Diagnostic ultrasound ( PDFDrive )

CHAPTER 20 The Parathyroid Glands 747
sonography has demonstrated some of the highest sensitivities
and accuracies of all modalities for adenoma detection in the
reoperative setting, especially when combined with ultrasoundguided
FNA biopsy of a suspected parathyroid adenoma. 57,59,60,62,64,100-
103
Ultrasound augmented by FNA biopsy and PTH assay can
lead to a speciicity approaching 100%, a sensitivity of 84% to
90%, and an accuracy 82% to 84%. 60,103 It is important to understand
that in most large clinical series of patients undergoing
reoperation for hyperparathyroidism, the great majority of
parathyroid adenomas are still found in the neck or are accessible
through a neck incision. 59-61,64 herefore a thorough ultrasound
examination of the neck is important in these reoperative patients.
If the adenoma is not visible sonographically, an ectopic mediastinal
location must be considered. here should be a low
threshold to utilize multiple imaging modalities, especially when
initial imaging indings are ambiguous or the surgical risk is
high. 57,60,61,64 his approach signiicantly improves the success
rate and decreases the procedural time and cost in the reoperated
patient. 57,59,60
Other Modalities
Another widely used imaging modality for parathyroid localization
is scintigraphy with technetium-99m ( 99m Tc) labeled agents,
providing combined functional and anatomic imaging in the
primary preoperative imaging of patients with parathyroid
disease. 44,81,85,88,104-111 99m Tc sestamibi scintigraphy, using singleisotope,
dual-phase (“washout”) imaging, or dual-isotope,
single-phase (“subtraction”) imaging, particularly when combined
with single-photon emission computed tomography (SPECT)
or SPECT/CT, has sensitivity similar to or better than ultrasound
44,62,81,85,104-109,111-116 (Fig. 20.17). Scintigraphy can demonstrate
adenomas in areas that are missed by ultrasound, including the
mediastinum and retrotracheal space. However, scintigraphy is
more expensive than ultrasound and requires the use of ionizing
radiation. As with ultrasound, parathyroid scintigraphy also
appears to be less sensitive and accurate in multiglandular
parathyroid disease, for smaller adenomas, and in the presence
of multinodular thyroid disease. 92,93,111
A
B
FIG. 20.17 Ectopic Intrathyroid Parathyroid Adenoma. Correlation of ultrasound and scintigraphy. (A) Longitudinal sonogram of the left neck
in a patient with persistent hyperparathyroidism shows a heterogeneous ectopic intrathyroid parathyroid adenoma (arrows). T, Thyroid. (B) Corresponding
anterior projection using 99m Tc sestamibi (left image) and iodine-123 (middle image) dual-agent subtraction (right image) coronal SPECT
imaging shows a concordant focal area of increased activity (arrows) in the left thyroid lobe, which corresponds to the ectopic intrathyroid parathyroid
adenoma.