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Objective: In clinical positron emission tomography (PET) studies for oncology, it is occasionally required to differentiate a diffuse increase in bone marrow (BM) F-18 fluoro-2-deoxyglucose (FDG) uptake due to the involvement of malignancy or hematopoietic disease and that due to the administration of hematopoietic cytokines, an inflammation reaction, or stimulation by some types of malignancy. The objectives of this study were to clarify the relationships between BM F-18 FDG uptake and blood parameters as well as age, and also to determine the degree of F-18 FDG accumulation that constitutes an abnormal level referring to blood parameters., Methods: Records of 65 patients, 32 with benign diseases and 33 with malignancies without metastasis in bone and liver until a half year after the PET examination, were analyzed retrospectively. Regions of interest were placed on the liver and the lower thoracic and lumbar vertebrae to measure the standardized uptake value (SUV), and vertebral SUVs were averaged as the BM SUV(mean). The BM SUV(mean) was divided by the liver SUV to calculate the BM/liver ratio. The relationships among the BM SUV(mean), or BM/liver ratio, and blood parameters and age were tested using multiple regression analysis., Results: In both patients with and without malignancy, a multiple regression model using the BM/liver ratio showed a higher coefficient of determination value than that using the BM SUV(mean), indicating that the correction by the liver SUV reduced the interindividual variation in the BM SUV(mean). The BM/liver ratio was negatively correlated with age (beta = -0.41 and -0.43, respectively) and positively correlated with serum C-reactive protein (CRP) level (beta = 0.39 and 0.46, respectively) in both groups of patients. Every patient with benign disease who had a ratio greater than or equal to 1 had an increased CRP level., Conclusions: The BM F-18 FDG uptake depends on the patient's age and serum CRP level, both with and without malignancy. A BM F-18 FDG uptake greater than or equal to that of the liver may indicate BM activation.

Objective: The dependent-density of computed tomography (CT) images of positron emission tomography (PET)/CT is sometimes difficult to distinguish from chronic interstitial lung disease (ILD) when it accompanies increased (18)F-fluorodeoxy-D: -glucose ((18)FDG) uptake. Though the possible utility of (18)FDG-PET for the diagnosis of active ILD has been reported, the clinical relevance of mild lung (18)FDG uptake in ILD cases without signs and symptoms suggesting acute progression has not been described. This study aimed to test relationships between (18)FDG uptake and lung density on CT using PET/CT in patients with normal lung as well as clinically stable chronic ILD., Methods: Thirty-six patients with normal lungs (controls) and 28 patients with chronic ILD (ILD cases) without acute exacerbation were retrospectively selected from (18)FDG-PET/CT scans performed in examination of malignant neoplasms. Elliptical regions of interest (ROIs) were placed on the lung. The relationships between CT density and (18)FDG uptake between the control and ILD cases were tested., Results: The CT density and (18)FDG uptake had a linear correlation in both the controls and the ILD cases without a difference in their regression slopes, and they were overlapped between the controls and the ILD cases with higher mean values in the ILD cases., Conclusions: Lung (18)FDG uptake was considered to reflect a gravity-dependent tissue density in the normal lung. Though the lung (18)FDG uptake as well as the CT density tended to be higher in chronic ILD patients, it may be difficult to distinguish them in normal dependent regions from those related to chronic ILD in some cases.

This report documents 2 cases of esophageal cancer complicated by sarcoidosis mimicking mediastinal lymph node metastases on F-18 fluorodeoxyglucose positron emission tomography (FDG PET) for staging of the cancer. In both cases, FDG PET demonstrated intense uptake in the swollen mediastinal and bilateral hilar lymph nodes. In 1 case, FDG PET showed intense uptake in the primary esophageal cancer. In another case, FDG PET showed no definite intense uptake in the primary esophageal cancer. The histopathology of the resected mediastinal and hilar lymph nodes demonstrated no malignant cells but sarcoid lesions such as noncaseating granuloma. Therefore, sarcoidosis should be considered when FDG PET shows intense FDG uptake in nonregional swollen lymph nodes, although the incidence of esophageal cancer complicated by sarcoidosis is rare.

The vertebral spine is frequently affected by the SAPHO (synovitis, acne, pustulosis, hyperostosis, and osteitis) syndrome. We report the collective imaging findings of hybrid F-18 fluorodeoxyglucose-positron emission tomography/computed tomography (18FDG-PET/CT), as well as bone scans and magnetic resonance imaging, in a patient who had suspected metastatic vertebral bone tumors. 18FDG-PET/CT can be utilized to exclude metastatic vertebral tumors, as well as identifying stable lesions, by demonstrating active inflammatory lesions with accurate anatomic localization through the convergence of the functional information from 18FDG uptake with the anatomic information of CT.

We report a case demonstrating intense FDG uptake in the ovary, which was diagnosed to be a hemorrhage and congestion due to painless torsion. An asymptomatic retropelvic mass was detected in a 51-year-old female by echography. FDG-PET demonstrated intense uptake in the mass, thus suggesting an ovarian tumor. A resection of the tumor was performed, and histopathological examination revealed hemorrhage and congestion in the ovary due to ovarian torsion. An ovarian hemorrhage due to painless torsion should be considered in the differential diagnosis of intrapelvic masses demonstrating high FDG uptake, even in asymptomatic patients.

It is well known that hematopoietic cytokine stimulation can cause diffuse increase of FDG accumulation in bone marrow on PET imaging, which simulates that seen in patients with bone marrow metastases. However, diffuse bone marrow FDG uptake can be caused by other etiologies. We report 2 patients who did not have a history of hematopoietic cytokine stimulation. The FDG PET images showed diffuse bone marrow FDG uptake, and the patients were diagnosed as having myelodysplastic syndromes. These cases demonstrate that diffuse FDG uptake by bone marrow can suggest neoplastic disease of the hematopoietic tissues.

Objective: Positron emission tomography (PET) with fluorodeoxyglucose (FDG) is widely used for evaluation of cancer and ischemic heart disease. Recently, increased myocardial FDG uptake has been reported to be related to some types of heart disease, such as sarcoidosis. However, the physiological increased FDG uptake in the heart often mimics the abnormal high uptake in these cases. In this study, we investigated the relationships between myocardial uptake and age, blood glucose level, fasting period, and hospitalization status (inpatient vs. outpatient)., Methods: A total of 159 non-diabetic patients were enrolled in the present study. Patients were imaged on a PET/CT scanner, and a three-dimensional region of interest (ROI) was drawn on the fused PET/CT image to measure the maximum standardized uptake value (SUV(max)) of the whole left ventricle., Results: No significant relationships were observed between myocardial uptake and age or fasting period. Blood glucose level showed a significant relationship (p = 0.025) with myocardial uptake, but the R-square was extremely small (r2 = 0.03). With an SUV(max) threshold of 3.0, there was no significant difference between inpatients and outpatients. However, outpatients showed a significantly higher frequency of myocardial uptake over SUV(max) of 5.0 (chi2 test: p = 0.046)., Conclusion: It is difficult to predict the degree of physiological uptake in the heart from data regarding age, fasting period, or blood glucose level. Outpatients tend to show higher myocardial uptake than inpatients, which may make it difficult to detect abnormally increased uptake in the heart. A long fasting period, such as overnight fasting, is an inadequate means to reduce the physiological uptake of FDG in the heart.

Metastatic tumors or secondary lymphoma of the kidney are rare and can often be missed on conventional computed tomography (CT) imaging. On the other hand, many types of metastatic tumor or lymphoma can be detected clearly as hotspots of elevated uptake on FDG PET. However, excreted FDG present in the urinary tract mimics these findings and interferes with image reading. Careful investigation of the renal cortex by FDG PET and review of anatomical images, such as the findings of CT and MRI, have important roles in the detection of renal tumor. Here, we present three cases of solitary metastatic/secondary tumor of the kidney, and discuss the features of the lesions on FDG PET in comparison with their appearance on CT.