*4.2.2 Single-isotope dual-phase scintigraphy with 99mTc-tetrofosmin*

99mTc-tetrofosmin, another myocardial perfusion agent, is also used for parathyroid scintigraphy, but there are limited data in the literature for its use. Several

#### **Figure 3.**

*(a) Single-isotope dual-phase scintigraphy with 99mTc-sestamibi. Early planar images show diffuse uptake in the thyroid gland. Late planar images show no sign of a focus of residual activity in the neck area or mediastinum. (b) (The same patient) 99mTc-sestamibi SPECT images show an area of a residual activity, located dorsally and caudally of the left thyroid lobe (arrows) suspicious for a parathyroid adenoma.*

**53**

**Figure 4.**

*and caudally of the left thyroid lobe.*

*Parathyroid Scintigraphy*

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

localizing parathyroid adenomas.

studies [26, 27] assess the diagnostic value of 99mTc-tetrofosmin scintigraphy for topic localization of the hyperfunctioning parathyroid glands in patients with PHPT. They show that this method was useful for the clinical practice and that the accumulation of 99mTc-tetrofosmin depended on the weight of the tumor and the level of PTH. The early images (15th min) prove to be better than the late ones (120th min). 99mTc-tetrofosmin is washed out more slowly from the thyroid gland than 99mTc-sestamibi but both radionuclides give better results in comparison with 99mTc-pertechnetate/201Tl-substractional technique [56]. 99mTc-tetrofosmin looks promising alternative of 99mTc-sestamibi with similar properties and capabilities of

Dual-isotope substractional scintigraphy with 99mTc-tetrofosmin/99mTc-pertechnetate and SPECT represent highly sensitive method for localization of parathyroid adenomas and their combination can further improve the diagnostic precision [57]. 99mTc-tetrofosmin, like 99mTc-sestamibi is not perfect for localization of hyperplastic parathyroid glands in patients with SHPT, because of its lower sensitivity [56]. 99mTc-tetrofosmin has some similarities with 99mTc-sestamibi, but its mechanism of accumulation in the cells is different. In contrast with 99mTc-sestamibi, which accumulation depends on mitochondria's membrane potential, retention of 99mTctetrofosmin depends mainly on cell's membrane potential [25]. 99mTc-tetrofosmin, shows slower wash out from the thyroid on the late planar images (120 min). This leads to the necessity to obtain additional later planar images—between 150 and 160 min. This slower wash out makes 99mTc-tetrofosmin to be unsuitable for performing single-isotope, dual-phase scintigraphy [25]. To avoid misleading, because of prolonged retention of the radiopharmaceutical in the thyroid adenomas, an US

examination should be performed, especially in iodine deficient areas [56]. **Figure 5** is presented a single-isotope dual-phase scintigraphy with 99mTc-

In 99mTc-tetrofosmin scintigraphy early images at 20th min show better quality

*Early 99mTc-sestamibi SPECT images showing an area of radionuclide accumulation (arrows), located dorsally* 

tetrofosmin, combined with SPECT in a patient with PHPT.

than the later ones at 120th min (**Figure 6a–c**). Late planar images (120 min)—negative scan.

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

*Medical Isotopes*

sestamibi with SPECT can be of great help.

In some cases, the obtained early and late images show no signs of abnormal accumulation of radionuclide, but when combined with SPECT, than adenomas located at the back of the thyroid gland become visible (**Figure 3a** and **b**).

So, the combination of a single-isotope dual-phase scintigraphy with 99mTc-

AP-images, and rarely this was combined with lateral and oblique images [52, 53].

*4.2.2 Single-isotope dual-phase scintigraphy with 99mTc-tetrofosmin*

During many years in the past, two-dimensional images have been obtained, mainly

SPECT has gained more importance, because it gives three-dimensional images. There are accumulating data from the literature, that it improves sensitivity for discovering and localizing the hyperfunctioning parathyroid glands [54, 55]. The main reason for this is the improved contrast resolution of SPECT (**Figure 4**).

99mTc-tetrofosmin, another myocardial perfusion agent, is also used for parathyroid scintigraphy, but there are limited data in the literature for its use. Several

*(a) Single-isotope dual-phase scintigraphy with 99mTc-sestamibi. Early planar images show diffuse uptake in the thyroid gland. Late planar images show no sign of a focus of residual activity in the neck area or mediastinum. (b) (The same patient) 99mTc-sestamibi SPECT images show an area of a residual activity, located dorsally and caudally of the left thyroid lobe (arrows) suspicious for a parathyroid adenoma.*

**52**

**Figure 3.**

studies [26, 27] assess the diagnostic value of 99mTc-tetrofosmin scintigraphy for topic localization of the hyperfunctioning parathyroid glands in patients with PHPT. They show that this method was useful for the clinical practice and that the accumulation of 99mTc-tetrofosmin depended on the weight of the tumor and the level of PTH. The early images (15th min) prove to be better than the late ones (120th min). 99mTc-tetrofosmin is washed out more slowly from the thyroid gland than 99mTc-sestamibi but both radionuclides give better results in comparison with 99mTc-pertechnetate/201Tl-substractional technique [56]. 99mTc-tetrofosmin looks promising alternative of 99mTc-sestamibi with similar properties and capabilities of localizing parathyroid adenomas.

Dual-isotope substractional scintigraphy with 99mTc-tetrofosmin/99mTc-pertechnetate and SPECT represent highly sensitive method for localization of parathyroid adenomas and their combination can further improve the diagnostic precision [57]. 99mTc-tetrofosmin, like 99mTc-sestamibi is not perfect for localization of hyperplastic parathyroid glands in patients with SHPT, because of its lower sensitivity [56]. 99mTc-tetrofosmin has some similarities with 99mTc-sestamibi, but its mechanism of accumulation in the cells is different. In contrast with 99mTc-sestamibi, which accumulation depends on mitochondria's membrane potential, retention of 99mTctetrofosmin depends mainly on cell's membrane potential [25]. 99mTc-tetrofosmin, shows slower wash out from the thyroid on the late planar images (120 min). This leads to the necessity to obtain additional later planar images—between 150 and 160 min. This slower wash out makes 99mTc-tetrofosmin to be unsuitable for performing single-isotope, dual-phase scintigraphy [25]. To avoid misleading, because of prolonged retention of the radiopharmaceutical in the thyroid adenomas, an US examination should be performed, especially in iodine deficient areas [56].

**Figure 5** is presented a single-isotope dual-phase scintigraphy with 99mTctetrofosmin, combined with SPECT in a patient with PHPT.

In 99mTc-tetrofosmin scintigraphy early images at 20th min show better quality than the later ones at 120th min (**Figure 6a–c**).

Late planar images (120 min)—negative scan.

#### **Figure 4.**

*Early 99mTc-sestamibi SPECT images showing an area of radionuclide accumulation (arrows), located dorsally and caudally of the left thyroid lobe.*

#### **Figure 5.**

*(a) Early phase image (20 min) shows an intense uptake of the radionuclide at the lower part of the right thyroid lobe, which activity is still present on the late image (120 min) (arrows) and (b) (same patient) SPECT images showing an intense uptake dorsally and caudally of the right thyroid lob (arrow), suggestive for adenoma of the right lower parathyroid gland.*

In this case, early SPECT gives opportunity to visualize adenomas, which were not seen on the late planar images, which is probably due to the rapid wash out of the radiopharmaceutical from some adenomas, as well as to the small sizes of the adenomas. When combined with SPECT, dual-phase scintigraphy with 99mTctetrofosmin can detect adenomas with rapid wash out of the radiopharmaceuticals.

#### **Pearls/pitfalls:**


**55**

**Figure 6.**

*Parathyroid Scintigraphy*

sensitivity.

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

from the thyroid gland.

poor quality of the obtained images and slower washout of the radionuclide

c.SPECT combined with single-isotope scintigraphy and subtractional methods for visualization of hyperfunctioning parathyroid adenomas in patients with PHPT and SHPT is a reliable additional modality. It does not cause additional and unnecessary exposure of the patients to the gamma-rays and can increase

*(a) Single-isotope dual-phase scintigraphy with 99mTc-tetrofosmin. Early planar images (20 min) are with better quality, (b) (same patient) single-isotope dual-phase scintigraphy with 99mTc-tetrofosmin and (c) 99mTctetrofosmin SPECT images—an area (arroes) with high uptake located dorsally of the lower right lobe is seen,* 

*consistent with adenoma of the right lower parathyroid gland.*

*Medical Isotopes*

**54**

**Pearls/pitfalls:**

*adenoma of the right lower parathyroid gland.*

**Figure 5.**

In this case, early SPECT gives opportunity to visualize adenomas, which were not seen on the late planar images, which is probably due to the rapid wash out of the radiopharmaceutical from some adenomas, as well as to the small sizes of the adenomas. When combined with SPECT, dual-phase scintigraphy with 99mTctetrofosmin can detect adenomas with rapid wash out of the radiopharmaceuticals.

*(a) Early phase image (20 min) shows an intense uptake of the radionuclide at the lower part of the right thyroid lobe, which activity is still present on the late image (120 min) (arrows) and (b) (same patient) SPECT images showing an intense uptake dorsally and caudally of the right thyroid lob (arrow), suggestive for* 

a.The single isotope dual-phase scintigraphy with 99mTc-sestamibi or 99mTctetrofosmin could miss parathyroid adenomas with rapid washout of the radionuclide. The combination with early SPECT improves sensitivity.

b.The single isotope dual-phase scintigraphy with 99mTc-tetrofosmin in patients with PHPT and SHPT is with less sensitivity and specificity, because of the

poor quality of the obtained images and slower washout of the radionuclide from the thyroid gland.

c.SPECT combined with single-isotope scintigraphy and subtractional methods for visualization of hyperfunctioning parathyroid adenomas in patients with PHPT and SHPT is a reliable additional modality. It does not cause additional and unnecessary exposure of the patients to the gamma-rays and can increase sensitivity.

*(a) Single-isotope dual-phase scintigraphy with 99mTc-tetrofosmin. Early planar images (20 min) are with better quality, (b) (same patient) single-isotope dual-phase scintigraphy with 99mTc-tetrofosmin and (c) 99mTctetrofosmin SPECT images—an area (arroes) with high uptake located dorsally of the lower right lobe is seen, consistent with adenoma of the right lower parathyroid gland.*
