Kimiteru Ito

Long fasting is effective in inhibiting physiological myocardial 18F-FDG uptake and for evaluating active lesions of cardiac sarcoidosis

BackgroundF-fluorodeoxyglucose (FDG) positron emission tomography (PET) is a promising modality for detecting active lesions of cardiac sarcoidosis (CS). However, determining whether 18F-FDG uptake in the myocardium is physiological is challenging due to metabolic shift in myocardial cells. Although methods for inhibiting physiological myocardial 18F-FDG uptake have been proposed, no standard methods exist. This study therefore aimed to compare the effect of an 18-h fast (long fasting (LF)) with heparin loading plus a 12-h fast (HEP) before 18F-FDG PET scan.MethodsWe analyzed the effects of LF and HEP on the inhibition of physiological myocardial 18F-FDG uptake in healthy subjects (18 in HEP and 19 in LF) and in patients with known or suspected CS (96 in HEP and 69 in LF). In CS, the lower uptake of 18F-FDG in the myocardium was evaluated. A visual four-point scale was used to assess myocardial 18F-FDG uptake in comparison with hepatic uptake (1 lower, 2 similar, 3 somewhat higher, 4 noticeably higher).ResultsMyocardial 18F-FDG uptake was 1.68 ± 1.06 in LF and 3.17 ± 1.16 in HEP in healthy subjects (p < 0.0001), whereas it was 1.48 ± 0.99 in LF and 2.48 ± 1.33 in HEP in CS patients (p < 0.0001). Logistic regression and regression trees revealed the LF was the most effective in inhibiting myocardial 18F-FDG uptake. In addition, serum free fatty acid levels on intravenous 18F-FDG injection were a possible biomarker.ConclusionsLF is effective in inhibiting myocardial 18F-FDG uptake, and consequently, it could be useful for evaluating active lesions of CS in 18F-FDG PET images.

FDG-PET for the diagnosis of fever of unknown origin: a Japanese multi-center study.

ObjectiveTo evaluate the clinical value of 2-[18F]fluoro-2-deoxy-d-glucose positron emission tomography (FDG-PET) for the diagnosis of fever of unknown origin (FUO), we performed a Japanese multi-center retrospective survey.MethodsA total of 81 consecutive patients with FUO who underwent FDG-PET at 6 institutions between July 2006 and December 2007 were retrospectively evaluated. FDG uptake was visually evaluated using a 4-grade scale. The efficacy of FDG-PET for the evaluation of FUO, the provision of additional diagnostic information, the clinical impact on therapeutic decisions (4-grade scale), and the diagnostic performance compared with the final diagnosis were evaluated.ResultsThe diagnostic results were analyzed according to 4 groups of final diagnoses: infection, arthritis/vasculitis/autoimmune/collagen disease (A/V), tumor/granuloma (T/G), and other/unknown (O/U). Sensitivity was highest in T/G, followed by infection, A/V and O/U [100%(7/7), 89%(24/27), 65%(11/17), 0%(0/1) respectively]. Clinical impact and mean FDG score showed the same tendency. Additional information was highest in infection followed by T/G, A/V, and O/U [76%(22/29), 75%(6/8), 43%(9/21), 23%(5/22), respectively]. The O/U group showed a high specificity (84%, 16/19) and accurately excluded active focal inflammatory diseases and malignancy. The use of steroids for the treatment of fever seemed to mask the lesions and modified the results, especially in the A/V group (4 false negatives in 8 steroid users out of 21 A/V patients). The prevalence of each disease in each hospital significantly affected the effectiveness of FDG-PET for the diagnosis of FUO. The mean FDG uptake score and additional information (70%, 31/44 vs. 30%, 11/37, respectively) in national hospital (NH) was significantly higher than in university hospitals (UH). A Grade 3 clinical impact, in which the FDG PET results changed the clinical decision, was seen in 50% (22/44) of the patients in the NH group and 13.5% (5/37) of the patients in the UH group. The sensitivity (91%, 30/33; 63%, 12/19) and specificity (60%, 6/10; 86%, 12/14) of the results in the NH and UH groups differed. The total sensitivity was 81% (42/52), specificity was 75% (18/24). The NH group included a large number of cases with infectious diseases (50%, 23/44), while the UH group included a large number of A/V cases (38%, 14/37) and O/U cases (41%, 15/37).ConclusionFDG-PET for the diagnosis of FUO provided additional diagnostic information and had a high clinical impact, especially among patients with infectious diseases. It was also helpful in cases with unknown or other miscellaneous diseases by allowing the exclusion of focally active diseases. The prevalence of diseases in hospitals significantly affected the effectiveness of FDG-PET for the diagnosis of FUO. FDG-PET is a useful examination providing various degrees of clinical impact for the management of FUO, depending on the characteristics of the patient and the hospital.

FDG PET for rheumatoid arthritis: basic considerations and whole-body PET/CT

[18F]Fluorodeoxyglucose (FDG) is a tracer for glucose metabolism. Its distribution is not specific to cancer cells but is also observed in inflammatory tissue, including macrophages, capillaries, and fibroblasts. Rheumatoid arthritis (RA) is a systemic, chronic inflammation of the joints resulting in synovitis. The disease is characterized by fibrovascular proliferation leading to the formation of a pannus and causing high FDG uptake. Several clinical studies of RA have demonstrated that FDG uptake in affected joints reflects the disease activity of RA, with strong correlations between uptake and various clinical parameters having been noted. Furthermore, the use of FDG PET for the sensitive detection and monitoring of the response to RA therapy has been reported. FDG PET/computed tomography (CT) enables the detailed evaluation of disease in large joints throughout the whole body, which is a unique advantage of PET/CT. FDG PET/CT can also be used to detect high‐risk disease complications, such as atlanto‐axial joint involvement, at an early stage. The possible contribution of FDG PET to the management of patients with RA remains to be studied in detail.

Effects of blood glucose level on FDG uptake by liver: a FDG-PET/CT study

UNLABELLED In FDG-PET for abdominal malignancy, the liver may be assumed as an internal standard for grading abnormal FDG uptake both in early images and in delayed images. However, physiological variables of FDG uptake by the liver, especially the effects of blood glucose level, have not yet been elucidated. METHODS FDG-PET studies of 70 patients examined at 50 to 70 min after injection (60 ± 10 min: early images) and of 68 patients examined at 80 to 100 min after injection (90 ± 10 min: delayed images) were analyzed for liver FDG uptake. Patients having lesions in the liver, spleen and pancreas; patients having bulk tumor in other areas; and patients early after chemotherapy or radiotherapy were excluded; also, patients with blood glucose level over 125 mg/dl were excluded. RESULTS Mean standardized uptake value (SUV) of the liver, blood glucose level and sex showed no significant differences between early images and delayed images. However, liver SUV in the delayed image showed a larger variation than that in the early image and showed significant correlation to blood glucose level. The partial correlation coefficient between liver SUV and blood glucose level in the delayed image with adjustment for sex and age was 0.73 (P < .0001). Multivariate regression coefficient (95% confidence interval) of blood glucose was 0.017 (0.013-0.021). CONCLUSION Blood glucose level is an important factor affecting the normal liver FDG uptake in nondiabetic patients. In the case of higher glucose level, liver FDG uptake is elevated especially in the delayed image. This may be due to the fact that the liver is the key organ responsible for glucose metabolism through gluconeogenesis and glycogen storage.

Evaluation of Wegener’s granulomatosis using 18F-fluorodeoxyglucose positron emission tomography/computed tomography

ObjectiveWegener’s granulomatosis (WG) is a relatively rare disease characterized by granulomatous necrotizing vasculitis that primarily involves small- and medium-sized vessels. Systemic findings observed on 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) have not been well reported. The purpose of this study was to evaluate the FDG PET/CT imaging in the diagnosis and follow-up of patients with WG.Materials and methodsThirteen FDG PET/CT images obtained for 8 patients (2 men and 6 women) with WG were retrospectively analyzed. Of these, 6 were performed for diagnosis, 2 for restaging and follow-up, and 5 for assessment of treatment efficacy. Maximum standardized uptake values (max SUVs) and visual analyses were used to interpret the FDG PET/CT images. In addition, nonenhanced CT findings obtained during FDG PET/CT were described.ResultsWG lesions of the upper respiratory tract and lung were more clearly detected by FDG PET/CT fusion imaging than by nonenhanced CT alone, and all of the active lesions showed decreased FDG uptake after treatment. In addition, FDG PET/CT can provide complementary information to indicate biopsy site based on FDG uptakes.ConclusionsFDG PET/CT is a feasible modality for evaluating lesion activities, therapeutic monitoring, and follow-up of WG. Furthermore, biopsy sites of WG lesions may be determined by FDG PET/CT.

Abnormalities of cerebral blood flow in multiple sclerosis: A pseudocontinuous arterial spin labeling MRI study

Arterial spin labeling (ASL) is a noninvasive technique that can measure cerebral blood flow (CBF). To our knowledge, there is no study that examined regional CBF of multiple sclerosis (MS) patients by using this technique. The present study assessed the relationship between clinical presentations and functional imaging data in MS using pseudocontinuous arterial spin labeling (pCASL). Twenty-seven patients with MS and 24 healthy volunteers underwent magnetic resonance imaging and pCASL to assess CBF. Differences in CBF between the two groups and the relationships of CBF values with the T2-hyperintense volume were evaluated. Compared to the healthy volunteers, reduced CBF was found in the bilateral thalami and right frontal region of the MS patients. The volume of the T2-hyperintense lesion was negatively correlated with regional CBF in some areas, such as both thalami. Our results suggest that demyelinated lesions in MS mainly have a remote effect on the thalamus and that the measurement of CBF using ASL could be an objective marker for monitoring disease activity in MS.

(18)F-FDG-PET/CT findings of granulocyte colony stimulating factor (G-CSF)-producing lung tumors.

Tumors producing granulocyte colony stimulating factor (G-CSF), malignant lung tumors in most cases, are rare, and patients present with abnormal elevations of the white blood cell (WBC) count in the absence of any infectious disease. We present the 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG-PET/CT) imaging findings of two cases of G-CSF-producing tumor. PET-CT showed abnormally high uptake of 18F-FDG not only by the tumor itself but also diffusely throughout the bone marrow. Following resection of the tumor, the blood G-CSF level as well as the WBC count dropped down to normal range in both cases. Histopathological examination of the resected tumor specimens revealed the presence of an enormous number of inflammatory cells within the tumors and positive immunostaining of the tumor cells for G-CSF. The 18F-FDG-PET/CT findings could be explained by the elevated bone marrow metabolism associated with the excessively active production of granulocytes under G-CSF stimulation, and the 18F-FDG uptake by the inflammatory cells also contributing to the total tumor uptake of 18F-FDG. These characteristic imaging findings are expected to be useful for the diagnosis of G-CSF-producing tumors.

Differentiation of Brain Tumor Recurrence from Post-Radiotherapy Necrosis with 11C-Methionine PET: Visual Assessment versus Quantitative Assessment

Purpose The aim of this multi-center study was to assess the diagnostic capability of visual assessment in L-methyl-11C-methionine positron emission tomography (MET-PET) for differentiating a recurrent brain tumor from radiation-induced necrosis after radiotherapy, and to compare it to the accuracy of quantitative analysis. Methods A total of 73 brain lesions (glioma: 31, brain metastasis: 42) in 70 patients who underwent MET-PET were included in this study. Visual analysis was performed by comparison of MET uptake in the brain lesion with MET uptake in one of four regions (around the lesion, contralateral frontal lobe, contralateral area, and contralateral cerebellar cortex). The concordance rate and logistic regression analysis were used to evaluate the diagnostic ability of visual assessment. Receiver-operating characteristic curve analysis was used to compare visual assessment with quantitative assessment based on the lesion-to-normal (L/N) ratio of MET uptake. Results Interobserver and intraobserver κ-values were highest at 0.657 and 0.714, respectively, when assessing MET uptake in the lesion compared to that in the contralateral cerebellar cortex. Logistic regression analysis showed that assessing MET uptake in the contralateral cerebellar cortex with brain metastasis was significantly related to the final result. The highest area under the receiver-operating characteristic curve (AUC) with visual assessment for brain metastasis was 0.85, showing no statistically significant difference with L/Nmax of the contralateral brain (AUC = 0.89) or with L/Nmean of the contralateral cerebellar cortex (AUC = 0.89), which were the areas that were the highest in the quantitative assessment. For evaluation of gliomas, no specific candidate was confirmed among the four areas used in visual assessment, and no significant difference was seen between visual assessment and quantitative assessment. Conclusion The visual assessment showed no significant difference from quantitative assessment of MET-PET with a relevant cut-off value for the differentiation of recurrent brain tumors from radiation-induced necrosis.

Usefulness of SWI for the Detection of Iron in the Motor Cortex in Amyotrophic Lateral Sclerosis

The purpose of the present retrospective study was to evaluate the sensitivity of susceptibility‐weighted imaging (SWI) compared to conventional spin‐echo T2‐weighted and T2*‐weighted images in detecting iron deposition in the motor cortex of amyotrophic lateral sclerosis (ALS) patients in comparison with age‐matched normal controls. We also investigated the etiology of the low signal referring to the pathology of one autopsy case.

Kikuchi disease: 18F-FDG positron emission tomography/computed tomography of lymph node uptake.

PurposeThis study evaluated 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) findings in patients with Kikuchi disease (KD), or histiocytic necrotizing lymphadenitis.Materials and methodsWe evaluated the 18F-FDG PET/ CT findings of seven patients (one man, six women) with KD, ranging in age from 23 to 66 years (mean 36 years). All the patients had been diagnosed based on the pathological findings of a biopsy and clinical course.ResultsThe maximum standard uptake values (SUVmax) of FDG uptake in affected lymph nodes were 2.05–13.94 (mean ± SD, 6.25 ± 3.32). In all the patients but two, the lymph nodes with the SUVmax were located in the neck. All the lymph nodes had a diameter of <30 mm. In nonneck regions, the SUVs of the swollen lymph nodes tended to indicate lower uptake.ConclusionFDG-PET/CT was capable of visualizing general regions containing lymph nodes and was useful for making clinical decisions as to biopsy sites. Together with the physical findings, consideration of the distribution and size of the affected lymph nodes, as shown using FDG-PET/CT, may be useful for suggesting the possibility of KD. KD should be considered in the differential diagnosis of FDG-avid lymph node lesions.