# Clinical Impact of FDG PET/CT in Pulmonary Nodule Characterization: Current Perspectives on Dual-Time-Point Imaging and Semi-Quantitative Imaging Metrics

## TL;DR

This paper reviews how FDG PET/CT helps distinguish between benign and malignant lung nodules using dual-time imaging and semi-quantitative metrics.

## Contribution

The paper provides a comprehensive review of dual-time-point imaging and semi-quantitative metrics in FDG PET/CT for pulmonary nodule characterization.

## Key findings

- High SUV, MTV, and TLG values are significantly associated with malignant pulmonary nodules.
- Dual-time-point imaging improves diagnostic accuracy by assessing changes in FDG uptake over time.
- Advanced PET/CT parameters show better accuracy in characterizing indeterminate pulmonary nodules.

## Abstract

Pulmonary nodules are frequently detected via conventional imaging, and distinguishing benign from malignant lesions remains a diagnostic challenge. 18F-FDG PET/CT has become a key imaging modality for evaluating these nodules based on their metabolic activity. This review explores the clinical impact of FDG PET/CT in characterizing pulmonary nodules, focusing on dual-time-point imaging and semi-quantitative metrics such as standardized uptake values (SUVs), evolving metrics including metabolic tumor volume (MTV) and total lesion glycolysis (TLG), and future perspectives including artificial intelligence (AI) and PET radiomics. Dual-time-point imaging improves diagnostic accuracy by assessing changes in FDG uptake over time, while semi-quantitative analysis provides measurements to support clinical decision-making. We highlight the current limitations, recent advances, and potential future applications of these techniques in improving diagnostic accuracy.

Background/Objectives: Pulmonary nodules (PNs) are a common incidental finding on conventional imaging. Differentiating benign from malignant lesions remains a diagnostic challenge. 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) has become an essential imaging modality in this setting. This review aims to evaluate the clinical impact of PET/CT parameters and techniques, focusing on semi-quantitative imaging biomarkers and dual-time-point imaging. Methods: This review is organized into three main sections. First, qualitative analysis and PET key metrics are analyzed, including standardized uptake value (SUVmax), metabolic tumor volume (MTV), and total lesion glycolysis (TLG) indices, highlighting their diagnostic and prognostic significance. The second section focuses on the clinical utility of dual-time-point imaging (DTPI), evaluating its ability to differentiate between benign and malignant PNs through changes in SUV over time (ΔSUVmax). We compare these advanced imaging approaches with histopathological diagnosis, the current gold-standard method, highlighting the potential of advanced PET/CT techniques in clinical decision-making. The last section focuses on future applications of PET/MR, artificial intelligence, and PET radiomics. Results: Evidence indicates that high SUV, MTV, and TLG values are significantly associated with malignant PNs and aggressiveness. Moreover, DTPI with ΔSUV, ΔMTV, and ΔTLG further enhances specificity and accuracy in characterizing PNs. Despite a lack of standardization, studies have shown better accuracy when advanced PET/CT parameters are used. Conclusions: While DTPI and semi-quantitative PET parameters are not yet universally adopted in daily clinical practice, evidence supports their role in enhancing the characterization of indeterminate PNs. More prospective studies are needed.