Evaluation of treatment effects in brain abscess with positron emission tomography: Comparison of fluorine-18-fluorodeoxyglucose and carbon-11-methionine

Positron emission tomography (PET) imaging is in common use preoperatively to clinically evaluate patients who present with central nervous system mass lesions. The usefulness of PET is also recognized as a method to detect intracranial tumorous lesions. A number of papers reportthat some inflammatory processes also showed the uptake of Fluorine-18-Fluorodeoxyglucose (FDG) and Carbon-11-Methionine (Met) tracers. We performed two PET studies before and after treatment in 4 patients with brain abscess. PET showed the uptake of both tracers to thebrain abscess before treatment. The area showing an increased uptake of Met corresponded closely to the enhanced area on both CT and MR images. FDG-PET visually showed an uptake of FDG in a small area corresponding to an enhanced lesion within the CT and MR images. After treatment the area of lesions became small on enhancement CT or MRI and both PET studies showed reduced lesion and decreased uptake. The mechanism of Met uptake in the inflammatory area may be related to the higher metabolic rate and the active transport of amino acids as well as disruption of the blood brain barrier. Furthermore, it appears that the mechanism of FDG uptake is also related to a higher metabolic rate and, in addition, is related to the increased density of inflammatory cells. PET studies, more directly, reflect the degree of inflammatory response in brain abscess than enhancement CT or MRI. Therefore, PET is useful in detecting the inflammatory lesion and assessing the clinical effects of antibiotics treatment on brain abscesses.     

Positron emission tomographic findings in a tuberculous brain abscess

Several case reports and studies have described the positron emission tomographic (PET) findings of intracranial tuberculomas and bacterial brain abscesses. However, to our knowledge, the PET pattern of a tuberculous brain abscess has not been previously described. We report the case of a diabetic heavy drinker with a left parietal tuberculous abscess. ¹⁸F-fluoro-2-deoxyglucose (FDG)-PET scans showed intense FDG uptake at the abscess periphery, where contrast enhancement was observed on a magnetic resonance image. FDG uptake was reduced within the abscess cavity and in the adjacent cerebral cortex. The possibility of a tuberculous brain abscess should be considered when FDG accumulates at the periphery of a ring-enhancing lesion in a chronically ill or immunocompromised patient.     

Systemic disseminated tuberculosis mimicking malignancy on F-18 FDG PET-CT

FDG PET-CT imaging is increasingly accepted as a modality for evaluation of many malignancies, but FDG also can be accumulated intensely by inflammatory lesions. We present a case of a 60-year-old woman with intermittent fever, chills, fatigue, and dyschezia. CT scans indicated colon carcinoma with thoracic and retroperitoneal lymph node metastases. Whole body FDG PET-CT was performed to confirm and stage the malignant disease and showed intense FDG uptake in those lesions. However, histopathology confirmed tuberculosis. The literature describing FDG accumulation in constitutional tuberculous lesions is sparse, and one must be aware of patterns of FDG accumulation in tuberculosis in the diagnosing malignancies.     

Synchronous Bronchioloalveolar and Squamous Cell Lung Cancer With Different 18F-FDG Avidity on PET/CT

ABSTRACT: We report a case of synchronous multiple primary lung cancer diagnosed by F-FDG PET/CT. A 78-year-old man underwent staging FDG PET/CT that demonstrated intense tracer uptake in the primary, and a second lesion with low uptake. Histopathologic evaluation revealed synchronous squamous cell and bronchioloalveolar carcinoma, representing 2 distinct primaries. FDG PET/CT may identify and diagnose synchronous multiple primary lung cancer on the basis of different morphologic and metabolic features of distinct tumor entities. Moreover, pulmonary lesions with low FDG avidity may still represent malignant disease, even in the context of biopsy-proven FDG-avid lung cancer.     

Diagnosis of pancreatic cancer using fluorine-18 fluorodeoxyglucose positron emission tomography (FDG PET) —Usefulness and limitations in “clinical reality”—

The present review will provide an overview of the literature concerning the FDG PET diagnosis of pancreatic cancer and a summary from our experience of 231 cases of pancreatic lesions. FDG PET can effectively differentiate pancreatic cancer from benign lesion with high accuracy. Newly-developed PET scanners can detect small pancreatic cancers, up to 7 mm in diameter, by their high resolution, which could make a great contribution to the early detection of resectable and potentially curable pancreatic cancers. FDG PET is useful and cost-beneficial in the pre-operative staging of pancreatic cancer because an unexpected distant metastasis can be detected by whole-body PET in about 40% of the cases, which results in avoidance of unnecessary surgical procedures. FDG PET is also useful in evaluation of the treatment effect, monitoring after the operation and detection of recurrent pancreatic cancers. However, there are some drawbacks in PET diagnosis. A relatively wide overlap has been reported between semiquantitative uptake values obtained in cancers and those in inflammatory lesions. As for false-positive cases, active and chronic pancreatitis and autoimmune pancreatitis sometimes show high FDG accumulation and mimic pancreatic cancer with a shape of focal uptake. There were 8 false negative cases in the detection of pancreatic cancer by FDG PET, up to 33 mm in diameter, mainly because of their poor cellularity in cancer tissues. In addition, there are 19% of cancer cases with a decline in FDG uptake from 1 hr to 2 hr scan. FDG PET was recently applied to and was shown to be feasible in the differential diagnosis of cystic pancreatic lesions, such as intraductal papillary mucinous tumor of the pancreas. Further investigations are required to clarify the clinical value of FDG PET in predicting prognosis of the pancreatic patients.     

A case of septic pulmonary embolism associated with renal abscess mimicking pulmonary metastases of renal malignancy

We report the case of a 46-year-old woman with acute febrile symptom who had multiple pulmonary nodules and a renal mass. She underwent ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) to find a hidden malignancy and the cause of her fever. FDG PET/CT images demonstrated a renal mass and multiple lung nodules with intense FDG uptake, which was suspicious of a renal malignancy with multiple pulmonary metastatic lesions. CT-guided biopsies of the pulmonary and renal lesions only showed chronic inflammatory infiltrates without evidence of malignancy. She was diagnosed with septic pulmonary embolism from a renal abscess. One month after antibiotic treatment, the follow-up chest and abdomen CT showed improvement of the lung and renal lesions. This is the first case demonstrating the FDG PET/CT finding of septic pulmonary embolism associated with renal abscess in the published literature.     

PET imaging of cerebral and pulmonary Nocardia infection

We report the case of a 69-year-old man who was suspected to have lung cancer with a single metastasis to the brain. Initial workup for neurologic and pulmonary symptoms demonstrated a ring-enhancing lesion in his right frontal lobe on MRI and a lung mass on CT. An F-18 fluorodeoxyglucose positron emission tomography (FDG PET) scan demonstrated marked glucose hypermetabolism in the lung and brain lesions with maximal standard uptake values (SUV) in both lesions of approximately 11. Biopsy of the brain mass revealed an abscess and cultures grew Nocardia. He was treated for nocardiosis, and a repeat CT of the chest in 2 months and MRI of the brain in 5 months showed nearly complete resolution of the lesions. Currently, there are few reported cases of PET evaluation of brain abscesses, particularly Nocardia. We discuss the appearance of brain infections on FDG PET scans in immunocompetent and immunocompromised patients.     

Comparison of (18)F-FDG, (131)I-Na, and (201)Tl in diagnosis of recurrent or metastatic thyroid carcinoma.

There are several reports about the usefulness of (18)F-FDG PET in thyroid cancer. However, few studies have compared FDG PET with (131)I and (201)Tl scintigraphy. The aim of this study was to evaluate the clinical significance of whole-body FDG PET in differentiated thyroid cancer and to compare the results with those obtained from (131)I and (201)Tl scintigraphy. METHODS: Whole-body FDG PET was performed on 32 patients (10 men, 22 women; age range, 30-77 y; mean age, 54 y) with differentiated thyroid cancer (5 cases of follicular cancer and 27 of papillary cancer) after total thyroidectomy. An overall clinical evaluation was performed, including cytology, thyroglobulin level, sonography, MRI, and CT, to allow a comparison with functional imaging results for each patient. Metastatic regions were divided into five areas: neck, lung, mediastinum, bone, and other. Multiple lesions in one area were defined as one lesion. The tumor-to-background ratio (TBR) was measured for the lesions that were positive for both (201)Tl uptake and FDG PET uptake. RESULTS: The number of lesions totaled 47. Forty-one (87%) were detected by all scintigraphic methods. FDG uptake was concordant with (131)I uptake in only 18 lesions (38%). FDG uptake was concordant with (201)Tl uptake in 44 lesions (94%). Only one lesion was negative for FDG uptake and positive for (201)Tl uptake, and two lesions were positive for FDG uptake and negative for (201)Tl uptake. A significant correlation was seen between the TBR of (201)Tl and that of FDG (r = 0.69; P<0.05). CONCLUSION: These data indicate that for detecting metastatic lesions, FDG PET and (131)I scintigraphy may provide complementary information, whereas FDG PET may provide results similar to those of (201)Tl scintigraphy. Thus, the combination of (131)I scintigraphy and FDG PET (or (201)Tl scintigraphy) is the method of choice for detecting metastatic thyroid cancer after total thyroidectomy.     

Value of whole-body FDG PET in management of lung cancer

18F-fluorodeoxyglucose (FDG) PET imaging provides physiologic and metabolic information that characterizes lesions that are indeterminate by CT. FDG PET imaging is sensitive to the detection of lung cancer in patients who have indeterminate lesions on CT, whereas low grade malignancy such as bronchioloalveolar carcinoma and carcinoid may be negative on FDG PET. The specificity of PET imaging is less than its sensitivity because some inflammatory processes, such as active granulomatous infections, avidly accumulate FDG. This possibility should be kept in mind in the analysis of PET studies of glucose metabolism aimed at differentiating malignant from benign solitary pulmonary nodules. FDG uptake is considered to be a good marker of cell differentiation, proliferative potential, aggressiveness, and the grade of malignancy in patients with lung cancer. FDG PET accurately stages the distribution of lung cancer. Several studies have documented the increased accuracy of PET compared with CT in the evaluation of the hilar and mediastinal lymphnode status in patients with lung cancer. Whole-body PET studies detect metastatic disease that is unsuspected by conventional imaging. Management changes have been reported in up to 41% of patients on the basis of the results of whole-body studies. Whole-body FDG PET is also useful for the detection of recurrence. Several studies have indicated that the degree of FDG uptake in primary lung cancer can be used as an independent prognostic factor. Thus, whole-body FDG PET is clinically very useful in the management of lung cancer.     

18F-FDG PET in characterizing adrenal lesions detected on CT or MRI.

The purpose of this study was to evaluate the ability of (18)F-FDG PET to characterize adrenal lesions in patients with proven or suspected cancers. METHODS: A retrospective analysis was performed on 50 adrenal lesions in 41 patients, whose PET scans were done to evaluate the primary or metastatic disease. CT had shown 50 adrenal lesions in 41 patients and MRI had revealed 13 lesions in 10 patients. There were 34 patients with proven malignancy (28 lung cancer, 3 thyroid cancer, 2 colorectal cancer, and 1 lymphoma) and 7 with lung nodules. Of the 50 lesions, 18 were eventually determined to be malignant either by histopathology (n = 7) or by follow-up (n = 11). The remaining 32 lesions were proven or assumed to be benign by histopathology (n = 4) or clinical follow-up (n = 28). Unlike previously published reports, PET was interpreted as positive if the uptake was equal to or greater than that of the liver. RESULTS: No malignant lesion yielded a negative result on PET. Most lesions (13/18) showed significantly higher FDG uptake than that of the liver. In the remaining 5 lesions (2 metastases from neuroendocrine tumor, 2 early metastases, and 1 necrotic metastasis), FDG uptake was equal to or slightly higher than that of the liver. Of the 32 benign lesions, there were 2 lesions with uptake equal to or slightly higher than that of the liver, 3 with uptake less than the liver but more than the background, and 27 with uptake of the background. MRI identified 3 of the 13 lesions as false-positives but FDG PET correctly identified all 3 as benign. The other 10 adrenal lesions accurately diagnosed by MRI were also characterized by PET. FDG PET for characterization of adrenal lesions showed a sensitivity of 100%, a specificity of 94%, and an accuracy of 96%. CONCLUSION: FDG PET showed excellent diagnostic performance in differentiating adrenal lesions detected on CT or MRI. Because FDG PET has the additional advantage of evaluating the primary lesions as well as metastases, it could be cost-effective and the modality of choice for the characterization of adrenal lesions, especially in patients with malignancy.     

18F-FDG PET/CT Findings in a Breast Cancer Patient with Concomitant Tuberculous Axillary Lymphadenitis

Although ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography (PET) is a sensitive modality for detecting a malignant lesion, increased ¹⁸F-FDG uptake is also seen in infected or inflammatory processes. Here, we report the case of a breast cancer patient with concomitant tuberculous axillary lymphadenitis that showed increased ¹⁸F-FDG uptake. A 39-year-old woman underwent preoperative ¹⁸F-FDG PET/computed tomography (CT) as a part of the work-up for right breast cancer. ¹⁸F-FDG PET/CT images showed a malignant lesion in the right breast with moderate ¹⁸F-FDG uptake, and multiple enlarged right axillary lymph nodes with intense ¹⁸F-FDG uptake. Subsequently, the patient underwent right mastectomy and right axillary lymph node dissection. Histopathological examination confirmed breast cancer and tuberculous lymphadenitis, and the patient was treated concomitantly with anti-tuberculous therapy.     

Combined C-11 methionine and F-18 FDG PET imaging in a case of neurosarcoidosis

PURPOSE: PET scanning of the brain with F-18 FDG and C-11 methionine (MET) is useful for characterizing brain lesions discovered at MRI or CT. Most positive PET scans indicate malignancy. However, this case report demonstrates positive F-18 FDG and C-11 MET PET scans in a patient with a nonmalignant condition, neurosarcoidosis. MATERIALS AND METHODS: We detail the history and evaluation of a 59-year-old woman who presented with ataxia. The patient's evaluation included a contrast-enhanced MRI followed by PET scanning of the brain with C-11 MET and of the brain and trunk with F-18 FDG. The patient subsequently underwent biopsy of a lesion as directed by MRI and PET. RESULTS: The MRI demonstrated multiple enhancing leptomeningeal lesions consistent with metastatic disease. PET with F-18 FDG and C-11 MET demonstrated lesions in both cerebellar hemispheres with F-18 FDG accumulation in the mediastinum and left hilum. Biopsy of a brain lesion directed by MRI and PET revealed sarcoidosis. CONCLUSIONS: In evaluating brain lesions, PET with F-18 FDG and C-11 MET can help localize the lesion best suited for biopsy. However, not all lesions that have increased uptake on C-11 MET or F-18 FDG PET are malignant. Granulomatous inflammatory diseases such as neurosarcoidosis should also be considered in the differential diagnosis.     

FDG PET in the evaluation of the aggressiveness of pulmonary adenocarcinoma: correlation with histopathological features

2-[Fluorine-18]fluoro-2-deoxy-d-glucose (FDG) uptake within the primary lesion correlates with survival on positron emission tomography (PET) studies of patients with non-small cell lung cancer. The more metabolically active the tumour, the worse the outcome. The aim of this study was to determine whether a correlation exists between aggressiveness as determined by pathology and the findings of FDG PET in pulmonary adenocarcinoma. Thirty-five patients with 38 adenocarcinomas of the lung were studied. All patients underwent thoracotomy within 4 weeks of the FDG PET study. For semiquantitative analysis, standardized uptake values (SUVs) were calculated. Patients were classified into high SUV (> or = 4.0) and low SUV (<4.0) groups. The degree of FDG uptake (SUVs) in primary lung lesions was correlated with the histopathological features of aggressiveness (pleural involvement, vascular invasion or lymphatic permeation). The mean SUV of aggressive adenocarcinomas (4.36+/-1.94, n = 22) was higher than that of non-aggressive ones (1.53+/-0.88, n = 16) (P < 0.0001). Tumours with a high FDG uptake have a significantly higher likelihood of aggressiveness than those with a low FDG uptake (P = 0.0004). Analysis by the Kaplan-Meier methods revealed that the groups had different prognoses (log-rank test, P = 0.0099). The high SUV group had a significantly worse prognosis. In conclusion, a correlation was seen between aggressiveness as determined by pathology and glucose metabolism as measured by FDG PET in adenocarcinoma of the lung. FDG PET may be used as a non-invasive diagnostic technique in measuring aggressiveness and prognosis in patients with pulmonary adenocarcinoma.     

Use of dual-point fluorodeoxyglucose imaging to enhance sensitivity and specificity

Positron emission tomography (PET) and positron emission tomography/computed tomography imaging with fluorodeoxyglucose (FDG) are widely used as a powerful evaluation modality in oncological nuclear medicine not only for detecting tumors but also for staging and for therapy monitoring. Nevertheless, there are numerous causes of FDG uptake in benign processes seen on PET images. In fact, the degree of FDG uptake is related to the cellular metabolic rate and the number of glucose transporters. FDG accumulation in tumors is due, in part, to an increased number of glucose transporters in malignant cells. However, FDG is not specific for neoplasms: a similar situation exists in inflammation; activated inflammatory cells demonstrate increased expression of glucose transporters. Therefore, there is growing interest in improving the specificity of FDG-PET in patients with cancer. Preliminary studies showed that in several neoplasms, the uptake of FDG continues to increase for hours after radiopharmaceutical injection, and this difference in the time course of FDG uptake could be useful to improve the accuracy of PET to distinguish benign lesions from malignant ones. Also in experimental cultures, dual-point acquisition (early at 40-60 minutes postinjection and delayed at 90-270 minutes) demonstrated that it is able to differentiate inflammatory from neoplastic tissue. In general, inflammatory tissue is expected to reduce FDG uptake as the time goes by, whereas the uptake in the neoplastic lesions is supposed to be increasing. There is evidence in the recent literature of the clinical usefulness of dual-time-point FDG-PET imaging in a wide variety of malignancies, including those of head and neck, lung, breast, gallbladder, cervix, liver, and in brain tumors. A lesion is likely to be malignant if the standard uptake value increases over time, whereas it is likely to be benign if the standard uptake value is stable or decreases. It is worth noting that in many of these studies, dual-time-point PET improved not only the specificity but also the sensitivity in assessing breast, pulmonary, liver, and other tumors because of increased lesion-to-background ratio, as a consequence of FDG washout from the surrounding normal tissues and increasing neoplastic uptake.     

18F-FDG PET/CT findings of pharyngeal tuberculosis

A 58-year-old woman with dysphagia and hoarseness underwent 18F-FDG PET/CT to detect the original lesion and disease spread. Bilateral cervical lymphadenopathy and abnormal FDG uptakes in the right tonsil and pharyngeal wall were demonstrated. CT and MRI confirmed the bilateral cervical lymphadenopathy and mucosal thickening in the pharyngeal wall. On the basis of these findings, biopsy sites were selected. Pharyngeal tuberculosis was diagnosed based on culture of the biopsy specimens. 18F-FDG PET/CT contributed to clinical management in this case by detecting tuberculous lesions and showing the extent of these lesions in one examination.     

Detection of liver metastases from pancreatic cancer using FDG PET.

We evaluated the potential of the glucose analog [18F]fluorodeoxyglucose (FDG) as a PET tracer for the hepatic staging in 168 patients designated for resective pancreatic surgery. METHODS: Metastatic liver disease was confirmed or excluded during surgery or with CT follow-up for at least 6 mo. Proven metastases were then retrospectively identified on preoperative CT (gold standard). Hepatic PET scans of all patients were interpreted blindly. Any focal FDG uptake was considered malignant. Both proven hepatic metastases and suspicious hepatic PET lesions were then compared, lesion by lesion, with CT. Standardized uptake values (SUV) and tumor-to-liver ratios (T/L) were determined for the most intense lesion of each patient. RESULTS: Sensitivity of FDG PET was 68% (15 of 22 patients). The lesion detection rate was 97% (28 of 29 metastases) for lesions >1 cm and 43% (16 of 37 metastases) for lesions < or = 1 cm. Specificity was 95% (138 of 146 patients). Six of eight patients with false-positive results had marked intrahepatic cholestasis (versus 3 of 15 patients with true-positive lesions), one had an infrahepatic abscess and one had a right basal pulmonary metastasis. The SUV and T/L were 4.6+/-1.4 and 2.3+/-1.1, respectively, for malignant lesions and 4.1+/-1.5 and 1.9+/-0.3, respectively, for false-positive lesions and therefore are of limited value. CONCLUSION: FDG PET provides reliable hepatic staging for lesions >1 cm. False-positive results are associated with the presence of marked intrahepatic cholestasis. For lesions < or = 1 cm, FDG PET can define malignancy in 43% of suspicious CT lesions in the absence of dilated bile ducts.     

F-18 FDG uptake in breast infection and inflammation

PURPOSE: Whole-body fluorine-18 fluorodeoxyglucose (F-18 FDG) positron emission tomography (PET) scanning has been useful in the management of breast cancer. However, F-18 FDG uptake sometimes has been associated with benign breast disease. Four cases are reported of F-18 FDG breast uptake caused by infectious or inflammatory mastitis that mimics malignant disease. METHODS AND RESULTS: Two women had F-18 FDG whole-body scans for the evaluation of a large breast mass after inconclusive results of ultrasonography. In both cases, intense focal F-18 FDG breast uptake was noted that mimicked breast cancer. Histologic examination showed, in one patient, chronic granulomatous infiltration that likely represented tuberculous mastitis, because she showed a good clinical response to empirical anti-tuberculous treatment. The second patient had lactational changes associated with acute inflammation, and the culture grew Staphylococcus aureus. The breast mass completely disappeared 3 weeks after a course of antibiotic treatment. The other two patients had staging F-18 FDG PET scans 1 and 12 months after lumpectomy for breast carcinoma to detect residual, recurrent, or metastatic disease. Both scans showed a ring-like uptake in the involved breast, with superimposed intense focal uptake suggesting tumor necrosis centrally and malignant foci peripherally. In both cases, histologic examination revealed hemorrhagic inflammation secondary to postsurgical hematomas and no evidence of malignancy. CONCLUSION: Acute or chronic infectious mastitis and postsurgical hemorrhagic inflammatory mastitis should be considered in patients who have a breast mass, especially those with a history of tenderness or surgery.     

FDG PET for esophageal cancer complicated by sarcoidosis mimicking mediastinal and hilar lymph node metastases: two case reports

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.     

F-18 FDG PET demonstration of a thyroid metastasis in a patient with colon cancer

A 51-year-old man with a history of surgical removal of sigmoid colon cancer underwent F-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) to search for distant metastases and/or local recurrence because the carcinoembryonic antigen level was elevated. F-18 FDG PET images showed increased focal FDG uptake in the left lobe of the thyroid. Computed tomography images showed thyroid tumor in the left lobe as well as F-18 FDG PET images. Thereafter he underwent thyroidectomy and the resected specimen was histopathlogically shown to have thyroid metastasis from colon cancer. F-18 FDG PET was useful to detect thyroid metastasis from colon cancer as well as the most frequently seen metastatic sites such as liver, lungs, and lymph nodes.     

髂腰肌病变的影像特点及临床特征

目的探讨髂腰肌疾病的影像表现及临床特征。方法回顾性分析96例经手术或病理证实的髂腰肌病变并复习文献。结果 35例恶性病变包括原发性肿瘤2例,转移性髂腰肌肿瘤33例。动脉期可见转移性肿瘤中75%(25/33)的病变强化低于周边肌肉,16%(5/33)的病灶强化高于周边肌肉,9%(3/33)的病灶可见环形强化。髂腰肌结核40例,其中2例合并髋关节结核,3例合并骶髂关节结核。非特异性髂腰肌脓肿11例,3例可见气液平面。腰大肌外伤5例及退行性病变5例。结论髂腰肌病变具有一定的影像学及临床特征,认识其有助于正确诊断。