Gated Blood Pool Imaging Research Articles

Gated cardiac blood pool studies in atrial fibrillation: role of cycle length windowing

Cycle length windowing is gaining increasing acceptance in gated blood pool imaging of patients with atrial fibrillation (AF). The goals of this study were: to assess differences of ejection fraction (EF) in AF with and without windowing and to determine how EF varied with cycle length in patients with AF. Twenty patients with AF were prospectively studied by gated blood pool imaging, with simultaneous collection in each patient of 5-7 studies with cycle length windows spanning the cycle length histogram. Each window accepted beats of only a narrow range of cycle lengths. EF was determined for each of the narrow cycle length windows as well as for the entire gated blood pool study without cycle length windowing. For every patient an average of the windowed EFs was compared with the non-windowed EF. EF values were similar (mean windowed: 46.6; non-windowed: 45.5; P = 0.16), and there was a good correlation between the two techniques (r = 0.97). The data were then examined for a relationship of EF with cycle length. The difference from average windowed EF (delta EF) was calculated for each window and plotted vs. the cycle length of the center of each window. No predictable linear or nonlinear relationship of delta EF with window position was observed. Lack of predictable variation of EF with cycle length is likely due to lack of a predictable amount of ventricular filling for a given cycle length, as the amount of diastolic filling in AF depends on the random cycle length of the preceding beat.(ABSTRACT TRUNCATED AT 250 WORDS)

Reduction in ST segment elevation after thrombolysis predicts either coronary reperfusion or preservation of left ventricular function.

The usefulness of a reduction in ST segment elevation to predict coronary reperfusion in myocardial infarction remains uncertain. ST segment changes and angiographic findings were compared in 45 patients soon after thrombolysis. The percentage ST segment change 3 hours after treatment (in the lead showing the greatest initial ST elevation) was compared with the TIMI perfusion grade (thrombolysis in myocardial infarction trial) obtained between 90 minutes and 3 hours after treatment. Global ejection fraction and regional wall motion were assessed by cineventriculography (11 (5) days (mean (SD))) and by gated blood pool imaging (44 (11) days). Prediction of coronary patency by a reduction of greater than 25% in ST segment elevation 3 hours after thrombolytic treatment had a sensitivity of 97% but a specificity of only 43%. Where the ST segment elevation was reduced by greater than 25% the global ejection fraction was well maintained whether or not the infarct vessel was patent. In patients with a reduction of less than 25% in ST elevation, the ejection fraction was significantly lower and regional wall motion abnormality more severe. Reduction in ST elevation of greater than 25% within 3 hours of thrombolysis indicates either a patent infarct artery or preservation of left ventricular function. When the ST segment elevation does not fall by greater than 25% persistent coronary occlusion is likely (predictive accuracy 86%) and is associated with a lower ejection fraction. These patients may benefit from further treatment or additional interventions.

Assessment of Mitral Regurgitation Using Gated Radionuclide Ventriculography: Analysis of Left Atrial Time Activity Curve

The authors analyzed the left atrial (LA) time activity curve (TAC) in 18 normal subjects and 30 patients with mitral regurgitation (MR) to assess the usefulness of radionuclide ventriculography (RNV) in detecting MR. The LA TAC was generated from gated blood pool images using phase and amplitude images. The configuration of normal LA TAC was M shaped. The first peak and last peak of LA TAC were represented as points B and D, respectively. In addition, the trough following B was named point C. The presence and severity of MR was analyzed by use of three methods: (1) analysis of LA TAC, (2) analysis of left ventricular TAC, and (3) measurement of the stroke count ratio of left ventricle to right ventricle. In the diagnosis of MR using RNV, the rapid emptying fraction [REF:(B-C)/(B-A)] of LA TAC was the most sensitive index compared with the other two methods. The sensitivity and specificity of MR with Sellers' II degrees or more were 0.84 and 0.90 in LA TAC but were 0.42 and 0.90 in the count method.

Sustained improvement in left ventricular function after successful coronary angioplasty.

The short and long term effects of successful percutaneous transluminal coronary angioplasty on left ventricular function, at rest and on exercise were investigated in 49 patients. Thirty-four had had no previous infarction (group 1) and 15 had (group 2). Technetium-99m gated blood pool images were obtained at rest and during exercise before, six weeks after, and a mean of fifteen months after successful angioplasty. Before angioplasty the mean (SD) ejection fraction fell significantly on exercise in both groups from 58 (10)% to 53 (13)% in group 1 and from 48 (10)% to 40 (16)% in group 2. This change was paralleled by a worsening wall motion score (from 0.6 (0.4) to 1.6 (1.2) in group 1 and from 2.3 (1.9) to 3.3 (2.4) in group 2). Six weeks after the procedure there was little change in resting ejection fraction but it increased significantly on exercise (to 62 (11)% in group 1 and to 53 (13)% in group 2). There was a concomitant significant improvement in the exercise wall motion score (to 0.4 (0.6) in group 1 and to 1.8 (1.1) in group 2). This improvement in exercise ejection fraction and wall motion was maintained at later follow up with no significant deterioration in either variable and a clearly sustained improvement in ejection fraction (60 (10)% in group 1 and 51 (10)% in group 2) and wall motion score (0.2 (0.2) in group 1 and 1.3 (0.8) in group 2) compared with values before angioplasty. The initial improvement in left ventricular function on exercise after successful angioplasty was maintained for at least 9-24 months both in patients with previous myocardial infarction and in those without.

Gated blood pool tomography: A technology whose time has come

Tomographic gated blood pool imaging is a natural extension of the technologies of planar gated blood pool scanning and rotating Anger camera single photon emission computed tomography (SPECT). The high photon flux, optimum 140 keV energy, and volume sampling of tomography permit reconstruction of the data in any perspective. The true three-dimensional nature of this process allows the evaluation of regional wall motion of all the cardiac chambers, unencumbered by overlapping structures. The heart can be viewed from any angle, including a long axis, short axis, apical four chamber, and a true inferior view. In addition to evaluation of regional wall motion, precise determination of chamber volumes and ejection fractions is possible. Early clinical experience has demonstrated the superiority of tomographic gated blood pool imaging over planar blood pool imaging for precisely defining subtle functional abnormalities. The enormous amount of data generated by this procedure taxes the capacity of most nuclear medicine computer systems. However, the availability of 32-bit processors and large amounts of image memory in new machines should ultimately reduce this processing time to less than ten minutes. The combination of complete visualization and quantitation suggests that a renaissance for blood pool imaging is on the horizon.

Acute left ventricular dysfunction during unsuccessful weaning from mechanical ventilation.

The authors studied the hemodynamic effects of rapidly weaning from mechanical ventilation (MV) 15 patients with severe chronic obstructive pulmonary disease (COPD) and cardiovascular disease who were recovering from acute cardiopulmonary decompensation. In each patient, 10 min of spontaneous ventilation (SV) with supplemental oxygen resulted in reducing the mean esophageal pressure (X +/- SD, + 5 +/- 3 to -2 +/- 2.5 mmHg, P less than .01) and increasing cardiac index (CI) 3.2 +/- 0.9 to 4.3 +/- 1.3 1/min/M2, P less than .001), systemic blood pressure (BP 77 +/- 12 to 90 +/- 11 mmHg, P less than .001), heart rate (HR 97 +/- 12 to 112 +/- 16 beats/min, P less than .001), and, most importantly, transmural pulmonary artery occlusion pressure markedly increased (PAOPtm 8 +/- 5 to 25 +/- 13 mmHg, P less than .001), mandating a reinstitution of MV. In four patients with left ventricular (LV) catheters, the PAOP correlated with the LV end-diastolic pressure during both MV and SV. Gated blood pool imaging showed SV increased the LV end-diastolic volume index (65 +/- 24 to 83 +/- 32/M2, P less than .002) with LV ejection fraction unchanged. Patients were treated for a mean of 10 days with diuretics, resulting in a reduction of blood volume (4.55 +/- 0.9 1 to 3.56 +/- 0.55 1) and body weight (-5 kg, P less than .001). Subsequently, nine of the 15 patients were weaned successfully from mechanical ventilation with unchanged PAOP.

Prolonged PR interval associated with an abnormal frontal plane QRS axis as an electrocardiographic criterion of left ventricular function

The aim of this study was to investigate whether, in patients who had had one or more myocardial infarctions, the electrocardiographic appearances of prolonged PR interval associated with an abnormal frontal plane QRS axis are correlated with the value of left ventricular ejection fraction. Seventy-three consecutive patients all of whom had had at least one myocardial infarction, were divided into 3 groups: Group A, 22 patients having on their electrocardiogram a prolonged PR interval and an abnormal frontal plane QRS axis; Group B, 15 patients having an abnormal QRS axis as a solitary conduction disturbance; and Group C, 36 patients without conduction abnormalities. The ejection fraction, determined in all patients by gated blood pool imaging, was found to be 30% ± 8 (mean ± 1 SD) in Group A, 53% ± 21 in Group B, and 52% ± 14 in Group C ( P < 0.001). An ejection fraction of less than 40% was found in 91% of patients in Group A, in 33.33% in Group B, and in 8.33% in Group C ( P < 0.01). Multiple segment ventricular wall contraction abnormalities were found in 50, 6.66, and 11.11%, respectively ( P < 0.001). It can be presumed, therefore, that in patients after one or more myocardial infarctions, this association of conduction abnormalities signifies a severe impairment of ventricular contractility and may identify a subgroup with a high prevalence of severely depressed ejection fraction.

The role of ischemia and ventricular asynergy in the genesis of exercise‐induced ST elevation

Sixty-five patients with ST elevation were retrospectively studied in order to evaluate the clinical significance and underlying mechanisms of ST-segment elevation during exercise. Of these, 50 patients had previous myocardial infarction (Group I) and 15 patients did not (Group II). Exercise thallium-201 imaging was performed on 30 patients, resting gated blood pool imaging was performed on 33 patients, and 23 underwent cardiac catheterization for clinical indications. When the two groups were compared, patients in Group I had more frequent multivessel disease (9/13 vs. 3/10, p less than 0.05), anterior infarctions (33/50 vs. 4/10, p less than 0.02), while Group II patients had more frequent single-vessel disease (7/10 vs. 4/13, p less than 0.05). For Group I patients, the most common reason for termination of exercise was fatigue and/or dyspnea (35/50 vs. 0/15, p less than 0.05), with an irreversible defect noted in both stress and delayed views on thallium imaging (20/24 vs. 1/6, p less than 0.05). In Group II, the most common reason for termination was angina (15/15 vs. 2/50, p less than 0.001), with reversible thallium defects noted more frequently (4/6 vs. 3/24, p less than 0.01). Thus, we conclude that in patients with Q waves, left ventricular dysfunction rather than ischemia is the mechanism for ST elevation. In these patients angina is rare, but fatigue, dyspnea, multivessel disease, and fixed thallium defects are common. In patients with non-Q-wave exertional ST elevation, ischemia is the rule, manifested by frequent chest pain and reversible thallium defects.

｀９９ｍ´Ｔｃ標識ジエチレントリアミン五酢酸‐ヒト血清アルブミン（ＤＴＰＡ‐ＨＳＡ）による左室機能測定

A newly developed blood pool agent 99mTc-DTPA-HSA (Japan Mediphysics, Inc.) was used for ECG gated blood pool scintigraphy. The radiopharmaceutical remained in the blood pool with disappearance half time of 420 min in a healthy subject. The gated blood pool study in the same subject clearly demonstrated contracting left ventricle and right ventricle both with planar and SPECT images. Three healthy volunteers and 14 patients were included in the study, in that gated blood pool images were successfully obtained. The left ventricular ejection fraction (LVEF) calculated by the analysis of LV volume curves correlated well with those obtained by echocardiography (US). In 11 patients with implanted pacemaker for complete atrioventricular block and sick sinus syndrome changes of LVEF were evaluated in relation to pacing rates. The mean LVEF at pacing rate of 60/min was 58.5%, which decreased to 54.4% at 100/min pacing rate. However, changes of LVEF in individual patient did not show same pattern. We conclude that 99mTc-DTPA-HSA is a convenient blood pool scanning agent which does not require time consuming labeling preparations. Stable labeling and slow blood clearance allows its use for repeat measurements of LVEF in different conditions in a patient such as with pacemaker.

Digitizing and signal averaging of left ventricular pressure signals using a dedicated radionuclide imaging system.

A method for obtaining left ventricular (LV) volume curves, synchronized with average LV pressure (LVP) curves for calculation of LV contractility, is described. Multiple gated blood pool imaging was performed to calculate average LV volume curves. Simultaneously with this acquisition, LVPs and aortic pressures were measured by indwelling catheters and recorded on an FM tape recorder. These signals were fed to the computer as image information and averaged and processed by the software developed for this purpose. Pressure resolution of the calibrated images was 4 mmHg/pixel when provision was made for a maximum pressure of 200 mmHg. A good correlation (r = 0.99) was obtained between the calculated peak LVPs and mean peak LVPs read from the chart recorder. The regression equation was: digitized peak LVP = 1.04 x chart recording--5.11 mmHg and the standard error of the estimate was 2.9 mmHg. Similar results were obtained with the aortic pressure (AP) measurements (digitized AP = 0.94 x chart recording + 6.37 mmHg, the standard error of the estimate was 3.8 mmHg). The digitized data also allowed the construction of pressure-volume loops for interpretation of ventricular contractility.

Evaluation of myocardial perfusion and function by single photon emission computed tomography

Although planar radionuclide techniques provide accurate, noninvasive measurements of myocardial perfusion and function that are of proven clinical value in the evaluation of the cardiac patient, they are limited by poor object contrast and superimposition of surrounding structures. Due to incomplete angular sampling and significant longitudinal distortion, limited angle tomography did not solve these problems. Single photon emission computed tomography (SPECT) can acquire scintillation information over very small angles of rotation and, thus, improve both object contrast and delineation of overlying or adjacent structures without distortion. The early SPECT systems were cumbersome, dependent on individual user developed software, and had extremely long acquisition and processing time. Improved camera design, new software algorithms, and the use of array processors have simplified and standardized quality control, decreased processing time, and minimized the number of user interventions. New image display formats and quantitative methods of analysis have made interpretation less cumbersome, more reliable and highly reproducible. Cardiac SPECT has been used with thallium-201 and gated blood pool imaging in both research and clinical applications and shown an improvement over planar methods of acquisition.

Atrial kinetics and left ventricular diastolic filling in the healthy elderly

A delay of left ventricular isovolumic relaxation and decrease in myocardial compliance may result in a decline of measured early filling rates in elderly subjects. Previous studies of diastolic function, however, have not excluded coronary artery disease or addressed the contribution of atrial contraction to diastole. The present study evaluated radionuclide-derived diastolic variables in 13 healthy elderly volunteers aged 75 +/- 6 years without symptoms or risk factors for coronary disease who had normal findings on the stress electrocardiogram, stress gated blood pool imaging and two-dimensional echocardiogram. Results were compared with those of a group of 10 healthy young volunteers aged 26 +/- 5 years. High count, 32 frame, double-buffered gated blood pool acquisitions were obtained at rest in the left anterior oblique view with an RR interval variation less than 5%. Left ventricular time-activity curves were analyzed and flow-volume loops for each group were constructed. In the healthy elderly: peak early diastolic filling rate is decreased, time of peak early filling and time to first third of diastolic filling are delayed, and peak late left ventricular filling rate and percent of atrial filling volume are augmented, suggesting an adaptive response of the atria to diminished left ventricular compliance.

Inotropic effect of enoximone in patients with severe heart failure: Demonstration by left ventricular end-systolic pressure-volume analysis

Left ventricular end-systolic pressure-volume analysis was employed to assess the inotropic effect of the phosphodiesterase inhibitor enoximone (formerly MDL-17,043) in nine patients with severe heart failure (New York Heart Association class IV symptoms, mean ejection fraction = 0.22). Left ventricular pressure-volume loops were constructed using high fidelity left ventricular pressure measured with micromanometer-tipped catheters and simultaneous left ventricular volume obtained by gated blood pool imaging. Afterload was reduced with the vasodilator nitroprusside to generate the baseline left ventricular end-systolic pressure-volume relation, a relatively load-independent measure of contractile function. The intravenous administration of enoximone (mean dose 75 mg) shifted the end-systolic pressure-volume point upward and leftward from the baseline pressure-volume relation in eight of the nine patients, demonstrating a positive inotropic effect of this agent. The maximal rate of left ventricular pressure development (peak positive dP/dt) increased from 1,030 +/- 142 to 1,381 +/- 219 mm Hg/s (p less than 0.01) on enoximone despite a significant decrease in preload (as assessed by left ventricular end-diastolic pressure and volume) and a small, insignificant decrease in mean arterial pressure. Two patients developed angina after enoximone administration; both patients had coronary artery disease and experienced a greater than 30% increase in heart rate-systolic blood pressure product. Thus, enoximone has a significant inotropic effect in patients with severe heart failure. Like other inotropic drugs, it has the potential to increase myocardial oxygen demand and thereby precipitate ischemia.

Pharmacologic intervention as an alternative to exercise stress

Although thallium exercise imaging has served an important role in clinical cardiology, it is significantly limited by suboptimal sensitivity and specificity, particularly in asymptomatic man. The increasing recognition of silent myocardial ischemia, the significant prevalence of coronary artery disease in asymptomatic middle age men, and the frequent occurrence of myocardial infarction without preceding symptoms in 60% of cases emphasizes the need for a more definitive, noninvasive diagnostic test for the presence of coronary artery disease suitable for screening in asymptomatic or symptomatic patients. Intravenous dipyridamole combined with handgrip stress provides a potent stimulus for purposes of diagnostic perfusion imaging. Although planar and single photon emission computed tomography (SPECT) imaging also have played an important role, these techniques are seriously hindered by their inability to quantitate radiotracer uptake or image modest differences in maximum relative flow caused by coronary artery stenosis. Accordingly, the combination of dipyridamole-handgrip stress with positron imaging of myocardial perfusion has become a powerful diagnostic tool suitable for routine clinical use. With the availability of generator-produced rubidium-82, dedicated clinically oriented positron cameras, the routine application of positron imaging to clinical cardiology has become feasible. Based on published literature, the current clinical indications for positron imaging that may be carried out economically on a routine clinical basis include assessment of myocardial perfusion utilizing rubidium-82 or N-13 ammonia for purposes of reliable, accurate, noninvasive screening for coronary artery disease in symptomatic or asymptomatic patients; assessing noninvasively the physiologic severity of coronary stenoses; myocardial infarct imaging; assessing myocardial viability of reversibly injured or ischemic cells using N-13 ammonia combined with fluorine-18-deoxy-glucose or Rubidium-82 alone in experimental animals; assessing regional or global left ventricle (LV) function by 3-dimensional gated blood pool imaging and/or wall thickening by ECG gating; and assessing the functional significance of collaterals in man.

Abnormalities of the ascending aorta detected by gated blood pool imaging.

Radionuclide angiography has been used for visualization of aortic arch pathology. Gated blood pool scintigraphy generally has been reserved for the evaluation of ventricular function. By observing the aorta in relation to other cardiac structures, additional information about relative size and shape is available, and can be integrated with ventriculographic observations. This may enhance understanding of the mechanism of disease in the individual patient. Five selected case histories illustrating this point are presented. The last example demonstrates the ability of the technique to uncover unsuspected thoracic aorta pathologic findings. The sensitivity and specificity of this technique to diagnose aortic disease requires further study.

Measurement of left ventricular volume using single-photon emission computed tomography

A count-based method for measuring left ventricular (LV) volume using technetium-99m-labeled red cells and ungated single-photon emission computed tomography is described. The tomographic slices were used to determine the counts per milliliter in the center of the left ventricle and total LV counts, which were used to derive mean LV volume. End-diastolic and end-systolic volumes were calculated from the mean volume using the LV time-activity curve from planar gated blood pool images. Phantom evaluation with simulated LV volumes (50 to 400 ml) in air, in a phantom filled with water, with 10% background, and with a simulated right ventricle, showed excellent accuracy. For clinical validation, 30 patients underwent electrocardiographically gated planar and nongated tomographic acquisition of the cardiac blood pool followed by single-plane cineangiography. For end-diastolic and end-systolic volumes combined, the correlation with cineangiography showed a standard error of the estimate (SEE) of 24 ml and 14 ml, respectively. Mean intra- and interobserver deviation was 12 ml and 14 ml (SEE 13 ml and 16 ml), respectively. It is concluded that this noninvasive count-based technique, requiring no assumptions regarding LV geometry, is an accurate and reproducible way to measure LV volume.

Long-term follow-up after intracoronary streptokinase therapy for acute myocardial infarction

This article describes the effects on patients treated with intracoronary streptokinase during acute myocardial infarction and long-term follow-up. The mortality and the incidence of cardiac events were assessed during a follow-up period of 35 ± 5 months. Coronary artery bypass grafting was undertaken in 37% of the patients. Hospital mortality was 11%, (n = 8); none of these deaths was due to myocardial rupture. The postdischarge mortality was 10%; three of these patients experienced sudden death. Serial assessment of left ventricular function in 35 patients showed an increase of angiographic ejection fraction prior to intervention from 50 ± 4% to 58 ± 12% ( p = 0.005) 36 ± 53 days later. Gated-blood pool imaging after 16 ± 7 months (n = 35) and 32 ± 9 months (n = 31) revealed no change in ejection fraction. Angina pectoris recurred in four of the 35 patients. We studied a historical comparison group, that consisted of 66 patients, who were treated at the same institution prior to the advent of intracoronary intervention techniques; this group was followed for 48 ± 9 months. Baseline clinical and angiographic parameters were comparable in the two groups. Coronary artery bypass grafting was performed in only 18 of these patients. Mortality during hospialization and postdischarge was not significantly different in the two groups. Ejection fraction decreased significantly in the comparison group from the first to the second evaluation and remained unchanged during the follow-up period. We conclude that no major adverse effects were associated with intracoronary streptokinase infusion over a long follow-up period. This may be related to the high frequency of coronary artery bypass surgery following reperfusion.

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.

Right and left ventricular ejection fraction and left ventricular volume changes at rest and during exercise in normal subjects.

The effect of exercise upon right and left ventricular ejection fractions (RVEF and LVEF) as well as the changes upon left ventricular end-diastolic and end-systolic volume indices (LVEDVI and LVESVI) were investigated. Twenty-two normal subjects were studied at rest and during upright submaximal exercise. RVEF was determined using a first-pass method. LVEF was measured using multiple gated blood pool imaging. During the exercise test ECGs remained normal. HR and BP increased significantly (P less than 0.01). RVEF increased from 44% +/- 4 (mean +/- SD) to 60% +/- 6 (P less than 0.001). LVEF increased from 62% +/- 6 to 76 +/- 5 (P less than 0.001). A wider scatter was observed in delta RVEF than in delta LVEF. There was a 14% increase in LVEDV-index and a 14% decrease in LVESV-index (P less than 0.001). A multiple regression analysis with delta RVEF as the dependent variable and delta HR, delta systolic BP, delta LVEF, delta LVEDV-index and LVESV-index as independent variables showed a significant correlation between delta RVEF and delta LVEF and delta systolic BP (P less than 0.05). Our data provide insight into the mechanisms by which the pump performance is increased in normal subjects. The central mechanisms observed are the Starling effect and an increase in contractility of the myocardium. This is connected in the general circulation to an increase in afterload, indicating a redistribution of blood from the vascular beds to the muscles and to the heart.

MEASUREMENT OF LEFT VENTRICULAR VOLUME USING SINGLE PHOTON EMISSION COMPUTED TOMOGRAPHY

A count-based method for measuring left ventricular (LV) volume using technetium-99m-labeled red cells and ungated single-photon emission computed tomography is described. The tomographic slices were used to determine the counts per milliliter in the center of the left ventricle and total LV counts, which were used to derive mean LV volume. End-diastolic and end-systolic volumes were calculated from the mean volume using the LV time-activity curve from planar gated blood pool images. Phantom evaluation with simulated LV volumes (50 to 400 ml) in air, in a phantom filled with water, with 10% background, and with a simulated right ventricle, showed excellent accuracy. For clinical validation, 30 patients underwent electrocardiographically gated planar and nongated tomographic acquisition of the cardiac blood pool followed by single-plane cineangiography. For end-diastolic and end-systolic volumes combined, the correlation with cineangiography showed a standard error of the estimate (SEE) of 24 ml and 14 ml, respectively. Mean intra- and interobserver deviation was 12 ml and 14 ml (SEE 13 ml and 16 ml), respectively. It is concluded that this noninvasive count-based technique, requiring no assumptions regarding LV geometry, is an accurate and reproducible way to measure LV volume.