PT - JOURNAL ARTICLE AU - William Raynor AU - Ali Gholamrezanezhad AU - Austin Borja AU - Donald Detchou AU - Raheleh Taghvaei AU - Thomas Werner AU - Mona-Elisabeth Revheim AU - Abass Alavi TI - Musculoskeletal applications of PET-based quantitative techniques DP - 2021 May 01 TA - Journal of Nuclear Medicine PG - 2006--2006 VI - 62 IP - supplement 1 4099 - http://jnm.snmjournals.org/content/62/supplement_1/2006.short 4100 - http://jnm.snmjournals.org/content/62/supplement_1/2006.full SO - J Nucl Med2021 May 01; 62 AB - 2006Objectives: 1. Review PET tracers and their applications in musculoskeletal disorders. 2. Introduce quantitative and semi-quantitative methods of assessing musculoskeletal involvement by PET. Methods: Molecular imaging with PET provides unique insights into molecular phenomena that precede macroscopic changes such as the presence of inflammatory cells shown by 18F-fluorodeoxyglucose (FDG) and the presence of bone formation by 18F-sodium fluoride (NaF). Certain inflammatory musculoskeletal conditions such as rheumatoid arthritis have primarily been assessed by FDG-PET, while others such as ankylosing spondylitis have been found to demonstrate both FDG and NaF uptake at involved areas. Quantitative parameters in these diseases can assist in diagnosis, assessment over time, and determining the efficacy of intervention. Metabolic bone diseases such as osteoporosis and osteopenia, which are primarily assessed by bone mineral density, represent a logical application of PET-based assessment of bone turnover using NaF. As part of a diffuse, systemic process, osteoporosis and osteopenia result in subtle changes in NaF uptake and therefore require a quantitative rather than qualitative method of analysis and interpretation. Results: In contrast to anatomical modalities such as MRI and computed tomography (CT), the interpretations of which are primarily qualitative, PET and its hybrid modalities contain straightforward quantitative methods that can guide clinical decision making. Although quantification based on dynamic PET imaging is considered the most accurate, it is limited to a single region of interest and not practical in the clinical setting. Quantitative NaF-PET studies rely on a three-compartment model consisting of plasma, bone extracellular fluid, and bone mineral, with the clearance of tracer from plasma to bone mineral represented as Ki. Investigators have found that Ki and rate constants between compartments can be used to diagnose osteoporosis and show effects of therapy. Semi-quantitative techniques can be performed with a significantly simpler static imaging protocol while compromising little accuracy. The standardized uptake value (SUV) is a semi-quantitative PET parameter that represents tracer uptake normalized to injected dose and either patient body weight or surface area. While the maximum SUV is easily determined, automated segmentation methods have made calculating the mean SUV a possibility. Furthermore, global assessment by multiplying uptake values by volumes of individual lesions can determine total disease activity in inflammatory and infectious disorders. Partial volume correction is also feasible, resulting in higher uptake in smaller lesions susceptible to the partial volume effect. Conclusions: A major advantage of PET imaging is the availability and utility of quantitative parameters that can be applied to musculoskeletal disorders that involve infection, joint inflammation, bone destruction, and abnormal bone turnover. Semi-quantitative metrics are practical and highly useful in determining disease activity, and implementation of global assessment and partial volume correction represents superior evaluation of overall disease status.