Tomographic gated blood pool radionuclide ventriculography: analysis of wall motion and left ventricular volumes in patients with coronary artery disease.

The use of planar radionuclide ventriculography to evaluate global and segmental ventricular function is limited by the superimposition of structures in some projections and the gross segmental resolution of the planar technique. Preliminary reports have suggested the feasibility of tomographic gated radionuclide ventriculography with rotating detector systems. This study tested the hypotheses that 1) tomographic radionuclide ventriculography detects segmental dysfunction at rest not identified with multiview planar studies and single plane contrast ventriculography, and 2) ventricular volumes and ejection fraction calculated from these studies provide data similar to those obtained with angiography and planar radionuclide ventriculography. Gated blood pool tomograms were acquired over 180 degrees at 15 frames per cardiac cycle during the initial 90% of the cardiac cycle. Compared with the multiview planar technique tomographic ventriculography showed an increased sensitivity for detecting left ventricular segments with significant coronary artery stenosis (97 versus 74%, p less than 0.025) without any loss in specificity. Compared with both planar radionuclide and contrast ventriculography, tomographic radionuclide ventriculography also detected more noninfarcted left ventricular segments supplied by stenosed coronary arteries (81 versus 39 and 32%, respectively, p less than 0.01). Tomographic radionuclide ventriculographic measurements of left ventricular volumes and ejection fraction showed close correlations with angiographic and planar radionuclide determinations. Gated blood pool tomography is a sensitive method for the evaluation of segmental wall motion and an accurate method for the measurement of global left ventricular volumes and ejection fraction.

Three-dimensional motion and perfusion quantification in gated single-photon emission computed tomograms.

Methods for quantification and display of left ventricular (LV) functional parameters from gated single-photon emission computed tomographs are described. Using previously documented surface detection methods, we developed techniques for calculating global variables, such as volumes and areas, as well as local variables such as segmental motion and local perfusion from gated tomographic radionuclide ventriculograms (TRVG) and gated perfusion tomograms (sestamibi). We have developed three-dimensional displays to allow realistic visualizations of the results. The motion results have been validated using correlative magnetic resonance imaging (MRI) studies; motion calculated from user-traced MR images of the heart was compared to motion calculated from automatically detected surfaces in TRVG and sestamibi. The average motion error was calculated to be 0.67 mm in TRVG and -0.21 mm in sestamibi. Errors were largest in basal LV regions; we explain this phenomenon using simulations. Finally, we present additional examples of the analysis using studies obtained from normal volunteers and from subjects whose coronary artery anatomies were known.

Quantification of three-dimensional left ventricular segmental wall motion and volumes from gated tomographic radionuclide ventriculograms.

Tomographic radionuclide ventriculograms may be used for three-dimensional wall motion analysis. We propose that automatic quantification of these images is possible, and here we describe the implementation and validation of a method to perform this task. Automatic computer methods were developed to locate the left ventricular (LV) endocardial surfaces in all time frames of the cardiac cycle. Global, regional, and local motion and volume were computed. Results were displayed using three-dimensional graphics. The methods were validated using phantom, canine, and human studies. Actual phantom values correlated well with experimentally determined volumes, y = 1.01x + 1.29ml, r = 0.99. In the canine model, the LV endocardial surfaces were located to within an average of 1.9 mm and 3.7 mm at end-diastole and end-systole, respectively. Areas of obvious wall motion abnormalities in automatically processed patient studies corresponded well with angiographically documented coronary artery disease. End-diastolic and end-systolic volumes computed automatically from single photon emission computed tomography averaged errors of 9% and 38%, respectively, when compared with contrast ventriculographic volumes. These results indicate that it is possible to automatically identify the left ventricular endocardial surface in gated tomographic radionuclide ventriculograms. The location of these surfaces corresponds well with the location of implanted endocardial markers, and global volume computed from these surfaces corresponds well with known volumes.

Quantitation of postexercise lung thallium-201 uptake during single photon emission computed tomography.

To test the hypothesis that analysis of lung thallium uptake measured during single photon emission computed tomography (SPECT) yields supplementary clinical information as reported for planar imaging, quantitative analysis of lung thallium uptake following maximal exercise was performed in 40 clinically normal subjects (Group 1) and 15 angiographically normal subjects (Group 2). Lung thallium uptake was measured from anterior projection images using a ratio of heart-to-lung activities. Seventy subjects with coronary artery disease (CAD) (Group 3) determined by angiography (greater than or equal to 70% luminal stenosis) underwent thallium perfusion SPECT. Thirty-nine percent of these subjects had multivessel and 61% had single vessel CAD. Lung thallium uptake was elevated in 47 of 70 (67%) Group 3 subjects. Group 3 subjects with elevated lung thallium uptake did not differ from Group 3 subjects with normal lung thallium uptake with respect to extent or distribution of coronary artery disease, left ventricular function, or severity of myocardial ischemia as determined by exercise and redistribution thallium SPECT. Thus, the measurement of thallium lung uptake from anterior projection images obtained during SPECT frequently identifies patients with CAD, but it may not provide supplementary information regarding the extent of myocardial ischemia or ventricular dysfunction.

Estimation of jeopardized left ventricular myocardium in symptomatic and silent ischemia as determined by iodine-123 phenylpentadecanoic acid rotational tomography.

Whether patients with silent myocardial ischemia have a lesser mass of ischemic myocardium than patients with symptomatic ischemia is controversial. Forty-five patients with angiographic coronary artery disease (greater than or equal to 70% luminal diameter narrowing) were studied. All patients had ischemic patterns of myocardial uptake and clearance of the long-chain fatty acid perfusion/metabolic imaging agent iodine-123 phenylpentadecanoic acid after maximal exercise. Single-photon emission computed tomography was performed and 25 myocardial segments were analyzed using circumferential activity profile curves. The 21 patients with silent treadmill ischemia exercised longer than the 24 patients with painful treadmill ischemia (430 +/- 137 vs 337 +/- 96 seconds, p less than 0.01) and to a higher heart rate (138 +/- 21 vs 125 +/- 18 beats/min, p less than 0.05). Patients with treadmill silent ischemia had the same number of abnormally perfused myocardial segments as patients with painful treadmill ischemia (8.6 +/- 4.5 vs 6.5 +/- 4.1 segments, difference not significant) and the same number of reversibly ischemic myocardial segments (4.0 +/- 1.4 vs 4.2 +/- 3.0 segments, difference not significant). The angiographic severity and extent of coronary artery disease were similar in the 2 groups. Thus, in this selected group of patients, those with silent treadmill ischemia appear to have at least as great an extent of ischemic myocardium as patients with painful exertional ischemia.

Abnormal myocardial fatty acid metabolism in dilated cardiomyopathy detected by iodine-123 phenylpentadecanoic acid and tomographic imaging.

The radioidinated synthetic fatty acid iodine-123 phenylpentadecanoic acid (IPPA) has proven useful in the identification of regional abnormalities of cardiac metabolism in patients with myocardial ischemia. The present study was performed to test the hypothesis that the myocardial distribution and turnover of fatty acids, assessed noninvasively with IPPA, are altered in patients with cardiomyopathy. Nine normal volunteers and 19 patients with dilated cardiomyopathy of various etiologies underwent cardiac imaging with single-photon emission computed tomography (SPECT) after intravenous injection of IPPA. Apical short-axis and basal short-axis sections were reconstructed and quantitatively analyzed for relative IPPA activity distribution and washout. Patients with congestive cardiomyopathy demonstrated significantly greater heterogeneity of IPPA uptake than normal subjects (maximal percent variation of activity 27 +/- 11 vs 18 +/- 4, p less than 0.01). They also demonstrated a more rapid percent washout rate than control subjects (24 +/- 8 vs 17 +/- 6 for the apical short-axis section, p less than 0.05; 26 +/- 7 vs 18 +/- 5 for the basal short-axis section, p less than 0.01). These abnormalities of fatty acid distribution and turnover were independent of the etiology of the cardiomyopathy. The degree of heterogeneity of IPPA uptake was significantly related to the patients' New York Heart Association functional class (r = 0.64, p less than 0.01). Thus, compared with normal myocardium, the myocardium of patients with congestive cardiomyopathy demonstrates a more heterogeneous distribution of fatty acid uptake, which parallels the clinical severity of the disease. Furthermore, patients with congestive cardiomyopathy demonstrate a more rapid myocardial clearance of the labeled fatty acid, as assessed with SPECT imaging.

Regional cardiac adrenergic function using I-123 meta-iodobenzylguanidine tomographic imaging after acute myocardial infarction.

The effect of acute myocardial infarction (AMI) on regional cardiac adrenergic function was studied in 27 patients mean +/- standard deviation 10 +/- 4 days after AMI. Regional adrenergic function was evaluated noninvasively with I-123 meta-iodobenzylguanidine (MIBG) using a dedicated 3-detector tomograph. Four hours after its administration, there was reduced MIBG uptake in the region of infarction, 0.38 +/- 0.31 counts/pixel/mCi x 103 compared with 0.60 +/- 0.30 counts/pixel/mCi x 103 and 0.92 +/- 0.35 counts/pixel/mCi x 103 in the zones bordering and distant from the infarct area, respectively, p less than 0.001. In all patients, the area of reduced MIBG uptake after 4 hours was more extensive that the associated thallium-201 perfusion defect with defect scores of 52 +/- 22 and 23 +/- 18%, respectively, p less than 0.001. After anterior wall AMI, the 4-hour MIBG defect score was 70 +/- 13% and the degree of mismatch between myocardial perfusion and MIBG uptake was 30 +/- 9% compared with 39 +/- 17 and 21 +/- 17% after inferior AMI, p less than 0.001 and p = 0.016, respectively. The 4-hour MIBG defect score correlated inversely with the predischarge left ventricular ejection fraction, r = -0.73, p less than 0.001. Patients with ventricular arrhythmia of greater than or equal to 1 ventricular premature complexes per hour, paired ventricular premature complexes or ventricular tachycardia detected during the late hospital phase had higher 4-hour MIBG defect scores, 62.5 +/- 15.0%, than patients with no detectable complex ventricular ectopic activity and a ventricular premature complex frequency of less than 1 per hour, 44.6 +/- 23.4%, p = 0.036.(ABSTRACT TRUNCATED AT 250 WORDS)

Quantitative rotational tomography with 201Tl and 99mTc 2-methoxy-isobutyl-isonitrile. A direct comparison in normal individuals and patients with coronary artery disease.

We tested the hypothesis that 99mTc 2-methoxy-isobutyl-isonitrile (99mTc MIBI), a new radiopharmaceutical for myocardial perfusion imaging, provides accurate noninvasive detection of coronary artery disease (CAD). Imaging in patients after exercise and at rest with 99mTc MIBI was compared with imaging after exercise and redistribution with 201Tl in 12 normal subjects and 38 patients with angiographic documentation of CAD (greater than or equal to 50% diameter stenosis). We used single-photon emission computed tomography (SPECT) and computer quantitation of regional tracer distribution. The quality of reconstructed images with 99mTc MIBI judged visually was superior to that of 201Tl in 88% of all studies performed and was comparable in the others. With the limits of normal as 2.5 SD below the mean of gender-matched normal volunteers, 201Tl SPECT identified 32 and 99mTc MIBI identified 36 patients with CAD (p = 0.2). 201Tl SPECT identified 45 of 75 (60%) and 99mTc MIBI identified 59 of 75 (79%) stenosed coronary arteries (p less than 0.05). The quantitative severity of perfusion defects was similar for the two tracers. 201Tl SPECT identified 104 reversibly ischemic myocardial segments compared with 134 with 99mTc MIBI (p less than 0.05). Thus, SPECT myocardial perfusion imaging with 99mTc MIBI and computer quantitation provides an accurate method for the noninvasive detection of significant coronary artery disease. Furthermore, image quality is generally superior to 201Tl, and reversibly ischemic myocardial segments may be better identified with 99mTc MIBI.

Abnormal I-123 metaiodobenzylguanidine myocardial washout and distribution may reflect myocardial adrenergic derangement in patients with congestive cardiomyopathy.

I-123 metaiodobenzylguanidine (MIBG) is a new radiopharmaceutical with properties that allow the characterization of the sympathetic innervation of several organ systems. In this study, we used MIBG with tomographic imaging to evaluate noninvasively the differences in myocardial sympathetic innervation in 14 healthy volunteers and 16 patients with severe dilated cardiomyopathy (CM). Initial (15-minute) images demonstrated no significant differences in MIBG concentration in the hearts of patients with CM and of healthy volunteers. However, the myocardial retention of MIBG was significantly reduced in the patients with CM. Expressed as the percent washout from 15 to 85 minutes, the patients with CM had a 28 +/- 12% washout rate compared with 6 +/- 8% in the controls (p less than 0.001). A small subset of patients from each group imaged at 4-hour intervals demonstrated even greater disparity in washout rates. In addition, the patients with CM had significantly greater heterogeneity in the MIBG activity distribution within the myocardial images. There was 47 +/- 15% intraimage variability in MIBG distribution in the patients with CM and 22 +/- 9% variation in the controls (p less than 0.001). We conclude from these data that the myocardial distribution and kinetics of MIBG in images obtained from patients with CM differ significantly from those of controls and that the MIBG patterns may be used as a relatively noninvasive means to evaluate the severity of altered adrenergic innervation in the hearts of these patients.

Development and prospective application of quantitative 2-day stress-rest Tc-99m methoxy isobutyl isonitrile SPECT for the diagnosis of coronary artery disease.

The clinical diagnostic accuracy of 2-day stress/rest quantitative Technetium-99m (Tc-99m) methoxy-isobutyl-isonitrile (Tc-sestamibi) single photon emission computerized tomography (SPECT) was assessed in a validation population of 61 patients from two different sites using two different camera/computer systems. The study population was made up of 53 catheterized patients, 29 from Cedars-Sinai Medical Center (CSMC) and 24 from the University of Texas Southwestern Medical Center (UTSMC), and eight UTSMC patients with a less than 5% pre-test likelihood of coronary artery disease. Interpretation employed gender-specific normal limits developed in an additional 15 men and 8 women at CSMC with less than a 5% likelihood of significant coronary artery disease. The results from CSMC compared with those from UTSMC were not different from each other. The overall sensitivity for detection of patients with coronary artery disease (greater than or equal to 50% stenosis) was 94% (CSMC: 92%, UTSMC: 95%). Overall specificity in the five patients with normal coronary arteriograms was 80% (CSMC: 67%, UTSMC: 100%). The normalcy rate in patients with a low likelihood of coronary artery disease was 88%. Vessel sensitivity was 85% (CSMC: 84%, UTSMC: 85%), while vessel specificity was 71% (CSMC: 72%, UTSMC: 69%). There was also no significant difference in the sensitivities and specificities between male and female populations. In addition, the agreement with coronary angiography for assessment of disease extent (normal coronary arteriogram, single or multivessel disease) was 75% (kappa = 0.6 +/- 0.1). This study demonstrated that Tc-sestamibi SPECT by quantitative analysis is accurate for the detection and localization of coronary artery disease. Furthermore, the CSMC quantitative method was shown to provide similar diagnostic accuracy when applied to data acquired at a different site using a different camera/computer system.