Same day injections of Tc-99m methoxy isobutyl isonitrile (hexamibi) for myocardial tomographic imaging: comparison between rest-stress and stress-rest injection sequences

The Status of Stress Myocardial Perfusion Imaging Using 99mTc Pharmaceuticals in Japan: Results from a Nationwide Survey

Objective(s):

To appropriately use one-day myocardial perfusion imaging (MPI) with ^99mTc radiopharmaceuticals (i.e. to avoid shine-through artifacts), injection doses need to be optimized and dose ratios between the 1^st and 2^nd scans should be maintained at ≥ 3. However, the current state of practice in Japan is unclear. Thus, the aim of this study was to clarify the details of MPI protocols using ^99mTc radiopharmaceuticals in Japan.

Methods:

A nationwide survey was conducted in June and July 2016. Questionnaires about stress MPI protocols using ^99mTc radiopharmaceuticals were sent to 641 nuclear medicine facilities.

Results:

Responses were received from 246 facilities. One-day protocols were used in 97.1% of the facilities. The most common injection dose ratio was 2.5. Only 18.2% of facilities achieved the recommended injection dose ratio. Stress-only protocols were performed in only 1.7% of facilities; the primary reasons for not performing stress-only protocols were as follows: 1) “The reading-physician cannot interpret the image just after the first scan,” and 2) “Preparation of radiopharmaceuticals and scan arrangements turn out to be complicated.”

Conclusion:

Approximately 80% of nuclear medicine facilities do not follow the recommended injection dose ratio. Stress-only protocols are ideal, but are performed at very few facilities. Both optimization and standardization of stress MPI protocols using ^99mTc radiopharmaceuticals are needed in Japan.

Myocardial perfusion scintigraphy: techniques, interpretation, indications and reporting

Myocardial perfusion single photon emission-computed tomography (MPS) has been one of the most important and common non-invasive diagnostic cardiac test. Gated MPS provides simultaneous assessment of myocardial perfusion and function with only one study. With appropriate attention to the MPS techniques, appropriate clinical utilization and effective reporting, gated MPS will remain a useful diagnostic test for many years to come. The aim of this article is to review the basic techniques of MPS, a simplified systematic approach for study interpretation, current clinical indications and reporting. After reading this article the reader should develop an understanding of the techniques, interpretation, current clinical indications and reporting of MPS studies.

Women with high exercise tolerance and the role of myocardial perfusion imaging

BACKGROUND

Myocardial perfusion imaging (MPI) provides incremental diagnostic and prognostic information, even in patients with high exercise tolerance.

HYPOTHESIS

Myocardial perfusion imaging provides significant diagnostic value, specifically in women with high exercise tolerance.

METHODS

Our study population consisted of all women who underwent exercise MPI in our Department from January 1992 to June 1996 and reached at least Stage IV in the Bruce protocol. Patients were divided into those with known and those with possible coronary artery disease (CAD). All patients were followed for 3 years from the performance of MPI.

RESULTS

Of 4,803 women who underwent myocardial perfusion imaging, 3,183 had exercise stressing, and of those, 311 reached at least Stage IV in the Bruce protocol. Of these 311 MPI scans, only 23 (7.4%) were abnormal (reversible, fixed, or mixed) and the remaining 288 (92.6%) were normal. Of the 82 patients with known CAD, 13 (15.8%) had an abnormal MPI, while only 10 (4.4%) of the 229 patients with possible CAD. No myocardial infarction or cardiac death occurred within 3 years; one patient with normal MPI needed revascularization.

CONCLUSION

In women with high exercise tolerance, especially in those without already known CAD, the yield of MPI is very low. Women with high exercise tolerance have an excellent prognosis.

New protocol of myocardial SPECT imaging with technetium-99m sestamibi for reducing the time interval between rest and adenosine stress phases

We have developed a new protocol of myocardial perfusion-gated single-photon emission computed tomography (SPECT), by use of technetium-99m sestamibi (MIBI), in which SPECT imaging at rest followed by SPECT imaging after adenosine with low level ergometer stress can be conducted by use of the Monzen position within a shortened total testing time of 1 h or less. The study group consisted of 137 patients who underwent this new imaging protocol. The diagnostic quality of the images was as good as that of images obtained with the conventional method (30-60 min after the injection of MIBI). The SPECT image quality for the 137 patients was evaluated, and the percentages of images rated as excellent, good, fair, and poor were 65.3, 27.4, 5.8, and 1.5% for the rest image, and 68.2, 21.9, 8.4, and 1.5% for the stress image, respectively. The shortened total testing time reduced the physical and mental burden on the patient compared with that of conventional myocardial perfusion imaging. Because this technique allows us to perform rest and stress myocardial imaging within a short period, it is expected to be very useful in the clinical setting.

[Tomographic studies of myocardial perfusion normality with 99m Tc-Tetrofosmin. Spanish multicenter study]

This objective of this study was to obtain a pool of Myocardial Perfusion SPECTs with a 99mTetrofosmin stress/rest one day protocol in normal volunteers having a less than or equal to 5% likelihood of coronary artery disease that represents normalcy in the Spanish population. A total of 169 volunteers from 15 hospitals were studied. The volunteers were divided into 5 groups: Groups 1, 2 or 3 corresponding to men < 30 years (n = 33), men between 30 and 50 years (n = 32), or men > 50 years (n = 31); Groups 4 or 5: premenopausal (n = 38) or postmenopausal women (n = 35). A clinical history, physical examination, clinical laboratory parameters, echocardiography and a symptom limited exercise stress test were performed in all of them and had to be normal. The mean likelihood of coronary artery disease was 1.15 +/- 1.07%.Twenty-four segments were analyzed in each study and were classified into 5 grades of uptake (1 = normal, 2, 3, 4 = mild, moderate or severe defect and 5 = no uptake). Defects were then analyzed according to sex and location. Considering the stress and rest studies separately (8,112 segments), only 19 moderate and 75 mild defects were found, these corresponding to 16 volunteers, with more inferior defects in men and anterior defects in women. These data validate the normalcy of our population. A pool of Myocardial Perfusion SPECTs with a 99mTetrofosmin stress/rest one day protocol in normal volunteers that represents Spanish normal values was obtained.

Evaluation of cardiac function in myocardial infarction patients by ECG 99mTc-MIBI gated SPECT using a three-dimensional perfusion/motion map procedure

Three-dimensional (3D) radionuclear myocardial imaging has improved the evaluation of left ventricular wall motion. However, there have been no studies evaluating left ventricular function using 3D-perfusion/motion map techniques. We hypothesized that the 3D-perfusion/motion map could accurately evaluate left ventricular wall motion even in patients with a history of myocardial infarction. Electrocardiogram (ECG)-gated single photon emission computed tomography (SPECT) using 99mTc-methoxy isobutyl isonitrile (MIBI) was performed in 20 patients with a history of myocardial infarction who underwent left ventriculography. Myocardial imaging data were collected during ECG-gated SPECT using a 3-headed gamma camera. Reconstructed 3D SPECT images were oriented to correspond to standard left ventriculography views (right anterior oblique and left anterior oblique projections), and the shortening fraction (SF) was calculated using the center line method. The SF and left ventricular ejection fraction from 3D SPECT images were compared with those determined by left ventriculography. There was a significant correlation between left ventriculography and the 3D-perfusion/motion map procedure in determining SF for all regions of the left ventricle except the anterobasal and posterior segments by using the Bland and Altman method. The 3D-perfusion/motion map procedure offers the advantage that the influences of contraction-related myocardial torsion and three-dimensional compression are minimized. In addition, this method facilitates evaluation of images from nonstandard projections. We conclude that this method may be useful for evaluating left ventricular function.

Simultaneous assessment of myocardial perfusion and left ventricular function during transient coronary occlusion

OBJECTIVES

We used technetium-99m sestamibi imaging to evaluate the magnitude of changes in left ventricular function and perfusion and to investigate their interdependence during transient coronary occlusion.

BACKGROUND

Transient coronary occlusion during coronary angioplasty provides a unique opportunity for examining the effects of acute myocardial ischemia on left ventricular function and perfusion.

METHODS

Thirty-five patients with normal left ventricular function underwent first-pass radionuclide angiography with technetium-99m sestamibi using a multicrystal gamma camera during balloon occlusion of a coronary artery. Single-photon tomography was performed 2.1 +/- 1.7 h later. Subsequently, all scans were repeated at rest.

RESULTS

The mean size +/- SD of the perfusion defect during coronary occlusion was 23 +/- 18%, with significantly larger defects observed for occlusions of the left anterior descending coronary artery (39 +/- 20%) than for occlusions of the left circumflex (15 +/- 11%) or right (15 +/- 9%) coronary artery (p < 0.05). The mean change in ejection fraction from recovery to occlusion was -17 +/- 17% and was significantly larger for left anterior descending (-26 +/- 21%) and left circumflex (-15 +/- 11%) than for right (-8 +/- 10%) coronary artery occlusions (p < 0.05). For the entire group, ejection fraction during occlusion correlated significantly with perfusion defect size (r = 0.63, p = 0.0004), whereas the extent of ischemic myocardium correlated with the decrease in ejection fraction (r = 0.69, p = 0.0001). The defects present during occlusion reversed within a few hours.

CONCLUSIONS

Changes in left ventricular function and perfusion develop pari passu during coronary occlusion and are more severe when the left anterior descending artery is occluded. Although a significant correlation exists between the extent of the perfusion defect and the severity of the decrease in ejection fraction, there is a substantial individual variation with respect to changes in both myocardial perfusion and ventricular function during acute coronary occlusion.

How accurate is dobutamine stress electrocardiography for detection of coronary artery disease? Comparison with two-dimensional echocardiography and technetium-99m methoxyl isobutyl isonitrile (mibi) perfusion scintigraphy

OBJECTIVES

This study was designed to establish the appropriate diagnostic criteria for positive dobutamine electrocardiographic (ECG) stress test results and to compare their accuracy with those of dobutamine two-dimensional echocardiography and perfusion scintigraphy.

BACKGROUND

Conventional criteria for positive findings on ECG exercise testing may not be appropriate for use with dobutamine ECG stress testing.

METHODS

One hundred twenty-nine consecutive patients with an interpretable ECG and without previous myocardial infarction were prospectively studied at the time of coronary arteriography. All completed a standard dobutamine protocol (5 to 40 micrograms/kg body weight per min in 3-min dose increments) without side effects. Significant coronary artery disease, defined as > 50% lumen diameter stenosis of a major epicardial coronary artery on coronary angiography, was present in 83 patients. Empiric receiver operating curves were generated for various ECG criteria derived from computer-averaged signals.

RESULTS

The best ECG criterion, with a sensitivity of 42% and a specificity of 83%, was an ST segment shift, relative to baseline, of 0.5 mm 80 ms after the J point. The sensitivity of this criterion was greater than that of the conventional criterion of 1-mm ST segment depression 60 (23%) or 80 (18%) ms after the J point, was comparable to that of chest pain occurring during the test (44%, p = NS) but remained inferior to the sensitivities of technetium-99m methoxyl isobutyl isonitrile (mibi) perfusion (76%) or stress echocardiography (76%, p < 0.001, for both). The specificity of this criterion was not significantly different from that of technetium-99m mibi perfusion tomography (65%) or stress echocardiography (89%) but was superior to that of chest pain (59%, p < 0.025).

CONCLUSIONS

We conclude that this new criterion for dobutamine electrocardiography is specific but that an imaging technique is still required to accurately predict coronary artery disease.

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

This study compared the results of planar and single-photon emission computed tomographic (SPECT) imaging with tetrofosmin with those of 201Tl and coronary angiography. In three normal volunteers the images were normal by both 201Tl and tetrofosmin (planar and SPECT). In 23 patients with coronary artery disease, the images were abnormal in 20 patients by SPECT tetrofosmin, in 19 by planar tetrofosmin, in 20 by SPECT thallium, and in 18 by planar thallium (difference not significant). Both planar and SPECT images were divided into five segments per patient. There were 58 perfusion defects by SPECT tetrofosmin, 50 by planar tetrofosmin (difference not significant), 47 by SPECT thallium, and 42 by planar thallium (difference not significant). Perfusion defects were reversible in 47 segments (36%) by SPECT tetrofosmin, 35 (27%) by planar tetrofosmin, 31 (24%) by SPECT thallium (p < 0.05 vs SPECT tetrofosmin), and 31 (24%) by planar thallium (difference not significant). Among the 23 patients with coronary artery disease, 19 underwent coronary angiography. In these patients there were 32 diseased coronary arteries. Perfusion defects were present in 21 territories (66%) by SPECT tetrofosmin, 19 (59%) by planar tetrofosmin, 20 (63%) by SPECT thallium, and 18 (56%) by planar thallium. There was agreement between thallium and tetrofosmin in 108 of 130 segments (kappa statistics = 0.69 +/- 0.06). The images, especially with SPECT, are better with tetrofosmin than with 201Tl. Thus myocardial imaging with tetrofosmin provides results that are at least as good as those of 201Tl. Slightly more abnormal segments and more reversible defects are detected by tetrofosmin than by thallium imaging, especially with SPECT imaging.

Comparative ability of dobutamine and exercise stress in inducing myocardial ischaemia in active patients

OBJECTIVE

To compare the ability of dobutamine and exercise stress to induce myocardial ischaemia and perfusion heterogeneity under routine clinical circumstances.

DESIGN

86 active patients without previous myocardial infarction were studied by dobutamine and exercise stress protocols and coronary angiography. During both tests patients underwent electrocardiography, digitised echocardiography, and perfusion scintigraphy using Tc-99m methoxybutylisonitrile (MIBI) single photon emission computed tomography.

MAIN OUTCOME MEASURE

Coronary disease defined as an ST segment depression of > or = 0.1 mV, a resting or stress induced perfusion defect, or a resting or stress induced wall motion abnormality on exercise and dobutamine stress testing.

RESULTS

Dobutamine stress was submaximal in 51 patients because of ingestion of beta adrenoceptor blocking agents on the day of the test (n = 25) or failure to attain the peak dose owing to side effects (n = 28). Exercise was limited in 23 patients by non-cardiac symptoms. The peak heart rate with dobutamine was less than that attained with exercise (105 (25) v 132 (24) beats/min, P < 0.0001); the response to maximal dobutamine stress significantly exceeded that to submaximal stress. Peak blood pressure was greatest with exercise (206 (27) v 173 (25) mm Hg, P < 0.001), values at maximal and submaximal dobutamine stress being comparable. Electrocardiographic evidence of ischaemia was induced less frequently by dobutamine than exercise (32% v 77% of the 56 patients with significant coronary disease, P < 0.01), as was abnormal wall motion (54% v 88%, P < 0.001). Ischaemia was induced more readily with maximal stress of either type; thus the sensitivities of dobutamine and exercise echocardiography were comparable only in patients undergoing a maximal dobutamine testing (73% v 77%, NS). Perfusion heterogeneity was induced in 58% of patients with coronary disease at submaximal dobutamine stress, 73% at maximal dobutamine stress, and 73% at exercise stress (NS). Among 30 patients without coronary stenoses, normal function was obtained in 83% of echocardiography studies with dobutamine and in 80% with exercise (NS). Normal perfusion was identified in 70% of these patients at exercise MIBI, and 68% at dobutamine stress (NS).

CONCLUSIONS

In a group of patients studied under normal clinical circumstances antianginal treatment and inability to complete the stress protocol are frequent and compromise the capacity of dobutamine stress to induce ischaemia. In contrast, the induction of perfusion heterogeneity is less susceptible to submaximal stress.

The maze of myocardial perfusion imaging protocols in 1994

A confusing multitude of different myocardial perfusion imaging protocols have been proposed during the last few years. The impetus for this development was new insights in imaging with thallium 201 and the challenge to perform efficient imaging with the newly developed technetium 99m-labeled imaging agents. The practicing nuclear cardiologist is confronted with a true maze of options. This review describes in detail the various protocols, discusses advantages and disadvantages of each, and states, when appropriate, the personal preference of the author.

99mTc-sestamibi can improve the inferior attenuation of TL-201 myocardial spect imaging

Tl-201 myocardial scintigraphy (Tl study) tends to be attenuated by soft tissues (such as the diaphragm) due to its low energy emission. 99mTc-sestamibi (2-methoxy isobutyl isonitrile) is a relatively new agent with a higher energy emission and this characteristic accounts for the higher quality of 99mTc-sestamibi images. The purpose of this study is to evaluate the ability of 99mTc-sestamibi in alleviating the inferior attenuation of Tl studies. 99mTc-sestamibi SPECT myocardial scintigraphy was performed on 13 patients with inferior wall perfusion defects as determined by Tl study (but with normal coronary artery as evidenced by cardiac catheterization). All patients underwent Tl SPECT study using a standard procedure. Same-day protocol (rest-stress sequence) was used for 99mTc-sestamibi SPECT imaging. All images were analyzed by two independent observers. The results of our study reveal that 99mTc-sestamibi produced better images. The inferior wall perfusion defects in the T1 study were noted in one case only (1/13) in the 99mTc-sestamibi study. Our study suggests that 99mTc-sestamibi can remarkably reduce the inferior attenuation of Tl study.

Evaluation of myocardial perfusion defects by means of "bull's eye" images

The purpose of this study was to evaluate the usefulness of so-called "bull's eye" imaging as a simplified display of tomographic slices in the detection of coronary artery disease (CAD). A total of 64 patients were studied at stress and at rest, by single photon emission computed tomography (SPECT), either with thallium-201 (201Tl) or with technetium-99m methoxy-isobutyl-isonitril (Tc-MIBI). The myocardial perfusion defects detected by bull's eye image alone and in combination with visual analysis of tomographic images were evaluated in all cases, taking coronary arteriographic results as a gold standard. The overall sensitivity and specificity for detection of CAD were as follows: bull's eye imaging, 100% and 70.8%; tomographic imaging (SPECT), 90% and 91.6%. The results of bull's eye imaging and SPECT interpreted together were 96.6% and 83.3%. The regional sensitivity and specificity of bull's eye for individual coronary arteries were: right coronary artery (RCA), 100% and 73.7%; left anterior descending (LAD), 100% and 87.2%; left circumflex (LCx), 100% and 97.3%. For SPECT they were: RCA, 93.7% and 89.5%; LAD, 86.6% and 92.3%; LCx, 73.3% and 97.4%. For bull's eye with SPECT they were: RCA, 94.4% and 86.1%; LAD, 87.5% and 92.1%; LCx, 82.3% and 97.2%. We conclude that the bull's eye image display allows an easier and more objective assessment of myocardial perfusion defects and shows higher sensitivity. However, it has a relatively low specificity which can cause an overestimation of perfusion defects. Thus, visual analysis of bull's eye imaging is a useful diagnostic tool but must be evaluated in conjunction with tomographic imaging.

Clinical experience with technetium-99m teboroxime scintigraphy in patients referred for myocardial perfusion evaluation

A series of 30 patients (25 males, 5 females, age = 28-73 years) with a clinical indication of thallium-201 stress/4 hours redistribution scintigraphy has been studied using stress/rest (n = 7) or rest/stress (n = 23) protocols with technetium-99m teboroxime (CARDIOTEC, Squibb Diagnostics) in order to assess the clinical usefulness of this new molecule and to compare it to thallium. In all cases coronary artery disease was known or highly suspected, with a history of myocardial infarction in 18 cases (subacute n = 6, remote n = 12) and/or previous by-pass surgery or PTCA in 5 cases. Medical treatment was not discontinued at the time of stress testing. Coronary angiography was available for 27 patients. Exercise tests for both tracers were carried out on an ergometric bicycle during the same day and the levels of exercise achieved for the thallium studies were very similar to those achieved for teboroxime. Imaging was performed in three planar projections and sudies were evaluated using a model with 4 territories: septal and anterior assumed to correspond to the LAD artery, lateral and latero-posterior (= LCX), inferior and posterior (= RCA) and apex. Classification of results was: normal, ischemic, infarcted and infarcted with ischemia. With reference to the thallium-201 results, agreement was found in 86% (37/43) of normal regions and in 82% (63/77) of abnormal regions. Relative to documented coronary artery lesions (27 patients) sensitivity and specificity of thallium and teboroxime for exact correspondence between arteries and territories were, respectively: thallium, se = 71%, sp = 64%, teboroxime, se = 67%, sp = 75%.(ABSTRACT TRUNCATED AT 250 WORDS)

Radiopharmaceucticals for cardiovascular imaging

Radionuclide cardiac imaging is a noninvasive technique routinely used to detect coronary artery disease (CAD). This imaging modality includes techniques such as planar, single photon emission computed tomography (SPECT), positron emission tomography (PET) and radionuclide ventriculography--each technique having unique features of its own. Each technique employs various radiopharmaceuticals suitable for assessing different physiological and functional parameters that may become abnormal in the presence of CAD. Various cardiac imaging techniques include myocardial perfusion or blood flow, myocardial metabolism and cardiac function and wall motion. While radionuclide ventriculography gives the global functional status of the heart, SPECT and PET techniques provide information as to the regional blood flow and metabolic status of the myocardium. The following is a review of radiopharmaceuticals that are utilized clinically and in research in different types of nuclear cardiac imaging. Radiopharmaceuticals have been grouped according to the technique employed in which they are used. Various characteristics, merits and disadvantages of each radiopharmaceutical are discussed in detail.

Combined exercise radionuclide angiocardiography and single photon emission computed tomography perfusion studies for assessment of coronary artery disease

Although there is widespread use of exercise thallium 201 scintigraphy and radionuclide angiocardiography in patients with coronary artery disease (CAD), little is known about the independence, concordance, or relative importance of these studies in the diagnosis, prognosis, and assessment of the outcome of therapy. The use of both tests in the same patient has been impractical because of the logistic considerations imposed by two exercise tests on separate days, and excessive radiation exposure. New technetium 99m-labeled radiopharmaceuticals with high myocardial extraction now permit the simultaneous assessment of myocardial perfusion (single photon emission computed tomography [SPECT]) and ventricular function (radionuclide angiocardiography [RNA]) during treadmill exercise (exercise tolerance test [ETT]). The ability to perform all three tests during a single exercise session offers a very attractive technique to evaluate patients with CAD. The investigators studied 86 patients with chronic CAD using the same-day perfusion and function protocol combined with treadmill exercise. The results demonstrate good concordance between myocardial perfusion and ventricular function as indicated by a significant correlation between tomographic perfusion defect size and ejection fraction (P less than .0001, R = 0.75 at rest and P less than .0001, R = 0.76 during exercise). Stepwise logistic regression was used to model ETT, RNA, and SPECT variables against the presence of one or more 60% stenoses by quantitative angiography, an end point present in 47 patients. Univariable analysis showed all three tests (ETT, RNA, and SPECT) to be significant predictors of the end points (lambda 2 = 5.1, P less than .05; lambda 2 = 12.5, P less than .001; and lambda 2 = 16.1, P less than .001, respectively). Multivariable analysis demonstrated that SPECT provided more diagnostic information than ETT and RNA (Lambda 2 = 16.1, P less than .001).(ABSTRACT TRUNCATED AT 250 WORDS)

Myocardial perfusion imaging with technetium-99m-labeled agents

Thallium-201 (201Tl) is suboptimal as a single-photon emitting agent for myocardial perfusion imaging, in view of its low-energy photons and long half-life. To circumvent these limitations, two new myocardial perfusion imaging agents labeled with technetium-99m (99mTc) have been developed. They are Tc-sestamibi and Tc-teboroxime. Clinical trials of myocardial perfusion with both tracers have shown results similar to those obtained with 201Tl for detection of coronary artery disease. Results to date indicate that Tc-sestamibi accurately detects and locates myocardial infarction and can accurately assess both left and right ventricular ejection fractions by the first-pass technique. In addition, research has shown that rest-stress studies can be performed on the same day and that Tc-sestamibi can be used to assess the results of thrombolytic therapy. Tc-teboroxime has excellent myocardial tracer uptake characteristics but is cleared very rapidly from the myocardium. These features make Tc-teboroxime well suited to rapid serial studies. These new technetium myocardial perfusion agents have just become available for routine clinical use and are likely to replace 201Tl in many of its clinical applications.

Technetium-99m teboroxime scintigraphy. Clinical experience in patients referred for myocardial perfusion evaluation

In order to evaluate the clinical value of a new myocardial perfusion tracer, a series of 30 patients (25 male, 5 female, mean age 56 years) referred for thallium 201 stress/redistribution scintigraphy has been studied using stress/rest (n = 7) or rest/stress (n = 23) protocols with technetium 99m teboroxime (Cardiotec SQUIBB). In all cases coronary artery disease was known or highly probable, with a history of myocardial infarction in 18 cases. Medical treatment was not discontinued at the time of stress testing, and coronary angiography was available in 27 patients. Exercise tests for both tracers were carried out on a bicycle ergometer during the same day, and the levels of exercise achieved for the 201Tl study were very similar to those achieved for 99mTc-teboroxime. Studies performed in three planar projections were evaluated using a model with four territories: septal and anterior assumed to correspond to the left anterior descending artery, lateral and latero-posterior (left circonflex), inferior and posterior (right coronary artery) and apex. Classification of results was: normal, ischaemic, infarcted and infarcted with ischaemia. On comparison with the 201Tl results, agreement was found in 86% (37/43) of normal regions and in 82% (63/77) of abnormal regions. Relative to documented coronary artery lesions (27 patients), sensitivity and specificity of 201Tl and 99mTc-teboroxime for exact correspondence between arteries and territories were respectively: 201Tl: sensitivity 64%, specificity 60%; 99mTc-teboroxime: sensitivity 62%, specificity 77%.(ABSTRACT TRUNCATED AT 250 WORDS)

Development and prospective application of quantitative 2-day stress-rest Tc-99m methoxy isobutyl isonitrile SPECT for the diagnosis of coronary artery disease

The clinical diagnostic accuracy of 2-day stress/rest quantitative Technetium-99m (Tc-99m) methoxy-isobutyl-isonitrile (Tc-sestamibi) single photon emission computerized tomography (SPECT) was assessed in a validation population of 61 patients from two different sites using two different camera/computer systems. The study population was made up of 53 catheterized patients, 29 from Cedars-Sinai Medical Center (CSMC) and 24 from the University of Texas Southwestern Medical Center (UTSMC), and eight UTSMC patients with a less than 5% pre-test likelihood of coronary artery disease. Interpretation employed gender-specific normal limits developed in an additional 15 men and 8 women at CSMC with less than a 5% likelihood of significant coronary artery disease. The results from CSMC compared with those from UTSMC were not different from each other. The overall sensitivity for detection of patients with coronary artery disease (greater than or equal to 50% stenosis) was 94% (CSMC: 92%, UTSMC: 95%). Overall specificity in the five patients with normal coronary arteriograms was 80% (CSMC: 67%, UTSMC: 100%). The normalcy rate in patients with a low likelihood of coronary artery disease was 88%. Vessel sensitivity was 85% (CSMC: 84%, UTSMC: 85%), while vessel specificity was 71% (CSMC: 72%, UTSMC: 69%). There was also no significant difference in the sensitivities and specificities between male and female populations. In addition, the agreement with coronary angiography for assessment of disease extent (normal coronary arteriogram, single or multivessel disease) was 75% (kappa = 0.6 +/- 0.1). This study demonstrated that Tc-sestamibi SPECT by quantitative analysis is accurate for the detection and localization of coronary artery disease. Furthermore, the CSMC quantitative method was shown to provide similar diagnostic accuracy when applied to data acquired at a different site using a different camera/computer system.

Preparation and evaluation of 99mTc-t-butylisonitrile (99mTc-TBI) for myocardial imaging: a kit for hospital radiopharmacy

A previous method was modified to obtain [99mTc(TBI)6]+ by reacting Zn(TBI)2Br2 directly with 99mTcO4- in the presence of Sn2+ ions. [Cu(TBI)4]Cl was next used as a source of TBI. On reaction with 99mTcO4- and Sn2+ ions for 3 min at 100 degrees C, [99mTc(TBI)6]+ product of radiochemical purity greater than 90% and yield greater than 70% was obtained. Data of biodistribution in rats (2-2.5% in heart) and biokinetics in rabbits were satisfactory. The kit formulation was found to be stable and also safe for administration.

The use of magnetic resonance imaging in exertional compartment syndromes

This prospective, double-blind study was carried out to assess the usefulness of magnetic resonance imaging (MRI) as a noninvasive method in the diagnosis of chronic compartment syndrome (CCS). As well, a new radiopharmaceutical known as methoxy isobutyl isonitrile that has been shown to be taken up by muscle in direct proportion to its blood flow was used to illustrate the possible pathophysiology of this syndrome. Twenty patients with a history of chronic leg pain and possible diagnosis of CCS and five normal volunteers had preexercise and postexercise MRI, nuclear medicine imaging, and static and dynamic slit catheter pressure studies. Nine patients had classic symptoms; only five of these nine had abnormal pressure studies. The other 11 patients had an element of pain at rest and had normal pressure studies. The nuclear blood flow studies were normal in all 25 legs tested in this study. Measurement of intrinsic MRI parameters T1 and T2 in the normal legs as well as in those with an atypical history showed a marked elevation with exercise and a gradual return to baseline postexercise that was similar to the pressure curves. In the five patients with a clinical history and elevated pressures, four had abnormal MRI studies with failure of T1 to return to baseline values. Although these results demonstrate the potential of MRI as a tool for noninvasively monitoring muscle status, clinical history and examination remain important in the diagnosis of CCS. This study indicates that the pathophysiology of exertional compartment syndrome does not appear to be related to ischemia.