1-23I-MIBG thyroid uptake: Implications for MIBG imaging of the heart

Abstract

The thyroid visualization in MIBG imaging is likely an expression of thyroid sympathetic innervation. The differences in TWO and T/M ratio in cardiac and neurological patients probably express differences in thyroid dopaminergic receptors. Thus, pre-treatment with potassium perchlorate or Lugol's solution may not be justified in patients undergoing 123I-MIBG imaging in whom the risk of side effects due to pre-treatment could be higher than the risk due to thyroid radiation exposure.

123I-Metaiodobenzylguanidine cardiac innervation imaging: methods and interpretation

“…Friedman et al [9] found that there was no statistical difference in the thyroid uptake between subjects receiving blockade medication compared to those not undergoing pre-treatment. More recently, Giubbini et al [10] reported similar results in patients studied for cardiac or neurological disorders in three different centers in Italy. They found no significant differences both in tracer washout from the thyroid or 4-h thyroid-to-mediastinum ratio between patients pre-treated or not by thyroid blocking agents [10].…”

“…More recently, Giubbini et al [10] reported similar results in patients studied for cardiac or neurological disorders in three different centers in Italy. They found no significant differences both in tracer washout from the thyroid or 4-h thyroid-to-mediastinum ratio between patients pre-treated or not by thyroid blocking agents [10]. These findings suggest that there is a certain amount of uptake that cannot be prevented, supposedly due to 123 I-MIBG uptake in thyroid sympathetic nerve terminals rather than uptake of free iodine.…”

“…In a previous study, Melander et al [11] pointed out that the noradrenaline released from inter-follicular adrenergic nerve terminals has a stimulatory influence of the sympathetic nervous system on the secretion of thyroid hormone and that there was an age-related reduction of the sympathetic innervation in human thyroid tissue. Giubbini et al [10] demonstrated that 123 I-MIBG thyroid uptake is lower in patients with neurological disorders than in those with cardiac diseases. Tipre et al [12] and Matsui et al [13] showed that sympathetic nervous denervation, and consequently reduced 123 I-MIBG uptake, is present in the heart but also in extra-cardiac tissues, such as thyroid, in Parkinson's disease.…”

Misdiagnosis of Paraganglioma by 123I-mIBG Without Stable Iodine Blockade of Thyroidal Radioiodine Uptake

“…In 2014, one study reported that thyroid uptake and scans for patients who were undergoing 123 I-mIBG for cardiac imaging were not statistically different between individuals who received stable iodine blockade 1 hour prior to the tracer injection and those who did not receive blockade [ 6 ]. The authors suggested that the accumulation of mIBG tracer in the thyroid sympathetic nerves, rather than actual thyroid uptake, resulted in the “uptake” seen in the blocked thyroid [ 6 , 17 ]. Another study in 2016 [ 17 ], conducted in patients undergoing 123 I-mIBG for cardiac and neurological conditions (congestive heart failure and Parkinson disease, respectively), reported similar results, suggesting that thyroid blockade may not be justified.…”

Thyroid blockade in 123I-mIBG cardiac imaging: A common sense approach

“…8 There were differences in thyroid and cardiac uptake patterns between the cardiology and neurology patients but no difference in thyroid parameters (thyroid/mediastinum ratio and washout) between patients who did and did not receive thyroid blockade. The authors conclude that thyroid uptake on 123 I-mIBG imaging is primarily a reflection of sympathetic neuronal activity and therefore use of thyroid blockade pretreatment to prevent uptake of free iodide may not be justified.…”