Planar myocardial perfusion imaging with technetium-99m-teboroxime: comparison by vascular territory with thallium-201 and coronary angiography.

Myocardial perfusion agents labeled with 99mTc offer improved physical imaging properties compared to 201TI. Teboroxime is a new 99mTc-labeled compound for myocardial perfusion imaging that shows a high myocardial extraction and rapid clearance. Sixty-seven patients underwent planar teboroxime imaging with a rapid acquisition protocol. Agreement of teboroxime and 201TI for the presence or absence of disease occurred in 56/65 patients (86%). There was agreement (normal or abnormal) between the two agents in 156/195 vessels (80%) and 457/585 segments (78%). When abnormal segments (ischemia or infarction) were compared, teboroxime showed significantly more ischemic segments (89/135, 66%) than did 201TI (73/135, 54%, p < 0.05). Teboroxime offers accuracy comparable to 201TI for the diagnosis of coronary artery disease and may improve the detection of ischemic or viable myocardium. In addition, its rapid myocardial clearance permits stress/rest imaging in 60-90 min.     

Clinical usefulness of exercise/rest 99mTc-teboroxime SPECT imaging: results of a Japanese multi-center phase II study]

99mTc-Teboroxime [Chloro[tris(cyclohexyldioxime)methaneboronic acid] (99mTc)technetium], a perfusion agent for myocardial imaging, has a distinct advantage over 201Tl because of its very high myocardial extraction and is a 99mTc compound ideal for gamma camera imaging. This agent also demonstrates rapid myocardial washout, which allows completion of exercise and rest imaging studies in a short interval (to 1 hour). However, the rapid washout necessitates the completion of image acquisition very quickly after injection and therefore may require nonconventional SPECT imaging. In this Phase II study we evaluate the safety and efficacy of 99mTc-Teboroxime to detect coronary artery disease by exercise and rest SPECT imaging in 38 patients with prior myocardial infarction, 31 patients with angina pectoris, and 4 patients with non-coronary cardiac diseases. The 99mTc-Teboroxime dose used was 370-740 MBq in each study. The findings were compared with coronary angiography or 201Tl exercise and redistribution SPECT. No significant adverse reactions or laboratory abnormalities attributable to 99mTc-Teboroxime were observed. The quality of SPECT images was optimal in 62.5% of all patients. The relatively large population of suboptimal cases (37.5%) was attributed to the delay of the start and prolongation of the image acquisition time. In 85.7% of patients whose imaging was started within 5 minutes and completed within 11 minutes after injection, optimal quality was observed. Thus, 99mTc-Teboroxime SPECT requires the rapid completion of image acquisition after injection to achieve optimal image quality. Abnormalities of 99mTc-Teboroxime distribution were detected in 97.1% and 62.1% of patients with prior myocardial infarction or angina pectoris, respectively. The concordance with coronary angiography was 84.4% and 68.0%, and with 201Tl was 78.1% and 74.1%, respectively. Although standardization of the image protocol suitable for this agent is needed for the next study, these high correlations suggest the potential usefulness of 99mTc-Teboroxime SPECT imaging.     

Characteristics of the myocardial SPECT images of 99mTc-MIBI and 99mTc-teboroxime]

Characteristics of the myocardial distribution of 99mTc-MIBI and 99mTc-Teboroxime was compared with the myocardial distribution of 201Tl. We made summed myocardial images, in which central three short-axis SPECT slices were added. Rectangular region of interest (ROI) was set on each myocardial segment, and mean counts of each myocardial region was obtained using summed short-axis images. The ratio of inferior-to-anterior mean counts (I/A) was 0.69 +/- 0.20 in 99mTc-MIBI and 0.62 +/- 0.16 in 201Tl. The ratio of inferior-to-lateral mean counts was 0.70 +/- 0.18 and 0.65 +/- 0.13, respectively. Both ratios in 99mTc-MIBI were significantly higher than those in 201Tl (p less than 0.05). 201Tl to 99mTc-MIBI ratios of these two values were 1.11 +/- 0.17 (I/A) and 1.08 +/- 0.16 (I/L). The ratios of I/A and I/L of 99mTc-MIBI were about 10 percent higher than those of 201Tl. 99mTc-Teboroxime dynamic short-axis SPECT images of every three-minute were obtained. The ratios of counts in each wall were calculated similarly. After about 8 minutes, gradual increase in hepatic activity can be a cause of quantitative error in the assessment of SPECT images. We obtained the data with a human cardiac phantom. The myocardial phantom filled with 99mTc or 201Tl was placed in the mediastinal portion that is surrounded by the lung (saw dust) and vertebra (plastic bar). The ratio of I/A was 0.79 and I/L was 0.85 in 201Tl. The I/A ratio was 0.93 and I/L was 0.97 in 99mTc. Both ratios in 99mTc were about 15 percent higher than those in 201Tl.(ABSTRACT TRUNCATED AT 250 WORDS)     

Diagnostic value of a new myocardial perfusion agent, 99mTc-teboroxime (SQ30,217) in patients with coronary artery disease, utilizing a SPECT imaging protocol: a multicenter phase III clinical trial]

Technetium-99m teboroxime (TEBO) is a new technetium-based myocardial perfusion imaging agent, which has high myocardial extraction and rapid myocardial washout. Its rapid myocardial washout may necessitate rapid imaging protocols. This study was designed to perform exercise/rest SPECT imaging protocols with rapid data acquisition (from 2.8 +/- 1.4 min to 11.2 +/- 4.1 min after injection) in 171 patients with coronary artery disease, 15 patients with cardiomyopathy and 8 patients with other heart disease. The rapid imaging protocols resulted in a high prevalence of good image quality. The diagnostic value of TEBO was recognized from the high concordance of image findings with thallium-201 (201Tl) scintigraphy, 88.2% in the exercise protocol and 89.9% in the rest protocol. Also, the sensitivity and specificity of TEBO for detecting coronary artery disease were comparable (86.6% and 53.9%, respectively) with those of 201Tl (90.7% and 46.2%, respectively). No toxic effects of TEBO were observed in subjective and objective clinical findings and blood examinations. TEBO was finally evaluated to be useful in 98.4% of the patients. Thus, this agent has good clinical potential for myocardial perfusion imaging.     

Preliminary report of SPECT imaging with Tc-99m teboroxime in ischemic heart disease.

Tc-99m teboroxime (Cardiotec) is one member of a new class of radiopharmaceuticals, the BATO agents (boronic acid adducts of technetium dioxime). This agent is a small, neutral, lipophilic compound with a high myocardial extraction (approximately 85% to 90%), and its uptake in the heart is directly related to myocardial perfusion. Tc-99m teboroxime washes out rapidly from the heart, and its potential for SPECT imaging has therefore been questioned. Tc-99m teboroxime SPECT imaging was compared prospectively with thallium SPECT (20 of 20 patients) and coronary arteriography (17 of 20 patients) suspected of having coronary artery disease. In this small preliminary series, both Tc-99m teboroxime and thallium SPECT detected all abnormal patients (12 of 12) and predicted correctly the site of critical stenosis in 20 of 24 diseased arteries (83%). Tc-99m teboroxime SPECT was normal in 5 of 6 patients without evidence of disease. Several cases occurred of clearly different radiotracer distribution (not related to obvious artifacts) with teboroxime compared with thallium, and lesion size was significantly larger on teboroxime compared with thallium SPECT. The clinical significance of these differences is not yet clear. Tc-99m teboroxime SPECT is possible with imaging times less than half those of thallium SPECT. Though much work remains to be done, teboroxime, because of its unique kinetics, creates many new possibilities for the evaluation of ischemic heart disease.     

Clinical comparison of technetium-99m-teboroxime and thallium-201 utilizing a continuous SPECT imaging protocol.

To examine the advantages of a 99mTc-labeled cardiac perfusion agent, teboroxime or SQ30,217 (Squibb Diagnostics), a prospective study was undertaken comparing it to 201Tl stress testing in 17 patients suspected or known of having coronary artery disease (CAD). All patients were studied utilizing a single-detector SPECT camera with a continuous acquisition imaging protocol. Testing was performed on a treadmill to comparable levels with both agents within a 2-wk period. Concordance between the two studies on a patient by patient basis was seen in 16/17 (94%) patients, and discordance was seen in 1/17 (6%) patients. Comparison of findings between 201Tl and 99mTc-teboroxime on a segment by segment basis showed concordance in 107/119 (90%) segments, and 12/119 (10%) were discordant. Both examinations independently detected an equal number of normal (77) and abnormal (42) segments. There was no significant difference between the two agents in classifying lesions as ischemic, although there were significant differences between thallium and teboroxime in classifying infarct and infarct/ischemia. Technetium-99m-teboroxime SPECT imaging is a clinically useful method for detecting CAD, with a major advantage being the shorter examination time per individual patient study. The mean total examination time for completion of the 99mTc-teboroxime study was 2.5 hr versus 4.0 hr for 201Tl.     

Photon energy recovery for crosstalk correction in simultaneous 99mTc/201Tl imaging.

Simultaneous 99mTc sestamibi/201Tl imaging enables the acquisition of images of myocardial stress perfusion and myocardial viability in a single process. One of the major limits of this technique is the crosstalk of the 99mTc downscattered photons into the 201Tl window. We propose using the spectral deconvolution technique photon energy recovery (PER) for correcting this crosstalk. METHODS: A planar line phantom made of 99Tc vertical lines and 201Tl horizontal lines and a cardiac SPECT phantom including an anterior (2 mL) and an inferior (1.5 mL) myocardial fixed defect were used. The phantoms were filled with an initial 99mTc/201Tl ratio of 5:1. Several successive acquisitions were made from time t = 0 to time t = 48 h (99mTc/201Tl ratio approximately 0) without moving the phantoms. Total number of counts, contrast, and normalized SD (NSD) were calculated on the Tl-raw and the Tl-PER planar images. SPECT datasets were analyzed. The Tl-raw images recorded at 48 h were considered the reference "virgin" 201Tl images. RESULTS: Total number of counts, contrast, and NSD ranged from 336% to 201%, 15% to 29%, and 257% to 225% of the virgin 201Tl values, respectively, for Tl-raw planar images; whereas values for Tl-PER images ranged from 128% to 108%, 61% to 79%, and 154% to 108%, respectively. Anterior and inferior defect contrasts ranged from 1.18 to 1.22 and 1.12 to 1.16 for Tl-raw SPECT images, respectively; whereas for Tl-PER images, value ranges were 1.28-1.32 and 1.21-1.24, respectively. The corresponding reference virgin 201Tl values were 1.31 and 1.25 respectively. Summed score, average defect severity, and average defect extent ranges were 4-5, 0.4-0.52, and 4.7-5.9 for Tl-raw images, respectively, and 8-9, 0.59-0.79, and 7.4-8.8 for Tl-PER images. The reference virgin 201Tl values were 9, 0.73, and 8.7, respectively. CONCLUSION: PER is quantitatively efficient to remove 99mTc crosstalk photons from 201Tl images for 99mTc/201Tl ratios ranging from 5:1 to 2:1.     

Rapid myocardial perfusion imaging with 99Tcm-teboroxime and a three-headed SPECT system: a comparative study with 201Tl.

99Tcm-teboroxime is a new myocardial perfusion agent with a high first pass extraction and rapid myocardial washout. The usefulness of 99Tcm-teboroxime was evaluated for detection of myocardial ischaemia using a three-headed single photon emission tomography (SPECT) system which allows for rapid data acquisition. The subjects consisted of 14 patients, including seven with ischaemic heart disease, four with cardiomyopathy and three others. After the 99Tcm-teboroxime injection, dynamic data was collected every minute for 15 min with continuous rotation. High-quality SPECT images could be obtained by reconstructing the serial scans from 2 to 8 min. The sensitivity, specificity and accuracy of the 99Tcm-teboroxime study for the detection of the ischaemic region were not significantly different from those of the 201Tl study. Myocardial clearance was slow in the ischaemic lesion and in the myocardium of cardiomyopathy patients, while the coronary angiograms did not show any abnormality. These results therefore indicate that the rapid SPECT imaging and myocardial clearance of 99Tcm-teboroxime obtained with a three-headed SPECT system were useful for the detection of myocardial ischaemia.     

New color imaging of [99mTc]-pyrophosphate and [201Tl]-chloride dual isotope single photon emission computed tomography in acute myocarditis

[99mTc]-pyrophosphate (PYP) and [201Tl]-chloride dual isotope single photon emission computed tomography (SPECT) is now available to detect the site and extent of acute myocardial infarction. In inflammatory myocardial disease, [99mTc]PYP makes hot image on damaged area. We performed dual isotope SPECT of [99mTc]PYP and [201Tl]Cl in two patients with acute myocarditis and severe rhythm disturbance to evaluate the severity of inflammation. Myocardial damage was estimated by [201Tl] perfusion coloring blue and myocardial inflammation was estimated by [99mTc]PYP uptake coloring red. The overlap display of both images made it clear to detect spatial extent of myocardial inflammation. Using this technique, we expect to estimate the severity of myocarditis and to make a decision of therapeutic plan.     

Evaluation of myocardial viability following acute myocardial infarctic using201Tl SPECT after thallium-glucose-insulin infusion —Comparison with18F-FDG positron emission tomography—

OBJECTIVE AND METHODS: The aim of this study was to evaluate myocardial viability in patients after acute myocardial infarction (AMI). We compared 201Tl SPECT after 201Tl with GIK (10% glucose 250 ml, insulin 5 U and KCl 10 mEq) infusion (GIK-201Tl) with resting 201Tl and 99mTc-pyrophosphate (PYP) dual SPECT, positron emission computed tomography (PET) using 18F-fluorodeoxyglucose (18F-FDG) in 21 patients with their first AMI, who all underwent successful reperfusion. GIK-201Tl SPECT, 201Tl and 99mTc-PYP dual SPECT were done within 10 days after admission and 18F-FDG-PET was performed at 3 weeks. GIK-201Tl SPECT was obtained after 30 min of GIK-201Tl infusion. 18F-FDG (370 MBq) was injected intravenously after oral glucose (1 g/ kg) loading, and then PET was obtained. PET and SPECT images were divided into 20 segments. Regional tracer uptake was scored using a 4-point scoring system (3 = normal to 0 = defect), and summed to a regional uptake score (RUS). Regional area means the infarcted area in which 99mTc-PYP accumulated. The number of decreased uptake segments (ES) was then determined. The infarcted area was defined as the area of 99mTc-PYP uptake. RESULTS: The ESs for the GIK-201Tl and 18F-FDG-PET images were significantly lower than the number of 99mTc-PYP uptake segments. The RUS for GIK-201Tl was higher than that for resting-201Tl imaging and similar to those for 18F-FDG-PET. CONCLUSIONS: In the detection of myocardial viability following AMI, GIK-201Tl imaging is useful with findings similar to those of 18F-FDG-PET.     

Uptake of myocardial imaging agents by rejecting and nonrejecting cardiac transplants. A comparative clinical study of thallium-201, technetium-99m, and gallium-67

To study the scintigraphic detectability of cardiac rejection, we performed 135 planar myocardial scans ([99mTc]pyrophosphate, 85; 201Tl, 36; 67Ga, 14) together with endomyocardial biopsies in ten patients for a (mean) 17-mo postoperative period. Specificity of each agent exceeded 89%. Technetium-99m pyrophosphate showed results that significantly correlated with the severity of rejection (p = 0.03), as shown by biopsy, but neither 201Tl nor 67Ga did so (p = 0.63 and 0.81, respectively). Technetium-99m pyrophosphate showed better diagnostic accuracy (85%) than 201Tl (69%) and 67Ga (64%). Technetium-99m pyrophosphate also showed higher negative predictive value (91%) than thallium (76%) and gallium (69%). Thus, a normal 99mTc pyrophosphate scan was usually associated with absence of cardiac rejection. However, all three agents showed unacceptably poor sensitivity (0% to 30%) and thus were not useful as a screening test for cardiac rejection, even when the same agent was used serially in imaging a given patient.     

Characteristics of iodine-123 IQ-SPECT/CT imaging compared with conventional SPECT/CT

Annals of Nuclear Medicine - Although the utility of IQ-SPECT imaging using 99mTc and 201Tl myocardial perfusion SPECT has been reported, 123I-labeled myocardial SPECT has not been fully evaluated....     

Segmental analysis of SPECT 99mTc-methoxy isobutyl isonitrile and 201Tl myocardial imaging in ischaemic heart disease

To study the potential usefulness of 99mTc-methoxy isobutyl isonitrile (99mTc-MIBI) as a substitute for 201Tl in assessing patients with ischaemic heart disease, 24 patients underwent 1 day rest and exercise 99mTc-MIBI single photon emission computerised tomography (SPECT) 1 week after SPECT exercise 201Tl. All patients were catheterized within 1 month after myocardial imaging. In 17 patients, resting first pass radionuclide angiography (FPRNA) was performed with 99mTc-MIBI. The heart to lung ratio for 99mTc-MIBI and 201Tl was calculated both at rest and exercise. The segmental analysis for myocardial perfusion reveals that 87/96 segments (91%) were correctly classified by SPECT 201Tl and 84/96 segments (88%) were correctly classified by 99mTc-MIBI. A significant correlation was present between LVEF measured by 99mTc-MIBI FPRNA and contrast ventriculography (r = 0.85, P less than 0.0001). The heart to lung ratio both at rest and exercise for 99mTc-MIBI is significantly higher than 201Tl (P less than 0.01 and less than 0.001 respectively). We conclude that 99mTc-MIBI is a promising agent for simultaneous evaluation of myocardial perfusion and cardiac function.     

Extraosseous accumulation of 99mTc phosphonate complexes in primary brain tumor evaluated with SPECT

Although extraosseous accumulations of 99mTc phosphate complexes are phenomena which can often be seen, no case showing extraosseous accumulation to brain tumor on SPECT has been reported. We report here two cases of primary brain tumor showing extraosseous accumulation of 99mTc phosphate in bone SPECT. 201Tl SPECT also showed increased 201Tl uptake by the tumor. Comparing bone SPECT with 201Tl SPECT, the regions of abnormality of both SPECTs were very similar in the case of glioblastoma, but in the case of malignant lymphoma the region showing intense uptake of 99mTc-MDP was smaller than that on 201Tl SPECT. It was revealed that bone SPECT is more useful in the assessment of extraosseous accumulation to a primary brain tumor than conventional bone scintigraphy.     

Comparison of 99mTc-hexakis 2-methoxy-2-isobutyl isonitrile and 201Tl SPECT imaging for evaluation of coronary artery disease

To evaluate clinical value of 99mTc-hexakis 2-methoxy-2-isobutyl isonitrile (MIBI) imaging for assessing coronary artery disease (CAD), 99mTc-MIBI SPECT imaging at post-exercise and at rest was compared with 201Tl SPECT imaging at post-exercise and 3 hours redistribution in 27 patients suspected with CAD. The sensitivities for detecting CAD patients were 94% (17/18) by both studies. The specificities were 71% (5/7) by 99mTc-MIBI and 57% (4/7) by 201Tl (p = NS). The sensitivities for detecting stenosed coronary arteries (greater than or equal to 75% stenosis) were also similar between 99mTc-MIBI (78%) and 201Tl (74%) (p = NS). The similar specificity values were obtained by 99mTc-MIBI (84%) and by 201Tl (82%) (p = NS). The patterns of abnormality (normal, ischemia and scar) were similar between 99mTc-MIBI and 201Tl images in 22 of the 25 cases (88%) and 117 of the 125 segments (94%). However, these patterns were occasionally different particularly in patients who received PTCA or CABG. Thus, 99mTc-MIBI SPECT imaging seems to be as accurate as 201Tl SPECT imaging for the detecting and evaluating CAD.     

Quantitative assessment of the infarct size with the unfolded map method of 201Tl myocardial SPECT in patient with acute myocardial infarction]

The unfolded map method of 201Tl single photon emission computed tomography (SPECT) was evaluated as to the ability to quantify and the clinical reliability in estimation of infarct size. At first, the following results were obtained in basic experiments using thoracic phantom: 1) the defect area estimated by the unfolded map method was well correlated with the real defect area in spite of overestimation of the defect area, when the defect area was determined by an isocount method (below 80% of maximum count) (y = 1.941 + 2.29x, r = 0.971, p less than 0.001); 2) the defect volume estimated by short-axis images of 201Tl SPECT was closely correlated with real defect volume in spite of overestimation of defect volume (y = 0.762 + 2.156x, r = 0.982, p less than 0.001); 3) when the defect area was estimated by division of the defect volume by the mean myocardial compartment thickness, it was closely correlated with real defect area (y = 0.946 + 1.232x, r = 0.990, p less than 0.001); 4) when the volume was calculated from the summation of voxels in the regions districted by isocount threshold level at each section of the 99mTc SPECT, the optimal isocount threshold level (percentage to maximum count) was 55%. In addition, the clinical reliability of the unfolded map method as infarct sizing was evaluated in 26 patients with acute myocardial infarction by comparing it with enzymatic method, Bull's eye method, and 99mTc pyrophosphate (PYP) SPECT method. In 14 first attack cases of patient without right ventricular infarction, infarct area (IA) of the unfolded map method correlated most closely with the accumulated creatine kinase MB isoenzyme release (CK-MBr) (r = 0.897), compared with the extent score (ES) (r = 0.853) and the severity score (SS) (r = 0.871) of Bull's eye method and the infarct volume (IV) (r = 0.595) of 99mTc PYP SPECT. In conclusion, although the unfolded map method of 201Tl SPECT has the tendency which overestimate infarct size, it is accurate and clinically reliable method in estimating infarct size.     

Assessment of left ventricular function by 201Tl ECG-gated myocardial SPECT]

We applied the QGS program for LV function analysis (described by Germano, 1995) to a 201Tl SPECT study at rest, and estimated its accuracy. We performed 201Tl ECG-gated myocardial SPECT in 25 patients with ischemic heart disease under an acquisition time used in the routine 99mTc ECG-gated SPECT study. The quality of the gated images was visually assessed with a 4-point grading system. LVEDV, LVESV, LVEF determined by the QGS program were compared with those by Simpson's method on biplane LVG in 25 patients. Regional wall motion scores in 7 myocardial segments were assessed on the three-dimensional display created by the QGS program and the cine display of biplane LVG with a 5-point grading system. Wall motion scores obtained by the QGS program were compared with those by LVG. Although 72.0% of 201Tl ECG-gated SPECT images were fair or poor in image quality, there were good correlations between the values obtained by the QGS program and LVG (LVEDV: r = 0.82, LVESV: r = 0.88, LVEF: r = 0.89). In addition, wall motion scores by the QGS program were correspondent to those by LVG in 77.1% of all 175 myocardial segments. We conclude that the QGS program provides high accuracy in evaluating left ventricular function even from 201Tl ECG-gated myocardial SPECT data.     

Compartmental modeling of technetium-99m-labeled teboroxime with dynamic single-photon emission computed tomography: comparison with static thallium-201 in a canine model

Di Bella EVR, Ross SG, Kadrmas DJ, et al. Compartmental modeling of technetium-99m-labeled teboroxime with dynamic single-photon emission computed tomography: Comparison with static thallium-201 in a canine model. Invest Radiol 2001;36:178-185.RATIONALE AND OBJECTIVES: A compartmental modeling approach to deriving kinetic parameters from a time series of single-photon emission computed tomography (SPECT) images of technetium-99m-labeled (99mTc-) teboroxime may have value for semiquantitative assessment of myocardial perfusion. This study investigated the value of the kinetic parameters derived from a two-compartment model of 99mTc-teboroxime for measuring myocardial perfusion and compared it with static thallium-201 (201Tl) uptake and microsphere-measured blood flow in dogs. METHODS: Experiments were successfully conducted in 9 of 11 open-chest dogs. During adenosine stress, a single complete set of projections of 201Tl uptake was acquired. 99mTc-teboroxime was then injected during adenosine stress, and a complete set of projections was acquired every 5.7 seconds for 17 minutes. Resting studies were performed on 4 of the animals. All of the projection sets were reconstructed with an iterative algorithm and incorporated corrections for attenuation and the geometric response of the collimators. Regional kinetic parameters (washin and washout) were determined semiautomatically from the time series of reconstructed 99mTc-teboroxime images and registered with microsphere data. Regional washin estimates were compared with 201Tl intensities and myocardial blood flows determined from microspheres. RESULTS: Optimally scaled 99mTc-teboroxime washin parameters and 201Tl uptakes were correlated with microsphere-determined blood flows (r = 0.91, y = 0. 99x + 0.01, and r = 0.92, y = 0.88x + 0.28, respectively). In six of the studies, the left anterior descending coronary artery was occluded, and stress occluded-to-normal (O/N) ratios were calculated. The O/N ratios were 0.32 +/- 0.17 as determined from microspheres injected with 201Tl and 0.38 +/- 0.29 from microspheres injected with 99mTc-teboroxime (P = NS). The O/N ratios were 0.48 +/- 0.16 for static 201Tl uptake and 0.27 +/- 0.21 for 99mTc-teboroxime washin (P < 0.05). CONCLUSIONS: Both 201Tl uptake and 99mTc-teboroxime kinetic parameters were well correlated with flow. The 99mTc-teboroxime washin parameters offer semiquantitative flow values and provide greater defect contrast than can be obtained with 201Tl uptake values.     

99mTc-HL91 is inferior to 201Tl in scintigraphic detection of chronic myocardial ischaemia

AIM: 99mTc-HL91 is a new hypoxia agent and can identify acutely ischaemic viable myocardium in a canine model using a standard gamma camera. The purpose of the study was to determine whether this tracer could be used to detect regional ischaemia in chronic ischaemic myocardium in a swine model. METHOD: Using a porcine model of chronic myocardial ischaemia, five mini-pigs with proximal left anterior descending artery (LAD) stenoses were studied. Injection of 462.5 MBq (12.5 mCi) 99mTc-HL91 was followed by imaging over 2 h. Coronary angiography and dipyridamole stress-re-injection 201Tl single photon emission computed tomography (SPECT) were performed within 1 day of each other. RESULTS: None of the five pigs demonstrated positive hot 99mTc-HL91 uptake throughout the 2 h imaging, whereas four of the five animals showed significant myocardial ischaemia on 201Tl SPECT. The region of interest analysis of LAD/left circumflex artery count ratios at 1 and 2 h demonstrated similar 99mTc-HL91 uptake and retention in chronic ischaemic as well as non-ischaemic myocardium. CONCLUSION: 99mTc-HL91 is inferior to 201Tl in scintigraphic detection of chronic myocardial ischaemia.     

Technetium 99m sestamibi in the assessment of chronic coronary artery disease.

Extensive work has already been performed with regard to both planar and single photon emission computed (SPECT) technetium 99m sestamibi studies. Before widespread application of optimized acquisition and processing methods, clinical results between 99mTc sestamibi and thallium 201 were remarkably similar. It is anticipated that as techniques for 99mTc sestamibi planar and SPECT imaging become optimized, improvements in sensitivity and specificity for detection of coronary artery disease, over those observed with 201TI, might be forthcoming. This expectation is based on the improved image quality inherent in the use of the 99mTc agent with its higher count rate and higher energy. This improvement in image quality may be a principal reason for laboratories to switch from 201TI to 99mTc sestamibi imaging. It is anticipated that, with improved imaging characteristics, it will be easier for the average community hospital to obtain higher quality planar or SPECT imaging using 99mTc sestamibi rather than 201TI. In addition to improved image quality, the characteristics of 99mTc sestamibi allow gated planar or SPECT perfusion images to be obtained. It has been suggested that stress-gated SPECT sestamibi studies may provide all the information contained in a stress-rest nongated 99mTc sestamibi study, thereby potentially increasing patient throughput, a major concern with SPECT. Throughput can also be increased by using dual-isotope approaches with rest 201TI and stress technetium sestamibi acquisitions, employing either separate or simultaneous imaging with which the entire study can be accomplished in less than 2 hours. With simultaneous dual-isotope acquisition, camera time can be reduced by 50%. Finally, 99mTc sestamibi offers the advantage of the ability to perform first-pass exercise ventricular function and SPECT myocardial perfusion studies with a single injection of tracer. Regarding the assessment of myocardial viability, results to date suggest a very high degree of concordance between 201TI and 99mTc sestamibi studies using either planar or SPECT acquisition techniques. Correlative rest studies with both tracers will be of particular interest, as will preoperative and postoperative and position emission tomography correlation studies.