Background/Objectives: This study evaluates the diagnostic accuracy of [18F]fluorodeoxyglucose ([¹⁸F]FDG) positron emission tomography (PET) using bone marrow biopsy (BMB) and clinical follow-up as reference standards. It further identifies predictive factors for bone marrow involvement (BMI) in non-Hodgkin lymphoma (NHL) patients. Methods: NHL patients who underwent [¹⁸F]FDG PET and BMB at diagnosis in a tertiary cancer center were included in this study. Diagnostic accuracy was analyzed, and logistic regression was performed to identify BMI predictors using Stata software version 17. A retrospective analysis of 262 NHL patients was conducted. Results: Concordance rates between [¹⁸F]FDG PET and BMB and between [¹⁸F]FDG PET and clinical follow-up were 75.6% and 88.1%, respectively. The primary cause of discordance between [¹⁸F]FDG PET and BMB was the detection of extra-iliac focal hypermetabolic bone marrow lesions by [¹⁸F]FDG PET, which were negative on BMB. The sensitivity, specificity, and accuracy of [¹⁸F]FDG PET were 62.9%, 80%, and 75.6%, respectively, with BMB as a reference, and 74.1%, 97.5%, and 88.2%, respectively, with clinical follow-up as a reference. The focal bone marrow [¹⁸F]FDG pattern was the most reliable indicator of BMI. Univariate logistic regression showed that advanced NHL stage, elevated alkaline phosphatase, thrombocytopenia, leukopenia, and elevated lactate dehydrogenase were significant predictors of BMI. Multivariate analysis revealed advanced NHL stage and thrombocytopenia as clinical predictors. Conclusions: [¹⁸F]FDG PET is a reliable tool for assessing BMI, providing comprehensive total-body evaluation and identifying extra-iliac involvement beyond the scope of BMB. The collective interpretation of molecular imaging, clinical, and biochemical factors is crucial for predicting BMI.

Glomerular filtration rate (GFR) is a key indicator of renal function. Traditional methods for GFR measurement have limitations including invasiveness, low spatial resolution, and lengthy protocols. Positron emission tomography (PET) radiotracers have emerged as promising tools for non-invasive, accurate, and dynamic renal function assessment. Objectives: This systematic literature review evaluates the clinical utility, and current evidence surrounding PET radiotracers used for GFR measurement in humans, emphasizing advances over conventional renal imaging modalities. Methods: A systematic literature search was conducted in PubMed, Web of Science, and Scopus, following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, from database inception to November 2024. The search identified studies evaluating PET-based measurement of glomerular filtration rate (GFR) and renal perfusion. Inclusion criteria encompassed human studies using PET radiotracers (e.g., ⁶⁸Ga, ¹⁸F) with comparisons to reference standards (estimated GFR or serum creatinine). Two authors independently screened titles/abstracts, extracted data, and assessed bias using Quality Assessment of Diagnostic Accuracy Studies tool (QUADAS-2). Exclusions included animal studies, reviews, and non-English articles. Results: Eleven studies met inclusion criteria, with ⁶⁸Ga-EDTA showing the highest validation against reference standards such as ⁵¹Cr-EDTA plasma clearance, demonstrating strong correlation. PET imaging offered superior spatial–temporal resolution, enabling accurate split renal function assessment and quantitative analysis of both filtration and perfusion. ⁶⁸Ga-somatostatin analogues exhibited moderate correlations between renal SUV and estimated GFR, with post-PRRT uptake changes indicating early nephrotoxicity. Among novel tracers, ⁶⁸Ga-FAPI showed a strong inverse SUV–GFR relationship, reflecting renal fibrosis and suggesting potential as a chronic kidney disease (CKD) biomarker but requires further clinical validation. Limitations across studies include small sample sizes, retrospective designs, and variability in reference standards. Conclusions: PET radiotracers, particularly ⁶⁸Ga-EDTA, represent a significant advancement for non-invasive, quantitative GFR measurement with improved precision and renal anatomical detail compared to traditional methods. Future prospective, large-scale human studies with standardized protocols are needed to establish these PET tracers as routine clinical tools in nephrology. Integration of hybrid PET/MRI and novel tracer development may further enhance renal diagnostic capabilities.