Pitfalls in oncologic diagnosis with FDG PET imaging: physiologic and benign variants.

A rapidly emerging clinical application of positron emission tomography (PET) is the detection and staging of cancer with the glucose analogue tracer 2-[fluorine-18]fluoro-2-deoxy-D-glucose (FDG). Proper interpretation of FDG PET images requires knowledge of the normal physiologic distribution of the tracer, frequently encountered physiologic variants, and benign pathologic causes of FDG uptake that can be confused with a malignant neoplasm. One hour after intravenous administration, high FDG activity is present in the brain, the myocardium, and--due to the excretory route--the urinary tract. Elsewhere, tracer activity is typically low, a fact that allows sensitive demonstration of tracer accumulation in many malignant neoplasms. Interpretive pitfalls commonly encountered on FDG PET images of the body obtained 1 hour after tracer administration can be mistaken for cancer. Such pitfalls include variable physiologic FDG uptake in the digestive tract, thyroid gland, skeletal muscle, myocardium, bone marrow, and genitourinary tract and benign pathologic FDG uptake in healing bone, lymph nodes, joints, sites of infection, and cases of regional response to infection and aseptic inflammatory response. In many instances, these physiologic variants and benign pathologic causes of FDG uptake can be specifically recognized and properly categorized; in other instances, such as the lymph node response to inflammation or infection, focal FDG uptake is nonspecific.

Diagnosis of spine metastases by FDG imaging using a gamma camera in the coincidence mode.

PURPOSE: To illustrate the detection of metastatic lung cancer using a conventional dual detector gamma camera modified to operate in the coincidence mode to image the static distribution of 2-deoxy-2-[F-18]fluoro-D-glucose (FDG). METHODS: A patient with known lung cancer underwent FDG imaging to evaluate the extent of metastatic disease. Twenty-three-minute emission image acquisition at one bed position using a dual detector coincidence gamma camera was performed to evaluate the entire chest and upper abdomen. RESULTS: In addition to detecting the malignant lung nodule, mediastinal lymph node metastases and a rib metastasis, symptomatic metastases to lower thoracic and upper lumbar vertebral bodies, which were not identified on radiographs, CT, or bone scan, were shown clearly by FDG coincidence gamma camera imaging. CONCLUSION: FDG tumor imaging in the body is feasible using a dual detector gamma camera operating in coincidence mode and may find an important role in a certain subset of FDG tumor imaging.

Oncologic diagnosis with 2-[fluorine-18]fluoro-2-deoxy-D-glucose imaging: dual-head coincidence gamma camera versus positron emission tomographic scanner.

PURPOSE: To compare the performance of a dual-head single photon emission computed tomographic (SPECT) Anger camera operated in coincidence mode with that of a dedicated positron emission tomographic (PET) scanner in the imaging of cancer with 2-[fluorine-18]fluoro-2-deoxy-D-glucose (FDG). MATERIALS AND METHODS: Thirty-one patients with known or suspected malignant neoplasms underwent imaging with both methods, and the images were read blindly. Diagnostic performance on a lesion-by-lesion basis was compared with attenuation-corrected PET as the standard of reference. RESULTS: Of a total of 109 discrete lesions depicted at PET, 60 (relative sensitivity, 55%) were identified on the coincidence-mode images. Of the nodules or masses depicted at PET, 13 (93%) of 14 lung nodules or masses, 20 (65%) of 31 mediastinal lymph nodes, five (71%) of seven lesions in the neck, five (55%) of nine axillary lymph nodes, 11 (50%) of 22 bone metastases, and six (23%) of 26 abdominal tumor deposits were correctly identified on the coincidence gamma camera images. CONCLUSION: These preliminary findings indicate FDG imaging with a modified dual-detector gamma camera operating in coincidence mode can depict many of the lesions depicted with a PET scanner, particularly in the lungs. Sensitivity for lesions detected at dedicated FDG PET was poor in the abdomen and in all locations outside the lungs for tumor deposits generally less than 1.5 cm in short-axis diameter.

Focal fluorine-18 fluorodeoxyglucose accumulation in inflammatory pancreatic disease.

Focal 2-deoxy-2[fluorine-18]fluoro-D-glucose (FDG) uptake on positron emission tomography (PET) in a pancreatic mass has been reported as a specific finding for pancreatic carcinoma. Inflammatory conditions of the pancreas and associated clinical circumstances yielding similar findings have not yet been fully defined. Among 42 patients studied by attenuation-corrected FDG PET for pancreatic disease, 12 with focal FDG uptake in the pancreas were identified as having no underlying neoplasm based on surgical findings, biopsy results, and long term clinical and imaging follow up. Focal FDG accumulation in the pancreas with standardized uptake values ranging from 3.4 to 11.2 on FDG PET was ultimately found to be related to inflammation rather than neoplasm. This occurred in pancreatic masses in which clinical and laboratory evidence of acute pancreatitis was equivocal or entirely lacking, as well as in the setting of acute pancreatitis and after recovery from acute pancreatitis. Inflammation can give rise to focal FDG uptake in the same intensity range as pancreatic neoplasm, even when clinical, laboratory and computed tomographic findings suggestive of an inflammatory etiology are equivocal or absent.

Imaging of the pancreas and related diseases with PET carbon-11-acetate.

UNLABELLED: The purpose of this study was to evaluate [1-11C]-acetate as a tracer for functional imaging of the pancreas and related diseases using position emission tomography (PET). METHODS: Thirty-three patients underwent 30 min of dynamic attenuation-corrected PET after intravenous administration of 740 MBq (20 mCi) of [1-11C]-acetate. RESULTS: The normal pancreas demonstrates prompt uptake of [1-11C]-acetate and is visualized as early as 2 min post-injection, with maximal activity achieved by 5 min. Subsequent clearance of tracer from the pancreas is slow relative to adjacent organs and background, such that by 10 min post-injection the pancreas is the most prominent organ in the imaging field of view. Pancreatic uptake of [1-11C]-acetate was unaffected by pancreatic endocrine insufficiency, but is absent in chronic pancreatitis complicated by exocrine insufficiency. Moderately reduced [1-11C]-acetate uptake was observed in acute uncomplicated pencreatitis. The level of tracer accumulation was substantially reduced in phlegmatous masses complicating pancreatitis and in chronic mass forming pancreatitis. Adenocarcinoma of the pancreas likewise demonstrated no significant uptake of [1-11C]-acetate. CONCLUSIONS: Accumulation of [1-11C]-acetate by the pancreas allows rapid metabolic imaging using PET, and may be a useful metabolic probe for the study of pancreatic physiology and disease.

Metastatic prostate cancer: initial findings of PET with 2-deoxy-2-[F-18]fluoro-D-glucose.

PURPOSE: To evaluate the accuracy of positron emission tomography (PET) with 2-deoxy-2-[fluorine-18] fluoro-D-glucose (FDG) in the detection of osseous and soft-tissue metastases of prostate cancer. MATERIALS AND METHODS: Thirty-four patients (mean age, 71 years) with biopsy-proved prostate cancer and known or suspected metastatic disease were examined. Blinded interpretation of the PET images was compared with bone scan, CT, and clinical follow-up findings. RESULTS: In 202 untreated osseous metastases in 22 patients, the sensitivity of FDG PET was 65% (131 of 202 metastases), with a positive predictive value of 98% (131 of 133 positive findings). The estimated standardized uptake value in metastases was 2.1-5.7. Soft-tissue metastases to the lymph nodes or liver were identified, but evaluation of pelvic lymph node metastases was severely limited because of bladder tracer activity. CONCLUSION: FDG PET can help identify osseous and soft-tissue metastases of prostate cancer with a high positive predictive value but is less sensitive than bone scintigraphy in the identification of osseous metastases.

Simultaneous transmission/emission myocardial perfusion tomography. Diagnostic accuracy of attenuation-corrected 99mTc-sestamibi single-photon emission computed tomography.

BACKGROUND: The purpose of the present study was to assess the diagnostic performance of attenuation-corrected (AC) stress 99mTc-sestamibi cardiac single-photon emission computed tomography (SPECT) for the identification of coronary heart disease (CHD). METHODS AND RESULTS: With a triple-detector SPECT system with a 241Am transmission line source, simultaneous transmission/emission tomography (TCT/ECT) was performed on 60 patients with angiographic coronary disease and 59 patients with < or = 5% likelihood of CHD. Iteratively reconstructed AC stress 99mTc-sestamibi perfusion images were compared with uncorrected (NC) filtered-backprojection images. Normal database polar maps were constructed from AC and NC images for quantitative analyses. From the low-likelihood patients, the visual and quantitative normalcy rates increased from 0.88 and 0.76 for NC to 0.98 and 0.95 for AC (P < .05). For the detection of CHD, the receiver operating characteristic curves for the AC images demonstrated improved discrimination capacity (P < .05), and sensitivity/specificity values increased from 0.78/0.46 (NC) to 0.84/0.82 (AC) with visual analysis and from 0.84/0.46 (NC) to 0.88/0.82 (AC) with quantitative analysis. For localization of stenosed vessels, visual and quantitative sensitivity values were 0.51 and 0.63 for NC and 0.64 and 0.78 for AC images (P < .05), respectively. CONCLUSIONS: TCT/ECT myocardial perfusion imaging significantly improves the diagnostic accuracy of cardiac SPECT for the detection and localization of CHD. Clinical use of TCT/ECT imaging deserves serious consideration.

Triple-head SPECT with 2-[fluorine-18]fluoro-2-deoxy-D-glucose (FDG): initial evaluation in oncology and comparison with FDG PET.

PURPOSE: In patients with cancer, performance was assessed of a commercially available triple-head gamma camera fitted with ultra-high energy parallel-hole collimators performing single photon emission computed tomography (SPECT) with 2-[fluorine-18]fluoro-2-deoxy-D-glucose (FDG). Results were compared with those of positron emission tomography (PET) with FDG. MATERIALS AND METHODS: Performance characteristics were first determined in phantom studies for FDG PET and triple-head gamma camera SPECT systems. In 13 patients with malignancies, FDG PET was followed by SPECT of the same region, and imaging results were independently assessed. RESULTS: Sensitivity of the PET and SPECT systems was 58.3 counts/MBq/min and 4.5 counts/MBq/min, respectively. Reconstructed spatial resolution was approximately 7 mm for PET and 20 mm for SPECT. All known cancer foci were detected at PET. SPECT depicted 11 of the 22 lesions detected at PET, but only five of the 14 lesions less than 3 cm in diameter. CONCLUSION: FDG SPECT performed with a specially collimated triple-head gamma camera depicted some cancers but had an unacceptably low sensitivity compared with PET for lesions less than 3 cm in diameter. PET is preferable for detecting small cancers.

Synthesis of a nonpeptide carbon-11 labeled substance P antagonist for PET studies.

CP 96,345 is a nonpeptide high affinity antagonist of the substance P (NK1) receptor. The radiosynthesis of [11C]CP 96,345 suitable for Positron Emission Tomography (PET) applications is described. [11C]CP 96,345 was prepared by O-methylation of a desmethyl precursor via in situ generation of its phenolate salt. The in vivo tissue distribution of [11C]CP 96,345 in guinea pigs (n = 2) at 5 and 30 min was determined. Uptake was low in brain (approximately 0.04% dose/g) and highest (approximately 1-2% dose/g) in the spleen and lungs. The present findings indicate that the use of [11C]CP 96,345 in PET might be more applicable to the study of substance P receptors in peripheral tissues involved with inflammatory disease and arthritis.

Insulin regulation of Na/K pump activity in rat hepatoma cells.

Insulin rapidly increases Na/K pump activity in HTC rat hepatoma cells in tissue culture, as measured by the ouabain-sensitive influx of the potassium analogue 86Rb+. Increased influx is observed within minutes and is maximal (70% above control) within 1-2 h. The effect appears to be mediated by the insulin receptors, as: the concentration dependence on insulin is identical to that for insulin induction of tyrosine aminotransferase and stimulation of 2-aminoisobutyric acid transport, proinsulin is 6% as potent as insulin, and the effect is blocked by anti-receptor antibodies. The early stimulation of potassium influx is not blocked by cycloheximide and is not associated with an increased number of pump sites as measured by 3H-ouabain binding. The insulin effect is blocked by amiloride, which blocks sodium influx, and is mimicked by the sodium ionophore monensin, which increases sodium influx and intracellular accumulation. Insulin also rapidly increases the initial rate of 22Na+ influx, suggesting that insulin may enhance Na/K pump activity, in part, by increasing intracellular sodium concentration. Incubation of HTC cells with insulin for 24 h causes complete unresponsiveness to the insulin induction of transaminase and stimulation of amino acid transport, a phenomenon mediated by postbinding mechanisms. In contrast, similar incubation with insulin does not cause unresponsiveness to the insulin stimulation of Na/K pump activity. Therefore, the site of regulation of responsiveness to insulin must be distal to, or separate from, those events causing stimulation of ion fluxes.