Independent and incremental prognostic value of exercise thallium single-photon emission computed tomographic imaging in women

Background  

This study examined the independent and incremental prognostic value of exercise thallium single-photon emission computed tomographic imaging in 212 women who also underwent coronary angiography.     

Prognostic value of adenosine single-photon emission computed tomographic thallium imaging in medically treated patients with angiographic evidence of coronary artery disease

Background  

This study examined the prognostic value of adenosine single-photon emission computed tomographic thallium imaging in medically treated patients with angiographic evidence of coronary artery disease (CAD).     

Planar and tomographic imaging with technetium 99m-labeled tetrofosmin: Correlation with thallium 201 and coronary angiography

This study compared the results of planar and single-photon emission computed tomographic (SPECT) imaging with tetrofosmin with those of²⁰¹Tl and coronary angiography. In three normal volunteers the images were normal by both²⁰¹Tl and tetrofosmin (planar and SPECT). In 23 patients with coronary artery disease, the images were abnormal in 20 patients by SPECT tetrofosmin, in 19 by planar tetrofosmin, in 20 by SPECT thallium, and in 18 by planar thallium (difference not significant). Both planar and SPECT images were divided into five segments per patient. There were 58 perfusion defects by SPECT tetrofosmin, 50 by planar tetrofosmin (difference not significant), 47 by SPECT thallium, and 42 by planar thallium (difference not significant). Perfusion defects were reversible in 47 segments (36%) by SPECT tetrofosmin, 35 (27%) by planar tetrofosmin, 31 (24%) by SPECT thallium (p<0.05 vs SPECT tetrofosmin), and 31 (24%) by planar thallium (difference not significant). Among the 23 patients with coronary artery disease, 19 underwent coronary angiography. In these patients there were 32 diseased coronary arteries. Perfusion defects were present in 21 territories (66%) by SPECT tetrofosmin, 19 (59%) by planar tetrofosmin, 20 (63%) by SPECT thallium, and 18 (56%) by planar thallium. There was agreement between thallium and tetrofosmin in 108 of 130 segments (κ statistics=0.69±0.06). The images, especially with SPECT, are better with tetrofosmin than with²⁰¹Tl. Thus myocardial imaging with tetrofosmin provides results that are at least as good as those of²⁰¹Tl. Slightly more abnormal segments and more reversible defects are detected by tetrofosmin than by thallium imaging, especially with SPECT imaging. Supported in part by Mediphysics, Inc., Arlington Heights, Ill.     

Quantitative myocardial thallium single-photon emission computed tomography in normal women: Demonstration of age-related differences

The aim of this study is the development of a database of normal women for quantitative analysis of exercise and reinjection myocardial single-photon emission computed tomography (SPET). We studied 101 subjects (40 males and 61 females) with less than 5% likelihood of coronary artery disease. All patients underwent stress and rest thallium-201 myocardial SPET. Myocardial stress was induced by bicycle exercise test (n=51), dipyridamole infusion (n=27) or a combined test (n=23). Multivariate ANOVA showed that the type of stress did not influence the percentage of thallium uptake for each region. Significant differences between men and women were found for the percentage of uptake in the inferior and the anterior wall. The most original finding of this study is the correlation between age and thallium uptake in the three regions of the anterior wall, showing an increase in measured thallium uptake with age for women. Consequently, two groups of women, those under and those over 55 years old, were separated, with a significantly lower tracer uptake in the anterior wall in the younger age group. These results may suggest that the commonly described breast tissue attenuation is due not only to breast volume or morphology but also to breast density. This emphasizes the need for two different databases for myocardial SPET quantitative analysis in the female population. Awareness of this fact should allow avoidance of any underestimation of possible anterior wall ischaemia in women aged more than 55 years.     

Reversible ischemia in severe stress technetium 99m-labeled sestamibi perfusion defects assessed from gated single-photon emission computed tomographic polar map fourier analysis

Background  

Detection of reversible ischemia and regional viability by inference from the presence of preserved resting myocardial thickening on dynamic electrocardiographic-gated tomographic (GSPECT) images obtained after stress injection could potentially obviate the need for a separate resting injection. This would decrease the cost, effort, duration, and radiation exposure of diagnostic myocardial perfusion imaging. The aim of this study was to determine whether functional images derived from GSPECT stress myocardial perfusion images, which represent indices of regional wall thickening, could predict the pattern of reversibility of perfusion defects in myocardial segments with severe perfusion defects on stress ^99mTc-labeled sestamibi (^99mTc-sestamibi) images.     

Cardiofocal collimators for gated single-photon emission tomographic myocardial perfusion imaging

Cardiofocal collimators (CFCs) are more sensitive than parallel-hole collimators (PHCs) of the same resolution because the rays converge in the centre of the field of view. After reconstruction a useful field of view with a 10 cm radius in which both sensitivity and resolution are homogeneous is obtained. In this article the feasibility and accuracy of gated single-photon emission tomographic (gated SPET) myocardial perfusion imaging using a triple-head camera equipped with CFC, is evaluated. Twenty patients with a history of myocardial infarction were studied. SPET myocardial perfusion images, gated in eight time bins, were acquired in a random sequence with a PHC and a CFC for each patient. Imaging was started 60 min after the injection of 925 MBq of technetium-99m tetrofosmin at rest. Ninety-six projections over 360° were acquired, with 32 stops of 40 s for the PHC and 20 s for the CFC in order to obtain similar count densities. The extent (EXT) and severity (SEV) of perfusion defects were quantified on polar maps using the non-gated data. Left ventricular volumes [end-diastolic volume (EDV), end-systolic volume (ESV)] and ejection fraction (LVEF) were calculated from gated data using the Cedars-Sinai program. In 17 of 20 patients the complete left ventricle was positioned within the useful field of view of the CFC. The results in respect of perfusion, volumes and ejection fraction were almost identical to those obtained with the PHC. The mean difference±SD between the CFC and the PHC was −2.30±7.16 (% of LV area) for EXT, −0.48±2.90 for SEV (arbitrary units), −1,50±5.25 (ml) for EDV and 0.53±4.10 (%) for LVEF. The largest differences in EXT and LV volumes were observed in patients in whom a part of the LV was not positioned within the useful field of view. We conclude that, for the majority of patients, identical information with regard to both perfusion and function can be derived from gated SPET myocardial perfusion studies obtained with PHCs or with CFCs. Because of the greater sensitivity, however, a much shorter acquisition time is required with CFCs. Received 7 May and in revised form 31 August 1997     

Left bundle branch block and coronary artery disease: Accuracy of dipyridamole thallium-201 single-photon emission computed tomography in patients with exercise anteroseptal perfusion defects

Background  Reduced septal or anteroseptal uptake of thallium-201 during exercise is frequently observed in patients with left bundle branch block (LBBB) even in the absence of left anterior descending (LAD) coronary artery disease. The purpose of this study was to evaluate prospectively the accuracy of dipyridamole²⁰¹TI single-photon emission computed tomography (SPECT) in detecting LAD coronary artery disease in patients with LBBB and septal or anteroseptal perfusion defects on exercise²⁰¹TI SPECT. Methods and Results  Twelve consecutive patients (10 men and two women) with complete LBBB and septal or anteroseptal perfusion defects on exercise²⁰¹TI SPECT underwent dipyridamole²⁰¹TI SPECT. The delay between dipyridamole and exercise was 2 to 30 days. Coronary angiography was performed during this period in all patients. Six (50%) of 12 patients with exercise perfusion defects showed normal perfusion after dipyridamole; all had normal coronary angiograms. The remaining six patients also had positive results of dipyridamole studies, two with moderate and four with severe septal or anteroseptal perfusion defects. Coronary angiography showed significant (>50%) LAD coronary artery stenosis in three patients; three patients with severe septal or anteroseptal perfusion defects after dipyridamole had normal coronary angiograms. Neither the evaluation of apical involvement nor the presence of dilated ventricles, decreased left ventricular ejection fraction, or wall motion abnormalities could help to identify (or explain) false-positive results. Conclusion  This study confirms that dipyridamole is more accurate than exercise in excluding LAD coronary artery disease. However, there are still false-positive results and the severity of the septal or anteroseptal perfusion defect does not add additional information to identify LAD coronary artery disease. Coronary angiography is thus necessary for positive dipyridamole study results to identify coronary artery disease as a major prognostic factor in patients with LBBB.     

Impact on exercise single-photon emission computed tomographic thallium imaging on patient management and outcome

Background

Stress perfusion imaging is useful in risk stratification of patients with known or suspected coronary artery disease. In the current era of managed health care, there is a need to provide data on patient outcome.

Methods and Results

This study examined the impact of exercise single-photon emission computed tomographic (SPECT) thallium imaging on patient management (the subsequent need for coronary angiography and revascularization) and outcome (the occurrence of hard cardiac events defined as cardiac death or nonfatal acute myocardial infarction) in 2700 patients who were being evaluated for diagnostic purposes. None of the patients had previous coronary angiography, coronary revascularization, or Q-wave myocardial infarction. The SPECT images were normal in 2027 patients (group 1) and abnormal in 673 patients (group 2). Within 6 months after thallium imaging 53 patients in group 1 (3%) and 242 patients in group 2 (36%) underwent coronary angiography (p=0.0001). The patients who underwent coronary angiography had higher pretest probability of coronary disease (group 1) or more perfusion defects (group 2) than patients who did not (p=0.0001 each). Coronary revascularization within 3 months of coronary angiography was performed in 1 of the 53 patients (2%) in group 1 and in 87 of 242 patients (30%) in group 2 (p=0.0001). Among the remaining patients who had coronary angiography but were medically treated there were no hard cardiac events in group 1 but there were 15 events in group 2 (p=0.02).

Conclusions

The results of exercise SPECT thallium imaging are important in patient management and outcome. Coronary angiography, coronary revascularization and events are rare in patients with normal exercise SPECT thallium images.     

Motion detection and correction using multi-rotation 180° single-photon emission tomography for thallium myocardial imaging

Patient and organ motion is a potentially limiting factor in gamma camera single-photon emission tomography (SPET) imaging, as highlighted in stress thallium myocardial SPET, where the heart may exhibit a systematic axial motion (cardiac creep) following stress. Multi-rotation SPET has previously been described as a means of obtaining better raw data for motion detection and correction. This study describes the validation of a computerised motion detection algorithm applied to multi-rotation SPET, and reports measured motions in thallium myocardial stress SPET studies from a single-headed gamma camera. Forty-two patients underwent pharmacological stress (dipyridamole) with leg raising, with injection of 75 MBq thallium-201 and imaging after a 10-min delay to detect or evaluate coronary artery disease. Multi-rotation gamma camera SPET was performed with a single-headed gamma camera, with five sequential rapid (4.5 min) continuous SPET mode rotations over 180°. A one-dimensional cross-correlation alignment technique was applied to the projection images to perform motion detection and correction in the axial direction prior to combining the five data sets for tomographic reconstruction. Validation of the cross-correlation alignment analysis was carried out by performing imaging with measured whole-body axial motions in nine subjects, and by reproducibility measurements on multi-rotation data sets. The effect of the applied motion correction was evaluated by calculating mean differences between image pairs before and after shifting, and the general reliability of the automatic motion detection was checked to within one pixel by visual assessment of 160 image pairs. Validation measurements of the cross-correlation technique gave a mean absolute error of 1.5±0.4 mm (0.24±0.06pixels) with a maximum error of 3.7 mm (0.6 pixels). In 40 subjects undergoing pharmacological stress ²⁰¹Tl myocardial SPET imaging, the mean cardiac axial creep movement was calculated as 3.1±0.7 mm (0.49±0.11 pixels), with 13 out of 40 (32%) having a calculated motion of 1 pixel (6.3 mm) or more. The automatic image shift was visually judged to be within 1 pixel in all 160 image pair analyses, and the mean pixel value difference between image pairs was reduced following image shifting. It is concluded that multi-rotation 180° SPET imaging provides raw data which allow objective and accurate motion detection of cardiac motion in thallium stress myocardial imaging, whilst the one-dimensional cross-correlation technique demonstrates adequate accuracy and reliability to be applied as an automatic motion screening technique on these data. Received 14 March and in revised form 27 July 1998     

Thallium-201 right lung/heart ratio during exercise in patients with coronary artery disease: relation to thallium-201 myocardial single-photon emission tomography, rest and exercise left ventricular function and coronary angiography

The aim of this study was to correlate lung thallium-201 uptake on exercise with ²⁰¹Tl single-photon emission tomography (SPET) myocardial perfusion imaging, rest and exercise equilibrium radionuclide angiographic and coronary angiographic findings in patients with coronary artery disease (CAD) using a simple, reproducible lung/heart (L/H) ratio that would be easy to use in clinical practice. L/H ratio was defined on the anterior planar image obtained during exercise ²⁰¹Tl SPET acquisition as the mean counts per pixel in an entire right lung field region of interest divided by the mean counts per pixel in the hottest myocardial wall region of interest. We studied 103 patients. Fifty-nine patients (group I) with <5% likelihood of CAD were used as a reference group. In 44 CAD patients (group II), L/H ratio was compared with ²⁰¹Tl SPET, radionuclide angiographic and coronary angiographic variables. The group I L/H ratio of 0.35±0.05 (mean ±1 SD) was significantly lower (P<0.001) than the group II L/H ratio of 0.45±0.10. An L/H ratio >0.45 (mean + 2 SD in group I) was considered abnormal. In group II, L/H ratio showed a significant correlation with stress and rest ²⁰¹Tl perfusion defect size (r = 0.39 and r = 0.42, P<0.01, respectively), but not with extent of ischaemic myocardium. The mean L/H ratio was 0.41±0.10 in patients with one-vessel disease (n = 15), 0.46±0.08 in those with two-vessel disease (n = 17) and 0.47±0.12 in those with three-vessel disease (n = 12), but no significant difference was found between the three subgroups. L/H ratio showed a significant inverse relation with rest and exercise left ventricular ejection fraction (r = –0.37 and r = –0.50, P<0.05 and P<0.001, respectively). Using stepwise multiple regression analysis, exercise left ventricular ejection fraction and previous history of hypertension were the sole two variables independently predictive of the L/H ratio. In conclusion, although lung thallium uptake is usually found to correlate with extent and severity of CAD, increased L/H ratio should primarily be considered as a marker of exercise-induced left ventricular systolic and perhaps diastolic dysfunction, probably independent of the underlying cardiac disease. Received 14 January and in revised form 22 February 1999     

F18-fluorodeoxyglucose single-photon emission computed tomography predicts functional outcome of dyssynergic myocardium after surgical revascularization

Background  Prediction of functional recovery after revascularization is possible with positron emission tomography and F18-fluorodeoxyglucose (FDG). Recently, the use of FDG in combination with single-photon emission computed tomography (SPECT), with 511 keV collimators, has been proposed to allow more widespread use of FDG. In the current study we aimed to predict improvement of regional left ventricular function after surgical revascularization with FDG and SPECT. Methods and Results  Twenty-seven patients with regional wall motion abnormalities (on echocardiography) underwent early thallium-201 (TI-201) SPECT to assess perfusion and FDG SPECT to assess regional glucose uptake. The left ventricular myocardium was divided into 13 segments. For each segment, tracer uptake was evaluated visually (with the use of a 4-point scoring system) by consensus of two observers. Myocardial viability was determined in dyssynergic segments on echocardiography and defined as normal perfusion or increased FDG uptake in a perfusion defect (mismatch). Absence of viability was defined as a perfusion defect without increased FDG uptake (match). Improvement of regional, wall motion was assessed 3 months after revascularization. In the group of segments that were viable on FDG/TI-201 SPECT (n=64), the segmental wall motion score decreased from 1.4±0.5 to 0.6±0.7 (p<0.01), whereas the segmental wall motion score remained unchanged in nonviable segments (n=72): 1.6±0.5 versus 1.5±0.6 (not significant). Forty-six (72%) of the 64 segments that were viable on FDG/TI-201 SPECT demonstrated improved contractile function after coronary revascularization. In contrast, only 7 (10%) of 72 nonviable segments on FDG/TI-201 SPECT showed improvement in function after revascularization (p<0.01 versus viable segments). The sensitivity, specificity, and positive and negative predictive values were 87%, 78%, 72%, and 90%, respectively. Conclusion  This study shows that FDG/TI-201 SPECT can identify patients who improve in regional ventricular function after revascularization.     

A simple method for localising single-photon emission computed tomographic images on an anatomical template

We introduce a simple method for localising brain images an anatomical templates. Our method does not need expensive software or hardware and may be useful for clinical investigation.     

Different thallium-201 single-photon emission tomographic patterns in benign and aggressive meningiomas

To evaluate the possibility of preoperatively obtaining an index of aggressiveness for intracranial meningiomas, we prospectively studied 22 patients with computed tomography or magnetic resonance imaging evidence of meningeal tumour, using single-photon emission tomography (SPET) of the brain and thallium-201 (²⁰¹Tl). On a brain-dedicated SPET scanner, a rapid acquisition protocol with early, short scans was started simultaneously with the intravenous administration of 111 MBq²⁰¹Tl, covering the initial intratumoral distribution of the tracer. Twenty minutes post injection, a delayed SPET scan was also obtained. On the reconstructed and attenuation-corrected images we calculated the²⁰¹Tl concentration in tumour and normal contralateral brain tissue, and compared intratumoral tracer concentration in the initial and the final part of the rapid acquisition protocol. Benign and malignant meningiomas were classified as such based on histological examination. In malignant lesions, the ratio of the²⁰¹Tl concentration at 2–4 min post injection to that at 14–16 min was found to be significantly higher than in non-aggressive neoplasms (mean±1 SD: 1.14±0.31 and 0.56±0.13, respectively,P <0.01). Conversely, in the delayed scan, most lesions showed high tracer concentration, and the two groups could not be distinguished. In addition, three recurrent meningiomas displayed the same imaging behaviour as the malignant group, i.e. had similar²⁰¹Tl concentration values at 2–4 and at 14–16 min. Our findings suggest that the comparative assessment of intratumoral²⁰¹T1 concentration at 2–4 and at 14–16 min post injection could provide a fast, simple method to differentiate preoperatively intracranial meningiomas with different biological behaviour.     

A semi-automated method for edge detection in the evaluation of left ventricular function using ECG-gated single-photon emission tomography

Thallium-201 gated single-photon emission tomography (GSPET) of myocardium was performed at rest in 18 patients. Images were reconstructed to obtain end-diastolic (ED) and end-systolic (ES) images. The endocardial and epicardial edges of the left ventricle (LV) for the ED and ES images were defined for the mid-ventricular images of the short-axis slices, using a semi-automated method. LV wall thickness was measured for ED and ES images at 10° intervals. Mean LV thickness was derived as the mean of the LV thickness for the three mid-ventricular slices. The systolic thickening (ST) was derived as: mean LV thickness (ES) —mean LV thickness (ED). The systolic thickening ratio (STR) was defined as: ST/mean LV thickness (ED). LV cavity area was measured. The dilation ratio (DR) was defined as: [mean cavity area (ED) — mean cavity area (ES)]/mean cavity area (ED). LV ejection fraction (LVEF) was estimated using technetium-99m gated blood pool study. There was a linear correlation between LVEF and ST (r=0.85), LVEF and STR (r=0.77) and LVEF and DR (r=0.81). There was a strong correlation (r=0.85) between regional STR and regional percent count increase in 52 segments which did not have perfusion defects. As well as for the evaluation of myocardial perfusion, GSPET images can be of use for the assessment of LV function using an appropriate method for LV edge detection. Correspondence to: Kuang-Tao A. Yang     

Application of transmission scan-based attenuation compensation to scatter-corrected thallium-201 myocardial single-photon emission tomographic images

A practical method for scatter and attenuation compensation was employed in thallium-201 myocardial single-photon emission tomography (SPET or ECT) with the triple-energy-window (TEW) technique and an iterative attenuation correction method by using a measured attenuation map. The map was reconstructed from technetium-99m transmission CT (TCT) data. A dual-headed SPET gamma camera system equipped with parallel-hole collimators was used for ECT/TCT data acquisition and a new type of external source named ”sheet line source” was designed for TCT data acquisition. This sheet line source was composed of a narrow long fluoroplastic tube embedded in a rectangular acrylic board. After injection of ^99mTc solution into the tube by an automatic injector, the board was attached in front of the collimator surface of one of the two detectors. After acquiring emission and transmission data separately or simultaneously, we eliminated scattered photons in the transmission and emission data with the TEW method, and reconstructed both images. Then, the effect of attenuation in the scatter-corrected ECT images was compensated with Chang’s iterative method by using measured attenuation maps. Our method was validated by several phantom studies and clinical cardiac studies. The method offered improved homogeneity in distribution of myocardial activity and accurate measurements of myocardial tracer uptake. We conclude that the above correction method is feasible because a new type of ^99mTc external source may not produce truncation in TCT images and is cost-effective and easy to prepare in clinical situations. Received 1 September and in revised form 25 October 1997     

Gated single-photon emission tomography imaging protocol to evaluate myocardial stunning after exercise

This study was designed to apply ECG-gating to stress myocardial perfusion single-photon emission tomography (SPET) for the evaluation of myocardial stunning after exercise. Technetium-99m sestamibi was selected as the perfusion agent and a rest/exercise 1-day protocol was employed. Fourteen patients without coronary stenosis and 33 patients with coronary stenosis were enrolled in the study. We carried out three data acquisitions with ECG-gating: a 15-min data acquisition starting 30 min after the rest injection (AC1), a 5-min acquisition starting 5 min after the stress injection (AC2) and a 15-min acquisition starting 20 min after the stress injection (AC3). Calculation of left ventricular ejection fraction (LVEF) values was performed by means of automatic determination of the endocardial surface for all gating intervals in the cardiac cycle. Measured global EF values in 14 patients without coronary stenosis were 52.3%±7.6% (AC1), 60.6%±8.9% (AC2) and 55.6%± 5.6% (AC3), and those in 11 patients with severe ischaemia were 53.6%±8.0% (AC1), 45.6%±12.1% (AC2) and 49.7%±10.7%. The magnitude of the depression of post-stress LVEF relative to the rest LVEF correlated with the severity of ischaemia (r=0.594, P=0.002), and segments manifesting post-stress functional depression were associated with ischaemic segments showing reversible perfusion defects. Stress myocardial perfusion SPET with ECG-gating is a feasible method for the evaluation of myocardial stunning as well as exercise-induced ischaemia. Received 13 June and in revised form 19 August 1999     

Pharmacologic stress perfusion imaging with adenosine: Role of simultaneous low-level treadmill exercise

BACKGROUND: Adenosine is commonly used for pharmacologic stress myocardial perfusion imaging (MPI). However, it frequently results in adverse effects, and the subdiaphragmatic tracer uptake may interfere with the image interpretation. Our aim was to determine the feasibility of combining low-level treadmill exercise with adenosine MPI and its impact on adverse effects, image quality, and myocardial ischemia. METHODS AND RESULTS: Forty-one patients underwent technetium 99m sestamibi single photon emission computed tomography following adenosine and adenosine with low-level exercise (adenosine-Ex) on separate occasions and rest MPI. A comparison was made of symptoms, hemodynamic response, electrocardiographic changes, image quality, and image interpretation between the 2 protocols. With adenosine-Ex, fewer patients had one or more adverse effects (61% vs 90%; P =.006), more patients had ischemic electrocardiographic changes (34% vs 15%; P =.03), a higher percentage had excellent- or fair-quality images (88% vs 61%; P =.003), and they had higher heart-liver ratios (1.0 +/- 0.37 vs 0.84 +/- 0.29; P =.002) compared with adenosine alone. Four adenosine MPI studies, but only 2 adenosine-Ex studies, were uninterpretable because of excessive subdiaphragmatic radiotracer activity. Of the 39 patients with at least 1 interpretable stress study, interpretation was discordant in 11 (28%): 7 showed greater ischemia with adenosine-Ex, 2 uninterpretable adenosine studies were interpretable with adenosine-Ex, and 2 studies interpreted as abnormal with adenosine were normal by adenosine-Ex (both had normal coronary angiograms). CONCLUSIONS: Simultaneous low-level treadmill exercise with adenosine Tc-99m sestamibi imaging is safe and feasible, significantly reduces unfavorable side effects, enhances image quality, and may result in greater ischemia detection compared with adenosine alone.     

Attenuation compensation for cardiac single-photon emission computed tomographic imaging: Part 1. Impact of attenuation and methods of estimating attenuation maps

Attenuation is believed to be one of the major causes of false-positive cardiac single-photon emission computed tomographic (SPECT) perfusion images. This article reviews the physics of attenuation, the artifacts produced by attenuation, and the need for scatter correction in combination with attenuation correction. The review continues with a comparison of the various configurations for transmission imaging that could be used to estimate patient specific attenuation maps, and an overview of how these are being developed for use on multiheaded SPECT systems, including discussions of truncation, noise, and spatial resolution of the estimated attenuation maps. Ways of estimating patient specific attenuation maps besides transmission imaging are also discussed.     

Comparison of thallium-201 single-photon emission tomography after rest injection and fluorodeoxyglucose positron emission tomography for assessment of myocardial viability in patients with chronic coronary artery disease

This prospective study in 42 patients with chronic coronary artery disease and severe wall motion abnormalities (sWMA) on cineventriculography (24 patients with previous myocardial infarction; ejection fraction, 45%±13%) was designed to compare myocardial thallium-201 uptake after rest injection and normalized fluorodeoxyglucose (¹⁸FDG) uptake (after oral glucose load) for assessment of a rest ²⁰¹Tl protocol to evaluate myocardial viability. The left ventricle was divided into the supply territory of the left anterior descending coronary artery (LAD) and the lateral wall and posterior territory (inferior, posterior and posteroseptal segments) because of the high variability of left circumflex and right coronary artery supply territories. Segmental ²⁰¹Tl uptake in single-photon emission tomography (SPET) and segmental normalized ¹⁸FDG uptake (13 segments per patient) showed a close linear relationship in the LAD territory (r=0.79) and in the lateral wall (r=0.77), while the correlation in the posterior territory was considerably lower (r=0.52). ²⁰¹Tl/¹⁸FDG concordance was defined as an ¹⁸FDG uptake exceeding ²⁰¹Tl uptake by < 20%. Discordance was assumed if ¹⁸FDG exceeded ²⁰¹Tl uptake by at least 20%. Concordant results were shown by 81% (439/541) of segments. In segments with severe ²⁰¹Tl reduction ( 50% of peak, n=78) discordance was observed in 10% of segments in the LAD territory and lateral wall (n=62) and in 44% of segments in the posterior territory (n=16). In segments with moderate ²⁰¹Tl reduction (51%–75%, n=205) discordance occured in 12% (LAD and lateral wall, n=126) or 46% (posterior territory, n=79) of segments, respectively. Severe defects were defined as the entire area with ²⁰¹Tl uptake 50% within a defined territory. Discordance was observed in 6/43 (14%) of these. Of 90 areas with sWMA on cineventriculography, 12 showed discordant results. Ten of these 12 discordant areas affected septum or posterior wall. In areas with normal wall motion or only mild hypokinesis, discordance occured in the septum or posterior wall in 22% whereas the figure for the anterior or lateral wall was only 2%. These results point to a significant role of photon attenuation in ²⁰¹Tl SPET imaging in the septum and posterior wall. It is concluded that ²⁰¹Tl SPET using a rest protocol identifies viable myocardium in the supply area of the LAD and in the lateral wall with high accuracy compared to ¹⁸FDG positron emission tomography while disordance in the posterior territory may be governed by photon attenuation in the SPET study rather than by a pathophysiological difference. Correspondence to: C. Aftehoefer