Thyroid FDG uptake incidentally identified on FDG-PET/CT occurred at a frequency of 3.8%, with about half of focal and half of diffuse lesions. The risk of thyroid malignancy was 63.6% in lesions with focal uptake, whereas the majority of diffuse uptake cases represents chronic thyroiditis. More data are needed to elucidate the role of SUV in the differentiation of benign and malignant lesions.

Purpose Determine if the histology of a breast malignancy influences the appearance of untreated osseous metastases on FDG PET/CT. Methods This retrospective study was performed under IRB waiver. Our Hospital Information System was screened for breast cancer patients who presented with osseous metastases, who underwent FDG PET/CT prior to systemic therapy or radiation from 2009–2012. Patients with invasive ductal carcinoma (IDC), invasive lobular carcinoma (ILC), or mixed ductal/lobular (MDL) histology were included. Patients with history of other malignancies were excluded. PET/CT was evaluated, blinded to histology, to classify osseous metastases on a per patient basis as sclerotic, lytic, mixed lytic/sclerotic, or occult on CT, and record SUVmax for osseous metastases on PET. Results 95 patients met inclusion criteria (74 IDC, 13 ILC, and 8 MDL). ILC osseous metastases were more commonly sclerotic and demonstrated lower SUVmax than IDC metastases. For all IDC and MDL patients with osseous metastases, at least one was FDG-avid. For ILC, all patients with lytic or mixed osseous metastases demonstrated at least one FDG-avid metastasis; however, only 3 of 7 patients with sclerotic osseous metastases were apparent on FDG PET. Conclusions The histologic subtype of breast cancer affects the appearance of untreated osseous metastases on FDG PET/CT. In particular, non-FDG-avid sclerotic osseous metastases were more common in patients with ILC, than in those with IDC. Breast cancer histology should be considered when interpreting non-FDG-avid sclerotic osseous lesions on PET/CT, which may be more suspicious for metastases (rather than benign lesions) in patients with ILC.

Purpose To assess and compare the value of FDG-PET to combined 111In-labeled leukocyte/99mTc-sulfur colloid bone marrow (WBC/BM) imaging for diagnosing infection in hip and knee prostheses. Methods In this prospective study, patients with painful hip or knee arthroplasty, who were scheduled to undergo clinical and diagnostic evaluation for prosthesis revision were included. They have been studied by using FDG-PET and 111In-labeled leukocyte/99mTc-sulfur colloid bone marrow scan. This study was IRB approved and HIPAA compliant. All patients provided written informed consent. Results A total of 134 hip and 87 knee prostheses, suspected of being either infected or non-infectious loosening were evaluated. All 221 prostheses underwent FDG-PET, whereas both WBC/BM imaging and FDG-PET was performed in 88 prostheses. The initial analysis of data from the WBC/BM images demonstrated somewhat results compared to those of FDG-PET scans on 88 patients. Also, some patients were not willing to undergo both procedures and therefore participate in this study. Therefore, a decision was made to eliminate WBC/BM imaging from the procedures for the remainder of this research study. This decision was reached partly due to the significant radiation dose delivered from labeled WBC as well as safety issues related to preparing these labeled cells. Final diagnosis was based on microbiological examinations of the surgical specimens in 125 prostheses and joint aspirations combined with the clinical follow-up of 6 months or more in 86 prostheses. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of FDG-PET in hip prostheses were 81.8%, 93.1%, 79.4%, and 94.0%, respectively and in knee prostheses were 94.7%, 88.2%, 69.2%, and 98.4% respectively. The sensitivity, specificity, PPV, and NPV of WBC/BM imaging in hip prostheses were 38.5%, 95.7%, 71.4%, and 84.6%, respectively and in knee prostheses were 33.3%, 88.5%, 25.0%, and 92.0%, respectively. In those cases that underwent both FDG-PET and WBC/BM imaging, there was a trend (P=0.0625) towards a higher sensitivity for FDG-PET in hip prostheses, whereas other comparisons did not show any significant differences between the two imaging modalities. Conclusion Based on this study, the diagnostic performance of FDG-PET scan in detecting infection in painful hip and knee prostheses is optimal for routine clinical application. Considering the complexity and costs of WBC/BM imaging and related safety issues associated with this preparation, FDG-PET appears to be an appropriate alternative for assessing these patients.

Through the use of novel quantitative techniques, we were able to calculate GKI and demonstrate a significant increase in the entity of joint inflammation with advancing age. As degenerative disease is age-related and inflammation is implicated in its pathogenesis, our findings further support this association. These preliminary data suggest that this approach can potentially provide a means to objectively quantify the degree of inflammation in various joint disorders, and possibly in other knee degenerative/inflammatory diseases.

The objective of this prospective study was to compare the metabolic activity of the knee joints of a group of subjects with painful knees clinically (as recurrent joint pain, joint instability and functional limitations) consistent with osteoarthritis (OA) and those of another group of patients without such complaints, using FDG-PET imaging. A total of 97 subjects who participated in either painful joint prosthesis or diabetic foot research studies involving FDG-PET scans were asked to complete a knee pain questionnaire. The patients were asked whether they experienced pain in any joint, and if so, which joints were affected. A total of 18 knee joints without prosthesis were reported to be painful. The maximum SUVs (SUVmax) of the middle joint space and lateral synovial tissue of these 18 knees were measured and compared to those of a set of subjects with control asymptomatic knees. The average SUVmax of the middle part of the joint space in the painful knees was 1.35 ± 0.59, as compared to an average SUVmax value of 0.86 ± 0.14 in the control group (p = 0.0176). The average SUVmax of the synovium in the lateral part of the painful joints was 1.17 ± 0.49, as compared to 0.73 ± 0.31 in the control group (p = 0.0161). These data indicate that increased FDG uptake is associated with knee pain in OA patients, and that there is a positive relationship between the two parameters.

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