Comparative scanning of thyroid nodules with technetium-99m pertechnetate and technetium-99m methoxyisobutylisonitrile

Thyroid imaging was performed using technetium-99m methoxyisobutylisonitrile and technetium-99m pertechnetate in 58 patients. The ^99mTc-pertechnetate scans showed a total of 77 nodules: 60 cold, 13 hot and 4 of normal activity. There was no ^99mTc-MIBI accumulation in 46.4% of ^99mTc-pertechnetate cold nodules; 27 (45%) of these nodules showed ^99mTc-MIBI uptake with the same intensity as the surrounding normal tissue, and five (8.6%) became hot with ^99mTc-MIBI. Of the ^99mTc-pertechnetate hot nodules 11 (84.6%) could not be differentiated from the normal extranodular tissue on the ^99mTc-MIBI scan. The histopathology of 34 surgically removed nodules proved that increased, normal or decreased ^99mTc-MIBI accumulation is not specific for thyroid malignancy and that the ^99mTc-MIBI uptake depends mainly on the viability of thyroid tissue.Correspondence to: I. Földes     

Parathyroid scintigraphy: comparison of technetium-99m methoxyisobutylisonitrile and technetium-99m tetrofosmin studies

We report the preliminary results of a prospective study demonstrating tetrofosmin uptake in surgically and histologically proven parathyroid adenomas. In ten patients with primary chronic hyperparathyroidism, parathyroid imaging was performed using (1) technetium-99m methoxyisobutylisonitrile (MIBI) and (2)^99mTc-1,2-bis(bis(2-ethoxyethyl)phosphino)ethane (tetrofosmin) within a time interval of 3–5 days. Both tracers correctly identified the parathyroid adenomas by focal prolonged tracer retention. On visual inspection image contrast was generally higher with MIBI than with tetrofosmin in all the patients studied. Tetrofosmin showed a slower elimination from the parathyroid adenomas than MIBI in six of the ten cases. Our preliminary results show that tetrofosmin, like MIBI, as a feasible, sensitive tracer for parathyroid scintigraphy. For routine use, the rapid kit preparation without heating and the lower radiation dose to the patient make tetrofosmin an alternative tracer for parathyroid scintigraphy. Further evaluation is needed to determine which of the two tracers is the more sensitive for the detection of parathyroid adenomas, and which tracer properties better reflect the degree of endocrine activity.[/p]     

Rest-injected thallium-201 redistribution and resting technetium-99m methoxyisobutylisonitrile uptake in coronary artery disease: relation to the severity of coronary artery stenosis

To compare rest-injected thallium-201 (Tl) redistribution and resting technetium-99m methoxyisobutylisonitrile (^99mTc-MIBI) myocardial uptake in chronic coronary artery disease (CAD), 15 patients with angiographically proven CAD and left ventricular (LV) dysfunction (ejection fraction 34%±9%) were studied. All patients underwent rest-redistribution Tl and resting ^99mTc-MIBI cardiac imaging. Gated ^99mTc-MIBI images were also acquired to assess regional LV wall motion (WM). Myocardial segments (n=225) were divided into three groups on the basis of the degree of coronary artery stenosis: group 1 (total occlusion, n=82), group 2 (50%–99% of stenosis, n=84) and group 3 (<50% of stenosis, n=59). WM was significantly worse in groups 1 and 2 compared to group 3 (P<0.001), but no difference was observed between groups 1 and 2. TI and ^99mTc-MIBI uptake were significantly lower in groups 1 and 2 compared to group 3 (P < 0.001), and in group 1 compared to group 2 (P<0.001). When TI and ^99mTc-MIBI uptake were directly compared, TI uptake was higher than ^99mTc-MIBI uptake in group 1 (P<0.001), while no significant difference was observed in groups 2 and 3. Thus, both rest-injected TI redistribution and resting ^99mTc-MIBI uptake reflected the severity of coronary artery stenosis in CAD. However, in myocardial segments with total coronary occlusion T1 uptake was significantly higher than ^99mTc-MIBI uptake. Our data suggest that rest-injected Tl redistribution cardiac imaging may identify, more accurately than resting ^99mTc-MIBI imaging, the presence of viable myocardium in chronic CAD, particularly when the coronary blood flow is severely impaired.     

The use of technetium-99m methoxyisobutylisonitrile breast scintigraphy to evaluate palpable breast masses

Thirty-eight female patients (age range: 31–79 years) with breast masses underwent technetium-99m methoxyisobutylisonitrile (^99mTc-MIBI) breast scintigraphy in order to assess the value of this technique in the detection of breast carcinomas and in their differentiation from benign breast masses. The results showed that 27 of the 32 cases of breast carcinoma were detected by ^99mTc-MIBI breast scintigraphy. In contrast, none of the six benign lesions could be detected by this method. The diagnostic sensitivity, specificity and accuracy were 84%, 100% and 87%, respectively, in the differentiation of malignant and benign breast masses. In conclusion, we consider ^99mTc-MIBI breast scintigraphy is useful in distinguishing malignancies from benign breast masses. Correspondence to: C.H. Kao     

Comparison of technetium-99m sestamibi left ventricular wall motion and perfusion studies with thallium-201 perfusion imaging: in search of the combination of variables with the highest accuracy in predicting coronary artery disease

Measurements of myocardial perfusion and ventricular function are expected to provide additional information in the detection of coronary artery disease (CAD). The purpose of this study was threefold: (1) to determine to what extent technetium-99m sestamibi wall motion yields different information compared with^99mTc-sestamibi and thallium-201 perfusion; (2) to test which information unique to either study is of value in diagnosing CAD; and (3) to assess the combination of variables with the highest diagnostic accuracy. Perfusion and wall motion scores (at rest and during exercise) obtained from visual and quantitative planar²⁰¹T1 and^99mTc-sestamibi scintigraphy of 60 patients with suspected CAD were compared with the angiographic results by means of a polytomous logistic regression model and the diagnostic values were compared with one another. All univariate variables were significantly related to the probability of CAD and its extent. Comparative studies revealed a large degree of correlation between²⁰¹T1 stress and redistribution variables. The rest^99mTc-sestamibi and wall motion studies contained partially different information. Stepwise logistic regression analysis showed the strongest diagnostic power for the combination of²⁰¹Tl visual analysis of the stress images with quantitative redistribution images (sensitivity 93%, specificity 71%). The diagnostic power was similar for all combinations of visual and quantitative analyses of the exercise and redistribution images. The strongest diagnostic power of the^99mTc-sestamibi variables was the score of the diastolic stress image (sensitivity 91%, specificity 79%). Comparable sensitivity and specificity estimates were found when both optimal models were compared. Wall motion studies did not have additional diagnostic power. Although^99mTc-sestamibi wall motion studies, both at rest and during exercise, provide information in addition to the^99mTc-sestamibi or²⁰¹Tl myocardial perfusion variables, the information does not enhance the diagnostic power with regard to the prediction of CAD.     

Assessment of systolic wall thickening using technetium-99m methoxyisobutylisonitrile in patients with coronary artery disease: relation to thallium-201 scintigraphy with re-injection

The results of resting planar ECG-gated technetium-99m methoxyisobutylisonitrile (^99mTc-MIBI) imaging were compared with those of thallium-201 (TI) reinjection after exercise-redistribution scintigraphy in 20 patients (19 men, 1 woman, mean age 53±10 years) with angiographically proven coronary artery disease. Eight normal subjects (seven men, one woman, mean age 50±8 years) constituted the control group. In these subjects, only resting^99mTc-MIBI imaging was performed. The standardized percent count increase from end-diastole to end-systole was calculated as an index of wall thickening in 13 segments for each study. Regional wall thickening index (WTI) and^99mTc-MIBI uptake were significantly different (P<0.05) among segments classified as normal, reversible defects, irreversible defects with increased tracer uptake after re-injection (Re+) or irreversible defects with unchanged tracer uptake after re-injection (Re-) on TI imaging. Furthermore, WTI and^99mTc-MIBI uptake were significantly higher (P<0.05) in Resegments with moderate reduction of T1 uptake (50% of peak activity) than in Re- segments with severe reduction of TI uptake (<50% of peak activity). A significant relationship between WTI and the results of TI scintigraphy was observed (rho=0.71,P<0.0001). The percentage of Re- segments with severe reduction of WTI was significantly higher compared to Re+ segments (64% vs 3%,P<0.01). Furthermore, compared with moderate Re- segments, a significantly higher percentage of severe Re- segments showed a severe reduction of WTI (86% vs 48%,P<0.01). Our data document a close relationship between^99mTc-MIBI regional wall thickening, myocardial perfusion and TI uptake after reinjection. The results of this study suggest that regional WTI decreased significantly as myocardial perfusion decreased. In addition, regional wall thickening was preserved in segments with exercise-induced ischaemia and enhanced TI uptake after re-injection.     

Comparison of technetium-99m methoxyisobutylisonitrile and gallium-67 citrate scanning in the assessment of lymphomas

The aim of this study was to compare the value of scintigraphy using technetium-99m methoxy-isobutylisonitrile (MIBI) with that of scintigraphy using gallium-67 citrate in the assessment of Hodgkin's disease and non-Hodgkin's lymphoma and to relate these results with those of CT scan and MRI. Fifty-eight patients were included either for a follow-up examination or for monitoring of their treatment. Twenty-three residual masses were studied. A whole-body scan was performed, followed by single-photon emission computed tomography (SPET) 20 min after injection of 740 MBq of^99mTc-MIBI and 72 h after injection of 185 MBq of⁶⁷Ga citrate. The overall sensitivity of^99mTc-MIBI and⁶⁷Ga citrate was 71% and 68%, respectively, and the overall specificity was 76% and 44%, respectively. For residual masses, the sensitivity was 44% with both tracers and the specificity was 80% with^99mTc-MIBI and 53% with⁶⁷Ga citrate. The positive predictive values were 85% and 68% and the negative predictive values were 59% and 44%, respectively. The signal-to-background ratio was 1.5 for^99mTc-MIBI and 2 for⁶⁷Ga citrate. At present,^99mTc-MIBI cannot replace⁶⁷Ga citrate in the assessment of lymphomas.     

Scintimammography with technetium-99m methoxyisobutylisonitrile: results of a prospective European multicentre trial

The aim of the trial was to determine the diagnostic accuracy of scintimmammography with technetium-99m methoxyisobutylisonitrile (^99mTc-MIBI) in the detection of primary breast cancer and to verify its clinical usefulness. A total of 246 patients with a suspicious breast mass or positive mammogram were included in this prospective European multicentre trial. At 5 min and 60 min (optional) p.i. two lateral prone images were acquired for 10 min each; 30 min p.i. one anterior image was acquired for 10 min. There were 253 lesions (195 palpable and 58 non-palpable), in respect of which histology revealed 165 cancers and 88 benign lesions. Institutional and blinded read results were correlated to core laboratory histopathology results obtained during excisional biopsy. Diagnostic accuracy for the detection of breast cancer was calculated per lesion. The overall sensitivity and specificity of blinded read scintimammography were 71% and 69%, respectively. For palpable lesions, the sensitivity of blinded read and institutional read scintimammography was 83% and 91%, respectively. Sensitivity was not dependent on the density of the breast tissue. Invasive ductal and invasive lobular cancers showed similar sensitivity. The sensitivity and specificity of mammography were 91% and 42%, respectively, and did not depend on the tumour size. In 60% of false-negative mammograms, ^99mTc-MIBI was able to diagnose malignancy (true-positive). High-quality imaging with ^99mTc-MIBI has a high diagnostic accuracy for the detection of primary breast cancer. Used as a complementary method, scintimammography with ^99mTc-MIBI can help to diagnose breast cancer at an earlier stage in patients with dense breasts. Received 11 October and in revised form 12 December 1997     

Scintimammography with technetium-99m methoxyisobutylisonitrile: comparison with mammography and magnetic resonance imaging

The aim of the study was to compare the diagnostic accuracy of scintimammography with technetium-99m methoxyisobutylisonitrile (MIBI; SMM) in the detection of primary breast cancer with that of mammography (MM) and magnetic resonance imaging (MRI). Fifty-six patients with suspected lesions detected by palpation or MM were included in the study. Within the 4 weeks preceding excisional biopsy, MM and MRI were performed in all patients. Between 5 and 10 min after the injection of 740 MBq^99mTc-MIBI, SMM in the prone position was performed. In the total group of 56 patients, 43 lesions were palpable, while 13 were non-palpable but were detected by MM. Breast cancer was confirmed by histopathology in 27 of the patients (22 palpable and 5 non-palpable carcinomas). The tumour size ranged from 6 to 80 mm in diameter. For non-palpable lesions, the sensitivity of SMM, MM and MRI was 60%, 60% and 100%, respectively, while the specificity was 75%, 25% and 50%, respectively. For palpable breast lesions, all methods showed high sensitivity (SMM 91%, MM 95%, MRI 91%) but SMM demonstrated significantly higher specificity (SMM 62%, MM 10%, MRI 15%). In two mammographically negative tumours (dense tissue), SMM showed a positive result. In comparison to MRI, one additional carcinoma could be diagnosed by SMM. It may be concluded that for palpable breast lesions, the diagnostic accuracy of SMM is superior to that of MM and MRI. Through the complementary use of SMM it is possible to increase the sensitivity for the detection of breast cancer and multicentric disease. In patients in whom the status of a palpable breast mass remains unclear, SMM may help to reduce the amount of unnecessary biopsies.     

Prediction of reversible perfusion defects by quantitative analysis of post-exercise electrocardiogram-gated acquisition of technetium-99m 2-methoxyisobutylisonitrile myocardial perfusion scintigraphy

The aim of this study was to assess the reliability of the quantitative analysis of regional wall thickening with electrocardiographic-gated technetium-99m 2-methoxyisobutylisonitrile (SESTAMIBI) in predicting the reversibility of stress-induced perfusion defects. The assumption was that a preserved resting wall thickening in a segment with stress-induced perfusion defect would predict normal resting perfusion. Twenty-five patients with suspected coronary artery disease underwent planar stress-rest SESTAMIBI scintigraphy. The wall thickening was quantitatively evaluated as percentage increase in counts from diastole to systole; a ratio defined as the wall thickening index (WTI) between patient and normal profile (mean - 2 SD) below 1 was considered abnormal. Improvement of the perfusion pattern at rest was observed in 76% (54/71) of segments with a stress-induced perfusion defect; 90% of these segments had a (WTI) > 0.8. Five segments (9%) showed fixed perfusion defects despite a WTI value > 0.8. In conclusion, quantitative analysis of regional wall thickening by electrocardiographic-gated SESTAMIBI identifies segments with reversible perfusion defects; this may overcome the need for studies at rest and may direct the detection of hypoperfused but viable myocardium. Offprint requests to: C. Marcassa     

Optimization of X-ray mammography and technetium-99m methoxyisobutylisonitrile scintimammography in the diagnosis of non-palpable breast lesions

The purpose of this study was to evaluate the contribution of technetium-99m methoxyisobutylisonitrile (MIBI) scintimammography to the early diagnosis of breast cancer in 78 patients with non-palpable breast lesions detected by mammography. In all cases biopsy was indicated and they were classified into three groups according to the mammographic findings: high (28), intermediate (30) and low (20) mammographic probability of malignancy. Histological diagnosis confirmed 37 benign and 41 malignant lesions. In the high-probability group ^99mTc-MIBI scintimammography changed the four false-positives into true negatives at the expense of two false-negatives; in the intermediate group it changed nine of the 17 false-positives into true-negatives at the expense of one false-negative, and in the low-probability group it changed five of the 16 false-positives into true-negatives without false-negatives. Applying scintimammography to patients included in the intermediate and low-probability groups together, 14 of the 33 mammographic false-positives were changed into true-negatives with 1 false-negative; thus, 41% of the unnecessary biopsies would have been avoided. When MIBI scintimammography was applied to the low-probability group, the negative predictive value was 100% and the unnecessary biopsies would have been reduced by 31%. Received 10 November 1997 and in revised form 19 January 1998     

ECG-manifest and ECG-silent dipyridamole technetium-99m sestamibi SPET perfusion defects in patients with ischaemic heart disease

At dipyridamole myocardial scintigraphy, perfusion defects are seldom backed up by significant ECG changes. This would suggest myocardial blood flow heterogeneity, rather than true ischaemia, as the cause of the scintigraphic abnormalities. Electrocardiographic surface mapping has been documented to be more accurate than standard 12-lead ECG in the detection of provoked ischaemia. Thus, to investigate the relationship between ECG changes and perfusion abnormalities, body surface maps were recorded during dipyridamole infusion in 55 subjects (11 normals and 44 patients with ischaemic heart disease) undergoing dipyridamole technetium-99m sestamibi single-photon emission tomography (SPET). All had a normal resting ECG. The extent and severity of the sestamibi defect were quantified. New negative areas in the isointegral maps and rest-dipyridamole map differences >2 SD from normal limits were considered abnormal. After dipyridamole in normals, neither perfusion defects nor>-1 mm ST segment depression on 12-lead ECG nor new negative areas in isointegral maps occurred. In patients, dipyridamole induced new perfusion defects in 35 (80%) but ST segment depression in only 18 (41%,P<0.001). Of the 35 patients with perfusion defects, 17 (49%, group 1) showed ST segment depression, while the other 18 (51%, group 2) did not. Abnormal body surface maps were found in 100% of group 1 and 88% of group 2 patients (NS). In group 1, the provoked hypoperfusion was of greater extent (P=0.007) and severity (P=0.01) and the onset of map abnormalities was significantly earlier (P<0.001) than in group 2; time to map abnormalities was also significantly shorter than time to ST segment depression (P=0.01). In the 35 patients with complete scintigraphic, body map and angiographic data, the severity of reversible perfusion defect proved to be the strongest correlate of ST segment depression upon logistic regression analysis. Thus, sestamibi SPET abnormalities after dipyridamole are almost always associated with electrical changes on body surface maps, suggesting myocardial ischaemia as their cause. The much less common 12-lead ECG changes are slower to appear and reflect a more severe hypoperfusion.     

Effect of coronary reperfusion on technetium-99m methoxyisobutylisonitrile uptake by viable and necrotic myocardium in the dog

Technetium-99m hexakis-2-methoxyisobutyl isonitrile (^99mTc-MIBI) distribution is flow-dependent, permitting the imaging of coronary perfusion defects. However, the behaviour of this tracer in viable and necrotic tissues within the ischaemic area at risk is still being debated. In a clinically relevant canine model, dogs were submitted either to a 24-h permanent occlusion (group 1) of the left descending coronary artery (LAD) or to a 90-min LAD occlusion followed by 22.5 h reperfusion (group 2). ^99mTc-MIBI and radiolabelled microspheres were injected 3 h before sacrifice. After delimiting the area at risk and the infarct by Evans blue perfusion and triphenyltetrazolium chloride staining, heart slices were imaged by scintigraphy and tissue radioactivity measured in a gamma-counter. In the necrotic area of both groups, the ^99mTc-MIBI distribution was proportional to the myocardial blood flow, approximating a 1:1 ratio (identity line slope l, intercept 0) with highly significant correlation coefficients (group 1 r = 0.87, group 2 r = 0.86), whereas in the viable-ischaemic area of both groups, the data points are widespread above and below the identity line, indicating both over- and underestimations of blood flow in these tissue areas. These results were more pronounced following reperfusion as compared with permanent occlusion. Multiple linear regression analysis confirms differences (P < 0.001) in ⁹⁹Tc-MIBI distributions between the viable-ischaemic and the necrotic zones. Delineation of the ischaemic area at risk was possible only with permanent occlusion. A hypoper-fused area was observed after reperfusion but differs from the anatomical infarcted area. These results indicate that the ^99mTc-MIBI distribution is not significantly influenced by myocardial cell death, whereas the relationship of ^99mTc-MIBI to blood flow in the remaining viable-ischaemic myocardium salvaged by reperfusion appears more deeply affected. Therefore, the influence of tissue viability on the ^99mTc-MIBI distribution in the myocardium must be reconsidered in the light of these observations.Supported by grant IU-0027, Medical Research Council of CanadaPostdoctoral fellow of the Canadian Heart FoundationBursor from the Canadian Heart Foundation Offprint requests to: J.-G. Latour     

Technetium-99m teboroxime scintigraphy

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 99^mTc-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 lateroposterior (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%. These results, obtained in a given clinical context, indicate the ability of Cardiotec to evaluate myocardial perfusion with a significant saving in time, since the complete study duration (stress and rest) was: ²⁰¹Tl, 4 h 35 min±21 min; ^99mTc-teboroxime, 1 h 52 min ±29 min. Nevertheless, the high liver uptake was responsible for 68% of non-evauble inferior segments and the limited acquisition time makes the applicability of SPET questionable.     

Localization of parathyroid enlargement: experience with technetium-99m methoxyisobutylisonitrile and thallium-201 scintigraphy,ultrasonography and computed tomography

Technetium-99m methoxyisobutylisonitrile (MIBI), like thallium-201, has recently been introduced as a myocardial perfusion agent and is now also showing very promising results in parathyroid scintigrapy. The results of ²⁰¹Tl/^99mTc-pertechnetate and ^99mTc-MIBI/^99mTc-pertechnetate subtraction scintigraphy, ultrasonography and computed tomography are presented in a series of 43 patients operated on for hyperparathyroidism. All four imaging modalities were confirmed to be reliable, scintigraphy being the most accurate. Sensitivities ranged from 81% to 95%, that of ^99mTc-MIBI being the highest. Moreover this tracer, which has more favourable physical and also biochemical properties, yielded images of superior quality. This allowed localization of the lesion by visual inspection only in as many as 86% of the patients with positive ^99mTc-MIBI/^99mTc-pertechnetate subtraction scintigraphy. We believe that the higher sensitivity, superior image quality and lower cost of ^99mTc-MIBI imaging will make ^99mTc-MIBI the new radiopharmaceutical of choice for parathyroid scintigraphy (when one takes into account the stability of labelling with large activities it is possible to perform three or four cardiac studies together with one parathyroid scintigraphic examination using one lyophililzed vial).     

Exercise gated planar myocardial perfusion imaging using technetium-99m sestamibi for the diagnosis of coronary artery disease: an alternative to exercise tomographic imaging

Single-photon emission tomography (SPET) using technetium-99m labelled myocardial tracers (e.g.^99mTc-sestamibi) has become one of the most popular myocardial imaging methods for the diagnosis of coronary artery disease (CAD). This prospective study was designed to evaluate the diagnostic performance of^99mTc-sestamibi exercise gated planar myocardial imaging by comparison with both visual and quantitative analyses of SPET. The study was conducted in 115 consecutive patients with known or suspected CAD, including 54 patients with a previous myocardial infarction (MI), referred for exercise testing prior to coronary angiography. Multi-gated planar imaging and SPET were performed after bicycle exercise. The end-diastolic (ED) and SPET images were visually scored (SVi). Myocardial uptake was quantitated on SPET slices using maximum count circumferential profiles (SQu) and defect extent was measured by comparison with gender-matched data sets obtained from 27 controls (<5% likelihood of CAD). CAD was defined as coronary artery stenosis >50% and/or regional wall motion abnormality. The cut-off criteria for positivity of the three procedures were determined from receiver operating characteristic (ROC) curves derived from the data of patients without previous MI. The area under the ROC curves was similar for ED, SVi and SQu. This was confirmed by the analysis of sensitivity performed using the ROC curve-derived cut-off criteria, in patients with or without previous MI. SVi was more sensitive than ED in identifying the diseased vessel(s) (ED: 41% vs SVi: 80%;P<0.0005) but ED was more specific in this respect (ED: 79% vs SVi: 61%;P<0.0005). We conclude that visual analysis of ED images obtained from gated^99mTc-sestamibi stress planar imaging is a valuable alternative to SPET imaging for the diagnosis of CAD. SPET is, however, more accurate for the evaluation of the disease extent and localization and therefore remains the method of choice for the assessment of myocardial perfusion.     

Technetium-99m methoxyisobutylisonitrile localizes an ectopic ACTH-producing tumour: case report and review of the literature

Extensive investigation including whole-body examinations with computed tomography and magnetic resonance imaging did not detect the suspected ectopic ACTH-producing tumour in a patient with advanced Cushing's syndrome and hypokalemic alkalosis. Gamma camera examination with technetium-99m methoxyisobutylisonitrile (MIBI) depicted the tumour, which was localized in the anterior neck and mediastinum. This was later verified by surgery. ^99mTc-MIBI is normally used for myocardial scintigraphy. Its accumulation is unspecific and merely reflects metabolic activity. Despite this, the present case shows that examination with this agent can provide important information with regard to tumour localization in a given situation, thereby serving as a complement to other imaging modalities. The current literature on ^99mTc-MIBI for tumour diagnosis is reviewed. Correspondence to: H. Jacobsson     

Perioperative myocardial perfusion scintigraphy at rest with technetium 99m methoxyisobutylisonitrile before and after coronary bypass operations

Eighteen patients were examined at rest by technetium 99m methoxyisobutylisonitrile (^99mTc-MIBI) myocardial scintigraphy 1 day before and 1 week after aorto-coronary bypass operation with planar and single photon emission tomography (SPET) imaging. One day postoperatively, a planar scintigraph in the intensive care unit (ICU) was done. Inter-observer variability was 3.8% for all examinations and for SPET alone, 3.9%. The quality of the planar images taken under emergency conditions in the ICU was quite comparable with those taken under routine conditions. The postoperative myocardial infarction in a patient who died 6 days later could clearly be demonstrated. In 16.2% of all segments which were hypoperfused at rest on preoperative scintigraphy, an amelioration of perfusion could be shown in the 1 st week after the bypass operation. ⁹⁹Tc-MIBI proved to be a useful agent to assess perioperative perfusion, in the ICU as well as under standard conditions. Offprint requests to: G.K. von Schulthess     

Detection of coronary artery disease by dynamic planar and single photon emission tomographic imaging with technetium-99m teboroxime

To test the clinical significance of technetium-99m teboroxime regional myocardial clearance in the detection of coronary artery disease, 25 patients underwent dynamic planar or single-photon emission tomographic (SPET) myocardial imaging with ^99mTc-teboroxime after exercise and again 2 h later at rest. All patients underwent both thallium-201 exercise and redistribution SPET and coronary arteriography. The early phases of exercise ^99mTc-teboroxime myocardial clearance determined by dynamic planar imaging showed a significant difference between normal and post-stenotic myocardial regions (clearance rate constant k: 0.047±0.005 min' versus 0.034±0.003 min^–1, P <0.001). Reflecting this differential clearance between myocardial regions, an early redistribution-like phenomenon was observed in a significant number of myocaridal segments by comparing serially acquired post-exercise ^99mTc-teboroxime SPET images. These results indicated that the analysis of ^99mTc-teboroxime myocardial clearance was of potential use in the detection of coronary artery disease, yielding additional information to that provided by the tracer distribution analysis. Although the early redistribution-like phenomenon of ^99mTc-teboroxime could be the source of underestimation of ischaemia if acquisition of the initial post-exercise image were delayed, it could also prove useful in the early differentiation of ischaemia from scar because when the phenomenon was observed in delayed post-exercise images, the rest study could be omitted under some circumstances.     

Myocardial technetium-99m sestamibi single-photon emission tomography as a prognostic tool in coronary artery disease: multivariate analysis in a long-term prospective study

To date several studies have evaluated the accuracy of thallium-201 myocardial scan in risk stratification of coronary artery disease (CAD), while reports using technetium-99m methoxyisobutylisonitrile (MIBI), a tracer particularly suited to single-photon emission tomographic (SPET) imaging, are lacking. To rectify this omission, a prospective study was started in 1988 and at present 176 consecutive, and thus unselected, patients have been enrolled. All of them have been submitted to stress-rest MIBI SPET for the diagnosis or evaluation of CAD; 147 patients (121 males and 26 females, aged 53±9 years) have completed a surveillance period of at least 36 months following the scintigraphic study (range 36–60 months, mean 43). Sixty-one patients had a documented previous myocardial infarction. The mean pretest likelihood of CAD was 44% in the patients without prior infarction. The main anamnestic, clinical, EKG and scintigraphic findings were evaluated and statistically correlated with the incidence of ensuing cardiac events using both univariate (chi-square test) and multivariate analysis (logistic regression model). Twenty-nine patients suffered from a cardiac event during the follow-up period (i.e. three cardiac deaths, six myocardial infarctions and 20 cases of unstable angina). Statistical multivariate analysis identified MIBI scan as the only highly significant and independent prognostic predictor [P=0.006, relative risk (RR)=17.62]. In detail, the most important scintigraphic parameters were the presence of a reversible defect (P=0.0089, RR=5.11) and the extension of the stress perfusion defect (P=0.0255, RR=3.27). The presence of typical angina proved to be a slightly significant predictor (P=0.051, RR=2.45), while no other examined parameter showed a significant correlation with a bad prognosis. In conclusion, MIBI SPET can be considered a useful tool in the risk stratification of CAD patients. The presence of a reversible perfusion defect or an extensive defect appears responsible for a clear increase in the probability of subsequent cardiac events, thus indicating a more aggressive therapeutic approach to be appropriate.This work was presented in part at the 6th World Congress of the World Federation of Nuclear Medicine and Biology in Sydney, Australia (28–30 October 1994).