Fluorodeoxyglucose positron emission tomography studies in the diagnosis and staging of clinically advanced prostate cancer.

OBJECTIVE: To determine the value of 18F-fluoro-2-deoxyglucose (FDG) positron-emission tomography (PET) studies in evaluating patients with advanced prostate cancer. PATIENTS AND METHODS: FDG-PET scans were taken in 30 patients with advanced prostate cancer 1 h after an injection with 555 MBq of FDG. Patients were scanned from the base of the skull to the inguinal region (including the pelvis). They were also assessed by computed tomography (CT) of the abdomen and pelvis, and bone scintigraphy, to evaluate them for metastases. RESULTS: Thirteen patients had locally extensive prostate cancer and 17 had metastatic disease. Twenty of the 30 patients were positive for radioisotope uptake in the prostate or extraprostatically. The patients with PET-detected prostate cancer were untreated (seven), treated hormonally while they had rising PSA levels (eight), or treated hormonally with a detectable but stable PSA (five). The remaining 10 patients were negative for FDG uptake in the prostate or any metastatic sites; these 10 patients were receiving hormone therapy, with undetectable PSA levels. CONCLUSION: FDG-PET imaging is not a useful test in evaluating advanced prostate cancer in patients being treated and who have an undetectable PSA level. Staging of advanced prostate cancer may be enhanced by FDG-PET imaging in patients who are untreated, who have had an incomplete response to therapy, or who have a rising PSA level despite treatment.

Positron emission tomography of the thyroid, with an emphasis on thyroid cancer.

The role of Positron Emission Tomography (PET) using 18F-fluorodeoxyglucose (FDG) in the management of thyroid cancer is discussed. It is important to ensure that patients are relaxed because uptake of FDG in tense or active muscles in the neck and larynx can be misinterpreted as metastases. The major role for PET is in patients where the stage of disease is uncertain, usually the result of discordant negative 131I scan and a positive serum thyroglobulin (Tg) values. PET identifies the source of Tg production in 50-80% of patients. PET scan can be negative in well differentiated cancers which retain the ability to trap iodine. This can result in a 'flip/flop', with negative PET, positive radio-iodine scan, or positive PET, negative radioiodine scan. PET is also valuable in identifying the source of calcitonin production in patients with medullary thyroid cancer. When focal uptake is seen in the thyroid of patients who are scanned for non thyroidal reasons, the likelihood of primary thyroid cancer is high. In contrast diffuse uptake of FDG in the thyroid is usually the result of auto-immune thyroid disorders.

Fluorodeoxyglucose positron emission tomography studies in diagnosis and staging of clinically organ-confined prostate cancer.

OBJECTIVES: To determine the value of 18-fluoro-2-deoxyglucose (FDG) positron emission tomography (PET) studies in the evaluation of patients with organ-confined prostate cancer. This imaging method has previously found little usefulness in localized prostate tumors because of excretion of the isotope into the urine, masking any lower urinary tract lesions. We evaluated this imaging modality using hydration, furosemide, and bladder emptying before the procedure to evacuate the nonspecific isotope in the urine. METHODS: FDG PET scans were performed on 24 patients diagnosed with clinically organ-confined prostate cancer. No patient had received any prior treatments for the cancer. FDG PET scans were performed 1 hour after injection of 15 mCi of F-18 deoxyglucose. Patients were scanned from the base of the skull through the inguinal region (including the pelvis). Additional signal attenuation-corrected images of the inguinal region were acquired 30 minutes after intravenous injection of 40 mg of furosemide. The final diagnosis was made by histologic examination, correlative imaging studies, and/or clinical follow-up. RESULTS: FDG PET studies were negative in 23 of the 24 organ-confined prostate cancers and the study was only faintly positive in 1 tumor (4.0% sensitivity). CONCLUSIONS: FDG PET is not a useful test in the evaluation of clinically organ-confined prostate cancer.

PET in differentiation of recurrent brain tumor from radiation injury.

The annual incidence of primary intracranial tumors is 7 to 19 cases per 100,000 people. The general approach to the treatment of brain neoplasms is surgical resection of solitary lesions or limited disease, followed by radiation therapy with or without chemotherapy. Multiple metastatic lesions are usually treated with whole-brain radiation. Radiation injury occurs in 5% to 37% of cases and can be difficult to differentiate from residual or recurrent malignancy by MRI. PET has been used to differentiate radiation injury from malignancy on the basis of differences in glucose uptake. Recent studies have reported the sensitivity and specificity of PET to be 81% to 86% and 40% to 94%, respectively. This article reviews the classification of primary brain tumors, the histologic changes associated with radiation injury, and the diagnostic and prognostic information provided by PET.

The effect of fluorine-18 fluorodeoxyglucose positron emission tomography on the management of cutaneous malignant melanoma.

PURPOSE: To assess the effect of positron emission tomography (PET) with fluorine-18 fluorodeoxyglucose (FDG) on the treatment of patients with cutaneous malignant melanoma. MATERIALS AND METHODS: We retrospectively reviewed the medical records of 38 patients with newly diagnosed (n = 25) and recurrent (n = 13) cutaneous melanoma who were referred for evaluation with FDG PET imaging at our institution. We compared the PET findings with computed tomography (CT), which was available in 21 (55%) patients, and tabulated the changes in the diagnostic evaluation and therapeutic management that were prompted by PET during a follow-up period of 10 to 36 months. RESULTS: Compared with PET, the extent of disease was underestimated by CT in 5 (13%) patients. Planned surgical resection of metastases was canceled in two of these patients. In another patient, surveillance PET detected an unsuspected hypermetabolic abdominal mass that was noted on a subsequent CT to arise from the small bowel. The mass was found to be jejunal metastatic melanoma at the time of resection. Overall, PET influenced surgical management in 3 (8%) patients, but it did not affect the wait-and-watch strategy or decision to initiate immunotherapy in the others. CONCLUSIONS: FDG PET contributes important information not provided by CT and has a substantial effect on the clinical management of patients with malignant melanoma.

Positron emission tomography detection of osseous metastases of renal cell carcinoma not identified on bone scan.

The clinical utility of positron emission tomography (PET) in renal cell carcinoma (RCC) has not been determined. We describe a case in which metastatic RCC undetected by traditional staging methods was accurately staged by PET. A 77-year-old man presented with a 20-lb weight loss and bilateral renal masses. Plain radiographs, bone scintigraphy, and alkaline phosphatase were normal. PET imaging confirmed the right renal mass and revealed several metastatic bone lesions, confirmed by biopsy. The patient died 7 months after diagnosis. This case illustrates the potential superiority of PET in evaluating skeletal metastases of RCC.

Effect of atropine and sincalide on the intestinal uptake of F-18 fluorodeoxyglucose.

PURPOSE: Variable diffuse intestinal uptake of F-18 fluorodeoxyglucose (FDG) is commonly seen in patients undergoing positron emission tomography (PET) imaging. Diffuse high uptake can obscure a lesion, whereas occasional high focal uptake can mimic a lesion. The cause of intestinal FDG uptake and the parameters that influence the level of uptake are unknown. METHODS: We hypothesized that intestinal FDG uptake may result from smooth muscle peristalsis. We tested our hypothesis by comparing FDG uptake at baseline and after administration of two drugs (atropine and sincalide) that are known to affect intestinal motility. We performed FDG PET scans in random order in five healthy male volunteers without medication, after intramuscular administration of atropine, and after intravenous administration of sincalide. RESULTS: Qualitative comparison of the images before and after both medications did not show any significant difference in the level of intestinal FDG uptake. CONCLUSIONS: We conclude that intestinal FDG uptake is probably not caused by peristalsis. Mucosal uptake may be an alternative explanation.

A mathematical model for the distribution of fluorodeoxyglucose in humans.

UNLABELLED: The goals of this study were to define the total body distribution kinetics of 18F-fluorodeoxyglucose (FDG), to contribute to its radiation dosimetry and to define a suitable proxy for arterial cannulation in human FDG studies. METHODS: Time-activity FDG heart, lung, liver and blood data from paired fasting and glucose-loaded sessions in five adult human volunteers, together with published brain parameters, were incorporated into a multicompartmental model for whole-body FDG kinetics. Tau values were calculated from this model. We also compared the usefulness of activity in the left ventricle (LV), right ventricle (RV), left lung and right lung as proxy for arterial blood FDG sampling. RESULTS: No systematic difference was found in model parameters between the fasting and glucose-fed sessions, even for the parameter for transfer of FDG into the myocardium. Myocardial PET data fitted well to a model in which there is very rapid exchange indistinguishable from blood kinetics and transfer into an intracellular "sink." The lung data fitted to a simple sink representing the lung cells. The liver data required an additional intermediate exchange compartment between the plasma and a hepatic sink. In terms of total body distribution kinetics, unmeasured organs and tissues (probably the skeletal muscle and gut) become increasingly important with time and account for a mean of 76% of the decay-corrected FDG activity at infinity. Right lung activity, corrected to venous blood, represents the whole arterial blood curve better than the LV or RV. The tau values for radiation dosimetry of FDG in the heart, lungs, liver and bladder calculated from our model do not differ significantly from published results using other methods. Bladder tau decreased with voiding frequency and was markedly decreased with early voiding. CONCLUSION: Glucose loading state is not a good predictor of myocardial FDG uptake. The majority of FDG distribution at 90 min is in tissues other than the blood, brain, heart and liver. Bladder radiation will be much reduced if the patient voids early after FDG administration. Summed large volume right lung activity, normalized to venous blood activity, is a good proxy for arterial blood FDG sampling. The model presented may be expanded to include other FDG kinetics as studies become available.

SPECT and PET in the evaluation of coronary artery disease.

Cardiac positron emission tomography (PET) is an accurate method for assessing myocardial perfusion and metabolism in the evaluation of coronary heart disease. PET allows more accurate detection of myocardial ischemia than single photon emission tomography (SPECT). In addition, PET has higher spatial resolution and allows attenuation correction and the quantification of various physiologic parameters. PET with 2-(fluorine-18) fluoro-2-deoxy-D-glucose is considered the standard of reference for predicting improvement in regional or global left ventricular function after revascularization by identifying hibernating viable myocardium that shows diminished perfusion and preserved metabolism. Other less commonly used clinical applications of cardiac PET include assessment of myocardial oxygen consumption and fatty acid metabolism. The use of PET in myocardial imaging is expected to increase in the near future with the regional distribution of positron-emitting radiotracers and the emergence of relatively low-cost PET systems.

Usefulness of positron emission tomography imaging in the management of lung cancer.

Positron emission tomography imaging is useful for the characterization of the solitary pulmonary nodule and mediastinal staging. Potential future applications include extrathoracic staging to help to determine the ideal site for possible tissue diagnosis, to guide treatment plans, and to monitor the response to therapy and recurrence. Positron emission tomography may also predict prognosis. This review discusses the uses of positron emission tomography, the current literature, and the clinical guidelines for positron emission tomography imaging.

Uses and limitations of FDG positron emission tomography in patients with head and neck cancer.

OBJECTIVE: Numerous authors have reported the potential usefulness of positron emission tomography (PET). These studies have had conflicting results, at least partly owing to limited sample sizes. The objective of this study is to define not only the uses, but also the limitations of PET in patients with head and neck cancer. STUDY DESIGN: Nonrandomized, retrospective analysis of PET at an academic institution. METHODS: The authors performed 146 PET scans on 133 patients with head and neck cancer. Eighteen patients (19 PET scans) with thyroid disorders were excluded. A minimum 1 year of follow-up was available in 84 patients, who were separated into groups based on whether the PET was used to detect unknown primary cancers (n = 20), stage neck nodal and distant metastases (n = 8), monitor response to nonsurgical therapy (n = 22), or detect recurrent or residual cancers (n = 34). The results of PET were compared with results from computed tomography (CT) and magnetic resonance imaging (MRI) performed in the same patients. RESULTS: Of the unknown primary cancers, PET correctly identified 7 of 20 primary sites, giving a sensitivity of 35%. When combined with CT or MRI, the sensitivity increased to 40%. When used for detection of metastatic disease, PET demonstrated five of five nodal metastases (100%) and two of four distant metastases (50%). In evaluating the response to nonsurgical therapy, PET had a sensitivity of 50% and a specificity of 83% for detecting tumor at the primary site and a sensitivity of 86% and a specificity of 73% for detecting nodal disease. When used for evaluation of recurrent/residual disease, PET identified seven of seven cases of local recurrences/residual disease and had a specificity of 85%. PET also detected seven of seven cases of nodal disease and had a specificity of 89%. CONCLUSIONS: For staging purposes, PET is limited by its lack of anatomic detail. However, PET compares favorably with CT and MRI in detecting recurrent/residual cancers. PET imaging complements the more traditional imaging modalities (CT or MRI), especially for an unknown primary cancer.

Hot water swallows improve symptoms and accelerate esophageal clearance in esophageal motility disorders.

Cold liquid ingestion may precipitate episodes of dysphagia and chest pain in patients with spastic esophageal motility disorders. The effect of hot liquids on esophageal symptoms, esophageal peristalsis, and clearance and any potential therapeutic benefit in such patients has not been examined. Using esophageal scintigraphy and manometry, we have investigated the effects of hot water swallows on dysphagia, chest pain, and esophageal motility and clearance in patients with esophageal motility disorders. We studied 48 men and women with intermittent dysphagia to both solids and liquids, chest pain, and/or regurgitation. All patients underwent upper endoscopy, barium swallow, and esophageal manometry using standard techniques. Esophageal scintigraphy assessed esophageal transit time (ETT) and retrograde intraesophageal movement of bolus at baseline (22 degrees C) and after hot (60 degrees C) water swallows. Esophageal manometry assessed the amplitude and duration of esophageal contractions in response to baseline and hot water swallows. Patients were followed clinically for as long as 6 months to assess symptomatic response. We found that baseline esophageal scintigraphy revealed a mean ETT of 48.5 seconds; after hot water swallow, mean ETT was 27.8 seconds (p < 0.001). The number of secondary peaks at baseline was 3.5; after hot water swallow, it was 2.1 (p < 0.001). Baseline esophageal manometry showed a mean esophageal body contraction amplitude of 188 mm Hg (mean duration, 11.8 seconds) in response to wet swallows and 125 mm Hg (mean duration, 5.7 seconds) with hot water swallows (p < 0.001). Clinically, 28 (58%) of 48 patients noted significant (>50%) improvement of their symptoms and have been ingesting hot water or other hot liquids regularly with their meals. We conclude that hot water accelerates esophageal clearance, decreases the amplitude and duration of esophageal body contractions, and improves symptoms in patients with esophageal motility disorders. Because of its safety and simplicity, it may have an important role in the management of these chronic conditions.

Evaluation of suspected recurrent papillary thyroid carcinoma with [18F]fluorodeoxyglucose positron emission tomography.

We evaluated 10 patients with suspected recurrent papillary thyroid cancer using [18F]fluorodeoxyglucose positron emission tomography (FDG PET). Prior therapy included total (n = 8) or subtotal (n = 2) thyroidectomy, radiation therapy (n = 2) and radioiodine ablation (n = 2). All patients had an 131I scan and one or more of the following imaging studies: 99Tcm-sestamibi scan. 111In-octreotide scan, sonography (US), computed tomography (CT) and magnetic resonance imaging (MRI). Both the PET and 131I scans were negative in four patients. The PET and 131I scan results were discordant in six patients. Of the six discordant cases, five had true-positive PET scans and false-negative 131I studies. Three of these patients underwent neck lymph node dissection that showed positive histology for metastatic papillary carcinoma. Another patient had fine-needle aspiration (FNA) of a parapharyngeal mass that was also positive for papillary carcinoma. One patient was treated with radiation to the thyroid surgical bed based on an elevated serum thyroglobulin and a positive PET finding. Tumour response with a decrease in the size of the lesion was documented by a follow-up MRI scan. The remaining patient had a presumed false-positive PET scan, since a difficult hypocellular FNA of a small palpable lymph node was negative for tumour. We conclude that FDG PET is useful in the evaluation of patients with suspected recurrent papillary thyroid cancer when the 131I scan is negative.

Fast acquisition of myocardial SPECT images with Tc-99m sestamibi for the diagnosis of coronary artery disease.

BACKGROUND: Shortening the acquisition time for myocardial single-photon emission computed tomographic (SPECT) imaging increases patient comfort and laboratory throughput. The purpose of this study was to compare the diagnostic accuracy for coronary artery disease detection of myocardial SPECT images acquired in 5 to 10 minutes versus 25 minutes using Tc-99m methoxyisobutylisonitrile (Tc-99m sestamibi) and a single-head gamma camera. METHODS AND RESULTS: Forty-one subjects had a standard 1-day rest/stress Tc-99m sestamibi myocardial SPECT study. Two sets of rest and stress images were acquired on the same day for each subject. One set of images was acquired with a 5- to 10-minute fast acquisition protocol; the second set of images was acquired with a 25-minute standard protocol. The accuracies of the fast and standard protocols for identifying individuals with and without coronary artery disease were equivalent. Accuracy was 76% for the fast protocol and 73% for the standard protocol in individuals with at least one coronary stenosis > or = 70%. The accuracies of the two protocols for identifying individual coronary arteries with stenoses > or = 70% also were equivalent. Accuracy was 77% for the fast protocol and 74% for the standard protocol. CONCLUSIONS: SPECT myocardial images may be acquired in as little as 5 to 10 minutes using Tc-99m sestamibi and a 1-day rest/stress protocol. Accuracy is equivalent to that attained in studies with longer imaging times.

Effect of radionuclide renograms on treatment of patients with spinal cord injuries.

OBJECTIVE: Urinary tract problems stemming from neurologic dysfunction are a major cause of morbidity in patients with spinal cord injury. Radionuclide renograms have been used to monitor renal function in these patients. However, the effect of renographic results on the treatment of patients has not been studied. A retrospective study was done to determine the effect of radionuclide renography on the diagnostic evaluation and therapeutic treatment of patients with spinal cord injury. MATERIALS AND METHODS: The records of 199 patients with spinal cord injuries were reviewed. A decline in effective renal plasma flow of 20% or more, a low effective renal plasma flow for age, and abnormal tracer time-activity curves were correlated with diagnostic procedures and therapeutic interventions. Diagnostic procedures included renal sonography, CT, excretory urography, and urodynamics. Therapeutic interventions included changes in medication, changes in bladder management, and surgery. RESULTS: Patients with abnormal findings on renograms underwent more diagnostic procedures and therapeutic interventions. A significant correlation was found between abnormal tracer time-activity curves and use of excretory urography. A decline in effective renal plasma flow was the best predictor of therapeutic intervention. CONCLUSION: Radionuclide renograms influence the diagnostic evaluation and therapeutic treatment of patients with spinal cord injury.

False-negative fluorine-18-FDG PET in metastatic carcinoid.

Carcinoid tumors have high numbers of somatostatin receptors that allow scintigraphic imaging with the radiolabeled somatostatin analog octreotide. Experience, however, with PET using 2-[18F]fluoro-2-deoxy-D-glucose (18FDG) in carcinoid is very limited. In two prior studies which investigated the utility of 18FDG-PET in cancer detection, three patients with small, solitary, indolent carcinoid tumors had false-negative results. We report a case where 18FDG-PET imaging was false-negative in a patient with known metastatic carcinoid and a positive octreotide scan.

Characterization of pulmonary nodules and mediastinal staging of bronchogenic carcinoma with F-18 fluorodeoxyglucose positron emission tomography.

OBJECTIVE: To evaluate F-18 fluorodeoxyglucose positron emission tomography (PET) in terms of its sensitivity and specificity in diagnosing malignant pulmonary nodules and staging bronchogenic carcinoma. METHODS: A retrospective review of any patient that presented to the VA Palo Alto Health Care System with a pulmonary nodule between 9/94 and 3/96 revealed 49 patients (four female, 45 male) age 37-85 (mean 63) with 54 pulmonary nodules who had: chest CT scan, PET scan; and tissue characterization of the nodule. Characterization of each nodule was achieved by histopathologic (N = 44) or cytopathologic (N = 10) analysis. Of the 49 patients, 18 had bronchogenic carcinoma which was adequately staged. Mediastinal PET and CT findings in these 18 patients were compared with the surgical pathology results. N2 disease was defined as mediastinal lymph node involvement by the American Thoracic Society's classification system. Mediastinal lymph nodes were interpreted as positive by CT if they were larger that 1.0 cm in the short-axis diameter. RESULTS: Sensitivity and specificity for the diagnosis of malignant pulmonary nodules using PET was 93 and 70%, respectively. All nodules (N = 3) that were falsely positive by PET scan were infectious in origin. All nodules (N = 4) that were falsely negative by PET were technically limited studies (outdated scanner, no attenuation correction, hyperglycemia) except for one case of metastatic adenocarcinoma. The sensitivity and specificity of PET in diagnosing N2 disease was 67 and 100%, compared with 56% and 100% for CT scan (not statistically significant). However, one more patient with N2 disease was correctly diagnosed by PET than by CT scan. CONCLUSION: PET is a valuable tool in the diagnosis and management of pulmonary nodules and may more accurately stage patients with bronchogenic carcinoma than CT scanning alone.