New Application of 18F-Fluoride PET for the Detection of Bone Remodeling in Early-Stage Osteoarthritis of the Hip

Validation of quantitative [18F]NaF PET uptake parameters in bone diseases: a systematic review

PURPOSE

[18F]NaF PET has become an increasingly important tool in clinical practice toward understanding and evaluating diseases and conditions in which bone metabolism is disrupted. Full kinetic analysis using nonlinear regression (NLR) with a two-tissue compartment model to determine the net rate of influx (Ki) of [18F]NaF is considered the gold standard for quantification of [18F]NaF uptake. However, dynamic scanning often is impractical in a clinical setting, leading to the development of simplified semi-quantitative parameters. This systematic review investigated which uptake parameters have been used to evaluate bone disorders and how they have been validated to measure disease activity.

METHODS

A literature search (in PubMed, Embase.com, and Clarivate Analytics/Web of Science Core Collection) was performed up to 28th November 2023, in collaboration with an information specialist. Each database was searched for relevant literature regarding the use of [18F]NAF PET/CT to measure disease activity in bone-related disorders. The main aim was to explore whether the reported semi-quantitative uptake values were validated against full kinetic analysis. A second aim was to investigate whether the chosen uptake parameter correlated with a disease-specific outcome or marker, validating its use as a clinical outcome or disease marker.

RESULTS

The initial search included 1636 articles leading to 92 studies spanning 29 different bone-related conditions in which [18F]NaF PET was used to quantify [18F]NaF uptake. In 12 bone-related disorders, kinetic analysis was performed and compared with simplified uptake parameters. SUVmean (standardized uptake value) and SUVmax were used most frequently, though normalization of these values varied greatly between studies. In some disorders, various studies were performed evaluating [18F]NaF uptake as a marker of bone metabolism, but unfortunately, not all studies used this same approach, making it difficult to compare results between those studies.

CONCLUSION

When using [18F]NaF PET to evaluate disease activity or treatment response in various bone-related disorders, it is essential to detail scanning protocols and analytical procedures. The most accurate outcome parameter can only be obtained through kinetic analysis and is better suited for research. Simplified uptake parameters are better suited for routine clinical practice and repeated measurements.

Multimodal positron emission tomography (PET) imaging in non-oncologic musculoskeletal radiology

Musculoskeletal (MSK) disorders are associated with large impacts on patient's pain and quality of life. Conventional morphological imaging of tissue structure is limited in its ability to detect pain generators, early MSK disease, and rapidly assess treatment efficacy. Positron emission tomography (PET), which offers unique capabilities to evaluate molecular and metabolic processes, can provide novel information about early pathophysiologic changes that occur before structural or even microstructural changes can be detected. This sensitivity not only makes it a powerful tool for detection and characterization of disease, but also a tool able to rapidly assess the efficacy of therapies. These benefits have garnered more attention to PET imaging of MSK disorders in recent years. In this narrative review, we discuss several applications of multimodal PET imaging in non-oncologic MSK diseases including arthritis, osteoporosis, and sources of pain and inflammation. We also describe technical considerations and recent advancements in technology and radiotracers as well as areas of emerging interest for future applications of multimodal PET imaging of MSK conditions. Overall, we present evidence that the incorporation of PET through multimodal imaging offers an exciting addition to the field of MSK radiology and will likely prove valuable in the transition to an era of precision medicine.

Imaging of Pain using Positron Emission Tomography

Positron emission tomography (PET) is a noninvasive molecular imaging technique that utilizes biologically active radiolabeled compounds to image biochemical processes. As such, PET can provide important pathophysiological information associated with pain of different etiologies. As such, the information obtained using PET often combined with MRI or CT can provide useful information for diagnosing and monitoring changes associated with pain. This review covers the most important PET tracers that have been used to image pain including tracers for fundamental biological processes such as glucose metabolism and cerebral blood flow to receptor-specific tracers such as ion channels and neurotransmitters. For tracer type, we describe the structure and radiochemical synthesis of the tracer followed by a brief summary of the available preclinical and clinical studies. By providing a summary of the PET tracers that have been employed for PET imaging of pain, this review aims to serve as a reference for preclinical, translational and clinical investigators interested in molecular imaging of pain. Finally, the review ends with an outlook of the needs and opportunities in this area.

Imaging of Cartilage and Chondral Defects: An Overview

A healthy articular cartilage is paramount to joint function. Cartilage defects, whether acute or chronic, are a significant source of morbidity. This review summarizes various imaging modalities used for cartilage assessment. While radiographs are insensitive, they are still widely used to indirectly assess cartilage. Ultrasound has shown promise in the detection of cartilage defects, but its efficacy is limited in many joints due to inadequate visualization. CT arthrography has the potential to assess internal derangements of joints along with cartilage, especially in patients with contraindications to MRI. MRI remains the favored imaging modality to assess cartilage. The conventional imaging techniques are able to assess cartilage abnormalities when cartilage is already damaged. The newer imaging techniques are thus targeted at detecting biochemical and structural changes in cartilage before an actual visible irreversible loss. These include, but are not limited to, T2 and T2* mapping, dGEMRI, T1ρ imaging, gagCEST imaging, sodium MRI and integrated PET with MRI. A brief discussion of the advances in the surgical management of cartilage defects and post-operative imaging assessment is also included.

Imaging of Osteoarthritis of the Knee

Knee osteoarthritis is rising in prevalence, and more imaging studies are being requested to evaluate these patients. Although conventional radiographs of the knee are the most widely requested and available studies, other imaging modalities such as MRI, CT, and ultrasound may also be used. This article reviews commonly used imaging modalities, advantages and limitations of each, and their clinical applicability in diagnosing and monitoring knee osteoarthritis. New and advanced imaging techniques are also discussed as possible methods of early diagnosis and improved understanding of osteoarthritis pathophysiology.

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.

Emerging role of integrated PET-MRI in osteoarthritis

Osteoarthritis (OA) is a common degenerative disorder of the articular cartilage, which is associated with hypertrophic changes in the bone, synovial inflammation, subchondral sclerosis, and joint space narrowing (JSN). Radiography remains the first line of imaging till now. Due to the lack of soft-tissue depiction in radiography, researchers are exploring various imaging techniques to detect OA at an early stage and understand its pathophysiology to restrict its progression and discover disease-modifying agents in OA. As the OA relates to the degradation of articular cartilage and remodeling of the underlying bone, an optimal imaging tool must be sensitive to the bone and soft tissue health. In that line, many non-invasive imaging and minimally invasive techniques have been explored. Out of these, the non-invasive compositional magnetic resonance imaging (MRI) for evaluation of the integrity of articular cartilage and positron emission tomography (PET) scan with fluorodeoxyglucose (FDG) and more specific bone-seeking tracer like sodium fluoride (18F-NaF) for bone cartilage interface are some of the leading areas of ongoing work. Integrated PET-MRI system, a new hybrid modality that combines the virtues of the above two individual modalities, allows detailed imaging of the entire joint, including soft tissue cartilage and bone, and holds great potential to research complex disease processes of OA. This narrative review attempts to signify individual characteristics of MRI, PET, the fusion of these characteristics in PET-MRI, and the ongoing research on PET-MRI as a potential tool to understand the pathophysiology of OA.

Normal Skeletal Standardized Uptake Values Obtained from Quantitative Single-Photon Emission Computed Tomography/Computed Tomography: Time-Dependent Study on Breast Cancer Patients

Aim:

To estimate the standard uptake values (SUVs) of Tc-99m methylene-diphosphonate (Tc-99m MDP) from normal skeletal sites in breast cancer patients using quantitative single-photon emission computed tomography (SPECT).

Materials and Methods:

A total of 60 breast cancer patients who underwent Tc-99m MDP SPECT/CT study at different postinjection acquisition times were included in this study. Based on postinjection acquisition time, patients were divided into four study groups (n_15 each), i.e. I^st (2 h), II^nd (3 h), III^rd (4 h), and IV^th (5 h). Image quantification (SUVmax and SUVmean) was performed using Q.Metrix software. Delineation of volume of interest was shaped around different bones of the skeletal system.

Results:

The highest normal SUVmax and SUVmean values were observed in lumber and thoracic vertebra (8.89 ± 2.26 and 2.89 ± 0.58) for Group I and in pelvis and thoracic (9.6 ± 1.32 and 3.04 ± 0.64), (10.93 ± 3.91 and 3.65 ± 0.97), (11.33 ± 2.67 and 3.65 ± 0.22) for Group II, III and IV, respectively. Lowest normal SUVmax and SUVmean values were observed in humerus and ribs (3.22 ± 0.67 and 0.97 ± 0.18), (5.16 ± 1.82 and 1.18 ± 0.16) for Group I, IV, and in humerus (3.17 ± 0.58 and 0.85 ± 0.26), (3.98 ± 1.12 and 1.04 ± 0.28) for Group II and III, respectively. Significant difference (P < 0.05) noted in SUVmax for sternum, cervical, humerus, ribs, and pelvis with respect to time. However, significant difference (P < 0.05) noted in SUVmean for all skeletal sites with respect to time.

Conclusions:

Our study shows variability in normal SUV values for different skeletal sites in breast cancer patients. Vertebral bodies and pelvis contribute highest SUV values. Time dependency of SUVs emphasizes the usefulness of routinely acquired images at the same time after Tc-99m MDP injection, especially in follow-up studies.

Comparison of 18F-sodium fluoride positron emission tomography and CT: An exploratory study in 12 dogs with elbow pain

18F-Sodium Fluoride (18F-NaF) positron emission tomography (PET) provides high resolution functional information about bone activity and can be fused with CT images to improve three-dimensional localization and characterization of lesions. This prospective, observational study assessed 18F-NaF PET-CT for imaging of canine elbows, compared PET with CT findings, and assessed correlation with lameness. Twelve patients with elbow pain were included. Cases included primarily young, large breed dogs. A three-level clinical lameness score was assigned to each forelimb. All dogs had bilateral elbow joints imaged with CT and PET under general anesthesia, approximately 1.5 h after intravenous injection of 3 MBq/kg of 18F-NaF. Imaging findings were independently reviewed by two radiologists using a three-level scoring scheme over nine anatomical regions in the elbow. PET imaging identified areas of bone activity where minimal change was identified on CT. PET imaging also demonstrated absence of uptake in areas where modeling was present on CT. A stronger correlation was observed between clinical grades and PET scores (r2  = 0.38, P = .001) than between clinical grades and CT scores (r2  = 0.17, P = .048). The total PET scores were significantly different for each clinical grade (P = .013) but total CT scores did not differ (P = .139). This exploratory study suggests that PET improves the ability to detect lesions and to determine the clinical significance of CT findings in dogs with elbow pain.

Magnetic resonance imaging-based partial volume-corrected 18F-sodium fluoride positron emission tomography in the femoral neck

OBJECTIVES

18F-sodium fluoride (NaF) is a radiotracer used in PET that reflects calcium metabolism and osteoblastic activity. In this study, we assessed the construct validity of a novel application of global assessment to measure NaF uptake in the femoral neck as a method of evaluating physiologic changes in osteoblastic metabolism with age.

METHODS

Whole-body NaF-PET/computed tomography (CT) images and MRI of 24 male patients with a history of nonmetastatic prostate cancer between the ages of 36 and 82 years (67.8 ± 9.6) were analyzed. A region of interest delineated the entire femoral neck on the PET/CT image to determine the mean standardized uptake value (SUVmean). Correction for the partial volume effect was performed by measuring the volume of inert yellow bone marrow by MRI segmentation. Multiple linear regression was used to assess the relationship of uptake with age and body weight.

RESULTS

The SUVmean with and without partial volume correction decreased with respect to age (P = 0.001 and P = 0.002, respectively). Body weight was not significantly related to any measured PET parameter.

CONCLUSION

Our results support the use of global NaF uptake with magnetic resonance-derived partial volume correction in the femoral neck. Because osteoblastic metabolism is known to decrease with normal aging, the observed decrease in NaF uptake constitutes evidence for convergent validity, indicating that the proposed methodology likely reflects systemic osteoblastic activity. Future studies of this methodology are warranted in other instances of varying osteoblastic activity such as in metabolic bone diseases and for the evaluation of therapy targeting osteoblastic metabolism.

Total-Body PET Imaging of Musculoskeletal Disorders

Imaging of musculoskeletal disorders, including arthritis, infection, osteoporosis, sarcopenia, and malignancies, is often limited when using conventional modalities such as radiography, computed tomography (CT), and MR imaging. As a result of recent advances in Positron Emission Tomography (PET) instrumentation, total-body PET/CT offers a longer axial field-of-view, higher geometric sensitivity, and higher spatial resolution compared with standard PET systems. This article discusses the potential applications of total-body PET/CT imaging in the assessment of musculoskeletal disorders.

Identifying Musculoskeletal Pain Generators Using Clinical PET

Identifying the source of a person's pain is a significant clinical challenge because the physical sensation of pain is believed to be subjective and difficult to quantify. The experience of pain is not only modulated by the individual's threshold to painful stimuli but also a product of the person's affective contributions, such as fear, anxiety, and previous experiences. Perhaps then to quantify pain is to examine the degree of nociception and pro-nociceptive inflammation, that is, the extent of cellular, chemical, and molecular changes that occur in pain-generating processes. Measuring changes in the local density of receptors, ion channels, mediators, and inflammatory/immune cells that are involved in the painful phenotype using targeted, highly sensitive, and specific positron emission tomography (PET) radiotracers is therefore a promising approach toward objectively identifying peripheral pain generators. Although several preclinical radiotracer candidates are being developed, a growing number of ongoing clinical PET imaging approaches can measure the degree of target concentration and thus serve as a readout for sites of pain generation. Further, when PET is combined with the spatial and contrast resolution afforded by magnetic resonance imaging, nuclear medicine physicians and radiologists can potentially identify pain drivers with greater accuracy and confidence. Clinical PET imaging approaches with fluorine-18 fluorodeoxyglucose, fluorine-18 sodium fluoride, and sigma-1 receptor PET radioligand and translocator protein radioligands to isolate the source of pain are described here.

Posterior acetabular uptake on 18F-fluoride positron emission tomography/computed tomography reveals a putative contrecoup region in patients with femoroacetabular impingement

BACKGROUND AND PURPOSE

The pathology of the posterior acetabular lesions, so-called "contrecoup regions", in femorocacetabular impingement (FAI) has not been elucidated fully. ¹⁸F-fluoride positron emission tomography/computed tomography (PET/CT) can visualize abnormal uptake caused by impingement. Therefore, we aimed to evaluate posterior acetabular uptake on PET/CT in FAI patients.

PATIENTS AND METHODS

Patients with FAI who underwent ¹⁸F-fluoride PET/CT between October 2014 and October 2016 were retrospectively evaluated. The maximum standardized uptake value (SUV_max) in the posterior acetabulum was evaluated. The mean SUV_max of FAI with cam morphology (the cam group) was compared with that of FAI with pincer morphology (the pincer group). In addition, the numbers of cases with SUV_max ≥ 6 and SUV_max < 6 in each group were evaluated. The entire study cohort was also grouped according to SUV_max, and the mean α and center edge angles were evaluated.

RESULTS

In total, 41 hips were analyzed (34 hips in the cam group and 7 in the pincer group). The mean SUV_max of the cam group (11.2 ± 7.4) was significantly higher than that of the pincer group (4.9 ± 1.9) (p < 0.01). The incidence of cases with SUV_max ≥ 6 in the cam group was significantly high (p < 0.01). In the overall cohort, the mean α angle of the SUV_max ≥ 6 group was significantly higher than that of the SUV_max < 6 group (p < 0.01).

CONCLUSION

Evaluation of posterior acetabular uptake suggests an association between cam morphology and increased posterior acetabular uptake.

Fusion and Healing Prediction in Posterolateral Spinal Fusion Using 18F-Sodium Fluoride-PET/CT

This study measures the total graft of ¹⁸F-sodium fluoride (NaF) uptake in non-instrumented posterolateral lumbar fusion (niPLF) patients one month after surgery and correlates it with the difference in the clinical findings between the baseline and one year after surgery. The walking distance (WLK-D), visual analog scale of back pain (VAS-B), VAS score of leg pain (VAS-L), tandem test (TAN), Oswestry Disability Index questionnaire (ODI), and European Quality of Life-5 Dimensions questionnaire (EQ-5D) were assessed before surgery and one year after. The graft NaF uptake was analyzed quantitatively with a fixed threshold algorithm resulting in the total graft uptake (SUVtotal) and partial volume corrected SUVtotal (cSUVtotal). Only 4 out of 18 patients experienced fusion; they had an insignificantly lower median total graft uptakes, i.e., 1178 SUVtotal vs. 1224 SUVtotal (p = 0.73) and 1282 cSUVtotal vs. 1231 cSUVtotal (p = 0.35), respectively. Similarly, fused patients experienced insignificantly larger pain decreases, i.e., median VAS-B 4.3 vs. 3.8 (p = 0.92) and VAS-L −6.4 vs. −4.4 (p = 0.2). We found an insignificant trend for a lower NaF uptake and less pain in fused patients. The NaF uptake did not correlate with the chronological change in the clinical parameters.

Bone metabolism of the jaw in response to bisphosphonate: a quantitative analysis of bone scintigraphy images

We examined the changes in the bone metabolism of the jaw in response to BP treatment, and we used bone SPECT-CT to analyze the site-specific bone metabolism between the jaw and other sites of bone. We compared the changes in the bone metabolism of each part of bone in response to BP treatment by performing a quantitative analysis of bone scintigraphy images between patients treated with low-dose BP for osteoporosis (LBP group; n = 17), those treated with high-dose BP for metastatic bone tumor (HBP group; n = 11), and patients with other oral disease who required bone scintigraphy, with no history of BP treatment (control group; n = 40). The study endpoint was the mean standardized uptake value (SUV) of the uptake of Tc-99 m methylene diphosphonate (MDP) in each group. The mean SUVs of the HBP group were significantly lower at the axial bone of the cervical vertebra, thoracic vertebra, sternum, and rib compared to those of the LBP and control groups. The LBP group's mean SUV was significantly higher at the temporal bone, the anodontia part of the alveolar bone in maxilla, the vital teeth part of alveolar bone in the mandible, and the temporomandibular joint. There was no significant difference among the three groups at the mandibular angle and mandibular ramus. Our analyses revealed that the bone metabolism of the jaw and temporal bone in the BP-treated patients was enhanced, and no suppression of bone remodeling in the jaw by BP was observed.

[18 F]-Sodium Fluoride PET/MR Imaging for Bone-Cartilage Interactions in Hip Osteoarthritis: A Feasibility Study

This study characterized the distribution of [¹⁸ F]-sodium fluoride (NaF) uptake and blood flow in the femur and acetabulum in hip osteoarthritis (OA) patients to find associations between bone remodeling and cartilage composition in the presence of morphological abnormalities using simultaneous positron emission tomography and magnetic resonance imaging (PET/MR), quantitative magnetic resonance imaging (MRI) and femur shape modeling. Ten patients underwent a [¹⁸ F]-NaF PET/MR dynamic scan of the hip simultaneously with: (i) fast spin-echo CUBE for morphology grading and (ii) T_1ρ /T₂ magnetization-prepared angle-modulated partitioned k-space spoiled gradient echo snapshots for cartilage, bone segmentation, bone shape modeling, and T_1ρ /T₂ quantification. The standardized uptake values (SUVs) and Patlak kinetic parameter (K_pat ) were calculated for each patient as PET outcomes, using an automated post-processing pipeline. Shape modeling was performed to extract the variations in bone shapes in the patients. Pearson's correlation coefficients were used to study the associations between bone shapes, PET outcomes, and patient reported pain. Direct associations between quantitative MR and PET evidence of bone remodeling were established in the acetabulum and femur. Associations of shaft thickness with SUV in the femur (p = 0.07) and K_pat in the acetabulum (p = 0.02), cam deformity with acetabular score (p = 0.09), osteophytic growth on the femur head with K_pat (p = 0.01) were observed. Pain had increased correlations with SUV in the acetabulum (p = 0.14) and femur (p = 0.09) when shaft thickness was accounted for. This study demonstrated the ability of [¹⁸ F]-NaF PET-MRI, 3D shape modeling, and quantitative MRI to investigate cartilage-bone interactions and bone shape features in hip OA, providing potential investigative tools to diagnose OA. © 2019 The Authors. Journal of Orthopaedic Research^® published by Wiley Periodicals, Inc. on behalf of Orthopaedic Research Society J Orthop Res 37:2671-2680, 2019.

Applications of PET-Computed Tomography-Magnetic Resonance in the Management of Benign Musculoskeletal Disorders

Although computed tomography (CT) and MR imaging alone have been used extensively to evaluate various musculoskeletal disorders, hybrid imaging modalities of PET-CT and PET-MR imaging were recently developed, combining the advantages of each method: molecular information from PET and anatomical information from CT or MR imaging. Furthermore, different radiotracers can be used in PET to uncover different disease mechanisms. In this article, potential applications of PET-CT and PET-MR imaging for benign musculoskeletal disorders are organized by benign cell proliferation/dysplasia, diabetic foot complications, joint prostheses, degeneration, inflammation, and trauma, metabolic bone disorders, and pain (acute and chronic) and peripheral nerve imaging.

PET-MRI for the Study of Metabolic Bone Disease

PURPOSE OF REVIEW

This review article attempts to summarize the current state and applications of the hybrid imaging modality of PET-MRI to metabolic bone diseases. The advances of PET and MRI are also discussed for metabolic bone diseases as potentially applied via PET-MRI.

RECENT FINDINGS

Etiologies and mechanisms of metabolic bone disease can be complex where molecular changes precede structural changes. Although PET-MRI has yet to be applied directly to metabolic bone disease, possible applications exist since PET, specifically 18F-NaF PET, can quantitatively track changes in bone metabolism and is useful for assessing treatment, while MRI can give detailed information on bone water concentration, porosity, and architecture through novel techniques such as UTE and ZTE MRI. Earlier detection and further understanding of metabolic bone disease via PET and MRI could lead to better treatment and prevention. More research using this modality is needed to further understand how it can be implemented in this realm.

In Vivo Molecular Imaging of Musculoskeletal Inflammation and Infection

In vivo molecular imaging detects biologic processes at molecular level and provides diagnostic information at an earlier time point during disease onset or repair. It offers definite advantage over anatomic imaging in terms of improved sensitivity and ability to quantify. Radionuclide molecular imaging has been widely used in clinical practice. This article discusses the role of radionuclide imaging in various infective and inflammatory diseases affecting musculoskeletal system with a focus on PET. It appears that, as more data become available, combined PET/MR imaging could emerge as a front runner in the imaging of musculoskeletal infection and inflammation.

PET/MRI in Infection and Inflammation

Hybrid positron emission tomography/magnetic resonance imaging (PET/MR) systems are now more and more available for clinical use. PET/MR combines the unique features of MR including excellent soft tissue contrast, diffusion-weighted imaging, dynamic contrast-enhanced imaging, fMRI and other specialized sequences as well as MR spectroscopy with the quantitative physiologic information that is provided by PET. Most of the evidence of the potential clinical utility of PET/MRI is available for neuroimaging. Other areas, where PET/MR can play a larger role include head and neck, upper abdominal, and pelvic tumours. Although the role of PET/MR in infection and inflammation of the cardiovascular system and in musculoskeletal applications are promising, these areas of clinical investigation are still in the early phase and it may be a little longer before these areas reach their full potential in clinical practice. In this review, we outline the potential of hybrid PET/MR for imaging infection and inflammation. A background to the main radiopharmaceuticals and some technical considerations are also included.

The prognostic and diagnostic value of 18F-FDG PET/CT for assessment of symptomatic osteoarthritis

OBJECTIVE

The objective of this study was to assess the clinical significance of increased fluorine-18-fluorodeoxyglucose (F-FDG) uptake on PET/CT in joints for evaluation of symptomatic osteoarthritis (OA) and prediction of progression.

PATIENTS AND METHODS

In this prospective study, shoulder, hip, and knee joints were imaged in 65 patients undergoing routine F-FDG PET/CT imaging. Patients completed the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) questionnaire to assess joint pain, stiffness, and physical function. Standardized uptake values (SUVs) were measured in hip, knee, acromioclavicular (AC), and glenohumeral (GH) joints. Scout PET/CT images were evaluated for OA using the Kellgren and Lawrence (K/L) system. Patients were followed-up for 5 years to determine the progression of OA on the basis of follow-up imaging or surgical intervention.

RESULTS

SUV of knee (r=0.309, P=0.0003), hip (r=0.260, P=0.0027), AC (r=0.186, P=0.0313), and GH (r=0.191, P=0.0271) joints correlated with WOMAC overall scores. Furthermore, SUV of knee (r=0.410, P<0.0001), hip (r=0.203, P=0.0199), and AC (r=0.364, P<0.0001) joints correlated with K/L scores. The area under the receiver operating characteristic curves for SUV were 0.734 (knee), 0.678 (hip), 0.661 (AC), and 0.544 (GH) for symptomatic OA detection based on WOMAC overall z-score greater or equal to 2. Compared with K/L score [hazard ratio (HR)=0.798, P=0.5324], age (HR=0.992, P=0.8978), and WOMAC overall score (HR=1.089, P=0.1265), only SUV (HR=5.653, P=0.0229) was an independent predictor of OA progression in the knees.

CONCLUSION

F-FDG PET/CT may be helpful with localization of painful abnormalities in the inflamed regions of the joints, which could potentially be used to direct individualized treatment in moderate and severe OA. Furthermore, SUV measurement on F-FDG PET/CT could serve as an inflammation activity index in the knees that may be predictive of outcomes and progression rate of OA.

Bone formation in ankylosing spondylitis during anti-tumour necrosis factor therapy imaged by 18F-fluoride positron emission tomography

Objectives

Excessive bone formation is an important hallmark of AS. Recently it has been demonstrated that axial bony lesions in AS patients can be visualized using ¹⁸F-fluoride PET-CT. The aim of this study was to assess whether ¹⁸F-fluoride uptake in clinically active AS patients is related to focal bone formation in spine biopsies and is sensitive to change during anti-TNF treatment.

Methods

Twelve anti-TNF-naïve AS patients [female 7/12; age 39 years (SD 11); BASDAI 5.5 ± 1.1] were included. ¹⁸ F-fluoride PET-CT scans were performed at baseline and in two patients, biopsies were obtained from PET-positive and PET-negative spine lesions. The remaining 10 patients underwent a second ¹⁸F-fluoride PET-CT scan after 12 weeks of anti-TNF treatment. PET scans were scored visually by two blinded expert readers. In addition, ¹⁸F-fluoride uptake was quantified using the standardized uptake value corrected for individual integrated whole blood activity concentration (SUV_AUC). Clinical response to anti-TNF was defined according to a ⩾ 20% improvement in Assessment of SpondyloArthritis international Society criteria at 24 weeks.

Results

At baseline, all patients showed at least one axial PET-positive lesion. Histological analysis of PET-positive lesions in the spine confirmed local osteoid formation. PET-positive lesions were found in the costovertebral joints (43%), facet joints (23%), bridging syndesmophytes (20%) and non-bridging vertebral lesions (14%) and in SI joints (75%). After 12 weeks of anti-TNF treatment, ¹⁸F-fluoride uptake in clinical responders decreased significantly in the costovertebral (mean SUV_AUC −1.0; P < 0.001) and SI joints (mean SUV_AUC −1.2; P = 0.03) in contrast to non-responders.

Conclusions

¹⁸F-fluoride PET-CT identified bone formation, confirmed by histology, in the spine and SI joints of AS patients and demonstrated alterations in bone formation during anti-TNF treatment.

New imaging modalities to predict and evaluate osteoarthritis progression

In this narrative review, we discuss the role of different imaging methods for the evaluation of progression of structural osteoarthritis. We will focus on the role of less commonly applied imaging modalities and imaging biomarkers that were introduced in recent years or on established methods that have evolved into more prominent positions in recent years. We will highlight findings from longitudinal studies that focused on structural osteoarthritis progression as their outcome of interest. Imaging modalities discussed include plain radiography (including novel approaches of joint space width assessment and fractal signature analysis), ultrasonography (including the assessment of synovitis), magnetic resonance imaging (including semiquantitative, quantitative, and compositional evaluation), and positron emission tomography.

Feasibility of Na18F PET/CT and MRI for Noninvasive In Vivo Quantification of Knee Pathophysiological Bone Metabolism in a Canine Model of Post-traumatic Osteoarthritis

Purpose:

To assess and quantify by molecular imaging knee osseous metabolic changes serially in an in vivo canine model of posttraumatic osteoarthritis (PTOA) of the knee utilizing sodium fluoride (Na¹⁸F) positron emission tomography (PET)/computed tomography (CT) coregistered with magnetic resonance imaging (MRI).

Materials and Methods:

Sodium fluoride PET imaging of 5 canines was performed prior to anterior cruciate ligament transection (ACLT) and 2 times post-ACLT (3 and 12 weeks). The PET/CT was coregistered with MRI, enabling serial anatomically guided visual and quantitative three-dimensional (3D) region of interest (ROI) assessment by maximum standardized uptake value.

Results:

Prior to ACLT, every 3D ROI assessed in both knees showed no Na¹⁸F uptake above background. The uptake of Na¹⁸F in the bone of the ACLT knees increased exponentially, presenting significantly higher uptake at 12 weeks in every region compared to the ACLT knees at baseline. Furthermore, the uninjured contralateral limb and the ipsilateral distal bones and joints presented Na¹⁸F uptake at 3 and 12 weeks post-ACLT.

Conclusion:

This study demonstrated that Na¹⁸F PET/CT coregistered with MRI is a feasible molecular imaging biomarker to assess knee osseous metabolic changes serially in an in vivo canine model of knee PTOA. Moreover, it brings a novel musculoskeletal preclinical imaging methodology that can provide unique insights into PTOA pathophysiology.

The Relationship Between the Location of Uptake on Positron Emission Tomography/Computed Tomography and the Impingement Point by Computer Simulation in Femoroacetabular Impingement Syndrome With Cam Morphology

PURPOSE

To clarify the concordance rate of the location of uptake on positron emission tomography/computed tomography (PET/CT) and the impingement point demonstrated in computer simulation in femoroacetabular impingement (FAI) syndrome with cam morphology.

METHODS

We included hip joints with FAI syndrome that underwent ¹⁸F-fluoride PET/CT. We also excluded hips with SUV_max <6. Each hip was evaluated for the region of the SUV_max point on PET/CT as well as the impingement point by computer simulation. We used ZedHip software (Lexi, Tokyo, Japan) for impingement simulation analysis based on CT data. Bony impingement is identified if there is a mesh in acetabular and femoral side contact in at least one unit. We investigated the rate of concordance between these 2 regions for each 10° flexion angle of the hip, ranging from 0° to 90°.

RESULTS

Twenty-two hips of 22 patients were evaluated. The SUV_max region was most frequently distributed in the proximal middle region in 12 hips. In 18 of 22 hips (81.8%), the SUV_max region was concordant with the impingement region for at least one flexion angle. The concordance rates in 50° (P = .034), 60° (P = .007), 70° (P = .011), and 80° (P = .046) of flexion were significantly higher than in 90° of flexion.

CONCLUSIONS

It was possible to visualize and clarify the detailed location of abnormal uptake in FAI syndrome patients with cam morphology by applying ¹⁸F-fluoride PET/CT. The concordance rates in 50°, 60°, 70°, and 80° of flexion were significantly higher than in 90° of flexion, which suggested that impingement may more frequently occur at less than 90° of flexion in FAI syndrome with cam morphology.

LEVEL OF EVIDENCE

Level III, cross-sectional diagnostic study.

Predicting the collapse of the femoral head due to osteonecrosis: From basic methods to application prospects

Collapse of the femoral head is the most significant pathogenic complication arising from osteonecrosis of the femoral head. It is related to the disruption of the maintenance of cartilage and bone, and results in an impaired function of the vascular component. A method for predicting the collapse of the femoral head can be treated as a type of clinical index. Efforts in recent years to predict the collapse of the femoral head due to osteonecrosis include multiple methods of radiographic analysis, stress distribution analysis, finite element analysis, and other innovative methods. Prediction methods for osteonecrosis of the femoral head complications originated in Western countries and have been further developed in Asia. Presently, an increasing number of surgeons have chosen to focus on surgical treatments instead of prediction methods to guide more conservative interventions, resulting in a growing reliance on the more prevalent and highly effective total hip arthroplasty, rather than on more conservative treatments. In this review, we performed a literature search of PubMed and Embase using search terms including "osteonecrosis of femoral head," "prediction," "collapse," "finite element," "radiographic images," and "stress analysis," exploring the basic prediction method and prospects for new applications.

Evaluation of local bone turnover in painful hip by 18F-fluoride positron emission tomography

OBJECTIVE

The diagnosis of painful hip without remarkable radiographic findings is still challenging. In recent years, femoroacetabular impingement (FAI) has been recognized as an important cause of painful hip. The hypothesis of this study was that local bone turnover may be accelerated in painful hip, especially in FAI lesions. To test this, patients with unilateral symptomatic hip underwent F-fluoride PET, which directly correlates with osteoblast activity and therefore bone turnover.

PATIENTS AND METHODS

In total, 27 patients with unilateral symptomatic painful hip were enrolled. The diagnosis included 15 cam-type FAI cases, six labral tear cases, and six early-stage osteoarthritis cases. The region of interest for cam and pincer lesions was identified and the maximum standardized uptake value (SUVmax) in these regions and the contralateral asymptomatic regions were measured by F-fluoride PET. The SUVmax ratio was defined as symptomatic side SUVmax/asymptomatic side SUVmax. The α angle and center-edge angle were measured by plain radiograph.

RESULTS

The SUVmax of both cam and pincer lesions were significantly higher than the SUVmax of the contralateral regions (P<0.0001). The cam SUVmax ratio correlated positively with the α angle (r=0.5, P=0.007). Patients with an α angle of more than or equal to 60° had a significantly higher cam SUVmax ratio than the less than 60° group (P=0.017).

CONCLUSION

This study showed the accelerated local bone turnover in painful hip, partly in FAI cases. Accelerated bone turnover may play a significant role in FAI pathophysiology; therefore, its recognition by imaging modality may contribute toward a more sensitive diagnosis in painful hip.

Potential of PET-MRI for imaging of non-oncologic musculoskeletal disease

Early detection of musculoskeletal disease leads to improved therapies and patient outcomes, and would benefit greatly from imaging at the cellular and molecular level. As it becomes clear that assessment of multiple tissues and functional processes are often necessary to study the complex pathogenesis of musculoskeletal disorders, the role of multi-modality molecular imaging becomes increasingly important. New positron emission tomography-magnetic resonance imaging (PET-MRI) systems offer to combine high-resolution MRI with simultaneous molecular information from PET to study the multifaceted processes involved in numerous musculoskeletal disorders. In this article, we aim to outline the potential clinical utility of hybrid PET-MRI to these non-oncologic musculoskeletal diseases. We summarize current applications of PET molecular imaging in osteoarthritis (OA), rheumatoid arthritis (RA), metabolic bone diseases and neuropathic peripheral pain. Advanced MRI approaches that reveal biochemical and functional information offer complementary assessment in soft tissues. Additionally, we discuss technical considerations for hybrid PET-MR imaging including MR attenuation correction, workflow, radiation dose, and quantification.

Imaging of osteoarthritis (OA): What is new?

In daily clinical practice, conventional radiography is still the most applied imaging technique to supplement clinical examination of patients with suspected osteoarthritis (OA); it may not always be needed for diagnosis. Modern imaging modalities can visualize multiple aspects of the joint, and depending on the diagnostic need, radiography may no longer be the modality of choice. Magnetic resonance imaging (MRI) provides a complete assessment of the joint and has a pivotal role in OA research. Computed tomography (CT) and nuclear medicine offer alternatives in research scenarios, while ultrasound can visualize bony and soft-tissue pathologies and is highly feasible in the clinic. In this chapter, we overview the recent literature on established and newer imaging modalities, summarizing their ability to detect and quantify the range of OA pathologies and determining how they may contribute to early OA diagnosis. This accurate imaging-based detection of pathologies will underpin true understanding of much needed structure-modifying therapies.

Evolving Role of Molecular Imaging with (18)F-Sodium Fluoride PET as a Biomarker for Calcium Metabolism

(18)F-sodium fluoride (NaF) as an imaging tracer portrays calcium metabolic activity either in the osseous structures or in soft tissue. Currently, clinical use of NaF-PET is confined to detecting metastasis to the bone, but this approach reveals indirect evidence for disease activity and will have limited use in the future in favor of more direct approaches that visualize cancer cells in the read marrow where they reside. This has proven to be the case with FDG-PET imaging in most cancers. However, a variety of studies support the application of NaF-PET to assess benign osseous diseases. In particular, bone turnover can be measured from NaF uptake to diagnose osteoporosis. Several studies have evaluated the efficacy of bisphosphonates and their lasting effects as treatment for osteoporosis using bone turnover measured by NaF-PET. Additionally, NaF uptake in vessels tracks calcification in the plaques at the molecular level, which is relevant to coronary artery disease. Also, NaF-PET imaging of diseased joints is able to project disease progression in osteoarthritis, rheumatoid arthritis, and ankylosing spondylitis. Further studies suggest potential use of NaF-PET in domains such as back pain, osteosarcoma, stress-related fracture, and bisphosphonate-induced osteonecrosis of the jaw. The critical role of NaF-PET in disease detection and characterization of many musculoskeletal disorders has been clearly demonstrated in the literature, and these methods will become more widespread in the future. The data from PET imaging are quantitative in nature, and as such, it adds a major dimension to assessing disease activity.

Prediction of femoral head collapse in osteonecrosis using 18F-fluoride positron emission tomography

OBJECTIVE

We investigated the usefulness of (18)F-fluoride PET as a predictor of femoral head collapse in patients with osteonecrosis (ON) before radiographic changes occur.

PATIENTS AND METHODS

Sixty-six hips of 42 patients diagnosed with ON of the femoral head were included in this study. We evaluated the relationship between the maximum standardized uptake value (SUV(max)) in (18)F-fluoride PET and the Ficat classification. We evaluated the relationship between SUV(max) and the presence of femoral head collapse on plain radiography at 12 months after (18)F-fluoride PET in 23 hips of 18 patients with Ficat classification stage 1 or 2. A receiver operating characteristic analysis was carried out to calculate the cut-off SUVmax for the prediction of femoral head collapse. We analyzed the relationship between SUV(max) and femoral head collapse on plain radiography in the 23 hips using a logistic regression model.

RESULTS

SUV(max) increased according to the progression of the Ficat classification stage. The mean SUV(max) was 12.3±5.9 in the collapse group and 4.9±1.3 in the noncollapse group (P<0.01). The cut-off SUV(max) of 6.45 (sensitivity: 0.80, specificity: 0.92) was used for the prediction of femoral head collapse. In the univariate analysis, SUV(max), type classification, and ring sign were related significantly to femoral head collapse.

CONCLUSION

We showed that the quantitative assessment of SUV(max) in (18)F-fluoride PET was useful to predict femoral head collapse in ON. (18)F-Fluoride PET might reflect accelerated bone metabolism because of microcollapse of the femoral head, which is undetectable on plain radiography.

(18)F-FDG and (18)F-NaF PET/CT demonstrate coupling of inflammation and accelerated bone turnover in rheumatoid arthritis

OBJECTIVE

To compare the findings in rheumatoid arthritis (RA)-affected joints between (18)F-fluorodeoxyglucose (FDG) and (18)F-fluoride (NaF) positron emission tomography (PET)/computed tomography (CT).

METHODS

We enrolled twelve RA patients who started a new biologic agent (naïve 9 and switch 3). At entry, both hands were examined by (18)F-FDG PET/CT, (18)F-NaF PET/CT, and X-ray. Intensity of PET signals was determined by standardized uptake value max (SUVmax) in metacarpophalangeal (MCP), proximal interphalangeal (PIP), and ulnar, medial, and radial regions of the wrists. Hand X-rays were evaluated according to the Genant-modified Sharp score at baseline and 6 months.

RESULTS

Both (18)F-FDG and (18)F-NaF accumulated in RA-affected joints. The SUVmax of (18)F-FDG correlated with that of (18)F-NaF in individual joints (r = 0.65), though detail distribution was different between two tracers. (18)F-NaF and (18)F-FDG signals were mainly located in the bone and the surrounding soft tissues, respectively. The sum of SUVmax of (18)F-NaF correlated with disease activity score in 28 joint (DAS28), modified health assessment questionnaire (MHAQ), and radiographic progression. (18)F-FDG and (18)F-NaF signals were associated with the presence of erosions, particularly progressive ones.

CONCLUSION

Our data show that both (18)F-FDG and (18)F-NaF PET signals were associated with RA-affected joints, especially those with ongoing erosive changes.

(18)F-NaF PET/CT: EANM procedure guidelines for bone imaging

The aim of this guideline is to provide minimum standards for the performance and interpretation of (18)F-NaF PET/CT scans. Standard acquisition and interpretation of nuclear imaging modalities will help to provide consistent data acquisition and numeric values between different platforms and institutes and to promote the use of PET/CT modality as an established diagnostic modality in routine clinical practice. This will also improve the value of scientific work and its contribution to evidence-based medicine.

Sodium 18F-fluoride PET/CT of bone, joint, and other disorders

The use of (18)F-sodium fluoride ((18)F-NaF) with PET/CT is increasing. This resurgence of an old tracer has been fueled by several factors including superior diagnostic performance over standard (99m)Tc-based bone scintigraphy, growth in the availability of PET/CT imaging systems, increase in the number of regional commercial distribution centers for PET radiotracers, the recent concerns about potential recurring shortages with (99m)Tc-based radiotracers, and the recent decision by the Centers for Medicare and Medicaid Services to reimburse for (18)F-NaF PET/CT for evaluation of patients with known or suspected bone metastases through the National Oncologic PET Registry. The major goal of this article is to review the current evidence on the diagnostic utility of (18)F-NaF in the imaging assessment of the bone and joint in a variety of clinical conditions.

Use of 18F-fluoride positron emission tomography as a predictor of the hip osteoarthritis progression

OBJECTIVE

The prediction of hip osteoarthritis (OA) progression is still a difficult issue. We have adopted (18)F-fluoride positron emission tomography (PET) for the evaluation of hip osteoarthritis, and investigated the prediction utility of (18)F-fluoride PET for both pain worsening and OA progression using a logistic regression model.

MATERIALS AND METHODS

A total of 57 hip joints were analyzed for progression risk factors for pain worsening and minimum joint space (MJS) narrowing by logistic regression analysis. Sex, age, BMI, existence of pain, the PET maximum standardized uptake value (SUV(max)), Kellgren and Lawrence grade, MJS, and follow-up period were used as explanatory variables. Receiver operating characteristic analysis was performed to calculate the cutoff value of the SUV(max).

RESULTS

Multivariate logistic regression analysis revealed significant differences only in the SUV(max) values for pain worsening and MJS narrowing. The odds ratio of the SUV(max) for pain worsening was 1.89, and for MJS narrowing it was 11.02. The SUV(max) cutoff value was 7.2 (sensitivity: 1.00, specificity: 0.84) for pain worsening and 6.4 (sensitivity: 0.92, specificity: 0.83) for MJS narrowing.

CONCLUSIONS

Our results indicate that the PET SUV(max) is a best predictor of pain worsening and MJS narrowing. This imaging modality has a great potential for the prediction of OA progression.

OARSI Clinical Trials Recommendations: Knee imaging in clinical trials in osteoarthritis

Significant advances have occurred in our understanding of the pathogenesis of knee osteoarthritis (OA) and some recent trials have demonstrated the potential for modification of the disease course. The purpose of this expert opinion, consensus driven exercise is to provide detail on how one might use and apply knee imaging in knee OA trials. It includes information on acquisition methods/techniques (including guidance on positioning for radiography, sequence/protocol recommendations/hardware for magnetic resonance imaging (MRI)); commonly encountered problems (including positioning, hardware and coil failures, sequences artifacts); quality assurance (QA)/control procedures; measurement methods; measurement performance (reliability, responsiveness, validity); recommendations for trials; and research recommendations.

OARSI Clinical Trials Recommendations: Hip imaging in clinical trials in osteoarthritis

Imaging of hip in osteoarthritis (OA) has seen considerable progress in the past decade, with the introduction of new techniques that may be more sensitive to structural disease changes. The purpose of this expert opinion, consensus driven recommendation is to provide detail on how to apply hip imaging in disease modifying clinical trials. It includes information on acquisition methods/techniques (including guidance on positioning for radiography, sequence/protocol recommendations/hardware for magnetic resonance imaging (MRI)); commonly encountered problems (including positioning, hardware and coil failures, artifacts associated with various MRI sequences); quality assurance/control procedures; measurement methods; measurement performance (reliability, responsiveness, and validity); recommendations for trials; and research recommendations.

Correlation between mechanical stress by finite element analysis and 18F-fluoride PET uptake in hip osteoarthritis patients

18F-fluoride positron emission tomography (18F-fluoride PET) is a functional imaging modality used primarily to detect increased bone metabolism. Increased 18F-fluoride PET uptake suggests an association between increased bone metabolism and load stress at the subchondral level. This study therefore examined the relationship between equivalent stress distribution calculated by finite element analysis and 18F-fluoride PET uptake in patients with hip osteoarthritis. The study examined 34 hips of 17 patients who presented to our clinic with hip pain, and were diagnosed with osteoarthritis or pre-osteoarthritis. The hips with trauma, infection, or bone metastasis of cancer were excluded. Three-dimensional models of each hip were created from computed tomography data to calculate the maximum equivalent stress by finite element analysis, which was compared with the maximum standardized uptake value (SUVmax) examined by 18F-fluoride PET. The SUVmax and equivalent stress were correlated (Spearman's rank correlation coefficient ρ=0.752), and higher equivalent stress values were noted in higher SUVmax patients. The correlation between SUVmax and maximum equivalent stress in osteoarthritic hips suggests the possibility that 18F-fluoride PET detect increased bone metabolism at sites of stress concentration. This study demonstrates the correlation between mechanical stress and bone remodeling acceleration in hip osteoarthritis.

Osteoarthritis year in review 2014: imaging

PURPOSE

This narrative review covers original publications related to imaging in osteoarthritis (OA) published in English between April 2013 and March 2014. In vitro data, animal studies and studies with less than 20 observations were not included.

METHODS

To extract relevant studies, an extensive PubMed database search was performed based on, but not limited to the query terms "Osteoarthritis" in combination with "MRI", "Imaging", "Radiography", "Ultrasound", "Computed Tomography" and "Nuclear Medicine". Publications were sorted according to relevance based on potential impact to the OA research community with the overarching goal of a balanced overview covering all aspects of imaging. Focus was on publications in high impact special interest journals. The literature will be presented in a methodological fashion covering radiography, ultrasound, compositional and morphologic Magnetic resonance imaging (MRI), and from an anatomic perspective including bone, muscle, meniscus and synovitis.

RESULTS AND CONCLUSIONS

Imaging research in OA in the last year was characterized by a strong focus on MRI-based studies dealing with epidemiological and methodological aspects of the disease. Ultrastructural tissue assessment specifically of cartilage and meniscus using compositional MRI is evolving further. Additional subsets of the large publicly available Osteoarthritis Initiative (OAI) MRI dataset are being analyzed at present and have been published with muscle analyses coming increasingly into the focus of the community. Bone parameters were evaluated using varying technology and a persistent interest in inflammatory disease manifestations has been noted. Other modalities than MRI have been less explored. To date most OA imaging research is still focused on the knee joint.

Normal SUV values measured from NaF18- PET/CT bone scan studies

Objectives

Cancer and metabolic bone diseases can alter the SUV. SUV values have never been measured from healthy skeletons in NaF18-PET/CT bone scans. The primary aim of this study was to measure the SUV values from normal skeletons in NaF18-PET/CT bone scans.

Methods

A retrospective study was carried out involving NaF18- PET/CT bone scans that were done at our institution between January 2010 to May 2012. Our excluding criteria was patients with abnormal real function and patients with past history of cancer and metabolic bone diseases including but not limited to osteoporosis, osteopenia and Paget’s disease. Eleven studies met all the criteria.

Results

The average normal SUV_max values from 11 patients were: cervical vertebrae 6.84 (range 4.38–8.64), thoracic vertebrae 7.36 (range 6.99–7.66), lumbar vertebrae 7.27 (range 7.04–7.72), femoral head 2.22 (range 1.1–4.3), humeral head 1.82 (range 1.2–2.9), mid sternum 5.51 (range 2.6–8.1), parietal bone 1.71 (range 1.3–2.4).

Conclusion

According to our study, various skeletal sites have different normal SUV values. SUV values can be different between the normal bones and bones with tumor or metabolic bone disease. SUV can be used to quantify NaF-18 PET/CT studies. If the SUV values of the normal skeleton are known, they can be used in the characterization of bone lesions and in the assessment of treatment response to bone diseases.

Factors Affecting Uptake of NaF-18 by the Normal Skeleton

Background

The primary aim of this study was to examine if factors such as renal function, height, weight and age could affect the uptake of sodium fluoride-18 (NaF-18) by the normal bone. This is the first study to examine the possible factors that can influence NaF-18 uptake in the normal bone.

Methods

A retrospective study was done on NaF-18 PET/CT bone scans from January 2010 to May 2012 at our institution. All NaF-18 PET/CT studies used the same clinical protocol. Our excluding criteria were patients with abnormal renal function and patients with past history of cancer and metabolic bone diseases. Spearman’s correlation was used to analyze the data.

Results

From our study (n = 11 patients), no correlation was found between SUV_max and serum creatinine and between SUV_max and age. However, significant correlations were found between SUV_max and height (cm) and between SUV_max and weight (kg) for thoracic 5, 7, 12 and lumbar 2 vertebral levels.

Conclusion

Based on our findings, SUV_max values in NaF-18 PET/CT bone scans can vary depending on the patient’s height, weight and bone region. This information can be helpful in diagnosing and monitoring bone pathologies and can help explain the clinical findings.