George M. Segall

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.

Effects of anger on left ventricular ejection fraction in coronary artery disease

This study examined the comparative potency of several psychological stressors and exercise in eliciting myocardial ischemia as measured by left ventricular (LV) ejection fraction (EF) changes using radionuclide ventriculography. Twenty-seven subjects underwent both exercise (bicycle) and psychological stressors (mental arithmetic, recall of an incident that elicited anger, giving a short speech defending oneself against a charge of shoplifting) during which EF, blood pressure, heart rate and ST segment were measured. Eighteen subjects had 1-vessel coronary artery disease (CAD), defined by greater than 50% diameter stenosis in 1 artery as assessed by arteriography. Nine subjects served as healthy control subjects. Anger recall reduced EF more than exercise and the other psychological stressors (overall F [3.51] = 2.87, p = .05). Respective changes in EF for the CAD patients were -5% during anger recall, +2% during exercise, 0% during mental arithmetic and 0% during the speech stressor. More patients with CAD had significant reduction in EF (greater than or equal to 7%) during anger (7 of 18) than during exercise (4 of 18). The difference in EF change between patients with CAD and healthy control subjects was significant for both anger (t25 = 2.23, p = 0.04) and exercise (t25 = 2.63, p = 0.01) stressors. In this group of patients with CAD, anger appeared to be a particularly potent psychological stressor.

SNM Practice Guideline for Sodium 18F-Fluoride PET/CT Bone Scans 1.0

PREAMBLE The Society of Nuclear Medicine (SNM) is an international scientific and professional organization founded in 1954 to promote the science, technology, and practical application of nuclear medicine. Its 16,000 members are physicians, technologists, and scientists specializing in the research and practice of nuclear medicine. In addition to publishing journals, newsletters, and books, the SNM also sponsors international meetings and workshops designed to increase the competencies of nuclear medicine practitioners and to promote new advances in the science of nuclear medicine. The SNM will periodically define new Practice Guidelines for nuclear medicine practice to help advance the science of nuclear medicine and to improve the quality of service to patients throughout the United States. Existing Practice Guidelines will be reviewed for revision or renewal, as appropriate, on their fifth anniversary or sooner, if indicated. Each Practice Guideline, representing a policy statement by the SNM, has undergone a thorough consensus process in which it has been subjected to extensive review, requiring the approval of the Committee on SNM Guidelines, Health Policy and Practice Commission, and SNM Board of Directors. The Practice Guidelines recognize that the safe and effective use of diagnostic nuclear medicine imaging requires specific training, skills, and techniques, as described in each document. Reproduction or modification of the published Practice Guidelines by those entities not providing these services is not authorized. These Practice Guidelines are an educational tool designed to assist practitioners in providing appropriate care for patients. They are not inflexible rules or requirements of practice and are not intended, nor should they be used, to establish a legal standard of care. For these reasons and those set forth below, the SNM cautions against the use of these Practice Guidelines in litigation in which the clinical decisions of a practitioner are called into question. The ultimate judgment regarding the propriety of any specific procedure or course of action must be made by the physician or medical physicist in light of all the circumstances presented. Thus, an approach that differs from the Practice Guidelines, standing alone, does not necessarily imply that the approach was below the standard of care. To the contrary, a conscientious practitioner may responsibly adopt a course of action different from that set forth in the Practice Guidelines when, in the reasonable judgment of the practitioner, such course of action is indicated by the condition of the patient, limitations of available resources, or advances in knowledge or technology subsequent to publication of the Practice Guidelines. The practice of medicine involves not only the science, but also the art, of preventing, diagnosing, alleviating, and treating disease. The variety and complexity of human conditions make it impossible to always reach the most appropriate diagnosis or to predict with certainty a particular response to treatment. Therefore, it should be recognized that adherence to these Practice Guidelines will not ensure an accurate diagnosis or a successful outcome. All that should be expected is that the practitioner will follow a reasonable course of action based on current knowledge, available resources, and the needs of the patient to deliver effective and safe medical care. The sole purpose of these Practice Guidelines is to assist practitioners in achieving this objective.

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. Key Words: Head and neck cancer, squamous cell carcinoma, positron emission tomography, unknown primary cancer, cervical lymph node metastasis.

A Comparison of the Diagnostic Accuracy of 18F-FDG PET and CT in the Characterization of Solitary Pulmonary Nodules

CT and PET are widely used to characterize solitary pulmonary nodules (SPNs). However, most CT accuracy studies have been performed with outdated technology and methods, and previous PET studies have been limited by small sample sizes and incomplete masking. Our objective was to compare CT and PET accuracy in veterans with SPN. Methods: Between January 1999 and June 2001, we recruited 532 participants with SPNs newly diagnosed on radiography and untreated. The SPNs were 7–30 mm. All patients underwent 18F-FDG PET and CT. A masked panel of 3 PET and 3 CT experts rated the studies on a 5-point scale. SPN tissue diagnosis or 2-y follow-up established the final diagnosis. Results: A definitive diagnosis was established for 344 participants. The prevalence of malignancy was 53%. The average size was 16 mm. Likelihood ratios (LRs) for PET and CT results for combined ratings of either definitely benign (33% and 9% of patients, respectively) or probably benign (27% and 12%) were 0.10 and 0.11, respectively. LRs for PET and CT results for combined ratings of indeterminate (1% and 25%), probably malignant (21% and 39%), or definitely malignant (35% and 15%) were 5.18 and 1.61, respectively. Area under the receiver operating characteristic curve was 0.93 (95% confidence interval, 0.90–0.95) for PET and 0.82 (95% confidence interval, 0.77–0.86) for CT (P < 0.0001 for the difference). PET inter- and intraobserver reliability was superior to CT. Conclusion: Definitely and probably benign results on PET and CT strongly predict benign SPN. However, such results were 3 times more common with PET. Definitely malignant results on PET were much more predictive of malignancy than were these results on CT. A malignant final diagnosis was approximately 10 times more likely than a benign final diagnosis in participants with PET results rated definitely malignant.

Positron emission tomography is superior to computed tomography for metastatic detection in melanoma patients.

BackgroundWhole-body positron emission tomography (PET) provides diagnostic information not currently available with traditional imaging and may improve the accuracy of staging melanoma patients.MethodsA retrospective cohort review was performed of 104 patients with primary or recurrent melanoma who underwent PET to determine sensitivity/specificity for metastatic detection compared with body computed tomography (CT). One hundred fifty-seven PET and 70 CT scans were analyzed, with a median patient follow-up of 24 months. Metastases were confirmed with positive histology (87.5%) or documented disease progression (12.5%). Fifty-three patients prospectively underwent consecutive studies within a mean 3-week interval for direct comparative analysis.ResultsPET demonstrated 84% sensitivity (95% confidence interval [CI], .78 to .89) and 97% specificity (95% CI, .91 to .99), whereas CT showed 58% sensitivity (95% CI, .49 to .66) and 70% specificity (95% CI, .51 to .84). Exclusion of areas not evaluated on CT (head, neck/supraclavicular, extremities) increased CT sensitivity to 69% (95% CI, .59 to .77). Sixty-six consecutive PET and CT scans were performed with 81% and 57% of metastases detected, respectively.ConclusionsPET is more sensitive and specific than CT for detection of melanoma metastasis and should be considered the primary staging study for 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. PET is superior to CT even when sites not routinely evaluated by CT are excluded from comparative analysis.

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 radio-iodine 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.

Evaluation of Fluorodeoxyglucose Positron Emission Tomography Imaging in Metastatic Transitional Cell Carcinoma with and without Prior Chemotherapy

Introduction: This study was designed to determine the value of fluorodeoxyglucose (FDG) positron emission tomography (PET) in the evaluation of metastatic transitional cell carcinoma (TCC). Methods: Fifty-eight FDG PET scans were performed on 46 consecutive patients with TCC. Results were correlated with radiologic, pathologic, and histologic findings in these patients and the sensitivity of PET for detecting malignancy in untreated TCC patients (n = 48) was compared to the sensitivity in patients who had undergone prior chemotherapy (n = 10). Results: Of 48 scans in patients who had no prior systemic chemotherapy, 10 had increased uptake in proven metastatic TCC lesions and 3 PET studies failed to reveal metastatic TCC (sensitivity 76.9%). In patients free of metastatic disease, 33 revealed no abnormal uptake and 1 study revealed a suspicious area in a patient free of metastases (specificity = 97.1%). However, in 10 patients imaged after receiving chemotherapy, the sensitivity fell to 50% for the detection of histologically confirmed residual/recurrent tumor by PET. Conclusions: FDG PET detects increased metabolic activity. After chemotherapy, viable cancer cells may still be present but with a diminished metabolic rate. As a result, PET imaging is often useful in the evaluation of untreated metastatic TCC metastasis but should be interpreted with caution in patients who have received prior chemotherapy.

Assessment of myocardial viability by positron emission tomography.

Accurate assessment of myocardial viability is critical for identifying patients likely to benefit from coronary revascularization. Positron emission tomography (PET) has several advantages over single photon emission computed tomography (SPECT), including higher sensitivity and specificity, as well as the ability to measure myocardial blood flow and myocardial metabolism in absolute terms, which is important in understanding the pathophysiology of ischemic cardiomyopathy. The most commonly used PET tracer is [18F]2-fluoro-2deoxy-D-glucose (FDG). The dependence of ischemic myocardium on glucose metabolism makes FDG an ideal tracer in this setting. Studies have shown positive and negative predictive values for the detection of viable myocardium in the range of 48-94%, and 73-96%, respectively. FDG is superior to SPECT using thallium or technetium myocardial perfusion agents, as well as echocardiography with dobutamine infusion. FDG PET also provides important prognostic information. Patients with evidence of myocardial viability by FDG PET have fewer cardiac events and survive longer if revascularized compared to patients who are treated medically. This article will review myocardial metabolism, PET procedures and interpretive criteria, as well as problems and limitations. Data from the literature regarding diagnostic and prognostic information will also be summarized.

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.