Clinical positron imaging : official journal of the Institute for Clinical P.E.T最新文献

Purpose: A rising CEA level after the resection of colorectal cancer is an early indicator of tumour recurrence. However, conventional imaging techniques have limited sensitivity for detecting recurrent disease in such patients. Our group has evaluated the role of Positron Emission Tomography with ¹⁸F-Fluorodeoxiglucose (FDG-PET) in this clinical situation.

Material and Methods: Seventy-two patients with abnormal CEA levels and normal results of conventional methods of tumour detection were studied with FDG-PET. The PET results were compared with pathologic findings (n = 25) long-term radiological (n = 9) and clinical follow-up (n = 38). Influence of PET findings in therapeutic management was also considered in this study.

Results: PET detected lesions in 63/72 patients (87.1%). Metabolic imaging showed metastases in the liver (44.1%), ganglionar nodes (27.5%), local recurrence (20.4%) and lung metastases (8%). Overall, the sensitivity of PET was 94.4%, specificity was 83.3%, the positive-predictive value was 97.1%, the negative-predictive value was 71.4% and the diagnostic accuracy was 92.8%. FDG-PET findings change therapeutic decision in 68/72 patients (94.1%)

Conclusion: When conventional examinations are normal, FDG-PET is a valuable imaging tool in patients who have rising CEA level after colorectal surgery. Metabolic imaging represents a very cost-effectiveness diagnostic procedure in this clinical situation, avoiding unnecessary invasive techniques.

Purpose: To analyze the efficacy and impact on management of PET-FDG in patients with metastases from unknown primary tumor.

Procedures: Retrospective analysis of 24 patients referred to the PET center for metastasis of unknown primary after a negative imaging workup. PET results were validated by means of oriented imaging, follow-up or biopsy when ethically justified.

Results: PET identified the primary tumor in 13/24 (54%) of patients: breast (n = 1), lung (n = 9), colon (n = 1), stomach (n = 1) and mouth (n = 1). The false positive rate of PET was 21% (5/24). PET was shown to affect the management of 10/24 patients (42%).

Conclusion: Whole body PET-FDG was more effective than conventional imaging methods in detecting unknown primary tumors. PET altered patient management in 42% of cases. PET should be performed prior to other investigations in such patients and could avoid unnecessary and often unfruitful diagnostic procedures.

Purpose: Positron Emission Tomography with ¹⁸F-Fluorodeoxyglucose (¹⁸FDG-PET) is becoming the noninvasive test of choice to evaluate patients with single pulmonary nodules (SPN). While positive scans yield a high sensitivity for malignancy, the significance of negative scans remains unclear. The purpose of this study was to evaluate the prognostic value of negative ¹⁸FDG-PET in patients with SPN.

Methods: From January 1998 to January 2000, 59 patients with non-calcified parenchymal SPN underwent ¹⁸FDG-PET evaluations. From a total of 14 pathologically proven tumors 12 patients had positive ¹⁸FDG-PET scans (sensitivity 86%, PPV 100%) with a mean SUV of 5.6. A total of 24 patients (41%) with negative ¹⁸FDG-PET scans were followed up with serial chest x-ray (CXR) and/or Computed tomography (CT) for a period of 6 to 24 months (mean 10.4 months). Histology specimens were available in 5 patients. Two patients had a second PET scan.

Results: Nineteen of the 24 negative ¹⁸FDG-PET patients (79.2%) had no evidence of intrathoracic neoplasia at subsequent follow up by CT and/or CXR, for an overall NPV of 86.3%. Two patients (8.3%) had transthoracic needle biopsies that were positive for malignancy after the PET scan. The remaining 3 patients developed intrathoracic malignancies during the follow up period (6, 6, and 9 months respectively) by CT and/or CXR. Repeat ¹⁸FDG-PET scans were positive in 2 patients.

Conclusion: ¹⁸FDG-PET appears to effectively characterize patients at low risk for malignant transformation of SPN discovered by CT. Blinded, randomized controlled trials are needed for further evaluation.

Purpose: To examine the value of PET in diagnosis and staging of suspected lung cancer.

Methods: 20 (13 male; mean age: 56 yr., range: 22-83 yr.) patients with chest X-ray findings suspicious of malignancy were staged a) “clinically” (X-ray, history/physical examination, lung function), b) by chest CT of thorax/upper abdomen, and c) by whole-body PET (GE Advance, visual analysis). The CT and PET studies were performed within 2 weeks of admission and read blinded to all information except the chest X-ray report. The decision to refer to mediastinoscopy/thoracotomy was made by a tumor board using clinical information, CT and PET findings. In principle, suspected metastatic lesions were biopsied before surgery. The gold standard was histology from biopsy or thoracotomy, or resolution of the X-ray findings and symptoms.

Results: One patient was excluded because of uncertain diagnosis. In 3 (15%) patients surgery was avoided mainly because of the PET findings. In one SCLC patient and one lymphoma patient, PET showed extensive disease, which changed the chemotherapy regime. Accuracy was 83% for clinical stage, 79% for CT and 77% for PET. Four (20%) false positive PET findings were caused by granuloma, pneumonia and BOOP. These nodules were only 1 to <3 cm, while malignant nodules were 2-8 cm. There were no false negative PET or CT studies.

Conclusion: FDG-PET is valuable in patients suspected for pulmonary malignancy, since thoracotomy was avoided in 15% of patients and in 10% of patients more extensive disease was found which changed the chemotherapy regime.

Purpose: The study evaluates whether adjusting the dose of FDG injected by the patient's body surface area and the serum glucose level will produce a SUV with less standard error.

Methods: The study is a prospective study. For the period of 4/1999–5/1999, the patient received various dose of FDG as available from radiopharmacy. The Standardized Uptake Value Maximum (SUVmax) and Standardized Uptake Value Average (SUVavg) of the liver were calculated for PET scans at 40-50 minutes after injection. This is the control group. For the period of 6/1999–10/1999, the patients receiving a standard dose of FDG normalized by adjusting 15 mCi. per 1.73 sq.m. body surface area (BSA) and a proportional adjustment factor for serum glucose (serum glucose level / 5 mMol.). BSA is calculated by the formula = 0.007184 × (cm. height)^0.725 × (kg. weight)^0.425. The SUVmax and SUVavg of the liver at 40-50 minutes after injection. This is the study group.

Results and Conclusion: There are 29 subjects in the control group (CG) and 32 subjects in the study group (SG). Dose of FDG given ranges from 7.8–15 mCi in the CG, to 15.5–16.5 mCi in the SG. In the CG, liver SUVmax = (2.3 +/− s.d.0.37), SUVavg = (1.72 +/− s.d. 0.38). In the SG, liver SUVmax = (2.13 +/− s.d. 0.26), SUVavg = (1.88 +/− 0.22). The study shows that the liver SUVmax and SUVavg has a 42%, 72% respectively narrower standard deviation when the dose is adjusted for patient's body surface area and serum glucose level. This implies that such approach gives a more reproducible measurement of SUVmax and SUVavg in assessing tumor lesion.

Purpose: We evaluated the usefulness of FDG-PET in the assessment of patients with suspected pancreatic carcinoma who have previously undergone a Whipple procedure.

Methods and Materials: Attenuation-corrected FDG-PET was performed in 11 patients (5 males, 6 females, age range 52–76 years), with suspected recurrent pancreatic carcinoma after Whipple procedure. Recurrence was suspected based on clinical, laboratory (CA19-9 serum tumor marker level), or abdominal CT findings. Diagnostic validation was by histology in 2 patients and radiologic or clinical follow-up (5 to 48 months) in 9 patients. Changes in therapeutic management that were prompted by PET were tabulated.

Results: PET was concordant with the findings of abdominal CT in 7 patients (6 true-positive, 1 true-negative). PET detected unsuspected lung lesions in 1 of these patients that was subsequently confirmed by a chest CT. PET was discordant with abdominal CT in 4 patients. PET detected tumor recurrence in 3 of 4 patients in this group (27% of total) who had non-diagnostic CT and elevated CA19-9 serology. Chemotherapy was initiated in 2 of these 3 patients (18% of total), while the other patient died shortly after the PET study from pneumonia and recurrent tumor was confirmed at autopsy. The remaining 1 of 4 patients in the discordant group had a false-positive PET study due to relatively high FDG localization in a displaced loop of bowel.

Conclusion: PET is useful in localizing the tumor in post-Whipple patients with suspected recurrent pancreatic carcinoma and can impact their clinical management.

The purpose of this study was to determine if the first-pass of FDG can be used to measure regional blood flow in tumors in the absence of perfusion imaging with a known blood flow tracer.

PET scans were obtained in patients being evaluated for tumor perfusion and metabolism in a Phase I dose escalating protocol for Endostatin, a novel antiangiogenic agent. A two minutes perfusion scan was done with a bolus injection of 60 mCi of O-15 labeled water followed by a 10 mCi dose of FDG and four sequential scans consisting of a first pass two minutes scan and three 15 minutes scans. Regions of interest were drawn on two tumor sites for each scan. Blood flow was computed using a one-compartment model previously published by the authors. Linear regression analysis was carried out between the first pass FDG measured blood flow and O-15 measured blood flow (Figure 1)

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Figure 1.

Blood flow estimated from the first pass of FDG was linearly correlated with O-15 measured blood flow with an intercept of 0.01, slope of 0.86, and r squared regression coefficient of 0.74 (R = 0.86) for blood flow values of up to 0.6 ml/min/gm of tissue. These results suggests that in the absence of a perfusion tracer, the first pass of FDG provides an estimate of perfusion in a tumor within the limitations of incomplete extraction of FDG compared to O-15 water.

Purpose: FDG-PET images and EEG dipole modelling were used to localization of interictal epileptogenic foci. A multimodality approach with the analysis of FDG-PET images, EEG dipoles and anatomical images (MRI) were applied to patients with drug-resistant epilepsy.

Methods: Source location was determined using Brain Electromagnetic Source Analysis (BESA) program. The dipole location provided by BESA was then transformed into PET co-ordinates using the patient's MRI previously registered with the PET image. As a difference with other methods, no external markers are necessary.

Results: The study group includes ten drug-resistant epileptic patients. FDG hypometabolism was found in all patients. Abnormalities in glucose uptake were always ipsilateral to the EEG dipole. However, quantitative analysis of FDG-PET within hypometabolic areas showed no significant correlation between decrease glucose uptake and location of EEG-dipole source. The comparison of the results using both methods shows that the dipole location matches the FDG-PET hypometabolic area for all the patients. Combining the spatial localization on FDG-PET with the temporal accuracy of EEG dipole source aids in the exact localization of the epileptogenic focus.

Conclusion: As a conclusion, the results show that projection of EEG dipole data onto FDG-PET may play a key role in the indication of surgery for the treatment of drug-resistant epileptic patients, provided it is simple and easy to perform.

Purpose: At the University Of Pittsburgh Medical Center, over 100 oncology studies have been performed using a combined PET/CT scanner. The scanner is a prototype, which combines clinical PET and clinical CT imaging in a single unit. The sensitivity achieved using three-dimensional PET imaging as well as the use of the CT for attenuation correction and image fusion make the device ideal for clinical oncology. Clinical indications imaged on the PET/CT scanner include, but are not limited to, tumor staging, solitary pulmonary nodule evaluation, and evaluation of tumor reoccurrence in melanoma, lymphoma, colorectal cancer, lung cancer, pancreatic cancer, head and neck cancer, and renal cancer.

Methods: For all studies, seven millicuries of F¹⁸-fluorodeoxyglucose is injected and a forty-five minute uptake period is allowed prior to positioning the patient in the scanner. A helical CT scan is acquired over the region, or regions of interest followed by a multi-bed whole body PET scan for the same axial extent. The CT scan is used to correct the PET data for attenuation. The entire imaging session lasts 1–1.5 hours depending on the number of beds acquired, and is generally well tolerated by the patient.

Results and Conclusion: Based on our experience in over 100 studies, combined PET/CT imaging offers significant advantages, including more accurate localization of focal uptake, distinction of pathology from normal physiological uptake, and improvements in evaluating therapy. These benefits will be illustrated with a number of representative, fully documented studies.

Purpose: The aim of this study was to evaluate the role of FDG-CDET for the detection of primary oesophageal tumour, lymph node involvement and distant extension before surgery.

Methods and patients: In patients fasting for 6h or more, 150-250 MBq of ¹⁸F-FDG were injected i.v. and 2D imaging (whole-body scan and at least a tomoscintigram) was started 45 min. later, using a PICKER gamma camera. We studied 14 patients (pts). All of them were operated on (mean time between FDG and surgery: 5.4 ± 3.8 days) and staging results were correlated with post surgical histology.

Results: The primary lesion took up FDG in all cases but one (FN in a 5 mm lesion). The primary NM staging of these 14 pts was negative with FDG-CDET in 7 cases (4 TN and 3 FN corresponding to an invasion of satellite lymph nodes in 2 cases and to a metastatic infracentimetric subdiaphragmatic lymph node in one case) and positive in 7 cases (7 TP corresponding to 10 foci), revealing in 4 cases a sub-diaphragmatic lymph node extension unknown prior to FDG-CDET. One pt referred for characterisation of an oesophageal lesion (failure of multiple biopsies) had an intense focus of FDG uptake in this area (TP confirmed by surgery). The overall sensitivity was 13/14 = 93% on a per patient basis and 21/25 = 84% on a per lesion basis. Specificity on a per lesion basis was 5/5 = 100%.

Conclusion: These first results, obtained in an indication of FDG not frequently evaluated even with dedicated PET systems, seem very promising, the oesophageal neoplastic lesions appearing to take up FDG with a high intensity.