Use of 99mTc-sestamibi SPECT/CT imaging in predicting the degree of pathological hyperplasia of the parathyroid gland: semi-quantitative analysis

Abstract

Background: Previous studies have demonstrated that ^99mTc-sestamibi (^99mTc-MIBI) Single-Photon Emission Computed Tomography/ Computed Tomography (SPECT/CT) imaging is an effective isotopic technique for locating the parathyroid in secondary hyperparathyroidism (SHPT). This study aimed to explore further the correlation between ^99mTc-MIBI SPECT/CT imaging and SHPT to demonstrate the value of ^99mTc-MIBI SPECT/CT in evaluating the degree of pathological hyperplasia of the parathyroid gland (PG).

Methods: The demographics, surgical records, and follow-up information of 91 patients were recorded and analyzed. A total of 216 paraffin-embedded PGs of 54 patients were obtained and analyzed.

Results: Patients with ^99mTc-MIBI negative PG(s) had significantly lower preoperative serum phosphorus and higher serum calcium levels at 6 months postoperatively compared to those with ^99mTc-MIBI positive PG(s) (P<0.05). We also found a higher total uptake ratio of the region of interest (URRI) and higher URRI max in the hypocalcemia group than in the non-hypocalcemia group. Both URRI total (P=0.003) and URRI max (P=0.028) were independent risk factors for hypocalcemia 6 months postoperatively. The URRI values of the PGs were significantly positively correlated with glandular weight (R²=0.343, P<0.001), glandular volume (R²=0.240, P<0.001), and degree of pathological hyperplasia (P<0.001). However, the URRI value of the PGs exhibited a notably weak correlation with proliferating cell nuclear antigen (PCNA) (R²=0.035, P=0.006). The area under the receiver operating characteristic curve showed a URRI evaluative value of 0.771 for diffuse and nodular types in 216 PGs (P<0.001). We further evaluated 167 nodular-type PGs, distinguishing between nodular hyperplasia and a single nodule; the URRI evaluative value reached 0.819, which was higher than the volume or weight (P<0.001).

Conclusions: The ^99mTc-MIBI SPECT/CT scintigraphy results were related to serum calcium levels at 6 months after total parathyroidectomy with autotransplantation (TPTX+AT), suggesting the occurrence of hypocalcemia (6 months after TPTX+AT). More importantly, this technique effectively evaluated the pathological hyperplasia of PGs preoperatively, and therefore, could assist surgeons in selecting the PGs with the lowest degree of hyperplasia intraoperatively.

Keywords: 99mTc-MIBI; hyperplasia; hypocalcemia; parathyroid gland; secondary hyperparathyroidism.

Figure 1

Axial CT (A,C,E,G) and SPECT/CT (B,D,F,H) showed four lesions in the back of the thyroid gland that were pathologically confirmed to be parathyroid hyperplasia (A,B: superior left parathyroid gland; C,D: inferior left parathyroid gland; E,F: superior right parathyroid gland; G,H: inferior right parathyroid gland). The early and delayed phase planar images (I,J) showed ^99mTc-MIBI uptake of the thyroid lobe and parathyroid gland.

Figure 2

Axial CT (A,C,E,G) and SPECT/CT (B,D,F,H) showed four lesions in the back of the thyroid gland that were pathologically conformed to be parathyroid hyperplasia (A,B: superior left parathyroid gland, URRI =2.35; C,D: inferior left parathyroid gland, URRI =0.59; E,F: superior right parathyroid gland, URRI =8.03; G,H: inferior right parathyroid gland, URRI =3.62). The planar images (I) showed different ^99mTc-MIBI uptake of the parathyroid glands in a patient. URRI, uptake ratio of region of interest.

Figure 3

An example of PCNA staining (IHC) for different URRIs and degrees of pathological hyperplasia in different parathyroid glands of a patient. URRI, uptake ratio of region of interest; PCNA, proliferating cell nuclear antigen.

Figure 4

The relationship between the value of parathyroid URRI and glandular weight (A), glandular volume (B), PCNA (C), and pathological hyperplasia of PG (D). URRI, uptake ratio of region of interest; PCNA, proliferating cell nuclear antigen.

Figure 5

ROC curves demonstrating (A) the accuracy of volume, URRI, weight, and location as predictors of diffuse and nodular types in 216 parathyroid glands, and (B) the accuracy of volume, URRI, weight, and location as predictors of nodular hyperplasia and single nodule in 167 parathyroid glands with nodular-type. URRI, uptake ratio of region of interest.