Detection of moderate and severe coronary artery stenosis with technetium-99m tetrofosmin myocardial single-photon emission tomography

The aim of this study was to determine the diagnostic accuracy of technetium-99m tetrofosmin myocardial imaging for the localization of coronary artery stenoses of different degrees of severity. Stress-rest single-photon emission tomography (SPET) was performed on separate days in 80 patients (64 males, 16 females; mean age 61 years; 43 patients with previous myocardial infarction; 18 patients with pharmacological stress), within 6 months of coronary angiography. Scintigraphic images were blindly and independently evaluated by three observers. Coronary stenosis was defined as a >50% narrowing in luminal diameter; severe stenosis was defined as a proximal stenosis of >75% or a peripheral stenosis of >90%. Coronary angiography revealed normal coronary arteries or insignificant coronary stenosis in 13 patients and significant coronary stenoses in 67 patients. The sensitivity and specificity of ^99mTc-tetrofosmin SPET in respect of severely stenosed vessels were, respectively, 80% and 65% for the left anterior descending artery (LAD), 100% and 46% for the right coronary artery (RCA) and 58 and 78% for the left circumflex artery (LCx) territories. Considering all the significantly stenosed vessels, a significant decrease in sensitivity was observed for LAD territories (to 59%, P=0.05), and a nonsignificant decrease for RCA (88%) and LCx (47%) territories while specificity values remained essentially unchanged. No significant changes in sensitivity or specificity were observed when regions with previous myocardial infarction were excluded. In conclusion, the sensitivity of ^99mTc-tetrofosmin SPET for the localization of individual stenosed vessels is only moderate when all significant stenoses are considered, but the ability of this technique to predict the location of severe coronary artery stenoses seems satisfactory, with the exception of the low specificity in respect of RCA territories. Received 26 April and in revised form 7 June 1997     

Technetium-99m sestamibi scintigraphy for the assessment of lower extremity ischaemia in peripheral arterial disease

Technetium-99m sestamibi was used for functional investigation of the muscle perfusion of lower extremities in 35 patients with peripheral vascular disease. The aim was to test what useful information could be obtained by additional imaging of the legs in patients referred for risk stratification with dipyridamole myocardial scanning. Posterior images were acquired over the thighs and calves after postocclusive reactive hyperaemia and at rest. Inter- and intraextremity ratios and differences between the stress and rest data were used for the assessment of abnormal circulation. Arteriography was performed in every case, and surgical procedures or transluminal angioplasty in 31 patients. To estimate diagnostic accuracy, the results of^99mTc-sestamibi scintigraphy were compared with those of angiography and the functional consequences of revascularization procedures. The sensitivity and specificity of^99mTc-sestamibi scintigraphy were 55% and 25%, respectively, with an overall accuracy of 50%. Apparently methodological error was not responsible for these poor results. Instead, a paradoxically high uptake of the radiopharmaceutical in muscles supplied by significantly stenosed vessels was identified as the main source of both false-negative and false-positive results. This phenomenon resembles the findings of a previous study involving delayed administration of thallium-201 after exercise. In conclusion,^99mTc-sestamibi scintigraphy has not proved sufficiently reliable to help in the management strategy for patients with peripheral vascular disease.     

Scintigraphic visualization of intrathecal liposome biodistribution

Background: Liposomes containing local anaesthetics have been administered intrathecally and in the epidural space. Poor attention has been given to the pharmacokinetics of liposomes as drug carriers. Therefore, we observed the biodistribution of liposomes after intrathecal injection in rats by scintigraphic imaging during 24 h.
Methods: We administered ⁹⁹Tc-labeled multilamellar (MLV) and small unilamellar vesicles (SUV) of defined size and volume dispersities into the cerebrospinal fluid at the lumbar level. Those vesicles were free of contamination by radiolabeled colloids as visualized by light and electron microscopy and of neurotoxic products from phosphatidylcholine hydrolysis and peroxidation, both during the preparation process and after 24 h incubation in cerebrospinal fluid at 37°C in vitro.
Results: SUV immediately diffused from the lumbar site of injection to the head and were cleared between 1 and 24 h after injection. MLV were cleared more slowly from the spinal space and appeared in the head region 1 h after injection where they accumulated up to 24 h. These differences were explained in terms of vesicle sizes and volumes. SUV with 0.05 μm diameters were rapidly absorbed into the blood through the arachnoid granulations. In contrast, particles larger than the upper size limit of the arachnoid granulations permeability (±8 μm) could accumulate in the head with a slow elimination rate.
Conclusion: This difference in clearance from the intrathecal space outlines the importance of defining the size of the liposomes, the distribution of a tracer or a drug inside the liposomal preparation, the chemical stability and the absence of toxic degradation products of liposome formulations before clinical use.     

A method of simultaneous dual-radionuclide cardiac imaging with technetium 99m and thallium 201. I: Analysis of interradionuclide crossover and validation in phantoms

Background  

Simultaneous dual-radionuclide technetium 99m/thallium 201 scintigraphy can potentially produce perfectly aligned stress and rest images in less time than conventional protocols. However, interradionuclide crossover limits diagnostic accuracy. Accordingly, we evaluated^99mTc and²⁰¹Tl crossover in line and heart phantoms.     

Evaluation of renal first pass blood flow with a functional image technique in hypertensive patients

The renal circulation of patients with essential hypertension and renovascular hypertension was evaluated using ^99mTc-DTPA. The first renal peak count (the first C_max; FC_max), time phase distribution (the first T_max; FT_max), and blood velocity (the FC_max/FT_max) were calculated by digital imaging. This yields a visual image of the renal circulation. We consider that the increase in the renal first pass blood flow in patients with essential hypertension is best observed pixel by pixel. The FC_max and FC_max/FT_max images before and after treatment by percutaneous transluminal renal angioplasty in patients with renovascular hypertension clearly show its therapeutic effect. The FI technique, therefore, has the advantage that it can be performed at the same time as the conventional routine examinations of renal function. This makes it very useful clinically.     

Role of technetium-99m planar bone scanning in the evaluation of low back pain

The records of 1018 patients with low back pain in a tertiary spine referral practice were reviewed. One hundred thirty-nine out of 1018 (13.6%) underwent technetium-99m planar bone scanning as part of their investigation. Seventy-three out of 139 scans (52%) showed increased uptake in some area, but only 27 out of 139 (19.4%) showed increased uptake specifically in the low back. Scans consistently yielded no findings with reference to the back when the prescan diagnosis was spinal stenosis, lumbar pain syndrome, herniated nucleus pulposus, or postlaminectomy syndrome. Some scans gave positive findings in patients with a diagnosis of degenerative disc disease, pseudarthrosis, spondylolisthesis, fracture, infection, metabolic disorder, or tumor. Positive scans were generally obtained early after presentation (within 3 months) and negative scans obtained later (after 6 months), suggesting that clinical suspicion is still the main indication for early scanning. Planar bone scanning was helpful in both diagnosis and therapeutic decisionmaking in many conditions.     

Determination of the mean transit time for the transport of aerosolized 99mTc-DTPA across the pulmonary epithelial membrane. A plasma sample method

Summary. During the last decade it has been customary to estimate pulmonary epithelial permeability (P-P) as the pulmonary clearance of inhaled nebulized ^99mTc-DTPA from a time-activity (t-a) curve registered externally by monitoring over the chest. The t-a curve, however, is not defined by the degree of P-P alone but also by factors such as the deposition of the ^99mTc-DTPA in the lungs. To avoid these problems a plasma sample method was derived. It describes P-P by the mean transit time (t?) for the transport of ^99mTc-DTPA across the pulmonary epithelial membrane, t? (L). The calculation of t? (L) involves two steps. Following the inhalation of Tc-DTPA the plasma t-a curve is defined and used to calculate t? for the transport for ^99mTc-DTPA across the pulmonary epithelial membrane, through the E?V and until elimination by the kidneys, t? (L+ECV). Subsequently, ^99mTc-DTPA is injected as a bolus i.v. and the new t-a curve is used to calculate t? for the transport of ^99mTc-DTPA through ECV to the kidneys, t? (ECV). Finally t? (L) is calculated as t? (L) = -t? (L+ECV) t? (ECV). We applied the method in nine non-smoking individuals (median age 25–5 years, range 20–28) and compared the results to t? as calculated from the initial slope of an externally derived t-a curve. The individual t? (L) values were systematically greater than those of the external detection method (P<0·05). It is concluded that the initial slope method overestimates total PCI as measured by the plasma sample method. When choosing between the two methods, special interest should be paid to the inherent problems of the methods.     

~(99m)Tc-MIBI心肌灌注断层显像监测蒽环类药物的心脏毒性

目的 :探讨99mTc-MIBI心肌灌注断层显像在蒽环类药物心脏毒性监测中的价值。方法 :2 3例接受蒽环类药物治疗的患者 ,在治疗前进行心电图、心肌酶学检查、核素心室造影测左室射血分数 (LVEF)和99mTc MIBI心肌灌注断层显像并计算相对定量值。并于每一周期治疗后重复上述检查。结果 :蒽环类药物治疗一周期后 ,2 3例患者心肌相对定量值明显下降 (P <0 .0 1)。其中 11例吡喃阿霉素、6例表阿霉素和 6例米托蒽醌治疗的患者 ,心肌相对定量值明显下降 (P <0 .0 5 ) ,心电图和心肌酶学无明显变化 (P >0 .0 5 )。蒽环类药物治疗多周期后的 10例患者心肌相对定量值较治疗前下降 (P <0 .0 5 )。 9例患者的心肌相对定量值 (最大累积剂量为 2 0 0mg/m2 )与一周期后无明显差别 (P >0 .0 5 )。10例患者治疗前及多周期治疗后LVEF均 >6 0 %,且化疗前后无明显差别 (P >0 .0 5 )。结论 :99mTC MIBI心肌灌注断层显像能监测蒽环类药物所致的心肌损害 ,且较左室射血分数敏感 ,比心电图和心肌酶学检查优越 ,有利于指导蒽环类药物的临床应用。     

99mTc-depreotide生长抑素受体显像的临床应用研究

生长抑素受体显像近年来研究较多，depreotide已成为其研究热点之一。Depreotide在诊断与鉴别诊断临床常见的孤立性肺结节方面有其独特优势；此外，^99mTc—depreotide生长抑素受体显像在乳腺癌、甲状腺癌、淋巴瘤等肿瘤及甲状腺相关性眼病等非肿瘤性疾病也有一定应用前景。     

Quantitative Analysis of the Tomographic Technetium－99m MIBI （~（99m）Tc－MIBI） Myocardial Bullseye Display： Application to Diag

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