Assessment of ventricular function with first-pass radionuclide angiography using technetium 99m hexakis-2-methoxyisobutylisonitrile: a European multicentre study

Technetium-99m tetrofosmin myocardial perfusion single photon emission computed tomography in syndrome X: a preliminary report

Syndrome X is used to describe patients with chest pain and a normal coronary angiogram. We reviewed technetium-99m tetrofosmin (Tc-99m TF) myocardial perfusion single photon emission computed tomography (SPECT) results and clinical data of 43 syndrome X patients and 30 healthy controls with normal left ventricular ejection fraction and no cardiac abnormalities. The Tc-99m TF myocardial perfusion SPECT results showed 12 (27.9%) syndrome X patients had normal myocardial perfusion and 31 (72.1%) had abnormal myocardial perfusion, including 6 (14.0%) patients with fixed defects. 20 (46.5%) patients with transient defects, and 5 (11.6%) patients with reverse defects. The results of exercise ECG were not related to perfusion defects in Tc-99m TF myocardial perfusion SPECT. In contrast, all of the 30 (100.0%) healthy controls had normal myocardial perfusion SPECT results. We conclude that abnormal Tc-99m TF myocardial perfusion SPECT is common in syndrome X and does not correlate well with the exercise ECG. However, further studies with larger case numbers and long term follow up in patients with myocardial events are necessary to support our findings.

Measurement of ventricular function with radionuclide techniques

The noninvasive assessment of resting left ventricular performance has become an integral part of the evaluation of patients with known or suspected cardiac disease, having important diagnostic, therapeutic, and prognostic significance. This article details the wide range of clinical diagnostic possibilities available by dynamic imaging of myocardial function using scintigraphic techniques, including gated planar and tomographic blood pool imaging, first-pass radionuclide angiography, and gated tomographic perfusion imaging. The clinical and technical aspects described should be useful to the cardiologist intent upon supervising the performance of these tests, as well as providing their interpretation.

Left ventricular cavity-to-myocardium count ratio in exercise and resting technetium-99m-tetrofosmin SPECT: correlation with left ventricular function

The aim of this study was to assess the value of the cavity-to-myocardium count ratio (C/M ratio) calculated in exercise and resting technetium-99m (Tc-99m) tetrofosmin single photon emission computed tomography (SPECT) images to identify patients with depressed exercise and resting left ventricular ejection fraction (LVEF). We studied 60 patients with recent coronary artery diseases (CAD) undergoing first-pass ventriculography to calculate LVEF and myocardial perfusion SPECT imaging to calculate left ventricular C/M ratios. The group A of 30 CAD patients with higher LVEF (> or = 40%) had significant higher C/M ratios than the group B of 30 CAD patients with abnormal LVEF (< 40%) during exercise and rest. However, C/M ratios between exercise and rest did not differ significantly in the both groups A and B. There is significant correlation between exercise/rest LVEF and exercise/rest C/M ratios. Tc-99m tetrofosmin C/M ratios calculated SPECT perfusion images are useful parameters in identifying patients with depressed LVEF in CAD patients.

Exercise and rest technetium-99m-tetrofosmin lung uptake: correlation with left ventricular ejection fraction in patients with coronary artery disease

Increased lung uptake of thallium-201 (Tl-201) and technetium-99m (Tc-99m) MIBI in myocardial perfusion imaging is a reliable marker of left ventricular dysfunction. The goal of our study was to establish whether the lung-to-heart (L/H) uptake ratio with a newer cardiac imaging agent, Tc-99m tetrofosmin, can also provide valuable information about left ventricular function. We studied 60 patients with recent coronary artery diseases (CAD) undergoing first-pass radionuclide ventriculography to calculate left ventricular ejection fraction (LVEF) and myocardial perfusion imaging to calculate the L/H ratio. Group A consisting of 30 CAD patients with higher LVEF (> or =40%) had a significantly lower L/H ratio than group B consisting of 30 CAD patients with abnormal LVEF (<40%) during exercise and rest. In groups A and B, the exercise and rest L/H ratios did not differ significantly. However, a statistically significant inverse correlation was found between the L/H ratio and LVEF during exercise and rest among the 60 patients. L/H ratios, measured by 99mTc-tetrofosmin imaging, provide clinically useful information with which to predict left ventricular dysfunction in CAD patients.

Correlation of abnormal response of left ventricular ejection fraction after exercise and left ventricular cavity-to-myocardium count ratio of technetium-99m-tetrofosmin single photon emission computed tomography in patients with coronary artery disease

The aim of this study was to assess the value of the left ventricular cavity-to-myocardium count ratio (C/M ratio) of technetium-99m (Tc-99m) tetrofosmin single photon emission computed tomography (SPECT) to identify abnormal left ventricular ejection fraction (LVEF) responses after exercise in patients with coronary artery diseases (CAD). We studied 50 patients with recent CAD undergoing rest and exercise first-pass ventriculography to calculate LVEF and rest and exercise Tc-99m tetrofosmin myocardial perfusion SPECT to calculate left ventricular C/M ratios. Group A, consisting of 25 CAD patients with normal responses (increased LVEF> or =5% after exercise), had significantly higher rest and exercise C/M ratios than those of the group B, consisting of 25 CAD patients with abnormal responses (increased LVEF <5% after exercise) after exercise. However, the C/M ratios between exercise and rest did not differ significantly between groups A and B. In addition, there was significant correlation between LVEF and C/M ratios in all of the patients. C/M ratios of Tc-99m tetrofosmin myocardial perfusion SPECT are useful parameters for identifying patients with abnormal LVEF responses among patients with CAD.

New method for calculating right ventricular ejection fraction using gated myocardial perfusion studies

BACKGROUND

Quantification of right ventricular ejection fraction (RVEF) is important in patients who have right heart failure or cor pulmonale. When Tl-201 was the primary radiotracer used to evaluate myocardial perfusion, the outline of the right ventricle could vary and was not visualized in most patients. However, visualization of the right ventricle has become easier with the use of Tc-99m-labeled myocardial perfusion agents.

PURPOSE

This study describes a new method for quantifying RVEF using gated stress myocardial perfusion (GMP) slices. The results are compared with those of first-pass radionuclide ventriculography (FPRNA) in the same patients.

METHODS

Fifty-two consecutive patients referred for routine GMP imaging were included. After administration of Tc-99m tetrofosmin, all patients underwent FPRNA using a single crystal gamma camera and a GMP study. Regions of interest (ROI) were drawn to outline the right ventricular cavity at end diastole and end systole from three pairs of GMP slices. The RVEF was calculated from the number of pixels within the ROIs. The mean RVEF obtained using FPRNA and GMP imaging was 51.8 +/- 10.8% and 51.9 +/- 12.3%, respectively. The two methods showed good correlation with r = 0.81. In addition, there was no significant difference in the RVEFs calculated using these methods (P = 0.85). Bland-Altman analysis also showed good agreement between the two methods (limits of agreement +14.4% to -14.0%, slope = 0.19). Intraobserver and interobserver correlation were evaluated by reanalyzing 12 patients using the new RVEF quantification method and were good at r = 0.87 and 0.82, respectively. Therefore, this is a new convenient method for evaluating RVEF as part of a routine tomographic gated myocardial perfusion study.

Is a low-dose Tc-99m-MIBI protocol suitable for first-pass RNV?

Tc-99m-labelled radiopharmaceuticals, such as Tc-99m-sestamibi (Tc-99m-MIBI), offer the opportunity to measure myocardial perfusion and function with one injection only. The aim of this study was to evaluate whether first-pass (FP) radionuclide ventriculography (RNV) consecutively followed by myocardial perfusion single photon emission computed tomography (SPECT) may be performed according to a low-dose MIBI 1-day protocol using a multi-crystal gamma camera. Two hundred and seventy consecutive, predominantly obese [61% with a body mass index (BMI) of >25 kg x m(-2)] patients (169 male, 101 female), referred for myocardial perfusion SPECT with Tc-99m-MIBI [4 MBq x kg(-1) (>300 MBq) at stress; 9 MBq x kg(-1) (> 650 MBq) at rest], were studied with FP RNV prior to SPECT. Bicycle ergometry (29%), dobutamine (6%) or dipyridamole stress (65%) was performed. Adequate count (ct) statistics for FP RNV were defined as follows: (1) > 2000 cts within the background-corrected, end-diastolic (ED), left ventricular (LV) region of interest (ROI) of the representative cycle; and (2) >4 heart beats with > 1000 cts within the ED LV ROI (> 50% of maximal cts). A net mean dose of 318+/-64 MBq (4.3+/-1.1 MBq x kg(-1)) was injected during stress and 674+/-55 MBq (9.1+/-1.7 MBq x kg(-1)) during rest. There was no statistical difference among the three stress modalities concerning the net dose. Two hundred and fifty-six out of 270 (95%) stress and a basis for reliable all 270 (100%) rest FP RNV studies showed adequate count statistics as functional analysis. The 14 patients with insufficient count statistics were all obese and had received less than the planned dose. For the vast majority of patients, even a low-dose 1-day protocol with Tc-99m-MIBI is suitable for the assessment of FP RNV prior to SPECT. A minimum of 300 MBq and 4 MBq x (kg body weight)(-1) should be administered in order to obtain technically adequate results even in obese patients.

Application of mathematical methods in dynamic nuclear medicine studies

Dynamic nuclear medicine studies can generate large quantities of data, and their analysis consists essentially of a reduction of these data to a small number of relevant parameters which will assist in clinical decision making. This review examines some of the mathematical techniques that have been used in the process of data reduction and attempts to explain the principles behind their application. It particularly identifies the techniques that have stood the test of time and demonstrated their usefulness, many of which are now available as standard tools on nuclear medicine processing computers. These include curve processing tools such as smoothing, fitting and factor analysis, as well as tools based on empirical models, such as the Patlak/Rutland plot and deconvolution. Compartmental models and vascular models are also examined and the review finishes with a summary of some functional images and condensed images. It is concluded that an appreciation of the principles and limitations of these mathematical tools is valuable for their correct usage and interpretation of the results produced.

Simultaneous assessment of right ventricular function and hypertrophy by Tc-99m MIBI

PURPOSE

Tc-99m MIBI allows the simultaneous performance of cardiac blood pool scintigraphy and myocardial SPECT. The authors performed studies to determine whether right ventricular function and hypertrophy can be evaluated simultaneously using Tc-99m MIBI in patients with right heart disease.

METHODS

Using right heart catheterization, several parameters of pulmonary circulation were measured, including right ventricular ejection fraction, in 23 patients with chronic pulmonary disease and pulmonary vascular disease. Within 1 week, right heart blood pool scintigraphy was performed using the first-pass method using Tc-99m MIBI. The right ventricular ejection fraction calculated from right heart blood pool scintigraphy was compared with that measured using right heart catheterization. Myocardial SPECT was performed 1 hour after right heart blood pool scintigraphy. On the short axis images, which allowed optimal visualization of the right ventricle, the right and left ventricular free walls were established as regions of interest. Myocardial wall counts were determined. The right ventricular uptake: left ventricular uptake ratio was calculated to study the relation of that ratio to mean pulmonary artery pressure and total pulmonary resistance.

RESULTS

A significant correlation was observed between the right ventricular ejection fraction calculated on right heart catheterization and that calculated on right heart blood pool scintigraphy. The right ventricular uptake:left ventricular uptake ratio correlated positively with pulmonary artery pressure and total pulmonary resistance.

CONCLUSION

These results suggest that Tc-99m MIBI allows simultaneous noninvasive evaluation of cardiac function and structure, which previously was considered impossible in patients with right heart disease.

First-pass radionuclide angiocardiography with single-crystal gamma cameras

Both multicrystal and single-crystal detectors have been in use for more than 25 years for measurement of ejection fraction by analysis of images collected during the first-pass transit of radionuclides through the heart. Originally, multicrystal cameras were preferred, because they provided higher count rates than Anger cameras; however, over the years improvements in count rate capability and collimator design have enabled Anger cameras to perform equally well. This has become an important issue now that readily available 99mTc agents, such as sestamibi, enable evaluation of both myocardial function and perfusion from a single injection. The technical abilities of a particular camera determine which acquisition protocols are most likely to provide clinically useable images for the widest spectrum of patients. Electrocardiographic-gated list mode collection is highly desirable for first-pass imaging, providing the greatest flexibility of data review, rebinning, and analysis. Attention to quality control issues of data characterization and processing is important to ensure accuracy and precision of all measurements. Accurate determinations of ejection fraction of the left ventricle are possible routinely and, under favorable circumstances, of the right ventricle as well.

Combined left ventricular wall motion and myocardial perfusion stress imaging in the initial assessment of patients with a recent uncomplicated myocardial infarction

The aim of the study was to examine the ability to simultaneously assess left ventricular function and myocardial perfusion by using a single injection of technetium-99m sestamibi at rest and during submaximal exercise to identify high-risk patients with left main, proximal left anterior descending (LAD), or three-vessel coronary artery disease (CAD) after an uncomplicated acute myocardial infarction (AMI). Multiple studies have evaluated the separate value of the exercise ECG, myocardial perfusion scintigraphy, and radionuclide angiocardiography (RNA) for identifying patients with severe CAD. The availability of technetium-99m (Tc99m)-labeled myocardial imaging agents offers the opportunity to evaluate simultaneously ventricular function and myocardial perfusion during a single exercise session. Only limited data are available about the value of this combined technique in the workout of patients early after an uncomplicated AMI. Combined first-pass RNA and myocardial perfusion tomoscintigraphy (SPECT) at rest and during submaximal exercise were performed in 52 patients, less than six weeks after an uncomplicated AMI, with use of Tc99m sestamibi. Patients were classified in two subgroups according to the presence of left main, proximal LAD, or three-vessel CAD. Stepwise logistic regression analysis was used to determine the independent predictors of severe CAD. All patients underwent the exercise testing without any medical complication. On univariate analysis, the global left ventricular ejection fraction (LVEF), wall motion score, and myocardial perfusion score, both at rest and at submaximal exercise, were significantly associated with the presence of severe CAD. The response of LVEF to exercise, and the presence of exercise-induced wall motion or myocardial perfusion abnormalities, were not associated with the severity of CAD. On multivariant analysis only the wall motion score during exercise was an independent predictor for the presence of severe CAD (P < 0.001, r = 0.6). In analyzing patients with anterior AMI separately, LVEF at submaximal exercise was the most accurate predictive parameter. If a cutoff value of 40% was chosen, the LVEF at exercise had a sensitivity of 85% and a specificity of 78% for the detection of severe CAD. In patients with inferior AMI, neither LVEF nor wall motion or myocardial perfusion scores were useful for differentiating the two subgroups. In these patients the presence of an additional perfusion defect during exercise in one of the anterior wall segments yielded a sensitivity of 70% and a specificity of 75% for the presence of severe CAD.

IN CONCLUSION

simultaneous evaluation of LV function and myocardial perfusion at submaximal exercise, using a single injection of Tc99m-sestamibi, is a safe and accurate technique for selecting patients with severe CAD after an uncomplicated AMI.

Effect of dipyridamole on myocardial perfusion and function using technetium-99m MIBI

Myocardial perfusion imaging with dipyridamole is an accepted method for diagnosing coronary artery disease. However, the simultaneous effect of dipyridamole on perfusion and function in the detection of coronary artery disease has not been studied extensively. The aim of this study was to investigate this effect using technetium-99m methoxy isobutyl isonitrile (Tc-MIBI) imaging. Twenty-eight patients with proven coronary artery disease participated in a 2-day protocol (rest and then 0.56 mg/kg dipyridamole i.v.) using Tc-MIBI for first-pass radionuclide ventriculography followed by SPECT imaging. Fifteen patients (54%) demonstrated a decrease in left ventricular ejection fraction from rest to dipyridamole and/or wall motion abnormality, while 21 patients (75%) showed abnormal perfusion by dipyridamole MIBI SPECT imaging. Concordance between perfusion and function was 65%. Correlation for one-, two- and three-vessel disease (coronary angiography) to perfusion versus function were: 54% vs. 38%, 80% vs. 60% and 80% vs. 80%, respectively. Left ventricular dysfunction using dipyridamole was noted in patients with multivessel disease, and with multi-reversible perfusion filling defects. We conclude that dipyridamole in combination with Tc-MIBI for assessment of perfusion and function serves as a valuable tool to identify patients with multivessel disease and a high amount of myocardium at risk.

Evaluation of changes in myocardial perfusion and function on exercise in patients with coronary artery disease by gated MIBI scintigraphy

OBJECTIVE

To investigate the ability of gated methoxy-isobutylisonitrile (MIBI) scintigraphy to measure changes in myocardial function as well as perfusion with exercise.

SETTING

Regional cardiothoracic centre.

PATIENTS

43 presenting with chest pain, 28 with coronary artery disease on angiography, and 15 with normal coronary arteriograms.

RESULTS

Gated perfusion images showed an improvement in detecting regions with stenosed arteries compared with non-gated images (38/55 v 31/55, p < or = 0.01)). Functional analysis showed an increase in fractional shortening of 4.11% in subjects with normal coronary arteries, whereas in those with coronary disease a fall of 0.57% was found (p < or = 0.01). Both perfusion and function imaging showed an improved sensitivity compared with standard exercise testing (p < or = 0.01). When both function and perfusion imaging were analysed all patients with coronary disease were detected. There was agreement in abnormal regions in 33/55 territories supplied by a stenosed artery. Combined perfusion and function detected 49/55 (89%) of abnormal regions, thus improving the overall sensitivity from 38/55 (69%) by perfusion imaging alone (p < or = 0.01).

CONCLUSIONS

Gated methoxy-isobutylisonitrile scintigraphy can successfully evaluate perfusion and function on exercise, so improving the diagnostic usefulness of this agent.

Preliminary evaluation in humans of Tc-99m-Q3, a new tracer for myocardial perfusion imaging

Trans[99m-Tc-acac2en(TMPP)2]+, where acac2en is N,N'-ethylenebis(acetylacetone iminate) and TMPP is tris-(3 methoxy propyl) phosphine, (shortened Q3) is a new lipophilic Technetium-99m-labelled compound developed for myocardial perfusion imaging. Encouraging data were obtained in the experimental animal. Aim of this study was to perform a preliminary evaluation of Q3 imaging in humans and to compare it with a reference coronary flow tracer such as Tc-99m microspheres. Eight coronary artery disease patients (males, age 58.5 +/- 10 years) were studied. They were injected with 740 MBq of Q3 and single photon emission computed tomography (SPECT) was performed 90 minutes later. After 3 days 740 MBq of Tc-99m microspheres were injected through a pig-tail catheter in the left ventricle (LV), during heart catheterization, and SPECT was acquired 60 minutes later. Q3 images showed a good target/background activity ratio:LV wall/LV cavity = 4.16 +/- 1.2; myocardium/lung = 3.95 +/- 0.52; the related values with microspheres were 6.36 +/- 2.48 (N.S.) and 4.57 +/- 1.07 (N.S.), respectively. Q3 was cleared by the liver and at the moment of SPECT collection the myocardium/liver activity ratio was 1.54 +/- 0.32. The Q3 LV lateral wall/septum activity ratio showed a good correlation with the corresponding microspheres ratio: Q3 ratio = 0.027 + 0.95 microspheres ratio, r = 0.89, SEE = 1.12, p < 0.005.

Quantitative phase analysis of myocardial wall thickening by technetium-99m 2-methoxy-isobutyl-isonitrile SPECT

Regional wall thickening was assessed by ECG-gated SPECT using technetium-99m 2-methoxy-isobutyl-isonitrile (99mTc-MIBI). For myocardial segments with an optimal short axis, regional count changes from end-diastole to end-systole were used to calculate the regional wall thickening. Functional images displaying amplitude, % wall thickening (% WT), and phase were generated by a fundamental Fourier analysis. In the control subjects, % WT analysis showed heterogeneous contraction among the left ventricular wall segments. The amplitude values showed a similar pattern to the %WT values. Phase images demonstrated that the timing of ventricular contraction was almost homogenous between the various wall segments. In the CAD patients, regional decreases in amplitude and %WT corresponding to zones of reduced perfusion were shown in the ischemic segments. Phase images also indicated asynchronous contraction in these segments. Phase analysis of regional wall thickening in 99mTc-MIBI scintigraphy seems to be useful for understanding regional myocardial function in combination with perfusion scanning.

Perfusion and mechanical analysis with technetium-99m 2-methoxy-isobutyl-isonitrile in a case of dilated cardiomyopathy

With technetium-99m 2-methoxy-isobutyl-isonitrile (99mTc-MIBI), regional wall thickening in a patient with dilated cardiomyopathy was analyzed by the first component Fourier method. The regional wall thickening was compared with thallium-201 and 99mTc-MIBI SPECT imaging. Thallium-201 SPECT images showed mildly reduced perfusion in the posterior wall and redistribution in the septum, whereas 99mTc-MIBI images showed heterogeneous accumulation around the left ventricular circumference. By means of phase analysis, diffusely decreased wall thickening and discontinuity of percent wall thickening in neighboring segments were observed throughout the left ventricle. Regional wall motion and wall thickening correlated roughly. However, discrepancies between the mechanical function and myocardial perfusion, and discrepancies in regional myocardial perfusion between thallium-201 and 99mTc-MIBI were observed.