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PubMed2003

Positron emission tomography and single photon emission computed tomography in epilepsy care.

Radiopharmaceutical brain imaging is clinically applied in planning resective epilepsy surgery. Cerebral sites of seizure generation-propagation are highly associated with regions of hyperperfusion during seizures, and with glucose hypometabolism interictally. For surgical planning in epilepsy, the functional imaging modalities currently established are ictal single photon emission computed tomography (SPECT) with [(99m)Tc]technetium-hexamethylpropyleneamine oxime (HMPAO) or with [(99m)Tc]technetium-ethylene cysteine dimer (ECD), and interictal positron emission tomography (PET) with 2-[(18)F]fluoro-2-deoxyglucose (FDG). Ictal SPECT and interictal FDG PET can be used in presurgical epilepsy evaluations to reliably: (1) determine the side of anterior temporal lobectomy, and in children the area of multilobar resection, without intracranial electroencephalographic recording of seizures; (2) select high-probability sites of intracranial electrode placement for recording ictal onsets; and, (3) determine the prognosis for complete seizure control following anterior temporal lobe resection. Coregistration of a patient's structural (magnetic resonance) and functional images, and statistical comparison of a patient's data with a normal data set, can increase the sensitivity and specificity of these SPECT and PET applications to the presurgical evaluation.

Brain↗
PubMed2003

Imaging gliomas with positron emission tomography and single-photon emission computed tomography.

Over the last two decades the large volume of research involving various brain tracers has shed invaluable light on the pathophysiology of cerebral neoplasms. Yet the question remains as to how best to incorporate this newly acquired insight into the clinical context. Thallium is the most studied radiotracer with the longest track record. Many, but not all studies, show a relationship between (201)Tl uptake and tumor grade. Due to the overlap between tumor uptake and histologic grades, (201)Tl cannot be used as the sole noninvasive diagnostic or prognostic tool in brain tumor patients. However, it may help differentiating a high-grade tumor recurrence from radiation necrosis. MIBI is theoretically a better imaging agent than (201)Tl but it has not convincingly been shown to differentiate tumors according to grade. MDR-1 gene expression as demonstrated by MIBI does not correlate with chemoresistance in high grade gliomas. Currently, MIBI's clinical role in brain tumor imaging has yet to be defined. IMT, a radio-labeled amino acid analog, may be useful for identifying postoperative tumor recurrence and, in this application, appears to be a cheaper, more widely available tool than positron emission tomography (PET). However, its ability to accurately identify tumor grade is limited. 18 F-2-Fluoro-2-deoxy-d-glucose (FDG) PET predicts tumor grade, and the metabolic activity of brain tumors has a prognostic significance. Whether FDG uptake has an independent prognostic value above that of histology remains debated. FDG-PET is effective in differentiating recurrent tumor from radiation necrosis for high-grade tumors, but has limited value in defining the extent of tumor involvement and recurrence of low-grade lesions. Amino-acid tracers, such as MET, perform better for this purpose and thus play a complementary role to FDG. Given the poor prognosis of patients with gliomas, particularly with high-grade lesions, the overall clinical utility of single photon emission computed tomography (SPECT) and PET in characterizing recurrent lesions remains dependent on the availability of effective treatments. These tools are thus mostly suited to the evaluation of treatment response in experimental protocols designed to improve the patients' outcome.

Brain↗
PubMed2003

Applications of positron emission tomography/computed tomography image fusion in clinical positron emission tomography-clinical use, interpretation methods, diagnostic improvements.

Positron emission tomography (PET)/computed tomography (CT) scanners with combined dedicated high performance PET and CT scanners have been introduced recently in PET imaging. Oncological imaging with fluorodeoxyglucose (FDG) is currently the dominant application of PET. The addition of CT to PET offers many advantages, including obtaining a fast and relatively low-noise transmission scan, shortening the duration of the examination, adding precise anatomical information to FDG imaging, and providing additional diagnostic information. However, the use of CT for attenuation correction can lead to some artifacts that need to be considered when interpreting a PET/CT study: quantitative measurements may be altered, high density IV and oral and metallic objects may produce artifacts, and the registration of PET and CT may occasionally be suboptimal. Areas where using PET/CT offers particular potential advantages include the head and neck region, abdomen, and pelvis. Even in the thorax, PET/CT offers some advantages. Although clinical data evaluating the added value of PET/CT over PET are presently limited, preliminary results are very encouraging. More studies are warranted to clearly define the clinical impact of PET/CT over PET; however, it is clear this dedicated fusion technology will be very important for patient imaging in the coming years.

Artifacts↗
PubMed2001

Single-photon emission computed tomography and positron-emission tomography assays for tissue oxygenation.

Radiotherapy prescription can now be customized to target the major mechanism(s) of resistance of individual tumors. In that regard, functional imaging techniques should be exploited to identify the dominant mechanism(s). Tumor biology research has identified several mechanisms of tumor resistance that may be unique to radiation treatments. These fall into 3 broad areas associated with (1) tumor hypoxic fraction, (2) tumor growth rate, (3) and the intrinsic radiosensitivity of tumor clonogens. Imaging research has markers in various stages of development for quantifying relevant information about each of these mechanisms, and those that measure tumor oxygenation and predict for radioresistance are the most advanced. Positron-emission tomography (PET) measurement of oxygen 15 has yielded important information, particularly about brain tissue perfusion, metabolism, and function. Indirect markers of tumor hypoxia have exploited the covalent binding of bioreductive intermediates of azomycin-containing compounds whose uptakes are inversely proportional to intracellular oxygen concentrations. Pilot clinical studies with single-photon emission computed tomography (SPECT) and PET detection of radiolabeled markers to tumor hypoxia have been reported. Recently, other studies have attempted to exploit the reduction properties of both technetium and copper chelates for the selective deposition of radioactive metals in hypoxic tissues. A growing number of potentially useful isotopes are now available for labeling several novel chemicals that could have the appropriate specificity and sensitivity. Preclinical studies with "microSPECT" and "microPET" will be important to define the optimal radiodiagnostic(s) for measuring tissue oxygenation and for determining the time after their administration for optimal hypoxic signal acquisition. Radiolabeled markers of growth kinetics and intrinsic radiosensitivity of cells in solid tumors are also being developed. We conclude that radiation oncology is uniquely positioned to benefit from functional imaging markers that identify important mechanisms of tumor radioresistance, since several strategies for overcoming these individual mechanisms have already been identified.

Animals↗
PubMed1998

[Computerized tomography and F-18-FDG positron emission tomography in staging of malignant lymphomas: a comparison].

PURPOSE: To determine the value of F-18-FDG-positron emission tomography (FDG-PET) compared with computed tomography (CT) in the staging of malignant lymphomas. MATERIAL AND METHOD: 50 patients with biopsy-proven lymphoma were studied with FDG-PET and CT. The results in initial, posttherapeutic and staging of recurrence were compared. RESULTS: 37 of 65 FDG-PET were identical with CT. 28 studies showed differences. 14 post-therapeutically and one of the initial studies led to downstaging by FDG-PET were as upstaging resulted in one case of initial staging. In two cases false positive pulmonary FDG accumulations caused an upstaging. CONCLUSION: FDG-PET was at least comparable to CT in recording the extension of a newly diagnosed lymphoma, or its recurrence. Upstaging according to FDG-PET occurred only once in initial staging. FDG-PET plays its most important role in the evaluation of residual mass in CT after therapy by accumulating FDG in viable tumour rather than in fibrotic tissue. 14 cases of downstaging according to FDG-PET resulted.

Adolescent↗
PubMed1984

[Comparative studies on imaging artificial bone lesions--conventional tomography and computed tomography].

Conventional tomography (T) and computer tomography (CT) were used for examining 97 artificial bone lesions at various sites. The purpose of the study was to determine how far CT can replace T in the diagnosis of skeletal abnormalities. The results have shown that modern CT, particularly in its high resolution form, equals T and provides additional information (substrate of a lesion, its relationship to neighbouring tissues, simultaneous demonstration of soft tissues etc.). These cannot be shown successfully by T. It follows that CT is indicated as the primary method of examination for lesions of the facial skeleton, skull base, spine, pelvis and, to some extent, extremities.

Animals↗
PubMed2003

Staging of non-small-cell lung cancer with integrated positron-emission tomography and computed tomography.

BACKGROUND: We compared the diagnostic accuracy of integrated positron-emission tomography (PET) and computed tomography (CT) with that of CT alone, that of PET alone, and that of conventional visual correlation of PET and CT in determining the stage of disease in non-small-cell lung cancer. METHODS: In a prospective study, integrated PET-CT was performed in 50 patients with proven or suspected non-small-cell lung cancer. CT and PET alone, visually correlated PET and CT, and integrated PET-CT were evaluated separately, and a tumor-node-metastasis (TNM) stage was assigned on the basis of image analysis. Nodal stations were identified according to the mapping system of the American Thoracic Society. The standard of reference was histopathological assessment of tumor stage and node stage. Extrathoracic metastases were confirmed histopathologically or by at least one other imaging method. A paired sign test was used to compare integrated PET-CT with the other imaging methods. RESULTS: Integrated PET-CT provided additional information in 20 of 49 patients (41 percent), beyond that provided by conventional visual correlation of PET and CT. Integrated PET-CT had better diagnostic accuracy than the other imaging methods. Tumor staging was significantly more accurate with integrated PET-CT than with CT alone (P=0.001), PET alone (P<0.001), or visual correlation of PET and CT (P=0.013); node staging was also significantly more accurate with integrated PET-CT than with PET alone (P=0.013). In metastasis staging, integrated PET-CT increased the diagnostic certainty in two of eight patients. CONCLUSIONS: Integrated PET-CT improves the diagnostic accuracy of the staging of non-small-cell lung cancer.

Aged↗
PubMed2004

Results of radio frequency ablation of primary and secondary liver tumors: long-term follow-up with computed tomography and positron emission tomography-18F-deoxyfluoroglucose scanning.

BACKGROUND: In the literature, promising results have been obtained with radiofrequency ablation (RFA) of primary liver malignancies (e.g. hepatocellular carcinoma, HCC) and secondary liver malignancies (e.g. metastases of colorectal tumors). In our center, positron emission tomography with FDG (FDG-PET) and computed tomography (CT) were used for follow-up. Patient outcome was compared with that in the literature, and PET and CT were analyzed regarding positive and negative predictive values for early detection of tumor recurrence. METHODS: The data were analyzed of patients who were treated with RFA for primary or secondary liver tumors between January 1999 and December 2002. Indications for treatment with RFA were liver tumors that could not be resected owing to size, number, or tumor location. In all patients, a CT scan was performed before RFA, and follow-up was performed with a CT scan in all patients and with an additional PET scan at various intervals in 11 patients. At evaluation with PET, tumor recurrence was defined as positive uptake of tracer either at the previous RFA lesion or at a new site in the liver. RESULTS: In total, 15 patients (8 M, 7 F) were treated in 21 sessions with RFA. The mean follow-up period was 16.8 months (range: 7-42). Average age of the patients was 63 years (range: 40-74). One patient had a primary liver tumor; all other patients had metastases of the breast (1), ovary (1), renal cells (1), and colorectal carcinoma (11 patients). The mean number of tumors per patient was 2.7 (range: 1-5). No treatment-related morbidity or mortality occurred. In 4 of 11 patients evaluated with PET at a mean period of 6.8 months, positive uptake of tracer was noted. At CT evaluation, tumor recurrence was observed in 4 of these patients, at a mean time of 9.8 months. Two patients (13.3%) died of cancer recurrence during follow-up. CONCLUSIONS: Tumor recurrence is comparable with that in other studies. Centrally located tumors showed more recurrence than peripheral tumors. The use of PET in combination with CT scan at follow-up may lead to earlier detection of tumor recurrence than contrast-enhanced CT alone.

Adult↗
PubMedDate not supplied

Functional imaging of vegetative state applying single photon emission tomography and positron emission tomography.

Nuclear medicine techniques, such as single photon emission tomography (SPECT) and positron emission tomography (PET) have been applied in patients in a vegetative state to investigate brain function in a non-invasive manner. Parameters investigated include glucose metabolism, perfusion at rest, variations of regional perfusion after stimulation, and benzodiazepine receptor density. Compared to controls, patients in a vegetative state show a substantial reduction of glucose metabolism and perfusion. While patients post-anoxia exhibit a rather homogenous cortical reduction of glucose metabolism, patients after head trauma often show severe cortical and sub-cortical reductions at the site of primary trauma. To distinguish reduced glucose metabolism due to neuronal inactivation from neuronal loss, flumazenil-PET, an indicator of benzodiazepine receptor density, could add valuable information on the extent of brain damage. Activation studies focus on the evaluation of residual brain network, looking for processing in secondary projection fields. So far the predictive strength concerning possible recovery for the individual patient is limited, and PET and SPECT are not routine procedures in the assessment of patients in a vegetative state.

Brain↗
PubMed2002

Advantages of positron emission tomography (PET) with respect to computed tomography in the follow-up of lymphoma patients with abdominal presentation.

For abdominal lymphoma patients, fluorine-18 fluorodeoxyglucose positron emission tomography (PET) provides unique information on the presence of residual active disease. We provide an update on the largest reported cohort of patients whose management following induction therapy was based on routine PET and computed tomography (CT) restaging. Fifty-nine patients with Hodgkin's disease or aggressive non-Hodgkin's lymphoma presenting abdominal involvement (35% with bulky disease) were studied with both PET and CT following combined chemotherapy/radiation treatment. After treatment, 3/3 (100%) patients who were PET+/CT- relapsed, compared with 0/7 patients in the PET-/CT- subset. Among the 49 patients who were CT+, six of the 10 (60%) who were PET+ relapsed, as compared with only two of the 39 (5%) who were PET-. The actuarial relapse-free survival (RFS) rates were 0 and 100% in the PET+/CT- and PET-/CT- subsets, respectively. In the PET+/CT+ subset, RFS was 94% at 5 years. PET restaging is very valuable for the identification of patients who would need appropriate second-line therapy because of the presence of residual active abdominal disease and should be made widely available in combination with CT.

Abdominal Neoplasms↗
PubMed2002

Detecting mediastinal lymph node metastases in non-small-cell lung cancer using a combination of technetium-99m tetrofosmin chest single photon emission computed tomography and chest computed tomography.

UNLABELLED: The staging of non-small-cell lung cancer (NSCLC) to detect mediastinal lymph node (MLN) metastases is very important for determining the therapeutic strategy. METHODS: Thirty-four patients with proven NSCLC were enrolled in this study. All patients underwent chest computed tomography (CT) and technetium-99m (Tc-99m) tetrofosmin chest single photon emission computed tomography (SPECT) preoperative staging. Mediastinal lymph node metastases were determined on the basis of postoperative pathologic findings to compare the diagnostic accuracy of chest CT with that of Tc-99m tetrofosmin chest SPECT. RESULTS: Tc-99m tetrofosmin chest SPECT showed a diagnostic accuracy rate of 85.3% in detecting MLN metastases. Chest CT had an accuracy rate of 73.5%. If either Tc-99m tetrofosmin chest SPECT or chest CT with positive findings was considered as positive findings, the sensitivity was 94.7%. If either Tc-99m tetrofosmin chest SPECT or chest CT with negative findings was considered as negative, the specificity was 93.3%. CONCLUSION: Tc-99m tetrofosmin chest SPECT was more accurate than chest CT in detecting MLN metastases in NSCLC patients. In addition, the combined use of Tc-99m tetrofosmin chest SPECT and chest CT could significantly increase the sensitivity and specificity compared with the single use of either Tc-99m tetrofosmin chest SPECT or chest CT.

Adult↗
PubMed2003

Detection of recurrent or residual nasopharyngeal carcinomas after radiotherapy with technetium-99m tetrofosmin single photon emission computed tomography and comparison with computed tomography--a preliminary study.

The effectiveness of technetium-99m tetrofosmin (Tc-TF) single photon emission computed tomography (SPECT) of the head and neck for detecting recurrence of nasopharyngeal carcinomas (NPC) was evaluated and compared with computed tomography (CT). Both Tc-TF SPECT and CT of the head and neck were performed in 36 NPC patients 4 months after radiotherapy. All 36 then underwent histopathological examinations of nasopharyngeal biopsies. Based on the histopathological results, the sensitivity, specificity, and accuracy of visually interpreted Tc-TF SPECT images, to differentiation of recurrent NPC from benign lesions, were 64%, 96%, and 86%, respectively. The sensitivity, specificity, and accuracy of CT for detecting recurrent NPC were 73%, 88%, and 83%, respectively. The Tc-TF SPECT has a better specificity but a lower sensitivity to differentiate benign lesions and recurrent/residual NPC when compared with CT. Combined Tc-TF SPECT and CT sensitivity and specificity were 100% and 88%, respectively. There are much better either test alone. However, further studies, including a larger NPC patient population, are warranted to determine the exact role and clinical usefulness of Tc-TF SPECT to differentiate benign lesions and recurrent/residual NPC.

Adolescent↗
PubMed2005

Computed tomography and 18F-FDG positron emission tomography for therapy control of Hodgkin's and non-Hodgkin's lymphoma patients: when do we really need FDG-PET?

BACKGROUND: The aim of this study was to evaluate the accuracy of computed tomography (CT) and [(18)F]fluoro-deoxy-d-glucose positron emission tomography (FDG-PET) for prediction of progression-free survival of Hodgkin's disease (HD) and non-Hodgkin's lymphoma (NHL) patients after completion of therapy. PATIENTS AND METHODS: CT and FDG-PET were performed in 40 HD, 17 indolent NHL and 44 aggressive NHL patients (29 women, 72 men; aged 41+/-14 years) in a median of 2 months after therapy. Progression-free survival was evaluated using the Kaplan-Meier method. Independent prognostic factors were identified by means of Cox proportional hazards model. RESULTS: CT imaging results were progressive disease (PD) in five, stable disease (SD) in 57, and partial response (PR) or complete remission (CR) in 39 patients. FDG-PET suggested residual lymphoma in 24 patients. Three-year progression-free survival rates after exclusion of five PD patients were: 100% (PET negative; CT: PR or CR), 81% (PET negative; CT: SD), 21% (PET positive; CT: SD) and 0% (PET positive; CT: PR). FDG-PET (P<0.0001) and bulky disease (P <0.05) were identified as independent prognostic variables. CONCLUSIONS: Among lymphoma patients with PR and SD on CT, FDG-PET discriminated those destined to progress into a low risk of < or =20% and a high risk for recurrence of > or =80%.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed2006

Characteristics of advantages of positron emission tomography over computed tomography for N-staging in lung cancer patients.

OBJECTIVE: We analyzed the characteristics of advantages of positron emission tomography (PET) over computed tomography (CT) for N-staging in lung cancer patients. METHODS: Preoperative PET and CT scans were performed for 2057 lymph node stations in 205 patients with peripheral-type lung cancer. The advantages of PET over CT for N-staging were analyzed among lymph node locations and histological subtypes. RESULTS: The pathological N-stages were N0 in 143 patients, N1 in 31, N2 in 24 and N3 in 7. PET was able to diagnose N0, N2 and N3 diseases more accurately than CT (P=0.03, 0.01 and 0.02, respectively), but there was no significant difference between the two modalities for N1 disease. In the upper mediastinal lymph node stations, both false-negative and false-positive were significantly less frequent with PET than with CT (P=0.001). In the lower mediastinal and supra clavicle lymph nodes, PET showed a lower frequency of false-negative than CT (P=0.04 and 0.003, respectively), but there was no significant difference in the frequency of false-positive between the two modalities. Among histological types, PET could stage adenocarcinoma with less frequent false-negative and squamous cell carcinoma with less frequent false-positive than CT (P=0.02 and 0.005, respectively). CONCLUSION: For N-staging, PET was superior to CT for the following: (1) more accurate for N0, N2 and N3 diseases but not for N1; (2) lower frequency of false-positive in the upper mediastinal nodes; and (3) lower frequencies of false-negative in adenocarcinoma and false-positive in squamous cell carcinoma. Recognizing these advantages of PET could make the N-staging of lung cancer more accurate.

Adenocarcinoma↗
PubMed2002

Evaluation of 18 F-fluorodeoxyglucose positron emission tomography and computed tomography with histopathologic correlation in the initial staging of head and neck cancer.

OBJECTIVE: To prospectively evaluate the use of 18F-Fluorodeoxyglucose positron emission tomography (FDG-PET) in the initial staging of squamous cell head and neck carcinoma. SUMMARY BACKGROUND DATA: The status of cervical lymph nodes is an important prognostic factor and determinant of management approach in squamous cell head and neck cancer. METHODS: FDG-PET findings were compared with those of computed tomography (CT) before removal of the primary tumor and/or neck dissection. Histopathologic analysis was used as the gold standard for assessment of the sensitivity and specificity of these modalities. RESULTS: FDG-PET correctly identified the primary tumor in 35 of 40 patients in whom the site of the primary was known clinically and still present (sensitivity 88%). None of four unknown primaries were detected. Tumors not detected by FDG-PET were generally superficial, with depths of less than 4 mm. CT correctly identified 18 of the 35 primary tumors (sensitivity 51%). Eleven of 17 CT false-negative tumors were detected by FDG-PET. The sensitivity and specificity for the presence of metastatic neck disease on FDG-PET were 82% and 100%, respectively; those for CT were 81% and 81%, respectively. FDG-PET was true positive for metastatic neck disease in two of the three CT false-negative patients. CONCLUSIONS: FDG-PET shows promise in the initial staging of head and neck cancer and provides additional accuracy to a conventional staging process using CT.

Adult↗
PubMed1992

Receptor imaging by positron emission tomography and single-photon emission computed tomography.

Positron emission tomography (PET) has been used primarily to measure regional brain metabolism and blood flow. Single-photon emission computed tomography (SPECT) also can be used to measure brain perfusion. Receptor imaging by PET and SPECT, however, offers distinctive advantages over the more established flow/metabolism imaging methods, including improved chemical specificity and improved sensitivity in detecting changes in disease. Radioligands are available for PET and SPECT imaging of many neuroreceptors, including the opiate receptor, the dopamine receptor, and the muscarinic cholinergic receptor. A new focus of interest is the imaging and quantification of presynaptic neurotransmitter reuptake sites.

Brain↗
PubMed1983

Discrepancies in brain tumor extent as shown by computed tomography and positron emission tomography using [68Ga]EDTA, [11C]glucose, and [11C]methionine.

A patient with an anaplastic (malignant) astrocytoma was examined with computed tomography (CT) and with positron emission tomography (PET), in the latter case using [68Ga]EDTA, [11C]glucose, and [11C]methionine. The CT examination as well as the [68Ga]EDTA study showed a small tumor located in the region of the head of the left caudate nucleus. The [11C]glucose examination showed increased uptake on the same region, as did the [11C]methionine examination, but the latter also showed a considerable uptake in the entire left thalamic region. The patient died 15 days after the [11C]methionine study and a histologic evaluation of thin sections obtained at autopsy showed excellent agreement between tumor extent and activity distribution after [11C]methionine administration. The tumor tissue seen only with [11C]methionine was histologically different from that part of the tumor observed with the other tracers. Although cytologically similar, the latter showed large necrotic areas and an ability to induce marked endothelial proliferation, whereas in the former neither necroses nor notable endothelial proliferation was seen. In this case more than 50% of the tumor would have remained radiologically imperceptible without the [11C]methionine PET examination.

Astrocytoma↗
PubMed1984

Positron emission tomography and computed tomography assessments of the aging human brain.

The relationship between alterations in brain structure and brain function was studied in vivo in both young and elderly human subjects. Computed tomography revealed significant age-related ventricular and cortical sulcal dilatation. The cortical changes were most closely related to age. Positron emission tomography failed to show regional changes in brain glucose metabolic rate. The results suggest that the normal aging brain undergoes structural atrophic changes without incurring regional metabolic changes. Examination of the correlations between the structural and the metabolic measures revealed no significant relationships. These data are discussed with respect to the significant structure-function relationships that have been reported in Alzheimer disease.

Adult↗