18F-Sodium Fluoride PET as a Diagnostic Modality for Metabolic, Autoimmune, and Osteogenic Bone Disorders: Cellular Mechanisms and Clinical Applications.

In a healthy body, homeostatic actions of osteoclasts and osteoblasts maintain the integrity of the skeletal system. When cellular activities of osteoclasts and osteoblasts become abnormal, pathological bone conditions, such as osteoporosis, can occur. Traditional imaging modalities, such as radiographs, are insensitive to the early cellular changes that precede gross pathological findings, often leading to delayed disease diagnoses and suboptimal therapeutic strategies. 18F-sodium fluoride (18F-NaF)-positron emission tomography (PET) is an emerging imaging modality with the potential for early diagnosis and monitoring of bone diseases through the detection of subtle metabolic changes. Specifically, the dissociated 18F- is incorporated into hydroxyapatite, and its uptake reflects osteoblastic activity and bone perfusion, allowing for the quantification of bone turnover. While 18F-NaF-PET has traditionally been used to detect metastatic bone disease, recent literature corroborates the use of 18F-NaF-PET in benign osseous conditions as well. In this review, we discuss the cellular mechanisms of 18F-NaF-PET and examine recent findings on its clinical application in diverse metabolic, autoimmune, and osteogenic bone disorders.

Comparison of 18F-sodium fluoride uptake in the whole bone, pelvis, and femoral neck of multiple myeloma patients before and after high-dose therapy and conventional-dose chemotherapy.

AIM: To compare the effects of high-dose therapy (HDT consisting of high-dose chemotherapy followed by autologous stem cell transplantation) and conventional-dose chemotherapy (non-HDT) on the uptake of 18F-sodium fluoride (NaF) in the whole bone, pelvis, and femoral neck of multiple myeloma (MM) patients. METHOD: The data of 19 MM patients who received HDT (61.5 (SD 5.6) years) and 11 MM patients who received conventional-dose chemotherapy (70.9 (SD 7.2) years) were collected in a prospective study. NaF PET/CT imaging was performed at baseline, and 8 weeks and 2 weeks after treatment for the HDT group and the non-HDT group, respectively. A CT-based algorithm was applied to segment the bones, and the global mean SUV (GSUVmean) of the whole bone and pelvis was calculated (OsiriX MD v.9.0, Pixmeo SARL; Bernex, Switzerland). In addition, regions of interest for the whole, medial, and lateral femoral neck were delineated bilaterally. Whole bone and pelvis measurements were replicated by two observers. RESULTS: The average GSUVmean in the whole bone and pelvis of the patients who underwent HDT significantly decreased from before to after treatment (- 16.27%, p = 0.02 and - 16.54%, p = 0.01, respectively). A significant decrease in the whole and lateral femoral neck was also observed bilaterally in the HDT group. No significant decrease in average GSUVmean was observed in the non-HDT group. A high level of inter-observer reliability was found in intra-class correlation (ICC for pre-treatment whole bone 0.983, post-treatment whole bone 0.989, pre-treatment whole pelvis 0.998, post-treatment whole pelvis 0.996). CONCLUSION: NaF uptake significantly decreased after treatment in patients who received high-dose therapy. A high level of agreement was observed between two operators for whole bone and pelvis measurements.

Association between age, uptake of 18F-fluorodeoxyglucose and of 18F-sodium fluoride, as cardiovascular risk factors in the abdominal aorta.

OBJECTIVE: We aimed to assess the feasibility of quantifying fluorine-18-fluorodexoglucose (18F-FDG) and 18F-sodium fluoride (18F-NaF) uptake in abdominal aorta and examine their association with age and cardiovascular risk factors. SUBJECTS AND METHODS: Our study comprised 123 subjects (48±14 years of age, 62 men) including 78 healthy volunteers and 45 patients with chest pain syndrome, who originally enrolled in the CAMONA study in Odense, Denmark (NCT01724749). All subjects underwent 18F-FDG positron emission tomography/computed tomography (PET/CT) and 18F-NaF PET/CT on separate days, 180min and 90min after administration of tracers, respectively. The global tracer uptake value (GTUV) in the abdominal aorta was determined as sum of the product of each slice area and its corresponding average standardized uptake value (SUV mean), divided by the sum of those slice areas. In addition, for each subject, the 10 years Framingham risk score (FRS) was calculated. The correlations between 18F-NaF and 18F-FDG GTUV with age and 10 years FRS were assessed in all, healthy and patient subjects. RESULTS: There was a significant, positive correlation between subjects' age and 18F-NaF GTUV (r=0.35, P<0.001), but not 18F-FDG GTUV (r=0.06, P=0.53). Also, there was a significant, positive correlation between 10 years FRS and 18F-NaF GTUV (r=0.30, P<0.001), but not 18F-FDG GTUV (r=0.01, P=0.95). Individual differences in 18F-FDG and 118F-NaF uptake were large in both healthy subjects and patients. CONCLUSION: In this study, the global uptake of 18F-NaF in abdominal aorta was positively associated with age and 10 years FRS in all subjects, healthy and patient groups, whereas the global uptake of 18F-FDG was not.

Role of PET/CT in diagnosing and monitoring disease activity in rheumatoid arthritis: a review.

Rheumatoid Arthritis (RA) is a systemic inflammatory disorder that commonly presents with polyarthritis but can have multisystemic involvement and complications, leading to increased morbidity and mortality. The diagnosis of RA continues to be challenging due to its varied clinical presentations. In this review article, we aim to determine the potential of PET/CT to assist in the diagnosis of RA and its complications, evaluate the therapeutic response to treatment, and predict RA remission. PET/CT has increasingly been used in the last decade to diagnose, monitor treatment response, predict remissions, and diagnose subclinical complications in RA. PET imaging with [18F]-fluorodeoxyglucose ([18F]-FDG) is the most commonly applied radiotracer in RA, but other tracers are also being studied. PET/CT with [18F]-FDG, [18F]-NaF, and other tracers might lead to early identification of RA and timely evidence-based clinical management, decreasing morbidity and mortality. Although PET/CT has been evolving as a promising tool for evaluating and managing RA, more evidence is required before incorporating PET/CT in the standard clinical management of RA.

Predicting the Efficacy of SBRT for Lung Cancer with 18F-FDG PET/CT Radiogenomics.

PURPOSE: to develop a radiogenomic model on the basis of 18F-FDG PET/CT radiomics and clinical-parameter EGFR for predicting PFS stratification in lung-cancer patients after SBRT treatment. METHODS: A total of 123 patients with lung cancer who had undergone 18F-FDG PET/CT examination before SBRT from September 2014 to December 2021 were retrospectively analyzed. All patients' PET/CT images were manually segmented, and the radiomic features were extracted. LASSO regression was used to select radiomic features. Logistic regression analysis was used to screen clinical features to establish the clinical EGFR model, and a radiogenomic model was constructed by combining radiomics and clinical EGFR. We used the receiver operating characteristic curve and calibration curve to assess the efficacy of the models. The decision curve and influence curve analysis were used to evaluate the clinical value of the models. The bootstrap method was used to validate the radiogenomic model, and the mean AUC was calculated to assess the model. RESULTS: A total of 2042 radiomics features were extracted. Five radiomic features were related to the PFS stratification of lung-cancer patients with SBRT. T-stage and overall stages (TNM) were independent factors for predicting PFS stratification. AUCs under the ROC curve of the radiomics, clinical EGFR, and radiogenomic models were 0.84, 0.67, and 0.86, respectively. The calibration curve shows that the predicted value of the radiogenomic model was in good agreement with the actual value. The decision and influence curve showed that the model had high clinical application values. After Bootstrap validation, the mean AUC of the radiogenomic model was 0.850(95%CI 0.849-0.851). CONCLUSIONS: The radiogenomic model based on 18F-FDG PET/CT radiomics and clinical EGFR has good application value in predicting the PFS stratification of lung-cancer patients after SBRT treatment.

18F-FDG and 18F-NaF PET/CT Global Assessment of Large Joint Inflammation and Bone Turnover in Rheumatoid Arthritis.

Rheumatoid arthritis (RA) involves chronic inflammation of synovial joints, causing pain, stiffness, and limited mobility. 18F-sodium fluoride (NaF) is a PET tracer whose uptake reflects bone turnover, while 18F-fludeoxyglucose (FDG) shows glucose metabolism and can serve as a marker for inflammation. The aim of this study is to determine the feasibility of calculating the FDG and NaF mean standardized uptake value (SUVmean) in the knee joint, hip joint, and sacroiliac (SI) joint of RA patients and to determine their association with patient characteristics. Prospective FDG-PET/CT as well as NaF-PET/CT imaging was performed on 18 RA patients. The global SUVmean was calculated on FDG-PET/CT and NaF-PET/CT images using a semiautomated CT-based method of segmentation. FDG and NaF uptake were found to be significantly correlated in the knee (r = 0.77, p < 0.001), but not in the hip and SI joints. In the knee, both NaF SUVmean and FDG SUVmean were significantly correlated with body weight, BMI, leptin, and sclerostin levels (p < 0.05). NaF SUVmean was significantly positively correlated with BMI and leptin for both the hip and SI joints (p < 0.05). No significant correlation was observed between either PET parameter and age, height, erythrocyte sedimentation rate (ESR), and interleukins 1 and 6 (IL-1 and IL-6); however, FDG was correlated with inflammatory markers such as C-reactive protein (CRP) and patient global visual analogue scale (VAS-PtGlobal) in some joints. In this study, both FDG and NaF uptake were quantified in large joints of patients with RA using CT segmentation. NaF and FDG SUVmean were correlated with clinical variables related to body weight and adiposity, suggesting that degenerative joint disease may play a larger role in influencing the uptake of these tracers in large joints than RA disease activity. FDG and its correlation with markers of inflammation such as CRP and VAS-PtGlobal suggests that this tracer may serve as a more specific marker for RA disease activity than NaF. Larger prospective and longitudinal data are necessary to gain a better understanding of the roles of FDG and NaF in evaluating RA joint activity in these joints.

Atherosclerosis Imaging: Positron Emission Tomography.

Assessment of molecular changes by PET has introduced a new paradigm in atherosclerosis imaging, which has traditionally relied on anatomic changes visualized by conventional angiography or computed tomography. The use of 18F-fluorodeoxyglucose (FDG) to identify atherosclerotic changes in the vessel wall was first described more than 2 decades ago. Since then, PET tracers targeting macrophage activity, neoangiogenesis, smooth muscle activity, and other aspects of atherogenic changes have been proposed. The evolving roles of PET tracers including frontrunners FDG and 18F-sodium fluoride, which show arterial wall inflammation and microcalcification, respectively, are discussed.

Is Imaging Bacteria with PET a Realistic Option or an Illusion?

The application of [18F]-fluorodeoxyglucose ([18F]FDG) as a radiotracer to detect sites of inflammation (either due to bacterial infection or primary inflammation) has led to exploring the role of PET in visualizing bacteria directly at sites of infection. However, the results from such efforts are controversial and inconclusive so far. We aimed to assess the limitations of PET as an effective modality in the diagnosis of bacterial infections. Inflammation due to bacterial infections can be visualized by using [18F]FDG-PET. However, the non-specificity of [18F]FDG makes it undesirable to visualize bacteria as the underlying cause of inflammation. Hence, more specific radiotracers that possibly bind to or accumulate in bacteria-specific receptors or enzymes are being explored. Several radiotracers, including 2-deoxy-2-[18F]fluorosorbitol ([18F]FDS), 6-[18F]-fluoromaltose, [11C]para-aminobenzoic acid ([11C]PABA), radiolabeled trimethoprim (11C-TMP) and its analog fluoropropyl-trimethoprim (18F-FPTMP), other radiolabeled sugars, and antimicrobial drugs have been used to image microorganisms. Unfortunately, no progress has been made in translating the results to routine human use; feasibility and other factors have constrained their success in clinical settings. In the current article, we discuss the limitations of direct bacterial visualization with PET tracers, but emphasize the important role of [18F]FDG-PET as the only option for detecting evidence of infection.

The Utility of 18 F-NaF-Positron Emission Tomography/Computed Tomography in Measuring the Metabolic Activity of the Aging Spine : Implications for Osteoporosis.

STUDY DESIGN: Cross-sectional; observational. OBJECTIVES: To determine whether sodium fluoride (NaF) positron emission tomography/computed tomography (PET/CT) can be used to monitor decreased bone turnover with aging in the spine. BACKGROUND: Osteoporosis is characterized by structural changes in the bone such as decreased bone mineral density leading to an increased risk for fractures. An imaging modality capable of identifying molecular changes that precede these structural changes could be critical for the early diagnosis and monitoring of osteoporosis and other metabolic bone disorders. MATERIALS AND METHODS: The potential of 18 F-sodium fluoride (NaF)-PET/CT in detecting changes in bone turnover associated with aging was examined in the lumbar spine of 88 healthy volunteers (43 females, 45 males; mean age 44.6 yr). Regions of interest equal to the trabecular body of the L1 to L4 vertebrae were used to calculate the mean standardized uptake value (SUVmean) and average Hounsfield unit (HU) values. Receiver-operating characteristic curve analysis with an area under the curve using the Wilson/Brown method was generated to assess the value of NaF uptake (SUVmean) in predicting osteoporosis as defined by HU-threshold values. To determine the correlation among global SUVmean, mean HU values, and age, the Spearman correlation test was performed on images acquired at 90 minutes postinjection. RESULTS: There was a significant negative correlation between NaF SUVmean and age in females ( P < 0.0001, r = -0.59), and a weaker, but also significant correlation in males ( P = 0.03, r = -0.32). In females only, there was a significant correlation between NaF uptake and age at all acquisition time points. Measured NaF uptake increased by 10% to 15% with acquisition time in both sexes, from 45 to 90 minutes and from 90 to 180 minutes. CONCLUSIONS: NaF-PET/CT detects decreased vertebral bone turnover with aging, particularly in females. Measured NaF uptake increased with PET acquisition time after tracer injection, which must be considered in follow-up studies monitoring disease development and treatment effects.

State of the Art Imaging of Osteoporosis.

Osteoporosis is a common disease, particularly prevalent in geriatric populations, which causes significant worldwide morbidity due to increased bone fragility and fracture risk. Currently, the gold-standard modality for diagnosis and evaluation of osteoporosis progression and treatment relies on dual-energy x-ray absorptiometry (DXA), which measures bone mineral density (BMD) and calculates a score based upon standard deviation of measured BMD from the mean. However, other imaging modalities can also be used to evaluate osteoporosis. Here, we review historical as well as current research into development of new imaging modalities that can provide more nuanced or opportunistic analyses of bone quality, turnover, and density that can be helpful in triaging severity and determining treatment success in osteoporosis. We discuss the use of opportunistic computed tomography (CT) scans, as well as the use of quantitative CT to help determine fracture risk and perform more detailed bone quality analysis than would be allowed by DXA . Within magnetic resonance imaging (MRI), new developments include the use of advanced MRI techniques such as quantitative susceptibility mapping (QSM), magnetic resonance spectroscopy, and chemical shift encoding-based water-fat MRI (CSE-MRI) to enable clinicians improved assessment of nonmineralized bone compartments as well as a way to longitudinally assess bone quality without the repeated exposure to ionizing radiation. Within ultrasound, development of quantitative ultrasound shows promise particularly in future low-cost, broadly available screening tools. We focus primarily on historical and recent developments within radiotracer use as applicable to osteoporosis, particularly in the use of hybrid methods such as NaF-PET/CT, wherein patients with osteoporosis show reduced uptake of radiotracers such as NaF. Use of radiotracers may provide clinicians with even earlier detection windows for osteoporosis than would traditional biomarkers. Given the metabolic nature of this disease, current investigation into the role molecular imaging can play in the prediction of this disease as well as in replacing invasive diagnostic procedures shows particular promise.

Novel technique of detecting inflammatory and osseous changes in the glenohumeral joint associated with patient age and weight using FDG- and NaF-PET imaging.

OBJECTIVE: The glenohumeral (GH) joint is a classic ball-and-socket joint of the shoulder subject to various pathologies including osteoarthritis (OA). Degenerative changes of the OA evident on traditional imaging are proceeded by molecular changes, which if detected early could enhance disease prevention and treatment. In this study, we use 18F-FluoroDeoxyGlucose (FDG) and 18F-sodium-fluoride (NaF)-PET/CT to investigate the effects limb laterality, age, and BMI on the inflammation and bone turnover of the GH shoulder joint. METHODS: FDG and NaF-PET/CT scans of 41 females (mean age of 43.9 ± 14.2 years) and 45 males (mean age of 44.5 ± 13.8 years) were analyzed with a semi-quantitative technique based on predefined region of interest. RESULTS: There was greater FDG uptake in the left side of the GH joint compared to the right in both females (left: 0.79 ± 0.17, right: 0.71 ± 0.2; P < 0.0001) and males (left: 0.76 ± 0.19, right: 0.57 ± 0.18; P < 0.0001). We also observed a strong positive association between BMI and FDG uptakes in females (left: P < 0.0001, r = 0.71, right: P < 0.0001, r = 0.58) and males (left: P < 0.0001, r = 0.56, right: P < 0.0001, r = 0.64). Association between BMI and NaF uptake were found in males as well (left: P = 0.004, r = 0.42, right: P = 0.02, r = 0.35). CONCLUSION: Our study demonstrates the varying effect of limb laterality and BMI on FDG and NaF uptake at the GH joint. Adoption of molecular imaging will require future studies that correlate tracer uptake with relevant medical and illness history as well as degenerative change evident on traditional imaging.

Emerging PET Tracers in Cardiac Molecular Imaging.

18F-fluorodeoxyglucose (FDG) and 18F-sodium fluoride (NaF) represent emerging PET tracers used to assess atherosclerosis-related inflammation and molecular calcification, respectively. By localizing to sites with high glucose utilization, FDG has been used to assess myocardial viability for decades, and its role in evaluating cardiac sarcoidosis has come to represent a major application. In addition to determining late-stage changes such as loss of perfusion or viability, by targeting mechanisms present in atherosclerosis, PET-based techniques have the ability to characterize atherogenesis in the early stages to guide intervention. Although it was once thought that FDG would be a reliable indicator of ongoing plaque formation, micro-calcification as portrayed by NaF-PET/CT appears to be a superior method of monitoring disease progression. PET imaging with NaF has the additional advantage of being able to determine abnormal uptake due to coronary artery disease, which is obscured by physiologic myocardial activity on FDG-PET/CT. In this review, we discuss the evolving roles of FDG, NaF, and other PET tracers in cardiac molecular imaging.

A review of different methods used for quantification and assessment of FDG-PET/CT in multiple myeloma.

The quantification of positron emission tomography/computed tomography (PET/CT) in multiple myeloma (MM) is challenging. Different methods of PET/CT quantification for assessment of fluorodeoxyglucose (FDG) uptake in myeloma patients have been suggested. This is the first review article that focuses on the advantages and disadvantages of each approach. Use of the maximum standardized uptake value (SUVmax) showed some promise in prognostic stratification of MM patients. However, it is affected by noise and time of flight and is subject to high variability. Volumetric PET metrics such as total lesion glycolysis and metabolic tumor volume are other proposed approaches. The high number of osteolytic lesions in MM patients makes this approach difficult in clinical practice. In addition, evaluation of small focal lesions is subject to partial volume correction. CT-based segmentation for assessment of FDG radiotracer is recently introduced. The methodologies are highly reproducible, but the clinical values of the approaches are unclear and still under investigation. We also discuss the Italian Myeloma criteria for PET Use (IMPeTUs), which is a qualitative approach, as a point of comparison. The reproducibility of IMPeTUs depends heavily on the level of user experience. We recommend further studies for assessing the prognostic significance of CT-threshold approaches in the assessment of MM patients.

The effects of limb laterality and age on the inflammation and bone turnover of the acromioclavicular shoulder joint: 18 F-fluorodeoxyglucose and 18 F-sodium-fluoride-PET/computed tomography study.

PURPOSE: The acromioclavicular (AC) joint is a common site of injury and degenerative changes such as osteoarthritis (OA) of the shoulder. Physical manifestations of OA are preceded by molecular changes, detection of which may enhance early prophylaxis and monitoring of disease progression. In this study, we investigate the use of 18 F-FDG and 18 F-NaF-PET/CT to assess the effects of limb laterality and age on the inflammation and bone turnover of the AC shoulder joint. METHODS: We analyzed FDG and NaF-PET/CT scans of 41 females (mean age of 43.9 ± 14.2 years) and 45 males (mean age of 44.5 ± 13.8 years) using a semiquantitative technique based on predefined ROI. RESULTS: There was a greater NaF uptake in the right side of the AC joint compared with the left in both females (left: 2.22 ± 1.00; right: 3.08 ± 1.18; P < 0.0001) and males (left: 2.57 ± 1.49; right: 2.99 ± 1.40; P = 0.003). No consistent correlation between age and NaF or FDG uptakes were found in both females and males. There was also a positive correlation between FDG and NaF uptakes in both left ( P = 0.01; r = 0.37) and right ( P = 0.0006; r = 0.53) AC joints of male subjects. CONCLUSION: Our study is the first to reveal the varying effect of right-left limb laterality and aging on FDG and NaF uptake at the AC joint. Future studies correlating the history of shoulder trauma, pain, and degenerative change with FDG and NaF-PET/CT findings will be critical in the adoption of molecular imaging in the clinical setting.

Application of 18F-NaF-PET/CT in assessing age-related changes in the cervical spine.

Background: Cervical spondylosis is the degeneration of cervical spine often associated with aging and neck pain. As the degenerative changes are coupled with altered osteoblastic activity, imaging modalities sensitive to such molecular changes could be valuable for clinical assessment, disease prophylaxis, and monitoring early therapy response. In this study, we examined the role of 18F-sodium fluoride-positron emission tomography/computed tomography (18F-NaF-PET/CT) in detecting age-associated changes in the cervical spine of an adult population with broad age spectrum. Methods: In this retrospective cross-sectional study, we analyzed 18F-NaF-PET/CT scans of 88 control volunteers (43 females, 45 males) with age ranging from 21 to 75 years (mean =44.6, standard deviation, 14.0) divided into younger (21-45 years) and older (46-75 years) age groups. A semi-automated global assessment technique was used to measure 18F-NaF uptake in C2-C4 and C5-C7 vertebrae of the subjects. Furthermore, a CT-based scoring system was devised to measure the degree of structural degeneration. Results: There was a significant difference in 18F-NaF uptake of the younger and older groups at the C5-C7 vertebrae for both females (younger: mean =4.13, 95% CI: 3.72-4.55; older: mean = 4.80, 95% CI: 4.40-5.20; P=0.005) and males (younger: mean =3.66, 95% CI: 3.24-4.09; older: mean =4.22, 95% CI: 3.80-4.64; P=0.009), but not at the C2-C4 vertebrae. Furthermore, there was a positive correlation between the degree of degeneration and 18F-NaF uptake at both C2-C4 and C5-C7 spinal segments of both sexes. Conclusions: Aging is associated with increased 18F-NaF uptake in the cervical spine, which may be associated with osteoblastic activity coupled with degeneration. Our study alludes to the potential role of 18F-NaF-PET/CT in evaluating age-related degeneration and osteoarthritis of the spine.

Role of Molecular Imaging with PET/MR Imaging in the Diagnosis and Management of Brain Tumors.

Gliomas are the most common primary brain tumors. Hybrid PET/MR imaging has revolutionized brain tumor imaging, allowing for noninvasive, simultaneous assessment of morphologic, functional, metabolic, and molecular parameters within the brain. Molecular information obtained from PET imaging may aid in the detection, classification, prognostication, and therapeutic decision making for gliomas. 18F-fluorodeoxyglucose (FDG) has been widely used in the setting of brain tumor imaging, and multiple techniques may be employed to optimize this methodology. More recently, a number of non-18F-FDG-PET radiotracers have been applied toward brain tumor imaging and are used in clinical practice.

Prognostic significance of conventional and volumetric PET parameters with and without partial volume correction in the assessment of head and neck squamous cell carcinoma.

BACKGROUND: The optimal quantification of PET in assessment of head and neck squamous cell carcinoma (HNSCC) is still under development. The effect of partial volume correction (PVC) on the evaluation of survival in the HNSCC patients has not been investigated yet. METHODOLOGY: Pretreatment 18F-FDG-PET/CT scans of a selected group of 57 patients with advanced stage HNSCC were collected. Conventional (SUVmean and SUVmax) and volumetric [total lesion glycolysis (TLG) and metabolic tumor volume (MTV)] PET metrics were calculated. The ROVER software (ABX GmbH, Radeberg, Germany) automatically applied PVC to the PET metrics. Cox proportional hazards regression model calculated hazard ratio (HR) for assessment of predictive parameters of progression-free survival (PFS). RESULTS: In multivariate Cox regression analysis, including age, gender, race, human papillomavirus status, and stage, the only significant predictors of PFS were the volumetric PET parameters (TLG: HR, 1.003; 95% CI, 1.001-1.005; P = 0.02), pvcTLG (HR, 1.002; 95% CI, 1.001-1.004; P = 0.01) and MTV (HR, 1.050; 95% CI, 1.024-1.077; P < 0.01). The partial volume-corrected values were significantly higher than the noncorrected values (Wilcoxon sign test; P < 0.05). However, there was not a statistically significant difference between the nonpartial volume corrected and partial volume-corrected PET metrics for assessment of PFS. CONCLUSION: Volumetric PET metrics were predictors of PFS in Cox regression analysis. Applying PVC could not significantly improve the accuracy of PET metrics for assessment of PFS.

Potential and Most Relevant Applications of Total Body PET/CT Imaging.

ABSTRACT: The introduction of total body (TB) PET/CT instruments over the past 2 years has initiated a new and exciting era in medical imaging. These instruments have substantially higher sensitivity (up to 68 times) than conventional modalities and therefore allow imaging the entire body over a short period. However, we need to further refine the imaging protocols of this instrument for different indications. Total body PET will allow accurate assessment of the extent of disease, particularly, including the entire axial and appendicular skeleton. Furthermore, delayed imaging with this instrument may enhance the sensitivity of PET for some types of cancer. Also, this modality may improve the detection of venous thrombosis, a common complication of cancer and chemotherapy, in the extremities and help prevent pulmonary embolism. Total body PET allows assessment of atherosclerotic plaques throughout the body as a systematic disease. Similarly, patients with widespread musculoskeletal disorders including both oncologic and nononcologic entities, such as degenerative joint disease, rheumatoid arthritis, and osteoporosis, may benefit from the use of TB-PET. Finally, quantitative global disease assessment provided by this approach will be superior to conventional measurements, which do not reflect overall disease activity. In conclusion, TB-PET imaging may have a revolutionary impact on day-to-day practice of medicine and may become the leading imaging modality in the future.