler ultrasound is valuable for diagnosis, it should be used in conjunction with clinical assessment and laboratory tests measuring thyroid hormones (TSH, free T4, free T3) and thyroid-stimulating immunoglobulins (TSI) for a definitive diagnosis of Graves' disease 1. The ultrasound also helps exclude other causes of hyperthyroidism such as toxic nodules and can guide further management decisions including medication dosing or consideration of radioactive iodine therapy or surgery.
Some key points to consider when using Doppler ultrasound for diagnosing Graves' disease include:
- The importance of increased blood flow throughout the gland, which is a characteristic finding in Graves' disease 1
- The need to use Doppler ultrasound in conjunction with clinical assessment and laboratory tests for a definitive diagnosis 1
- The ability of Doppler ultrasound to exclude other causes of hyperthyroidism and guide further management decisions 1
From the Research
Types of Thyroid Ultrasound for Diagnosing Graves' Disease
- High-resolution ultrasound is used to diagnose Graves' disease, as seen in a study from 2 where 53 patients with Graves' disease were scanned with 10-MHz high-resolution ultrasound.
- The study found that a heterogeneous echo pattern was noted in 31 patients (60.4%) and was strongly suggested to be correlated with the severity of hyperthyroidism.
- Another study from 3 compared the diagnostic effectiveness of two TSH receptor antibody immunoassays, ultrasonography, and thyroid scintigraphy in hyperthyroidism scenarios, and found that thyroid ultrasonography is less accurate than both TRAb/TSI and thyroid scintigraphy.
Echo Patterns in Thyroid Ultrasound
- A study from 3 found that the 'thyroid inferno' pattern, also known as echo pattern 3, provides a high positive predictive value (PPV) for Graves' disease.
- The study reported a good sensitivity (92.1%) and a high PPV (95.2%) for the 'thyroid inferno' pattern, but a quite low specificity value (69.8%) and a relatively low negative predictive value (NPV) (57.5%).
Comparison with Other Diagnostic Methods
- Thyroid scintigraphy remains the most accurate method to differentiate causes of thyrotoxicosis, as reported in a study from 3.
- TRAb assays can be alternatively adopted in this setting, limiting the use of thyroid scintigraphy to TRAb-negative patients, as seen in a study from 3.
- A study from 4 found that thyroid-stimulating immunoglobulin (TSI) diagnostic performance for Graves' disease was excellent and had better sensitivity than TRAb.