**Pearls/pitfalls**

a.Dual isotope subtractional scintigraphy with 99mTc-pertehnetat/99mTc sestamibi or 99mTc-pertehnetat/99mTc-tetrofosmin allows visualization of abnormal parathyroid glands after subtraction is performed, even on the early obtained images.

#### **Figure 9.**

*(а) Dual-isotope subtractional scintigraphy with 99mTc-pertehnetat/99mTc sestamibi. Subtractional image showing no residual activity in the areas of the neck and chest and (b) late planar images showing a residual activity (arrow) in the middle of the left thyroid lobe, consistent with left parathyroid adenoma.*

**59**

**Figure 10.**

*Parathyroid Scintigraphy*

*DOI: http://dx.doi.org/10.5772/intechopen.90341*

This helps to shorten the time of examination to 80–90 min and is of great use in the postsurgical follow up and when more than one abnormal gland is present.

b.Disadvantages of the subtractional scintigraphy with 99mTc-pertehnetat/99mTc sestamibi or 99mTc-pertehnetat/99mTc-tetrofosmin are: necessity of applying of two radionuclides, the need of very precise positioning of the patients in this dual phase method requiring full collaboration from patient's side and the

*(а) Dual-isotope subtractional method with 99mTc-pertehnetat/99mTc-tetrofosmin. The upper row: on the left image of the thyroid gland with 99mTc-pertehnetat and on the right image of the parathyroid gland with 99mTctetrofosmin (arrow). The lower row shows subtractional image representing adenoma of left parathyroid gland and (b) dual-isotope subtractional method with 99mTc-pertehnetat/99mTc-tetrofosmin early SPECT images* 

*showing an area of hyper fixation, located caudally of the left thyroid lobe.*

probability of the presence of artifacts in the obtained images.

*Medical Isotopes*

sensitivity (**Figures 9** and **10**).

**Pearls/pitfalls**

syndrome—pheochromocytoma, parathyroid adenoma and prolactinoma, who had previously undergone thyroid (subtotal thyroidectomy) and parathyroid (left upper parathyroid gland) surgery. Subtractional images (**Figure 8a**) and early SPECT images (**Figure 8b**) show two areas of intense uptake located below the remnants of the both thyroid lobes. SPECT images show that the lesion below the right thyroid

In some cases, obtaining late images could also be of help. Combining dualisotope, 99mTc-pertehnetat/99mTc sestamibi, subtractional scintigraphy with SPECT, and also recording late planar images on the 120th min (late phase) would improve

a.Dual isotope subtractional scintigraphy with 99mTc-pertehnetat/99mTc sestamibi or 99mTc-pertehnetat/99mTc-tetrofosmin allows visualization of abnormal parathyroid glands after subtraction is performed, even on the early obtained images.

*(а) Dual-isotope subtractional scintigraphy with 99mTc-pertehnetat/99mTc sestamibi. Subtractional image showing no residual activity in the areas of the neck and chest and (b) late planar images showing a residual* 

*activity (arrow) in the middle of the left thyroid lobe, consistent with left parathyroid adenoma.*

lobe was located also adjacent to the back part of the right thyroid lobe.

**58**

**Figure 9.**

This helps to shorten the time of examination to 80–90 min and is of great use in the postsurgical follow up and when more than one abnormal gland is present.

b.Disadvantages of the subtractional scintigraphy with 99mTc-pertehnetat/99mTc sestamibi or 99mTc-pertehnetat/99mTc-tetrofosmin are: necessity of applying of two radionuclides, the need of very precise positioning of the patients in this dual phase method requiring full collaboration from patient's side and the probability of the presence of artifacts in the obtained images.

#### **Figure 10.**

*(а) Dual-isotope subtractional method with 99mTc-pertehnetat/99mTc-tetrofosmin. The upper row: on the left image of the thyroid gland with 99mTc-pertehnetat and on the right image of the parathyroid gland with 99mTctetrofosmin (arrow). The lower row shows subtractional image representing adenoma of left parathyroid gland and (b) dual-isotope subtractional method with 99mTc-pertehnetat/99mTc-tetrofosmin early SPECT images showing an area of hyper fixation, located caudally of the left thyroid lobe.*

#### **Figure 11.**

*Single-isotope, dual-phase scintigraphy with 99mTc-sestamibi in a patient with secondary hyperparathyroidism. The late phase (120 min) show a focus of residual activity (arrow)—consistent with parathyroid adenoma (probably tertiary hyperparathyroidism).*

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*Parathyroid Scintigraphy*

SHPT than in PHPT.

**5. Conclusions**

modalities.

parathyroid cells:

a.biochemical factors

seen in patients with positive scans.

• Parathyroid hormone levels.

for positive scans.

• Vitamin D levels.

*DOI: http://dx.doi.org/10.5772/intechopen.90341*

Secondary hyperparathyroidism is characterized with hyperplasia of parathyroid glands, because it is caused by longstanding uncontrolled hypocalcemia, which leads to a profound overstimulation of a previously normal parathyroid glands. Over time this overstimulation causes hyperplasia and eventually adenomatous changes (tertiary hyperparathyroidism) of the parathyroid glands with PTH levels far more exceeding those observed in PHPT (**Figure 11)**. Nevertheless, hyperplastic parathyroid glands usually show faster wash out of the radionuclides in comparison to solitary adenomas, which makes them more difficult to be visualized with scintigraphy (**Figure 12)**. Negative scans, may be associated with the possible suppression of the accumulation of radiopharmaceuticals in the parathyroid cells as a result of the concomitant calcitriol intake. The use of calcium channel blockers may affect the uptake of 99mTc-sestamibi by parathyroid cells and reduce the sensitivity of the method. A study found that negative scans are twice as likely in patients taking calcium antagonists than those who do not take these medications (OR2, 88.95% CI, 1.03–8.10, p 0.045) [58]. So, adding the poor general condition of the patients, pathologically changed parathyroid glands are more difficult to be localized in

The visualization of abnormal parathyroid glands is difficult due to their variations in number and localization. Noninvasive parathyroid imaging studies include 99mTc-sestamibi scintigraphy, ultrasonography, computed tomography scanning, magnetic resonance imaging, and positron emission tomography. There is a general consensus that the most sensitive and specific imaging modality is the scintigraphy with 99mTc-sestamibi or 99mTc-tetrofosmin. 99mTc-sestamibi scintigraphy significantly increases the role of preoperative scintigraphy in patients with hyperparathyroidism and allows unilateral surgical approach with minimally invasive parathyroidectomy to be used. Generally three protocols with the use of two radiopharmaceuticals, 99mTc-sestamibi or 99mTc-tetrofosmin, are most widely applied: single-phase dual-isotope subtraction, dual-phase single-isotope and combination of both. Each one of them has specific advantages and disadvantages. While, single parathyroid adenomas are localized with greater precision, hyperfunctioning parathyroid hyperplastic cells represent a real challenge to the imaging

Several factors can influence the radionuclide uptake in pathologically changed

• Total calcium levels—higher preoperative calcium levels are more frequently

• A significant correlation between radiopharmaceutical uptake and preoperative levels of PTH is observed. As higher PTH is, as higher is the possibility

**4.4 Secondary hyperparathyroidism**

#### **Figure 12.**

*(а) Single-isotope, dual-phase scintigraphy with 99mTc-tetrofosmin in a patient with secondary hyperparathyroidism. Early (20 min) and late (120 min) images show no focus of a residual activity in the area of neck and mediastinum and (b) (same patient) early SPECT images showing an area of nuclide accumulation caudally of the left thyroid lobe, suspicious for parathyroid adenoma.*

*Medical Isotopes*

**Figure 11.**

*(probably tertiary hyperparathyroidism).*

*Single-isotope, dual-phase scintigraphy with 99mTc-sestamibi in a patient with secondary hyperparathyroidism. The late phase (120 min) show a focus of residual activity (arrow)—consistent with parathyroid adenoma* 

*(а) Single-isotope, dual-phase scintigraphy with 99mTc-tetrofosmin in a patient with secondary hyperparathyroidism. Early (20 min) and late (120 min) images show no focus of a residual activity in the area of neck and mediastinum and (b) (same patient) early SPECT images showing an area of nuclide* 

*accumulation caudally of the left thyroid lobe, suspicious for parathyroid adenoma.*

**60**

**Figure 12.**
