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Effect of biventricular pacing on metabolism and perfusion in patients affected by dilated cardiomyopathy and left bundle branch block: evaluation by positron emission tomography.

AIMS: Evaluate the possible changes in myocardial metabolism and perfusion induced by biventricular pacing (BIVP) in patients affected by dilated cardiomyopathy (DC) and left bundle branch block (LBBB). METHODS AND RESULTS: Eight male patients (aged 60-79 years, mean 69) affected by DC (NYHA functional class III and ejection fraction <40%) were submitted to cardiac PET in basal condition and 3 weeks after the implantation of a biventricular device. Metabolism was evaluated using F18-fluorodeoxyglucose (FDG), by the glucose load-insulin technique, and perfusion by N13-ammonia (NH3), injected at rest. Visual and a semi quantitative analyses were performed, calculating by ROIs the septum to lateral uptake ratio (SLR). The myocardial blood flow (MBF) was also calculated in ml/min/g using a dynamic acquisition and a modified Patlak method. In all 8 patients a selective defect in FDG uptake in the septum was present in basal condition (mean SLR 0.59+/-0.17) with a 'reverse mismatch' effect with respect to NH3 (mean SLR 1.07+/-0.18). During BIVP the distribution of FDG in the septal area significatively improved (mean SLR 0.86+/-0.15 P=0.011 with respect to basal); on the contrary, no significant changes were found in NH3 uptake (mean SLR 1.02+/-0.23, P=ns). On quantitative analysis the mean MBF in the septum was 1.05+/-0.37 in basal condition and did not significantly change during BIVP (0.95+/-0.34, P=0.06). CONCLUSIONS: Our results suggest that, in patients affected by DC and LBBB, BIVP improves the septal glucose metabolism without significant changes in myocardial perfusion.

Aged↗

Post-systolic shortening during dobutamine stress echocardiography predicts cardiac survival in patients with severe left ventricular dysfunction.

BACKGROUND: Patients with severe left ventricular dysfunction and myocardial viability by dobutamine stress echocardiography (DSE) or F18-fluorodeoxyglucose-single-photon emission computed tomography (FDG-SPECT), experience improved survival after coronary revascularization. Pulsed wave-tissue Doppler imaging (PW-TDI)-derived ejection phase shortening (EPS) and post-systolic shortening (PSS) velocities may help to quantify DSE. We assessed these variables in a prospective long-term follow-up. METHODS: Eighty patients (58 men, mean age 63+/-9 years) with left ventricular dysfunction (radionuclide ventriculography mean ejection fraction, 34+/-11%) underwent both DSE and FDG-SPECT for myocardial viability. Viable myocardium was improvement from rest to low dose or worsening of wall motion at peak DSE and normal perfusion, mildly reduced perfusion with FDG uptake or severely reduced or absent perfusion with increased FDG uptake (mismatch) at FDG-SPECT. EPS, PSS velocities and EPS/PSS ratio during DSE were analysed using a six-segment model. Coronary revascularization bypass grafting was performed in 62 patients. All patients completed a long-term (9-year) follow-up for cardiac death. RESULTS: The segmental prevalence of severe dyssynergy was 77%. On a patient basis myocardial viability was detected by EPS/PSS ratio (31%), FDG-SPECT (34%) and DSE (26%). A significant improvement of Kaplan-Meier survival was predicted in viable compared with nonviable revascularized patients (P < 0.01). Both EPS/PSS ratio and FDG-SPECT, compared to DSE alone, tended to allocate more accurately univariate prediction of death-free outcome (odds ratio, 2.5 and 2.7 compared with 2.1). CONCLUSIONS: TDI adds objective variables to DSE, helping to recognize viable myocardium and optimize prediction of death-free outcome in long-term follow-up, with favorable comparison with nuclear techniques.

Cardiomyopathies↗

PET scanning and measuring the impact of treatment.

Positron emission tomography (PET) scanning with F18-fluorodeoxyglucose or FDG is a becoming a standard method for tumor staging. The prediction and evaluation of therapy response are newer applications of FDG-PET. PET often offers an early readout of treatment efficacy and is an attractive alternative to conventional anatomic assessments of treatment response. This article reviews the methods available with PET to monitor therapy response. Disease specific applications of PET imaging are then reviewed. While FDG is the most commonly used radiotracer for PET, many other radioligands could be applied in the future.

Fluorodeoxyglucose F18↗

Correlative imaging strategies implementing CT, MRI, and PET for staging of childhood Hodgkin disease.

BACKGROUND: The value of different correlative imaging strategies with F18-fluorodeoxyglucose positron emission tomography (FDG-PET) and conventional imaging modalities (CIM) for initial staging of pediatric Hodgkin disease (HD) was assessed. METHODS: Thirty-three patients (age, 4 to 18 y) with histologically proven HD underwent initial staging with computed tomography (thorax), magnetic resonance imaging (neck, abdomen, pelvis), and FDG-PET in a prospective study. Image fusion (PET-CIM) was performed using a semiautomatic voxel-based algorithm. Analysis of separate, side-by-side (SBS) and fused PET and CIM was performed evaluating 21 nodal and 6 extranodal regions per patient for presence of lymphoma, applying a 5-point confidence scale. The reference data was clinical follow-up (>12 mo). RESULTS: Concerning lymph node regions above and below the diaphragm the accuracy of CIM, PET, SBS, and image fusion was 86%, 89%, 94%, 97%, and 94%, 94%, 97%, 98%. In extranodal regions, the accuracy was 96%, 96%, 100%, and 100%. The reviewers' confidence was improved significantly by image fusion. Staging and therapy assignment on the basis of CIM was correctly modified by SBS in 5 and 4, by image fusion in 7 and 5 patients. CONCLUSIONS: Combined reading of FDG-PET and CIM is crucial for accurate staging in pediatric HD. Image fusion improves the observers' confidence and has impact on the therapeutic management.

Adolescent↗

The clinical impact of camera-based positron emission tomography imaging in patients with recurrent colorectal cancer.

RATIONALE AND OBJECTIVES: F18-fluorodeoxyglucose (FDG)-positron emission tomography (PET) studies have clinical value in suspected recurrent or metastatic colorectal cancer cases. Because this modality is not accessible for many patients, a camera-based FDG (CB-FDG) coincidence imaging was suggested as an alternative. Although inferior in resolution to a dedicated PET system, it can make FDG studies available to more patients. We assessed the clinical value of CB-FDG in patients with recurrent colorectal cancer. METHODS: The disease stage and treatment approach in 83 patients were twice determined by an oncologist and a surgeon, first based on the patient's records and blind to CB-FDG findings and then with the inclusion of FDG results in the decision-making analysis. RESULTS: On a lesion-based analysis, the sensitivity of CB-FDG was 95% and the specificity was 81% compared with 88% and 64%, respectively, for computed tomography. Adding FDG findings led to disease-stage alteration in 47 patients (57%), upstaging in 35 (42%), and downstaging in 12 (15%). FDG localized the tumor sites in 21 of 26 patients (81%) with suspected clinical recurrence and a negative conventional imaging workup. In 8 patients, FDG ruled out viable tumor tissue suggested by other modalities. The oncologist's suggested treatment approach was altered in 54% of the patients and the surgeon altered the decision on operability in 28%. CONCLUSION: CB-FDG assessment has clinical value for both staging and selecting treatment in patients with recurrent colorectal cancer and can be considered an alternative to an nonaccessible dedicated PET system.

Adult↗

[Cardiac hypertrophy and coronary reserve in endurance athletes].

Impaired coronary reserve (CR) with angiographic coronary arteries has been demonstrated in patients with left ventricular hypertrophy (LVH) in response to valvular heart disease or hypertension. To determine if adaptive LVH induced by intensive training may alter myocardial blood flow (MBF) and CR, 8 highly trained endurance tri- athletes (29.6 +/- 4.0 yrs, with echographic LVH) were compared with 6 control subjects (33.0 +/- 7.9 yrs, with a normal echographic examination). Triathletes entered the study if they had a left ventricular mass >120 g/m2 at 2-D echocardiographic measurements (mean = 148.6 +/- 19.8 g/m2). MBF was assessed using positron emission tomography (PET) with H2O15. Subjects underwent an intravenous bolus of 17- 25 mCi of H2)15 at baseline and after intravenous infusion of 0.80 mg/kg of dipyridimole; H2O15 examination was followed by an F18-fluorodeoxyglucose (FDG) myocardial imaging. CR was determined as the ration of maximal to basal myocardial blood flow. In comparison with controls, triathletes with LVH showed normal MBF values (0.74 +/- 0.1 vs 0.8 +/- 0.2 ml/ml/min, p = 0.2), but an increased CR (3.8 +/- 0.7 vs 6.1 +/-1.9, p < 0.05). In contrast with other forms of LVH, CR is not altered in LVH due intense physical training. These results suggest that LVH due to intensive physical training is associated with an increase in coronary blood flow capacity.

Adult↗

[Decrease in the frontal-superobasal metabolic ratio in unipolar depression].

Cerebral frontal glucose metabolism was investigated in 12 unipolar depressed patients and compared to these of 12 healthy volunteers using Positron Emission Tomography (PET) and (F18) fluorodeoxyglucose. The PET investigation was made in a quiet room with a dimly light and each subject remained in a resting state with closed eyes. Results show a decreased in a frontal superobasal calculated ratio in depressed patients compared to control subjects for left and for right values. This reduction indicates an imbalance between the frontal and the superobasal region. This imbalance could relate to some particular depressive symptom profile.

Adult↗

Relation between the kinetics of thallium-201 in myocardial scintigraphy and myocardial metabolism in patients with acute myocardial infarction.

OBJECTIVE: To investigate the relations between myocardial metabolism and the kinetics of thallium-201 in myocardial scintigraphy. METHODS: 46 patients within six weeks after the onset of acute myocardial infarction underwent resting myocardial dual isotope, single acquisition, single photon emission computed tomography (SPECT) using radioiodinated 15-iodophenyl 3-methyl pentadecaenoic acid (BMIPP) and thallium-201, exercise thallium-201 SPECT, and positron emission tomography (PET) using nitrogen-13 ammonia (NH3) and [F18]fluorodeoxyglucose (FDG) under fasting conditions. The left ventricle was divided into nine segments, and the severity of defects was assessed visually. RESULTS: In the resting SPECT, less BMIPP uptake than thallium-201 uptake was observed in all of 40 segments with reverse redistribution of thallium-201, and in 21 of 88 segments with a fixed defect of thallium-201 (p < 0.0001); and more FDG uptake than NH3 uptake (NH3-FDG mismatch) was observed in 35 of 40 segments with reverse redistribution and in 38 of 88 segments with fixed defect (p < 0.0001). Less BMIPP uptake in the resting SPECT was observed in 49 of 54 segments with slow stress redistribution in exercise SPECT, and in nine of 17 segments with rapid stress redistribution (p < 0.0005); NH3-FDG mismatch was observed in 42 of 54 segments with slow stress redistribution and in five of 17 segments with rapid stress redistribution (p < 0.0005). CONCLUSIONS: Thallium-201 myocardial scintigraphy provides information about not only myocardial perfusion and viability but also about myocardial metabolism in patients with acute myocardial infarction.

Adult↗

Doppler tissue velocity sampling improves diagnostic accuracy during dobutamine stress echocardiography for the assessment of viable myocardium in patients with severe left ventricular dysfunction.

BACKGROUND: Both nuclear imaging with F18-fluorodeoxyglucose and dobutamine stress echocardiography have been used to identify viable myocardium, although dobutamine-stress echocardiography has been demonstrated to be the less sensitive of the two. AIM: To compare the accuracy of pulsed-wave Doppler tissue sampling with dobutamine-stress echocardiography for the detection of viable myocardium, using F18-fluorodeoxyglucose imaging as a reference. Methods Forty patients with chronic coronary artery disease and left ventricular dysfunction (mean ejection fraction 33+/-11%), underwent F18-fluorodeoxyglucose imaging, dobutamine-stress echocardiography and pulsed-wave Doppler tissue sampling. Evaluation was performed using a six-segment model. RESULTS: Visual assessment by resting echo was feasible in 230 out of 240 segments (96%); 177 (77%) segments showed severe dyssynergy at rest. F18-fluorodeoxyglucose imaging showed viability in 95 (54%) segments while 82 (46%) were non-viable. Ejection phase velocity at rest was not significantly different; ejection velocities during low-dose and peak-dose dobutamine, however, were significantly higher in viable myocardium (8.6+/-2.9 vs 6.0+/-1.8 and 9.3+/-3.1 vs 6.2+/-2.1 cm x s(-1)). Using receiver operating characteristic curves the optimal cut-off value for viability assessment was an increase in the ejection phase velocity low-dose of 1+/-0.5 cm x s(-1), while 0+/-0.5 cm x s(-1)predicted non-viability. The sensitivity and specificity (95%CI) of pulsed-wave Doppler tissue sampling and dobutamine-stress echocardiography for the prediction of viability was respectively 87% (82-92) vs 75% (67-81) (P<0.05) and 52% (44-59) vs 51% (45-59) (P=ns). CONCLUSIONS: The sensitivity of pulsed-wave Doppler tissue sampling is superior to dobutamine-stress echocardiography for the assessment of myocardial viability.

Dobutamine↗

Agreement and disagreement between "metabolic viability" and "contractile reserve" in akinetic myocardium.

BACKGROUND: In patients with chronic coronary artery disease and depressed left ventricular function, assessment of residual viability in akinetic myocardium is important for therapeutic management. Intact perfusion, preserved metabolism, and presence of contractile reserve are different aspects of cellular viability. However, not all viable cells exhibit all characteristics; it is thought that contractile reserve is less often preserved compared with metabolic activity or intact perfusion. In this study we performed a direct comparison between perfusion imaging with thallium-201 single photon emission computed tomography (SPECT), metabolic imaging with F18-fluorodeoxyglucose SPECT, and assessment of contractile reserve with low-dose dobutamine echocardiography in akinetic myocardium. METHODS AND RESULTS: Forty patients with depressed left ventricular function (mean left ventricular ejection fraction 31% +/- 16%) were studied. Resting echocardiography showed akinesis in 165 (32%) segments. Most (n = 154, 93%) of these segments demonstrated resting hypoperfusion. F18-fluorodeoxyglucose imaging revealed a perfusion-metabolism mismatch in 41 segments and a match in 113 segments. Contractile reserve was present in 33 (80%) of the segments with a perfusion-metabolism mismatch and in 7 (6%) segments with a match (P < .0005). Of the 11 segments with normal perfusion, only 5 (45%) showed contractile reserve. The agreement between SPECT and dobutamine echocardiography was 87%. Although 94% of the segments that were nonviable on scintigraphy did not show contractile reserve, the disagreement between SPECT and dobutamine echocardiography was caused mainly by the absence of contractile reserve in 27% of the segments that were viable on scintigraphy. CONCLUSION: This study shows a good agreement between SPECT and dobutamine echocardiography, although a substantial number of segments with preserved viability on SPECT do not exhibit contractile reserve, indicating underestimation of viability by dobutamine echocardiography compared with F18-fluorodeoxyglucose imaging.

Coronary Disease↗

[Value of (F18)-2-fluorodeoxyglucose PET scanning in staging mouth cavity carcinoma. Comparative evaluation of PET findings before and after preoperative radiochemotherapy with histological and computerized tomography findings].

OBJECTIVE: The lack of sensitivity and specificity of conventional imaging techniques based on morphological critera is responsible for considerable limitations in the staging and surveillance of oral cancer. Therefore, this study investigates the contribution of [F18]-2-fluordesoxyglucose (FDG) positron emission tomography (PET) to tumor management with special regard to lymphnode involvement and therapeutic monitoring after radiotherapy. DESIGN: Prospective observational study. PATIENTS: Twenty-one patients with advanced oral cancer, predominantly T3/T4. INTERVENTION: FDG-PET scans before and after preoperative radio(chemo)therapy. Standardized uptake values (SUV) were determined for the tumor site and lymphnode areas. PET scans were correlated to histological findings after ablative tumor surgery. RESULTS: FDG-PET yielded superior sensitivity and specificity for tumor and lymphnode assessment. The effect of radiotherapy was reflected by the metabolic activity of the tumor, which shows a close correlation between the decrease of FDG uptake and histologic tumor regression. PET detected distant metastases and simultaneous tumors. CONCLUSION: FDG-PET is a challenging imaging technique with the potential to improve staging procedures for oral cancer. In the monitoring of metabolic activity of the tumor in the course of radio(chemo)therapy, FDG-PET allows objective measurement of the treatment response.

Aged↗

[Diagnosis of metastasis of malignant melanoma in the thyroid gland with f18-FDG PET scan].

Metastases in the thyroid gland are very rare. When they occur, long-term survival is dismal; thus an early diagnosis is critical. Malignant melanoma is one of the tumors which may metastasize to the thyroid gland. Therefore we wanted to demonstrate F18-Fluorodeoxyglucose-Positron emission tomography (F18-FDG-PET) is a sensitive and reliable method to identify such metastases. We report about a 51-year-old man, who had an inguinal lymph node metastasis of a malignant melanoma with unknown primary tumor site. He came to us for an a follow-up F18-FDG-PET investigation. In the PET there was a pathologic FDG-uptake in the left lobe of the thyroid gland. The nodule was removed and showed a malignant melanoma metastasis. This unusual scenario underscores the value of the PET in the oncologic follow-up of patients with malignant melanoma.

Diagnosis, Differential↗

Positron emission tomographic studies in restless legs syndrome.

We studied six restless legs syndrome (RLS) patients with [F18]fluorodeoxyglucose (FDG) positron emission tomography (PET). We also studied four of these same patients with [F18]fluorodopa (FDOPA) PET. The patients' FDG and FDOPA PET scans were compared with those from age-matched healthy control subjects. No significant differences between the two groups were found for any regional blood flow values derived from the FDG scans or for any binding constants derived from the FDOPA scans. These results suggest that any abnormal resting brain metabolic activity or putative presynaptic dopaminergic defect in RLS is likely either to be so subtle that it is below the threshold for ready detection by PET or that it is located in an area of neural tissue inaccessible to the current scanner. No substantial defect is likely to involve the dopaminergic nigrostriatal axis.

Aged↗

[SPECT tomography with F 18-fluorodeoxyglucose in a recent myocardial infarction clinical case].

We report a 50-year-old woman with a recent myocardial infarction in whom a myocardial perfusion single photon emission computed tomography (SPECT) with Thallium201 was done simultaneously with a F18-fluorodeoxyglucose (FDG) SPECT to study glucose metabolism. Myocardial infarction was located in the anteroseptal and apical regions and an echocardiography, done at the second day of evolution, showed a septo-apical hypokinesia. On the tenth day, a coronary angiography showed a critical lesion of the anterior descending coronary artery and an angioplasty with stent placement was performed on the next day. On the twelfth day, a resting, redistribution 201Tl SPECT to study viability and a FDG-SPECT with a dual head high-energy collimator camera were done. Images, acquired 45 min after injection, were analyzed visually. In anterior and medial apical sectors, discordance between flux and metabolism, considered a classical mismatch, was observed. Echocardiographic hypokinesia disappeared three month after revascularization.

Female↗

Diagnosis of a contralateral second testicular carcinoma by F18-FDG PET.

BACKGROUND: In testicular carcinoma the early diagnosis is very important because with an early therapy there are good chances for long-term survival (50-90%). Metastases of a testicular carcinoma are at first lymphogenous, hematogenous only in late stages. CASE REPORT: This is a case report about a 28-year-old man, whose testicular carcinoma (left testis) had already been operated on (unripe teratoma with parts of an embryonic carcinoma, an endodermal sinus tumor and a chorion carcinoma). Because of the elevated tumor marker AFP an FDG PET (F18-fluorodeoxyglucose positron emission tomography) investigation was made. CT (covering thorax, abdomen and pelvis) and ultrasound of the testis showed no pathological results. In the FDG PET a significant pathological FDG uptake in the right testis was found. Histology showed an unripe teratoma with parts of an embryonic carcinoma, an endodermal sinus tumor, and a chorion carcinoma. It was a second carcinoma of the contralateral testis. CONCLUSION: F18-FDG PET was a sensitive and reliable modality for diagnosis in this patient.

Adult↗

18-Fluorodeoxyglucose imaging with positron emission tomography and single photon emission computed tomography: cardiac applications.

The assessment of myocardial viability has become an important aspect of the diagnostic and prognostic work-up of patients with ischemic cardiomyopathy. Although revascularization may be considered in patients with extensive viable myocardium, patients with predominantly scar tissue should be treated medically or evaluated for heart transplantation. Among the many viability tests, noninvasive assessment of cardiac glucose use (as a marker of viable tissue) with F18-fluorodeoxyglucose (FDG) is considered the most accurate technique to detect viable myocardium. Cardiac FDG uptake has traditionally been imaged with positron emission tomography (PET). Clinical studies have shown that FDG-PET can accurately identify patients with viable myocardium that are likely to benefit from revascularization procedures, in terms of improvement of left ventricular (LV) function, alleviation of heart failure symptoms, and improvement of long-term prognosis. However, the restricted availability of PET equipment cannot meet the increasing demand for viability studies. As a consequence, much effort has been invested over the past years in the development of 511-keV collimators, enabling FDG imaging with single-photon emission computed tomography (SPECT). Because SPECT cameras are widely available, this approach may allow a more widespread use of FDG for the assessment of myocardial viability. Initial studies have directly compared FDG-SPECT with FDG-PET and consistently reported a good agreement for the assessment of myocardial viability between these 2 techniques. Additional studies have shown that FDG-SPECT can also predict improvement of LV function and heart failure symptoms after revascularization. Finally, recent developments, including coincidence imaging and attenuation correction, may further optimize cardiac FDG imaging (for the assessment of viability) without PET systems.

Coronary Disease↗

Initial assessment of positron emission tomography for detection of nonpalpable regional lymphatic metastases in melanoma.

BACKGROUND: The purpose of this pilot study is to determine the feasibility of positron emission tomography with fluorodeoxyglucose (FDG-PET) for detection of nonpalpable regional lymph node metastases in patients with melanoma. METHODS: Adult patients with histologically proven cutaneous melanoma planned to undergo surgical lymphadenectomy for treatment of nonpalpable subclinical or residual metastatic melanoma in regional lymph node basin(s) participated. Each patient underwent attenuation-corrected PET imaging of the regional lymph node basin(s) with F18 fluorodeoxyglucose (FDG) followed by complete surgical lymphadenectomy. FDG-PET scans were interpreted prospectively by an experienced nuclear medicine physician. FDG-PET scan interpretations and histologic results were then correlated. RESULTS: Eleven patients underwent 12 FDG-PET scans followed by 12 operations to clear 14 regional lymph node basins. FDG-PET correctly predicted the presence of metastatic melanoma in seven of seven surgical specimens. FDG-PET scans correctly predicted the absence of disease in seven of seven histologically negative node basins. Sensitivity was 1.0; specificity was 1.0. CONCLUSIONS: This study suggests that increased fluorodeoxyglucose uptake in palpably unremarkable regional lymph node basins in patients with melanoma is highly suggestive of metastatic disease.

Adult↗

[Positron-emission tomography in oncology].

This review analyses clinical results, new trends and recommendations of the leading medical centers concerning application of positron-emission tomography (PET) with F-18 fluorodeoxyglucose (F18 FDG) in cancer patients. This method of radionuclide visualization has been widely introduced for the last decade in diagnosis of cancer of unknown primary location, or CUP-syndrome, bronchogenic cancer of the lungs, cancer of the head and neck, malignant lymphoma and melanoma, colorectal and neuroendocrine cancer. Efficacy of this procedure, physiological grounds, performance are considered. Potentialities of F18 FDG PET are demonstrated in tumor screening, detection of metastases, recurrences after surgical, radiation or drug antitumor treatment or monitoring. In combination with CT, MRT, USI and other techniques, F18 FDG PET raises accuracy of the diagnosis of pathological changes at any stage of cancer with resulting improvement in further therapeutic and follow-up efficacy.

Colorectal Neoplasms↗