Cardiac Single-photon Emission Tomography Research Articles

Coronary Artery Disease in Women: Lessons Learned from Single-Center SPECT Registry and Future Directions for INOCA Patients.

Background and objectives: Myocardial perfusion imaging with cardiac single-photon emission tomography (SPECT) is widely available for the detection of coronary artery disease (CAD) with high diagnostic and prognostic accuracy for women. A large proportion of symptomatic women with true myocardial perfusion defects in SPECT referred to coronary angiography have an absence of CAD—a condition named INOCA (ischemia with nonobstructive CAD). Additionally, the INOCA endotypes are rarely correctly diagnosed, and therefore, no tailored therapy is prescribed. Materials and methods: The cardiac SPECT for women was performed from 2018 to 2021. Patients with perfusion defect were analyzed according to further prescribed diagnostic tests used to diagnose CAD. According to the diagnostic criteria, patients with INOCA were selected as candidates for invasive microvascular physiology measurements. The correlation was calculated between SPECT results and clinical characteristics, symptoms, and risk factors. Results: A total of 726 women with suspected CAD were analyzed. True myocardial perfusion defects were detected in 125 patients (17.2%). During coronary angiography in 70 (56.0%) women, atherosclerosis in epicardial arteries was not observed. In 17 (20.9%) patients, obstructive CAD was present. Correlation was found between perfusion defect in SPECT and cardiovascular risk factors, including overweight, obesity, arterial hypertension, and dyslipidemia. Women with typical angina were more likely to have INOCA, but with “noncardiac” symptoms—CAD. In total, 68 female patients met three inclusion criteria for INOCA and were selected as candidates for invasive diagnostic testing. Conclusions: The created registry proves the important role of cardiac SPECT and great need for the development of invasively detected physiological measurements. The combination of both interventions could significantly change the future directions for INOCA patients, improving treatment strategies and clinical outcomes, especially knowing the number of risk factors and varying clinical presentation. The study will be continued by performing invasive testing of coronary microvascular function to expand the competence about what is known about INOCA patients.

Prediction of infarct size using two-dimensional speckle tracking echocardiography in acute myocardial infarction.

This study aimed to determine the myocardial damage (infarct size provided by cardiac single-photon emission tomography) in early stages of the infarction using longitudinal strain and rotational parameters of the left ventricle. The study included 66 patients with anterior myocardial infarction (AMI) and 62 patients with inferior myocardial infarction (IMI) who underwent primary percutaneous intervention as well as a control group consisting of 50 healthy subjects. LV rotational parameters based on parasternal short-axis views in basal and apical planes and global longitudinal strain were measured with apical four-chamber, apical two-chamber, and apical long-axis views. There was a significant positive correlation between infarct size and GLPSavg (r=-.55 <.001), GTOR angle (r=-.52, P<.001), apical rotation angle (r=-.40 <.001, and EF (r=-.43, <.001). While cutoff values were GLPSavg: 11.9 (AUC=0.78), GTOR angle: 11.4° (AUC=0.77), apical rotation angle: 7.1° (AUC=0.76) for patients with an infarct size greater than 20%, the cutoff values were GLPSavg: 10.7 (AUC=0.75), GTOR angle: 8.7° (AUC=0.86), apical rotation angle: 4.35° (AUC=0.87) for those with an infarct size greater than 40%. GLPSavg, GTOR angle, and apical rotation angle values may be used to determine the extent of infarction in early post-MI period, thereby allowing precautions to be taken for remodeling in early stages.

Imaging predictive factors and exercise training in CRT patients.

Cardiac resynchronization therapy (CRT) is an established treatment for patients with moderate-to-severe chronic heart failure (CHF) and intraventricular conduction delay, which is identified by a QRS interval of 120msec or more on a 12-lead electrocardiogram (ECG). CRT improved functional capacity, reduced hospitalizations for worsening CHF and increased survival. However, about 30-40% of patients who underwent CRT were non-responders with no clinical or echocardiographic improvement. Imaging parameters for prediction of CRT response have been reviewed. Cardiac magnetic resonance (CMR), recognized as the gold standard to assess viability, has shown to obtain good results regarding quantification of scar burden. CMR-derived measures of mechanical dyssynchrony appear to predict the outcome of CRT, however they have not been externally validated. Nuclear imaging techniques, namely single-photon emission cardiac tomography (SPECT) provide data on scar burden and location, left ventricular (LV) function, LV contraction and mechanical dyssynchrony from a single scan. The presence, location and burden of myocardial scar have been shown to affect response to CRT. However, compared to CMR, the low spatial resolution of scintigraphy might overestimate the scar extent. This problem can be overcome by positron emission tomography (PET). SPECT has also been used to quantify dyssynchrony, using phase analysis. Imaging investigation is ongoing, trying to better identifying CRT non-responders. The combination of ExT in CRT has not been well investigated; however some data show different aerobic exercise modes and intensities can further improve CRT benefits. Data available on the effects of ExT in patients with CRT have been reviewed.

Depressed Exercise Peak Ejection Rate Detected on Ambulatory Radionuclide Monitoring Reflects End-Stage Cardiac Inotropic Reserve and Predicts Mortality in Ischaemic Cardiomyopathy.

BackgroundFifteen patients with ischaemic cardiomyopathy and inducible ischaemia were studied to determine the mechanisms of mortality. Failure of the contractile reserve during daily life activities may reflect a prognostic index.MethodsSingle photon emission cardiac tomography and radionuclide ambulatory monitoring (Vest) data were analysed in all patients with a 7-year follow-up.ResultsAt peak exercise on Vest, the 7 non-survivors (N-SURV) showed worse peak ejection rates (PERs) and ejection fractions (EFs) compared with the 8 survivors (SURV), (2 ± 0.6 vs. 3.3 ± 0.7; end-diastolic volumes (EDVs), P < 0.003), and (34 ± 10% vs. 50 ± 13%; P < 0.02), respectively. However, exercise peak filling rates (PFRs) (1.9 ± 0.6 vs. 2.7 ± 0.9; EDVs/s) and exercise heart rates (HRs), (97 ± 17 vs. 106 ± 10), did not differ between the two groups (P > 0.05). In SURV, exercise PERs, which represented rapid left ventricular (LV) emptying, were significantly correlated with exercise PFRs, representing rapid LV filling, (r = 0.71, P < 0.04) but not in N-SURV (r = 0.66, P > 0.05). Among SURV, the Frank-Starling mechanism was thus preserved but not in N-SURV. Upon Cox analysis, overall LV function parameters, exercise PER was the only predictive measure associated with mortality (b = - 0.018, relative hazard ratio = 0.98, P = 0.02).ConclusionsExercise PER reduced values reflected failure of the Frank-Starling mechanism, the incapacity of the heart to perform rapid contractile adaptations to daily life activities and a poor prognosis.

Comprehensive adenosine stress perfusion MRI defines the etiology of chest pain in the emergency room: Comparison with nuclear stress test

To compare standard of care nuclear SPECT imaging with cardiac magnetic resonance imaging (MRI) for emergency room (ER) patients with chest pain and intermediate probability for coronary artery disease. Thirty-one patients with chest pain, negative electrocardiogram (ECG), and negative cardiac enzymes who underwent cardiac single photon emission tomography (SPECT) within 24 h of ER admission were enrolled. Patients underwent a comprehensive cardiac MRI exam including gated cine imaging, adenosine stress and rest perfusion imaging and delayed enhancement imaging. Patients were followed for 14 +/- 4.7 months. Of 27 patients, 8 (30%) showed subendocardial hypoperfusion on MRI that was not detected on SPECT. These patients had a higher rate of diabetes (P = 0.01) and hypertension (P = 0.01) and a lower global myocardial perfusion reserve (P = 0.01) compared with patients with a normal cardiac MRI (n = 10). Patients with subendocardial hypoperfusion had more risk factors for cardiovascular disease (mean 4.4) compared with patients with a normal MRI (mean 2.5; P = 0.005). During the follow-up period, patients with subendocardial hypoperfusion on stress MRI were more likely to return to the ER with chest pain compared with patients who had a normal cardiac MRI (P = 0.02). Four patients did not finish the MR exam due to claustrophobia. In patients with chest pain, diabetes and hypertension, cardiac stress perfusion MRI identified diffuse subendocardial hypoperfusion defects in the ER setting not seen on cardiac SPECT, which is suspected to reflect microvascular disease.

Experience with Paclitaxel-Eluting Infinnium Coronary Stents

To investigate the safety and efficacy of the Infinnium Paclitaxel-eluting stents in the treatment of coronary artery lesions, 196 patients with symptomatic coronary disease who received 202 stents at our center from January 2004 to November 2005 were studied prospectively. The primary study endpoint was the incidence of abnormalities on exercise electrocardiograms or cardiac single-photon emission tomography at 6 months, as a noninvasive index of stent reocclusion. Secondary endpoints were the rates of major adverse cardiac events at 1, 3, 6, 9, and 12 months. Stent deployment was successful in 98% of patients. Cumulative major adverse cardiac event rates at the end of 12 months were: cardiac death 1%, myocardial infarction 5% (Q-wave 2.5%, non-Q-wave 2.5%), and repeat revascularization of the stented lesion 3%. The overall major adverse cardiac event rate was 8.1%. There were 6 (3%) stent thromboses; all occurred late after the procedure. In patients with symptomatic ischemic heart disease, the low-cost Infinnium stent proved both effective and safe, with an acceptably low major adverse cardiac event rate.

Hypothermia during reperfusion does not reduce myocardial infarct size in pigs

We previously described a method for regional myocardial cooling that reaches the target temperature within 4 min. The present study evaluated whether this method for regional myocardial cooling during reperfusion reduces myocardial infarct size (IS) in 75-kg pigs. Myocardial infarction was induced by inflation of an angioplasty balloon in the left anterior descendent artery for 45 min followed by 3 h reperfusion. First, 15 pigs were randomized to regional myocardial cooling during reperfusion (n = 8) or control (n = 7). As further control experiments, systemic hypothermia was induced prior to ischemia (n = 3) and during reperfusion (n = 3). IS and area at risk (AAR) were evaluated in vivo by single photon emission cardiac tomography (SPECT) and by standard histochemical staining. Regional cooling during reperfusion did not reduce IS/AAR as assessed by histochemistry (cooling: 0.71 +/- 0.8; control: 0.68 +/- 0.10; p = ns) and SPECT (cooling: 0.90 +/- 0.20; control: 0.88 +/- 0.32; p = ns). Systemic hypothermia during ischemia reduced IS/AAR (histochemistry: 0.09 +/- 0.11; SPECT: 0.25 +/- 0.22; p < 0.001 and p = 0.01 vs control, respectively). Induction of systemic hypothermia during reperfusion had no significant effect on IS/AAR (histochemistry: 0.63 +/- 0.07; SPECT: 0.74 +/- 0.09; p = ns vs control for both comparisons). In conclusion, hypothermia during ischemia is strongly myocardioprotective while hypothermia during reperfusion does not reduce myocardial infarct size in human-sized pigs.

QT dispersion and viable myocardium in patients with prior myocardial infarction and severe left ventricular dysfunction.

QT dispersion (QTd) has been found to correlate to the amount of viable myocardium in patients with Q-wave myocardial infarction and well-preserved LV function. However, this relationship is unknown in patients with severe left ventricular dysfunction. Thirty-four patients with prior large myocardial infarction and severe left ventricular dysfunction underwent Tc-99m sestamibi single photon emission cardiac tomography (SPECT) and F-18 fluorodeoxyglucose (FDG) SPECT. Viability was defined as a defect relative count density (DCD) of at least 20% greater on FDG SPECT. QTd, corrected QT dispersion (QTcd), and QT coefficient of variation (cv) in patients with viable myocardium was compared to those without viable myocardium in the infarct area. Thirteen patients were excluded from analysis for poor FDG images or inadequate ECG tracings. Of the remaining patients, 10 (48%) were found to have viability on FDG SPECT. QTd, QTcd, and QTcv in patients with viability were: 58 +/- 22 ms, 61 +/- 23 ms, and 4.81 +/- 1.76%, respectively, which did not differ significantly from those in patients without viability (QTd = 56 +/- 14 ms, QTcd = 70 +/- 16 ms and Qtcv = 5.06 +/- 1.20% [P = NS]). Moreover, neither FDG defect size, nor LVEF correlated with QTd. This study indicates no relationship between QTd and viability in patients with myocardial infarction and severe left ventricular dysfunction.

Choice of collimator for cardiac SPET when resolution compensation is included in iterative reconstruction.

In clinical cardiac single-photon emission tomography (SPET) studies, collimators of different spatial resolution and geometric efficiency are available for imaging. In selecting the appropriate collimator for clinical use, there is a trade-off between spatial resolution, which can limit the contrast of the reconstructed image, and detection efficiency, which determines the noise in the image. Our objective was to assess which collimator is best suited for cardiac SPET when reconstruction is performed with and without compensation for distance-dependent resolution (CDR). The dynamic MCAT thorax phantom was used to simulate 180 degree technetium-99m cardiac data, acquired using either a general-purpose (GP) or high-resolution (HR) collimator. For GP and HR, the resolution at 15 cm was 11.5 mm and 9.5 mm respectively, and the corresponding relative efficiency was 1.0 and 0.52 respectively. Distance-dependent resolution, attenuation and noise were included in the projection data; scatter was not included. Ordered subsets expectation maximisation reconstruction (subset size 4) was performed with and without CDR. Results were evaluated by comparing the myocardial recovery coefficient and contrast between myocardium and ventricle relative to the original phantom, each plotted for different noise levels corresponding to increasing iteration number. The study demonstrated that, without CDR, HR gave the best results. However, for any given noise level with CDR, GP gave superior recovery and contrast. These findings were confirmed in a physical phantom study. Results suggest that improved reconstruction can be achieved using a GP collimator in combination with resolution compensation.

Should scatter be corrected in both transmission and emission data for accurate quantitation in cardiac SPET?

Ideally, reliable quantitation in single-photon emission tomography (SPET) requires both emission and transmission data to be scatter free. Although scatter in emission data has been extensively studied, it is not well known how scatter in transmission data affects relative and absolute quantitation in reconstructed images. We studied SPET quantitative accuracy for different amounts of scatter in emission and transmission data using a Utah phantom and a cardiac Data Spectrum phantom including different attenuating media. Acquisitions over 180 degrees were considered and three projection sets were derived: 20% images and Jaszczak and triple-energy-window scatter-corrected projections. Transmission data were acquired using gadolinium-153 line sources in a 90-110 keV window using a narrow or wide scanning window. The transmission scans were performed either simultaneously with the emission acquisition or 24 h later. Transmission maps were reconstructed using filtered backprojection and mu values were linearly scaled from 100 to 140 keV. Attenuation-corrected images were reconstructed using a conjugate gradient minimal residual algorithm. The mu value underestimation varied between 4% with a narrow transmission window in soft tissue and 22% with a wide window in a material simulating bone. Scatter in the emission and transmission data had little effect on the uniformity of activity distribution in the left ventricle wall and in a uniformly hot compartment of the Utah phantom. Correcting the transmission data for scatter had no impact on contrast between a hot and a cold region or on signal-to-noise ratio (SNR) in regions with uniform activity distribution, while correcting the emission data for scatter improved contrast and reduced SNR. For absolute quantitation, the most accurate results (bias <4% in both phantoms) were obtained when reducing scatter in both emission and transmission data. In conclusion, trying to obtain the same amount of scatter in emission and transmission data, in addition to being impractical because of the difficulty in knowing the precise scatter components, did not yield such accurate absolute activity quantitation as when emission and transmission scatter were reduced.

Truncation reduction in fan-beam transmission scanning using the Radon transform consistency conditions

Transmission scanning is needed for accurate attenuation correction in cardiac Single Photon Emission Tomography (SPET). Simultaneous emission and transmission imaging can be done using a scintillation camera with a fan-beam collimator and a line source at the focal point. The transmission data will be truncated, however, which may lead to inaccuracy in the reconstructed emission values. The authors have developed two different methods for augmentation of truncated transmission data, based on the Radon transform consistency conditions. The authors' results show that the uniformity in the myocardium can be improved with these methods, as compared to using the truncated data directly in the reconstruction.

Clinical evaluation of no-carrier-added meta-[123I]iodobenzylguanidine for myocardial scintigraphy.

In clinical and research studies, images obtained using carrier-added meta-[123I]iodobenzylguanidine (c.a. [123I]MIBG) have shown quite variable quality, with varying levels of uptake in lung, liver and mediastinum; this is a significant problem for quantification of the myocardial uptake by means of region ratios. First experimental and preliminary human data in respect of no-carrier-added (n.c.a.) [123I]MIBG are indicative of improved imaging quality. The aim of the present study was to evaluate the clinical value of myocardial scintigraphy with n.c.a. [123I]MIBG in patients with tachyarrhythmias. The study population comprised 24 patients with tachyarrhythmogenic diseases routinely studied by cardiac single-photon emission tomography (SPET) with [123I]MIBG. Twelve of the 24 patients were studied with c.a. [123I]MIBG (seven females and five males; mean age 42+/-13 years, range 20-60 years), whereas the other 12 were studied with n.c.a. [123I]MIBG (ten females, two males; mean age 41+/-11 years, range 18-60 years, P=NS). For quantification of the specific uptake in the different organs, count ratios were calculated on SPET images acquired 4 h p.i. Visual analysis of all [123I]MIBG scans showed improved image quality (improved contrast between heart and neighbouring organs) in n.c.a. studies as compared with c.a. studies. A significantly higher heart/left atrial blood ratio was found in the n.c.a. studies as compared with the c.a. studies (10.3+/-3.2 vs 5.3+/-1.3, P=0.0003); furthermore, significantly higher heart/lung and heart/liver ratios (2.5+/-0.6 vs 1.5+/-0.3, P=0.0002, and 0.8+/-0.2 vs 0.6+/-0.1, P=0.0006, respectively) were obtained in the c.a. studies, whereas lung/left atrial blood and liver/left atrial blood ratios showed no significant differences (4.2+/-1.3 vs 3.6+/-1.1, P=0.39, and 13.7+/-5.2 vs 9.6+/-2.2, P=0.21, respectively). In conclusion, the use of n.c.a. [123I]MIBG yields a significantly higher myocardial uptake associated with improvement in contrast between the heart and neighbouring organs and is therefore superior to the commercially available c.a. [123I]MIBG for use in clinical and research studies of the myocardial presynaptic sympathetic nervous system. Furthermore, our data indicate that for quantification the use of a left atrial blood reference region of interest, which is only available on SPET studies, is to be recommended.

Respective roles of scatter, attenuation, depth-dependent collimator response and finite spatial resolution in cardiac single-photon emission tomography quantitation: a Monte Carlo study.

The purpose of this study was to investigate the relative influence of scatter, attenuation, depth-dependent collimator response and finite spatial resolution upon the image characteristics in cardiac single-photon emission tomography (SPET). An acquisition of an anthropomorphic cardiac phantom was performed together with corresponding SPET Monte Carlo simulations. The cardiac phantom and the Monte Carlo simulations were designed so that the effect of scatter, attenuation, depth-dependent collimator response and finite spatial resolution could be studied individually and in combination. The impact of each physical effect and of combinations of effects was studied in terms of absolute and relative quantitative accuracy, spatial resolution and signal-to-noise ratio (SNR) in the resulting images. No corrections for these effects were assessed. Results obtained from Monte Carlo simulations and real acquisitions were in excellent agreement. Attenuation introduced about 90% activity underestimation in a 10-mm-thick left ventricle wall while finite spatial resolution alone introduced about 30% activity underestimation. Scatter had a negligible impact on quantitative accuracy in the recontructed slices when attenuation was present. Neither bull's eye map homogeneity nor contrast between a hot and a cold region were affected by depth-dependent collimator response or finite spatial resolution. Bull's eye map homogeneity was severely affected by attenuation but not by scatter. Attenuation and scatter reduced contrast by about 20% each. Both attenuation and scatter increased the full-width at half-maximum (FWHM) characterizing the spatial resolution of the imaging system by approximately 1 mm each but the main effect responsible for the observed 11-mm FWHM spatial resolution was the depth-dependent collimator response. SNR was reduced by a factor of approximately 2.5 because of attenuation, while scattered counts increased SNR by approximately 10%. In conclusion, the quantification of the relative influence of the different physical effects showed that attenuation is definitely the major phenomenon affecting cardiac SPET imaging accuracy, but that finite spatial resolution, scatter and depth-dependent collimator response also contribute significantly to the errors in absolute and relative quantitation and to the poor spatial resolution.

Nuclear medicine studies of the heart.

Nuclear imaging techniques are well established diagnostic tools in clinical cardiology, providing noninvasive information about myocardial perfusion, function and metabolism. The cost-effectiveness of radionuclide imaging in the diagnostic work-up of patients with coronary artery disease has been demonstrated. Additionally, the documented prognostic value of scintigraphic parameters is of clinical importance to guide decision making. Advances in technology, new radiotracers and new applications contribute to continuous growth in the field of nuclear cardiology. Multi-headed gamma camera systems lead to higher spatial resolution and sensitivity of cardiac single photon emission tomography (SPECT), and they also provide the opportunity for attenuation correction or electrocardiographic gating of SPECT images. Objective quantitative values of perfusion, function and metabolism are derived from scintigraphic data by use of improved software and hardware. With the latest developments in tracer technology, imaging of myocardial necrosis, receptor systems and autonomic innervation has become a reality and will lead to new clinical applications in the future.

Cardiac single-photon emission tomography: is attenuation correction enough?

Cardiac single-photon emission tomography: is attenuation correction enough?

Non-uniform attenuation correction in SPET using a modified conjugate gradient reconstruction method

We describe a non-uniform iterative attentuation correction method for single photon emission tomography (SPET) which uses transmission data. The method was derived using the general inverse problem theory. A cost functional which includes noise was derived and minimized using a weighted-least-square maximum a posteriori conjugate gradient (CG) method. The Hessian of the cost functional was modified by adding a noise term. The a priori value of the model data vector was neglected. The method was tested in a clinical cardiac SPET perfusion study. Prior to the emission scan, blank and transmission scans were acquired and used to obtain the non-uniform map of linear attenuation coefficients. The results of the study show that the new iterative method has a slightly better convergence rate than the standard CG method. Also, the corrected emission slices obtained by the new method were less noisy. Noise was measured as rms% and was reduced by a factor of 2.3 for the transmission scans and by a factor of 1.9 for the emission scans when reconstructed with the new method compared to the CG method. The new method provides a stable solution, whereas the standard CG method, for higher iterative steps, diverges. There is potential for improvement in the approach described here.

Optimal metabolic conditions during fluorine-18 fluorodeoxyglucose imaging; a comparative study using different protocols

Positron emission tomography (PET) with fluorine-18 fluorodeoxyglucose (FDG) can identify viable myocardium in patients with coronary artery disease. Recently, FDG imaging with single-photon emission tomography (SPET) and 511-keV collimators has been described. To obtain optimal image quality in all patients, cardiac FDG studies should be performed during hyperinsulinaemic glucose clamping. It has been suggested that FDG imaging after the administration of a nicotinic acid derivative may yield comparable image quality to clamping. We studied eight patients and compared the image quality of cardiac FDG SPET studies after oral glucose loading, after administration of a nicotinic acid derivative (acipimox, 250 mg orally) and during hyperinsulinaemic glucose clamping. The image quality was expressed as the myocardial to blood pool (M/B) activity ratio, which is used as a measure of the target-to-background ratio The M/B ratios were comparable after clamping and acipimox (2.8+/-0.8 vs 2.9+/-0.7), whereas the M/B ratio was lower after oral glucose loading (2.2+/-0.3, P<0.05 vs clamp and acipimox). To determine the clearance of FDG from the plasma, blood samples were drawn at fixed time intervals and the FDG activity was measured in a gamma well counter. The FDG clearance was significantly lower after oral glucose loading (T(1/2) oral load=16. 2+/-5.7 min) as compared with clamping (T(1/2) clamp=8.1+/-3.1 min) and acipimox (T(1/2) acipimox=10.7+/-4.0 min, NS vs clamp, P<0.05 vs oral load). It may be concluded that FDG SPET imaging after acipimox administration yields image quality and clearance rates comparable to those obtained during clamping. FDG SPET in combination with acipimox may useful in clinical routine for the assessment of myocardial viability.

Use of the selective linogram in cardiac tomography quality control.

Quality control for detection of patient motion is essential in tomographic myocardial imaging. Despite significant limitations, the summation image or conventional "linogram" has long been advocated as a useful image in the detection of vertical motion. In this study a new quality control image entitled the "selective linogram" is proposed to replace the summation image in routine cardiac single-photon emission cardiac tomography (SPECT) quality control. The selective linogram is constructed in a manner somewhat analogous to the sinogram. In the sinogram, each row represents a different projection angle; in the selective linogram each column represents a different projection angle. After selection of eight motion-free studies from acquisitions at our clinical center, vertical motion of various types (bounces, shifts, and creep) were added to the projection frames. Summation image and selective linogram quality control images from these motion-containing studies and the original motion-free studies were presented in a blinded manner to two observers for scoring of patient motion. The selective linogram was significantly more accurate in allowing detection of vertical motion than was the summation image (accuracy 89% vs 47%). The selective linogram image is markedly superior to the summation image for the detection of vertical patient motion during cardiac SPECT. This new technique can be a valuable aid in SPECT quality control.

Cardiac single-photon emission tomography with a 90 degrees dual-head system.

Dual-head single-photon emission tomography (SPET) systems which permit a 90 degrees orientation of the heads provide a twofold increase in sensitivity for 180 degrees SPET compared with single-head systems. Since such systems have additional mechanical and electrical alignment and stability requirements, clinical equivalency for myocardial perfusion SPET must be demonstrated. Accordingly, we studied 26 subjects who underwent exercise thallium scintigraphy consecutively with both single-head and dual-head systems. Image acquisition was similar, except that the dual-head study took one-half the time. Image reconstruction was identical. Images were interpreted in a blinded fashion, and rated for technical quality. All 26 studies were equivalently interpreted for the presence or absence of perfusion defects. Fourteen of the studies were judged to be technically equivalent; seven were judged to be slightly better with the single-head system; three were judged to be slightly better with the dual-head system; and two were judged to be definitely better with the dual-head system. We conclude that dual-head 90 degrees systems provide equivalent clinical performance in half the acquisition time.