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H Kiat

Publications and source records attributed to H Kiat.

At least 37 records · Page 2Linked to original sources
PubMed1995

Arbutamine stress thallium-201 single-photon emission computed tomography using a computerized closed-loop delivery system. Multicenter trial for evaluation of safety and diagnostic accuracy. The International Arbutamine Study Group.

OBJECTIVES: This study sought to evaluate the efficacy and safety of arbutamine when used in conjunction with thallium-201 single-photon emission computed tomography (SPECT) in a multicenter trial and to compare arbutamine stress and treadmill exercise thallium-201 SPECT for diagnostic sensitivity and myocardial perfusion pattern. BACKGROUND: Arbutamine is a potent beta-agonist developed specifically for pharmacologic stress testing. METHODS: Arbutamine was administered by a novel computerized closed-loop device that measures heart rate and adjusts arbutamine infusion to achieve a selected rate of heart rate increase toward a predetermined limit. The cohort included 184 patients who underwent arbutamine stress testing, of whom 122 (catheterization group) had angiographically defined coronary artery disease ( > or = 50% diameter stenosis of a major coronary artery), and 62 had a low pretest likelihood of coronary artery disease (low likelihood group). A subset of 69 patients from the catheterization group underwent both arbutamine and exercise stress testing. RESULTS: Hemodynamic responses during arbutamine and exercise stress testing demonstrated no significant difference in percent increase in heart rate (81% vs. 76%) or systolic blood pressure (26% vs. 30%). The sensitivity for detecting coronary artery disease ( > or = 50% stenosis) using arbutamine thallium-201 SPECT was 87% (95% for detecting > or = 70% stenoses), and the normalcy rate in the low likelihood group was 90%. In patients completing both arbutamine and exercise stress testing, thallium-201 SPECT sensitivity for detecting coronary artery disease ( > or = 50% stenosis) was 94% and 97% (p = NS), respectively Furthermore, SPECT segmental visual score agreement (defect vs. no defect) showed a concordance of 92% between arbutamine and exercise results (kappa 0.80, p < 0.001). The stress thallium-201 SPECT segmental scores showed 83% exact agreement (kappa 0.69, p < 0.001), and analysis of the reversibility of segments with stress perfusion defects demonstrated 86% exact agreement (kappa 0.68, p < 0.001). In general, side effects associated with arbutamine were well tolerated and resolved with discontinuation of infusion. CONCLUSIONS: Arbutamine, administered by a closed-loop feed-back system was shown to be a safe and effective pharmacologic stress agent. Arbutamine stress thallium-201 SPECT appears to be accurate for the diagnosis of coronary artery disease with a diagnostic efficacy similar to that of treadmill exercise thallium-201 studies.

Adult↗
PubMed1995

Clinical applications of exercise nuclear cardiology studies in the era of healthcare reform.

The challenge for nuclear cardiology is to demonstrate that it can provide more information than competitive modalities at comparable or lower cost. In considering patients for nuclear cardiology procedures, presentations can be divided into 9 subsets: within each subset, nuclear cardiology tests should be employed where incremental information is provided over the information available without performing the test. (1) Patients with no known coronary artery disease (CAD); for diagnosis, nuclear imaging is useful in patients with intermediate probability of CAD. For prognosis, assessment is based on extent of ischemia, where we have shown that nuclear testing provides incremental information, especially in patients with a high likelihood of CAD, such as those with typical angina. In the remaining categories (2-9), nuclear cardiology studies are predominantly used for purposes of risk stratification. Here the greatest value is in patients deemed to be at intermediate risk before nuclear testing. (2) Postmyocardial infarction: stress nuclear imaging provides an alternative to angiography for risk assessment of clinically uncomplicated patients. (3) Poor ventricular function: Nuclear testing is particularly useful for differentiating patients with hibernating myocardium (the defect is reversible), with stunned myocardium (no defect is present), or with myocardial infarction (the defect is persistent). (4) Unstable angina: Following current federal guidelines, nuclear imaging in medically stabilized low-to-intermediate risk patients with unstable angina is likely to increase. (5) Postcatheterization patients: Nuclear imaging is useful when there is uncertainty regarding the choice of medical management or revascularization. (6) Pre-noncardiac surgery patients: Nuclear imaging is clearly helpful in patients with intermediate clinical risk and may provide useful information in clinically high-risk patients. (7) Post-PTCA patients: Due to the intermediate likelihood of restenosis, nuclear scans are frequently employed 2-6 months following intervention. (8) Post-CABG patients: We have demonstrated that exercise scintigraphy (SPECT) provides incremental prognostic information over clinical and exercise electrocardiographic results and is useful when clinical risk of events is considered intermediate. (9) Long-term management: Scintigraphy provides objective information regarding progression or regression of CAD.

Angina, Unstable↗
PubMed1995

Adenosine pharmacologic stress myocardial perfusion tomographic imaging in patients with significant aortic stenosis. Diagnostic efficacy and comparison of clinical, hemodynamic and electrocardiographic variables with 100 age-matched control subjects.

OBJECTIVES: This study assessed the safety and diagnostic accuracy of adenosine stress myocardial perfusion scintigraphy for the detection of coronary artery disease using single-photon emission computed tomography (SPECT) in patients with significant aortic stenosis. BACKGROUND: Exercise cardiac stress testing in patients with significant aortic stenosis is generally avoided because of concerns for safety. In addition, those studies that have analyzed the utility of exercise testing both with and without myocardial thallium-201 scintigraphy for the diagnosis of coronary artery disease have yielded low specificity. Currently, no safe and accurate means exists to noninvasively assess the presence, extent and severity of coronary artery disease in patients with significant aortic stenosis. METHODS: The study included 35 patients with moderate to severe aortic stenosis (mean [+/- SD] aortic valve area 0.84 +/- 0.16 cm2, range 0.5 to 1.2; mean maximal instantaneous aortic valve gradient 44.4 +/- 15.9 mm Hg, range 20 to 84). All patients underwent a 6-min adenosine infusion (140 micrograms/kg body weight per min) protocol and either separate acquisition rest thallium-201/stress technetium-99m sestamibi or stress and 4-h redistribution thallium-201 SPECT: Visual 20-segment SPECT analysis used a standard five-point scoring system from 0 (normal tracer uptake) to 4 (absent uptake). The SPECT results were considered abnormal if more than two segments had a stress score > or = 2. Hemodynamic, electrocardiographic and clinical responses were compared with those in a reference group of 100 consecutive age-matched patients undergoing adenosine SPECT who did not have aortic stenosis. RESULTS: Hemodynamic responses during adenosine stress testing between the study and control patients demonstrated no significant difference in the net change in systolic blood pressure (18% of baseline vs. 14%, patients with aortic stenosis vs. control subjects), heart rate (21% vs. 19%), rate-pressure product (0% vs. 2%) or incidence of chest pain (23% vs. 35%) or transient second-(9% vs. 9%) or third-degree atrioventricular block (3% vs. 1%). In the 20 patients who had coronary angiography, sensitivity for detection of coronary artery disease was 92% (12 of 13) and specificity was 71% (5 of 7). CONCLUSIONS: In this preliminary study, adenosine was found to be well tolerated and diagnostically accurate in patients with moderate to severe aortic stenosis.

Adenosine↗
PubMed1995

Incremental prognostic value of exercise thallium-201 myocardial single-photon emission computed tomography late after coronary artery bypass surgery.

OBJECTIVES: This study assessed the incremental prognostic value of exercise thallium-201 myocardial perfusion single-photon emission computed tomography (SPECT) performed > or = 5 years after coronary artery bypass surgery. BACKGROUND: Thallium-201 scintigraphy has shown significant prognostic value in a variety of populations with suspected and known coronary artery disease. However, its value in patients with previous bypass surgery remains unknown. METHODS: We studied 294 patients who were prospectively followed up. Cox proportional hazards models for prediction of "hard" events (cardiac death and nonfatal infarctions) were constructed, with variables considered for inclusion in hierarchic order: clinical and exercise data first, followed by scintigraphic information. RESULTS: Mean (+/- SD) follow-up duration after scintigraphy was 31 +/- 11 months. There were 20 cardiac deaths and 21 nonfatal acute myocardial infarctions. Twenty-nine patients had late (> 60 days after thallium-201 SPECT) revascularization procedures or underwent repeat bypass surgery or percutaneous transluminal angioplasty. Shortness of breath and peak exercise heart rate were the most important clinical predictors of hard events. Two scintigraphic variables added significant prognostic information to the clinical model: the thallium-201 summed reversibility score (summation of segmental differences between stress and redistribution scores) and the presence of increased lung uptake of the radiotracer. The global chi-square statistic for this model was twice as high as that for the clinical/exercise model alone (49.7 vs. 24.2). When a second multivariate Cox model was built adding "soft" events (i.e., late revascularization procedures) as outcomes of interest, the summed reversibility score was selected as an independent scintigraphic predictor of events. The global chi-square statistic for this model was 50.7, three times as high as that for the clinical/exercise model alone. CONCLUSIONS: After evaluation of treadmill and exercise data, thallium-201 myocardial perfusion SPECT provided incremental prognostic information in patients late after bypass.

Aged↗
PubMed1995

Incremental value of simultaneous assessment of myocardial function and perfusion with technetium-99m sestamibi for prediction of extent of coronary artery disease.

OBJECTIVES: This study assessed the incremental value of technetium-99m myocardial single-photon emission computed tomography (SPECT) and simultaneous first-pass radionuclide angiography, when added to treadmill exercise, for prediction of the extent of coronary artery disease. BACKGROUND: Technetium-99m count statistics permit the simultaneous assessment of myocardial perfusion and function. However, whether this characteristic improves prediction of the extent of coronary artery disease remains unknown. METHODS: We studied 70 consecutive patients who had coronary angiography within 6 months of the scintigraphic study. All patients underwent a symptom-limited treadmill exercise test. Treadmill data were summarized using a previously validated score. Left ventricular ejection fraction and regional wall motion were evaluated from a first-pass radionuclide angiogram acquired at peak treadmill exercise in the anterior view. Perfusion was assessed visually. Extent of angiographic disease was expressed as the presence or absence of multivessel disease (more than two coronary artery territories with > 50% stenosis) and as a score that reflects the location of severe (> 75%) stenosis. RESULTS: Stepwise addition of scintigraphic data (perfusion first, followed by function) to the treadmill score showed significant incremental value for prediction of the angiographic score at each step; exercise ejection fraction alone was the strongest independent predictor. Discriminant accuracy for detection of multivessel disease was also improved by the addition of perfusion information to the treadmill score and addition of regional wall motion analysis to both of them. In this case, ejection fraction failed to show independent value. CONCLUSIONS: The addition of simultaneously performed sestamibi perfusion SPECT and first-pass radionuclide angiography to the treadmill exercise test significantly improved prediction of the extent of coronary artery disease.

Coronary Angiography↗
PubMed1995

Incremental value of prognostic testing in patients with known or suspected ischemic heart disease: a basis for optimal utilization of exercise technetium-99m sestamibi myocardial perfusion single-photon emission computed tomography.

OBJECTIVES: This study assessed the incremental prognostic implications of normal and equivocal exercise technetium-99m (Tc-99m) sestamibi single-photon emission computed tomography (SPECT) and sought to determine its incremental prognostic value, impact on patient management and cost implications. BACKGROUND: The prognostic implications of Tc-99m sestamibi SPECT are not well defined, and risk stratification using this test has not been explored. METHODS: We studied 1,702 patients referred for exercise Tc-99m sestamibi SPECT who were followed up for a mean (+/- SD) of 20 +/- 5 months. Patients with previous percutaneous transluminal coronary angioplasty or coronary artery bypass surgery were excluded. The SPECT studies were assessed using semiquantitative visual analysis. Cardiac death and myocardial infarction were considered "hard" events, and coronary angioplasty and bypass surgery > 60 days after testing were considered "soft" events. RESULTS: Of the 1,702 patients studied, 1,131 had normal or equivocal scan results. A total of 10 events occurred in this group (1 cardiac death and 1 myocardial infarction [0.2% hard events]; 4 coronary angioplasty and 4 bypass surgery procedures [0.7% soft events]). The rates of hard events and referral to catheterization after SPECT were similarly low in patients with a low (< 0.15), intermediate (0.15 to 0.85) and high (> 0.85) post-exercise treadmill test (ETT) likelihood of coronary artery disease. With respect to scan type, patients with normal, probably normal or equivocal scan results had similarly low hard event rates. In the 571 patients with abnormal scan results, there were 43 hard events (7.5%) and 42 soft events (7.4%) (p < 0.001 vs. 1,131 patients with normal scan results for both). When the complete spectrum of scan responses was considered, SPECT provided incremental prognostic value in all patient subgroups analyzed. However, the nuclear scan was cost-effective only in patients with interpretable exercise ECG responses and an intermediate to high post-ETT likelihood of coronary artery disease and in those with uninterpretable exercise ECG responses and an intermediate to high pre-ETT likelihood of coronary artery disease. CONCLUSIONS: Normal or equivocal exercise Tc-99m sestamibi study results are associated with a benign prognosis, even in patients with a high likelihood of coronary artery disease. Although incremental prognostic value is added by nuclear testing in all patient subgroups, a testing strategy incorporating nuclear testing proved to be cost-effective only in the groups with an intermediate to high likelihood of coronary artery disease before scanning.

Aged↗
PubMed1995

Operator-less processing of myocardial perfusion SPECT studies.

UNLABELLED: We have developed a completely automated algorithm to generate reoriented tomographic images from projections in myocardial perfusion SPECT. METHODS: The algorithm consists of three software modules. The first module determines reconstruction limits for the projection dataset using two-dimensional feature extraction techniques. The second module reconstructs the projection images into transaxial images using standard filtered backprojection. The third module reorients the transaxial images into short-axis images. RESULTS: The algorithm was validated on 350 rest 201Tl and 350 stress 99mTc-sestamibi studies acquired on a single-detector (178 studies), a 90 degrees dual-detector (230 studies) or a triple-detector camera (292 studies). The complete processing sequence was successful in 93.6% of the studies (166/178 + 216/230 + 273/292). As for the individual modules, myocardial boundaries were correctly determined in 96.3% of the studies (171/178 + 222/230 + 281/292), while reorientation was successful in 97.2% of the studies (166/171 + 216/222 + 273/281). No significant difference in success rates for 201Tl versus 99mTc-sestamibi images was found. CONCLUSION: Our automated approach to myocardial perfusion SPECT processing is highly successful, intrinsically reproducible and can produce time and cost savings while improving accuracy in a clinical or research environment.

Algorithms↗
PubMed1995

Automatic quantification of ejection fraction from gated myocardial perfusion SPECT.

UNLABELLED: We have developed a completely automatic algorithm to quantitatively measure left ventricular ejection fraction (LVEF) from gated 99mTc-sestamibi myocardial perfusion SPECT images. METHODS: The algorithm operates in the three-dimensional space and uses gated short-axis image volumes. It segments the left ventricle (LV), estimates and displays endocardial and epicardial surfaces for all gating intervals in the cardiac cycle, calculates the relative left ventricular cavity volumes and derives the global EF from the end-diastolic and end-systolic volume, all without operator interaction. The algorithm for measuring LVEF was tested in 65 clinical patients undergoing 16-interval and 8-interval rest-gated SPECT and validated against first-pass radionuclide ventriculography. RESULTS: Automatic segmentation and contouring of the LV was successful in 65/65 (100%) of the studies. Agreement between EFs measured from 8-interval gated SPECT and EFs calculated from first-pass data was high (y = 2.44 + 1.03x, r = 0.909, p < 0.001, s.e.e. = 6.87). Agreement between EF values measured from 16-interval and 8-interval gated SPECT was excellent (y = -2.7 + 0.97x, r = 0.988, p < 0.001, s.e.e. = 2.65), the latter being on average lower by 3.71 percentage points. CONCLUSION: Our automatic method is rapid and highly agrees with conventional radionuclide measurements of EF, thus providing clinically useful additional information to complement myocardial perfusion studies.

Algorithms↗
PubMed1995

Automatic reorientation of three-dimensional, transaxial myocardial perfusion SPECT images.

UNLABELLED: We developed a completely automatic technique to reorient transaxial images into short-axis (oblique) myocardial perfusion SPECT images. METHODS: The algorithm starts by isolating (segmenting) the left ventricle (LV) myocardium using a combination of iterative clusterification and rule-based location/size/shape criteria. The three-dimensional, mid-myocardial LV surface is initially estimated as the locus of the trilinearly interpolated maxima for the count profiles originating from the center of mass of the segmented LV. The final mid-myocardial surface is obtained by iteratively applying this process, incorporating additional constraints of shape and texture and using the nonsegmented, nonthresholded transaxial image to obtain information on hypoperfused areas of the myocardium. It is then fitted to an ellipsoid, of which the major axis is assumed to represent the long axis of the LV, and the three-dimensional image volume is resliced perpendicularly to it. RESULTS: The algorithm was retrospectively applied to 400 dual-isotope studies (200 rest 201TI, 200 stress 99mTc-sestamibi) from 200 consecutive patients. Segmentation was successful in 394/400 (98.5%) of the patients. The reproducibility of computer-based reorientation was perfect and significantly better than either intraobserver or interobserver reproducibility. CONCLUSION: Automatic reorientation offers the potential for consistently faster and more accurate image processing and analysis and is an important step towards totally operator-less management of myocardial perfusion SPECT data.

Algorithms↗
PubMed1994

Pharmacologic stress dual-isotope myocardial perfusion single-photon emission computed tomography.

Separate-acquisition rest thallium-201/exercise technetium-99m sestamibi (sestamibi) dual-isotope single-photon emission computed tomography (SPECT) has been shown to be effective for assessment of myocardial perfusion and viability. The present study was designed to validate the dual-isotope approach when used in conjunction with pharmacologic stress. All patients had rest 201TI SPECT followed immediately by adenosine (n = 82) or dipyridamole (n = 50) infusion and sestamibi injection. Sestamibi SPECT was performed 1 hour later. The entire study lasted < 2.5 hours. The patient population was categorized into three groups: 51 consecutive patients with coronary angiography and no previous myocardial infarction (group I), 58 consecutive patients with a low prescintigraphic test likelihood of coronary artery disease (group II), and 23 consecutive catheterized patients with remote Q-wave myocardial infarction (group III). For group I patients, the sensitivity and specificity for dual-isotope SPECT were 92% (35 of 38) and 85% (11 of 13), respectively, when > or = 50% coronary artery narrowing was considered significant and were 97% (34 of 35) and 81% (13 of 16) respectively, when > or = 70% narrowing was considered significant. The normalcy rate among the 58 patients of group II was 96%. Comparisons for pattern of stress-defect reversibility demonstrated that of the 97 stress defects within the infarct zones (group III), 15% were reversible and 85% were nonreversible. In contrast, of the 227 stress defects within the diseased (> or = 50% stenosis) vessel zones of the group I patients, 93% were reversible and 7% were noreversible (p < 0.001 vs group III). In conclusion, separate acquisition rest 201-TI/pharmacologic stress sestamibi dual-isotope SPECT is an efficient myocardial perfusion imaging protocol with high accuracy for detection and assessment of angiographically significant coronary artery disease.

Adenosine↗
PubMed1994

Gated technetium-99m sestamibi for simultaneous assessment of stress myocardial perfusion, postexercise regional ventricular function and myocardial viability. Correlation with echocardiography and rest thallium-201 scintigraphy.

OBJECTIVES: This study compares technetium-99m sestamibi (sestamibi) electrocardiographic (ECG) gated single-photon emission computed tomography (gated SPECT) and echocardiography for the evaluation of myocardial function and assesses the feasibility of single-injection, single-acquisition stress perfusion/rest function technetium-99m sestamibi-gated SPECT as an alternative to conventional stress/rest imaging for assessment of myocardial perfusion and viability. BACKGROUND: Simultaneous assessment of stress perfusion and rest function is possible with gated SPECT acquisition of stress-injected technetium-99m sestamibi. METHODS: Rest thallium-201 SPECT followed by stress sestamibi-gated SPECT (acquired 0.5 to 1 h after sestamibi injection) was performed in 58 patients. Echocardiography was performed immediately after or before gated SPECT in 43 of the patients. All studies were analyzed by semiquantitative visual scoring. Sestamibi-gated SPECT studies were read for stress perfusion and rest wall motion and thickening. Reversibility on sestamibi-gated SPECT was defined as the presence of a definite stress defect with normal or mildly impaired wall motion or thickening on gated SPECT: RESULTS: There was high segmental score agreement between gated SPECT and echocardiography for wall motion (91%, kappa = 0.68, p < 0.001) and thickening (90%, kappa = 0.62, p < 0.001). Correlation for global wall motion (r = 0.98, p < 0.001) and thickening (r = 0.96, p < 0.001) scores between the two modalities was excellent. In 32 patients without previous myocardial infarction, there was excellent agreement for reversibility between stress sestamibi-gated SPECT and rest thallium-201/stress sestamibi (98%, kappa = 0.93, p < 0.01). However, in 26 patients with previous infarction, discordance between the two approaches was frequent, with 26% (20 of 78) of nonreversible defects by stress sestamibi-gated SPECT being reversible by rest thallium-201/stress sestamibi and 21% (23 of 112) of reversible defects by stress sestamibi-gated SPECT being nonreversible by rest thallium-201/stress sestamibi. CONCLUSIONS: Gated SPECT of stress-injected sestamibi correlates well with echocardiographic assessment of regional function and thus adds information to perfusion SPECT: In patients without previous myocardial infarction, a single-injection stress perfusion/rest function approach using sestamibi-gated SPECT can substitute for conventional stress/rest myocardial perfusion imaging, adding a rest perfusion study only if there are nonreversible defects or consideration of attenuation artifacts. In patients with previous myocardial infarction, the gated SPECT approach does not replace the need for a rest perfusion study.

Aged↗
PubMed1994

Temporal image fractionation: rejection of motion artifacts in myocardial SPECT.

METHODS: We have developed a protocol, termed "temporal image fractionation," in which static myocardial perfusion SPECT studies are acquired as three-interval dynamic studies (three temporal frames, each consisting of a full projection set), utilizing continuous alternating detector rotation and a multi-detector camera. The frames are individually examined for motion by cine display, then summed together into a static SPECT file which is reconstructed with standard procedure. This approach offers three potential advantages in reducing or eliminating image artifacts resulting from patient or organ motion: (1) If severe motion occurs in one frame, only the remaining two are summed and reconstructed (motion-purging); (2) Alternating detector rotation reduces artifacts from mono-directional, drifting motion during acquisition (i.e., upward creep of the heart); and (3) Generally, with multiple rotations, motion is spread over a larger angular range and therefore has a lesser effect of the final reconstructed images. RESULTS: These advantages are demonstrated and quantified in this paper using clinical data (A) and simulated motion on phantom data (B and C). In the phantom experiments, fractionated images were found to be 48.9%, 35.8% and 35.9% "more similar" to the original images than nonfractionated images for simulated 1.67-cm upward creep, 1.1-cm nonreturning axial motion and 1.65-cm lateral motion, respectively. CONCLUSION: This protocol requires little extra processing and no final extra data storage compared to standard acquisition, and it has nearly eliminated instances in which a study had to be repeated due to patient motion. Step-and-shoot acquisition is not recommended in conjunction with this protocol, as it would lengthen the time necessary to obtain the same count statistics as in nonfractionated acquisition.

Artifacts↗
PubMed1994

State-of-the-art myocardial perfusion imaging.

Technetium-99m sestamibi is a new agent that offers several theoretical advantages over Tl-201 for myocardial perfusion imaging. The results of current clinical trials utilizing acquisition and processing parameters similar to those of Tl-201 and a separate 2-day injection protocol suggest that Tc-99m sestamibi and T1-201 SPECT provide similar information with respect to the detection of myocardial perfusion defects, the assessment of the pattern of defect reversibility, the overall detection of CAD, and the detection of disease in individual coronary arteries. Tc-99m sestamibi SPECT appears to be superior to Tc-99m planar imaging because it provides a higher defect contrast and is more accurate for the detection of disease in individual coronary arteries. Significant research is underway to address optimization of acquisition and processing of Tc-99m sestamibi studies and the development of quantitative algorithms for detection and localization of CAD and sizing of transmural and nontransmural myocardial perfusion defects. It is expected that with the implementation of the final results of these new developments, further significant improvement in image quality will be attained, which, in turn, will increase the confidence of image interpretation. The development of algorithms for analysis of diastolic myocardial images may allow better evaluation of small and nontransmural myocardial defects. Furthermore, gated studies may provide valuable information with respect to regional myocardial wall motion, wall thickening, and artifact identification. Simultaneous assessment of ventricular function by performing first-pass studies may provide important information additional to that obtained from analysis of myocardial perfusion, especially in relation to the prognostic significance of different myocardial perfusion patterns. With the implementation of algorithms for attenuation and scatter correction, the overall specificity of Tc-99m sestamibi SPECT should improve significantly because of a substantial decrease in the instances of attenuation-related image artifacts.

Coronary Disease↗
PubMed1994

Dual-isotope myocardial perfusion SPECT with rest thallium-201 and stress Tc-99m sestamibi.

The commercial availability of Tc-99m-labeled myocardial perfusion agents had added choices in the noninvasive clinical assessment of coronary artery disease. Preferential use of Tc-99m sestamibi has been advocated principally due to improved image quality, which results from the combined physical and biological characteristics of this agent. This article reports upon the investigation of another approach for Tc-99m sestamibi SPECT--dual-isotope rest-stress myocardial perfusion SPECT, which takes advantage of the Anger camera's ability to collect date in different energy windows. For the dual-isotope approach, separate radiopharmaceuticals are employed for the rest injection and the stress injection.

Coronary Disease↗
PubMed1994

Comparative feasibility of separate or simultaneous rest thallium-201/stress technetium-99m-sestamibi dual-isotope myocardial perfusion SPECT.

UNLABELLED: Separate or simultaneous rest 201Tl/stress 99mTc-sestamibi dual-isotope SPECT are potentially efficient myocardial perfusion imaging protocols which combine the use of a high-resolution 99mTc tracer for stress perfusion assessment and 201Tl, the current single-photon agent of choice, for viability assessment. METHODS: To investigate the feasibility of dual-isotope myocardial perfusion SPECT protocols using rest 201Tl and stress sestamibi, 201Tl crosstalk into the 99mTc acquisition window (Group 1, n = 26 patients) and 99mTc crosstalk into 201Tl windows (Group 2, n = 25) were studied. For Group 1, treadmill exercise with sestamibi injection and poststress SPECT ("virgin" sestamibi images) were performed, followed by rest 201Tl injection and SPECT acquisition using dual-isotope windows (contaminated or "dual" images). For Group 2, the order was reversed: rest 201Tl SPECT (virgin 201Tl images) was performed first, followed by exercise sestamibi injection and dual-isotope SPECT. RESULTS: The contribution of 201Tl scatter to the dual sestamibi images (Group 1) was measured to be 2.9% +/- 2.1%, while 99mTc crosstalk contributed 26.7% +/- 13.0% to the dual 201Tl images (Group 2). Image quality was considered good to excellent in 92% of the sestamibi (virgin and dual) images and 88% of the virgin 201Tl SPECT, but only in 23% of the dual 201Tl studies. CONCLUSIONS: Technetium-99m crosstalk into 201Tl windows is substantial; therefore, simultaneous dual-isotope protocols, which involve assessment of 201Tl images contaminated by 99mTc, are not recommended. On the other hand, because of the small amount of 201Tl crosstalk into the 99mTc window, a separate acquisition dual-isotope approach employing the rest 201Tl (virgin)/stress sestamibi sequence is acceptable.

Aged↗
PubMed1994

Multicenter trial validation for quantitative analysis of same-day rest-stress technetium-99m-sestamibi myocardial tomograms.

UNLABELLED: The accuracy of an automated quantitative analysis of same-day rest/stress 99mTc sestamibi SPECT images for detection and localization of coronary artery disease (CAD) was assessed in a multicenter trial consisting of 161 patients from 7 different clinical sites utilizing various camera computer systems. METHODS: Of the 161 patients, 102 had angiographically documented coronary artery disease, 22 had normal coronary arteriograms, and 37 had a low (< 5%) likelihood of coronary artery disease based on their age, sex, symptoms and the results of their exercise electrocardiograms. The patients were studied using previously optimized image acquisition and processing protocols. An additional population consisting of 45 patients with single-vessel disease were evaluated to determine the optimal criteria for detection of CAD. RESULTS: The quantitative analysis method was associated with an overall sensitivity of 87%, specificity of 36%, and normalcy rate (true negative rate in the low likelihood patients) of 81%. Sensitivity for overall detection of disease was similar (90%) in patients with and without myocardial infarction (90% versus 89%). The sensitivities and specificities for identification of disease in individual coronary arteries were, respectively, 69% and 76% for LAD, 70% and 80% for LCX, and 77% and 85% for RCA. CONCLUSION: The results of this study demonstrate that the new objective quantitative method for analysis of same-day rest/stress 99mTc sestamibi SPECT images is accurate for detection and localization of CAD and correlates highly with expert visual interpretation.

Adolescent↗