F-18 fluoride PET/CT in the detection of radiation-induced pelvic insufficiency fractures

Novel Musculoskeletal and Orthopedic Applications of 18F-Sodium Fluoride PET

PET imaging with ¹⁸F-sodium fluoride (NaF), combined with computed tomography or magnetic resonance, is a sensitive method of assessing bone turnover. Although NaF-PET is gaining popularity in detecting prostate cancer metastases to bone marrow, osseous changes represent secondary effects of cancer cell growth. PET tracers more appropriate for assessing prostate cancer metastases directly portray malignant activity and include ¹⁸F-fluciclovine and prostatic specific membrane antigen ligands. Recent studies investigating NaF-PET suggest utility in the assessment of benign musculoskeletal disorders. Emerging applications in assessing traumatic injuries, joint disease, back pain, orthopedic complications, and metabolic bone disease are discussed.

Differentiating between Alzheimer's disease, amnestic mild cognitive impairment, and normal aging via diffusion kurtosis imaging

Diffusion kurtosis imaging can be used to assess pathophysiological changes in tissue structure and to diagnose central nervous system diseases. However, its sensitivity in assessing hippocampal differences between patients with Alzheimer's disease and those with amnestic mild cognitive impairment has not been characterized. Here, we examined 20 individuals with Alzheimer's disease (11 men and 9 women, mean 73.2 ± 4.49 years), 20 with amnestic mild cognitive impairment (10 men and 10 women, mean 71.55 ± 4.77 years), and 20 normal controls (11 men and 9 women, mean 70.45 ± 5.04 years). We conducted diffusion kurtosis imaging, using a 3.0 T magnetic resonance scanner, to compare hippocampal differences among the three groups. The results demonstrated that the right hippocampal volume and bilateral mean kurtosis were remarkably smaller in individuals with Alzheimer's disease compared with those with amnestic mild cognitive impairment and normal controls. Further, the mean kurtosis was lower in the amnestic mild cognitive impairment group compared with the normal control group. The mean diffusion in the left hippocampus was lower in the Alzheimer's disease group than in the amnestic mild cognitive impairment and normal control groups, while the mean diffusion in the right hippocampus was lower in the Alzheimer's disease group than in the normal control group. Fractional anisotropy was similar among the three groups. These results verify that bilateral mean kurtosis and mean diffusion are sensitive to the diagnosis of Alzheimer's disease and amnestic mild cognitive impairment. This study was approved by the Ethics Review Board of Affiliated Sixth People's Hospital of Shanghai Jiao Tong University, China on May 4, 2010 (approval No. 2010(C)-6).

Osteoid osteoma: multimodality imaging with focus on hybrid imaging

Osteoid osteoma is a painful, benign, osteoblastic lesion that occurs in younger patients and affects the extremities or the axial skeleton. While plain film findings may suggest the diagnosis, in complex anatomical regions such as the spine, pelvis, wrist and foot advanced imaging modalities are often required. A typical nidus surrounded by sclerosis or cortical thickening characterizes osteoid osteoma on plain radiography and CT. MR is the cross-sectional imaging modality of choice for most musculoskeletal disorders. Unfortunately, extensive accompanying bone marrow oedema, soft-tissue alterations, difficulty detecting the nidus, and lesion locations close to a joint (with reactive arthritis) may make a confident diagnosis of osteoid osteoma by MR imaging difficult. Hybrid imaging with bone-seeking tracers such as SPECT/CT with ^99mTc-labelled bisphosphonates or PET/CT with ¹⁸F-labelled sodium fluoride (¹⁸F-NaF) combines high radionuclide uptake with morphological details and provides accurate diagnosis of osteoid osteoma and additional information for treatment planning. FDG is not the recommended PET tracer because osteoid osteoma is normally FDG-negative, although some osteoid osteomas may show increased FDG uptake. Osteoblastoma, Brodie's abscess and stress fractures may mimic osteoid osteoma on imaging and clinical presentation. Once identified as the pain generator, destruction of the osteoid osteoma nidus by ablation or resection techniques usually leads to complete healing. Image-guided drill excision and radiofrequency ablation are widely used interventions. We review the presentation of osteoid osteoma across all imaging modalities, with special focus on hybrid imaging techniques.

Diagnosis and Monitoring of Osteoporosis With 18F-Sodium Fluoride PET: An Unavoidable Path for the Foreseeable Future

The prevalence of metabolic bone diseases particularly osteoporosis and its precursor, osteopenia, continue to grow as serious global health issues today. On a worldwide perspective, 200million people suffer from osteoporosis and in 2005, over 2million fracture incidents were estimated due to osteoporosis in the United States. Currently, osteoporosis and other metabolic bone diseases are evaluated primarily through dual energy X-ray absorptiometry, and rarely by bone biopsy with tetracycline labeling or Technetium-99m (^99mTc) based bone scintigraphy. Deficiencies in these methods have prompted the use of more precise methods of assessment. This review highlights the use of ¹⁸F-sodium fluoride (NaF) with PET (NaF-PET), NaF-PET/CT, or NaF-PET/MRI in the evaluation of osteoporosis and osteopenia in the lumbar spine and hip. This imaging modality provides a molecular perspective with respect to the underlying metabolic alterations that lead to osseous disorders by measuring bone turnover through standardized uptake values. Its sensitivity and ability to examine the entire skeletal system make it a more superior imaging modality compared to standard structural imaging techniques. Further research is needed to determine its accuracy in reflecting the efficacy of therapeutic interventions in metabolic bone diseases.

18F sodium fluoride PET/CT detects osseous metastases from breast cancer missed on FDG PET/CT with marrow rebound

Intense FDG uptake by bone marrow following recent chemotherapy limits evaluation for osseous metastases. The impact of marrow rebound on accuracy of (18)F-fluoride PET/CT is unclear. A 73-year-old woman with breast cancer presented for restaging FDG PET/CT, which showed intense activity throughout almost the entire axial skeleton and no osseous metastases. An (18)F-fluoride PET/CT performed 7 days later identified multiple osseous metastases in the spine, ribs, and pelvis. This case demonstrates that (18)F-fluoride PET/CT should be considered for the evaluation of osseous metastases in patients with rebound marrow uptake on FDG PET/CT.

(18)F NaF PET/CT Versus Conventional Bone Scanning in the Assessment of Benign Bone Disease

Nuclear physicians in many centers nowadays have the choice of using different nuclear bone-imaging modalities. (18)F-labeled sodium fluoride (NaF) PET with computed tomography (PET/CT) is a promising tool for the evaluation of benign bone disease. The indications for NaF PET/CT in clinical practice are probably the same as those established for (99m)Tc-labeled methylene diphosphonate bone scintigraphy and single-photon emission computed tomography (SPECT)/CT. At present only preliminary data, often with a limited number of patients and lacking comparison with (99m)Tc-MDP SPECT/CT, are available. This article reviews the available literature and summarizes the authors' experience with NaF PET/CT in benign bone disease.