Acute myocardial infarction: myocardial viability assessment in patients early thereafter comparison of contrast-enhanced MR imaging with resting (201)Tl SPECT. Single photon emission computed tomography

PURPOSE: To compare contrast material-enhanced magnetic resonance (MR) imaging with resting thallium 201 ((201)Tl) single photon emission computed tomography (SPECT) for predicting myocardial viability in patients early after acute myocardial infarction. MATERIALS AND METHODS: Inversion-recovery contrast-enhanced MR images and resting (201)Tl SPECT images were obtained in 22 patients after acute myocardial infarction. The (201)Tl SPECT images were obtained 4.3 days +/- 0.2 (standard error) after the onset of myocardial infarction. Contrast-enhanced MR imaging was performed 7.9 days +/- 1.6 after (201)Tl SPECT. Transmural extent of hyperenhancement on contrast-enhanced MR images and regional (201)Tl activity were quantitatively analyzed with a 12-segment model. Regional wall thickening on follow-up cine MR images obtained 67 days +/- 17 after contrast-enhanced MR imaging was used as an index for myocardial viability. Statistical analyses were performed with the chi(2) and two-tailed Student t tests. RESULTS: Both contrast-enhanced MR and resting (201)Tl SPECT images showed significant correlations with regional wall thickening on follow-up cine MR images. The sensitivity, specificity, and accuracy of contrast-enhanced MR imaging in the prediction of viable myocardium were significantly higher than those of resting (201)Tl SPECT (98.0% vs 90.3%, P <.01; 75.0% vs 54.4%, P <.05; and 92.0% vs 81.1%, P <.001, respectively). CONCLUSION: Delayed contrast-enhanced MR imaging can help predict myocardial viability as seen on follow-up cine MR images after acute myocardial infarction, with significantly improved sensitivity, specificity, and accuracy in comparison with those of resting (201)Tl SPECT.     

Prediction of left ventricular remodeling and analysis of infarct resorption in patients with reperfused myocardial infarcts by using contrast-enhanced MR imaging

PURPOSE: To prospectively evaluate the accuracy of clinical and cardiac magnetic resonance (MR) imaging parameters for predicting left ventricular (LV) remodeling by using follow-up imaging as reference standard, and to prospectively evaluate infarct resorption in patients with reperfused first myocardial infarcts. MATERIALS AND METHODS: The study was approved by the institutional ethics committee and all patients gave written informed consent. In 55 patients (48 men, seven women; mean age+/-standard deviation, 56 years+/-13), contrast material-enhanced and cine MR imaging were performed 5 days+/-3 and 8 months+/-3 after myocardial infarction (MI). Microvascular obstruction (MO) and infarct size were estimated at first-pass enhancement (FPE) and delayed enhancement (DE) MR, respectively. Remodeling was defined as an increase in LV end-diastolic volume index of 20% or higher at follow-up. Differences in continuous and categorical data were analyzed by using Student t test and Fischer exact test as appropriate. RESULTS: Patients with remodeling (n=13, 24%) had higher creatine kinase MB (P<.05), more anterior infarcts (P<.05), more often a reduced Thrombolysis in Myocardial Infarction flow (P<.05), larger infarct size at DE MR (P<.001), a greater extent of MO at FPE MR (P<.01), lower ejection fraction (P<.001) and higher LV end-systolic volume index (P<.01). Infarct size at DE MR was a powerful predictor for remodeling (odds ratio: 1.18, P<.001), demonstrating that the risk for remodeling increased 2.8-fold with each 10% increase in infarct size. Infarct size of 24% or more of LV area predicted remodeling with high sensitivity (92%), specificity (93%), and accuracy (93%). Infarct resorption was larger in patients with remodeling (P<.01). CONCLUSION: Infarct size 24% or more of the LV area constitutes an important threshold to predict remodeling. Patients with remodeling develop disproportionate infarct resorption.     

Evaluation of acute myocardial infarction with late enhancement pattern on MRI compared with 201Tl and 99mTc-hydroxymethylenediphosphonate (HMDP) dual single photon emission computed tomography (SPECT) images

The purpose of this study is to evaluate reperfused acute myocardial infarction with late enhancement (LE) pattern on contrast-enhanced magnetic resonance imaging compared with myocardial single photon emission computed tomography (SPECT) images. MATERIALS AND METHODS: Magnetic resonance and 201Tl and 99mTc-hydroxymethylenediphosphonate SPECT images were obtained from 40 patients within 6 days of reperfused myocardial infarction. We assessed the myocardial LE pattern using the true fast imaging with steady-state free precession sequence after the injection of Gd-DTPA. Patients were classified into 3 groups: group 1 included patients with localized endocardial enhancement; group 2, patients with transmural enhancement; and group 3, patients with LE and a residual defect. RESULTS: There were 9 patients (23%) in group 1, 15 (38%) in group 2, and 15 (38%) in group 3. In 1 patient, LE was not detected (3%). The %201Tl uptake for the infarcted area was 60.7 +/- 7.2 (mean +/- SD) for group 1, 49.5 +/- 12.3 (P < 0.05 vs. group 1) for group 2, and 36.9 +/- 8.2 (P < 0.0001 vs. group 1, P = 0.005 vs. group 2) for group 3. An overlap pattern of 201Tl and 99mTc was observed in 9 of the group 1 patients (100%) and 9 of the group 2 patients (60%), but was not evident in group 3 (0%). CONCLUSIONS: LE with residual defect is an important indicator of microvascular obstruction after reperfusion therapy.     

Quantification of myocardial ischemia and infarction with single photon emission computed tomography

To evaluate the feasibility of 201Tl single photon emission computed tomography (SPECT) for quantitative detection of myocardial infarction and ischemia, scintigraphic studies were related to angiographic findings. In study A infarct sizes with SPECT were compared with the angiographic infarct sizes of 30 patients. A linear correlation was found for the % infarct of the left ventricular circumference between both methods (r = 0.73; P less than 0.001; mean infarct size 20.7% +/- 10.5% (angio) vs 19.8% +/- 12.9% (SPECT), mean +/- SD). Furthermore, a significant inverse correlation between scintigraphic infarct size and left ventricular ejection fraction (r = -0.87, P less than 0.001) was obtained. In study B exercise/rest 201Tl SPECT was used for quantification of myocardial ischemia. Forty-three patients underwent both stress 201Tl SPECT and biplane exercise left ventriculography. Ischemia was expressed as % defect size of the left ventricular circumference. Sensitivity and specificity for detection of ischemia were 96% and 100% respectively with stress SPECT. Extent of myocardial ischemia correlated significantly with both methods (r = 0.63; SPECT defect = 1.0 angiographic ischemia +2%; P less than 0.001). The regression followed the line of identity and the mean sizes of ischemia were identical (SPECT 12.2 +/- 7.6% vs 14.6 +/- 12.4% ventriculography, mean +/- SD) demonstrating the agreement of both methods. However, there was some intraindividual variance between the scintigraphic and the angiographic study. The sensitivity and specificity in single regions with SPECT were lower compared to the global test results.(ABSTRACT TRUNCATED AT 250 WORDS)     

Gadomer-enhanced MR imaging in the detection of microvascular obstruction: alleviation with nicorandil therapy

PURPOSE: To evaluate Gadomer-enhanced magnetic resonance (MR) imaging in the quantification of small microvascular obstruction regions and determine if nicroandil alleviates the formation of microvascular obstruction. MATERIALS AND METHODS: Approval of the institutional committee on animal research was obtained, and this study complied with guidelines for care and use of animals. Rats underwent coronary artery occlusion and reperfusion. After 24 hours, Gadomer-enhanced T1-weighted spin-echo MR imaging was used to define microvascular obstruction in animals in control and nicorandil groups. Sequential MR images obtained at two midventricular levels were acquired to measure microvascular obstruction and ischemically injured regions and monitor diffusive and/or convective transport of Gadomer in microvascular obstruction regions. Two investigators working in consensus and using threshold signal intensity measured differentially enhanced regions. Left-ventricular (LV) end-systolic and end-diastolic MR images obtained at the same two midventricular levels were used to measure regional wall thickening and systolic reduction in LV relative volumes. Agreement and correlation between MR imaging and postmortem data were determined with Bland-Altman and linear regression analyses. Animals were sacrificed 3 minutes after intravenous injection of blue dye. RESULTS: On Gadomer-enhanced MR images, two differentially enhanced regions were observed in ischemically injured myocardium, namely, the hypoenhanced region and the surrounding hyperenhanced region. Hypoenhanced regions at MR imaging and unstained regions at blue dye administration were identical 3 minutes after administration (17% +/- 1 and 17% +/- 2; P = .6; r = 0.98). In the control group, Gadomer provided a prolonged imaging window (eg, 6 minutes) for accurately quantifying small microvascular obstruction regions. Microvascular obstruction was observed in all animals in the control group and 27% of animals in the nicorandil group. Microvascular obstruction regions were smaller in the nicorandil group (eg, 3% +/- 1) than in the control group (eg, 17% +/- 2) (P < .001). Hyper- and hypoenhanced regions were also smaller (eg, 20% +/- 2) in rats in the nicorandil group than in those in the control group (37% +/- 4, P < .001). Improvement in LV function in the nicorandil group is likely related to alleviation and reduction in infarct size. CONCLUSION: Gadomer-enhanced MR imaging can be used to quantify small microvascular obstruction regions 24 hours after reperfusion. Intravenous therapy with nicorandil reduces formation of microvascular obstruction regions.     

Gadobenate dimeglumine in MRI of acute myocardial infarction: results of a phase III study comparing dynamic and delayed contrast enhanced magnetic resonance imaging with EKG, (201)Tl SPECT, and echocardiography

RATIONALE AND OBJECTIVES: To evaluate the safety and utility of gadobenate dimeglumine as a magnetic resonance (MR) contrast agent in patients with acute myocardial infarction (MI). METHODS: One hundred three patients with acute MI received intravenous bolus gadobenate dimeglumine (0.05 mmol/kg) during MR examination. Dynamic and delayed T1-weighted spin-echo postcontrast images were compared with precontrast images, EKG, resting (201)Tl SPECT and echocardiography. RESULTS: Gadobenate dimeglumine was well tolerated. Dynamic imaging with gadobenate dimeglumine was more sensitive (72% vs 56%) than delayed spin echo imaging (P < 0.001). No difference in specificity was seen (98% vs 99%). (201)Tl SPECT was a sensitive (96%) test, but was not specific (63%). Echocardiography was not sensitive (32%), but was specific (92%). CONCLUSION: The intravenous use of gadobenate dimeglumine, at a bolus dose of 0.05 mmol/kg, is safe in patients with an acute MI. Dynamic contrast enhanced MR imaging has moderate sensitivity and high specificity for demonstrating infarct.     

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.     

Myocardial infarct size after reperfusion therapy: assessment with Gd-DTPA-enhanced MR imaging

In 21 patients with proved acute myocardial infarction, the size of the infarct was estimated with serial magnetic resonance (MR) imaging after intravenous injection of gadolinium diethylenetriaminepentaacetic acid (DTPA) (0.2 mmol per kilogram of body weight). Early reperfusion after thrombolytic therapy or percutaneous transluminal coronary angioplasty performed during the acute phase of infarction was documented with coronary angiography in nine patients (group 1). In 12 patients (group 2), no reperfusion was achieved (n = 5) or no thrombolytic therapy was given (n = 7). All group 2 patients were considered to have no reperfusion. Infarct sizes measured with MR imaging were significantly smaller in group 1 than in group 2 at 8 days +/- 4 after infarct onset (8% +/- 5% vs 15% +/- 4%, respectively; P less than .001). Serial MR images showed individual variations in infarct size, findings that may be clinically significant. Estimation of infarct size with Gd-DTPA-enhanced MR imaging is accurate in demonstrating the effect of successful reperfusion therapy on infarct size.     

Comparison of contrast-enhanced MRI with (18)F-FDG PET/201Tl SPECT in dysfunctional myocardium: relation to early functional outcome after surgical revascularization in chronic ischemic heart disease.

Revascularization of viable myocardial segments has been shown to improve left ventricular (LV) function and long-term prognosis; however, the surgical risk is comparatively higher in patients with a low ejection fraction (EF). We compared contrast-enhanced MRI with (18)F-FDG PET/(201)Tl SPECT for myocardial viability and prediction of early functional outcome in patients with chronic coronary artery disease (CAD). METHODS: Forty-one patients with chronic CAD and LV dysfunction (mean age +/- SD, 66 +/- 10 y; 32 men; mean EF +/- SD, 38% +/- 13%) referred for (18)F-FDG PET, (201)Tl-SPECT and MRI within 2 wk were included. Twenty-nine subjects underwent coronary artery bypass grafting (CABG), and LV function was reassessed by MRI before discharge (17 +/- 7 d after surgery). Two were excluded from outcome analysis (1 death due to sepsis; 1 perioperative myocardial infarction). The extent of viable myocardium by (18)F-FDG PET/(201)Tl SPECT was defined by the metabolism-perfusion mismatch or ischemia, in comparison with the extent of delayed enhancement (DE) on MRI in a 17-segment model. Segmental functional recovery was defined as improvement in the wall motion score of > or =1 on a 4-point scale. EF and LV volume change were used as global functional outcome. RESULTS: Three hundred ninety-four dysfunctional segments were compared, and the extent of DE on MRI correlated negatively with the viability on (18)F-FDG PET. Of 252 dysfunctional segments that were successfully revascularized, the sensitivity, specificity, positive predictive value, and negative predictive value of PET/SPECT were 60.2%, 98.7%, 76.6%, and 96.7% and of MRI were 92.2%, 44.9%, 72.4%, and 78.6% using the cutoff value of 50% DE on MRI, without significant differences in overall accuracies. In 18 subjects who underwent isolated CABG, improvement of EF (> or =5%) and reverse LV remodeling (> or =10% LV size reduction) was best predicted by the no DE on MRI, and patients with substantial nonviable myocardium on (18)F-FDG/SPECT predicted a poor early functional outcome (all P < 0.001). CONCLUSION: Accurate prediction of early functional outcome by PET/SPECT and contrast-enhanced MRI is possible.     

Automatic detection and size quantification of infarcts by myocardial perfusion SPECT: clinical validation by delayed-enhancement MRI.

We aimed to validate the accuracy of a new automated myocardial perfusion SPECT quantification based on normal limits for detection and sizing of infarcts, using delayed-enhancement MRI (DE-MRI) as a gold standard. METHODS: Eighty-two immediate (201)Tl rest scans and 26 (201)Tl delayed redistribution scans were compared with resting DE-MRI scans acquired within 24 h of SPECT acquisition. The immediate (201)Tl scans were considered for validation of infarct detection and the delayed (201)Tl scans were considered for infarct sizing. A simplified quantification scheme was used in which defect extent (EXT) and total perfusion deficit (TPD) parameters were derived automatically from SPECT images by comparison with sex-matched normal limits and applying a 3.0 average deviation criterion. The total extent of hyperenhancement expressed as the percentage of the left ventricle was derived from DE-MRI images by visual definition of myocardial contours and defects. DE-MRI and SPECT images were fused in 3 dimensions for visual comparison. Phantom data were also quantified using the same EXT and TPD measures for defects ranging from 5% to 70% of the myocardium. RESULTS: The area under the receiver-operator-characteristic curve for the detection of infarct on immediate rest scans was 0.91 +/- 0.03 for EXT and 0.90 +/- 0.03 for TPD (P = not significant). The sensitivity and specificity for the detection of infarct by EXT on immediate (201)Tl rest scan were 87% and 91%, respectively, with the optimal defect size threshold of 4%. Six of 7 cases with DE-MRI defects < 5% were detected by SPECT. Infarct sizes obtained from DE-MRI correlated well with EXT (slope = 0.94, offset = 3.8%; r = 0.84) and TPD (slope = 0.75, offset = 4.2%; r = 0.85) obtained from delayed SPECT (201)Tl scans. Excellent correlation was observed between the SPECT quantification and the physical defect size for the phantom data. The actual size of the defect was better estimated by EXT (slope = 1.00, offset 1.33%; r = 0.99) than by TPD (slope = 0.79, offset = 1.9%; r = 0.99). CONCLUSION: Automated quantification of the EXT on myocardial perfusion SPECT images can reliably detect infarcts and measure infarct sizes.     

The assessment of infarct size in postmyocardial infarction patients undergoing thallium-201 tomographic imaging is improved using attenuation correction

PURPOSE: Attenuation correction (ATC) has been shown to improve the accuracy of thallium-201 single photon emission computed tomography (SPECT) for the detection and evaluation of patients with coronary artery disease. The purpose of this study was to evaluate the value of ATC for the assessment of infarct size in patients after myocardial infarction (MI). MATERIALS AND METHODS: Tl-201 SPECT with ATC was performed on 39 patients with 49 previous MIs. This was followed by radionuclide ventriculography for the assessment of global and regional left ventricular function. Uncorrected and corrected 24-hour redistribution SPECT images were analyzed for regional perfusion using a 5-point segmental scoring scale from 0 (normal) to 4 (absent) thallium uptake. RESULTS: The mean number of segments with scores of >1 and 2 was significantly higher without ATC than with ATC (5.3 +/- 3.6 vs. 3.5 +/- 3.6, P = 0.0001 for scores >1; 3.8 +/- 3.6 vs. 2.5 +/- 3.0, P = 0.0001 for scores of >2, respectively). The mean total number of segments with scores of >1 assessed without ATC was significantly higher compared with that assessed with ATC (16.9 +/- 13.5 vs. 11.2 +/- 12.2, P = 0.0001). Evaluation without ATC demonstrated only a fair correlation between the SPECT parameters (number of segments with scores of >1 and >2, and total score of segments with scores of >1) and left ventricular regional and global function, whereas there was a clear improvement in all the parameters after ATC. With ATC, a decrease in infarct size was demonstrated in 27 of the 49 infarcts (55%). CONCLUSIONS: The improved correlation with left ventricular function indicates that SPECT imaging with ATC provides a more accurate assessment of infarct size in post-MI patients. The use of nonattenuation-corrected SPECT imaging overestimates infarct size in a majority of patients.     

Usefulness of Tl-201 SPECT imaging in evaluation of left ventricular hypertrophy and dilation in patients with previous myocardial infarction.

Using short axis slices of Tl-201 myocardial SPECT images, total left ventricular (LV) mass, perfused LV mass, defect size, defect mass, ratio of total LV area to cavity area (T/C), ratio of radius of total LV area to radius of cavity area (TR/CR), and ratio of wall thickness to radius of cavity area (W/R) were obtained. The left ventricular ejection fraction (LVEF) was calculated using blood pool imaging studies. A total of 33 patients with old myocardial infarctions were studied. The patients were divided into group 1 (n = 16) with no history of heart failure, and group 2 (n = 17) with a history of heart failure. The LVEF (P less than 0.001), T/C (P less than 0.005), TR/CR (P less than 0.005) and W/R (P less than 0.001) were significantly lower, while the total LV mass (P less than 0.001) and perfused LV mass (P less than 0.01) were significantly higher in group 2. In the whole group of 33 patients, there was inverse linear correlation between the total LV mass and LVEF (r = -0.82), perfused LV mass and LVEF (r = -0.67), and defect mass and LVEF (r = -0.59). There was linear correlation between W/R and LVEF (r = 0.64). Nonlinear correlations were found between T/C and LVEF (r = 0.81) and TR/CR and LVEF (r = 0.80). Tl-201 myocardial SPECT imaging is useful for the evaluation of LV hypertrophy and cavity dilation in patients with previous myocardial infarction.     

Detection and quantification of recent myocardial infarction: diagnostic value of multiecho multislice spin echo imaging

Thirty-four patients with documented transmural MI were studied with gated three echo, multislice MR imaging. In 12 patients MRI MI size was compared with CK release measurement, Tl-201 SPECT defect, and with Tc-99m LVEF. Infarct was visualised in 29/34 patients on 3rd echo images (18/34 on 2nd and 6/34 on 1st echo images). Mean MR infarct size (planimetered from 3rd echo images): 33.1 +/- 9% overestimated the SPECT defect (mean value of 23.8 +/- 15%). However, the overall correlation between MRI and Tl-201 sizing was significant: r = 0.82; p less than 0.001; SEE = 5.5%. The correlation with LVEF also appeared significant: r = -0.61; p less than 0.038.     

Value of myocardial defect size measured by thallium-201 SPECT: results of a multicenter trial comparing heparin and a new fibrinolytic agent

In a multicenter randomized double-blind trial comparing heparin and a new fibrinolytic agent, anisoylated plasminogen streptokinase activator complex (APSAC), 231 patients presenting with a less than 5 hr acute myocardial infarction underwent a contrast angiography (CA) before the end of the first week of admission, and radionuclide cardiac blood-pool imaging and a 201Tl single photon emission computed tomography (SPECT) study before the end of the third week. Left ventricular ejection fraction (LVEF) and a wall motion score (WM) were calculated from CA. LVEF was also obtained from cardiac blood-pool imaging, and defect size (DS) from 201Tl SPECT. Results demonstrated that all parameters were significantly improved in patients treated with APSAC versus heparin (contrast LVEF 53 +/- 13 vs. 47 +/- 14 p less than 0.01, WM 9.8 +/- 6.5 vs. 13.3 +/- 7.9 p less than 0.001, radionuclide LVEF 43 +/- 12 vs. 40 +/- 13 p less than 0.05, DS 14 +/- 12 vs. 18 +/- 14 p less than 0.05). When the patients were divided according to infarct site and infarct-related coronary artery patency, it was demonstrated with all four parameters that the beneficial effect of APSAC can be largely explained by the lower incidence of vessel obstruction in this group (37% vs. 77% in the heparin group, p less than 0.001). It is concluded that (a) when compared with heparin and in the conditions of the trial, APSAC significantly improves the cardiac function and decreases the DS and (b) DS measured by 201Tl SPECT is as valuable a quantitative parameter of therapeutic evaluation as are LVEF and WM.     

Thallium-gated SPECT in patients with major myocardial infarction: effect of filtering and zooming in comparison with equilibrium radionuclide imaging and left ventriculography.

The effect of filtering and zooming on 201TI-gated SPECT was evaluated in patients with major myocardial infarction. METHODS: Rest thallium (TI)-gated SPECT was performed with a 90 degrees dual-head camera, 4 h after injection of 185 MBq 201TI in 32 patients (mean age 61 +/- 11 y) with large myocardial infarction (33% +/- 17% defect on bull's eye). End diastolic volume (EDV), end systolic volume (ESV) and left ventricular ejection fraction (LVEF) were calculated using a commercially available semiautomatic validated software. First, images were reconstructed using a 2.5 zoom, a Butterworth filter (order = 5) and six Nyquist cutoff frequencies: 0.13 (B5.13), 0.15 (B5.15), 0.20 (B5.20), 0.25 (B5.25), 0.30 (B5.30) and 0.35 (B5.35). Second, images were reconstructed using a zoom of 1 and a Butterworth filter (order = 5) (cutoff frequency 0.20 [B5.20Z1]) (total = 32 x 7 = 224 reconstructions). LVEF was calculated in all patients using equilibrium radionuclide angiocardiography (ERNA). EDV, ESV and LVEF were measured with contrast left ventriculography (LVG). RESULTS: LVEF was 39% +/- 2% (mean +/- SEM) for ERNA and 40% +/- 13% for LVG (P = 0.51). Gated SPECT with B5.20Z2.5 simultaneously offered a mean LVEF value (39% +/- 2%) similar to ERNA (39% +/- 2%) and LVG (40% +/- 3%), optimal correlations with both ERNA (r = 0.83) and LVG (r = 0.70) and minimal differences with both ERNA (-0.9% +/- 7.5% [mean +/- SD]) and LVG (1.1% +/- 10.5%). As a function of filter and zoom choice, correlation coefficients between ERNA or LVG LVEF, and gated SPECT ranged from 0.26 to 0.88; and correlation coefficients between LVG and gated SPECT volumes ranged from 0.87 to 0.94. There was a significant effect of filtering and zooming on EDV, ESV and LVEF (P < 0.0001). Low cutoff frequency (B5.13) overestimated LVEF (P < 0.0001 versus ERNA and LVG). Gated SPECT with 2.5 zoom and high cutoff frequencies (B5.15, B5.20, B5.25, B5.30 and B5.35) overestimated EDV and ESV (P < 0.04) compared with LVG. This volume overestimation with TI-gated SPECT in patients with large myocardial infarction was correlated to the infarct size. A zoom of 1 underestimated EDV, ESV and LVEF compared with a 2.5 zoom (P < 0.02). CONCLUSION: Accurate LVEF measurement is possible with TI-gated SPECT in patients with major myocardial infarction. However, filtering and zooming greatly influence EDV, ESV and LVEF measurements, and TI-gated SPECT overestimates left ventricular volumes, particularly when the infarct size increases.     

扩张型心肌病患者双嘧达莫负荷心肌201Tl SPECT显像分析

目的 观察扩张型心肌病患者的双嘧达莫负荷心肌201Tl SPECT显像表现.方法 2008年8月至2009年12月临床符合扩张型心肌病诊断标准的住院患者30例,按体质量0.56 mg/kg给予其双嘧达莫,于4 min内静脉注射,2 min后注射201Tl,注射完后10及240 min分别进行双嘧达莫负荷心肌201Tl SPECT显像,图像经三维重建后由2位以上有经验的核医学科医师进行分析.结果 27例(90.00%)患者的双嘧达莫负荷201Tl图像(10 min)显示左心室心肌放射性分布异常.延迟(240 min)显像时所有患者均出现左室心肌放射性分布异常,其中6例患者出现"反向再分布".结论 双嘧达莫负荷心肌201Tl SPECT显像对指导扩张型心肌病的诊治具有一定的临床意义.     

扩张型心肌病患者双嘧达莫负荷心肌^201Tl SPECT显像分析

目的 观察扩张型心肌病患者的双嘧达莫负荷心肌201Tl SPECT显像表现.方法 2008年8月至2009年12月临床符合扩张型心肌病诊断标准的住院患者30例,按体质量0.56 mg/kg给予其双嘧达莫,于4 min内静脉注射,2 min后注射201Tl,注射完后10及240 min分别进行双嘧达莫负荷心肌201Tl SPECT显像,图像经三维重建后由2位以上有经验的核医学科医师进行分析.结果 27例（90.00%）患者的双嘧达莫负荷201Tl图像（10 min）显示左心室心肌放射性分布异常.延迟（240 min）显像时所有患者均出现左室心肌放射性分布异常,其中6例患者出现＂反向再分布＂.结论 双嘧达莫负荷心肌201Tl SPECT显像对指导扩张型心肌病的诊治具有一定的临床意义.     

Relationship between resting 201Tl reverse redistribution, microvascular perfusion, and functional recovery in acute myocardial infarction.

201TI reverse redistribution is a common finding early after reperfusion therapy for myocardial infarction. Its mechanism and clinical implications remain unclear. The aim of this study was to clarify the relationships between reverse redistribution, microvascular perfusion, and myocardial viability. METHODS: Resting, 10-min-postinjection, and redistribution 201TI data obtained for 33 patients 8 and 42 d after the onset of acute myocardial infarction were compared with echocardiographic wall motion measured acutely and on day 42. Microvascular perfusion was assessed by myocardial contrast echocardiography performed 10 min after restoration of complete patency of the infarct artery. RESULTS: Marked significant reverse redistribution was found on day 8 (absolute change, 7.5%+/-7.9% of the 10-min-postinjection defect size; P<5x0.000001) and significantly decreased on day 42 (2.7%+/-6.8%; P = 0.004 between days 8 and 42). The 10-min-postinjection defect size best predicted the final infarct size on day 42 and was closely related to microvascular perfusion. Patients with adequate reperfusion had a smaller postinjection defect on day 8 (21.1%+/-14.6%) and a larger reverse redistribution (10.2%+/-6.1%) than did patients with no reflow (35.3%+/-13% and 3.2%+/-9.2%, respectively; P<0.04 for both). CONCLUSION: Reverse redistribution was marked early after myocardial infarction in patients with complete patency of the infarct artery and decreased in subsequent weeks. Reverse redistribution was associated with restoration of adequate microvascular reperfusion and with myocardial salvage and viability. The early postinjection scans on day 8 were the relevant images for assessing myocardial salvage and predicting wall motion recovery.     

MR imaging of reperfused myocardial infarction: comparison of necrosis-specific and intravascular contrast agents in a cat model

PURPOSE: To compare T2-weighted and Gadomer-17- and bis-gadolinium mesoporphyrins-enhanced magnetic resonance (MR) images for distinguishing reversibly from irreversibly damaged myocardium in a cat model of reperfused myocardial infarction. MATERIALS AND METHODS: Twelve cats underwent 90 minutes of occlusion and 90 minutes of reperfusion of the left anterior descending coronary artery. After baseline T1- and T2-weighted MR images were obtained, Gadomer-17-enhanced and bis-gadolinium mesoporphyrins-enhanced T1-weighted images were sequentially obtained for 6 hours and 2 hours, respectively. After MR imaging, all cats were sacrificed for 2,3,5-triphenyltetrazolium chloride (TTC) histochemical tissue staining. Areas of abnormal signal intensity on T2-weighted and Gadomer-17-enhanced and bis-gadolinium mesoporphyrins-enhanced T1-weighted MR images were compared with the areas of infarction seen at TTC histochemical staining by using repeated-measures two-way analysis of variance, linear regression analysis, and Bland-Altman analysis. RESULTS: Mean areas of abnormally high signal intensity on T2-weighted and Gadomer-17-enhanced T1-weighted MR images (43.9% of the left ventricular surface area +/- 11.9 [SD] and 37.7% +/- 10.1, respectively) were significantly larger than the mean area of myocardial infarction at TTC staining (25.7% +/- 12.5) (P <.001). However, there was excellent correlation between the size of an enhancing area on bis-gadolinium mesoporphyrins-enhanced T1-weighted MR images and that of myocardial infarction at TTC staining (r = 0.916, P <.001). CONCLUSION: bis-Gadolinium mesoporphyrins-enhanced T1-weighted MR images accurately reflect the area of infarction, whereas the size of infarction is overestimated on T2-weighted and Gadomer-17-enhanced T1-weighted MR images, which seem to depict the periinfarct area as well as the infarct area.     

Assessment of nicorandil therapy in ischemic myocardial injury by using contrast-enhanced and functional MR imaging.

PURPOSE: To determine the potential of mesoporphyrin- and gadopentetate dimeglumine-enhanced and functional magnetic resonance (MR) imaging in the assessment of the acute effect of nicorandil on ischemic injury of the myocardium. MATERIALS AND METHODS: Spin-echo MR imaging was used to monitor changes in myocardial contrast and function in reperfused myocardial injury. Inversion-recovery echo-planar MR imaging was used to depict the injured region. Myocardial injury in rats was produced by using 30 minutes of coronary occlusion followed by 24 hours reperfusion. Nicorandil (n = 9) was infused during occlusion and early reperfusion. Control animals (n = 11) received no therapy. At 24 hours, after administration of mesoporphyrin and gadopentetate dimeglumine and histochemical staining, the function and size of the injured region of the left ventricle (LV) were determined. A t test was used to compare data between groups of animals, whereas regression and Bland-Altman analyses were used to determine correlation and agreement between MR imaging and histomorphometry, respectively. RESULTS: Treated animals showed reduced infarction size as compared with the control group from 25.6% +/- 7.9 (SD) to 7.9% +/- 6.8 of LV myocardial area (P < .001), as defined with mesoporphyrin-enhanced MR imaging; while the size of the rim increased from 10.8% +/- 10.0 to 16.1% +/- 14.4 (P < .05). The diastolic-midventricular cavity area was smaller in treated animals (15.2 mm(2) +/- 4.3) compared with the control group (28.5 mm(2) +/- 7.9; P < .001). At functional MR imaging, nicorandil improved systolic reduction in LV cavity area (57.5% +/- 17.3) compared with the control group (38.0% +/- 16.0; P < .05) and preserved regional LV wall thickening at the site of injury (12.2% +/- 11.1 in treated group vs 0.3% +/- 8.6 in the control group; P < .05). CONCLUSION: Contrast material-enhanced MR imaging has the potential to demonstrate reduction in size of ischemically injured myocardium, whereas functional MR imaging demonstrated the recovery of LV function 24 hours after nicorandil therapy.