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FDG-PET is a sensitive but not specific test for myocardial sarcoidosis and its ability to define prognosis remains unclear. Combination with perfusion scanning may improve accuracy by differentiating scar from inflammation. We conducted this retrospective chart review to ascertain the utility of a rubidium -FDG PET scan for assessment of disease activity in patients with cardiac sarcoidosis. The presence of any perfusion-metabolism mismatch or a mismatch of > 6% of the myocardium on the scan were compared with the clinical course. Among 18 subjects, mismatched segments were present in 11 scans, whereas 7 demonstrated mismatch > 6%. There was a suggestion of association between PET scan and active disease using the threshold of any mismatch (p=0.09), with sensitivity of 80% and specificity of 62.5%. The threshold of >6% mismatch improved the specificity to 100% with 70% sensitivity, and the association between PET findings and clinically active disease was highly significant (p=0.0002). Eight patients had follow-up Rb-FDG PET scans, all of which were concordant with the clinical course. The positive predictive value of Rb-FDG PET scan showing >6% mismatch for detecting clinically active cardiac sarcoidosis was 100%. However, the finding of any mismatch still portends a high chance of clinical activity. Further studies to define the utility of Rb-FDG PET scan for management of cardiac sarcoidosis are warranted.

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Diagnosis of cardiac involvement in sarcoidosis is challenging and usually relies on a combination of clinical findings and imaging abnormalities. The case of a 53-yr-old female is described who presented with ventricular tachycardia and suspected angiosarcoma involving the right atrium and superior vena cava. A combination of magnetic resonance imaging and (18)F-2-fluoro-2-deoxyglucose-positron emission tomography were essential to the diagnosis of cardiac sarcoidosis. Reversibility of the disease was predicted more clearly by (18)F-2-fluoro-2-deoxyglucose-positron emission tomography than by magnetic resonance imaging, and clinical activity was predicted by persistent hypermetabolism on serial (18)F-2-fluoro-2-deoxyglucose-positron emission tomography.

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A 67-year-old man with progressive dysphagia was recently diagnosed with a gastroesophageal junction adenocarcinoma. Contrast-enhanced CT scans of the abdomen and pelvis reported a large GE junction tumor without evidence of metastatic disease. FDG positron emission tomography revealed intense tracer accumulation in the soft tissue mass at the GE junction consistent with the primary neoplasm. In addition, PET scan also identified a solitary focus of intense FDG accumulation at the musculotendinous junction of the right gluteus minimus muscle. Subsequent MRI demonstrated mild enhancement and could not differentiate between tumor versus inflammation. Needle biopsy was performed and confirmed metastatic esophageal adenocarcinoma. A case of skeletal muscle metastases from late-stage (IV) gastroesophageal adenocarcinoma was previously reported. However, a solitary metastasis to a distant skeletal muscle without evidence of other lymphatic and hematogenous metastasis is quite unusual. The case supports the previous report that PET is superior in detecting distant metastases for initial staging of esophageal carcinoma over CT.

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OBJECTIVES: The goal of this study was to determine the value of thallium201 single photon emission computed tomography (SPECT) imaging for prediction of all-cause mortality when considered along with functional capacity and heart rate recovery. BACKGROUND: Myocardial perfusion defects identified by thallium201 SPECT imaging are predictive of cardiac events. Functional capacity and heart rate recovery are exercise measures that also have prognostic implications. METHODS: We followed 7,163 consecutive adults referred for symptom-limited exercise thallium SPECT (mean age 60 +/- 10, 25% women) for 6.7 years. Using information theory, we identified a probable best model relating nuclear findings to outcome to calculate a prognostic nuclear score. RESULTS: There were 855 deaths. Intermediate- and high-risk prognostic nuclear scores were noted in 28% and 10% of patients. Compared with those with low-risk scans, patients with an intermediate-risk score were at increased risk for death (14% vs. 9%, hazard ratio: 1.67, 95% confidence interval [CI]: 1.44 to 1.95, p < 0.0001), while those with high-risk scores were at greater risk (24%, hazard ratio: 2.98, 95% CI: 2.49 to 3.56, p < 0.0001). In multivariable analyses that adjusted for clinical characteristics, functional capacity and heart rate recovery, an intermediate-risk nuclear score remained predictive of death (adjusted hazard ratio: 1.50, 95% CI: 1.28 to 1.76, p < 0.0001), as did a high-risk score (adjusted hazard ratio: 2.76, 95% CI: 2.13 to 2.56, p < 0.0001). Impaired functional capacity and decreased heart rate recovery provided additional prognostic information. CONCLUSIONS: Myocardial perfusion defects detected by thallium SPECT imaging are independently predictive of long-term all-cause death, even after accounting for exercise capacity, heart rate recovery and other potential confounders.

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The aims of this study were: (1) to measure noninvasively and near simultaneously myocardial blood flow, oxygen consumption, and contractile function and (2) to analyze myocardial energy expenditure and efficiency at rest and during dobutamine stress in normal humans. Dynamic and gated carbon-11 acetate positron emission tomography (PET) imaging was performed in 11 normal subjects. The initial uptake of (11)C-acetate was measured to estimate myocardial blood flow. Oxygen consumption was derived from the monoexponential slope of the (11)C-clearance curve recorded during myocardial washout. ECG-gated systolic and diastolic images were acquired during the peak myocardial (11)C activity to measure left ventricular radius, myocardial wall thickness, and long axis length. Myocardial oxygen consumption and parameters of cardiac geometry were used to determine myocardial energetics and cardiac efficiency by tension-area area analysis. Myocardial blood flow averaged 0. 8+/-0.06 ml min(-1) g(-1) at rest and 1.48+/-0.15 ml min(-1) g(-1) during dobutamine stress. Oxygen delivery and consumption were 151+/-13 and 88+/-15 microl O(2) min(-1) g(-1) at rest and increased to 291+/-31 and 216+/-31 microl O(2) min(-1) g(-1), respectively, during pharmacological stress (P<0.001). Oxygen extraction increased from 59%+/-8% at rest to 76%+/-9% during stress (P<0.001). Mechanical efficiency was 29%+/-6% at rest and 32%+/-6% during dobutamine stress (P=NS) while external work efficiency was 16%+/-6% at rest and increased to 21%+/-4% (P<0.01) during dobutamine stress. Stepwise linear regression analysis identified rate-pressure product and external cardiac work as major correlates of oxygen consumption. In summary, rapid dynamic and gated PET (11)C acetate imaging provides the unique capability to study noninvasively determinants of myocardial energy delivery, expenditure, and efficiency.

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BACKGROUND: Contrast echocardiography may be used to assess myocardial perfusion. However, gray scale assessment of myocardial contrast echocardiography (MCE) is difficult because of variations in regional backscatter intensity, difficulties in distinguishing varying shades of gray, and artifacts or attenuation. We sought to determine whether the assessment of rest myocardial perfusion by MCE could be improved with subtraction and color coding. METHODS AND RESULTS: MCE was performed in 31 patients with previous myocardial infarction with a 2nd generation agent (NC100100, Nycomed AS), using harmonic triggered or continuous imaging and gain settings were kept constant throughout the study. Digitized images were post processed by subtraction of baseline from contrast data and colorized to reflect the intensity of myocardial contrast. Gray scale MCE alone, MCE images combined with baseline and subtracted colorized images were scored independently using a 16 segment model. The presence and severity of myocardial contrast abnormalities were compared with perfusion defined by rest MIBI-SPECT. Segments that were not visualized by continuous (17%) or triggered imaging (14%) after color processing were excluded from further analysis. The specificity of gray scale MCE alone (56%) or MCE combined with baseline 2D (47%) was significantly enhanced by subtraction and color coding (76%, p<0.001) of triggered images. The accuracy of the gray scale approaches (respectively 52% and 47%) was increased to 70% (p<0.001). Similarly, for continuous images, the specificity of gray scale MCE with and without baseline comparison was 23% and 42% respectively, compared with 60% after post processing (p<0.001). The accuracy of colorized images (59%) was also significantly greater than gray scale MCE (43% and 29%, p<0.001). The sensitivity of MCE for both acquisitions was not altered by subtraction. CONCLUSION: Post-processing with subtraction and color coding significantly improves the accuracy and specificity of MCE for detection of perfusion defects.

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OBJECTIVES: Our purpose was to evaluate the long-term benefit of myocardial viability assessment for stratifying risk and selecting patients with low ejection fraction for coronary artery bypass grafting and to determine the relation between the severity of anginal symptoms, the amount of ischemic myocardium, and clinical outcome. METHODS: We studied 93 consecutive patients with severe coronary artery disease and low ejection fraction (median, 25%) who underwent positron emission tomography to delineate the extent of perfusion-metabolism mismatch (reflecting hibernating myocardium) for potential myocardial revascularization. Median follow-up was 4 years (range, 0 to 6.2 years). RESULTS: Fifty patients received medical therapy, and 43 patients underwent bypass grafting. In Cox survival models, heart failure class, prior myocardial infarction, and positron emission tomographic mismatch were the best predictors of survival. Patients with positron emission tomographic mismatch receiving bypass grafting had improved 4-year survival compared with those on medical therapy (75% versus 30%; P =.007) and a significant improvement in angina and heart failure symptoms. In patients without positron emission tomographic mismatch, bypass grafting tended to improve survival and symptoms only in those patients with severe angina (100% versus 60%; P =.085), whereas no survival advantage was apparent in patients with minimal or no anginal symptoms (63% versus 52%; P =.462). CONCLUSIONS: Patients with low ejection fraction and evidence of viable myocardium by positron emission tomography have improved survival and symptoms with coronary bypass grafting compared with medical therapy. In patients without evidence of viability, survival and symptom improvement with bypass grafting are apparent only among those patients with severe angina.

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BACKGROUND: Stress perfusion imaging can assess effectively the amount of jeopardized myocardium, but its use for identifying underperfused but viable myocardium has yielded variable results. We evaluated the relation between measurements of myocardial perfusion at rest and during pharmacologic stress and the patterns of tissue viability as determined by positron emission tomographic (PET) imaging. METHODS AND RESULTS: We studied 33 patients with coronary artery disease and left ventricular (LV) dysfunction (LV ejection fraction, 30%+/-8%). PET imaging was used to evaluate regional myocardial perfusion at rest and during pharmacologic stress with [13N]-ammonia as a flow tracer, and to delineate patterns of tissue viability (i.e., perfusion-metabolism mismatch or match) using [18F]-deoxyglucose (FDG). We analyzed 429 myocardial regions, of which 229 were dysfunctional at rest. Of these, 30 had normal perfusion and 199 were hypoperfused. A severe resting defect (deficit >40% below normal) predicted lack of significant tissue viability; 31 of 35 regions (89%) had a PET match pattern denoting transmural fibrosis. Although regions with mild or moderate resting defects (deficit <40% below normal) showed evidence of metabolic activity, perfusion measurements alone failed to identify regions with PET mismatch (reflecting hibernating myocardium). Reversible stress defects were observed with slightly higher frequency in regions with a PET mismatch (10 of 37) than in those with a PET match (36 of 162) pattern of viability. A reversible stress defect was a specific (78%) marker, but was a relatively insensitive marker (27%) of viable myocardium as defined by the PET mismatch pattern. CONCLUSIONS: In patients with LV dysfunction, the severity of regional contractile abnormalities correlates with the severity of flow deficit at rest. Severe reductions in resting blood flow in these dysfunctional regions identify predominantly nonviable myocardium that is unlikely to have improved function after revascularization. Although dysfunctional myocardium with mild to moderate flow reductions contains variable amounts of viable tissue (as assessed by FDG uptake), flow measurements alone do not distinguish between regions with PET mismatch (potentially reversible dysfunction) and PET match (irreversible dysfunction). The presence of an irreversible defect on stress imaging is a relatively specific (78%) marker of PET match, whereas a reversible stress defect is a rather insensitive (27%) marker of viability, as defined by the PET mismatch pattern.

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OBJECTIVES: We sought to assess the feasibility and accuracy of myocardial contrast echocardiography (MCE) using standard imaging approaches for the detection of perfusion defects in patients who had a myocardial infarction (MI). BACKGROUND: Myocardial contrast echocardiography may be more versatile than perfusion scintigraphy for identifying the presence and extent of perfusion defects after MI. However, its reliability in routine practice is unclear. METHODS: Fundamental or harmonic MCE was performed with continuous or triggered imaging in 203 patients with a previous MI using bolus doses of a perfluorocarbon-filled contrast agent (NC100100). All patients underwent single-photon emission computed tomography (SPECT) after the injection of technetium-99m (Tc-99m) sestamibi at rest. Quantitative and semiquantitative SPECT, wall motion and digitized echocardiographic data were interpreted independently. The accuracy of MCE was assessed for detection of segments and patients with moderate and severe sestamibi-SPECT defects, as well as for detection of patients with extensive perfusion defects (>12% of left ventricle). RESULTS: In segments with diagnostic MCE, the segmental sensitivity ranged from 14% to 65%, and the specificity varied from 78% to 95%, depending on the dose of contrast agent. Using both segment- and patient-based analysis, the greatest accuracy and proportion of interpretable images were obtained using harmonic imaging in the triggered mode. For the detection of extensive defects, the sensitivity varied from 13% to 48%, with specificity from 63% to 100%. Harmonic imaging remained the most accurate approach. Time since MI and SPECT defect location and intensity were all determinants of the MCE response. The extent of defects on MCE was less than the extent of either abnormal wall motion or SPECT abnormalities. The combination of wall motion and MCE assessment gave the best balance of sensitivity (46% to 55%) and specificity (82% to 83%). CONCLUSIONS: Although MCE is specific, it has limited sensitivity for detection of moderate or severe perfusion defects, and it underestimates the extent of SPECT defects. The best results are obtained by integration with wall motion. More sophisticated methods of acquisition and interpretation are needed to enhance the feasibility of this technique in routine practice.

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A woman with hydrocephalus due to aqueductal stenosis had functional imaging of cerebral perfusion and metabolism to demonstrate the effects of endoscopic third ventriculostomy--a new form of internal surgical shunting. Technetium-99m-ECD SPECT and 18F-FDG PET showed regional luxury perfusion at the left frontal region. Three months after a successful third ventriculostomy, a repeated imaging of cerebral perfusion and metabolism showed resolution of luxury perfusion and global improvement of both perfusion and metabolism. This concurred with postoperative clinical improvement. The paired imaging of cerebral perfusion and metabolism provides more information than just imaging perfusion or metabolism. Thus, the detection of perfusion and metabolism mismatch may open a new window of opportunity for surgical intervention.

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UNLABELLED: Multidetector SPECT systems equipped with a high-energy, or 511-keV collimator, have been proposed to offer a less expensive alternative to PET in myocardial viability studies with [18F]FDG. The objectives of this investigation included: (a) measuring the physical imaging characteristics of SPECT systems equipped with either a high-energy general-purpose collimator (HE), or the dedicated 511-keV collimator (UH), when imaging 511-keV photons, and comparing them with conventional FDG PET; and (b) directly and quantitatively comparing the diagnostic accuracy of SPECT, with either an UH or HE collimator, to that of PET in myocardial viability studies using 18F-FDG. METHODS: Physical imaging characteristics of SPECT and PET were measured and compared. Both SPECT and PET studies were performed in two groups of 18 patients each, with Group I using HE SPECT and Group II using UH SPECT. Myocardial perfusion studies were also performed using 82Rb PET at rest and during dipyridamole stress to identify areas of persistent hypoperfusion. For each myocardial region with a persistent perfusion defect, a perfusion-metabolism match or mismatch pattern was established independently, based on the results of 18F-FDG SPECT as well as PET. RESULTS: PET is superior to SPECT in all physical imaging characteristics, particularly in sensitivity and contrast resolution. PET had a sensitivity 40-80 times higher than that of SPECT, and its contrast resolution was 40-100% better than SPECT. Between FDG-SPECT using an HE collimator and that using a 511-keV collimator, the latter showed marked reduction in septal penetration (from 56% to 38%), improvement in spatial resolution (from 17 mm to 11 mm FWHM) as well as contrast resolution (from 34% to 45%), while suffering reduced system sensitivity (from 75 to 34 cpm/microCi). Patient studies demonstrated that although FDG-SPECT, using a HE or UH collimator, provided concordant viability information as FDG PET in a large majority of myocardial segments with persistent perfusion defects (88% and 90%, respectively), there is an excellent statistical agreement (kappa = 0.736) between SPECT with UH collimator and PET, while the agreement between SPECT using HE collimator and PET are moderate (kappa = 0.413). CONCLUSION: Despite its markedly inferior physical imaging characteristics compared with PET, SPECT with the dedicated 511-keV collimator offers a low-cost, practical alternative to PET in studying myocardial viability using [18F]FDG. SPECT systems with a high-energy, general-purpose collimator, on the other hand, are inadequate in such studies.

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Prospective delineation of viable from nonviable myocardium in patients with coronary artery disease in an important factor in deciding whether a patient should be revascularized or treated medically. Two common techniques--single-photon emission computed tomography (SPECT) and positron-emission computed tomography (PET)--are used in nuclear medicine using various radiopharmaceuticals for the detection of myocardial viability in patients. Thallium-201 (201Tl) and technetium-99m (99mTc)-sestamibi are the common radiopharmaceuticals used in different protocols using SPECT, whereas fluoride-18 (18F)-fluorodeoxyglucose (FDG) and rubidium-82 (82Rb) are most widely used in PET. The SPECT protocols involve stress/redistribution, stress/redistribution/reinjection, and rest/redistribution imaging techniques. Many studies have compared the results of 201Tl and (99mTc)-sestamibi SPECT with those of FDG PET; in some studies, concordant results have been found between delayed thallium and FDG results, indicating that 201Tl, although considered a perfusion agent, shows myocardial viability. Discordant results in a number of studies have been found between sestamibi and FDG, suggesting that the efficacy of sestamibi as a viability marker has yet to be established. Radiolabeled fatty acids such as iodine-123 (123I)-para-iodophenylpentadecanoic acid and carbon-11 (11C)-palmitic acid have been used for the assessment of myocardial viability with limited success. 11C-labeled acetate is a good marker of oxidative metabolism in the heart and has been used to predict the reversibility of wall motion abnormalities. (18F)-FDG is considered the marker of choice for myocardial viability, although variable results are obtained under different physiological conditions. Detection of myocardial viability can be greatly improved by developing new equipment and radiopharmaceuticals of better quality.

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In addition to providing useful clinical information, cardiac output determined during rubidium-82 positron emission tomographic (PET) myocardial perfusion studies can be used in the measurement of absolute regional myocardial blood flow using Sapirstein's method. This investigation was conducted to compare cardiac output values obtained by post-processing data acquired in a list mode PET myocardial perfusion study with those obtained using a technetium-99m-labeled red blood cell method on the same patients. Results from 14 patients showed that cardiac output can be accurately measured simultaneously in a 82Rb PET myocardial study, allowing determination of multiple perfusion and functional parameters of the heart, thus improving the cost-effectiveness of the 82Rb PET study.

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BACKGROUND: Although reversible perfusion defects, perfusion-metabolism mismatch and match patterns are important for differentiating viable from nonviable myocardium, the frequency of these scintigraphic patterns has not been reported. The study objective was to establish the incidence of these scintigraphic patterns to estimate the clinical need for metabolic positron emission tomography for evaluating tissue viability in patients with prior myocardial infarction (MI). METHODS AND RESULTS: 82Rb perfusion images were interpreted to identify reversible or irreversible defects, followed by determination of their 18F-fluorodeoxyglucose (18F-FDG) uptake pattern. In 155 patients with prior MI, analysis of 613 abnormal segments showed reversible perfusion defects in 13%. The 87% irreversible defects, 18% showed perfusion-metabolism mismatch, whereas 69% showed the match pattern. Reversible perfusion defects and perfusion-metabolism mismatches were noted in 20% (31/155) and 29% (45/155) of patients, respectively, whereas the match pattern was noted in 51% (79/155) of patients. CONCLUSION: Irreversible perfusion defects were common in our patients with prior MI, and distinction between viable and nonviable tissue was not possible by perfusion imaging alone. The identification of hibernating myocardium was possible only with the additional 18F-FDG imaging in about one third of patients. This indicates a significant clinical demand for 18F-FDG imaging that identifies patients who will benefit from revascularization.

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BACKGROUND: Studies of patients with coronary artery disease and left ventricular dysfunction have shown that preoperative quantification of myocardial viability may be clinically useful to identify those patients who will benefit most from revascularization both functionally and prognostically. However, the relation between preoperative extent of viability and change in heart failure symptoms has not been documented carefully. We assessed the relation between the magnitude of improvement in heart failure symptoms after coronary artery bypass surgery (CABG) and the extent of myocardial viability as assessed by use of quantitative analysis of preoperative positron emission tomography (PET) images. METHODS AND RESULTS: We studied 36 patients with ischemic cardiomyopathy (mean left ventricular ejection fraction, 28 +/- 6%) undergoing CABG. Preoperative extent and severity of perfusion abnormalities and myocardial viability (flow-metabolism mismatch) were assessed by use of quantitative analysis of PET images with 13N ammonia and fluorine-18-deoxyglucose. Each patient's functional status was determined before and after CABG by use of a Specific Activity Scale. Mean perfusion defect size and severity were 63 +/- 13% and 33 +/- 12%, respectively. Total extent of a PET mismatch correlated linearly and significantly with percent improvement in functional status after CABG (r = .87, P < .0001). A blood flow-metabolism mismatch > or = 18% was associated with a sensitivity of 76% and a specificity of 78% for predicting a change in functional status after revascularization. Patients with large mismatches (> or = 18%) achieved a significantly higher functional status compared with those with minimal or no PET mismatch (< 5%) (5.7 +/- 0.8 versus 4.9 +/- 0.7 metabolic equivalents, P = .009). This resulted in an improvement of 107% in patients with large mismatches compared with only 34% in patients with minimal or no PET mismatch. CONCLUSIONS: In patients with ischemic cardiomyopathy, the magnitude of improvement in heart failure symptoms after CABG is related to the preoperative extent and magnitude of myocardial viability as assessed by use of PET imaging. Patients with large perfusion-metabolism mismatches exhibit the greatest clinical benefit after CABG.

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BACKGROUND: Cigarette smoking is a major preventable risk factor for coronary artery disease and sudden cardiac death. However, the effect of acute and long-term cigarette smoking on coronary vasodilatory capacity and myocardial flow reserve has not been quantified in humans. METHODS AND RESULTS: To examine the effect of short-term and long-term smoking, myocardial blood flow was quantified at rest and during dipyridamole-induced hyperemia (0.56 mg/kg) in 12 smokers (10 males and 2 females; mean age, 27 +/- 4 years) under baseline conditions (reflecting the effect of long-term smoking) and during short-term cigarette smoking with 13N ammonia, positron emission tomography, and a two-compartment model. Twelve sex- and age-matched nonsmokers served as control subjects. Smoking significantly increased the rate-pressure product at rest from 7525 +/- 1290 to 9160 +/- 1125 (P < .001 versus baseline), which was paralleled by a proportional increase in myocardial blood flow at rest (0.70 +/- 0.17 versus 0.88 +/- 0.17 mL.g-1.min-1; P < .05 versus baseline). In contrast, hyperemic blood flow declined from 2.23 +/- 0.35 at baseline (P = NS versus control) to 1.98 +/- 0.32 mL.g-1.min-1 during smoking (P < .01 versus baseline). Accordingly, the myocardial flow reserve declined from 3.36 +/- 0.83 in smokers at baseline to only 2.28 +/- 0.28 during smoking (P < .0001 versus baseline). Thus, myocardial blood flow and flow reserve were similar in young, long-term smokers and young, healthy nonsmokers. CONCLUSIONS: Short-term smoking increases the coronary vasomotor tone during dipyridamole-induced hyperemia and markedly reduces the myocardial flow reserve. In contrast, long-term smoking does not attenuate the coronary vasodilatory capacity in young individuals with a relatively short smoking history. It might be speculated that the short-term reduction in the coronary vasodilatory capacity during smoking could lower the ischemic threshold in smokers with coronary artery disease and contribute to the increased risk for sudden cardiac death.

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In a retrospective study of ductal carcinoma in situ (DCIS) of the breast, the expression of the neu oncogene was determined immunohistochemically in 76 women treated by local excision or mastectomy. The histopathological features, including the extent of the lesion, histological subtype, cell type, and number of mitoses, were related to neu overexpression. Immunopositivity was found only in DCIS of large cell type, where it correlated with extent of disease but not with mitotic rate. Our findings, together with previous experimental evidence, suggest that this relationship is a consequence of the effect of the neu protein on cell motility.

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In dynamic cardiac PET FDG studies for measurement of myocardial metabolic rate of glucose (MMRGlc), the plasma FDG time-activity curve (input function) is commonly obtained from the left ventricular (LV) region on the PET images. The input function is contaminated by spillover of radioactivity from the surrounding myocardium and this could cause significant error in the estimated MMRGlc. In this study, we determined the effect of myocardial to blood pool spillover on MMRGlc and developed a method to correct for this spillover of activity. The method is based on a reformulation of the FDG model equation in terms of the spillover contaminated input function that includes both the myocardium to blood pool and blood pool to myocardium spillover fractions as variable parameters (Fmb and Fbm). The reformulated model equation can be used to fit the global myocardial tissue activity curve to estimate Fmb and thus yields a spillover corrected input function. The MMRGlc estimate with the corrected input function was within 95% of the true value (compared to 85% using the uncorrected input function) in a set of computer simulation studies. Dynamic PET FDG data were obtained in eight human studies and blood samples were obtained during the study. As compared to the results with the uncorrected input function, the estimates of k4 by the new method were reduced by 69% into a range consistent with in vitro results. The method is effective in correcting Fmb spillover and leads to more accurate estimates of MMRGlc. The method also allows larger regions of interest (up to 150 mm2) to be drawn over the LV in dynamic PET images, thereby reducing the noise level in the input function.

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