Comparison of interstudy reproducibility of equilibrium electrocardiography-gated SPECT radionuclide angiography versus planar radionuclide angiography for the quantification of global left ventricular function

BACKGROUND: Electrocardiography-gated single photon emission computed tomography (SPECT) radionuclide angiography (RNA) provides accurate measurement of both left ventricular (LV) ejection fraction (EF) and end-diastolic and end-systolic volumes. In this study we studied the interstudy precision and reliability of SPECT RNA as compared with planar RNA for the measurement of global systolic LV function. METHODS AND RESULTS: The population included 10 patients with chronic coronary artery disease having 2 sets of acquisitions, each consisting of planar and SPECT RNA. SPECT RNA was processed with SPECT-QBS and SPECT-35%. (For SPECT-35%, a manual segmentation method based on the 35% threshold of the maximum LV cavity activity is used to provide estimates of the number of voxels and the activity included in the LV cavity. The calculated LV number of voxels is then used to calculate LV volume measurement. The LV EF is calculated as the ratio of LV end-diastolic and end-systolic activity.) For LV EF, end-diastolic volume, and end-systolic volume, the interstudy precision, as reflected by the correlation coefficient, coefficient of variability, coefficient of repeatability, and within-subject coefficient of variation, and the interstudy reliability, as reflected by the intraclass correlation coefficient, were best with SPECT-35%, followed by planar RNA and then SPECT-QBS, respectively. The sample size needed to objectify a change in a parameter of LV function is lowest with SPECT-35%, followed by planar RNA and then SPECT-QBS, respectively. CONCLUSIONS: The SPECT-35% processing method provides excellent interstudy precision and reliability for LV function measurement. In this aspect it seems to be better than planar RNA and SPECT-QBS. These results need to be confirmed in a larger patient population.     

Validation of a new counts-based gated single photon emission computed tomography method for quantifying left ventricular systolic function: Comparison with equilibrium radionuclide angiography

Background  Because myocardial wall thickness is smaller than the spatial resolution of single photon emission computed tomography (SPECT) imaging, changes in myocardial wall thickness are related to changes in maximum pixel counts via the partial volume effect, allowing for quantification of regional systolic wall thickening. We have developed a new gated SPECT method for computing the global left ventricular ejection fraction (LVEF) based entirely on changes in maximum regional myocardial counts during systolic contraction. This new method is independent of endocardial edge detection or other geometric measurements. Methods and Results  In 23 patients the gated SPECT method was validated by comparison with radionuclide angiography. The correlation between computed LVEFs was excellent (slope=0.97, r=0.91). The measurement of LVEF by gated SPECT was highly reproducible, with minimal intraoperator (slope=0.97, r=0.97) or interoperator (slope=1.00, r=0.97) variability. Measurements of regional thickening indexes were also reproducible, with a mean intraoperator correlation coefficient of 0.89±0.05 (range 0.79 to 0.95) for the 14 myocardial regions. Finally, the measurement of LVEF was not significantly influenced by changes in reconstruction filter parameters over a range of cutoff frequencies from 0.16 to 0.28. Conclusions  This new counts-based gated SPECT method for measuring global left ventricular systolic function correlates well with radionuclide angiography, is highly reproducible, and has theoretic advantages over geometric methods. Supported by a grant from the American Heart Association, Virginia Affiliate, Inc., and by a grant from DuPont Pharma Radiopharmaceuticals, N. Billerica, Mass.     

Quantitative gated single photon emission computed tomography imaging: A counts-based method for display and measurement of regional and global ventricular systolic function

Background. Gated single photon emission computed tomography imaging allows simultaneous determination of myocardial perfusion and function. Quantitative perfusion measurements can be based on regional tracer uptake, but function measurements ordinarily require endocardial and epicardial edge detection, which is problematic because of the inherently low spatial resolution and image noise in single photon emission computed tomography images. This article presents methods for quantification of both function and perfusion that do not require edge detection.Methods and Results. In SPECT imaging the partial volume effect causes changes in myocardial wall thickness to be reflected as changes in pixel counts in pixels representing the myocardial wall. This effect allows an estimation of changes in myocardial wall thickness by comparing pixel counts in end-systolic images with corresponding pixel counts in end-diastolic images. This article first describes a standard method to quantify myocardial perfusion by sampling myocardial tracer activity at rest and stress. The same method is then used to sample tracer activity in diastolic and systolic images. A new method is developed to convert the diastolic and systolic samples into quantitative estimates of regional wall thickening. A method is then developed to convert the regional wall thickening fractions into a global left ventricular ejection fraction. A normal database is presented. Receiver operating characteristic analysis is used to establish normal limits.Conclusion. This method requires no edge detection or geometric boundary estimates. Computer results are presented in a simple and intuitive format, which is uniform for parameters of both perfusion and function. The method is robust and produces relatively few false-positive results.     

Validation of quantitative gated single photon emission computed tomography and an automated scoring system for the assessment of regional left ventricular systolic function

Despite its ability to quantify regional perfusion and function, there is no established method for quantification of regional perfusion and function by myocardial gated single photon emission computed tomography (SPECT). The aim of this study was to establish a quantitative index for regional perfusion and systolic function assessment using gated SPECT. Myocardial SPECT was performed at rest using (99m)Tc sestamibi with 8-frame gating in 62 consecutive patients. In addition to computation of left ventricular ejection fraction (LVEF), a new computerized method for quantifying, displaying and automatically grading regional data was developed. Regional function was quantified as wall motion, regional EF, and imaged based, count based, and normalized per cent wall thickenings (%WTs). Regional perfusion was assessed as a relative per cent peak count. Data were displayed on a 25-segmented polar map and automatically graded with a 5-point scale, and then summed scores were calculated. These quantitative parameters were compared to data from radionuclide ventriculography (RNV) and contrast left ventriculography. Gated SPECT had high reproducibilities for calculating global and regional ejection fractions and %WT indices (r=0.811-0.984, P<0.0001), but measurement of wall motion was less reproducible (r=0.555, SEE=7.9, P<0.011). LVEF estimated by gated SPECT and summed perfusion scores correlated closely (P<0.0001) with angiographic LVEF. Among the summed function indices that correlated closely with LVEF, normalized %WT had the closest correlations with LVEF estimated by RNV (r=0.657, P<0.0001) and by gated SPECT (r=0.778, P<0.0001). Assessment by visual reviewing of cine-mode playback or by normalized %WT had greater overall sensitivity, specificity, and positive and negative predictive values for detecting impaired regional function among the functional parameters: 71%, 79%, 63% and 84% for cine format analysis, and 78%, 73%, 59% and 87% for normalized %WT, respectively. Thus, besides LVEF, quantitative gated SPECT can provide reproducible and reliable quantitative data on regional perfusion and function. Automated summed scores obtained by gated SPECT can reflect integrated abnormalities of regional perfusion and function of the left ventricle. Both visual analyses by cine-mode display and a functional map of normalized wall thickening have greater diagnostic values for detecting regional function deficit related to coronary artery disease.     

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.     

Assessment of right ventricular function using gated blood pool single photon emission computed tomography in inferior myocardial infarction with or without hemodynamically significant right ventricular infarction]

Right ventricular function was assessed using gated blood pool single photon emission computed tomography (GSPECT) in 10 normal subjects and 14 patients with inferior myocardial infarction. Three-dimensional background subtraction was achieved by applying an optimal cut off level. The patient group consisted of 6 patients with definite hemodynamic abnormalities indicative of right ventricular infarction (RVI) and 8 other patients with significant obstructive lesion at the proximal portion of right coronary artery without obvious hemodynamic signs of RVI. Right ventricular regional wall motion abnormalities were demonstrated on GSPECT functional images and the indices of right ventricular function (i.e. the right ventricular ejection fraction (RVEF), the right ventricular peak ejection rate (RVPER) and the right ventricular peak filling rate (RVPFR)) were significantly reduced in the patient group, not only in the patients with definite RVI but also in those without hemodynamic signs of RVI. The present study indicates that inferior infarction is frequently associated with RVI, even in the absence of definite hemodynamic signs, when the proximal portion of right coronary artery is obstructed. It is concluded that GSPECT is reliable for the assessment of right ventricular function and regional wall motion, and is also useful for the diagnosis of RVI.     

Quantitative assessment of right ventricular structural abnormalities by right ventricular polar mapping of single photon emission computed tomogram

The identification of right ventricular (RV) abnormalities is clinically important in the evaluation of arrhythmogenic substrates in right ventricular-originated ventricular tachycardia (RVT). The purpose of this study was to determine the diagnostic benefit of quantitative analysis in RV single photon emission computed tomography (SPECT) imaging with (99m)Tc-tetrofosmin/sestamibi in patients with RVT. Thirty patients with RVT (15 with idiopathic RVT and 15 with arrhythmogenic right ventricular cardiomyopathy (ARVC)) were compared with 27 control subjects (including 11 with right bundle branch block) with regard to the semiquantitative RV uptake score in each of six segments and the quantitative RV extent score in polar coordinate map displays by SPECT imaging. The RV total score and RV extent score were compared with the RV global function. Perfusion abnormalities were more frequently detected (P = 0.0001) in the ARVC group (59/90, 65.6%) than in the idiopathic RVT group (4/90, 4.4%) or controls (1/162, 0.6%). The RV extent score in the ARVC group (53.0 +/- 24.8) was significantly higher than that in the idiopathic RVT group (8.4 +/- 10.1) or controls (1.2 +/- 4.9). The RV extent score correlated well with the regional RV perfusion score (P < 0.0001) and with the RV ejection fraction (P < 0.0001). Non-invasive RV perfusion mapping using a (99m)Tc-labelled tracer is useful for the quantitative evaluation of RV substrates in patients with ARVC.     

Instrumentation and computers for brain single photon emission computed tomography

Cerebral single-photon emission computed tomography (SPECT) requires attention to the instrumentation because of the anatomical location of the head at one end of the body, with a generally narrower diameter than the rest of the body. For a number of years, there have been SPECT units designed especially for head work, as well as general-purpose units that have performed well in imaging the head. The current emphasis on cerebral perfusion, using either agents that wash in and out with blood flow or agents that reflect blood flow in their static distribution, has allowed a concentration on imaging hardware and computer hardware and software for this purpose.     

Coronary angiography and thallium-201 single photon emission computed tomography in single vessel coronary artery disease

Polar presentations of selective coronary angiography and myocardial 201T1 SPECT were compared in 49 patients with single vessel disease. Twenty-six lesions were located in LAD, 8 in LCX and 15 in RCA. Perfusion defects were found within the supply area of 44 stenotic and 20 non-stenotic arteries. 201T1 SPECT detected coronary disease in 45 patients (92%) and the obstructed artery in 44 (90%). Single vessel disease was correctly indicated in 28 patients (57%) where the perfusion defects did not extend significantly outside the area supplied by the stenotic artery. Extensive perfusion defects could be explained by 'collateral steal', myocardial disease, LV aneurysm or spasm in 9 patients (18%). The absence of perfusion defect related to the stenotic artery could be explained by a moderate degree of stenosis or well developed collateral vessels in 5 patients (10%). Proximal LAD lesions resulted in larger perfusion defects than distal.     

Combined exercise radionuclide angiocardiography and single photon emission computed tomography perfusion studies for assessment of coronary artery disease

Although there is widespread use of exercise thallium 201 scintigraphy and radionuclide angiocardiography in patients with coronary artery disease (CAD), little is known about the independence, concordance, or relative importance of these studies in the diagnosis, prognosis, and assessment of the outcome of therapy. The use of both tests in the same patient has been impractical because of the logistic considerations imposed by two exercise tests on separate days, and excessive radiation exposure. New technetium 99m-labeled radiopharmaceuticals with high myocardial extraction now permit the simultaneous assessment of myocardial perfusion (single photon emission computed tomography [SPECT]) and ventricular function (radionuclide angiocardiography [RNA]) during treadmill exercise (exercise tolerance test [ETT]). The ability to perform all three tests during a single exercise session offers a very attractive technique to evaluate patients with CAD. The investigators studied 86 patients with chronic CAD using the same-day perfusion and function protocol combined with treadmill exercise. The results demonstrate good concordance between myocardial perfusion and ventricular function as indicated by a significant correlation between tomographic perfusion defect size and ejection fraction (P less than .0001, R = 0.75 at rest and P less than .0001, R = 0.76 during exercise). Stepwise logistic regression was used to model ETT, RNA, and SPECT variables against the presence of one or more 60% stenoses by quantitative angiography, an end point present in 47 patients. Univariable analysis showed all three tests (ETT, RNA, and SPECT) to be significant predictors of the end points (lambda 2 = 5.1, P less than .05; lambda 2 = 12.5, P less than .001; and lambda 2 = 16.1, P less than .001, respectively). Multivariable analysis demonstrated that SPECT provided more diagnostic information than ETT and RNA (Lambda 2 = 16.1, P less than .001).(ABSTRACT TRUNCATED AT 250 WORDS)     

Accuracy and reproducibility of left ventricular function from quantitative,gated, single photon emission computed tomography using dynamic myocardial phantoms: effect of pre-reconstruction filters

We have investigated the accuracy and reproducibility of left ventricular (LV) functions using quantitative, gated, single photon emission computed tomography (SPECT) software dependent on critical frequencies of pre-reconstruction filters. This study incorporated dynamic myocardial phantoms (myocardial and cone shapes). Gated SPECT of 8-interval sets were pre-filtered with Butterworth filters (critical frequency varying between 0.16 and 1.16 cycles/cm, order 5) and with no filter. Phantoms were repositioned, and SPECT acquisitions were repeated. As the critical frequency increased, the estimated LV volume increased to reach a plateau at the level of the critical frequency, 0.54 cycles/cm. Conversely, the values of ejection fractions, wall motion and wall thickening with different filters which used critical frequency of > or =0.39 cycles/cm remained unchanged. However, LV functions and volumes were underestimated when any pre-reconstruction filter was used. Standard deviations of LV functions after repeated measurements were unaffected by different filters with critical frequencies of > or =0.39 cycles/cm. Standard deviations of LV volume, ejection fraction, wall motion and wall thickening were <2.2 ml, <0.9%, <0.6 mm and <8.7%, respectively. Therefore, with the exception of low critical frequencies, LV functions and volumes were highly reproducible when these routine reconstruction filters were used.     

Retrospective evaluation of single photon emission computed tomography of the liver

Retrospective analysis, including indications for examination, of 335 consecutive liver examinations of adults with single photon emission computed tomography performed at the Karolinska Hospital during the first eight months of 1981 has been carried out. 85.1% of the investigations were performed in tumour patients. This group underwent retrospective evaluation specifically regarding space occupying lesions of the liver with a minimum followup time of 3 years. An adequate follow-up of 87.4% was achieved. The study showed a sensitivity of 82.7% and a specificity of 93.9%. The positive and negative predictive values were 78.2% and 95.4%, respectively. 4.4% of the examinations were regarded as equivocal. Compared to previously reported values for planar liver scintigraphy derived from several different studies, the tomographic technique produced no increase of specificity or positive predictive value but a higher total accuracy, probably due to better clarification of the hepatic anatomy. The false positive, false negative and equivocal diagnoses were analysed and reported.     

Clinical evaluation of single photon emission computed tomography of the brain

Single photon emission computed tomography (ECT) was performed on 67 patients. ECT images were taken with a Shimadzu scintillation camera, LFOV-E, before a delayed scan.Eighteen of 67 patients showed abnormal findings on the ECT images. Fourteen of the 18 had a transmission X-ray CT (TCT) study as well. There were eleven cases with brain metastases, one case each of an old infarction, a skull metastasis, and a surgical wound. Eleven of fortynine ECT-negative patients had a TCT study as well, and intracranial lesions were found in five. The smallest lesion found by ECT was 0.5 cm in diameter on the TCT image and the largest lesion missed by ECT was a tumor in the corpus callosum, measuring 4.2×2.7 cm.As far as the patients who also received TCT study are concerned, both the ECT and the ordinary scan were thought to be equal in sixteen patients and ECT to be superior in seven whereas the ordinary scintigram was superior in two. At present, ECT is considered to be useful when it is used in addition to the ordinary scans.In the field of clinical nuclear medicine, the development of new radiopharmaceuticals which are labeled with single photon emitters and which can show the metabolic activity of the brain is eagerly awaited.