缺血心肌动物模型PET和SPECT显像及组织学对比研究

目的评估^201TI SPECT及^18F-脱氧葡萄糖（FDG）PET显像对模型猪心肌活力的鉴别。方法健康家猪12头，其中10头于冠状动脉左旋支起始处放置Ameriod环，饲养28d形成慢性心肌缺血动物模型（另2头作正常对照），行^201TI SPECT心肌灌注显像和^18F—FDG PET心肌代谢显像并与HE染色病理学改变进行比较。结果81个心肌节段中，^18F—FDG心肌显像示心肌有活力的节段为73个（90．1％），明显高于^201TI心肌显像所示的62个（76．5％），差异有显著性（P〈0．05）。HE染色结果示有心肌活力的节段为74个（91．3％），与^18F—FDG心肌显像所示结果差异无显著性（P〉0．05）。结论^18F—FDGPET心肌显像检测心肌活力的准确性明显高于^201TI SPECT心肌显像。     

Acute myocardial infarction: evaluation with first-pass enhancement and delayed enhancement MR imaging compared with 201Tl SPECT imaging

PURPOSE: To evaluate acute myocardial infarction by using first-pass enhancement (FPE) and delayed enhancement (DE) magnetic resonance (MR) imaging compared with thallium 201 ((201)Tl) single photon emission computed tomography (SPECT). MATERIALS AND METHODS: Contrast material-enhanced FPE MR, inversion-recovery DE MR, and rest-redistribution (201)Tl SPECT images were obtained in 60 consecutive patients (53 men, seven women; mean age [+/- SD], 56 years +/- 13; range, 30-78 years) at 6 days +/- 3 after reperfused first myocardial infarction. Presence of microvascular obstruction was determined on FPE MR images. Infarct size was defined on DE MR images as percentage of left ventricular (LV) area and compared with uptake defect on redistribution (201)Tl SPECT images. Differences in continuous data were analyzed with Student t test. Linear regression and Bland-Altman analysis were used to compare measurements of infarct size. RESULTS: Mean infarct size was not significantly different between DE MR imaging (20.7% +/- 11.5% of LV area) and (201)Tl SPECT (19.4% +/- 14.3% of LV area; P =.26); good correlation (r = 0.73; P <.001) and agreement were found, with a mean difference of +1.3% +/- 9.8% of LV area. (201)Tl SPECT failed to depict infarct in six (20%) of 30 patients with inferior myocardial infarction (mean size, 6.4% +/- 5.7% of LV area on DE MR images), whereas DE MR images showed the infarct in all patients (P <.01). FPE MR images depicted microvascular obstruction in 23 (38%) of 60 patients; these patients had larger infarctions at DE MR imaging than did patients without microvascular obstruction (30.4% +/- 9.0% vs 15.1% +/- 8.4% of LV area, P <.001). (201)Tl SPECT showed larger infarcts in patients with microvascular obstruction (26.7% +/- 16.2% vs 15.0% +/- 11.2% of LV area, P <.01). CONCLUSION: Good correlation and agreement with (201)Tl SPECT indicate DE MR imaging may be used to estimate infarct size 6 days after reperfused acute myocardial infarction. DE MR imaging is more sensitive for detection of inferior infarction than is (201)Tl SPECT. Patients with microvascular obstruction on FPE MR images have larger infarcts.     

Evaluation of myocardial viability following acute myocardial infarctic using201Tl SPECT after thallium-glucose-insulin infusion —Comparison with18F-FDG positron emission tomography—

OBJECTIVE AND METHODS: The aim of this study was to evaluate myocardial viability in patients after acute myocardial infarction (AMI). We compared 201Tl SPECT after 201Tl with GIK (10% glucose 250 ml, insulin 5 U and KCl 10 mEq) infusion (GIK-201Tl) with resting 201Tl and 99mTc-pyrophosphate (PYP) dual SPECT, positron emission computed tomography (PET) using 18F-fluorodeoxyglucose (18F-FDG) in 21 patients with their first AMI, who all underwent successful reperfusion. GIK-201Tl SPECT, 201Tl and 99mTc-PYP dual SPECT were done within 10 days after admission and 18F-FDG-PET was performed at 3 weeks. GIK-201Tl SPECT was obtained after 30 min of GIK-201Tl infusion. 18F-FDG (370 MBq) was injected intravenously after oral glucose (1 g/ kg) loading, and then PET was obtained. PET and SPECT images were divided into 20 segments. Regional tracer uptake was scored using a 4-point scoring system (3 = normal to 0 = defect), and summed to a regional uptake score (RUS). Regional area means the infarcted area in which 99mTc-PYP accumulated. The number of decreased uptake segments (ES) was then determined. The infarcted area was defined as the area of 99mTc-PYP uptake. RESULTS: The ESs for the GIK-201Tl and 18F-FDG-PET images were significantly lower than the number of 99mTc-PYP uptake segments. The RUS for GIK-201Tl was higher than that for resting-201Tl imaging and similar to those for 18F-FDG-PET. CONCLUSIONS: In the detection of myocardial viability following AMI, GIK-201Tl imaging is useful with findings similar to those of 18F-FDG-PET.     

201Tl与13N-NH3、18F-FDG PET心肌显像判断存活心肌的对比研究

目的　比较再注射2 0 1T1心肌显像与联合应用13 N NH3 及18F 脱氧葡萄糖 (FDG)心肌PET显像判断存活心肌的临床价值。方法　 2 0例心肌梗死患者 ,行2 0 1T1SPECT负荷、再分布、再注射显像及13 N NH3 、18F FDGPET心肌显像。将左室分成 9个节段 ,以视觉评价法对放射性分布进行 4级评分。获得2 0 1T1SPECT再分布、再注射像及18F FDGPET显像的局部心肌摄取率 (%ID)。结果　PET判定为存活心肌的 48个节段中 ,45个节段 (93.8% ) 2 0 1T1再注射像也判定为存活心肌。在2 0 1T1再分布像示放射性分布严重低下的 2 4个节段 ,2 0 1T1再注射像与PET显像判定存活心肌的一致率为 87.5 % ,其中 37.5 %为存活心肌节段 ,5 0 %为无存活心肌节段。 2种显像方法的 %ID无明显差异 ,且呈显著正相关 (r=0 .72 2 )。结论　再注射2 0 1T1心肌显像判断存活心肌的准确性与PET心肌显像相似 ,有较大的临床应用价值。     

Clinical outcome of patients with previous myocardial infarction and left ventricular dysfunction assessed with myocardial (99m)Tc-MIBI SPECT and (18)F-FDG PET.

Myocardial viability was assessed by (99m)Tc-methoxyisobutylisonitrile (MIBI) SPECT and (18)F-FDG PET to evaluate the prognosis and treatment strategy of patients with myocardial infarction (MI) and left ventricular (LV) dysfunction. METHODS: One hundred twenty-three consecutive patients with previous MI and LV dysfunction (LV ejection fraction [EF], 35% +/- 6% [mean +/- SD]) who underwent (99m)Tc-MIBI SPECT and FDG PET were followed-up for 26 +/- 10 mo (mean +/- SD). Distributions of the 2 radiotracers in myocardial segments were classified into 2 patterns: myocardial perfusion-metabolism mismatch (MM) and match (M). LV EF and LV end-diastolic diameter (EDD) were measured by echocardiography at baseline, 3 mo (Pos1), and 6 mo (Pos2) after revascularization. Cardiac death, acute MI, unstable angina, and late revascularization (>3 mo) experienced by the patients during follow-up were defined as cardiac events. RESULTS: Sixty-seven patients underwent revascularization and 56 patients were treated medically. Of the 72 patients with > or =2 MM segments, 42 underwent revascularization (group A1) and 30 were treated medically (group A2). Of the 51 patients with <2 MM segments, 25 underwent revascularization (group B1) and 26 were treated medically (group B2). The 4 groups had similar baseline characteristics and rest LV EF. After revascularization, EF (mean +/- SD) increased in group A1 from 36% +/- 5% to 44% +/- 8% (P < 0.0001) in Pos1 and to 51% +/- 9% (P < 0.0001) in Pos2. EDD (mean +/- SD) decreased from 62 +/- 8 mm to 56 +/- 5 mm (P < 0.001) in Pos1 and to 55 +/- 5 mm (P < 0.001) in Pos2. However, EF and EDD were unchanged in group B1 (P > 0.05). During the follow-up, 22 patients (17.9%) suffered from cardiac events, including 11 cardiac deaths, 4 acute MI, 6 late coronary artery bypass grafting, and 1 unstable angina pectoris. The cardiac event rate in group A2 (50%) was significantly higher than that of groups A1 (2.4%; chi(2) = 23.08; P < 0.0001), B1 (12%; chi(2) = 8.94; P = 0.003), and B2 (11.5%; chi(2) = 9.45; P = 0.002). CONCLUSION: Assessment of myocardial viability using hybrid (99m)Tc-MIBI SPECT and FDG PET can predict the clinical outcome and is helpful to decision making in the treatment strategy of patients with MI and LV dysfunction. Revascularization can improve the LV function and clinical outcome of patients with >2 viable myocardial segments.     

Electromechanical properties of perfusion/metabolism mismatch: comparison of nonfluoroscopic electroanatomic mapping with 18F-FDG PET.

The aim of this study was to compare nonfluoroscopic electroanatomic mapping (NOGA), SPECT perfusion imaging, and PET metabolic imaging for assessment of myocardial viability. In particular, we sought to elucidate differences of electromechanical properties between the perfusion/metabolism mismatch as an indicator of a potentially reversible ischemic injury and the perfusion/metabolism match indicating irreversibly damaged myocardial tissue. METHODS: Twenty-one patients with coronary artery disease underwent NOGA mapping of endocardial unipolar voltage, cardiac 18F-FDG PET of glucose utilization, and resting 201Tl SPECT of myocardial perfusion. RESULTS: Electrical activity was 10.8 +/- 4.6 mV (mean +/- SD) in normal myocardium and was unchanged in hypoperfused segments with maintained glucose metabolism (perfusion/metabolism mismatch), 9.3 +/- 3.4 mV (P = not significant). In contrast, hypoperfused segments with a perfusion/metabolism match and nonviable segments showed significantly lower voltage (6.9 +/- 3.1 mV, P < 0.0001 and 4.1 +/- 1.1 mV, P < 0.0001 vs. normal). In hypoperfused segments, metabolic activity was more closely related to endocardial voltage than was myocardial perfusion (201Tl vs. voltage: r = 0.38, SEE = 3.2, P < 0.001; 18F-FDG PET vs. voltage: r = 0.6, SEE = 2.8, P < 0.0001). CONCLUSION: In hypoperfused myocardium, electrical activity by NOGA mapping is more closely related to PET metabolic activity than to SPECT myocardial perfusion. As NOGA mapping does not differentiate hypoperfused myocardium with enhanced glucose utilization from normal myocardium, results from NOGA mapping need to be correlated with results from perfusion imaging to identify hypoperfused, yet viable, myocardium and to stratify patients for revascularization procedures.     

Sequential (201)Tl imaging and dobutamine echocardiography to enhance accuracy of predicting improved left ventricular ejection fraction after revascularization.

201Tl imaging and dobutamine echocardiography (DE) can both identify viable myocardium. Prediction of functional outcome after revascularization remains suboptimal with either technique because of the relatively low specificity of (201)Tl and low sensitivity of DE. This study was undertaken to develop an optimal testing strategy for prediction of post-revascularization functional outcome. METHODS: Seventy-three patients (mean [+/-SD] left ventricular ejection fraction [LVEF], 32% +/- 8%) underwent DE and resting (201)Tl SPECT (4-h delayed imaging) before surgical revascularization. Dysfunctional segments with (201)Tl activity > or = 50% or with contractile reserve were considered viable. LVEF was assessed before and 3-6 mo after revascularization. RESULTS: Analysis of receiver operator characteristic curves showed that the optimum criteria to predict improvement (> or = 5%) in LVEF after revascularization were > or = 6 viable dysfunctional segments (using a 16-segment model) on (201)Tl and > or = 4 segments on DE. Sensitivity and specificity were 84% and 63% for (201)Tl (P < 0.05 vs. DE) and 63% and 85% for DE (P < 0.05 vs. (201)Tl). Changing the (201)Tl criteria to improve specificity to 78% (> or = 8 segments) yielded a low sensitivity of 44%, and changing the DE criteria to improve sensitivity to 84% (> or = 2 segments) lowered specificity to 56%. Two sequential testing strategies were explored to achieve optimal sensitivity and specificity. In strategy 1, 33 (45%) of 73 patients with an intermediate likelihood of viability by (201)Tl (5-8 viable segments) underwent DE. In strategy 2, 31 (42%) of 73 patients with an intermediate likelihood of viability by DE (2-4 viable segments) underwent (201)Tl. For strategy 1, sensitivity did not change significantly (69%), whereas specificity was improved significantly (93%, P < 0.01 vs. (201)Tl). For strategy 2, sensitivity improved significantly (78%, P < 0.05 vs. DE) and specificity remained unchanged (80%). CONCLUSION: Sequential testing by (201)Tl SPECT and DE in a subgroup of patients with an intermediate likelihood of viability by either test significantly enhanced prediction of post-revascularization improvement of LVEF.     

An assessment of wall motion, perfusion and glucose metabolism in recent myocardial infarction: a comparison in patients with and without revascularization

The aim of this study was to compare the extent and severity of wall motion abnormalities, perfusion and glucose metabolism, in recent myocardial infarction in patients with and without revascularization. Forty-nine patients were studied (82% men; mean age 58 years) by using echocardiography, 201Tl single photon emission computed tomography (SPECT) rest and redistribution, and 2-[18F]fluoro-2-deoxy-D-glucose (18F-FDG) SPECT at a mean of 9.2 days (range, 1-24 days) after myocardial infarction. Twenty-seven of the 49 patients underwent revascularization while the other 22 received medical therapy before echocardiography and studies using radionuclides. A contrast angiogram was obtained for each patient. A follow-up echocardiogram at 3 months was obtained for 44 patients. Images were read blindly, using a 17 segment model, with semi-quantitative analysis. In the whole group, the extent of hypokinesia was 15%+/-14 (mean+/-SD); the extent of mild defects was determined as 5%+/-6 by using 201Tl at rest, 6%+/-9 by using 201Tl redistribution, and 4%+/-6 by using 18F-FDG (P<0.0005, echocardiogram/radionuclides). Echocardiography showed that the extent of akinesia-dyskinesia was 16%+/-18 in revascularized patients and 28%+/-18 in non-revascularized patients (P=0.017). With regard to moderate and severe defects, 201Tl rest showed 19%+/-16 and 28%+/-17, respectively (P=0.047); 201Tl redistribution 17%+/-15 and 26%+/-15, respectively (P=0.043); and 18F-FDG 17%+/-13 and 24%+/-15, respectively (NS). In echocardiography, the extent of hypokinetic segments decreased from 16%+/-15 at baseline to 10%+/-11 at 3 months (P=0.045), in revascularized patients. It is concluded that, in recent myocardial infarction, hypokinesia extent on echocardiogram is greater than mild perfusion or metabolic defect extent, reflecting stunning and so the use of radionuclide techniques appear more accurate for defining the extent of myocardial infarction. Non-revascularized patients showed a significantly greater extent of akinesia-dyskinesia and moderate-severe perfusion defects than did revascularized patients, which can be considered a result of therapy. It is suggested that 201Tl rest perfusion be used for the assessment of myocardial infarction soon after revascularization.     

The predictive value of<Superscript>201</Superscript>Tl rest-redistribution and<Superscript>18</Superscript>F-fluorodeoxyglucose SPECT for wall motion recovery after recent reperfused myocardial infarction

201Tl and 18F-FDG are useful for acute myocardial infarction (MI) assessment. The goal of this study was to compare their predictive value for wall motion recovery in the culprit area after a recent reperfused MI using SPECT technique. METHODS: Forty-one patients (mean age: 56 +/- 12 years) were included, 81% of them male; all were studied within 1-24 days post MI. They underwent angioplasty in 27 cases (12 primary); bypass grafting in 10 cases and successful thrombolysis in 4. SPECT 201Tl injected at rest and redistribution (R-R) and also 18F-FDG, were performed on different days. Processed tomograms were interpreted blinded to clinical or angiographic data. Segmental wall motion assessed with echocardiography at baseline was compared with the 3 month follow up. RESULTS: Sensitivity [Confidence Interval] for 201Tl R-R was 74.6% [60.5-84.5], for FDG it was 82.1% [70.8-90.4]; specificities were 73% [64.3-80.5] and 54.8% [45.6-63.7], respectively. 18F-FDG tended to be more sensitive than 201Tl R-R, but the latter was more specific (p < 0.0004). Both 201Tl RR and 18F-FDG presented high negative predictive value (p: ns). CONCLUSION: In recent MI, SPECT 201Tl R-R is a valuable and widely available technique for viability detection, with similar sensitivity and significant better specificity than SPECT 18F-FDG.     

探测心肌活力的技术进展

心肌活力的评估十分重要,它有助于了解心肌病变患者的预后和选择治疗方式。评估心肌活力的方法包括核医学和其他临床上常见的方法,其中核医学上的方法有18F-FDG PET、18F-FDG SPECT、201Tl SPECT、99Tcm-MIBI SPECT和脂肪酸显像,其他显像技术包括多巴酚丁胺负荷超声,MRI(核磁共振显像)等。     

Usefulness of fasting 18F-FDG PET in identification of cardiac sarcoidosis.

Cardiac PET using (18)F-FDG under fasting conditions (fasting (18)F-FDG PET) is a promising technique for identification of cardiac sarcoidosis and assessment of disease activity. The aim of this study was to investigate the usefulness of fasting (18)F-FDG PET in detecting inflammatory lesions of cardiac sarcoidosis from a pathophysiologic standpoint. METHODS: Twenty-two patients with systemic sarcoidosis were classified into 2 groups of 11 each according to the presence or absence of sarcoid heart disease. Cardiac sarcoidosis was diagnosed according to the Japanese Ministry of Health and Welfare guidelines for diagnosing cardiac sarcoidosis with the exception of scintigraphic criteria. Nuclear cardiac imaging with fasting (18)F-FDG PET, (99m)Tc-methoxyisobutylisonitrile ((99m)Tc-MIBI) SPECT, and (67)Ga scintigraphy were performed in all patients. PET and SPECT images were divided into 13 myocardial segments and the standardized uptake value (SUV) of (18)F-FDG was calculated and defect scores (DS) for (99m)Tc-MIBI uptake were assessed for each segment. The total SUV (T-SUV) and total DS (TDS) were calculated as the sum of measurements for all 13 segments, and the diagnostic accuracy of fasting (18)F-FDG PET was compared with that of the other nuclear imaging modalities. In addition, pathophysiologic relationships between inflammatory activity and myocardial damage were examined by segmental comparative study using the SUV and DS. RESULTS: In patients with cardiac sarcoidosis, fasting (18)F-FDG PET revealed a higher frequency of abnormal myocardial segments than (99m)Tc-MIBI SPECT (mean number of abnormal segments per patient: 6.6 +/- 3.0 vs. 3.0 +/- 3.2 [mean +/- SD], P < 0.05). The sensitivity of fasting (18)F-FDG PET in detecting cardiac sarcoidosis was 100%, significantly higher than that of (99m)Tc-MIBI SPECT (63.6%) or (67)Ga scintigraphy (36.3%). The accuracy of fasting (18)F-FDG PET was significantly higher than (67)Ga scintigraphy. The T-SUV demonstrated a good linear correlation with serum angiotensin-converting enzyme levels (r = 0.83, P < 0.01), and the TDS showed a significant negative correlation with the left ventricular ejection fraction (r = -0.82, P < 0.01). In abnormal myocardial segments on the nuclear scan, the SUV showed a significant negative correlation with the DS (r = -0.63, P < 0.0001). CONCLUSION: This study suggests that fasting (18)F-FDG PET can detect the early stage of cardiac sarcoidosis, in which fewer perfusion abnormalities and high inflammatory activity are noted, before advanced myocardial impairment.     

201Tl and 99mTc-MIBI gated SPECT in patients with large perfusion defects and left ventricular dysfunction: comparison with equilibrium radionuclide angiography.

Left ventricular ejection fraction (LVEF) is a major prognostic factor in coronary artery disease and may be computed by 99mTc-methoxyisobutyl isonitrile (MIBI) gated SPECT. However, 201Tl remains widely used for assessing myocardial perfusion and viability. Therefore, we evaluated the feasibility and accuracy of both 99mTc-MIBI and 201Tl gated SPECT in assessing LVEF in patients with myocardial infarction, large perfusion defects and left ventricular (LV) dysfunction. METHODS: Fifty consecutive patients (43 men, 7 women; mean age 61 +/- 17 y) with a history of myocardial infarction (anterior, 26; inferior, 18; lateral, 6) were studied. All patients underwent equilibnum radionuclide angiography (ERNA) and rest myocardial gated SPECT, either 1 h after the injection of 1110 MBq 99mTc-MIBI (n = 19, group 1) or 4 h after the injection of 185-203 MBq 201Tl (n = 31, group 2) using a 90 degrees dual-head camera. After filtered backprojection (Butterworth filter: order 5, cutoff 0.25 99mTc or 0.20 201Tl), LVEF was calculated from reconstructed gated SPECT with a previously validated semiautomatic commercially available software quantitative gated SPECT (QGS). Perfusion defects were expressed as a percentage of the whole myocardium planimetered by bull's-eye polar map of composite nongated SPECT. RESULTS: Gated SPECT image quality was considered suitable for LVEF measurement in all patients. Mean perfusion defects were 36% +/- 18% (group 1), 33% +/- 17% (group 2), 34% +/- 17% (group 1 + group 2). LVEF was underestimated using gated SPECT compared with ERNA (34% +/- 12% and 39% +/- 12%, respectively; P = 0.0001). Correlations were high (group 1, r= 0.88; group 2, r = 0.76; group 1 + group 2, r = 0.82), and Bland-Altman plots showed a fair agreement between gated SPECT and ERNA. The difference between the two methods did not vary as LVEF, perfusion defect size or seventy increased or when the mitral valve plane was involved in the defect. CONCLUSION: LVEF measurement is feasible using myocardial gated SPECT with the QGS method in patients with large perfusion defects and LV dysfunction. However, both 201Tl and 99mTc-MIBI gated SPECT similarly and significantly underestimated LVEF in patients with LV dysfunction and large perfusion defects.     

Prediction of functional recovery after coronary bypass surgery using quantitative gated myocardial perfusion SPECT

Previous studies have demonstrated that myocardial perfusion imaging using 99mTc-tetrofosmin at rest allows viability assessment similar to that obtained with 201Tl imaging and 18F-fluorodeoxyglucose positron emission tomography (18F-FDG PET). The simultaneous assessment of perfusion and regional function is now available by quantitative gated myocardial perfusion single-photon emission computed tomography (SPECT). This study was designed to evaluate the utility of quantitative values of wall motion and wall thickening, calculated by quantitative gated myocardial perfusion SPECT, for the prediction of functional recovery after coronary bypass grafting (CABG). Fifty-six patients with coronary artery disease scheduled for CABG were included prospectively. All patients underwent 99mTc-tetrofosmin gated SPECT imaging at rest preoperatively and 3 months after CABG. The myocardium was divided into nine segments and the average quantitative values of regional perfusion (percentage uptake) (%), wall motion (mm) and wall thickening (%) were determined automatically using quantitative gated SPECT (QGS) software. The wall motion score was defined visually using a four-point scale (0, normal; 3, akinesis), and segments with severe asynergy (score of 2 or 3) with patent grafts were assessed. Of 77 segments with severe asynergy, 56 segments showed improved wall motion and 21 segments did not improve after CABG. The area under the receiver operating characteristic curve of wall thickening for the prediction of functional recovery was significantly higher (0.92) than that of the percentage uptake (0.77, P<0.017) or wall motion (0.60, P<0.0001). When each analysis used the optimal threshold, the wall thickening analysis (>or=10%) had a sensitivity of 95% and a specificity of 81%. These values tended to be higher than those of the percentage uptake (sensitivity, 86%; specificity, 67%). The wall motion analysis (>or=1.5 mm) had a significantly lower sensitivity of 75% and specificity of 43% than the wall thickening analysis (P=0.0038 and P=0.011, respectively). The results indicate that wall thickening, calculated by QGS software, may be more useful than regional perfusion or wall motion analysis for the prediction of functional recovery after CABG. The areas of asynergy with relatively preserved wall thickening may have the potential for improved function despite severely decreased perfusion.     

18F-FDG accumulation with PET for differentiation between benign and malignant lesions in the thorax.

Recent reports have indicated the value and limitations of (18)F-FDG PET and (201)Tl SPECT for determination of malignancy. We prospectively assessed and compared the usefulness of these scintigraphic examinations as well as (18)F-FDG PET delayed imaging for the evaluation of thoracic abnormalities. METHODS: Eighty patients with thoracic nodular lesions seen on chest CT images were examined using early and delayed (18)F-FDG PET and (201)Tl-SPECT imaging within 1 wk of each study. The results of (18)F-FDG PET and (201)Tl SPECT were evaluated and compared with the histopathologic diagnosis. RESULTS: Fifty of the lesions were histologically confirmed to be malignant, whereas 30 were benign. On (18)F-FDG PET, all malignant lesions showed higher standardized uptake value (SUV) levels at 3 than at 1 h, and benign lesions revealed the opposite results. Correlations were seen between (18)F-FDG PET imaging and the degree of cell differentiation in malignant tumors. No significant difference in accuracy was found between (18)F-FDG PET single-time-point imaging and (201)Tl SPECT for the differentiation of malignant and benign thoracic lesions. However, the retention index (RI) of (18)F-FDG PET (RI-SUV) significantly improved the accuracy of thoracic lesion diagnosis. Furthermore, (18)F-FDG PET delayed imaging measuring RI-SUV metastasis was useful for diagnosing nodal involvement and it improved the specificity of mediastinal staging. CONCLUSION: No significant difference was found between (18)F-FDG PET single-time-point imaging and (201)Tl SPECT for the differentiation of malignant and benign thoracic lesions. The RI calculated by (18)F-FDG PET delayed imaging provided more accurate diagnoses of lung cancer.     

Clinical usefulness of ECG-gated18F-FDG PET combined with99mTc-MIBI gated SPECT for evaluating myocardial viability and function

OBJECTIVES: This study sought to evaluate an imaging approach using gated 99mTc-MIBI (MIBI) SPECT and gated 18F-FDG (FDG) PET for assessment of myocardial viability and cardiac function. METHODS: Forty-eight patients (38 men, mean age 68.1 +/- 9.6 years) underwent ECG-gated FDG PET and MIBI SPECT within a week. The baseline diagnoses were coronary artery disease (31), mitral regurgitation (1), paroxysmal arrhythmia (10), and dilated cardiomyopathy (6). The gated FDG PET data were analyzed using pFAST software, and the gated MIBI SPECT data were analyzed using QGS software. Fifteen patients were diagnosed with myocardial infarction, and follow-up study was performed to assess the functional outcome four months later. An improvement in LVEF of >5% was defined as significant. The LV myocardium was divided into 17 segments, and regional defect scores were visually assessed using a 4-point scale for each segment (0 = normal, 1 = mildly reduced, 2 = moderately reduced, 3 = absent). A segment with a greater defect score on MIBI SPECT than on FDG PET was defined as a mismatch. The patients were divided into two groups: those with at least two mismatched segments (MM-group), and those with none or one (M-group). RESULTS: LVEF, EDV and ESV measured by gated FDG PET were highly correlated with those obtained by gated MIBI SPECT (r = 0.848, 0.855 and 0.911, p < 0.0001, respectively). The mean values of LVEF did not differ significantly, but EDV and ESV obtained by gated FDG PET were significantly grater than those obtained by gated MIBI SPECT (p < 0.0001). In 15 patients diagnosed with myocardial infarction, a significant association (p < 0.05) was found between the relative uptake of FDG PET and MIBI SPECT and the functional outcome 4 months later. Global LV function improved in 6 of the 8 patients showing mismatch but in only 1 of the 7 patients with matched defects, resulting in a sensitivity of 86% and specificity of 75%. The overall accuracy to predict global functional outcome was high (80%). CONCLUSION: This imaging approach allows accurate evaluation of myocardial viability. Furthermore, the high correlations of gated FDG PET and gated MIBI SPECT measurements hold promise for the assessment of left ventricular function using gated FDG PET.     

Monitoring left ventricular dilation in mice with PET.

Molecular imaging by small-animal PET is an important noninvasive means to phenotype transgenic mouse models in vivo. When investigating pathologies of the left ventricular (LV) myocardium, the serial assessment of LV volumes is important. By this, the presence of LV dilation as a sign of developing heart failure can be detected. Whereas PET is usually used to derive biochemical and molecular information, functional parameters such as ventricular volumes are generally measured using echocardiography or MRI. In this study, a novel method to monitor LV dilation in mice with PET is presented and evaluated using cardiac MRI. METHODS: A semiautomatic 3-dimensional algorithm was used to delineate the LV myocardial wall on static PET images depicting myocardial glucose metabolism ((18)F-FDG PET) for 20 mice: 10 wild-type and 10 genetically modified littermates designed to develop a dilative cardiomyopathy phenotype (cardiomyocyte-specific knockout of survivin). The volume enclosed by the 3-dimensional midmyocardial contour was calculated as a measure for LV volume for each mouse. Data were compared with ventricular volumes measured by MRI in the same animals. RESULTS: LV volumes obtained by PET and MRI correlated well (R = 0.89) for hearts with small and large left ventricles. In accordance with the hypothesis, the LV volumes were increased significantly for transgenic mice examined at an older age compared with those examined at a younger age (MRI: 160.5 +/- 25.7 microL vs. 114.7 +/- 15.2 microL [P = 0.012]; PET: 129.3 +/- 15.3 microL vs. 73.8 +/- 15.0 microL [P < 0.001], all values shown as mean +/- SD; for MRI, mean of end-diastolic and end-systolic volumes are given), whereas they did not for their wild-type littermates (MRI: 106.2 +/- 12.3 microL vs. 94.7 +/- 14.6 microL [P = 0.214]; PET: 82.6 +/- 20.9 microL vs. 65.0 +/- 16.9 microL [P = 0.185]). CONCLUSION: Evaluation and quantitation of LV dilation in both control and cardiomyopathic mice can be reliably and serially performed using small-animal PET and (18)F-FDG, yielding useful functional information in addition to metabolic data.     

Relationship between exercise-induced myocardial ischemia and reduced left ventricular distensibility in patients with nonobstructive hypertrophic cardiomyopathy.

Many studies have demonstrated that reduced left ventricular (LV) diastolic distensibility plays a key role in the pathophysiology of hypertrophic cardiomyopathy (HCM). However, the relationship between myocardial ischemia and reduced LV distensibility in HCM remains unclear. We aimed to clarify the relationship between exercise-induced ischemia and reduced LV distensibility in patients with HCM. METHODS: Twenty patients with HCM and 5 age-matched control subjects underwent stress-redistribution (201)Tl myocardial scintigraphy and biventricular cardiac catheterization and echocardiography at rest and during exercise. Scintigraphic defect analysis was interpreted using Berman's 20-segment model. The summed stress score (SSS) was calculated as the sum of scores of the 20 LV segments and the summed difference score (SDS) was calculated as the sum of differences between each of the 20 LV segments on stress and rest images. RESULTS: Patients were divided into 2 groups according to the (201)Tl defect as follows: 9 patients with an SSS on (201)Tl of >or=10 and an SDS on (201)Tl of >or=5 (ischemic group) and 11 patients with an SSS of <10 or an SDS of <5 (nonischemic group). The absolute increases from rest to peak exercise in LV end-diastolic pressure (LVEDP) and pulmonary artery wedge pressure were significantly greater (15.5 +/- 5.2 vs. 7.6 +/- 5.5 mm Hg and 17.3 +/- 5.0 vs. 8.9 +/- 5.0 mm Hg, P < 0.01, respectively), and the percentage changes from rest to peak exercise in the maximum first derivative of LV pressure and LV pressure half-time were significantly smaller in the ischemic HCM group compared with the nonischemic HCM group (70% +/- 24% vs. 123% +/- 43% and -32% +/- 6.4% vs. -44% +/- 9.4%, P < 0.01, respectively). However, the end-diastolic dimensions did not differ between the 2 HCM groups. One of the 9 patients in the ischemic group, as revealed by fill-in on (201)Tl scintigraphy, showed increased (18)F-FDG uptake in the anteroseptal wall. CONCLUSION: Some HCM patients show a significant increase in LVEDP without chamber dilatation, indicating reduced LV diastolic distensibility. Myocardial ischemia may at least in part contribute to this condition.     

Electrocardiographic-gated dual-isotope simultaneous acquisition SPECT using 18F-FDG and 99mTc-sestamibi to assess myocardial viability and function in a single study

Purpose Dual-isotope simultaneous acquisition single-photon emission computed tomography (DISA SPECT) with ¹⁸F-fluorodeoxyglucose (FDG) and ^99mTc-sestamibi appears attractive for the detection of viable myocardium because it permits simultaneous assessment of glucose utilisation and perfusion. Another potential benefit of this approach is that the measurement of left ventricular (LV) function may be possible by ECG gating. The aim of this study was to test the hypothesis that both myocardial viability and LV function can be assessed by a single ECG-gated ¹⁸F-FDG/^99mTc-sestamibi DISA SPECT study, based on comparison with ¹⁸F-FDG/¹³N-ammonia positron emission tomography (PET) and magnetic resonance imaging (MRI) as reference techniques.Methods Thirty-three patients with prior myocardial infarction underwent ECG-gated ¹⁸F-FDG/^99mTc-sestamibi DISA SPECT and ¹⁸F-FDG/¹³N-ammonia PET on a single day. Of these, 25 patients also underwent cine-MRI to assess LV function. The LV myocardium was divided into nine regions, and each region was classified as viable or scar using a semiquantitative visual scoring system as well as quantitative analysis. The global and regional LV function measured by gated SPECT was compared with the results of MRI.Results There was good agreement in respect of viability (90–96%, 0.74–0.85) between DISA SPECT and PET by either visual or quantitative analysis. Furthermore, although both global and regional LV function measured by gated SPECT agreed with those by MRI, ^99mTc-sestamibi showed a closer correlation with MRI than did ¹⁸F-FDG.Conclusion In conclusion, ECG-gated DISA SPECT provides information on myocardial viability, as well as global and regional LV function, similar to that obtained by PET and MRI.     

Reverse redistribution on exercise-redistribution (201)Tl SPECT in chronic ischemic dysfunction: predictive of functional outcome after revascularization?

This study analyzed the incidence and clinical significance of reverse redistribution (RR) on stress-redistribution (201)Tl SPECT studies in patients with poor left ventricular function and tested the hypothesis that the RR phenomenon could be caused by artifacts. METHODS: Seventy-three consecutive patients with chronic coronary artery disease and left ventricular dysfunction (ejection fraction, 36% +/- 12%) who underwent exercise-redistribution-reinjection (201)Tl SPECT before myocardial revascularization were included. Recovery of left ventricular systolic function was assessed with 2-dimensional echocardiography performed before and 5.5 +/- 2.5 mo after revascularization. RR was determined visually and confirmed quantitatively as a > or = 10% decrease in (201)Tl uptake on the circumferential profiles. The left ventricle was divided in 16 segments for (201)Tl uptake and wall motion analyses. RESULTS: RR was present in 39 of 1,168 segments (3.3%) and in 18 of 73 patients (25%). Before revascularization, regional wall motion was normal in 26 of 39 RR segments (67%), hypokinetic in 7 of 39 (18%), and akinetic in 6 of 39 (15%). Eight percent of all dysfunctional segments (13/167) of RR patients presented RR. After revascularization, 60 of 167 dysfunctional segments (36%) improved function by > or = 1 grade, among which 8 (13%) displayed RR on (201)Tl SPECT before revascularization. Segments with RR improved function more frequently than those without RR (62% vs. 34%; P = 0.05). Using a threshold for segmental (201)Tl uptake of >54%, the accuracy of (201)Tl reinjection to detect functional improvement in RR segments after revascularization was 77% (10/13). Artifactually induced RR was also excluded in all but 1 case because no increased activity of the pixel used for normalization could be found on redistribution images relative to that of the stress images. CONCLUSION: These data suggest that in patients with chronic left ventricular ischemic dysfunction, RR on exercise-redistribution (201)Tl SPECT is not an artifact and occurs rarely in normally functioning and in dysfunctional myocardium. In the latter, RR is frequently associated with myocardial viability as shown by functional recovery after revascularization. However, the presence or absence of RR in dysfunctional segments seems to be of little clinical relevance.     

Prediction of functional recovery after revascularization in patients with chronic ischaemic left ventricular dysfunction: head-to-head comparison between 99mTc-sestamibi/18F-FDG DISA SPECT and 13N-ammonia/18F-FDG PET

Purpose ¹⁸F-FDG PET is an important modality for myocardial viability assessment in patients with left ventricular (LV) dysfunction. Dual-isotope simultaneous acquisition (DISA) SPECT may be an alternative to PET. The aim of this study was to compare the diagnostic performance of PET and DISA SPECT for the prediction of improvement in regional and global LV function as well as LV reverse remodelling after revascularization.Methods Patients (n=47) with chronic coronary artery disease and LV dysfunction underwent DISA SPECT (with ^99mTc-sestamibi and ¹⁸F-FDG) and PET (with ¹³N-ammonia and ¹⁸F-FDG) on the same day to assess viability. All patients underwent revascularization and recovery of function was derived from serial magnetic resonance imaging studies.Results Of 264 revascularized, dysfunctional segments, 143 (54%) improved in function. For prediction of improvement in regional LV function, PET and DISA SPECT had similar sensitivity (90% versus 89%, NS) and specificity (86% versus 86%, NS). For prediction of improvement in global LV function, sensitivity was 83% for DISA SPECT and 86% for PET (p=NS), whereas both modalities had a specificity of 100%. Finally, sensitivity and specificity for the prediction of LV reverse remodelling were also similar for DISA SPECT and PET.Conclusion In patients undergoing revascularization, DISA SPECT and PET predict the improvement in regional and global LV function and LV remodelling equally well post revascularization.