Applications of PET in lung cancer

An estimated 180,000 new cases of lung cancer will be diagnosed in the United States this year, and lung cancer accounts for approximately 25% of all cancer deaths. The overall 5-year survival rate is 14%, and this has not changed over the past several decades. Lung cancer diagnosis and treatment is a major health problem globally. Most lung cancers are detected initially on chest radiographs, but many benign lesions have radiologic characteristics similar to malignant lesions. Thus, additional studies are required for further evaluation. Computed tomography (CT) is most frequently used to provide additional anatomic and morphologic information about the lesion, but it is limited in distinguishing benign from malignant abnormalities in the lung, pleura, and mediastinum. Because of the indeterminate results from anatomic imaging, biopsy procedures including thoracoscopy and thoracotomy may be used even through one-half of the lesions removed are benign and do not need to be removed. FDG-PET imaging provides physiologic and metabolic information that characterizes lesions that are indeterminate by CT and that accurately stages the distribution of lung cancer. Exploiting the fundamental biochemical differences between cancer and normal tissues, FDG imaging takes advantage of the increased accumulation of FDG in transformed cells. FDG-PET is very sensitive (approximately 95%) for the detection of cancer in patients who have indeterminate lesions on CT. The specificity (approximately 85%) of PET imaging is slightly less than the sensitivity because some inflammatory processes such as active granulomatous infections accumulate FDG avidly. The high-negative predictive value of PET suggests that lesions considered negative on the study are benign, biopsy is not needed, and radiographic follow-up is recommended. Several studies have documented the increased accuracy of PET compared with CT in the evaluation of the hilar and mediastinal lymph node status in patients with lung cancer. If the mediastinum is normal on PET imaging and there is no other evidence of metastatic disease, the patient has a thoracotomy. If the mediastinum is abnormal on PET imaging, mediastinoscopy is performed with the PET images providing the lymph node stations to target. Whole-body PET studies detect metastatic disease that is unsuspected by conventional imaging and demonstrate some of the anatomic abnormalities detected by CT to be benign lesions. Management changes have been reported to occur in up to 41% of patients based on the results of the whole-body studies.     

Dynamic positron emission tomography with F-18 fluorodeoxyglucose imaging in differentiation of benign from malignant lung/mediastinal lesions

PURPOSE: This study was done to evaluate the diagnostic utility of dynamic positron emission tomography (PET) with F-18 fluorodeoxyglucose (FDG) imaging in patients with suspected malignant pulmonary lesions. We wanted to test the hypothesis that the rate of FDG uptake (FDG influx constant values) would differentiate malignant from benign lung or mediastinal lesions. MATERIALS AND METHODS: We performed segmental dynamic PET imaging studies following administration of FDG in 19 patients with indeterminate pulmonary lesions based on chest radiograph and/or CT scans. Patlak analysis was done to compute Ki (FDG influx constant) values and compared with FDG standardized uptake values (SUVs) and histology. RESULTS: FDG Ki values (mean+/-SD) were significantly greater (p < 0.01) in all 12 malignant lesions (0.029+/-0.02) as compared with 7 benign lesions (0.0024+/-0.0011) with good correlation to the SUV values. Distinct time activity curve patterns were identified in malignant and benign lesions with continued uptake in malignant lesions. CONCLUSION: Dynamic PET-FDG imaging accurately differentiates malignant from benign pulmonary lesions. In certain cases with equivocal findings on visual analysis and SUV values, dynamic imaging may be further helpful in differentiating benign and malignant lesions.     

Comparison of fluorine-18 fluorodeoxyglucose positron emission tomography and technetium-99m methoxyisobutylisonitrile scintimammography in the detection of breast tumours

The aim of this study was to compare, in breast cancer patients, the diagnostic accuracy of positron emission tomography (PET) using fluorine-18 fluorodeoxyglucose (FDG) and scintimammography (SMM) using technetium-99m methoxyisobutylisonitrile (MIBI). A total of 20 patients (40 breasts with 22 lesions) were evaluated serially with MIBI and, on the following day, with FDG. For SMM, planar and single-photon emission tomography imaging in the prone position was performed starting at 10 min following the injection of MIBI (740 MBq). For PET, scans were acquired 45-60 min after the injection of FDG (370 MBq) and attentuation correction was performed following transmission scans. Results from SMM and PET were subsequently compared with the histopathology results. True-positive results were obtained in 12/13 primary breast cancers (mean diameter=29 mm, range 8-53 mm) with both FDG and MIBI. False-negative results were obtained in two local recurrences (diameter <9 mm) with both FDG and MIBI. In benign disease, FDG and MIBI did not localize three fibrocystic lesions, two fibroadenomas and one inflammatory lesion (true-negative), but both localized one fibroadenoma (false-positive). Collectively, the results demonstrate a sensitivity of 92%, and a specificity of 86%, for primary breast cancer regardless of whether FDG or MIBI was used. In contrast to MIBI scintigraphy, FDG PET scored the axillae correctly as either positive (metastatic disease) or negative (no axillary disease) in all 12 patients. The tumour/non-tumour ratio for MIBI was 1.97 (range 1.43-3.1). The mean standard uptake value (SUV) for FDG uptake was 2.57 (range 0.3-6.2). The diagnostic accuracy of SMM was equivalent to that of FDG PET for the detection of primary breast cancer. For the detection of in situ lymph node metastases of the axilla, FDG seems to be more sensitive than 99mTc-MIBI.     

False-positive 2-[F-18]-fluoro-2-deoxy-D-glucose positron emission tomography studies for evaluation of focal pulmonary abnormalities

Positron emission tomography (PET) with 2-[F-18]-fluoro-2-deoxy-D-glucose (FDG) can demonstrate the glucose metabolism characteristics of a lesion, which may be helpful in differentiating between benign and malignant focal pulmonary lesions. Malignant cells demonstrate higher glucose metabolic activity than benign lesions. However, some inflammatory processes also show significant FDG uptake. We present two cases where high FDG uptake was found in inflammatory lesions in the lungs. The first case was that of a 38-year-old woman with chronic cough for more than 20 years. FDG PET revealed a hypermetabolic lesion with a lesion-to-background ratio of 8.0 at the posterior aspect of the right middle lung. She underwent thoracotomy and tumor resection, and was diagnosed with cryptococcosis. The second case was that of a 72-year-old woman who had pulmonary tuberculosis previously with cavitation in the left lower lobe. She suffered from fever, chills and severe hemoptysis for several days before this admission. FDG PET revealed a hypermetabolic ring at the periphery of the cavity. The lesion-to-background ratio was 7.8. Echo-guided biopsy showed no evidence of malignancy. She was treated with antibiotics and the symptoms subsided gradually. Lung abscess complicating a pre-existing cavity was diagnosed. These two cases substantiate that positive FDG PET results should be interpreted with caution in differentiating benign from malignant pulmonary abnormalities, especially in regions with a high prevalence of granulomatous lesions.     

Metabolic imaging of malignant pleural mesothelioma with fluorodeoxyglucose positron emission tomography

BACKGROUND: The diagnosis of malignant mesothelioma is a challenging medical problem. CT often cannot differentiate between benign diffuse pleural thickening and malignant mesothelioma, while thoracentesis and CT-guided biopsies are insensitive. We have assessed the value of positron emission tomography (PET) with 2-fluoro-2-deoxy-D-glucose (FDG) in the evaluation of malignant mesothelioma. METHODS: Twenty-eight consecutive patients referred for the evaluation of suspected malignant mesothelioma were evaluated by FDG-PET imaging. Measured attenuation correction was performed in 26 of 28 cases for quantitation with the standardized uptake value (SUV) method. The results of PET imaging were compared with those of video-assisted thoracoscopy or surgical biopsies. RESULTS: Surgical biopsy specimens confirmed the presence of malignant disease in 24 patients and demonstrated benign processes in the remaining four. The uptake of FDG was significantly higher in malignant than in benign lesions (SUV=4.9+/-2.9 and SUV=1.4+/-0.6, respectively; p<0.0001). With a SUV cutoff of 2.0 to differentiate between malignant and benign disease, a sensitivity of 91% and a specificity of 100% could be achieved, although the activity in some epithelial mesotheliomas tended to be close to this threshold. FDG-PET images provided excellent delineation of the active tumor sites. Hypermetabolic lymph node involvement was noted on FDG-PET images in 12 patients, 9 of which appeared normal on CT scans. Histologic examination in six patients confirmed malignant nodal disease in five cases and indicated granulomatous lymphadenitis in one. CONCLUSION: In this highly selected population, FDG-PET imaging was a sensitive method to identify malignant mesothelioma and determine the extent of the disease process.     

Evaluation of benign vs malignant hepatic lesions with positron emission tomography

BACKGROUND: In most malignant cells, the relatively low level of glucose-6-phosphatase leads to accumulation and trapping of [18F]fluorodeoxyglucose (FDG) intracellularly, allowing the visualization of increased uptake compared with normal cells. OBJECTIVES: To assess the value of FDG positron emission tomography (PET) to differentiate benign from malignant hepatic lesions and to determine in which types of hepatic tumors PET can help evaluate stage, monitor response to therapy, and detect recurrence. DESIGN: Prospective blinded-comparison clinical cohort study. SETTING: Tertiary care university hospital and clinic. PATIENTS: One hundred ten consecutive referred patients with hepatic lesions 1 cm or larger on screening computed tomographic (CT) images who were seen for evaluation and potential resection underwent PET imaging. There were 60 men and 50 women with a mean (+/-SD) age of 59 +/- 14 years. Follow-up was 100%. INTERVENTIONS: A PET scan using static imaging was performed on all patients. The PET scan imaging and biopsy, surgery, or both were performed, providing pathological samples within 2 months of PET imaging. All PET images were correlated with CT scan to localize the lesion. However, PET investigators were unaware of any previous interpretation of the CT scan. MAIN OUTCOME MEASURES: Visual interpretation, lesion-to-normal liver background (L/B) ratio of radioactivity, and standard uptake value (SUV) were correlated with pathological diagnosis. RESULTS: All (100%) liver metastases from adenocarcinoma and sarcoma primaries in 66 patients and all cholangiocarcinomas in 8 patients had increased uptake values, L/B ratios greater than 2, and an SUV greater than 3.5. Hepatocellular carcinoma had increased FDG uptake in 16 of 23 patients and poor uptake in 7 patients. All benign hepatic lesions (n = 23), including adenoma and fibronodular hyperplasia, had poor uptake, an L/B ratio of less than 2, and an SUV less than 3.5, except for 1 of 3 abscesses that had definite uptake. CONCLUSIONS: The PET technique using FDG static imaging was useful to differentiate malignant from benign lesions in the liver. Limitations include false-positive results in a minority of abscesses and false-negative results in a minority of hepatocellular carcinoma. The PET technique was useful in tumor staging and detection of recurrence, as well as monitoring response to therapy for all adenocarcinomas and sarcomas and most hepatocellular carcinomas. Therefore, pretherapy PET imaging is recommended to help assess new hepatic lesions.     

Detection of recurrent or persistent nasopharyngeal carcinomas after radiotherapy with 18-fluoro-2-deoxyglucose positron emission tomography and comparison with computed tomography

PURPOSE: The effectiveness of positron emission tomography (PET) with 1 8-fluoro-2-deoxyglucose (FDG) for detecting suspected recurrence of nasopharyngeal carcinomas (NPC) was evaluated and compared with computed tomography (CT). PATIENTS AND METHODS: FDG-PET studies were performed on 36 NPC patients 4 months after radiotherapy. The images were interpreted visually and quantitatively by calculating standardized uptake values (SUVs). RESULTS: The sensitivity, specificity, and accuracy of visually interpreted FDG-PET images, for differentiation of recurrent or persistent NPC from benign lesions, were 100%, 96%, and 97%, respectively. Cases with recurrent or persistent NPC (1.6 to 5.8) had significantly higher SUVs than cases with benign lesions (0.8 to 1.5). The sensitivity, specificity, and accuracy of CT for detecting recurrent or persistent NPC were 72%, 88%, and 83%, respectively. CONCLUSION: FDG-PET is a better tool than CT for the detection of recurrent or persistent NPC. Either visual interpretation or SUV can be used to differentiate benign lesions from recurrent or persistent NPC.     

Effect of ovariohysterectomy in bitches with mammary neoplasms

Ninety bitches with mammary tumours were studied for two years after the surgical removal of the primary tumour(s). Twenty-nine of the bitches had been spayed before the development of the mammary tumour, 22 were spayed when the tumours were removed and 39 were left entire. Fifty-eight of the bitches (64 per cent) had benign tumours and, of these, 15 (26 per cent) developed a new mammary tumour within two years, irrespective of whether the bitch was spayed. The other 32 bitches had malignant tumours which were grouped into 'invasive' and 'well defined' carcinomas. Sixty-three per cent of the spayed bitches and 57 per cent of the entire bitches, with invasive carcinoma were dead within two years of surgery as a result of their mammary tumours. For those with well defined carcinomas the tumour-related death rates were 18 per cent and 33 per cent respectively for the spayed and entire bitches. These findings suggest that ovariohysterectomy when mammary tumours are removed does not have a significant effect on the progression of malignant disease, and that about one in four bitches with a benign mammary tumour is likely to develop a further tumour in another gland.     

Detection of response to chemotherapy using positron emission tomography in patients with oesophageal and gastric cancer

BACKGROUND: The aim of the study was to determine whether 2-[18F]-fluoro-2-deoxy-D-glucose (FDG)-positron emission tomography (PET) could detect response to chemotherapy in patients with oesophageal and gastric cancer. METHODS: Fourteen patients underwent imaging before and after chemotherapy using FDG-PET. Computed tomography (CT), dysphagia scores and weight changes were used for comparison of evidence of response. Tumour to liver ratios (TLRs) and influx constants for FDG (K) were used for quantification purposes. RESULTS: Thirteen of 14 lesions were successfully imaged before therapy. Changes were seen in all follow-up scans, ranging from a complete response to a 15 per cent increase in tumour FDG uptake. Response was demonstrated by CT in four patients; all four had large reductions in FDG uptake after chemotherapy. Two patients with an increase in FDG uptake reported no improvement in dysphagia and continued to lose weight during therapy. CONCLUSION: Changes in tumour FDG uptake were seen in all tumours after chemotherapy. FDG-PET may have a role to play in the assessment of patients with upper gastrointestinal malignancy receiving chemotherapy.     

Metabolic characterization of breast tumors with positron emission tomography using F-18 fluorodeoxyglucose

PURPOSE: To evaluate the diagnostic value of position emission tomographic (PET) imaging with F-18 fluorodeoxyglucose (FDG) in differentiating between benign and malignant breast tumors. PATIENTS AND METHODS: Fifty-one patients, with suspicious breast lesions newly discovered either by physical examination or by mammography, underwent PET imaging before exploratory surgery. FDG-PET images of the breast were analyzed visually and quantitatively for objective assessment of regional tracer uptake. RESULTS: Primary breast cancer was identified visually with a sensitivity of 68% to 94% and a specificity of 84% to 97% depending on criteria used for image interpretation. Quantitative analysis of FDG uptake in tumors using standardized uptake values (SUV) showed a significant difference between benign (1.4 +/- 0.5) and malignant (3.3 +/- 1.8) breast tumors (P < .01). Receiver operating characteristic (ROC) curve analysis exhibited a sensitivity of 75% and a specificity of 100% at a threshold SUV value of 2.5. Sensitivity increased to 92% with a corresponding specificity of 97% when partial volume correction of FDG uptake was performed based on independent anatomic information. CONCLUSION: PET imaging allowed accurate differentiation between benign and malignant breast tumors providing a high specificity. Sensitivity for detection of small breast cancer ( < 1 cm) was limited due to partial volume effects. Quantitative image analysis combined with partial volume correction may be necessary to exploit fully the diagnostic accuracy. PET imaging may be helpful as a complimentary method in a subgroup of patients with indeterminate results of conventional breast imaging.     

PET imaging of lung tumours and mediastinal lymphoma

Positron emission tomography (PET) of the lung is evaluated regarding its clinical practicability for staging of bronchogenic carcinomas and lymphomas. Stringent quality control, optimized acquisition and reconstruction techniques are of crucial importance. An analysis of 50 PET studies for tumour (T) and lymphnode (N) staging in comparison to CT shows that PET has the highest diagnostic accuracy to classify lesions and is the most promising technique for non-invasive staging. PET cannot be the first imaging modality, but if unnecessary or invasive procedures can be avoided, the additional expense of a PET study seems justified.     

Whole-body [18F]FDG PET in the management of metastatic brain tumours

BACKGROUND: To determine its roles in the diagnosis and the systemic evaluation of metastatic brain tumours, whole-body positron emission tomography (PET) using [18F]FDG was performed in 20 consecutive patients. METHODS: All patients were thought to be suffering or needing to be differentiated from metastatic brain tumours. Nine patients had multiple brain lesions; six were older and showed a rim-enhancing lesion with surrounding oedema; seven had homogeneously enhancing periventricular lesion(s) on computed tomography (CT) and/or magnetic resonance (MR) imaging, thought to be central nervous system lymphomas. Two patients had skull mass(es) and two patients had a solid mass suspected to be, respectively, a haemorrhagic metastasis and a metastatic malignant melanoma. All of them received whole-body [18F]FDG PET and conventional systemic work-up for metastasis in order to compare the results of the two methods. RESULTS: Metastatic brain tumours were diagnosed on whole-body [18F]FDG PET in eleven patients who had extracranial and intracranial hypermetabolic lesions. In nine of these, a conventional work-up also detected primary lesions which on whole-body [18F]FDG PET were seen to be hypermetabolic foci. Systemic lymph node metastases were detected by whole-body [18F]FDG PET only in two patients and histological diagnosis was possible by biopsy of lymph nodes rather than of brain lesions. In the remaining nine patients who had only intracranial hypermetabolic foci, histological diagnosis was made by craniotomy or stereotactic biopsy. It was confirmed that seven of nine patients were suffering from a primary brain tumour and two from metastatic carcinoma. None of the nine showed evidence of systemic cancer on conventional work-up. Histological diagnoses of the primary brain tumours were four cases of primary central nervous system lymphoma and one each of multifocal glioblastoma, Ewing's sarcoma, and cavernous angioma. Patients felt no discomfort during the whole-body [18F]FDG PET procedure and there were no complications. The false negative rate in [18F]FDG PET and in conventional work-up was 15.4% and 30.7% respectively. There were no false positives on either [18F]FDG PET or conventional work-up. CONCLUSION: It is suggested that whole-body [18F]FDG PET is a safe, reliable, and convenient method for the diagnosis and systemic evaluation of patients thought to be suffering or needing to be differentiated from a metastatic brain tumour.     

Evaluation of pancreatic tumors with positron emission tomography and F-18 fluorodeoxyglucose: comparison with CT and US

PURPOSE: To assess the clinical value of positron emission tomography (PET) with fluorine-18-labeled fluorodeoxyglucose (FDG) for identification of pancreatic carcinoma. MATERIALS AND METHODS: Forty-six patients suspected of having a pancreatic neoplasm and who were to undergo surgery prospectively underwent FDG PET, computed tomography (CT), and transabdominal ultrasound (US). Endoscopic US was performed in 40 patients. Images were independently interpreted and compared with the histopathologic findings at surgery (41 patients) or with clinical follow-up findings (five patients). RESULTS: In 33 of 35 patients, foci of pancreatic carcinomas (10-100 mm in diameter) were identified as an increase in FDG uptake, whereas CT, transabdominal US, and endoscopic US depicted the foci in 31, 31, and 28, cases, respectively. Among 11 benign lesions, nine showed no increased FDG uptake (specificity = 82%). Specificities of the other modalities were lower. False-positive findings were obtained in a case of chronic active pancreatitis and in a serous cystadenoma. CONCLUSION: FDG PET, which provides "biochemical" information, is accurate in identifying pancreatic carcinoma and may be a method of choice when imaging equivocal masses detected with other "anatomic" imaging studies.     

FDG PET in head and neck cancer

In our extensive experience with FDG PET imaging in head and neck cancer, we have found the technique to be of high accuracy but of limited usefulness. This seeming paradox arises from several causes. Competing techniques such as CT, MR imaging, and even clinical examination already have good accuracy. In addition, high-resolution studies such as CT and MR imaging provide information required for treatment planning that is unavailable from FDG PET images. The high cost of FDG PET militates against its use in this setting, in which only a small marginal gain can be expected. In the special problem areas in which FDG PET might be expected to offer unique advantages, such as screening for second primary lesions, searching for unknown primary lesions, or differentiating benign salivary rumors from malignant lesions, the results of FDG PET have been disappointedly poor. Of these special problem areas, only the question of accuracy in finding occult primary lesions appears unresolved and in need of further study. The single application in which FDG PET appears to be advantageous is the posttherapy setting. In this setting, the technique is definitely superior to alternative methods of determining tumor recurrence and differentiating posttherapy sequelae such as radiation necrosis from tumor recurrence. We believe that considerable opportunity remains for further research on the use of FDG PET in head and neck cancer. Other agents such as 11C-methionine for example, might improve the diagnostic accuracy of FDG PET in some of the problem areas that we have identified, such as the early postirradiation period. We currently have such a study under way. Also, because FDG PET offers a unique way to measure tumor metabolism, further investigation of the use of FDG PET tracers to evaluate various biologic parameters such as proliferation rates or tumor hypoxia are needed. Such studies could provide a noninvasive technique to identify which fractionation schemes or combinations of therapy might be useful for individual patients. A final caveat is in order. Although our findings of the usefulness (and lack thereof) of FDG PET in head and neck cancer may be disappointing to many, these results should not be generalized to other applications of FDG PET in oncology. Each tumor type and setting presents its own specific problems, and in some instances FDG PET offers unique advantages over other imaging techniques. A good example is the setting of primary lung cancer, in which FDG PET appears clearly superior to all other methods of pretherapy screening [19-20].     

Detection of paraneoplastic anti-neuronal autoantibodies on paraffin-embedded tissues

Although the detection of pancreatic carcinoma has been considerably improved by recently developed imaging procedures, differential diagnosis between cancer and benign tumor masses, as well as lymph node staging, is still difficult. In vivo evaluation of regional glucose metabolism by means of positron emission tomography (PET) and fluorine-18-labelled fluorode-oxyglucose (FDG) is a new approach utilizing metabolic instead of morphological tumor properties for diagnosis. PATIENTS AND METHODS. A total of 85 patients with suspected pancreatic carcinoma were investigated by FDG-PET prior to surgery. Static PET scans were evaluated visually as well as quantitatively, taking increased FDG uptake as a sign of malignancy. PET results were correlated with intraoperative findings and histopathology of surgical specimens. RESULTS. Forty-seven out of 55 (85%) malignant tumors and 23 out of 30 (77%) benign lesions were correctly classified by PET. Lymph node metastases were present in 31 patients, 19 of them (61%) positive in PET. In 7 our of 13 (54%) patients with liver metastases, PET detected hypermetabolic lesions. False-negative findings were mainly due to disturbance of glucose metabolism in diabetic patients, while most false-positive results could be attributed to acute inflammatory lesions in chronic pancreatitis. CONCLUSIONS. Our results indicate that classification of pancreatic masses can be improved by use of FDG-PET, which might lead to a reduction of unnecessary laparotomies in patients with benign or incurable disease.     

Identification of a novel antigenic structure of the human receptor for interleukin-6 involved in the interaction with the glycoprotein 130 chain

PURPOSE: To evaluate the diagnostic accuracy of positron emission tomography (PET) with administration of 2-deoxy-2-[fluorine-18]fluoro-D-glucose (FDG) relative to that of magnetic resonance (MR) imaging and/or computed tomography (CT) in recurrent head and neck cancers. MATERIALS AND METHODS: Twelve adult patients (mean age, 63 years) with previously treated head and neck cancers and clinical suspicion of recurrence underwent FDG PET and MR imaging and/or CT. All images were blindly and independently interpreted without histopathologic findings (obtained within 1 week of imaging). The level of confidence in image interpretation was graded by using a five-point rating system (0 = definitely no recurrence to 4 = definite recurrence). RESULTS: Recurrence was confirmed in eight patients. With a rating of 4 as a positive finding, FDG PET yielded a sensitivity and specificity of 88% (seven of eight) and 100% (four of four), respectively; MR imaging and/or CT, 25% (two of eight) and 75% (three of four), respectively. Receiver-operating characteristic analysis showed significantly better diagnostic accuracy with FDG PET than with MR imaging and/or CT (area under curve = 0.96 vs 0.55, P < .03). CONCLUSION: These data indicate that PET metabolic imaging, as compared with anatomic methods, has improved diagnostic accuracy for recurrent head and neck cancer.     

Diagnosis of pancreatic carcinoma: role of FDG PET

OBJECTIVE: The purpose of this study was to investigate the role of positron emission tomography (PET) with 18F-fluorodeoxyglucose (FDG) in differentiating benign from malignant disease in patients with possible pancreatic malignancy. SUBJECTS AND METHODS: All patients with a possible diagnosis of pancreatic carcinoma based on CT or ERCP findings were eligible for inclusion in this prospective study. PET imaging of the abdomen was performed in 37 patients and was interpreted as positive if FDG activity in the pancreas exceeded background activity and as negative if activity was less than or equal to background activity. Semiquantitative analysis was performed by calculating a standardized uptake ratio. Studies were reviewed independently by two radiologists, and results were correlated with biopsy results and with CT and ERCP findings. Sensitivity and specificity of FDG PET for revealing pancreatic malignancy was determined. RESULTS: FDG activity in the pancreas was increased in 24 patients, and adenocarcinoma was diagnosed in 22 of these patients (92%). Two patients (8%) with increased activity had benign disease, including one patient with chronic pancreatitis who showed no evidence of tumor at laparotomy and one patient with a mucinous cystic tumor who showed no malignant features at laparotomy. FDG uptake was low or normal in 13 patients, 10 of whom (77%) had benign disease. FDG uptake was also low in three patients with adenocarcinoma, whose tumor size ranged from 2 to 4 cm in diameter. The mean standardized uptake ratio value for malignant disease was 5.1 (range, 1.0-10.1) and for benign disease was 1.9 (range, 0.0-5.8) (p < .001). The sensitivity of FDG PET for revealing malignant disease in the pancreas was 88% and the specificity was 83%. CONCLUSION: FDG PET is a sensitive and specific noninvasive technique for the diagnosis of pancreatic malignancy.     

Fluorine-18-fluorodeoxyglucose assessment of glucose metabolism in bone tumors

In our study, we investigate the glucose metabolism of various types of bone lesions with 18F-fluorodeoxyglucose (FDG) PET. METHODS: Twenty-six patients showing clinical and radiographic symptoms of a malignant bone tumor were included. Histological examination after the PET study revealed 19 malignant and 7 benign tumors. PET images were corrected for attenuation. Arterial blood samples were taken to establish the input function. The metabolic rate of glucose consumption (MRglc) was calculated for the whole tumor, for the 10 pixels with maximum activity and for contralateral normal muscle tissue. RESULTS: All lesions were clearly visualized with 18F-FDG PET except for a small infarction of the humerus. All the other lesions had increased glucose metabolism compared to surrounding and contralateral muscle tissue. Both maximum and average MRglc for benign, as well as malignant, lesions were significantly higher than for contralateral normal tissue. The maximum and average MRglc were not higher for malignant as opposed to benign lesions. There was a large overlap between the MRglc of benign and malignant lesions. CONCLUSION: Fluorine-18-FDG PET appears suitable to visualize bone tumors. With the quantification of glucose metabolism, it is not possible to differentiate between benign and malignant bone tumors. There does not seem to be a clear correlation between the MRglc and the biologic aggressiveness of the neoplasms.     

Improved retroperitoneal and gastrointestinal sonography using oral contrast agents in a porcine model

PURPOSE: To evaluate use of functional imaging with positron emission tomography (PET) versus computed tomography (CT) for detection of extranodal lymphoma spread. MATERIALS AND METHODS: Eighty-one consecutive and previously untreated patients with malignant non-Hodgkin lymphoma (n = 43) or Hodgkin disease (n = 38) were examined with 2-[fluorine-18]fluoro-2-deoxy-D-glucose (FDG) PET and contrast material-enhanced CT. Concordant findings at both CT and FDG PET were regarded as actual locations of disease; discordant results were resolved on the basis of biopsy or follow-up results when possible. RESULTS: Forty-two lesions were identified at both PET and CT, and 19 were verified with biopsy results. PET demonstrated a further 24 lesions. Verification was possible in 15 of these lesions with biopsy (n = 10), magnetic resonance imaging (n = 1), scintigraphic (n = 1), or follow-up (n = 3) results. In 14 of these 15 lesions, PET findings were confirmed (bone marrow, nine; spleen, three; other, two). Seven lesions not visualized at FDG PET were identified at CT, six of which were verified with biopsy (n = 2) or follow-up (n = 4) results. Five of these six CT findings were found to be erroneous. In 13 patients, PET findings led to changes in tumor staging. CONCLUSION: PET may provide more information about extranodal lymphoma than does incremental CT.     

Mediastinal cyst involving the oesophagus: diagnosis and results of surgical treatment

OBJECTIVE: To describe our experience with mediastinal cysts involving the oesophagus. DESIGN: Retrospective study. SETTING: University hospital, Italy. SUBJECTS: 11 patients who presented to our department with a mediastinal cyst from 1976-1994. INTERVENTIONS: Excision of the mass through a posterolateral thoracotomy (n = 10) or by video-assisted thoracoscopy. MAIN OUTCOME MEASURES: Morbidity and mortality. RESULTS: 8 patients presented with retrosternal or epigastric pain, three of whom had mild dysphagia. In the remaining 3 the tumour was asymptomatic and an incidental finding on a chest radiograph. Endoscopic ultrasonography and computed tomography (CT) allowed preoperative diagnosis of an extramucosal cyst in 5 of the 7 patients investigated by both tests. Masses were excised through a formal thoracotomy (n = 10) or by video-assisted thoracoscopy. Histological examination confirmed a benign cyst in all cases. There was no operative morbidity and nine patients are free of symptoms after a median follow-up of 2.3 years. CONCLUSION: Excision, preferably by thoracoscopy, is the treatment of choice for mediastinal cysts that involve the oesophagus. Special attention should be paid to the vagal nerves, and as many as possible of the muscular layers of the oesophagus should be preserved.