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     

A comparison of rest sestamibi and rest-redistribution thallium single photon emission tomography: Possible implications for myocardial viability detection in infarcted patients

Thirty patients (26 men, 4 women, mean age 61 ± 8 years) who had suffered myocardial infarction 15 ± 6 months previously, were submitted to (1) standard stress-redistribution thallium-201 single photon emission tomography (SPET), (2) rest-redistribution²⁰¹Tl SPET and (3) stress-rest technetium-99m sestamibi SPET. Uptake modifications in relation to exercise-induced defects were evaluated in a total of 390 myocardial segments. Tracer uptake was scored as normal (=0), mildly reduced (=1), apparently reduced (=2), severely reduced (=3) or absent (=4). Comparison of stress studies failed to show any statistical difference (58% segmental abnormalities with sestamibi vs 61% with thallium). Uptake abnormalities (score 1–4) were detected in 55% of the segments wiliest sestamibi, 55% with standard thallium redistribution, 55% with early imaging after thallium injection at rest and 54% with 3-h delayed rest imaging (P = NS). Absence of tracer uptake (score = 4) under resting conditions was recorded in 75 (19%) segments with standard²⁰¹Tl redistribution, 75 (19%) with rest sestamibi, 70 (18%) with rest²⁰¹Tl imaging and 62 (16%) with rst-rdistruion²⁰¹Tl (P<0.05 vs other imaging modalities). Thus, 3-h delayed rest thallium imaging detected reversibility of uptake defects in a significantly higher number of myocardial segments. This finding might have important implications for both tracer and technique selection when myocardial viability is the main clinical issue.     

Use of 123I-BMIPP single-photon emission tomography to estimate areas at risk following successful revascularization in patients with acute myocardial infarction

Previous studies have indicated that iodine-123 labelled β-methyliodophenyl pentadecanoic acid (BMIPP), an iodinated fatty acid analogue, can identify persistent alteration of fatty acid metabolism after restoration of blood flow. To assess whether fatty acid imaging can delineate areas at risk following successful revascularization in patients with acute myocardial infarction (AMI), BMIPP findings at 1 week post AMI were compared with perfusion imaging before and after revascularization therapy. Sixty-five patients with AMI underwent technetium-99m tetrofosmin single-photon emission tomography (SPET) before m (TF0) and 1 week (TF1) after successful revascularization therapy. BMIPP SPET was also performed under a fasting state at 1 week (BM1) post AMI. The extent scores were calculated from the defect scores in 20 segments. The BM1 score (7.7±3.9) was similar to the TF0 score (8.8±4.2) (r=0.86, P<0.0001), but significantly higher than the TF1 score (5.8±3.9) (P<0.0001). A significant correlation was observed between the BM1 score and TF0 score (r=0.86, P<0.0001). Among a total of 1300 segments, the BM1 score was identical to the TF0 score in 1156 (88.9%). These data indicate that the ability of BMIPP imaging at 1 week post AMI to identify areas at risk is similar to that of tetrofosmin perfusion imaging in the acute phase. This may be due to the impairment of fatty acid uptake and metabolism reflecting prior severe ischaemic insult which persists at least 1 week after recovery of perfusion in the acute phase of AMI. Received 21 February and in revised form 28 May 1998     

Impairment of regional fatty acid uptake in relation to wall motion and thallium-201 uptake in ischaemic but viable myocardium: Assessment with iodine-123-labelled beta-methyl-branched fatty acid

In coronary artery disease, discrepancy in the uptake of thallium-201 and of methyl-branched fatty acid at rest has been described. The purpose of this study was to evaluate iodine-123 labelled beta-methylbranched fatty acid (BMIPP) myocardial uptake and wall motion at rest in segments with stress-induced ischaemia identified by stress²⁰¹Tl tomography in patients with chronic coronary artery disease.¹²³I-BMIPP myocardial tomography was performed at rest and was compared with the findings of exercise-reinjection²⁰¹Tl tomography in 45 patients with chronic coronary artery disease. Regional wall motion was evaluated by contrast left ventriculography in 36 patients. Among 237 segments with reversible²⁰¹Tl defects, equally decreased uptake on both reinjection²⁰¹Tl and BMIPP images was observed in 93 (39%), more severely decreased uptake of BMIPP in 118 (50%) and more severely decreased uptake of reinjection²⁰¹Tl in 26 (11%). On the other hand, among 90 segments with non-reversible²⁰¹Tl defects, each pattern was observed in 71 (79%), 6 (7%) and 13 (14%) segments, respectively. When comparing the ischaemic segments with and without more severely reduced uptake of BMIPP than of reinjection²⁰¹Tl, wall motion was impaired to a greater extent in the segments with more severely reduced uptake of BMIPP than of reinjection²⁰¹Tl [severe hypo- or dyskinesis was present in 64 (70%) of 91 segments and in 24 (22%) of 110 segments, respectively,P<0.005]. In patients with chronic coronary artery disease, resting fatty acid uptake was frequently more reduced than reinjection²⁰¹Tl in the segments with stress-induced ischaemia, while in most of the fixed perfusion defects BMIPP and reinjection²⁰¹Tl uptake decreased concordantly. In ischaemic myocardium, wall motion was impaired to a greater extent in those segments which showed more severely reduced uptake of BMIPP than of reinjection²⁰¹Tl. In ischaemic but viable myocardium, discordant BMIPP uptake less than reinjection²⁰¹Tl uptake may indicate metabolic alterations and wall motion abnormality at rest independent of perfusion abnormalities. In conclusion, the combination of resting BMIPP and stress-reinjection²⁰¹Tl imaging may provide information on metabolic alterations and wall motion abnormality at rest independent of perfusion abnormalities.     

Dobutamine stress thallium-201 single-photon emission tomography versus echocardiography for evaluation of the extent and location of coronary artery disease late after myocardial infarction

Dobutamine stress echocardiography and thallium-201 myocardial perfusion scintigraphy are clinically useful methods for the evaluation of coronary artery disease (CAD). However, the relative merits of these imaging modalities in the evaluation of the extent of CAD after myocardial infarction have not been well studied. The aim of this study was to compare the accuracy of dobutamine stress echocardiography and simultaneous ²⁰¹Tl single-photon emission tomography (SPET) imaging for the diagnosis and localization of CAD late after acute myocardial infarction. Dobutamine (up to 40 μg kg^–1 min^–1)-atropine (up to 1 mg) stress echocardiography in conjunction with stress-reinjection ²⁰¹Tl SPET was performed for the evaluation of myocardial ischaemia in 90 patients with previous myocardial infarction who underwent coronary angiography. Significant CAD was predicted on bases of myocardial ischemia (new or worsening wall motion abnormalities on echocardiography and reversible perfusion defects on ²⁰¹Tl SPET). Significant CAD (≥ 50% luminal diameter stenosis) was detected in 73 (81%) patients. The sensitivity, specificity and accuracy of echocardiography in detecting remote ischaemia for the diagnosis of remote CAD (present in 53 patients) were, respectively, 79% (CI 70%–88%), 85% (CI 77%–93%) and 81% (CI 73%–90%), while the corresponding figures for ²⁰¹Tl SPET were 75% (CI 66%–85%), 78% (CI 69%–87%) and 76% (CI 67%–86%) respectively (P = NS vs echocardiography). The sensitivity, specificity and accuracy of echocardiography in detecting peri-infarction ischaemia for the diagnosis of infarct-related artery stenosis (present in 70 patients) were, rspectively, 77% (CI 68%–86%), 85% (CI 78%–92%) and 79% (CI 70%–87%) while the corresponding figures for ²⁰¹Tl SPET were 73% (CI 64%–82%), 85% (CI 78%–92%) and 76% (CI 67%–84%) respectively (P = NS vs echocardiography). The agreement between the two methods for the diagnosis of peri-infarction and remote ischaemia was 70% (kappa = 0.37) and 80% (kappa = 0.59) respectively. It is concluded that dobutamine stress echocardiography and ²⁰¹Tl SPET have comparable accuracy for the diagnosis of infarct related and remote CAD in patients with previous myocardial infarction. The agreement between the methods is higher for the diagnosis of remote CAD than for that of peri-infarction ischaemia. Received 17 October 1998 and in revised form 5 January 1999     

Prediction of cardiac events in patients with dilated cardiomyopathy using <Superscript>123</Superscript>I-BMIPP and <Superscript>201</Superscript>Tl myocardial scintigraphy

Objective Various clinical trials for dilated cardiomyopathy (DCM) have demonstrated that the prognosis as well as cardiac function is improved by the administration of beta-blocker therapy. On the other hand, ¹²³I-betamethyl-p-iodophenyl-pentadecanoic acid (BMIPP) reflects myocardial fatty acid metabolism and is considered to be a more sensitive tracer than perfusion tracers. In this study, the efficacy of DCM for the evaluation of myocardial damage and the prediction of cardiac events was studied using ¹²³I-BMIPP and ²⁰¹TI (Tl) myocardial scintigraphy. Methods Study subjects comprised 33 DCM patients, divided into a cardiac event group (event, n = 9) and an event-free group (event free, n = 24). An extent score (ES) and severity score (SS) were calculated for each BMIPP image. BMIPP and Tl images were divided into 17 segments, and total defect scores (TDS) were calculated for each. The TDS of the BMIPP and Tl images were compared with score differences greater than or equal to 4 and less than 4 defined as mismatch and non-mismatch, respectively. Results The TDS of BMIPP was significantly higher in the event group than in the event-free group (P < 0.05). The ES and SS were significantly higher in the event group than in the event-free group (P < 0.01). The comparison in the 2 × 2 contingency tables showed that the occurrence of non-mismatch was significantly higher in the event-free group (χ² test; P < 0.01). The ES of BMIPP was a significant predictor of cardiac events in the multivariate analysis (P < 0.01). Conclusions These results suggest that the ES for BMIPP is useful as a predictor of cardiac events in DCM.     

Relation between myocardial uptake of thallium-201 chloride and fluorine-18 fluorodeoxyglucose imaged with single-photon emission tomography in normal individuals

Recently, we have demonstrated the feasibility of imaging myocardial uptake of fluorine-18 fluorodeoxyglucose (FDG) with single-photon emission tomography (SPET) using a specially designed collimator. Thallium-201 was used to determine distribution of perfusion for comparison with FDG uptake. However, regional²⁰¹Tl and FDG activities may be different, based on differences in tracer attenuation and the use of different collimators. To study the relation between tracer activities imaged with SPET, nine healthy individuals underwent resting²⁰¹Tl SPET and FDG SPET during a hyperinsulinaemic euglycaemic clamp. The SPET data were analysed semiquantitatively, using circumferential profiles. Mean profiles of midventricular short-axis slices showed no significant difference between²⁰¹Tl and FDG activity. Regional fluctuations were similar for FDG and²⁰¹Tl; the highest tracer activities were observed in the lateral wall and the lowest activities in the septum. Finally, pooled data (n=1620 segmental activities) in nine individuals showed a linear correlation (P<0.0001) between²⁰¹Tl and FDG activity: FDG=0.76²⁰¹Tl + 0.23 (r=0.70). These data demonstrate the absence of major differences between regional²⁰¹Tl and FDG activity in normal myocardium, suggesting that no separate²⁰¹Tl and FDG SPET reference values are needed for comparison with patient studies.     

Prognostic value of iodine-123 labelled BMIPP fatty acid analogue imaging in patients with myocardial infarction

This study was undertaken to evaluate the prognostic value of iodine-123 labelled 15-iodophenyl3-R,S-methyl pentadecanoic acid (BMIPP) imaging in patients with myocardial infarction. BMIPP is an iodinated methyl branched fatty acid analogue which is trapped in the myocardium with little washout, thereby reflecting fatty acid utilization in the myocardium. We previously reported that in patients with myocardial infarction, regions are often observed where reduced BMIPP uptake is seen relative to thallium-201 perfusion at rest. However, the clinical significance of such discordant BMIPP uptake remains unknown. Fifty consecutive patients with chronic myocardial infarction referred for stress thallium scan and coronary arteriography underwent BMIPP imaging at rest. Each patient was in a stable condition at the time of the radionuclide study. Follow-up was performed at a mean interval of 23 months to investigate the prognostic implications of the radionuclide studies. Nine patients had cardiac events during the follow-up period. Univariate analysis showed that the number of discordant BMIPP versus²⁰¹TL uptake segments was the best predictor of future cardiac events (P=0.0245), followed by the presence of discordant BMIPP uptake (P=0.0388) and the number of²⁰¹TL redistribution segments (P=0.0444). When all the clinical and radionuclide variables were analysed by Cox regression analysis, the presence of discordant BMIPP uptake was the best, and an independent, predictor of future cardiac events (²=8.5) followed by the number of coronary stenoses on angiography (²=3.9). These preliminary data suggest that decreased BMIPP uptake relative to²⁰¹TL is a valuable predictor of future cardiac events in patients with myocardial infarction. Areas with such discordant BMIPP uptake may contain jeopardized myocardium where fatty acid utilization has been severely suppressed relative to myocardial perfusion.Presented in part at the 40th Annual Meeting of Society of Nuclear Medicine at Orlando, Florida, June 1994     

Therapeutic effect of co-enzyme Q10 on idiopathic dilated cardiomyopathy: assessment by iodine-123 labelled 15-(p-iodophenyl)-3(R, S)-methylpentadecanoic acid myocardial single-photon mission tomography

It has been reported that myocardial mitochondrial function can be improved by the administration of co-enzyme Q10 (CoQ10). Recently, iodine-123 labelled 15-(p-iodophenyl)-3-(R, S)-methylpentadecanoic acid (BMIPP) was developed for metabolic imaging using single-photon emission tomography (SPET). This study was conducted to determine whether the therapeutic effects of CoQ10 on idiopathic dilated cardiomyopathy can be evaluated by BMIPP myocardial SPET. Fifteen patients, comprising 14 men and one woman (mean age: 64±12 years), were examined. CoQ10 was administered at 30 mg/day for a period of 35.7±12.4 days. BMIPP myocardial SPET was carried out belote and after CoQ 10 treatment. The count ratio of the heart (H) to the upper mediastinum (M) (H/M ratio) was calculated using a region of interest method with anterior planar imaging. Representative short-axis tomograms were divided into 27 segments (three slicesxnine segments). Each segmental score was analysed semiquantitatively using a four-point scoring system (normal=0, mild low uptake=1, severe low uptake=2, defect=3). The H/M ratio showed a significant improvement., from 2.39±0.39 to 2.54±0.47, after treatment (P<0.05). The BMIPP total defect score after CoQ10 treatment was significantly decreased to 10.1±43, compared to 13.9±4.5 without CoQ10 treatment (P<0.001). However, the percent fractional shortening measured using echocardiography was not significantly different before and alter CoQ treatment (19.2±8.1 vs 19.7±7.1). BMIPP myocardial SPET was confirmed to be sensitive in evaluating the therapeutic effects of CoQ 10 in patients with idiopathic dilated cardiomyopathy. This method is unique, since the therapeutic effects can be estimated from the perspective of metabolic SPET imaging.     

Clinical value of triple-energy window scatter correction in simultaneous dual-isotope single-photon emission tomography with123I-BMIPP and201TI

To improve the image quality in simultaneous dual-isotope single-photon emission tomography (SPET) with iodine-123 labelled 15-(p-iodophenyl)-3-methylpentadecanoic acid (BMIPP) and thallium-201, we applied the triple-energy window method JEW) for correction of the cross-talk and scatter artifact. Seventy-one patients with coronary artery disease were included.²⁰¹T1 cross-talk into the¹²³I acquisition window (group 1,n = 30) and¹²³I cross-talk into the²⁰¹Tl window (group 2,n = 41) were studied. In group 1,¹²³I images were first obtained (single-isotope images), followed by²⁰¹Tl injection and SPET acquisition using dual-isotope windows (dual-isotope images). In group 2, the order was reversed. The dual-isotope SPET images with and without TEW were compared with the single-isotope images. Qualitative evaluation was performed by scoring the segmental defect pattern. Detectability of the mismatched fatty acid metabolism on dual-isotope SPET was evaluated by receiver operating characteristic (ROC) curve analysis. Segmental defect pattern agreement between dual and corrected single images was significantly improved by TEW correction (P<0.01). The agreement was particularly improved in segments with absence of uptake. There was no significant difference between TEW-corrected dual-isotope SPET and corresponding single-isotope SPET with regard to either % defect count or background activity. Mismatched fatty acid metabolism depicted by dual-isotope SPET predicted abnormal wall motion more accurately with TEW than without TEW. With TEW, a practical method for scatter and cross-talk correction in clinical settings, simultaneous dual¹²³I-BMIPP/²⁰¹Tl SPET is feasible for the assessment of myocardial perfusion/metabolism mismatch.     

Ischemic “memory image” in acute myocardial infarctio of123I-BMIPP after reperfusion therapy: A comparison with99mTc-pyrophosphate and201Tl dual-isotope SPECT

Ischemic "memory image" is a phenomenon of 123I-15-(p-iodophenyl)-3-(R,S)-methylpentadecanoic acid (BMIPP) in which an area at risk of acute myocardial infarction (AMI), could be detected as a defect in a couple of weeks even after successful reperfusion therapy. The purpose of this study was to clarify the incidence of the ischemic "memory image" of 123I-BMIPP in patients with AMI by comparing 99mTc-PYP and 201Tl dual-isotope SPECT. Materials consisted of 14 patients with successfully reperfused AMI and 20 patients with old myocardial infarction (OMI). All AMI patients underwent PYP/Tl dual-isotope SPECT within 1 week after the onset of AMI, and BMIPP SPECT was performed within 1 week after the PYP/Tl dual-isotope SPECT. The extent and severity of the defect of BMIPP and Tl were visually scored into four grades: 0 = no defect to 3 = large or severe defect. These scores were compared. PYP positive AMI lesions were concordant with BMIPP defects (13/14). In AMI, both the extent and severity scores of BMIPP were higher than 201Tl (p < 0.001). Differences (BMIPP - Tl) of extent and severity scores were greater in AMI than in OMI (p < 0.001). In conclusion, the ischemic "memory image" obtained by means of the BMIPP is a common phenomenon (13/14) in AMI, and helpful in evaluating the area at risk.     

Nitrate administration to enhance the detection of myocardial viability by technetium-99m tetrofosmin single-photon emission tomography

A comparison was performed between technetium-99m tetrofosmin myocardial perfusion tomography at baseline and after nitrate administration, using a 2-day protocol, and rest-reinjection thallium-201 single-photon emission tomography (SPET) studies in order to assess whether nitrates enhance the detection of viable myocardium with^99mTc-tetrofosmin. Fifteen patients with coronary artery disease, previous myocardial infarction and a left ventricular ejection fraction <40% underwent²⁰¹T1 rest-injection and^99mTc-tetrofosmin. baseline-postnitroglycerin (0.4 mg sublingually) SPET studies, within 48 h. Tomograms based on the three spatial planes were divided into 15 segments and regional tracer uptake was quantitatively analysed. Viability was defined as presence of tracer uptake >50% of peak activity on baseline studies or after reversibility. The percentage of peak activity of^99mTc-tetrofosmin at baseline correlated with that of 201T1 (r=0.82,P <0.001). On baseline^99mTc-tetrofosmin studies, 73 of the 225 segments that were analysed had <50% of peal. activity. Fifteen percent of these segments showed reversibility after nitrate administration, with an increase in^99mTc-tetrofosmin uptake from 40%±9% to 57%±9% of peak activity (P=0.003). All reversible segments after nitrate administration had viability criteria on²⁰¹Tl studies, but 20 segments that were non-viable on^99mTc-tetrofosmin. studies were viable on²⁰¹Tl studies. Using a threshold value of >40% of peak activity, only seven segments remained non-viable on^99mTc-tetrofosmin studies. Overall agreement between^99mTc-tetrofosmin with nitrates and²⁰¹Tl-reinjection regarding the presence of myocardial viability was 90%. Detection of myocardial viability with^99mTc-tetrofosmin. was enhanced after nitrate administration, correlating with viability criteria observed on thallium studies.     

Assessment of myocardial perfusion and viability with technetium-99m methoxyisobutylisonitrile and thallium-201 rest redistribution in chronic coronary artery disease

We compare thallium-201 rest redistribution and fluorine-18 fluorodeoxyglucose ([¹⁸F]FDG) for the assessment of myocardial viability within technetium-99m methoxyisobutylisonitrile (MIBI) perfusion defects in 27 patients with chronic stable coronary artery disease. The following studies were performed: (1) stress^99mTc-MIBI, (2) rest^99mTc-MIBI, (3)²⁰¹T1 rest-redistribution single-photon emission tomography, (4) [¹⁸F]FDG positron emission tomography. The left ventricle was devided into 11 segments on matched tomographic images. The segment with the highest activity at stress was taken as the reference (activity=100%). Perfusion defects at^99mTc-MIBI rest were classified as severe (activity<50%), moderate (activity 50%–60%) or mild (activity 60%–85%). Uptakes of [¹⁸F]FDG and rest-redistributed²⁰¹Tl were recognized as significant if they exceeded 50% of that in the reference segment. Among the 33 segments with severe^99mTc-MIBI rest perfusion defects, 21 had significant [¹⁸F]FDG and 10 significant rest-redistributed²⁰¹Tl uptake. As regards the 37 segments with moderate defects, [¹⁸F]FDG was present in 29 and²⁰¹Tl in 31, while of the 134 segments with mild defects, 128 showed [¹⁸F]FDG uptake, and 131,²⁰¹Tl uptake. In conclusion, there is an inverse relationship between the severity of^99mTc-MIBI perfusion defects and the uptake of rest-redistributed²⁰¹Tl and [¹⁸F]FDG. Both tracers are adequate markers of viability in mild and moderate defects; in severe defects²⁰¹Tl might underestimate the presence of viability as assessed by [¹⁸F]FDG.     

Myocardial infarction in rats: high-resolution single-photon emission tomographic imaging with a pinhole collimator

The purpose of this study was to evaluate the accuracy of myocardial imaging by means of high-resolution single-photon emission tomography (SPET) with a pinhole collimator in rats with experimental infarction. Myocardial infarctions were induced in male Wistar rats by ligation of the left coronary artery for 30 min, followed by reperfusion. Two days after the reperfusion, pinhole SPET was performed after the intravenous administration of 111 MBq of thallium-201 chloride, using a rotating gamma camera equipped with a pinhole insert (2.0-mm aperture) in a low-energy pinhole collimator. SPET projection data were collected at 6° increments over 360° using a 4-cm radius of rotation to reconstruct the short- and long-axis images. Projection data were acquired in 15 or 30 s, the SPET imaging being accomplished within 40 min after the injection of²⁰¹T1. After SPET, the rats were sacrificed to remove the hearts for autoradiography (ARG) and nitroblue tetrazolium (NBT) staining as a visual correlative study. Quantitative correlative studies between pinhole SPET and ARG were performed with linear regression analysis for infarct size and distribution properties (relative counts on SPET images and relative density on autoradiographs) on the short-axis sections. All infarcts (4 mm in minimum diameter) in seven rats were detected by pinhole SPET. The SPET images in rats with or without myocardial infarction were consistent with the findings of ARG and NBT staining. There were significant correlations between pinhole SPET and ARG with respect to the infarct size (r=0.933,P <0.001;n=15) and the relative radiotracer distribution (r=0.931,P <0.001; n=68). This study therefore confirmed the accuracy of myocardial pinhole SPET imaging in rats with myocardial infarction. This method may partially substitute for ARG and prove useful for assessing new myocardial imaging agents in vivo in small laboratory animals.     

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     

Prognostic investigations after myocardial infarction: A comparison of radionuclide angiography and 201Tl scintigraphy

The ability of pre-discharge thallium Tl201 scintigraphy and radionuclide angiography (RNA) to predict subseqeunt cardiac events was investigated in 46 apparently low-risk survivors of a first acute myocardial infarction. All patients underwent selective coronary arteriography at 3 months post-discharge. At the time of the initial investigation, half were beta-blocked, and thereafter, all patients were given prophylactic beta-blockade. During a mean follow-up period of 12±4 months, 14 patients (30%) experienced cardiac events, i.e. recurrent myocardial infarction (3 patients), angina pectoris (13 patients) and coronary surgery (8 patients). No patient died during the follow-up period. Of the 14 with subsequent cardiac events, 11 were identified by the presence of a reversible perfusion defect at ²⁰¹Tl scintigraphy, while 7 exhibited abnormal left ventricular exercise reserve on RNA. The predictive accuracy of ²⁰¹Tl (85%) for subsequent cardiac events exceeded that of RNA (56%; P<0.01) and of arteriographic multi-vessel disease (65%; P<0.05). The sensitivity of the non-invasive techniques was not influenced by beta-blockade at the time of investigation. Thus, ²⁰¹Tl scintigraphy appears to be the more accurate technique for the assessment of the prognosis of apparently low-risk patients following myocardial infarction. The accuracy of the technique was not reduced by beta-adrenergic blockade.     

Prognostic value of single-photon emission tomography in acute ischaemic stroke

Single-photon emission tomography (SPET) is widely used in the investigation of acute stroke. We investigated the relationship between SPET data and functional outcome in a large group of acute stroke patients. One hundred and eight patients underwent cerebral computed tomography (CT) and technetium-99m hexamethylpropylene amine oxime SPET after acute ischaemic stroke. We categorised the clinical presentation according to the Oxford classification of acute stroke. Outcome was measured 1 year after stroke using mortality and the Barthel Index for survivors. SPET scans were interpreted without reference to the clinical data using a semi-automatic technique. Three experienced observers determined the presence of luxury perfusion using suitably scaled SPET images in conjunction with the CT scan. Both SPET volume and severity of deficit were significantly negatively correlated with Barthel Index at 1 year (r _s=–0.310,P<0.0001, andr _s=–0.316,P<0.0001 respectively). In patients scanned with SPET within 16 h of stroke onset, the correlations were more strongly negative (r _s=–0.606,P<0.0001, andr _s=–0.492,P<0.005 respectively). Luxury perfusion was not associated ( ²=0.073,df=1,P=0.79) with good functional outcome (Barthel score 60). Stepwise logistic regression identified Oxford classification, total deficit volume and patient's age as significant predictors of functional outcome. Overall predictive accuracy was 72%. Predictive accuracy was better in patients who received SPET within 16 h of stroke onset. SPET provides useful information about the functional outcome of acute stroke at 1 year. However, the accuracy of prediction decreases the longer SPET is delayed. Prognostication using SPET in combination with clinical assessment and other investigations may also be considered.     

Attenuation correction improves the detection of viable myocardium by thallium-201 cardiac tomography in patients with previous myocardial infarction and left ventricular dysfunction

The aim of this study was to determine the influence of attenuation-corrected thallium-201 stress/redistribution/reinjection single-photon emission tomography (SPET) on the number of viable segments in patients with previous myocardial infarction and dysfunctional myocardium. Fifty-one patients with previous myocardial infarction and left ventricular dysfunction were included in the study. In all patients, ²⁰¹Tl non-corrected (NC) and attenuation-corrected (AC) SPET was performed using a stress/redistribution/reinjection protocol followed by coronary angiography. A semiquantitative analysis was performed using polar maps for NC and AC stress, redistribution and reinjection short-axis and vertical long-axis (apex) slices. Severe (perfusion defect below 50%/maximal count rate: PD_<50), mild and moderate persistent defects for redistribution and reinjection were evaluated for both NC and AC studies. A total of 1581 segments were evaluated by semiquantitative segmental analysis for both NC and AC studies for each redistribution and reinjection map. In the redistribution maps, NC revealed a total of 352 segments and AC a total of 222 segments with impaired perfusion below 50% of the maximal count rate (PD_<50). The mean number of affected segments was 6.9±5.5 in the case of NC and 4.4±4.8 in the case of AC (P<0.001). In the reinjection maps, NC revealed a total of 263 non-viable segments (PD_<50) and AC a total of 169 non-viable segments. The mean number of affected segments was 5.2±5.3 in the case of NC and 3.3±4.2 in the case of AC (P<0.001). Recovery of function was better predicted by AC than by NC in 20% of patients in the follow-up group. Therefore, the use of attenuation correction influences the extent of viable segments by showing more viable segments in either redistribution or reinjection maps. ²⁰¹Tl imaging without attenuation correction may underestimate the extent of tissue viability, which may contribute to the lower sensitivity compared to fluorine-18-fluorodeoxyglucose positron emission tomography, where attenuation correction is a routinely performed procedure. Received 26 October and in revised form 23 December 1998     

Prospective evaluation of thallium-201 reinjection in single-vessel coronary patients undergoing coronary bypass surgery

Twenty-two patients with single-vessel left anterior descending coronary artery disease were investigated by means of dipyridamole stress thallium-201 myocardial perfusion scintigraphy, using single photon emission tomography (SPET), 1 week before and 2–5 weeks after coronary bypass surgery. The dose of dipyridamole was 0.56 mg/kg, and the injected activity of ²⁰¹T1 was 74 MBq. Before surgery, and after completion of the redistribution study, a further 37 MBq of ²⁰¹T1 was injected. Ten minutes and 1 h later, repeated SPET imaging were performed. SPET images were evaluated both subjectively and semiquantitatively, using a five-grade segmental defect score system, with higher scores for more severe perfusion defects. Before surgery, the 3-h redistribution images revealed complete or partial persistence of the perfusion defects in all patients. On the images taken 10 min after reinjection, these defects were completely filled in four cases, and partially filled in ten cases. Further positive changes were observed on the 1-h post-reinjection images in four cases. Three of the 1-h post-reinjection images exhibited a paradox redistribution. The stress images after surgery corresponded well to the ²⁰¹T1 distribution on the preoperative 1-h post-reinjection images in 11 cases. The average of the segmental defect severity scores was 17.0 after stress, 10.1 at rest, 7.1 10 min after reinjection and 6.4 1 h after reinjection. After surgery, the average of both the post-stress and the 3-h redistribution scores was 3.1. The correlation coefficients between the segmental scores of the postoperative resting study and the preoperative 3-h resting and the 10-min and 1-h post-reinjection studies were 0.72, 0.69 and 0.78, respectively. It is concluded that post-reinjection ²⁰¹T1 images before surgery are good predictors of myocardial perfusion after revascularization. The best results are obtained if imaging is performed 1 h after reinjection. Correspondence to: J. Mester     

A partial defect in technetium-99m pyrophosphate image suggesting cardiac rupture following acute myocardial infarction

We present the case of a 70-year-old woman with acute myocardial infarction who died of cardiac rupture on the 2nd hospital day. Dual isotope single photon emission computed tomography (SPECT) using thallium-201 chloride and technetium-99m pyrophosphate (PYP) performed on the 2nd hospital day showed a large perfusion defect in the anteroseptal wall on ²⁰¹Tl image and a increased accumulation on ^99mTc-PYP image in the anterior area consistent with a partial defect. Autopsy performed 1 h after death revealed a tear in the left ventricular anterior wall consistent with the defect on the ^99mTc-PYP image. We propose that the finding of a partial defect in ^99mTc-PYP is an interesting finding which may be associated with cardiac rupture following acute myocardial infarction. Offprint requests to: M. Hiroe