Lee P. Adler

Positron Emission Tomography for Evaluating Para-aortic Nodal Metastasis in Locally Advanced Cervical Cancer Before Surgical Staging: A Surgicopathologic Study

PURPOSE Positron emission tomographic (PET) scanning provides a novel means of imaging malignancies. This prospective study was undertaken to evaluate PET scanning in detecting para-aortic nodal metastasis in patients with locally advanced cervical carcinoma and no evidence of extrapelvic disease before planned surgical staging lymphadenectomy. MATERIALS AND METHODS After 20 mCi of 2-[18F]fluoro-2-deoxy-D-glucose (FDG) were administered intravenously, the abdomen and pelvis were scanned. Continuous bladder irrigation was used to reduce artifact. Patients were classified by the presence or absence of FDG uptake in the primary tumor and in pelvic or para-aortic nodes. Para-aortic node metastases were classified as present or absent according to a standardized staging procedure. Pelvic node metastases were similarly classified in a subset of patients who underwent pelvic node resection. RESULTS Thirty-two patients with stage IIB (n = 6), IIIB (n = 24), and IVA (n = 2) tumors were studied. Fluorodeoxyglucose was taken up by 91% of the cervical tumors. Six of eight patients with positive para-aortic node metastasis had PET scan evidence of para-aortic nodal metastasis. One of the two false-negatives had only one microscopic focus of metastatic cancer. In the para-aortic nodes, PET scanning had a sensitivity of 75%, a specificity of 92%, a positive predictive value of 75%, and a negative predictive value of 92%. Fluorodeoxyglucose para-aortic nodal uptake conferred a relative risk of 9.0 (95% confidence interval, 2.3 to 36.0) for para-aortic nodal metastasis. All 10 of 17 patients with metastasis were predicted by PET scanning (P < .001); five of these patients had abnormalities on computed tomographic scans. CONCLUSION Cervical cancers have a high avidity for FDG. The use of PET-FDG scanning accurately predicts both the presence and absence of pelvic and para-aortic nodal metastatic disease.

Performance Characteristics of Amyloid PET with Florbetapir F 18 in Patients with Alzheimer's Disease and Cognitively Normal Subjects

The objectives of this study were to examine the effective dose range and the test–retest reliability of florbetapir F 18 using, first, visual assessment by independent raters masked to clinical information and, second, semiautomated quantitative measures of cortical target area to cerebellum standardized uptake value ratios (SUVr) as primary outcome measures. Visual ratings of PET image quality and tracer retention or β-amyloid (Aβ) binding expressed as SUVrs were compared after intravenous administration of either 111 MBq (3 mCi) or 370 MBq (10 mCi) of florbetapir F 18 in patients with Alzheimers disease (AD) (n = 9) and younger healthy controls (YHCs) (n = 11). In a separate set of subjects (AD, n = 10; YHCs, n = 10), test–retest reliability was evaluated by comparing intrasubject visual read ratings and SUVrs for 2 PET images acquired within 4 wk of each other. Results: There were no meaningful differences between the 111-MBq (3-mCi) and 370-MBq (10-mCi) dose in the visual rating or SUVr. The difference in the visual quality across 111 and 370 MBq showed a trend toward lower image quality, but no statistical significance was achieved (t test; t1 = −1.617, P = 0.12) in this relatively small sample of subjects. At both dose levels, visual ratings of amyloid burden identified 100% of AD subjects as Aβ-positive and 100% of YHCs as Aβ-negative. Mean intrasubject test–retest variability for cortical average SUVrs with the cerebellum as a reference over the 50- to 70-min period was 2.4% ± 1.41% for AD subjects and 1.5% ± 0.84% for controls. The overall SUVr test–retest correlation coefficient was 0.99. The overall κ-statistic for test–retest agreement for Aβ classification of the masked reads was 0.89 (95% confidence interval, 0.69–1.0). Conclusion: Florbetapir F 18 appears to have a wide effective dose range and a high test–retest reliability for both quantitative (SUVr) values and visual assessment of the ligand. These imaging performance properties provide important technical information on the use of florbetapir F 18 and PET to detect cerebral amyloid aggregates.

Positron emission tomography and breast masses: Comparison with clinical, mammographic, and pathological findings

AbstractBackground: Positron emission tomography (PET) is a means of imaging tissue based upon its metabolic activity. Initial studies in the field of oncology suggest that PET may be useful for diagnosis, staging, and treatment of various tumors. Methods: Twenty-eight patients with 37 breast lesions were studied with PET using [fluorine-18] 2-deoxy-2-fluoro-D-glucose (FDG) to assess which clinico-pathological characteristics relate to FDG accumulation by the primary tumor. Results: PET-FDG was found to successfully discriminate malignant from benign breast lesions (p=0.02) and identify axillary lymph node metastases. FDG uptake by the primary tumor was found to be independent of age, menopausal status, race, tumor size, laterality, histologic differentiation, ploidy, DNA index, estrogen or progesterone receptor value, pathologic stage, and serum glucose. Higher tumor nuclear grade and S-phase were associated with more FDG accumulation by the primary tumor compared with normal breast tissue. PET-FDG correctly identified five malignant lesions that were indeter-minant for cancer both on clinical breast examination and mammography and identified one occult cancer that was neither palpable nor apparent mammographically. PET-FDG correctly identified clinical occult axillary metastatic cancer in five patients. Conclusions: This study shows that PET-FDG imaging can distinguish malignant from benign breast lesions among a diverse group of patients and suggests that PET-FDG may not only allow for preoperative staging of patients but also provide information about prognosis. This study provides impetus for continued research into PET-FDG imaging of breast lesions, which could have a major impact on the treatment of breast cancer.

Elimination of artifactual accumulation of FDG in PET imaging of colorectal cancer

BACKGROUND Positron emission tomography (PET) with fluorine-18 labeled deoxyglucose (FDG) can detect tumor recurrences in surgical patients that are otherwise difficult to assess by CT, as well as distant metastases and small malignant nodes that are not identified by other imaging modalities. However, the evaluation of such malignancy is complicated by urinary and colonic concentrations of FDG. Methods and examples of the elimination of artifactual accumulation of FDG in PET imaging of the abdomen and pelvis are presented. METHODS Elimination of artifactual accumulation requires patient preparation that begins with cleansing of the colon using an isosmotic solution taken the evening prior to examination. Approximately 500 MBq of F-18 FDG is intravenously administered upon arrival at the PET facility and then the patient is hydrated. After administration of furosemide, a Foley catheter with a drainage bag is placed and the patient is then scanned. Just prior to scanning over the pelvis, normal saline is delivered retrogradely into the urinary bladder. At the end of scanning, the patient voids and repeated pelvic images are obtained. RESULTS These routines yield a clean scanning field. Lesions that will generally be missed because they are obscured by FDG accumulations along the colon or in the kidneys, ureters, or bladder are better visualized and identified with greater confidence. Artifacts that lead to misinterpretation also are reduced. CONCLUSION Elimination of artifactual accumulation of FDG in the colon and urinary system is essential if primary cancer, associated adenopathy, or subtle recurrences are to be evaluated in FDG PET imaging of the abdomen and pelvis.

Measurement of Human Cerebral Blood Flow with [15O]Butanol and Positron Emission Tomography

Although H215O is widely used for CBF measurement by positron tomography, it underestimates CBF, especially at elevated flow rates. Several tracers, including butanol, overcome this problem, but the short half-life of 15O provides advantages that cause water to remain the tracer of choice. We report the first use and evaluation of 15O–labeled butanol for CBF measurement. Flow measurements made in a similar fashion with water and butanol at 10-min intervals were compared in normal volunteers under resting and hypercapnic conditions. Regional analysis showed good agreement between the tracers at low flows, and significant underestimation of flow by water relative to butanol in regions of elevated flow. The observed relationship between the tracers and the curve-fitted permeability-surface area product for water (133 ml · 100 g−1 · min−1) follow the known relationship between water and true flow. These observations indicate that [15O]-butanol provided accurate measurements of human regional CBF under conditions of elevated perfusion. We conclude that butanol is a convenient and accurate method for routine CBF determination by positron emission tomography.

Grading liposarcomas with PET using [18F]FDG

Five patients with liposarcomas of the thigh were studied using positron emission tomography (PET) with [18F]2-deoxy-2-fluoroglucose (FDG). There were three low-grade tumors (all National Cancer Institute Grade 1 myxoid liposarcomas) and two high-grade tumors (both pleomorphic liposarcomas, Grades 2 and 3). The low-grade liposarcomas were easily identified with an average dose uptake ratio (DUR) of 1.38 +/- 0.045 (mean +/- SD). The high-grade lesions were more avid for FDG with a mean DUR of 2.45 +/- 0.24. There was a significant difference (p = 0.004) in the DUR for the two groups and the histological grade of malignancy was highly correlated with the DUR for FDG (Rho = 0.89). These findings suggest that FDG-PET may be useful for distinguishing between low-grade and high-grade liposarcomas.

How to differentiate benign versus malignant cardiac and paracardiac 18F FDG uptake at oncologic PET/CT.

Patients undergoing 2-[fluorine 18]fluoro-2-deoxy-d-glucose (FDG) whole-body oncologic positron emission tomography (PET)/computed tomography (CT) are studied while fasting. Cardiac FDG uptake in fasted patients has been widely reported as variable. It is important to understand the normal patterns of cardiac FDG activity that can be seen in oncologic FDG PET/CT studies. These include focal and regional patterns of increased FDG myocardial activity. Focal activity can be observed in papillary muscles, the atria, the base, and the distal anteroapical region of the left ventricle. Regional increased cardiac FDG activity may be diffuse or localized in the posterolateral wall or the base of the left ventricle. Abnormal patterns of cardiac FDG activity not related to malignancy include those associated with lipomatous hypertrophy of the interatrial septum, epicardial and pericardial fat, increased atrial activity associated with atrial fibrillation or a prominent crista terminalis, cardiac sarcoidosis, endocarditis, myocarditis, and pericarditis. Knowledge of these patterns of cardiac FDG activity is important to be able to recognize malignant disease involving the paracardiac spaces, myocardium, and pericardium. With a better understanding of the range of normal and abnormal patterns of cardiac FDG activity, important benign and malignant diseases involving the heart and pericardium can be recognized and diagnosed.

Variable cardiac 18FDG patterns seen in oncologic positron emission tomography computed tomography: importance for differentiating normal physiology from cardiac and paracardiac disease.

Purpose Cardiac fluorine-18-fluorodeoxyglucose (18FDG) uptake is known to be variable in fasting oncologic positron emission tomography computed tomography studies. Increased posterolateral and basal 18FDG activity have been reported with the basal pattern ascribed to radiation injury. The purpose of this study was to investigate the spectrum of normal cardiac 18FDG findings seen in oncologic patients. Materials and Methods Men <35 years of age and women <45 years of age seen over a 3-year period were included. A visual assessment of 18FDG cardiac activity was performed using a 12-segment model of the heart by 2 observers. Focal papillary muscle activity was not included in the analysis. Results Of 65 patients who met the entry criteria, increased 18FDG activity was observed in the base of the heart in 37 (57%) patients. This was most common in the lateral-basal wall in 35 (54%) patients, followed by posterior-basal wall in 21 (32%) patients, anterior-basal wall in 10 (15%) patients, and basal-septum in 10 (15%) patients. Suppression of total cardiac activity was present in only 6 (9%) patients in spite of adequate fasting. Diffuse cardiac activity was seen in 9 (14%) patients. The previously reported increased posterolateral pattern was present in only 9 (14%) patients. Conclusion This study confirms variable fasting 18FDG cardiac activity with a predominant basal pattern not associated with radiation injury. Knowledge of these patterns is important for recognition of possible underlying cardiac ischemia, tumor, or other inflammatory conditions encountered during interpretation of oncologic positron emission tomography computed tomography studies.

PET imaging in soft tissue sarcomas

Positron emission tomography (PET) was conceived in the early years of nuclear medicine; however, until about 1980 the technology was insufficiently developed to allow its routine application. Furthermore, the high cost of construction and operation of a PET facility delayed its use in the clinical arena and also limited the number of sites available for its development. Today, only 15 years later, PET instrumentation is very sophisticated, costs are decreasing relative to other clinical studies, and clinical PET procedures are proliferating rapidly. In the last few years the application of PET to oncology has proven to be very successful, and there is now a significant literature on PET imaging of many different cancers [1–18].

Review of some common artifacts in nuclear medicine

In nuclear medicine, artifacts may simulate a pathologic process; their recognition is therefore necessary to avoid misdiagnosis. Artifacts may be divided into three groups: 1) camera dependent artifacts; 2) radiopharmaceutical dependent artifacts; and 3) patient-related artifacts. The authors present a variety of artifacts and discusses their possible prevention.