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At least 19 recordsLinked to original sources
PubMed2001

Comparison of (18)F-FDG, (131)I-Na, and (201)Tl in diagnosis of recurrent or metastatic thyroid carcinoma.

UNLABELLED: There are several reports about the usefulness of (18)F-FDG PET in thyroid cancer. However, few studies have compared FDG PET with (131)I and (201)Tl scintigraphy. The aim of this study was to evaluate the clinical significance of whole-body FDG PET in differentiated thyroid cancer and to compare the results with those obtained from (131)I and (201)Tl scintigraphy. METHODS: Whole-body FDG PET was performed on 32 patients (10 men, 22 women; age range, 30-77 y; mean age, 54 y) with differentiated thyroid cancer (5 cases of follicular cancer and 27 of papillary cancer) after total thyroidectomy. An overall clinical evaluation was performed, including cytology, thyroglobulin level, sonography, MRI, and CT, to allow a comparison with functional imaging results for each patient. Metastatic regions were divided into five areas: neck, lung, mediastinum, bone, and other. Multiple lesions in one area were defined as one lesion. The tumor-to-background ratio (TBR) was measured for the lesions that were positive for both (201)Tl uptake and FDG PET uptake. RESULTS: The number of lesions totaled 47. Forty-one (87%) were detected by all scintigraphic methods. FDG uptake was concordant with (131)I uptake in only 18 lesions (38%). FDG uptake was concordant with (201)Tl uptake in 44 lesions (94%). Only one lesion was negative for FDG uptake and positive for (201)Tl uptake, and two lesions were positive for FDG uptake and negative for (201)Tl uptake. A significant correlation was seen between the TBR of (201)Tl and that of FDG (r = 0.69; P<0.05). CONCLUSION: These data indicate that for detecting metastatic lesions, FDG PET and (131)I scintigraphy may provide complementary information, whereas FDG PET may provide results similar to those of (201)Tl scintigraphy. Thus, the combination of (131)I scintigraphy and FDG PET (or (201)Tl scintigraphy) is the method of choice for detecting metastatic thyroid cancer after total thyroidectomy.

Adenocarcinoma, Follicular↗
PubMed2000

Prediction of functional recovery after revascularization in coronary artery disease using (18)F-FDG and (123)I-BMIPP SPECT.

STUDY OBJECTIVES: Clinical studies comparing fatty acid and glucose metabolism in relation to functional recovery of ischemic myocardium after coronary revascularization are scarce. This study evaluated the recovery of regional and global left ventricular function after coronary revascularization in relation to uptake patterns of beta-methyl-iodophenyl-pentadecanoic acid (BMIPP) and fluorodeoxyglucose (FDG) in patients with ischemic myocardial dysfunction. METHODS: Patients with ischemic regional wall motion abnormality underwent baseline viability imaging with (18)F-FDG, (123)I-BMIPP, and (99m)Tc- methoxyisobutylisonitrile, and the regions with evidence for maintained tissue viability were revascularized. Mismatch of uptake score between two different single-photon emission CT (SPECT) images in the same myocardial region was graded as low or high mismatch. Regional and global left ventricular functional changes after revascularization were analyzed in relation to mismatch severity and difference of total uptake score in each SPECT image pair. A total of 33 vessels in 30 patients related to the asynergic regions were revascularized, and a total of 100 myocardial segments perfused by the revascularized vessels were analyzed. RESULTS: Segments showing high metabolic mismatch (FDG/BMIPP) had lowest regional wall motion score at baseline, representing the most severely impaired ischemic myocardium, and had highest improvement in regional wall motion score after revascularization. Difference of total uptake score between FDG and BMIPP showed a significant positive correlation with difference of ejection fraction between pre- and postrevascularization (r = 0.774, p < 0.0001). CONCLUSIONS: Combined metabolic SPECT imaging with FDG and BMIPP has the potential to identify severely impaired ischemic myocardium leading to more efficient therapeutic management of patients with coronary artery disease.

Aged↗
PubMed2000

Persistent tumor 18F-FDG uptake after a few cycles of polychemotherapy is predictive of treatment failure in non-Hodgkin's lymphoma.

BACKGROUND AND OBJECTIVE: Early recognition of the ineffectiveness of chemotherapy could result in lower cumulative drug toxicity and tumor burden at the start of salvage therapy, which might improve clinical outcome. Therefore, we studied the value of (18)F-FDG PET for early evaluation of response in patients with non-Hodgkin's lymphoma (NHL). DESIGN AND METHODS: We studied 28 patients by (18)F-FDG PET after a median of 3 cycles of polychemotherapy. The presence or absence of abnormal (18)F-FDG uptake was correlated to clinical outcome (median follow-up: 17.5 months, range 4-47 months). RESULTS: Five of 28 patients still had increased (18)F-FDG uptake in one or more sites previously shown to be involved by lymphoma at baseline evaluation. Only one of these five patients entered complete remission (CR), whereas among the 23 patients with negative (18)F-FDG PET studies, two died of toxicity during chemotherapy and all the others entered clinical CR (p<0.00001). All five patients with and 7/21 patients without residual abnormal (18)F-FDG uptake relapsed or reprogressed (positive predictive value for relapse: 100%, negative predictive value: 67%). By Kaplan-Meier analysis, progression-free survival (PFS) at 1 and 2 years was respectively 20+/-18% and 0% for (18)F-FDG PET positive patients and 81+/-9% and 62+/-12% for (18)F-FDG PET negative patients (p=0.0001). Overall survival (OS) at 1 and 2 years was respectively 20+/-18% and 0% for (18)F-FDG PET positive and 87+/-7% and 68+/-11% for (18)F-FDG PET negative patients (p<0.0001). INTERPRETATION AND CONCLUSIONS: Persistent tumoral (18)F-FDG uptake after a few cycles of polychemotherapy is predictive of CR, PFS and OS in NHL. Further studies are warranted to determine whether (18)F-FDG PET has a predictive value independent from conventional prognostic factors. However, the sensitivity of qualitative (18)F-FDG PET imaging in identifying patients with a poor outcome was insufficient. Earlier evaluation after only one cycle of chemotherapy and quantitative analysis might increase the sensitivity of 18F-FDG PET is predicting treatment failure.

Adult↗
PubMed2001

Whole-body positron emission tomography using 18F-fluorodeoxyglucose compared to standard procedures for staging patients with Hodgkin's disease.

BACKGROUND AND OBJECTIVES: Accurate staging is essential in order to determine appropriate treatment in Hodgkin's disease (HD). (18)F-fluorodeoxyglucose positron emission tomography ((18)F-FDG PET) offers the advantage of metabolic imaging that is largely independent of morphologic criteria. In the present study we evaluated the role of (18)F-FDG PET compared to routine procedures for the staging of patients with HD. DESIGN AND METHODS: Thirty-three patients with HD underwent standard staging procedures (clinical examination, laboratory screening, chest X-ray, computed tomography (CT) of the chest and abdomen and bilateral bone marrow biopsies) and a whole-body (18)F-FDG PET study. In clinical examination, an isolated lymph node > 1 cm or multiple lymph nodes > or = 1 cm in size were considered abnormal. Positive findings at both clinical examination or CT and (18)F-FDG PET were regarded as actual locations of disease. Negative findings with both methods were regarded as true negative (no involvement by HD). In cases of discrepancy, response to treatment and follow-up data were used to assess the overall accuracy of the patient's original evaluation. RESULTS: Completely concordant results in lymph node staging were observed in 20 patients. The two staging procedures indicated complementary information in 1 patient. Conventional staging indicated more pathologic lymph node areas in 6 patients (at least 1 false positive). (18)F-FDG PET showed more sites in 6 patients. The sensitivity of (18)F-FDG PET in detecting all known pathologic lymph nodes was 83% for peripheral lymph nodes, 91% for thoracic lymph nodes and 75% for abdominal and pelvic lymph nodes. Conventional staging procedures and (18)F-FDG PET indicated the same tumor stage in 26 patients. Based on (18)F-FDG PET, downstaging was suggested in 4 patients, including a biopsy-proven case. However in 1 of these cases this was incorrect. (18)F-FDG PET suggested upstaging in 3 patients. Based on conventional staging or (18)F-FDG PET the same treatment strategy was defined in 32 patients. In one patient (18)F-FDG PET downstaged disease extension (stage IIIA-->IIA) that would have suggested radiotherapy as a possible treatment option. INTERPRETATION AND CONCLUSIONS: (18)F-FDG PET provides an easy and efficient whole-body method for the evaluation of patients with HD. (18)F-FDG PET never missed tumor masses >1 cm. (18)F-FDG PET detected additional sites of disease not seen by conventional procedures and identified absence of disease in some sites suspected to be involved. However, in our patients this did not translate into changes in treatment strategy.

Adolescent↗
PubMed1999

Positron emission tomography of esophageal carcinoma using (11)C-choline and (18)F-fluorodeoxyglucose: a novel method of preoperative lymph node staging.

BACKGROUND: Accurate preoperative staging is an important but difficult problem in determining therapy for patients with esophageal carcinoma. Positron emission tomography (PET) is used with [methyl-(11)C]choline ((11)C-choline) and 2-[(18)F]fluoro-2-deoxy-D-glucose ((18)F-FDG) to detect a variety of malignancies. The authors used PET with both of these agents to detect lymph node metastases in patients with esophageal carcinoma. METHODS: Lymph node metastases in 33 patients with biopsy-proven esophageal carcinoma (16 patients with tumors classified as T1 and 17 patients with tumors classified as T2-4) was examined by PET using (11)C-choline and (18)F-FDG, and the accuracy of the results was correlated with pathology findings after surgery. RESULTS: (11)C-choline PET was more effective than (18)F-FDG PET and computed tomography (CT) in detecting very small metastases localized in the mediastinum. It was ineffective, however, in detecting metastases localized in the upper abdomen, because of the normal uptake of (11)C-choline in the liver. (18)F-FDG PET was superior to CT in detecting metastases in the mediastinum and the upper abdomen, whereas (11)C-choline PET was superior to (18)F-FDG PET in detecting metastases in the mediastinum. When (11)C-choline PET and (18)F-FDG PET were used in combination, they were very effective in evaluating the lymph node status in both the mediastinum and the upper abdomen, and detected 85% of the metastatic lymph nodes (n = 46). CONCLUSIONS: In this study, the combination of (11)C-choline PET and (18)F-FDG PET was very effective in evaluating the lymph node status of patients with esophageal carcinoma preoperatively.

Aged↗
PubMed2000

Ratio-images calculated from interictal positron emission tomography and single-photon emission computed tomography for quantification of the uncoupling of brain metabolism and perfusion in epilepsy.

PURPOSE: Image processing techniques were applied to interictal positron emission tomography (PET) and single-photon emission computed tomography (SPECT) brain images to aid in the localization of epileptogenic foci by calculating a functional image that represents the degree of coupling between perfusion and metabolism. Uncoupling of these two functions has been demonstrated to be a characteristic of epileptogenic tissue in temporal lobe epilepsy and has the potential to serve as a diagnostic measure for localization in other areas as well. METHODS: Interictal PET ((18)F-FDG) and interictal SPECT ((99m)Tc-HMPAO) scans were acquired from 11 epilepsy patients. The metabolism and perfusion images were three-dimensionally spatially registered, and a functional ratio-image was computed. These functional maps are overlaid onto a three-dimensional rendering of the same patient's magnetic resonance imaging anatomy. RESULTS: In all patients, an average uniform perfusion-to-metabolism ratio showed approximately constant values throughout most of the whole brain. However, the epileptogenic area (confirmed on surgery) demonstrated an area of elevated perfusion/metabolism in the grey matter. CONCLUSIONS: Although hypometabolism in the PET image was observed in most of these patients, the calculation of a functional ratio-image demonstrated localized foci that in some cases could not be observed on the PET image alone. The ratio-image also yields a quantitative measure of the uncoupling phenomenon.

Adolescent↗
PubMed2001

Extending positron emission tomography scan utility to high-risk neuroblastoma: fluorine-18 fluorodeoxyglucose positron emission tomography as sole imaging modality in follow-up of patients.

PURPOSE: Although positron emission tomography (PET) with fluorine-18 fluorodeoxyglucose ((18)F-FDG) has a major impact on the treatment of adult cancer, the reported experience with extracranial tumors of childhood is limited. We describe a role for PET in patients with neuroblastoma (NB). PATIENTS AND METHODS: In 51 patients with high-risk NB, 92 PET scans were part of a staging evaluation that included iodine-123 or iodine-131 metaiodobenzylguanidine (MIBG) scan, bone scan, computed tomography (and/or magnetic resonance imaging), urine catecholamine measurements, and bone marrow (BM) examinations. The minimum number of tests sufficient to detect NB was determined. RESULTS: Of 40 patients who were not in complete remission, only 1 (2.5%) had NB that would have been missed had a staging evaluation been limited to PET and BM studies, and 13 (32.5%) had NB detected by PET but not by BM and urine tests. PET was equal or superior to MIBG scans for identifying NB in soft tissue and extracranial skeletal structures, for revealing small lesions, and for delineating the extent and localizing sites of disease. In 36 evaluations of 22 patients with NB in soft tissue, PET failed to identify only two long-standing MIBG-negative abdominal masses. PET and MIBG scans showed more skeletal lesions than bone scans, but the normally high physiologic brain uptake of FDG blocked PET visualization of cranial vault lesions. Similar to MIBG, FDG skeletal uptake was diffusely increased with extensive or progressing BM disease but faint or absent with minimal or nonprogressing BM disease. CONCLUSION: In the absence or after resolution of cranial vault lesions, and once the primary tumor is resected, PET and BM tests suffice for monitoring NB patients at high risk for progressive disease in soft tissue and bone/BM.

3-Iodobenzylguanidine↗
PubMed1999

[Reduction of radiation exposure in PET examinations by data acquisition in the 3D mode].

AIM: Modern volume PET systems offer the possibility to measure without the shadowing effect of interplane septa (2D mode) and thus to detect coincident events between detectors on distant rings (3D mode). It was the aim of the present paper to characterize the count rate behaviour of a latest-generation whole-body PET system in the 2D and 3D mode as well as to discuss the consequences for the radiation hygiene of PET examinations with 2-[F-18]-fluoro-2-deoxyglucose (18-F-FDG). METHODS: All experiments were performed with the PET system ECAT EXACT HR+. For 2D data acquisition, a collimator of thin tungsten septa was positioned in the field-of-view. The count rate behaviour of the scanner was evaluated in the 2D and 3D mode over a wide range of F-18 activity concentrations following the NEMA protocol. Moreover, PET images of the EEC whole-body phantom with different inserts were acquired in the 2D and 3D mode over a period of 15 min each. For the 3D measurement, the activity concentrations of the F-18 solution were only half of those used for the 2D measurement. RESULTS: For the circular NEMA phantom (phi = 19.4 cm, length = 19.0 cm), we observed an increase of the system sensitivity in the 3D mode by a factor of about 5 with respect to the 2D mode (27.7 vs. 5.7 cps/Bq/ml). The evaluation of the activity distributions of the EEC phantom reconstructed from the 3D data set revealed a superior image quality compared to the corresponding 2D images despite the fact that the activity concentrations were only half as high. CONCLUSIONS: By using the 3D data acquisition mode, it is possible to markedly reduce the amount of activity to be applied to the patient and nevertheless to improve image quality. In our experience, it is sufficient to administer an activity of 150-200 MBq for whole-body examinations with F-18-FDG, which results in an effective equivalent dose of 3 or 4 mSv, respectively.

Environmental Exposure↗
PubMed2001

Radiolabeled amino acids: basic aspects and clinical applications in oncology.

As the applications of metabolic imaging are expanding, radiolabeled amino acids may gain increased clinical interest. This review first describes the basic aspects of amino acid metabolism, then continues with basic aspects of radiolabeled amino acids, and finally describes clinical applications, with an emphasis on diagnostic value. A special focus is on (11)C-methionine, (11)C-tyrosine, and (123)I-iodomethyltyrosine, because these have been most used clinically, although their common affinity for the L-transport systems may limit generalization to other classes of amino acids. The theoretic and preclinical background of amino acid imaging is sound and supports clinical applications. The fact that amino acid imaging is less influenced by inflammation may be advantageous in comparison with (18)F-FDG PET imaging, although tumor specificity is not absolute. In brain tumor imaging, the use of radiolabeled amino acids is established, the diagnostic accuracy of amino acid imaging seems adequate, and the diagnostic value seems advantageous. The general feasibility of amino acid imaging in other tumor types has sufficiently been shown, but more research is required in larger patient series and in well-defined clinical settings.

Amino Acids↗
PubMed2001

Dynamic PET 18F-FDG studies in patients with primary and recurrent soft-tissue sarcomas: impact on diagnosis and correlation with grading.

UNLABELLED: The purpose of this study was to evaluate (18)F-FDG PET studies of primary and recurrent sarcomas for diagnosis and correlation with grading. METHODS: The evaluation included 56 patients, 43 with histologically proven malignancies and 13 with benign lesions. Seventeen patients were referred with suspicion on a primary tumor, and the remaining 39 were referred with suspicion on a recurrent tumor. The FDG studies were accomplished as a dynamic series for 60 min. The evaluation of the FDG kinetics was performed using the following parameters: standardized uptake value (SUV), global influx, computation of the transport constants K1-k4 with consideration of the distribution volume (VB) according to a two-tissue-compartment model, and fractal dimension based on the box-counting procedure (parameter for the inhomogeneity of the tumors). RESULTS: Visual evaluation revealed a sensitivity of 76.2%, a specificity of 42.9%, and an accuracy of 67.9%. The vascular fraction VB and the SUV were higher in malignant tumors compared with benign lesions (t test, P < 0.05). Although the FDG SUV helped to distinguish benign and malignant tumors, there was some overlap, which limited the diagnostic accuracy. The SUV and fractal dimension accounted for significant differences in six of the nine diagnostic pairs. Whereas grade (G) II and G III tumors were differentiated from lipomas on the basis of the fractal dimension and some other kinetic parameters, no differences were found between G I tumors and lipomas. On the basis of the discriminant analysis, the differentiation of soft-tissue tumors was best for the use of six parameters of the FDG kinetics (SUV, VB, K1, k3, influx, and fractal dimension). Eighty-four percent of G III tumors, 37.5% of G II tumors, 80% of G I tumors, 50% of lipomas, and 14.3% of scars could be classified correctly, whereas inflammatory lesions were misclassified. CONCLUSION: FDG PET should be used preferentially for monitoring patients with G III sarcomas. Visual analysis provides a low specificity. In contrast, the evaluation of the full FDG kinetics provides superior information, particularly for the discrimination of G I and G III tumors (positive predictive value, >80%).

Diagnosis, Differential↗
PubMed2001

Low-dose dobutamine electrocardiograph-gated myocardial SPECT for identifying viable myocardium: comparison with dobutamine stress echocardiography and PET.

UNLABELLED: The identification of severely dysfunctional but viable myocardium is of particular importance for the selection of patients with depressed left ventricular function who will benefit from coronary revascularization. Assessment of inotropic reserve with dobutamine has recently been used for this purpose. This study compared the accuracy of low-dose dobutamine stress gated myocardial SPECT (DS SPECT) with the accuracy of dobutamine stress echocardiography (DSE) and resting perfusion SPECT for the identification of viable myocardium in patients with previous myocardial infarction. METHODS: Resting and low-dose dobutamine (7.5 microg/kg/min) gated (99m)Tc-tetrofosmin SPECT and echocardiography and resting (18)F-FDG PET were prospectively studied in 23 patients with previous myocardial infarction and severely depressed regional function. Twenty-one of them were successfully studied with each technique. The left ventricular wall was divided into 14 segments to assess wall motion using a 5-point scale. PET viability was defined as FDG uptake >/= 50% of the maximum uptake in a region with normal wall motion. For DS SPECT and DSE studies, viable myocardium was defined as hypokinetic areas with > or = 1 point improvement in wall motion. For resting perfusion SPECT, viable myocardium was defined as hypokinetic areas with a relative uptake > or = 50% of the maximum uptake. RESULTS: Of a total of 294 segments, 55 had severe resting dyskinesis. Thirty-four segments were identified as viable on FDG PET, and 21 segments were identified as nonviable. Eleven segments were inadequately visualized with DSE, including 5 segments in the apex. Sensitivities (78% vs. 76%) and specificities (94% vs. 100%) were similar for DSE and DS SPECT, with a concordance of 86% (kappa = 0.72). DS SPECT and perfusion SPECT did not significantly differ with respect to sensitivities (76% vs. 85%, respectively). However, specificity was significantly higher for DS SPECT than for perfusion SPECT (100% vs. 52%, respectively, P < 0.05). CONCLUSION: This study indicated that DS SPECT correlates well with DSE in the assessment of viability. In addition, gated SPECT can evaluate regional wall motion, even in areas inadequately assessed by echocardiography. DS SPECT may also provide additional information for identifying viable myocardium, which is often overestimated by routine perfusion scans.

Aged↗
PubMed2001

The diagnostic role of radionuclide imaging in evaluation of patients with nonhypersecreting adrenal masses.

UNLABELLED: The aim of this study was to evaluate the role of radionuclide imaging in the characterization of nonhypersecreting adrenal masses. METHODS: A total of 54 patients (19 men, 35 women; mean age, 50 +/- 16 y) with nonhypersecreting unilateral adrenal tumors that had been originally detected on CT or MRI underwent adrenal scintigraphy using different radiotracers. None of the patients showed specific symptoms of adrenal hypersecretion. Screening tests for excess cortical and medullary products showed normal adrenal hormone levels. Radionuclide studies (n = 73) included (131)I-norcholesterol (n = 24), (131)I-metaiodobenzylguanidine (MIBG) (n = 23), and (18)F-FDG PET (n = 26) scans. RESULTS: Histology after surgery (n = 31) or adrenal biopsy (n = 23) was obtained. Adrenal lesions were represented by 19 adenomas, 4 cysts, 1 myelolipoma, 1 neurinoma, 2 ganglioneuromas, 5 pheochromocytomas, 4 pseudotumors, 6 carcinomas, 2 sarcomas, and 10 metastases (size range, 1.5- to 5-cm diameter; mean, 4.9 +/- 3.1 cm). For norcholesterol imaging, diagnostic sensitivity, specificity, and accuracy were 100%, 71%, and 92%, respectively; the positive predictive value (PPV) of the norcholesterol scan to characterize an adrenal mass as an adenoma was 89%, whereas the corresponding negative predictive value (NPV) to rule out this type of tumor was 100%. For MIBG imaging, diagnostic sensitivity, specificity, and accuracy were 100%, 94%, and 96%, respectively; the PPV of the MIBG scan to characterize an adrenal mass as a medullary chromaffin tissue tumor was 83%, whereas the corresponding NPV to rule out this type of tumor was 100%. For FDG PET, diagnostic sensitivity, specificity, and accuracy were 100%, 100%, and 100%, respectively; the PPV of FDG PET to characterize an adrenal mass as a malignant tumor was 100%, whereas the corresponding NPV to rule it out was 100%. Furthermore, in 7 patients with malignant adrenal tumors, FDG whole-body scanning revealed extra-adrenal tumor sites (n = 29), allowing an accurate diagnosis of the disease's stage using a single-imaging technique. CONCLUSION: In patients with nonhypersecreting adrenal masses, radionuclide adrenal imaging, using specific radiopharmaceuticals such as norcholesterol, MIBG, and FDG, may provide significant functional information for tissue characterization. Norcholesterol and MIBG scans are able to detect benign tumors such as adenoma and pheochromocytoma, respectively. Conversely, FDG PET allows for recognition of malignant adrenal lesions. Therefore, adrenal scintigraphy is recommended for tumor diagnosis and, hence, for appropriate treatment planning, particularly when CT or MRI findings are inconclusive for lesion characterization.

19-Iodocholesterol↗
PubMed2001

Feasibility of dual-isotope coincidence/single-photon imaging of the myocardium.

UNLABELLED: Hybrid PET scanners offer the possibility of obtaining myocardial viability information from coincidence imaging of the positron emitter (18)F-FDG and perfusion measurements from a single-photon tracer-potentially simultaneously. This new approach is less costly and more readily available than dedicated PET and offers potential for improved FDG resolution and sensitivity compared with SPECT with 511-keV collimators. Simultaneous imaging of the coincidence and single-photon events offers the further advantages of automatic image registration and reduced imaging time. However, the feasibility of simultaneous coincidence/single-photon imaging or even immediately sequential imaging is unknown. In this study, the potential of using standard low-energy high-resolution (LEHR) collimators with hybrid PET to obtain coincidence and SPECT data was assessed. METHODS: Phantom and human studies were performed to investigate the effect of LEHR collimators on FDG coincidence imaging with a hybrid PET system, the effect of the presence of (99m)Tc during FDG coincidence imaging with LEHR collimators, and the effect of the presence of FDG during (99m)Tc SPECT imaging. RESULTS: FDG images were somewhat degraded (a measure of myocardial nonuniformity increased 10%) with LEHR collimators. With 148 MBq (4 mCi) (99m)Tc present during FDG imaging of a phantom, image quality was maintained and the number of detected coincidences changed by <5%. With (99m)Tc/(18)F whole-body ratios of 7:1, crosstalk from (18)F photons accounted for the majority of counts in the (99m)Tc SPECT images and resulted in severe artifacts. The artifacts were decreased with a simple crosstalk correction scheme but remained problematic. CONCLUSION: (99m)Tc/(18)F ratios of at least 9:1 and state-of-the-art reconstruction and crosstalk correction are likely to be required to perform immediately sequential coincidence/single-photon imaging of the myocardium with clinically useful results. Additional challenges remain before simultaneous imaging of coincidence events and single photons can be realized in practice.

Feasibility Studies↗
PubMed2001

Positron emission mammography-guided breast biopsy.

UNLABELLED: Positron emission mammography (PEM) is a technique to obtain planar images of the breast for detection of potentially cancerous, radiotracer-avid tumors. To increase the diagnostic accuracy of this method, use of minimally invasive methods (e.g., core biopsy) may be desirable for obtaining tissue samples from lesions detected with PEM. The purpose of this study was to test the capabilities of a novel method for performing PEM-guided stereotactic breast biopsies. METHODS: The PEM system consisted of 2 square (10 x 10 cm) arrays of discrete scintillator crystals. The detectors were mounted on a stereotactic biopsy table. The stereotactic technique used 2 PEM images acquired at +/-15 degrees and a new trigonometric algorithm. The accuracy and precision of the guidance method was tested by placement of small point sources of (18)F at known locations within the field of view of the imager. The calculated positions of the sources were compared with the known locations. In addition, simulated stereotactic biopsies of a breast phantom consisting of a 10-mm-diameter gelatin sphere containing a concentration of (18)F-FDG consistent with that reported for breast cancer were performed. The simulated lesion was embedded in a 4-cm-thick slab of gelatin containing a commonly reported concentration of FDG, simulating a compressed breast (target-to-background ratio, approximately 8.5:1). An anthropomorphic torso phantom was used to simulate tracer uptake in the organs of a patient 1 h after a 370-MBq injection of FDG. Five trials of the biopsy procedure were performed to assess repeatability. Finally, a method for verifying needle positioning was tested. RESULTS: The positions of the point sources were successfully calculated to within 0.6 mm of their true positions with a mean error of +/-0.4 mm. The biopsy procedures, including the method for verification of needle position, were successful in all 5 trials in acquiring samples from the simulated lesions. CONCLUSION: The success of this new technique shows its potential for guiding the biopsy of breast lesions optimally detected with PEM.

Biopsy, Needle↗
PubMed2001

18F-FDG PET detection of colonic adenomas.

UNLABELLED: The adenomatous polyp of the colon is clinically important as a precursor of colonic cancer. The aim of this preliminary study was to evaluate the potential usefulness of (18)F-FDG PET for detecting adenomatous polyps of the colon. METHODS: We performed a retrospective study of 110 subjects who underwent both PET study and total colonoscopy. On nonattenuation-corrected PET images, focal distinct FDG accumulation along the large intestine was considered a positive finding, and the PET results were compared with colonoscopic findings. Histology and adenoma size were determined by polypectomy. RESULTS: Fifty-nine adenomatous polyps, 5-30 mm in size, were found in 30 subjects by total colonoscopy. PET findings were positive for 14 of the 59 adenomas (24%). The positivity rate for PET images rose with the increase in size of the adenomas; it was 90% in adenomas (9/10) that were > or =13 mm. The overall false-positive rate was 5.5% (6/110 subjects). CONCLUSION: Increased glucose metabolism is observed in colonic adenomas, and detectability with PET increases with the increase in adenoma size. Adenomas are premalignant lesions, and it is important to realize that colonic adenomas may be found incidentally during an FDG PET study.

Adenomatous Polyps↗
PubMed2001

Troglitazone improves whole-body insulin resistance and skeletal muscle glucose use in type II diabetic patients.

UNLABELLED: Recently, troglitazone has emerged as an insulin sensitizer for the treatment of type II diabetes. However, its effect on skeletal muscle glucose use (SMGU) has not been studied. METHODS: To investigate the effect of troglitazone on SMGU in patients with type II diabetes, we undertook skeletal muscle (18)F-FDG PET dynamic imaging under insulin clamping before and after administration of SMGU to 20 patients with type II diabetes. Data were compared with those for 12 age-matched healthy volunteers. RESULTS: The whole-body glucose disposal rate (GDR) was significantly lower in patients (29.9 +/- 9.83 micromol/min/kg) than in control subjects (55.6 +/- 16.5 micromol/min/kg, P < 0.01), as was the SMGU (patients, 3.27 +/- 2.17 micromol/min/kg; control subjects, 10.9 +/- 6.4 micromol/min/kg; P < 0.01). After the therapy, GDR significantly improved in patients (29.3 +/- 14.6 micromol/min/kg, P < 0.05), as did SMGU (5.06 +/- 2.11 micromol/min/kg, P < 0.05). When results for patients with and without hypertension were separately analyzed, a significant improvement in SMGU after troglitazone was seen in both normotensive and hypertensive patients (normotensive [n = 10]: baseline, 3.67 +/- 2.89 micromol/min/kg; after therapy, 5.28 +/- 2.61 micromol/min/kg; P < 0.05; hypertensive [n = 10]: baseline, 2.89 +/- 1.22 micromol/min/kg; after therapy, 4.72 +/- 1.39 micromol/min/kg; P < 0.05). GDR in patients with and without hypertension was significantly improved by troglitazone (normotensive: baseline, 17.9 +/- 10.2 micromol/min/kg; after therapy, 31.9 +/- 15.9 micromol/min/kg; P < 0.01; hypertensive: baseline, 39.6 +/- 15.1 micromol/min/kg; after therapy, 47.7 +/- 23.8 micromol/min/kg; P < 0.05). The plasma free fatty acid concentration during insulin clamping was not changed by troglitazone (baseline, 1.1 +/- 0.86 mEq/L; after therapy, 0.93 +/- 0.65 mEq/L; P = not significant). CONCLUSION: Troglitazone can improve whole-body insulin resistance through the improvement of SMGU but not through a decline in plasma free fatty acid concentration in patients with type II diabetes with or without hypertension.

Blood Glucose↗
PubMed1982

Experimental study for cancer diagnosis with positron-labeled fluorinated glucose analogs: [18F]-2-fluoro-2-deoxy-D-mannose: a new tracer for cancer detection.

18F-2-fluoro-2-deoxy-D-glucose (18F-FDG) and 18F-2-fluoro-2-deoxy-D-mannose (18F-FDM) were tested as tumor diagnostic agents in a transplantable rat tumor and rabbit tumors. Tissue distribution studies in rats showed high tumor uptakes of both radiopharmaceuticals. The tumor uptake reached 2.65 +/- 0.61% dose 18 dose F-FDG/g and 2.65 +/- 0.81% dose 18F-FDM/g at 60 min and remained relatively constant until 120 min. Blood clearance both 18F-FDG and 18F-FDM was very rapid and tumor-to-blood ratios reached 22.1 and 29.4 at 60 min, respectively. Tumor-to-tissue ratios of both radiopharmaceuticals were very high in most organs, especially in the liver, kidney, and pancreas. Positron emission tomography (PET) of rabbit tumor with 18F-FDM clearly delineated the main tumor, central necrosis, and lymph node metastases. These data suggested that 18F-FDM, which is a by-product of 18F-FDG synthesis was also an excellent cancer diagnostic agent as well as 18F-FDG. This is not only a new feature of 18F-FDM, but also an economical improvement on cancer diagnosis by PET.

Animals↗