Clinical positron imaging : official journal of the Institute for Clinical P.E.T最新文献

Purpose: To reduce the artifact caused by cardiac uptake of F-18 fluorodeoxyglucose (FDG); we investigated the change in myocardial FDG uptake after placing a group of patients on a carbohydrate-restricted diet.

Methods: Case control study involving 130 whole body FDG PET scans. 73 scans were of patients on carbohydrate-restriction; the remaining 57 were without dietary restrictions. Dietary intake for the last meal prior to scanning was recorded for both groups. Coronal and axial images were assessed and scored based on myocardial FDG uptake the presence of associated image artifacts.

Results: Of the 73 patients on the diet, 50 did not consume carbohydrates, while of the 57 patients without dietary restriction, 13 did not consume carbohydrates. Of the 67 patients from both groups who consumed carbohydrates prior to their PET scan, 17 (25.4%) had a clinically significant image artifact versus only 6 (9.5%) of the 63 patients who did not consume carbohydrates (P = 0.018) in their meals prior to scanning. The odds ratio was calculated to be 3.23 (confidence interval 1.09–10.00), indicating that the risk a clinically significant image artifact will occur is 3.23 times higher for patients who consume carbohydrates in their last meal prior to scanning.

Conclusion: A substantial reduction in the prevalence of myocardial FDG uptake image artifacts among patients who did not consume carbohydrates was observed. A carbohydrate dietary restriction prior to scanning may play a significant role in increasing lesion detectability and in preventing false negative scans when imaging for thoracic neoplasm.

The purpose of the study was to evaluate a new technology of simultaneous transmission and F-18 FDG emission tomography (FDG-TET) in tumor imaging and its impact on patient management.

Emission and transmission devices were installed on the same gantry. 167 patients with histologically proven malignancy were evaluated at diagnosis or during follow up. Eight mCi of FDG were injected for PET and a low dose X-ray tube was used for CT. The FDG and CT were first interpreted independently, without knowledge of findings in other imaging modality. Subsequently fusion images were analyzed.

FDG-TET changed the interpretation of PET or CT in 75 patients (45%). In 60 patients TET allowed for correct localization of lesions on the PET studies. In 15 patients, FDG uptake was found in sites of physiologic activity. In 12 patients lesions previously missed on CT were retrospectively identified. In 21 patients, TET detected 34 previously unknown sites of disease.

FDG-TET changed the clinical management of 29 patients (17%). The stage of disease was changed in 9 patients. Early diagnosis of recurrence was made in 8 patients. Seven patients were referred for previously unplanned surgery. In 6 patients surgery was cancelled. Fifteen patients received additional chemo- or radiotherapy.

Diagnosis of cancer on CT is based on a change in size or attenuation of a mass. PET shows the metabolic status of a lesion but lacks anatomical landmarks. FDG-TET improves the diagnostic accuracy in cancer and may have a significant impact on patient management.

The purpose of this study was to develop and evaluate an F-18 labeled choline tumor imaging agent.

FCH was synthesized through the intermediate F-18 fluorobromomethane that was used to alkylate dimethylethanolamine. The isolated FCH was evaluated in PC-3 human prostate cancer cells, PC-3 human prostate cancer xenograft studies, and human prostate and brain tumor patients.

FCH was accumulated at a slightly lower rate than FDG in the cultures of PC-3 cells. Inhibition of choline transport and phosphorylation by hemicholinium-3 resulted in a 90% decrease in FCH uptake without altering FDG uptake. FCH had a similar biodistribution as C-14 choline in mice, with the liver and kidneys being the primary sites of uptake. Tumor uptake of FCH and FDG were comparable at 45-60 mins after injections. The tumor:blood ratio was higher for FCH (5.3 ± 2.4) than for FDG (3.2 ± 0.3). Brain uptake of FCH was 10% that of FDG. FCH-PET studies were compared to FDG-PET studies. In the prostate cancer patients, more lesions have been seen on the FCH studies than on the FDG studies, and the standardized uptake values (SUV) have been higher with the FCH. Decreases in FCH-PET SUV have been noted in patients treated by androgen deprivation. Patients with suspected recurrent brain tumors have had more clearly defined abnormal accumulation on the FCH-PET scans than on the FDG-PET scans. The FCH is not accumulated by normal cortex.

FCH is a promising imaging agent for the evaluation of metastatic prostate cancer and recurrent brain tumor.

Background: ¹⁸FDG PET scans are often interpreted on the basis of visual estimation of regional tracer uptake. Whether semiquantitative analysis may help clinicians in the recognition of neoplastic masses still remains debated.

Materials and Methods: 134 patients with 144 dubious lesions on CT scans (89 pulmonary, 16 hepatic, 39 soft tissue) were studied by means of PET and ¹⁸(F)fluorodeoxyglucose. PET images were qualitatively interpreted by the consensus of two nuclear physicians. Standardized uptake value (SUV) and SUV lean were quantified in both normal and suspicious tissues. SUVs results in the lesion were also expressed as normalized values for the normal mean value in each organ (SUVs/org) and for the overall mean value in normal tissues (SUVs/norm).

Results: All patients underwent cytological and/or hystological evaluation of the lesions: 53/144 (37%) were recognized as negative while 91/144 (63%) as positive for primary or metastatic disease. Qualitative analysis resulted in 75% specificity and 93% sensitivity. SUVs, SUVs lean, SUVs/org and SUVs/norm resulted significantly (p < 0.001) higher in positive than in negative lesions by cytology/histology. ROC curves analysis provided optimal cut-off values of 2.5, 0.8, 2.5 and 3, for SUVs, SUVs lean, SUVs/org and SUVs/norm, respectively. Using these cut-offs, specificity and sensitivity resulted 90 and 94%, 83 and 97%, 88 and 93%, 94 and 93%, respectively.

Conclusion: Our data suggest that, in patients with CT scan suspicious lesions, visual analysis of PET scans is affected by a high number of false negative results. Semiquantitative assessment of regional metabolic activity has an incremental value and should be used in PET scan interpretation of dubious lesions.

Purpose: To compare the sensitivity of F18 - FDG Positron Emission Tomography (PET), Computed Tomography (CT) and Planar Gallium 67-Citrate (GS) in the diagnosis of Hodgkin's Disease.

Materials and Methods: Thirty (30) adult patients with histopathologically confirmed diagnosis of Hodgkin's Disease between Oct 97 and June 98 at KFSH & RC had the three diagnostic imaging modalities for the initial work up; in twenty eight patients for newly diagnosed and in two patients for recurrent disease. Nodular sclerosis was the histological subtype in 25 patients, mixed cellularity in 3 and lymphocytic predominance in 2.

Results: For the initial evaluation of the results, a positive site by any of the three diagnostic imaging modalities was considered actual location of the disease. The patient-site sensitivity of PET, CT and for GS were 93.33%, 80% and 53.3% respectively. False negative results were observed in 2 patients with PET, 7 with CT and 14 with GS. The Spleen was the commonest site for false negative result in GS (4 patients) axilla and bones in CT (2 patients each), the 2 patients with false negative results with PET were in the lung. The difference in sensitivity between PET and GS was statistically significant (P = 0.002), but was not significant between PET and CT (P = 0.18). Although CT showed better sensitivity and accuracy when compared with GS, that didn't reach statistical significance (P = 0.09).

Conclusion: PET Scan has the highest sensitivity in the initial evaluation in this small group of patients with Hodgkin Disease, especially when compared with GS. Evaluations of the final sensitivity, specificity and accuracy of these imaging modalities will be presented.

Segmented attenuation correction (SAC) has been introduced as a method of reducing transmission scan times without degrading the quality of PET images. Presented are the results of a clinical evaluation of a SAC algorithm implemented on the GE Advance PET system. FDG whole body patient emission scans of eight minute duration were acquired. Dynamic transmission (Tx) scans of 5 frames and 6 minute total duration were acquired and rebinned into Tx scans of 2, 3, 4, 5 and 6 minute duration. Images (I) were generated using iterative reconstruction with measured attenuation correction (MAC) or SAC for all Tx scans—denoted as I(Tx6MAC), I(Tx6SAC), etc. Anthropomorphic phantom data was also acquired and reconstructed using the same methodology. Images were evaluated quantitatively using the normalized mean square error (NMSE) of different regions and the variance and bias of liver activity. I(Tx6MAC) served as the reference. A blinded observer ranked image quality. The NMSE increased as the Tx duration decreased; for patient images the NMSE was typically 20% and 40% greater for I(Tx3SAC) and I(Tx2SAC) than I(Tx6SAC) respectively. The NMSE of the MAC images increased much more rapidly as the Tx duration decreased. Similar trends were found for the variance in the liver. Bias in liver activity of the SAC images was approximately −8% for large patients. The observer consistently preferred SAC images over MAC images. SAC images demonstrated improved boundary delineation and reduced noise in areas of homogeneous high activity background. Areas of discordance were projected into areas of large difference between Tx and segmented Tx sinograms. This study has validated the use of SAC with short Tx scans. Images reconstructed with Tx scans of 3 minutes were not compromised with noise or severe artifacts.

Assessing prostate metastases is difficult with conventional radiographic modalities as few patients have soft tissue involvement and most have only bone lesions. Even with FDG PET, problems due to decreased avidity compared to other tumor types can occur. We assessed PET's ability to monitor changes in such tumors during an anti-angiogenic therapy. We measured changes in tumor blood flow (¹⁵O), blood volume (¹¹CO), ¹⁸F-FDG uptake and “metabolic volume” before and during thalidomide treatment, to see if these changes correlated with changes in PSA values.

Six patients with androgen-independent prostate cancer were imaged with ¹⁸F-FDG, ¹¹CO, and ¹⁵O water before and during (mean interval 63 days, range 55-76 days) thalidomide therapy (200-1200mg/day). Lesions were visually identified on FDG images (9 bone, 5 soft tissue lesions). VOI's were generated by 3D region growing, with a 50% maximum pixel threshold. These VOI's were registered with, and applied to, the ¹¹CO and water studies. Correlations with PSA values were done using the Spearman rank test.

The change in maximum (r = 0.77, p = 0.06) and mean FDG value (r = 0.83, p = 0.03), functional FDG volume (r = 0.66, p = 0.14), and 11-CO blood volume (r = 0.77, p = 0.06) all correlated with the change in PSA. Changes in blood flow values were smaller than the variance of the method for repeated measures, likely due to low flow values in bone.

Changes in blood volume measured by ¹¹CO, and the mean and peak activity and functional volume measured by ¹⁸F-FDG, correlate with changes in PSA and may be useful in monitoring anti-angiogenic therapy in prostate cancer.

Purpose: The frequency of adrenal metastases from non-small cell lung cancer (NSCLC) varies between 4 to 25%. Adrenal metastases are frequently missed (78%) by Computed Tomography (CT) and Magnetic Resonance Imaging (MRI). The purpose of this study was to characterize the patterns of adrenal gland involvement from lung cancer by 18-F-Fluorodeoxyglucose Positron Emission Tomography (¹⁸FDG-PET).

Methods: Retrospective review of patients evaluated for known or suspected lung carcinoma. Results of ¹⁸FDG-PET, CT, MRI, and scans were compared.

Results: From February 1996 to May 2000, 91 patients with known (85 patients) or suspected (6 patients) lung cancer were evaluated with ¹⁸FDG-PET scan. Twenty-two patients (mean age 63, range 38-88 years) had abnormal adrenal glands by either ¹⁸FDG-PET (16 patients), CT (12 patients) or MRI (1 patient). In 13 cases ¹⁸FDG-PET scan was ordered to clarify CT or MRI findings. Only 7 patients showed adrenal gland involvement: 5 patients (5.5%) with unilateral disease and 2 patients (2.2%) with bilateral disease. PET depicted unsuspected findings in 9 patients: 8 patients (8.8%) with unilateral disease and 1 patient (1.1%) with bilateral disease.¹⁸FDG-PET upstaged 9 patients from limited (N1M0) to widespread disease (M1), thus obviating surgical intervention.

Conclusion: This study demonstrates the potential of ¹⁸FDG-PET scanning in revealing unsuspected adrenal metastases in patients with early stages of NSCLC as well as characterizing CT or MRI equivocal adrenal masses.

Background: In cost-effective analysis regarding to utilization of FDG-PET on lung nodules, most studies focused on lung lesions themselves (benign vs. malignant) and possible metastases if primary lesion is malignant. However, in a patient with pulmonary nodules, abnormal sites of increased FDG uptake on a whole-body PET scan may either the primary tumor or lesions unrelated to lung malignancy. The incidence of detection of the unsuspected lesions, which often changes the management of these patients, should also be included in the cost-effective analysis.

Methods: We retrospectively analyzed 213 cases referred for evaluation of pulmonary nodules. 89 of them proved to have lung malignancy and were excluded in our study. None of the remaining 124 patients had prior clinical or radiographic evidence of other abnormalities before undergoing FDG-PET. All unsuspected lesions were verified either histologically or by the clinical course of the disease.

Results: Among the 124 patients without lung cancer, FDG-PET revealed unsuspected abnormality in eight patients. These include other malignancy (colon cancer × 3, lymphoma × 1) and benign lesions (sarcoidosis × 3, cystic kidney × 1). None of the 124 patients studied had additional pathology found during follow-up.

Conclusion: The routine uses of FDG-PET for characterizing the lung lesions significantly increases the chances detecting unexpected other pathology. The incidental FDG-PET findings of unsuspected lesions, especially those unrelated to lung cancers, no doubt have a major impact on the management of these patients and may prove to be cost-effective.

Purpose: To study the capability of positron emission tomography for mitochondrial dysfunction diagnosis on basis of oxidative metabolism evaluation.

Methods: PET studies were carried out in 13 patients (pts.) aged from 2 to 13 years (7,5+3,1) with CMP: hypertopic (HCMP) – 4, dilated (DCMP) – 9.The dynamic study with [C-11]-acetate was performed for evaluation of Krebs cycle activity. Rate constant (k_mono) and [C-11]-activity clearance half-time (t_1/2) were calculated using myocardial time-activity curve (from 3 to 10 min.). Myocardial perfusion was assessed with [N-13]-ammonia, glucose metabolism - with [F-18]-fluorodeoxylucose (FDG).

Results: Perfusion was normal in hypertohic parts of left ventricle (LV) in patients with HCMP. Krebs cycle activity was reduced (k_mono = 0,077 ± 0,013 min⁻¹). Glucose utilisation was increased in comparison with norm. Thus, Krebs cycle activity reduction (mitochondrial dysfunction) was compensated by increasing glycolysis activity. Perfusion was normal in all children with DCMP. Krebs cycle activity was reduced in LV in 6 pts. (k_mono = 0,065 ± 0,029 min⁻¹), normal - in 3 (k_mono = 0,104 ± 0,010 min⁻¹). All children had normal oxidative metabolism in right ventricle (k_mono = 0,129 ± 0,203 min⁻¹).Focal perfusion defects were noted in 2 pts. with CMP. In this region the Krebs cycle activity was decreased more then another LV parts. It means that ischemic injuries were. Glucose utilisation reduction in this field means that injuries were irreversible.

Conclusion: PET study showed Krebs cycle activity reduction in children with cardiomyopathy was noted despite in normal perfusion (mitochondrial dysfunction) vs. ischemic injuries of myocardium.