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

Purpose: To examine one potential clinical application of dedicated devices for positron emission mammography.

Background: Dedicated devices for breast imaging with FDG have technical specifications that appear well-suited for detecting small breast cancers, including registration with x-rays, high count sensitivity, and spatial resolution in the 2-3 mm range.

Methods: In IRB-approved clinical trials, patients who were scheduled for biopsy for suspicious findings on x-ray mammograms were injected with 10-20 mCi FDG intravenously one to two hours prior to x-ray guided core biopsy or lumpectomy. Positron emission mammograms using a dedicated device were performed just before biopsy, and results compared to final histopathology.

Results: Three patients whose cancers were missed on initial x-ray mammograms or whose mammograms contained subtle abnormalities that were not strongly suspicious for cancer, were shown to have very suspicious hot spots on positron emission mammograms. These patients were later confirmed to have cancer.

Discussion: The role for dedicated devices for positron emission mammography is evolving. Finding cancers that are either mammographically occult or have low indices of suspicion is a potential application for this technique. Further clinical and technical work will be needed to better define the strengths and weaknesses of the device in this application.

PET provides diagnostic information currently not available with traditional imaging. Retrospective analysis was performed of 104 patients with primary or recurrent melanoma who underwent PET for staging to determine sensitivity/specificity compared to body CT. 157 PET and 70 CT scans were analyzed with a mean follow up of 26 months. Metastatic events were confirmed with positive histology (73%) or documented disease progression.

PET demonstrated 86% sensitivity and 97% specificity in 41 patients with metastasis. CT showed 57% sensitivity and 70% specificity in 30 patients with metastasis. Exclusion of areas not evaluated on CT (head, neck/supraclavicular, and extremities) increased CT sensitivity to 68%. Fifty-three patients underwent 67 consecutive CT and PET scans that detected 132 metastases in 30 individuals. PET detected a greater percentage of metastases (83%) compared to CT (56%), and specifically, in the soft tissue, neck, peripheral/mediastinal/intraabdominal lymph nodes, and small bowel. PET detected 100% of mediastinal metastasis while CT detected only 67%. Surprisingly, PET detected 84% of lung parenchymal metastasis compared to 72% with CT.

PET is more sensitive and specific than CT for detection of melanoma metastasis and should be considered the primary staging study upon suspicion of recurrent disease. PET shows greater ability to detect soft tissue, small bowel, and lymph node metastasis that do not meet criteria designated as abnormal by CT. Likewise, CT does not routinely evaluate the supraclavicular area, neck, or upper/lower extremities. However, even when these sites are excluded from comparative analysis, PET is superior to CT in detecting melanoma metastasis.

Purpose: Dedicated PET-(fluorine-18)-fluorodeoxyglucose (FDG) studies were interpreted with the corresponding anatomic images (MR or CT) using image fusion display to improve spatial accuracy for the interpreter and the referring physician.

Methods: The image-fusion display system was designed in-house and allows manual alignment and display of one image volume as an overlay on the other which has improved accurate correlation of physiological and anatomical information for more than 50 patient studies.

Results: A case of a patient with left foot recurrent melanoma is presented for which the PET scan showed a large focus of activity just lateral to the urinary bladder. Image fusion confirmed that the PET focus corresponded to an abnormal lymph node on the follow-up CT scan. In a case of bladder carcinoma which included bladder augmentation, altered surgical anatomy rendered interpretation of the FDG-PET images difficult. The fusion with the patient's CT scan allowed evaluation of the altered physiology due to the altered surgical anatomy which permitted accurate image interpretation. In a case of pelvic lymphoma, the FDG-PET scan showed intense activity adjacent to the acetabulum and possibly within it. Image fusion allowed accurate localization of the patient's primary lesion with the additional benefit of showing activity extending into the adjacent bone.

Conclusion: Image fusion of tomographic, anatomic and physiologic information permits accurate lesion localization including separation of soft tissue from bone. The image-fusion technique facilitates image-guided biopsy by providing accurate anatomic localization.

Purpose: The purpose of this study was to evaluate the difference, if any, in lesion detection in ATN and NATN images.

Methods: Sixty-one consecutive patients having clinical whole body FDG PET scans for oncologic indications were included. The patients were administered 10-20 mCi FDG intravenously, and imaging on the Advance (GE Medical Systems) was started 45 min-1 h after injection. The emission images were acquired for 4 min and the transmission images for 3 min per bed position. The images were reviewed on the vendor-provided workstation. Four of the interpreting physicians read the ATN images first, and the other read the NATN images first. The interpreting physicians were asked to determine if any lesions were seen on only the ATN or NATN images (discordant findings) and to describe differences in the images not affecting overall interpretation.

Results: In the 61 patients, 3 discordant findings with abnormalities on the ATN images but not on the NATN images included the following: lung nodule, AP window node, and small para-aortic node. Observations that did not affect overall interpretation include the following: transmission scan helped localize lesion to be below instead of above the diaphragm; AT-N image better demonstrated liver metastasis; benign lung lesion seen only on ATN image (3 cases); pretracheal node seen better on NATN images; and low grade hilar activity on NATN not seen on ATN images.

Conclusion: These results demonstrate that the ATN images detect more lesions than the NATN images, and that reviewing NATN images may not be necessary. A different method for performing this evaluation is now being undertaken.

Purpose: Whole-body positron emission tomography (PET) with [F-18]fluorodeoxyglucose (FDG) is an important tool in the management of patients with cancer. While the sensitivity of FDG PET for tumor localization is most often reported to be ≥ 85%, the specificity is frequently found to be lower. One limitation of whole-body PET imaging is the confounding effect of normal physiologic FDG accumulation in kidneys, ureters, bladder, stomach and bowel. Also, highly metabolically active tissues such as brain and muscle can mask detection of adjacent abnormalities. Interpretation of functional PET images can be improved by correlation with anatomic imaging, e.g. CT or MRI. The utility of both visual comparison and retrospective fusion of PET with previously acquired morphologic studies may be, however, limited by the time interval between image acquisition and patient positioning differences.

Results: In our experience with over 150 examinations using a unique combined PET/CT scanner, we have frequently found that the direct registered images were critical to correct study interpretation. In this work, we review the beneficial results of a combined PET/CT tomograph for diagnosis/staging and localization of malignancy. We will further present specific examples of clinical questions uniquely addressed by PET/CT, and their impact on patient management.

Conclusion: Acquisition of co-registered PET and CT images in the same scanning session may enable physicians to more precisely discriminate physiologic uptake and tumor. Our initial experience suggests that this combined PET/CT device may improve the accuracy of PET, and in so doing, enhance the value of diagnostic PET in oncologic applications.

Purpose: To evaluate the utility of FDG-PET in detecting primary tumors in patients with metastatic disease from unknown primary tumors.

Methods: 12 patients with metastases from unknown origin after unsuccessful conventional diagnostic procedures were studied. 5 had lymph node metastases (2 axillary, 2 cervical, 1 mediastinal), 3 multiple metastases, 1 in the lung, 1 in the cava vein, 1 in the brain and 1 in adrenal glands. Patients received 400MBq FDG intravenously, and whole body images were acquired 60 min. after injection with an ECAT EXACT HR+. PET results were compared with histological and clinical findings.

Results: All but one metastatic lesion was identified by PET. Additional metastases were visualized in 4 patients. In one helped to guide biopsy for histological diagnosis. In 4/11 patients FDG-PET did not reveal lesions suspected to be primary tumor. FDG-PET identified primary tumor in 8/11 patients (breast: 2, pancreas: 2, base of tongue: 1, adrenal gland: 1, lung: 1, stomach: 1). In 4 of them (33% of total) primary tumor was confirmed either histologically or by the clinical evolution (breast: 2, lung: 1, pancreas: 1). In 1 patient FDG-PET was false positive (base of tongue). 3 patients positive FDG-PET have not yet been confirmed. FDG-PET influenced therapeutic procedures in 4 patients (33% of total). 2 underwent surgery (breast), 1 received specific chemotherapy (lung) and 1 palliative chemotherapy (pancreas).

Conclusions: Our preliminary results suggest that FDG-PET is a non-invasive technique useful in the detection of unknown primary tumors, can influence in selecting appropriate therapeutic management and could guide biopsies for histologic analysis.

Purpose: Positron Emission Tomography (PET) using ¹⁸F-Fluorodeoxyglucose (¹⁸FDG) has been extensively used to stage patients with different malignancies. The purpose of our study was to compare ¹⁸FDG-PET to Computed Tomography (CT) in the management of patients with malignant mesothelioma.

Methods: Eight patients (6 males, 2 females; mean age 67, range 53 to 78 years) underwent ¹⁸FDG-PET scan between March 1997 and November 1998. PET scan of the neck, thorax and upper abdomen was performed 45 minutes after the intravenous injection of 10 mCi of FDG in fasted patients; attenuation correction was applied in all cases. The findings were compared with CT and pathology.

Results: PET and CT were concordant in 3 patients. PET was superior to CT in 5 cases (1 patient was downgraded from widespread to localized disease, 2 patients were upstaged from localized to widespread disease, PET confirmed equivocal findings by CT in 2 cases). In 1 patient PET and CT missed local spread of tumor to diaphragm and pericardium, showing instead disease confined to pleural space.

Conclusions: Our results suggest that PET is more accurate than CT in the staging of patients with mesothelioma.

Purpose: Survival of patients (pts) undergoing “curative” treatment for colorectal carcinoma remains poor. Retrospective studies suggest that F-18 FDG PET is more accurate than CT for restaging suspected recurrent disease and favourably impacts management. The aim of this study was to confirm this by prospective analysis.

Patient Population and Methods: 102 consecutive patients for whom the referring clinicians had prospectively committed to a treatment plan based on conventional staging investigations and who then underwent F-18 FDG PET scanning were evaluated for management change and outcome. The accuracy of PET results was assessed by surgical findings or clinical follow-up.

Results: Overall PET changed management in 66/102 (65%) pts including14 pts changed from observation to active treatment after PET localized disease and 6 pts planned for local therapy to observation after negative PET. Planned surgery was cancelled in 28 pts whereas surgery was initiated in 11 pts. Radiotherapy was prevented in 5 pts, initiated in 11 and the radiation field altered in 5 others. The accuracy of the PET results could be assessed in 63/66 (95%) pts in whom management was changed. Relapse was confirmed in 50/51 pts with a positive PET but disease extent was underestimated in 4 cases. False negative PET results were confirmed in 5 cases.

Conclusion: FDG PET has a high and appropriate impact on patient management in patients with suspected recurrent disease. PET can miss small volume disease but the major benefit of PET is to prevent futile attempts at local salvage therapies.

Purpose: Evaluation of 3D clinical whole-body FDG PET imaging using recent improvements in data correction and reconstruction methods.

Methods: Phantom studies following the NEMA NU 2-2000 draft were performed to evaluate count loss and accuracy of attenuation and scatter correction algorithms. Phantom results were used to estimate 3D vs. 2D efficiency. For patient studies, an established 2D imaging protocol (9 min emission, 3 min transmission acquisition per bed position, commencing 60 min after injection of 15 mCi FDG) was used. This was followed by a 3D acquisition of the same duration, commencing approximately 110 min later, so that 3D acquisition was performed with approximately 50% lower patient activity than 2D. Images were compared in terms of anatomic structural definition and visible artifacts.

The count loss study showed that in a dose range of 10-15 mCi, 3D produced an approximately two-fold increase in effective NEC compared to 2D. The phantom imaging study showed slightly improved target to background ratios for both hot and the cold “lesions” when using 3D imaging. In 5 patients studied so far, comparison of 2D and 3D studies demonstrated no systematic differences in image quality between the two methods.

Conclusion: 3D whole-body imaging with improved image reconstruction may permit a two-fold reduction in emission acquisition time or injected dose, without decrease in image quality compared to standard 2D imaging techniques.

Purpose: The purpose of this study was to assess the accuracy in localizing mediastinal, hilar and intraparenchymal lymphadenopathy in patients with primary lung carcinomas, using FDG-PET and CT of the thorax and to correlate with surgical pathology.

Method: Thirty-five patients with primary lung carcinomas and minimal metastatic lymph node involvement, (either N⊘ or N1 disease) underwent FDG-PET and CT of the thorax prior to surgical intervention. Both FDG-PET and CT of the thorax were blindly read independent of one another.

Results: Histologically, 23 patients had negative lymph nodes (N⊘) and 12 patients had N1 disease. The imaging performance characteristics for FDG-PET and CT of the thorax in N⊘/N1 disease was evaluated and reported in Table 1

Conclusion: This study demonstrates the higher specificity, accuracy, PPV, and NPV of FDG-PET over CT of the thorax in patients with minimal lymph node disease.