Endocrinology application of molecular imaging: current role of PET/CT

Abstract

Background: In recent years, nuclear medicine imaging methods have proven to be of paramount importance in a wide variety of diseases, particularly in oncology, where they are crucial for assessing the extent of disease when conventional methods fall short. Moreover, nuclear imaging modalities are able to better characterize lesions using target agents related to specific pathways (e.g. glucose metabolism, cellular proliferation, amino acid transport, lipid metabolism, specific receptor ligands). The clinical presentation of endocrine diseases encompasses a broad spectrum of sign and symptoms. Moreover, endocrine tumors show varying degrees of aggressiveness from well differentiated and indolent to highly aggressive cancers, respectively.

Rationale: With the application of new medicinal radio-compounds and increasingly advanced tomographic imaging technology, the utility of Positron Emission Tomography/Computed Tomography (PET/CT) in the field of endocrine diseases is expanding.

Aim: This review aims to analyze and summarize the primary indications of PET/CT, providing a practical approach for clinicians. A comprehensive literature search on PubMed was conducted to provide an updated overview of the available evidence regarding the use of PET/CT in endocrinology. Within this review, we will discuss the applications of PET/CT, compare different radiopharmaceuticals and highlight the uptake mechanism, excluding neuroendocrine carcinomas from discussion.

Conclusions: PET/CT is a valuable tool in diagnosing and managing endocrine disorders due to its capacity to furnish both functional and anatomical information, facilitate early lesion detection, guide treatment decisions, and monitor treatment response. Its non-invasive nature and precision make it an integral component of modern endocrine healthcare. This review aims to provide physicians with a clear perspective on the role of PET/CT imaging, discussing its emerging opportunities and appropriateness of use in endocrinological diseases.

Keywords: 2-[18F]FDG; 6-[18F]FDOPA; Endocrine tumors; PET/CT; [11C]Choline; [18F]F-choline; [C1-11C]Methionine.

Fig. 1

¹²⁴I PET/CT of 63 yo woman with DTC after total thyroidectomy and RAI: (A) maximum Intensity Projection (MIP) multiple metastatic findings in the lung and upper mediastinum; axial images show metastatic lymph node in the upper mediastinum (B), multiple bilateral lung metastases (C–D) and a 3 cm solid mass in the right hilum of the lung (D); E 131-iodine scintigraphy findings after the second radioactive iodine (RAI) treatment: 131-iodine has accumulated in the metastatic tumor in the lungs and in the mediastinal lymph node

Fig. 2

[¹⁸F]FDOPA PET/CT preoperative staging in a 61 y.o. woman with hypercalcitonemia and mild elevation of serum CEA, showing focal uptake in thyroid nodule in the right lobe; no evidence of pathological lymph nodes. A MTC was diagnosed after total thyroidectomy

Fig. 3

Preoperative staging with [¹⁸F]F FDG PET/CT(A1) in a 32-year-old patient with a finding of a voluminous left adrenal mass: (A2) axial PET/CT images show an intense and inhomogeneous uptake in the adrenal mass and in some lumbar aortic lymph nodes; after left nephrectosurrenectomy and left lymphadenectomy, a diagnosis of high-grade ACC was made. B At follow-up PET scan, during mitotane therapy, was found a peritoneal carcinosis

Fig. 4

A Double tracer ^99mTc-sestamibi and ^99mTc pertechnetate in 71-year-old patient with primary HPT (PTH 226 pg/ml) and no evidence of enlarged parathyroid on ultrasonography and 4D CT; B SPECT/CT shows no findings likely to be an adenomatous parathyroid. C–D [¹⁸F]F-choline PET/CT MIP and axial images show the presence of small area of focal hyperfixation at the left upper parathyroid