PET/CT and PET/MRI in ophthalmic oncology (Review)

Abstract

Orbital and ocular anatomy is quite complex, consisting of several tissues, which can give rise to both benign and malignant tumors, while several primary neoplasms can metastasize to the orbital and ocular space. Early detection, accurate staging and re-staging, efficient monitoring of treat-ment response, non-invasive differentiation between benign and malignant lesions, and accurate planning of external radiation treatment, are of utmost importance for the optimal and individualized management of ophthalmic oncology patients. Addressing these challenges requires the employment of several diagnostic imaging techniques, such as high-definition digital fundus photography, ultrasound imaging, optical coherence tomography, optical coherence tomography (OCT)-angiography, computed tomography (CT) and magnetic resonance imaging (MRI). In recent years, technological advances have enabled the development of hybrid positron emission tomography (PET)/CT and PET/MRI systems, setting new standards in cancer diagnosis and treatment. The capability of simultaneously targeting several cancer-related biochemical procedures using positron emitting-radiopharmaceuticals, while morphologically characterizing lesions by CT or MRI, together with the intrinsic quantitative capabilities of PET-imaging, provide incremental diagnostic information, enabling accurate, highly efficient and personalized treatment strategies. Aim of the current review is to discuss the current applications of hybrid PET/CT and PET/MRI imaging in the management of patients presenting with the most commonly encountered orbital and ocular tumors.

New Perspectives in Imaging of Uveal Melanoma

“…Correlation between positive PET/CT imaging and increasing tumor size along with chromosome 3 loss was also described by Papastefanou et al [177].High SUV value was found in older patients with lesions presenting larger diameters linked to poor prognosis and greater metastatic risk [174]. According to those findings, PET/CT seems to be a useful tool for predictive purposes, but not for primary tumor diagnosis, as if it may not be able to detect small uveal melanomas or differentiate them from uveal nevi [167,173].…”

“…Positron emission tomography is a diagnostic imaging technique that visualizes areas based on their affinity and biodistribution of administered radiotracers [167]. After administering radiopharmaceutical is distributed in the tissue, it emits a positron that interacts with an electron, creating two photons emitted in virtually opposites directions.…”

“…This interaction is detected and estimated within a ring of detectors placed around the patient [168]. It allows visualization as well as the quantification of said biodistribution in a three-dimensional reconstruction [167]. PET cameras can provide images with a spatial resolution of around 2.4mm full width at half maximum (FWHM) [169].…”

“…We have found no studies on PET/MRI applicability in ophthalmic oncology. However, great soft-tissue contrast and functional MRI sequences combined with a functional element of PET can provide accurate tumor information at the time of diagnosis and in therapy response evaluation in regions with complex anatomy such as ocular space [167]. Low radiation dose is another advantage, and it suggests using this modality while searching for liver metastases or in follow-up imaging.…”

Imaging of Uveal Melanoma—Current Standard and Methods in Development

“…Positron emission tomography is a diagnostic imaging technique that visualizes areas based on their affinity and biodistribution of administered radiotracers [184]. After administering a radiopharmaceutical, IT is distributed in the tissue, emits a positron that interacts with an electron, and creates two photons emitted in virtually opposite directions [185].…”