F-18]fluorodeoxyglucose positron emission tomography and positron emission tomography: computed tomography in recurrent and metastatic cholangiocarcinoma

OBJECTIVES: We retrospectively assessed the diagnostic utility of dedicated positron emission tomography (PET) and hybrid PET-computed tomography (CT) scans with [F-18]fluorodeoxyglucose (FDG) in the imaging evaluation of patients with known or suspected recurrent and metastatic cholangiocarcinoma. METHODS: The study group included 24 patients (13 males and 11 females; age range, 34-75 years) with known or suspected recurrent and metastatic cholangiocarcinoma. We performed 8 dedicated PET scans (Siemens 953/A, Knoxville, Tenn) in 8 patients and 24 hybrid PET-CT scans (Siemens Biograph, Knoxville, Tenn) in 16 patients. Four patients underwent both pretreatment and posttreatment scans. Nonenhanced CT transmission scans were obtained for attenuation correction after administration of oral contrast material. PET images were obtained 60 minutes after the intravenous administration of 15 mCi (555 MBq) FDG. Prior treatments included surgery alone in 12 patients, surgery and chemotherapy in 6 patients, and surgery and combined chemoradiation therapy in 6 patients. Diagnostic validation was conducted through clinical and radiologic follow-up (2 months to 8 years). RESULTS: PET and CT were concordant in 18 patients. PET-CT correctly localized a hypermetabolic metastatic lesion in the anterior subdiaphragmatic fat instead of within the liver and was falsely negative in intrahepatic infiltrating type cholangiocarcinoma. PET was discordant with CT in 6 patients. PET was negative in an enlarged right cardiophrenic lymph node on CT, which remained stable for 1 year. In 1 patient, PET-CT scan showed hypermetabolic peritoneal disease in the right paracolic gutter without definite corresponding structural abnormalities, which was subsequently confirmed on a follow-up PET-CT scan performed 6 months after the initial study, at which time peritoneal nodular thickening was evident on concurrent CT. PET-CT documented the progression of locally recurrent and metastatic disease in another patient based on interval appearance of several new hypermetabolic lesions and significant increase in the standardized uptake values of the known lesions despite little interval change in the size and morphologic character of lesions on concurrent CT. It was also helpful in excluding metabolically active disease in patients with contrast enhancement at either surgical margin of hepatic resection site or focally within hepatic parenchyma and in an osseous lesion. Overall, based on the clinically relevant patient basis for detection of recurrent and metastatic cholangiocarcinoma, the sensitivity and specificity of PET (alone and combined with CT) were 94% and 100% and, for CT alone, were 82% and 43%, respectively. CONCLUSIONS: FDG PET and PET-CT are useful in the imaging evaluation of patients with cholangiocarcinoma (except for infiltrating type) for detection of recurrent and metastatic disease and for assessment of treatment response. In particular, the combined structural and metabolic information of PET-CT enhances the diagnostic confidence in lesion characterization.     

F-18 fluorodeoxyglucose positron emission tomography in pulmonary cryptococcoma

Cryptococcosis is not uncommon. Potential interpretation pitfalls should be kept in mind when fluorodeoxyglucose (FDG) positron emission tomography (PET) is used for differentiating pulmonary nodules and for discriminating infection from malignancy, especially in areas where the prevalence of granulomatous infection is high and in immunocompromised patients. In this case, a nodular mass was shown on chest radiography and computed tomographic (CT) scanning. A consolidated infection or a bronchioloalveolar carcinoma was suspected because the CT scan showed air bronchograms within the mass and another perihilar infiltration. The FDG PET scan clearly delineated the lesion and had intermediately high glucose uptake (standard uptake value, 3.8-4.0), which led to the exclusion of the possibility of bronchioloalveolar carcinoma because most of these tumors had normal or mildly increased FDG accumulation. Cryptococcoma was finally diagnosed. Hence, the CT scan and FDG PET played complementary roles in the differential diagnosis of this nodular mass.     

F-18 FDG positron emission tomography and benign fractures

PURPOSE: F-18 2-fluoro-2-deoxy-D-glucose (FDG) positron emission tomography (PET) has been used extensively in the imaging of cancer, including metastatic skeletal disease. Although uptake into benign osseous disease has been reported, there is very limited information regarding uptake into benign fractures. This report provides additional information regarding the appearance of benign fractures on FDG-PET images. MATERIALS AND METHODS: Four case reports of FDG-PET scanning are presented in patients with proved benign fractures. RESULTS: In three of these cases, FDG uptake was noted in fractures when images were obtained 17 days to 8 weeks after injury, with the most avid uptake observed when FDG-PET imaging was performed 17 days after fracture. In the patient in whom imaging was performed 8 weeks after fracture, no uptake of FDG was seen in a benign fracture. CONCLUSIONS: Fractures may accumulate FDG to varying degrees, and false-positive findings may occur when FDG-PET imaging is performed to assess for metastases, although the different pattern of uptake and clinical correlation usually allows accurate differentiation of fracture from skeletal metastases.     

Role of positron emission tomography (PET) and single photon emission tomography (SPECT) in so-called "multiple chemical sensitivity"

Functional imaging with SPECT and PET is increasingly used to prove evidence for the existence of a syndrome "Multiple Chemical Sensitivity" (MCS) and plays a major role in legal trials to justify compensation for the exposure to solvents. This paper critically reviews the literature on the use of SPECT and PET for the determination of MCS. The authors come to the conclusion that the current data are not sufficient to justify the claim of the existence of such a syndrome. The low specificity of the observed PET and especially SPECT-findings makes it very difficult to establish a cause-result relationship and therefore makes the use of these methods in legal trials on this issue doubtful.     

Tc-99m sestamibi/F-18 FDG myocardial SPECT in Takayasu arteritis with coronary artery involvement

Coronary arteries may be involved in some patients with Takayasu arteritis. Evaluation of myocardial involvement due to coronary lesions may provide important information in the clinical management of these patients. We report Tc-99m sestamibi and F-18 FDG myocardial single photon emission computed tomography in 3 cases of such patients.     

18-Fluorodeoxyglucose imaging with positron emission tomography and single photon emission computed tomography: cardiac applications

The assessment of myocardial viability has become an important aspect of the diagnostic and prognostic work-up of patients with ischemic cardiomyopathy. Although revascularization may be considered in patients with extensive viable myocardium, patients with predominantly scar tissue should be treated medically or evaluated for heart transplantation. Among the many viability tests, noninvasive assessment of cardiac glucose use (as a marker of viable tissue) with F18-fluorodeoxyglucose (FDG) is considered the most accurate technique to detect viable myocardium. Cardiac FDG uptake has traditionally been imaged with positron emission tomography (PET). Clinical studies have shown that FDG-PET can accurately identify patients with viable myocardium that are likely to benefit from revascularization procedures, in terms of improvement of left ventricular (LV) function, alleviation of heart failure symptoms, and improvement of long-term prognosis. However, the restricted availability of PET equipment cannot meet the increasing demand for viability studies. As a consequence, much effort has been invested over the past years in the development of 511-keV collimators, enabling FDG imaging with single-photon emission computed tomography (SPECT). Because SPECT cameras are widely available, this approach may allow a more widespread use of FDG for the assessment of myocardial viability. Initial studies have directly compared FDG-SPECT with FDG-PET and consistently reported a good agreement for the assessment of myocardial viability between these 2 techniques. Additional studies have shown that FDG-SPECT can also predict improvement of LV function and heart failure symptoms after revascularization. Finally, recent developments, including coincidence imaging and attenuation correction, may further optimize cardiac FDG imaging (for the assessment of viability) without PET systems.     

F-18 FDG positron emission tomography in primary breast non-Hodgkin's lymphoma

A 50-year-old woman had an irregular, mobile, firm right breast mass that became progressively larger in the past 3 months that measured 18 x 15 cm at the time of examination. She had no nipple discharge or skin changes. A 2-[18F]-fluoro-2-deoxy-D-glucose positron emission tomography (FDG PET) showed a ring-shaped breast uptake consisting of high peripheral glycolytic activity and a cold center most likely representing necrosis or hemorrhage despite the absence of a history of trauma, surgical intervention, chemotherapy, or radiation to the breast. Whole-body images did not show any evidence of lymph node involvement or distant metastases. These results were confirmed by computed tomography of the chest, abdomen, and pelvis. Cytologic examination of a fine-needle aspiration of the breast mass showed diffuse large B-cell, intermediate grade, non-Hodgkin's lymphoma. Although it occurs infrequently, primary breast lymphoma should be considered in patients with a breast mass that shows a ring-shaped FDG uptake. A PET scan, in contrast to other imagining techniques, offers the advantage of screening the entire body, excluding the presence of metastases, and confirming the primary origin of the breast lymphoma.     

Unusual extracardiac findings detected on myocardial perfusion single photon emission computed tomography studies with Tc-99m sestamibi

The authors describe the incidence and various uptake patterns of Tc-99m sestamibi (MIBI) in the extracardiac area due to unusual causes on myocardial perfusion single photon emission computed tomography (SPECT) studies. Seven patients are presented in whom incidental extracardiac findings were observed during the interpretation of the raw data besides the routine evaluation of myocardial reconstructed SPECT slices. These 7 patients were detected out of 582 consecutive patients (1.2%) who had myocardial perfusion SPECT with Tc-99m MIBI. The findings on the raw data led to additional reconstruction of thoracic SPECT images and eventually detailed examination of the extracardiac area. Two of the patients underwent surgery because of incidental extracardiac findings (thymoma and multinodular goiter) on cardiac scintigraphy. Other causes of increased extracardiac activity were the intestine protruded through the left hemithorax, uptake in the pulmonary arterial wall, and pulmonary interstitial fibrosis due to sarcoidosis. The reasons for decreased Tc-99m MIBI accumulation in the extracardiac area in the 2 other patients were significantly dilated pulmonary arteries and hydatic cyst, which were not defined before to our knowledge. Familiarity with the normal biodistribution and variable uptake patterns in the raw images becomes necessary during the interpretation of myocardial SPECT in order not to miss very unusual incidental extracardiac uptake or information that could lead to alteration in patient management. Potential underlying mechanisms of extracardiac Tc-99m MIBI accumulation are discussed, and the literature about noncardiac Tc-99m MIBI findings detected on myocardial perfusion SPECT studies was reviewed.     

F-18 FDG positron emission tomography findings in primary pancreatic lymphoma

The usefulness of F-18 2'-deoxy-2-fluoro-D-glucose (FDG) positron emission tomography (PET) has been well established for lymphoma staging. Although involvement of the pancreas occurs in more than one third of patients with non-Hodgkin lymphoma, primary lymphoma of the pancreas accounts for less than 1% of extranodal non-Hodgkin lymphomas. Because patients with primary pancreatic lymphoma require a different therapeutic approach and have a better prognosis than those with pancreatic adenocarcinoma, the accurate diagnosis is important. However, conventional imaging modalities cannot differentiate between adenocarcinoma and other less common neoplasms such as lymphoma. We report a 67-year-old man who had a primary pancreatic lymphoma in which FDG PET imaging revealed round, intense FDG uptake in the center of the midabdomen.     

The usefulness of F-18 fluorodeoxyglucose positron emission tomography/computed tomography in patients with Langerhans cell histiocytosis

Objective

Langerhans cell histiocytosis (LCH) has a wide spectrum of clinical manifestations, ranging from spontaneous resolution to rapid progression or death, with the risk of permanent consequences. F-18 FDG PET/CT has been used for assessment of LCH patients. However, its clinical implication has not been well elucidated, mainly due to very low incidence of LCH. The aim of this study was to evaluate the clinical usefulness of F-18 FDG PET/CT in LCH patients.

Methods

A database of 12 patients (mean age 17.8?±?17.9?years; 7 children, 5 adults) who were diagnosed histopathologically as LCH was retrospectively reviewed. Two patients underwent F-18 FDG PET/CT before and after therapy, 6 patients underwent only before therapy and 4 patients underwent only after therapy.

Results

Nine (75.0?%) and 3 patients (25.0?%) had single-system (single site and multiple sites) and multisystem involvements, respectively. Pretreatment SUV_max of patients with multisystem or multiple site involvement of a single-system was significantly higher than that of patients with single site involvement of a single-system (3.29?±?2.52 vs. 1.63?±?0.52, p?=?0.025). One patient showed multisystem risk organs (lung and bone marrow) involvement. In 2 patients, F-18 FDG PET/CT detected additional active LCH lesions not identified on conventional imaging modalities. In follow-up F-18 FDG PET/CT scans, complete resolution was identified in 2 patients and reactivation in another 2 patients.

Conclusions

Results of this study suggest that F-18 FDG PET/CT is useful for identification of active lesions, stratification of disease stages, monitoring of therapeutic response, and detection of reactivation in LCH patients.