Influence of infarct-zone viability detected by rest Tc-99m sestamibi gated SPECT on left ventricular remodeling after acute myocardial infarction treated by percutaneous transluminal coronary angioplasty in the acute phase

BACKGROUND: The purpose of this study was to assess the value of technetium 99m sestamibi gated single photon emission computed tomography (SPECT) in predicting the evolution of left ventricular volumes in patients treated successfully in the acute phase of a myocardial infarction (MI). METHODS AND RESULTS: Twenty-nine patients with acute MI and early percutaneous transluminal coronary angioplasty (PTCA) were included in this study. A rest Tc-99m sestamibi electrocardiography (ECG)-gated SPECT study was performed 21 +/- 5 days after PTCA. The myocardial perfusion index was calculated by use of a semiautomatic sectorial analysis. All patients had contrast ventriculography performed during the acute phase and 6 months later. The patients were separated into two groups according to the absence (group I, n = 21) or presence (group II, n = 8) of end-systolic enlargement. The perfusion index in the infarct sectors was -2.29 +/- 2.90 SD in group I and -6.40 +/- 2.85 SD in group II ( P < .01). With a cutoff value of -2.46 SD, the sensitivity and specificity of Tc-99m sestamibi SPECT for the prediction of end-systolic volume enlargement were 100% and 62%, respectively. When the functional data from ECG-gated acquisitions were added, specificity increased to 86%. CONCLUSIONS: Despite successful PTCA in the acute phase of MI, an increase in end-systolic volume was observed at 6 months in 28% of patients. Tc-99m sestamibi ECG-gated SPECT performed 3 weeks after the acute phase could predict this enlargement with a high accuracy.     

Estimation with Tc-99m tetrofosmin SPECT of salvaged myocardial mass after emergent reperfusion therapy in acute myocardial infarction

OBJECTIVES: The purpose of this study was to validate a new quantitative index of salvaged myocardial mass calculated from Tc-99m tetrofosmin SPECT for evaluating the therapeutic effect of emergent reperfusion therapy in acute myocardial infarction (AMI). METHODS: Tc-99m tetrofosmin SPECT was performed before and after emergent percutaneous transluminal coronary angioplasty (PTCA) in eight patients with AMI. In the pre-PTCA study, Tc-99m tetrofosmin was injected before emergent PTCA. Two weeks after the PTCA, post-PTCA study was performed. As a quantitative index of salvaged myocardial mass, salvaged myocardial volume (SMV) was defined as the difference of myocardial functional volume between the SPECT studies before and after the PTCA. To investigate the clinical significance of SMV, SMV was compared with the grade of therapeutic efficacy determined visually from pre- and post-PTCA SPECT images and clinical parameters, namely peak creatine phosphokinase level (pCK) and the time from the onset of the AMI to reperfusion (RPT). RESULTS: SMV showed a significant correlation with the visual grade of therapeutic efficacy (r = 0.737, p < 0.037) and a trend toward significant correlation with pCK (r = -0.622, p < 0.1). SMVs in early- and late-reperfusion groups (RPT < or = 6 hr and RPT > 6 hr) were 30.0 +/- 14.0 and -6.2 +/- 25.5 ml, showing a greater mean SMV value in the early-reperfusion group (p < 0.07). CONCLUSION: SMV could be used as a quantitative index of salvaged myocardial mass for evaluating the therapeutic effect of emergent reperfusion therapy.     

Restenosis after percutaneous transluminal coronary angioplasty.

Restenosis after percutaneous transluminal coronary angioplasty was demonstrated in 61 (29%) of 210 successfully treated patients. Mostly it occurred within 4 months after treatment and in arteries less than 3 mm in diameter. Careful clinical follow-up is therefore particularly important early after angioplasty of smaller arteries. Redilation can be performed without increased risk of restenosis.     

The value of Tc-99m MIBI SPECT during isosorbide dinitrate infusion in assessment of viable myocardium in patients with myocardial infarction

Tc-99m MIBI myocardial SPECT has shown promise for evaluation of coronary artery disease. But its role in predicting myocardial viability is still under investigation. The purpose of this study was to evaluate the value of Tc-99m MIBI myocardial SPECT during isosorbide dinitrate (ISDN) infusion in the assessment of myocardial viability. Thirty-seven patients with previous myocardial infarction (the infarct age ranged from ≤ 30 days to 900 days) were studied, of them 13 patients had Tc-99m MIBI studies before and after coronary artery bypass grafting (CABG). The results showed that out of 134 segments with hypoperfusion at resting SPECT, 56 segments (41.8%) had an increase in Tc-99m MIBI uptake during ISDN infusion. Among them, 17 segments (30.4%) were normalized, 6 segments (10.7%) were significantly improved and 33 segments (58.9%) were improved. The degree of improvement in perfusion was related to the age of the myocardial infarction. In 13 patients with CABG, of 31 segments with improvement in perfusion post CABG, 25 segments (80.6%) showed perfusion improvement during ISDN infusion, and of 28 segments with improved wall motion post CABG, 23 segments (82.1 %) showed improvement in perfusion during ISDN infusion. Tc-99m MIBI SPECT during ISDN infusion may therefore be a useful approach for assessing myocardial viability.     

Ectopic parathyroid adenoma with Tc-99m MIBI washout: role of SPECT

The authors present a case of a 71-year-old woman with clinical and biochemical features of primary hyperparathyroidism and a history of right pneumonectomy. An ultrasound scan did not demonstrate any abnormality. A planar Tc-99m methoxyisobutylisonitrile (Tc-99m MIBI) scan showed an area of minimally increased uptake within the right hemithorax. However, unlike most adenomas, this demonstrated washout similar to the thyroid at 90 minutes and 3 hours. Subsequent SPECT imaging clearly showed the lesion in the superior right hemithorax. A CT scan and angiogram confirmed the presence of this mass. After surgery, histology confirmed the diagnosis of a parathyroid adenoma. Postoperatively, the calcium and PTH levels returned to normal.     

Noninvasive assessment of coronary microvascular dysfunction using Tc-99m tetrofosmin SPECT in patients with acute myocardial infarction

BACKGROUND: We investigated whether technetium 99m tetrofosmin (TF) single photon emission computed tomography (SPECT) could predict coronary microvascular dysfunction in patients with acute myocardial infarction. METHODS AND RESULTS: We obtained the regional severity score index (TF-RSSI) using TF SPECT immediately after percutaneous coronary intervention in 25 patients with acute myocardial infarction. Using a Doppler guidewire, we evaluated the deceleration time of diastolic flow velocity (DDT) after percutaneous coronary intervention, and DDT of 600 milliseconds or less was suggested to be an indicator of coronary microvascular dysfunction. Moreover, the chronic regional wall motion score index (RWMSI) was obtained from echocardiography during the chronic phase. There was a good correlation between TF-RSSI and DDT (r = -0.68, P < .01). The optimal cutoff value of TF-RSSI to predict DDT of 600 milliseconds or less was defined as 1.9 or greater (sensitivity, 1.00; specificity, 0.71). The group with poor scintigraphic coronary microvascular function (TF-RSSI > or =1.9, n = 7) demonstrated a significantly shorter DDT (P = .0003), a lower frequency of early systolic retrograde flow (P = .0038), and greater chronic RWMSI (P = .0015) than the group with good scintigraphic coronary microvascular function (TF-RSSI <1.9, n = 15). CONCLUSIONS: Analysis of TF SPECT immediately after percutaneous coronary intervention in patients with acute myocardial infarction is a useful noninvasive method for evaluating coronary microvascular dysfunction.     

Tc-99m MIBI imaging in malignant fibrous histiocytoma

The authors report a case of malignant fibrous histiocytoma of the left forearm demonstrated by Tc-99m MIBI imaging. The tumor originated in the soft tissue of the forearm; no obvious bone invasion or metastasis was detected scintigraphically or radiologically.     

Tc-99m tetrofosmin myocardial perfusion SPECT after dipyridamole combined with low-level exercise in the diagnosis of coronary artery disease

Tc-99m tetrofosmin is a lipophilic, cationic perfusion imaging agent that changes to Tl-201 in detecting coronary artery disease during exercise testing. The purpose of this study is to evaluate the usefulness of Tc-99m tetrofosmin dipyridamole stress imaging combined with low level exercise for the detection of coronary artery disease. We examined 42 patients and 10 normal volunteers who also underwent coronary angiography. A one-day protocol was used: in the stress study, 296 MBq of tetrofosmin was injected and in the rest study 888 MBq was injected. After intravenous administration of dipyridamole (0.142 mg/kg/min for 4 minutes), the patient was exercised on a bicycle ergometer for 3 min (25 Watts). Tetrofosmin was injected 2 minutes after dipyridamole infusion during the exercise. Single photon emission computed tomographic images were obtained 30 minutes after the tracer injection. Images were interpreted as abnormal in 36 of 42 patients with coronary artery disease, and normal in all of 10 normal volunteers. The overall sensitivity of detection of coronary artery disease was 83.3% and the normalcy rate was 100%. The diagnostic values for the detection of significant stenosis in the three major arteries were: LAD sensitivity 83%, specificity 92%; LCX sensitivity 47%, specificity 91%; RCA sensitivity 75%, specificity 83%. Of the 66 arteries with more than 50% stenosis, 48 arteries were correctly identified. Of the 36 with more than 70% stenosis, 31 were identified. Scintigraphic evidence of multivessel disease was found in only 9 patients (50%). A protocol of Tc-99m tetrofosmin SPECT combined with low level exercise after dipyridamole is therefore useful for the detection of the coronary artery disease.     

Simultaneous assessment of right ventricular function and hypertrophy by Tc-99m MIBI

PURPOSE: Tc-99m MIBI allows the simultaneous performance of cardiac blood pool scintigraphy and myocardial SPECT. The authors performed studies to determine whether right ventricular function and hypertrophy can be evaluated simultaneously using Tc-99m MIBI in patients with right heart disease. METHODS: Using right heart catheterization, several parameters of pulmonary circulation were measured, including right ventricular ejection fraction, in 23 patients with chronic pulmonary disease and pulmonary vascular disease. Within 1 week, right heart blood pool scintigraphy was performed using the first-pass method using Tc-99m MIBI. The right ventricular ejection fraction calculated from right heart blood pool scintigraphy was compared with that measured using right heart catheterization. Myocardial SPECT was performed 1 hour after right heart blood pool scintigraphy. On the short axis images, which allowed optimal visualization of the right ventricle, the right and left ventricular free walls were established as regions of interest. Myocardial wall counts were determined. The right ventricular uptake: left ventricular uptake ratio was calculated to study the relation of that ratio to mean pulmonary artery pressure and total pulmonary resistance. RESULTS: A significant correlation was observed between the right ventricular ejection fraction calculated on right heart catheterization and that calculated on right heart blood pool scintigraphy. The right ventricular uptake:left ventricular uptake ratio correlated positively with pulmonary artery pressure and total pulmonary resistance. CONCLUSION: These results suggest that Tc-99m MIBI allows simultaneous noninvasive evaluation of cardiac function and structure, which previously was considered impossible in patients with right heart disease.     

Tc-99m MIBI SPECT in prediction of prognosis in patients with small cell lung cancer

PURPOSE: The purpose of this study was to evaluate whether the degree of technetium-99m methoxyisobutylisonitrile (MIBI) uptake and its retention in delayed imaging in small cell lung cancer (SCLC) was correlated with the response to multiagent chemotherapy and to investigate if there was a relationship between the survival time of patients with SCLC and Tc-99m MIBI SPECT tumor uptake parameters at the time of diagnosis. METHODS: Between 1998 and by December 2004, 40 patients with SCLC were studied with Tc-99m MIBI SPECT at the time of diagnosis. The patients were classified by a follow-up CT as good responders (complete or partial remission) and poor responders (stable disease or progressive disease). Following i.v. administration of 740 MBq Tc-99m MIBI, SPECT imaging at 30 minutes (early) and 2 hours (delayed) was performed. Regions of interests were placed over the tumors and contralateral normal lung tissue on one transverse section. The uptake ratio of the lesion to that in the contralateral normal lung was obtained from early images (early ratio; ER) as well as delayed images (delayed ratio; DR). The retention index (RI%) was measured as: RI% = [(DR-ER)/ER] x 100. Tc-99m MIBI tumor uptake parameters were compared with chemotherapeutic response and survival time. RESULTS: Of 40 patients, 29 patients were good responders (72.5%) and 11 patients were poor responders (27.5%). RI% of Tc-99m MIBI SPECT in the group of good response was significantly higher than in that with poor response (p < 0.05). On the other hand, there was no significant difference between the two groups with respect to ER or DR values. Four of 40 patients were still alive with disease (10%). The patient survival time varied from 1 to 70 months (mean survival time = 12.9 +/- 13.4 months). There was no significant difference between the survival time of patients with respect to ER or DR of Tc-99m MIBI SPECT imaging. When median RI% was accepted as a cut-off value (-3.85%), patients with higher RI% values had a longer survival time (12 months) when compared with those with low RI% (8 months), p < 0.05. CONCLUSION: Our results suggest that Tc-99m MIBI SPECT could accurately predict the chemotherapy response in patients with SCLC. RI% of Tc-99m MIBI SPECT is recommended to differentiate patients with a poor response to chemotherapy and good responders, and RI% of Tc-99m MIBI SPECT appears as the only parameter that may be useful in predicting the survival of patients with SCLC.     

A trial for the quantification of regional myocardial blood flow with continuous infusion of Tc-99m MIBI and dynamic SPECT

We propose a new method to quantify regional myocardial blood flow (rMBF) by continuous infusion of Tc-99m MIBI and dynamic SPECT. METHODS: Five patients with old myocardial infarction were studied. During continuous infusion of MIBI (approximately 740 MBq) with a syringe pump in 10 min, dynamic SPECT scan was performed every minute and lasted 20 min after the start of infusion to identify myocardial uptake of MIBI. Input function was obtained from the radioactivity in the left ventricle (LV) in dynamic SPECT images. Spillover fraction between LV and myocardium (M) was corrected with phantom data. The influx constant (Ku) was calculated by Patlak plot graphical analysis, and compared with rMBF measured by PET (F) with N-13 ammonia based on Patlak plot analysis with correction for the extraction fraction. To correct the limited first-pass extraction of MIBI, linearization correction by means of the permeability-surface area (PS) product value was also applied. RESULTS: Spillover fractions of MIBI were 0.169+/-0.056 from LV to M, and 0.042+/-0.021 from M to LV. Ku was well correlated with F (Ku = 0.057 + 0.220F, r = 0.83, p < 0.01) and the slope and correlation were improved after linearizaiton (F(MIBI) = -0.131+0.858F, r = 0.94, p < 0.01). CONCLUSION: The proposed method has the potential to be a clinically feasible tool for quantitative measurement of rMBF.     

Visualization of suppressed thyroid tissue by Tc-99m MIBI.

The authors describe a case of suppressed normal thyroid tissue in a patient with autonomous toxic nodule, which was visualized by a Tc-99m MIBI thyroid scan without thyrotropin (TSH) stimulation. The findings suggest that Tc-99m MIBI can be a substitute for conventional thyroid imaging using I-131 to visualize suppressed normal thyroid tissue without TSH stimulation and its side effects.     

Comparison of Tc-99m HMPAO fast SPECT with Tc-99m HMPAO conventional SPECT in patients with acute stroke.

Tc-99m HMPAO SPECT is more likely to detect a stroke in early stages than CT. However, a conventional HMPAO SPECT study takes at least 30 minutes to complete. This paper compares fast Tc-99m HMPAO SPECT scans and conventional Tc-99m HMPAO SPECT scans with respect to spatial resolution and diagnostic efficacy in vitro and in a small series of patients, respectively. The spatial resolution of fast Tc-99m HMPAO SPECT did not match that of images obtained from conventional SPECT, though the difference proved to be of no clinical significance. Since fast SPECT requires only one-fourth to one-fifth the time necessary for conventional SPECT, it may be more suitable for investigating cases of acute stroke in critical clinical situations.     

Clinical significance of reverse redistribution in exercise thallium-201 SPECT after percutaneous transluminal coronary angioplasty

Clinical significance of reverse redistribution on thallium image was evaluated in 54 patients who had undergone PTCA. Thallium SPECT imaging was performed one week and three to six months after PTCA. Reverse redistribution was detected eight of 54 patients one week after PTCA and five of 38 patients three to six months after PTCA. In the segments with reverse redistribution, reduced regional wall motion and lesser degree of coronary stenosis was common features (p less than 0.05) angiography. In conclusion, reverse redistribution had a tendency to appear in the region with mild myocardial injury and relatively high coronary blood flow after PTCA. But in cases with new occurrence and disappearance of reverse redistribution during follow up period, we can not assess the factors to explain these phenomena. In these segments, "coronary flow reserve", "stunned myocardium", "hibernating myocardium" or other factors may be related.     

Focal pulmonary uptake during Tc-99m myocardial perfusion SPECT imaging

PURPOSE: To evaluate the incidence and origin of abnormal focal pulmonary uptake during myocardial perfusion SPECT imaging (MSPECT). METHODS: For evaluation of chest pain, 790 men and 581 women (mean age, 56 +/- 13 years) underwent MSPECT. All of them received adenosine for pharmacologic stress and Tc-99m tetrofosmin (TF, n = 817) or Tc-99m sestamibi (MIBI, n = 554) for myocardial perfusion imaging. RESULTS: Review of chest radiography with or without computed tomography revealed 111 (8.1%) focal pulmonary diseases. Among them, 38 (34.2%) showed focal pulmonary uptake (TF, 22; MIBI, 16); 27 (30.7%) of 88 showed previous pulmonary tuberculosis; 2 of 10 (20%) benign pulmonary nodules; 4 of 5 (80%) metastatic lung cancers; 2 of 4 (50%) primary lung cancers; and 3 of 4 (75%) pneumonias. No difference in uptake was noted for the two imaging agents. Intensity of uptake did not vary with origin of the uptake. Focal abnormal pulmonary uptake was found in 2.8% of patients undergoing MSPECT and in 34.2% of patients in whom radiological examinations showed regional pulmonary disease. In patients with abnormal pulmonary uptake on MSPECT, 16% had a malignant lesion, whereas 75% of patients with a pulmonary nodule shown on radiography and focal pulmonary uptake on MSPECT had a malignant lesion. CONCLUSIONS: Although the incidence of abnormal pulmonary uptake during MSPECT was very low, the incidence of malignant lesions in the patients with nodular pulmonary uptake was relatively high.