No difference in cerebral perfusion between the wild-type and the 5XFAD mouse model of Alzheimer's disease.

Neuroimaging with [2,2-dimethyl-3-[(2R,3E)-3-oxidoiminobutan-2-yl]azanidylpropyl]-[(2R,3E)-3-hydroxyiminobutan-2-yl]azanide;oxo(99Tc)technetium-99(3+) ([99mTc]HMPAO) single photon emission computed tomography (SPECT) is used in Alzheimer's disease (AD) to evaluate regional cerebral blood flow (rCBF). Hypoperfusion in select temporoparietal regions has been observed in human AD. However, it is unknown whether AD hypoperfusion signatures are also present in the 5XFAD mouse model. The current study was undertaken to compare baseline brain perfusion between 5XFAD and wild-type (WT) mice using [99mTc]HMPAO SPECT and determine whether hypoperfusion is recapitulated in 5XFAD mice. 5XFAD and WT mice underwent a 45 min SPECT scan, 20 min after [99mTc]HMPAO administration. Whole brain and regional standardized uptake values (SUV) and regional relative standardized uptake values (SUVR) with whole brain reference were compared between groups. Brain perfusion was similar between WT and 5XFAD brains. Whole brain [99mTc]HMPAO retention revealed no significant difference in SUV (5XFAD, 0.372 ± 0.762; WT, 0.640 ± 0.955; p = 0.536). Similarly, regional analysis revealed no significant differences in [99mTc]HMPAO metrics between groups (SUV: 0.357 ≤ p ≤ 0.640; SUVR: 0.595 ≤ p ≤ 0.936). These results suggest apparent discrepancies in rCBF between human AD and the 5XFAD model. Establishing baseline perfusion patterns in 5XFAD mice is essential to inform pre-clinical diagnostic and therapeutic drug discovery programs.

Positron Emission Tomography/Computerized Tomography in Newly Diagnosed Patients with Giant Cell Arteritis Who Are Taking Glucocorticoids.

OBJECTIVE: Large vessel uptake on positron emission tomography/computerized tomography (PET/CT) supports the diagnosis of giant cell arteritis (GCA). Its value, however, in patients without arteritis on temporal artery biopsy and in those receiving glucocorticoids remains unknown. We compared PET/CT results in GCA patients with positive (TAB+) and negative temporal artery biopsies (TAB-), and controls. METHODS: Patients with new clinically diagnosed GCA starting treatment with glucocorticoids underwent temporal artery biopsy and PET/CT. Using a visual semiquantitative approach, 18F-fluorodeoxyglucose (FDG) uptake was scored in 8 vascular territories and summed overall to give a total score in patients and matched controls. RESULTS: Twenty-eight patients with GCA and 28 controls were enrolled. Eighteen patients with GCA were TAB+. Mean PET/CT scores after an average of 11.9 days of prednisone were higher in patients with GCA compared to controls, for both total uptake (10.34 ± 2.72 vs 7.73 ± 2.56; p = 0.001), and in 6 of 8 specific vascular territories. PET/CT scores were similar between TAB+ and TAB- patients with GCA. The optimal cutoff for distinguishing GCA cases from controls was a total PET/CT score of ≥ 9, with an area under the receiver-operating characteristic curve of 0.75, sensitivity 71.4%, and specificity 64.3%. Among patients with GCA, these measures correlated with greater total PET/CT scores: systemic symptoms (p = 0.015), lower hemoglobin (p = 0.009), and higher platelet count (p = 0.008). CONCLUSION: Vascular FDG uptake scores were increased in most patients with GCA despite exposure to prednisone; however, the sensitivity and specificity of PET/CT in this setting were lower than those previously reported.

Spectrum of CT Findings in Thoracic Extranodal Non-Hodgkin Lymphoma.

Non-Hodgkin lymphoma (NHL) frequently manifests in extranodal structures in the chest, often in the form of secondary involvement but occasionally as primary disease. Because staging and treatment are affected by the presence of extranodal disease at imaging, radiologists' interpretation and management of suspicious findings are critical to patient care. Unfortunately, owing to considerable imaging overlap with other diseases, primary extranodal lymphoma is difficult to diagnose with imaging alone. Radiologists should have a heightened degree of suspicion in patients at risk (including patients with immune compromise, autoimmune diseases, or a history of stem cell or solid organ transplant) or with particular imaging appearances (including the vertebral wraparound sign, nonresolving consolidation, an infiltrative soft-tissue mass, and lesions demonstrating vascular encasement without invasion). For patients with known NHL, positron emission tomography/computed tomography (PET/CT) using fluorine 18 (18F)-labeled fluorodeoxyglucose (FDG) is now preferred for routine staging in most cases. CT remains heavily used, and identification of subtle extranodal involvement with CT can be improved with use of intravenous contrast material and careful review of multiplanar images. Pericardial effusion, pleural soft tissue (even when mild), mass-like consolidation, perilymphatic nodularity, and new lytic bone lesions are particularly suggestive of secondary involvement in a patient with known NHL. Magnetic resonance imaging is a helpful problem-solving tool when equivocal findings would change staging and treatment. This comprehensive review illustrates the spectrum of CT manifestations of extranodal NHL in the chest, including the pleura, lung, airways, heart, pericardium, esophagus, chest wall, and breast. ©RSNA, 2017.

Myelofibrosis on F-18 FDG PET Imaging.

A 60-year-old male was referred for a positron emission tomography (PET) scan using F-18 fluoro-2-deoxyglucose (F-18 FDG) for evaluation of a right lung opacity identified on a computed tomography (CT) scan. The patient also had a history of idiopathic myelofibrosis. The PET scan revealed markedly increased uptake throughout the spleen and liver, which were massively enlarged. There was also significantly increased uptake diffusely throughout the bone marrow. These findings are a reflection of the patient's myelofibrosis.

Utility of 18F-FDG PET in evaluating cancers of lung.

PET has seen rapid progression in recent years, with applications in oncology leading the way. The glucose analog (18)F-FDG is the most commonly used PET radiopharmaceutical and has been shown to accumulate avidly in several different neoplasms, including cancers of the lung. The following discussion will review the physiologic basis for the uptake of (18)F-FDG in lung neoplasms and demonstrate the utility of (18)F-FDG PET in lung cancer. A brief review of other PET radiopharmaceuticals in lung cancer imaging, and dual-modality PET/CT scanners, will be presented. Upon completion of this article, the reader should be able to describe the pharmacokinetics of (18)F-FDG and discuss the efficacy of (18)F-FDG PET scans in the evaluation of solitary pulmonary nodules, disease staging, and monitoring response to therapy. Additionally, the reader should be able to compare (18)F-FDG PET with conventional anatomic imaging and describe some of the technical challenges of PET/CT fusion imaging.

2-Deoxy-2-[F-18]fluoro-D-glucose-positron emission tomography of the head and neck: an atlas of normal uptake and variants.

In the evaluation of tumors of the head and neck region, positron emission tomography (PET) using 2-deoxy-2-[F-18]fluoro-D-glucose (FDG) is increasingly playing a valuable clinical role. However, assessment of this region can be challenging because of the large number of structures in this area which may demonstrate physiologically increased uptake of FDG. Furthermore, these structures are generally small, and uptake patterns can be quite variable, rendering the head and neck region one of the most difficult areas of the body to assess with FDG-PET. To assist in this endeavor, a pictorial of normal FDG uptake, including commonly encountered variants, is presented.

Positron emission tomography with 18F-fluorodeoxyglucose to predict pathologic response after induction chemotherapy and definitive chemoradiotherapy in head and neck cancer.

BACKGROUND: Conventional imaging is limited in identifying persistent disease after organ-preserving therapy for patients with advanced squamous cell carcinoma of the head and neck (SCCHN). We studied the accuracy of positron emission tomography (PET) with (18)F-fluoro-2-deoxy-D-glucose (FDG-PET) in restaging disease in patients with SCCHN after they had undergone induction chemotherapy (ICT) followed by chemoradiotherapy (CRT). METHODS: Forty patients with advanced SCCHN were treated with ICT followed by CRT. FDG-PET imaging was performed to assess for residual cancer at the primary site and in nodal metastases. Two nuclear medicine physicians interpreted PET scans in random sequence. Test characteristics were calculated with pathologic analysis or clinical recurrence as the standard. RESULTS: After induction chemotherapy, PET imaging had a sensitivity of 100% and specificity of 65% for detecting persistent disease at the primary tumor site. After ICT and CRT were completed, the sensitivity and specificity of PET imaging were 67% and 53%, respectively, for detecting occult disease in cervical lymph nodes. CONCLUSIONS: FDG-PET imaging showed some correlation with pathologic response after ICT and CRT in patients with advanced SCCHN. The use of FDG-PET warrants further investigation in this setting.