Diagnostic ultrasound ( PDFDrive )

748 PART III Small Parts, Carotid Artery, and Peripheral Vessel Sonography
J
Tr
A
B
C
D
FIG. 20.18 Parathyroid Adenoma: Correlation of Ultrasound and CT. (A) Transverse sonogram shows a partially cystic ectopic supernumerary
parathyroid adenoma (arrow) posterior to the left internal jugular vein (J) but external to the carotid sheath. Left superior and inferior parathyroid
glands and the left thyroid lobe had previously been resected. Tr, Trachea. (B) Enhanced conventional axial CT image of the neck shows the same
partially cystic parathyroid adenoma. (C) Transverse sonogram in another patient shows a subcentimeter parathyroid adenoma posterior to the
right thyroid lobe (T). C, Common carotid artery. (D) Contrast enhanced axial CT of the neck shows the enhancing adenoma posterior to the right
thyroid lobe.
Computed tomography (CT) is also used in the evaluation
of parathyroid disease. More recently, thin-acquisition
thickness, multidetector CT (MDCT) with reconstruction has
been utilized with multiphase technique (“four-dimensional”
[“4D”]), and provides high-resolution, multiplane diagnostic
information based on the temporal perfusion characteristics
of parathyroid tissue 117-122 (Fig. 20.18). Successful imaging
requires experience in interpretation with close attention to
exam technique; in such studies, preoperative lateralization
of single gland parathyroid disease accuracies of 92% to 94%,
sensitivities of 88% to 92%, and speciicity of 93% have been
reported, with sensitivity decreasing to 43% in the setting of
multigland disease. 117-122 However, these examinations typically
utilize multiphase, thin-acquisition thickness techniques,
which lead to concerns of increased radiation exposure to the
patient, despite dose reduction with protocol modiications. In
addition, potential drawbacks of the technique include exam
costs and the need to administer iodinated IV contrast material.
herefore it has not been widely supported in the literature
as initial irst-line preoperative imaging method to detect
parathyroid disease.
Magnetic resonance imaging (MRI) is also a useful noninvasive
modality in the evaluation of parathyroid disease but is
not widely performed nor widely supported by the literature for
irst-line parathyroid imaging 44,111,123-127 (Fig. 20.19). As with
ultrasound, MRI is performed without the need for patient
radiation exposure; however, it is more expensive than ultrasound.
MRI has demonstrated particular utility in localizing mediastinal
adenomas and in the evaluation of the reoperative patient,
especially in cases when other functional and cross-sectional
imaging has been inconclusive.
he previously described modalities have largely replaced
angiography and venous sampling in the imaging of parathyroid
disease. 44,86,128 Selective venous sampling is more invasive,
expensive, and technically demanding than other imaging
modalities. However, it can be an occasional useful technique
to lateralize parathyroid disease, particularly in a high-risk
reoperative setting or when previous noninvasive imaging is
inconclusive. 128
he combination of multiple preoperative imaging studies
demonstrates improved sensitivity compared with singlemodality
evaluation. Combined imaging with ultrasound and
99m Tc sestamibi scintigraphy increases the sensitivity for the
preoperative diagnosis of parathyroid disease. 44,85,90,104,110-112 When
multiple studies are used, ultrasound is a good choice for initial
preoperative imaging because of its noninvasiveness, lack of
radiation exposure, relative low cost, high-resolution anatomic
detail, ability to assess for concomitant thyroid disease, and
competitive sensitivity and accuracy when used by an experienced
examiner. 92,103,110,111,113,115,116,129