Allocation of parathyroid adenoma and suspicious thyroid nodule by real-time ^99mTc-MIBI SPECT/US fusion imaging

Excerpt

A 58-year-old man presented with hypercalcemia caused by primary hyperparathyroidism (PTH: 290 ng/l). Imaging was performed for allocation of parathyroid adenoma. Ultrasonography (US) showed multinodular goiter with a large (4.5-cm diameter), hypoechoic, inhomogeneous, unsharp nodule caudally in the right lobe, representing potential criteria of malignancy. Caudodorsally, a small (1.5-cm diameter) hypoechoic lesion was detected with no further malignant signs whereby the differentiation toward the thyroid was sonomorphologically vague, leaving a marginal thyroid nodule or an enlarged parathyroid gland as potential differential diagnoses. ^99mTc-pertechnetate scintigraphy proved both nodules to be hypofunctional (Fig. 1a). ^99mTc-methoxyisobutylisonitrile (MIBI) scintigraphy (Fig. 1b) and single-photon emission computed tomography (SPECT; not shown) demonstrated a great area of reduced uptake in the right caudal part but a slight spot caudodorsally, which showed no correlation on ^99mTc-pertechnetate scintigraphy. This conventional work-up failed to precisely match the MIBI spot, which was most probably caused by the small hypoechoic nodule; however, a partial MIBI accumulation of the large suspicious nodule had to be considered.

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