Evaluation of radiopharmaceuticals for the detection of acute myocardial infarction in man.

The accuracy of the scintigraphic diagnosis of acute myocardial infarction with 99mTc-pyrophosphate, 99mTc-tetracycline and 99mTc-glucoheptonate was assessed in 63 patients, 43 of whom had clinical evidence of acute myocardial infarction. In 15, studies with both 99mTc-tetracycline and 99mTc-pyrophosphate were performed. Accuracy was greatest with 99mTc-pyrophosphate (17/17 true positives, 8/10 true negatives) contrasted with 99mTc-tetracycline (12/25 true positives, 6/11 true negatives) and 99mTc-glucoheptonate (3/13 true positives, 2/2 true negatives). 99mTc-pyrophosphate was the most sensitive tracer for the detection of acute myocardial infarction. The diagnostic accuracy with 99mTc-glucoheptonate was poor.     

Clinical evaluation of 99mTc-pyrophosphate myocardial emission computed tomography: comparison with planar imaging

To depict the three-dimensional distribution of 99mTc-pyrophosphate in the heart, emission computed tomography (ECT) was performed, following the conventional planar imaging, in 32 cases with suspected acute myocardial infarction (AMI). There were 23 cases with evidence of AMI, 7 with unstable angina (UA), and 2 with dilated cardiomyopathy (DCM). While the planar images showed discrete cardiac activity in only 11 of the 23 cases (48%) with AMI, the ECT images delineated focal myocardial uptake clearly in 20 of them (87%). On the other hand, the ECT images revealed cardiac blood-pool activity without significant myocardial uptake in all cases with UA and DCM in which the planar images showed diffuse activity. Thus, the ECT imaging of 99mTc-pyrophosphate seems to be a valuable technique for assessing the presence and localization of myocardial necrosis, especially in cases showing diffuse cardiac activity in the planar imaging.     

Radiation-induced inhibition of compensatory renal growth in the weanling mouse kidney

Four-hour balloon occlusion of the cranial mesenteric artery in 13 dogs produced a spectrum of widespread ischemic injury to the small bowel ranging from superficial mucosal infarction to transmural infarction. Twenty-four hours after the beginning of balloon occlusion, 15 mCl of 99mTc-pyrophosphate was injected into the cranial mesenteric artery in 8 dogs and into a peripheral vein in 5. Gamma camera imaging of the abdomen followed three hours later. Four of 8 dogs injected intra-arterially showed positive images with full-thickness mucosal or transmural infarction. The 4 intravenously injected dogs with positive images had transmural infarction. Only minimal ischemic injury with superficial mucosal infarction was found in the 5 dogs with negative images. Tracer uptake per gram infarcted tissue was highest after intra-arterial injection. It was concluded that 99mTc-pyrophosphate allows external imaging of extensive intestinal infarctions after both intra-arterial and intravenous injection.     

Acute myocardial infarction imaged with 99mTc-stannous pyrophosphate and 201Tl: a clinical evaluation.

Twenty-six patients suspected of having acute myocardial infarction (AMI) underwent myocardial scintigraphy sequentially with 201Tl and 99mTc-stannous pyrophosphate (99mTc-PPi). Of the 26 patients, 24 had AMI documented by enzyme and electrocardiographic changes. Nineteen had transmural and five had subendocardial myocardial infarctions. The remaining two patients had "unstable angina pectoris." The mean time from onset to imaging was 4 days. Of the 24 patients with AMI, 22 had positive 99mTc-PPi scintigrams. In 20 the area of acute myocardial damage appeared to be the same by 99mTc-PPi scintigram as by ECG; in two, the location could not be precisely determined. The two patients with negative 99mTc-PPi scintigrams at the time of combined myocardial imaging had had positive 99mTc-PPi images previously. In all 24 patients, the 201Tl images were abnormal in at least the location suggested by the electrocardiogram. In seven patients, the area of decreased 201Tl activity was grossly equal to the positive area on the 99mTc-PPi images; in 15, the 201Tl defect was definitely larger; and in two, the 201Tl defect appeared slightly smaller. Although the 99mTc-PPi and 201Tl myocardial images provide different information, both are valuable in determining the overall integrity of the myocardium in patients with ischemic heart disease.     

99Tcm标记化合物显像检测冠心病的优化方案探讨

目的 探讨99Tcm标记化合物显像检测冠心病的优化方案.方法 选择临床可疑或确诊的冠心病患者4236例,进行99Tcm标记化合物显像8873例次,分析显像结果,提出99Tcm标记化合物显像检测冠心病的优化方案,并与临床资料对照验证.结果 在可疑冠心病诊断、心肌缺血检测、心肌梗死诊断中,该方案准确率高达94.1%.对临床特需的诊断要求如存活心肌检测、 "罪犯"血管检测、缺血性心肌病诊断、疗效监测等也有较高的准确率.结论 99Tcm标记化合物显像优化方案可以完成临床对冠心病的大部分诊断要求,克服了核素显像自身的部分缺陷,具有高效、简便、节约的优势,临床指导价值显著.     

Kinetics of Tc-99m hexakis t-butyl isonitrile in normal and ischemic canine myocardium

Hexakis 99mTc-tertiary butyl isonitrile (99mTc-TBI) was studied as a cardiac perfusion imaging agent in nine dogs with partial occlusion of the LAD. Thirty min after applying the stenosis, 99mTc-TBI was injected into the right atrium (RA) in five dogs and left atrium (LA) in four dogs. Normal and ischemic zone regional myocardial 99mTc-TBI activities were monitored continuously for 4 h. Dogs with LA injections had minimal and equivalent 4 h fractional clearance from the normal and ischemic zones. Dogs with RA injections had minimal, but significantly lower 4 h fractional 99mTc clearances in the ischemic zone (0.08 +/- 0.08) compared to the normal zone (0.16 +/- 0.07, P less than 0.05). The delayed ischemic zone clearance is probably due to the high initial lung uptake observed after RA injection. Despite the differences in clearance, this minimal amount of redistribution could not be detected on gamma camera images. The minimal myocardial washout and redistribution, and the 140 keV gamma make 99mTc-TBI a promising cardiac perfusion imaging agent.     

Comparison of technetium-99m-glucarate and thallium-201 for the identification of acute myocardial infarction in rats.

The scintigraphic identification of acute severe ischemic myocardial injury requires a marker that localizes rapidly and specifically in zones of damaged myocardium. Technetium-99m-glucarate, a six-carbon dicarboxylic acid, which behaves in vivo somewhat like fructose, was recently described as a marker of severe acute ischemic injury with necrosis. This study was performed to determine the interval between the onset of myocardial ischemia and initial uptake and the duration of a positive scan in experimental animals. Serial injections and images were recorded over 10 days following ligation of the left anterior descending coronary artery of the rat. The distribution of 99mTc-glucarate was compared to that of regional myocardial perfusion monitored with 201TI. The findings on radionuclide imaging were compared to histologic changes in the myocardium. Sequential pinhole images of both radionuclides were collected at 3 hr, 24 hr, 72 hr and 7-10 days following ligation. Ten rats had normal 201TI distributions, no uptake of glucarate and no evidence of infarction by TTC staining at autopsy. Twenty-one rats had either 201TI lesions or evidence of infarction at autopsy. In 17 of these rats, significant acute 99mTc-glucarate uptake was noted, decreasing at 24 hr, and was not seen at 72 hr or 7-10 days. The extent of perfusion abnormality was greatest at 3 hr in most animals; the lesion decreased in four (33%), increased in one (8%) and remained stable in the remainder. These data suggest that 99mTc-glucarate may be a useful marker of acute myocardial injury.     

Diagnosis of acute myocardial infarction in patients undergoing open heart surgery: a comparison of serial myocardial imaging with cardiac enzymes, electrocardiography, and vectorcardiography.

In 44 consecutive patients undergoing elective open heart surgery (OHS), serial electrocardiograms (ECG), vectorcardiograms (VCG), serum CPK, cardiac isoenzymes (CPKMB), and myocardial images using Tc-99m pyrophosphate were obtained, before and after the operation, for the detection of acute myocardial infarction (AMI). Twenty-nine patients developed one or more positive tests postoperatively. Two patients had positive myocardial scintiscans; both had other evidence of infarction. Conversely, the appearance of CPKMB, or new ECG and VCG changes, occurred frequently without evidence of infarction, and were not associated with the development of a positive scintiscan. The results show that false-negative results are infrequent in patients imaged early after OHS, and that cardiac surgical procedures do not cause a high incidence of false-positive scintigrams. Consequently, radionuclide imaging for AMI offers an important adjunct for excluding acute infarction following open heart surgery.     

Technetium-99m-sestamibi myocardial perfusion imaging in detection of coronary artery disease: comparison between initial (1-hour) and delayed (3-hour) postexercise images.

Technetium-99m-sestamibi, a new myocardial perfusion imaging agent, does not show significant or rapid myocardial redistribution following its intravenous injection at stress. The purpose of this study was to evaluate the myocardial clearance of 99mTc-sestamibi and ischemic/normal wall ratios at 1 hr and at 3 hr after injection at stress in patients with significant coronary artery disease. Twenty-five patients with ischemic defects on 201Tl scans (n = 15) and/or significant disease on coronary angiogram (n = 18) were prospectively studied. Planar images were obtained at 65 and at 190 min after an injection at stress of 20-25 mCi of 99mTc-sestamibi. A rest study was performed 1-6 days later. Ischemic/normal wall ratios were 0.73 +/- 0.10 and 0.83 +/- 0.12 (p less than 0.05) at 1 and 3 hr, respectively (0.98 +/- 0.15 at rest). Myocardial washout was 26% +/- 12% for normal walls and 15% +/- 8% for ischemic walls (p less than 0.001). Segmental analysis showed 48 and 46 ischemic segments at 1 and 3 hr, respectively. In conclusion, although only a few ischemic segments were missed at 3 hr, significantly lower ischemic/normal wall ratios were found at 1 hr. Faster myocardial washout from normal walls is responsible for the partial reduction of this ratio.     

核素显像在阴囊急症的临床应用价值

目的 探讨放射性核素阴囊显像在急性睾丸扭转与急性睾丸附睾炎鉴别诊断中的临床应用价值。方法 对阴囊急症13例行SPECT核素阴囊显像，“弹丸”注射^99mTcO^-4 370 MBq后即刻行动态血流灌注显像，15min后行静态血池显像并进行显像结果分析。结果 10例血流灌注相呈血流减低，静态血池相放射性缺损，经急诊手术证实了9例为睾丸扭转，其中3例因及时确诊及手术纠正扭转而保留患睾。3例血流灌注相呈血流增高，静态血池相放射性分布仍明显高于对侧，符合睾丸附睾炎表现．经内科保守治疗后症状消失。结论 睾丸缺血的时间是影响其存活的重要因素。核素阴囊显像简便、快速、非创伤，对阴囊急症的鉴别诊断、治疗方法的选择具有重要的临床指导价值。     

Proton nuclear magnetic resonance imaging of regionally ischemic canine hearts: effect of paramagnetic proton signal enhancement

In a study to evaluate the potential of proton nuclear magnetic resonance (NMR) imaging with and without manganese contrast with and without manganese contrast enhancement for detecting acute myocardial infarction, 12 dogs underwent 90-minute occlusion of the left circumflex coronary artery. Transverse-section NMR images of the excised, nonbeating heart were obtained at 1-cm intervals using the steady-state-free-precession (SSFP) technique. All NMR images revealed detailed structure of the heart. The three hearts without manganese showed no difference in intensity between the normal and the ischemic posterior regions, whereas those with manganese demonstrated a clearly demarcated zone of reduced signal intensity consistent with the ischemic zone. It is concluded that high-resolution tomograms of the excised canine myocardium can be obtained using proton NMR imaging. With the SSFP imaging technique, proton signal enhancement with manganese infusion is necessary to differentiate between ischemic and nonischemic myocardium after 90 minutes of coronary occlusion.     

Myocardial clearance of Tc-99m hexakis-2-methoxy-2-methylpropyl isonitrile (MIBI) in patients with coronary artery disease

Myocardial clearance of the new cationic, lypophilic myocardial perfusion agent, Tc-99m-hexakis-2-methoxy-2-methylpropyl isonitrile (MIBI) was studied in nine patients with coronary artery disease. Regional time-activity curves were determined from serial postexercise myocardial SPECT images after a single dose of Tc-99m MIBI. There were significant differences between the clearance rates from normal and ischemic myocardium. Tc-99m MIBI washout from normal myocardium was 27 +/- 8% by 6 hours after injection. Clearance from mild myocardial defects (initial activity greater than 60% of the activity in normal myocardium) was 16% by 6 hours in six patients. No washout was detected by 6 hours in the three patients with severe myocardial defects. The ratio between the activity in ischemic and normal myocardium increased from 0.70 +/- 0.08 to 0.80 +/- 0.13 and 0.84 +/- 0.13 at 4 and 6 hours after injection in the patients with mild defects. In the patients with large defects, the ratio increased from 0.42 +/- 0.09 to 0.54 +/- 0.07 at 6 hours. It is concluded that, while redistribution is substantially slower than with Tl-201, image interpretation and data evaluation should be approached cautiously when imaging is delayed 4 hours or more after injection of Tc-99m MIBI. Quantitative techniques aimed at evaluating the extent and intensity of myocardial ischemia will be particularly affected.     

Aortic aneurysm detected by 99mTc-pyrophosphate imaging: case report.

An example of aneurysmal concentration of 99mTc-pyrophosphate (Tc-PPi) is described. An abdominal aortic aneurysm was suspected when a rectilinear bone scan showed an abnormal paraspinal area of activity. The aneurysm was confirmed by ultrasonic examination. Conventional radiographic examination failed to reveal calcification within the aneurysm. Aneurysmal concentration of Tc-PPi should be considered in patients showing abnormal radioactivity in the region of vascular structures on radionuclide bone images.     

Reliability of technetium-99m Q12 and thallium-201 myocardial activity measurements after triphenyl tetrazolium chloride myocardial staining by perfusion

RATIONALE AND OBJECTIVES: Investigations in animal models of severe myocardial ischemia or infarction use triphenyl tetrazolium chloride (TTC) staining to document infarction size histologically and to correlate these data with uptake measurements of radiolabeled tracers. Previously published data suggest that TTC staining itself has an important impact on myocardial tracer activity measurements. The authors hypothesized that TTC staining by perfusion has no significant effect on relative regional myocardial activity measurements of technetium-99m Q12 and thallium-201 in an open-chest canine model. METHODS: Eight dogs underwent left anterior descending artery occlusion for 2 hours with 30 minutes of reperfusion, followed immediately by injection of technetium-99m Q12 (n = 4) or thallium-201. Total myocardial activity was recorded in a dose calibrator, and regional myocardial samples were obtained by Cope needle biopsies from the ischemic and normal zones, both before and after TTC staining. RESULTS: The mean percent activity retention for the whole heart after perfusion staining with TTC was significantly reduced when compared to the preperfusion value for both technetium-99m Q12 and thallium-201. Regional measurements revealed no significant difference between the mean percent retention of technetium-99m Q12 in the ischemic and normal zones. After TTC perfusion, regional mean percent retention of thallium-201 was similar in the ischemic and normal zones. CONCLUSIONS: In a canine model of myocardial ischemia and infarction with reperfusion, TTC staining can be performed by coronary artery perfusion without significantly affecting comparative regional measurements of either technetium-99m Q12 or thallium-201. Whole heart tracer retention is significantly reduced by TTC perfusion staining, but thallium-201 is more affected than technetium-99m Q12.     

Diagnostic accuracy of coronary artery lesion by 99mTc-MIBI exercise myocardial scintigraphy--containing the utility of simultaneous assessment of left ventricular function]

To determine whether technetium-99m hexakis-2-methoxy isobutyl isonitrile (99mTc-MIBI) myocardial scintigraphy is a superior method in the detection of coronary artery disease, exercise and rest 99mTc-MIBI planar and SPECT scintigraphy were performed on 27 patients with coronary artery disease. When 99mTc-MIBI (555 MBq (15 mCi)) was injected, first-pass radionuclide angiography (FPRNA) was simultaneously performed by a new mobile multicrystal gamma camera (SIM-400), and LV function (LVEF) was evaluated quantitatively. Visual semiquantitative detection of coronary lesions using 99mTc-MIBI images showed superior accuracy to that obtained using 201TlCl images. 99mTc-MIBI SPECT images were particularly useful in diagnosing LCX and RCA lesions. Moreover, the simultaneous assessment of perfusion and left ventricular function by 99mTc-MIBI FPRNA proved to be useful in the diagnosis of multi-vessel disease. In summary, 99mTc-MIBI SPECT scintigraphy with simultaneous assessment of left ventricular function showed better diagnostic accuracy than 201TlCl myocardial scintigraphy.     

Improvement of 99mTc-pyrophosphate scintigraphy in detection of acute myocardial infarction: combined with 99mTc-tetrofosmin]

BACKGROUND: 201Tl and 99mTc-pyrophosphate (PYP) dual scintigraphy is daily used in the detection of acute myocardial infarction (AMI). However, 201Tl is not available on emergent situation. We proposed a new method for detection of AMI combined 99mTc-PYP with 99mTc-tetrofosmin (TF). METHODS: 99mTc-PYP (740 MBq) was administered to 25 patients with AMI, and 3.5 hours later, planar imaging (PYP planar) and SPECT were performed (PYP-SPECT). Immediately after cessation of PYP-SPECT, 99mTc-TF (370-740 MBq) was injected and 5 minutes later SPECT was performed in the same position (TF-SPECT). PYP-SPECT and TF-SPECT were reconstructed in the same geometric status to permit superimpose of PYP-SPECT and TF-SPECT images. Two experts and 2 beginners of nuclear medicine physician interpreted the images in three ways; PYP planar image only, PYP-SPECT, and PYP-SPECT with TF-SPECT. RESULTS: PYP-SPECT combined with TF-SPECT shows 100% detectability of the AMI lesions, which is significantly higher than other two methods in both experts and beginners. CONCLUSION: PYP-SPECT combined with TF-SPECT is a powerful method for detection of AMI.     

Early imaging of experimental intestinal infarction with 99mTc-pyrophosphate.

Extensive mucosal small-bowel infarction was produced in 8 dogs by occluding the cranial mesenteric artery. After one hour of reperfusion, 15 mCi (555 MBq) of 99mTc-pyrophosphate was intra-arterially injected into 4 dogs and venously into the other 4. Positive images were obtained in all dogs except 1 which had received an intravenous injection. Diagnostic images were obtained consistently as early as 15 minutes after injection, and the infarcted bowel could still be visualized two hours later. The average tracer content in infarcted small bowel was 0.015% I.D./g. This was about eight times the uptake found in normal dogs. The results show that experimental small-bowel infarction can be detected as early as five hours after the onset of ischemia.     

Kinetics of Tc-99m hexakis t-butyl isonitrile in normal and ischemic canine myocardium

Hexakis ^99mTc-tertiary butyl isonitrile (^99mTc-TBI) was studied as a cardiac perfusion imaging agent in nine dogs with partial occlusion of the LAD. Thirty min after applying the stenosis, ^99mTc-TBI was injected into the right atrium (RA) in five dogs and left atrium (LA) in four dogs. Normal and ischemic zone regional myocardial ^99mTc-TBI activites were monitored continuously for 4 h. Dogs with LA injections had minimal and equivalent 4 h fractional clearance from the normal and ischemic zones. Dogs with RA injections had minimal, but significantly lower 4 h fractional ^99mTc clearances in the ischemic zone (0.08±0.08) compared to the normal zone (0.16±0.07, P<0.05). The delayed ischemic zone clearance is probably due to the high initial lung uptake observed after RA injection. Despite the differences in clearance, this minimal amount of redistribution could not be detected on gamma camera images. The minimal myocardial washout and redistribution, and the 140 keV gamma make ^99mTc-TBI a promising cardiac perfusion imaging agent.Dr. Okada is an Established Investigator of the American Heart Association     

99Tcm-HL91 SPECT探测缺血存活心肌的初步应用研究

目的 研究99Tcm-4,9-二氮-3,3,10,10-四甲基十二烷-2,11-二酮肟(99Tcm-HL91)在缺血心肌中的显像表现,探讨99Tcm-HL91探测缺血但存活心肌的价值.方法 18例已确诊为心肌缺血或心肌梗死的患者均行99Tcm-甲氧基异丁基异腈(99Tcm-MIBI)与99Tcm-HL91心肌灌注显像.在心脏短轴图像上通过感兴趣区技术获取缺血区与正常心肌组织的平均放射性计数,获得99Tcm-MIBI与99Tcm-HL91在局部缺血区与正常心肌组织的放射性比值.结果 10例患者在99Tcm-MIBI显像的放射性稀疏或缺损区而在99Tcm-HL91 SPECT可见到明显的放射性充填;其余8例患者99Tcm-HL91显像心肌摄取不高.结论 99Tcm-HL91可选择性地被存活乏氧心肌摄取,与99Tcm-MIBI SPECT联合应用,可望有效提高检测存活心肌的效能.     

Scintigraphic imaging of the heart in dogs damaged by irradiation

The paper verified literature data assuming that the heart damage caused by irradiation of thorax may be scintigraphically detected by means of 99mTc-pyrophosphate. Three dogs underwent a single irradiation of thorax with a gamma cobalt source by the Dose 40 Gy. The myocardium scan was performed 24 hours, 20 days, 50 days, 80 days and 93 days after the irradiation. The scintigraphic examination proved to be negative at all the intervals observed. A comparison of the scan with morphological findings and with radioactivity of tissue samples after the dogs were sacrificed 93 days after the irradiation proved that the negativity of the pyrophosphate scintigraphy was caused by a minimum damage of the myocardium and not by an inability of 99mTc-pyrophosphate to be incorporated into radiation lesions. The data in literature on myocardium damage by irradiation appear to be considerably exaggerated.