Toxic multinodular goiter other imaging findings
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Mazia Fatima, MBBS [2]
Overview
Radioidodine uptake may be helpful in the diagnosis of multinodular goiter.Patchy pattern of increased radionuclide uptake in more than one nodule associated with decreased uptake in the surrounding extranodular thyroid tissue is characteristic of toxic multinodular goiter.
Thyroid Scintigraphy
- Radioidodine uptake may be helpful in the diagnosis of multinodular goiter.
- Findings on an thyroid nuclear scintigraphy suggestive of multinodular goiter include enlarged gland, with heterogeneous uptake that determines the activity of the gland.
- Patchy pattern of increased radionuclide uptake in more than one nodule associated with decreased uptake in the surrounding extranodular thyroid tissue is characteristic of toxic multinodular goiter.
- Commonly used isotopes are Tc-99m pertechnetate or radioiodine (I123).These isotopes are preferred over isotope sodium iodide-131 (Na 131 I) due to their shorter half-life and comparitively lower radiation exposure.
- 123 I scanning is preferred over 99m Tc scan. 99m Tc scanning may provide misleading results as 99m Tc is trapped in the thyroid but is not organified. Some nodules that appear hot or warm on 99m TC scan results may be cold on 123 I scan results.
- Based on uptake of radioactive isotope thyroid nodule can be divided into:
- Hot nodule: suggestive of autonomously functioning nodules.
- Warm nodule: indicates normal thyroid function.
- Cold nodule: suggestive of hypofunctional or nonfunctional thyroid tissue.
- 5-8% of warm or cold nodules are malignant, however hot nodules are rarely malignant.
Differentiation based Functional (Nuclear) Imaging for Thyrotoxicosis
| Functional (Nuclear) Imaging for Thyrotoxicosis | |||||
| Diagnosis | Degree of Thyrotoxicosis | Radioactive iodine Uptake | Scintigraphy Image | ||
|---|---|---|---|---|---|
| Toxic multinodular goiter | +/++ | Normal or +/++ | Enlarged gland with multiple "hot" or "cold" nodules | ||
| Grave's disease | ++++ | ++++ | Enlarged gland with homogenous uptake | ||
| Thyrotoxic phase of subacute thyroiditis | ++++ | <1% at 4 or 24 hr. | Absent isotope uptake | ||
| Toxic adenoma | +/++ | Normal or +/++ | Dominant "hot" nodule with low or absent uptake in the surrounding normal gland. | ||
Other Imaging Findings
Differentiation based Functional (Nuclear) Imaging for Thyrotoxicosis
| Functional (Nuclear) Imaging for Thyrotoxicosis | |||||
| Diagnosis | Degree of Thyrotoxicosis | Radioactive iodine Uptake | Scintigraphy Image | ||
|---|---|---|---|---|---|
| Toxic multinodular goiter | +/++ | Normal or +/++ | Enlarged gland with multiple "hot" or "cold" nodules | ||
| Grave's disease | ++++ | ++++ | Enlarged gland with homogenous uptake | ||
| Thyrotoxic phase of subacute thyroiditis | ++++ | <1% at 4 or 24 hr. | Absent isotope uptake | ||
| Toxic adenoma | +/++ | Normal or +/++ | Dominant "hot" nodule with low or absent uptake in the surrounding normal gland. | ||