[Progress of cardiovascular nuclear medicine technique and radiopharmaceuticals].
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Dobutamine↗
Biomedical subjects
H Bunko
Publications and source records attributed to H Bunko.
[Nuclear cardiology with new radiopharmaceuticals].
In the field of nuclear cardiology, 99mTc labeled myocardial perfusion agents such as MIBI, Tetrofosmin and Teboroxime, 111In-antimyosin for imaging of myocardial necrosis, 123I-betamethyl-iodophenylpentadecanoic acid (BMIPP) for imaging of myocardial fatty acid metabolism and 123I-metaiodobenzylguanidine (MIBG) for imaging of myocardial adrenergic function are introduced recently in Japan. Improved image quality and simultaneous evaluation of myocardial perfusion, function and wall motion can be obtained with use of 99mTc labeled myocardial perfusion agents. 111In-antimyosin enables specific imaging of myocardial necrosis which leads to the use for wide variety of heart diseases. Discrepancy of the myocardial perfusion and metabolism in case of stunned myocardium or cardiomyopathy can be evaluated by 123I-BMIPP in conjunction with perfusion agent. Recently wide variety of diseases which may have cardiac adrenergic abnormality are targeted for 123I-MIBG imaging. These new radiopharmaceuticals are expected to be powerful tool for evaluation of the pathophysiology including severity and prognosis and evaluation of the etiology of the various heart diseases.
3-Iodobenzylguanidine↗
Regional uptake of iodine-125-metaiodobenzylguanidine in the rat heart.
Regional uptake of iodine-125-metaiodobenzylguanidine ([125I]MIBG) was evaluated in normal (n = 12) and reserpinized (n = 12) rat hearts. At 15 min and 1, 3 and 6 h after injection of [125I]MIBG, tissue activities were calculated for the right ventricular myocardium (RV), the whole left ventricular myocardium (whole LV), the epicardial layer of the left ventricular myocardium (Ep LV), the endocardial layer of the left ventricular myocardium (En LV), the basal segment of the left ventricular myocardium and the apical segment of the left ventricular myocardium. The uptake of [125I]MIBG at 6 h after injection in the normal rat heart was higher in RV than in whole LV (0.45 +/- 0.09% vs 0.30 +/- 0.06% kg dose/g), and in Ep LV than in En LV (0.32 +/- 0.07% vs 0.25 +/- 0.05%). In the reserpinized rat heart, the difference in the uptake between Ep LV and En LV was smaller. This suggests that the difference in the regional [125I]MIBG uptake might reflect different intravesicular uptake in the layers of the heart. To our knowledge, the low uptake in the endocardial layer was a new finding which seems to indicate a difference in innervation between the epicardial and endocardial layers of the left ventricle in the rat heart. Autoradiographic study also showed the low uptake of [125I]MIBG in the endocardial layer, while homogeneous perfusion was observed with thallium-201, supporting the tissue uptake study. Thus, the endocardial and epicardial layers of the left ventricle in the rat heart were considered to be differently innervated.
3-Iodobenzylguanidine↗
123I-labelled BMIPP fatty acid myocardial scintigraphy in patients with hypertropic cardiomyopathy: SPECT comparison with stress 201Tl.
123I-labelled 15-(p-iodophenyl)-3-(R,S)-methylpentadecanoic acid (BMIPP) myocardial single photon emission computed tomography (SPECT) was performed in 17 patients with hypertrophic cardiomyopathy, and was compared with 201Tl exercise stress myocardial perfusion SPECT images. Fourteen patients showed asymmetrical hypertrophy, and three demonstrated apical hypertrophy. SPECT was performed 20 min and 3 h after injection of 111 MBq 123I-BMIPP at rest. Exercise stress 201Tl SPECT was performed at 10 min and 3 h after injection and was compared with BMIPP imaging. In 13 patients BMIPP accumulation in the hypertrophied area in the 20 min image was lower than that of 3 h 201Tl uptake. Interestingly, six patients demonstrated 201Tl redistribution in the region where the uncoupling of BMIPP uptake at 20 min and 201Tl accumulation at 3 h after exercise was observed. These findings suggest that impaired fatty acid metabolism or utilization in hypertrophic myocardium and ischaemia or impaired coronary flow reserve may be one of the causes of the abnormality of fatty acid accumulation.
Adult↗
Saphenous neuralgia and limb edema after femoropopliteal artery by-pass.
One hundred thirty-one limbs of 109 patients who underwent femoropopliteal artery by-pass were studied for postoperative saphenous neuralgia and limb edema. The following factors were analyzed: age, sex, underlying disease (arteriosclerosis obliterans or Buerger's disease), grade of symptoms (Fontaine's classification), presence of diabetes mellitus, the site of distal anastomosis (above or below the knee), vascular graft material (reversed saphenous vein, expanded polytetrafluoroethylene or composite), presence of postoperative hematoma, and levels of serum creatinine and albumin 3 weeks after surgery. To examine limb edema, radioisotope (RI) venography and RI lymphography were performed. Saphenous neuralgia occurred in 22 limbs (16.8%) and limb edema in 27 limbs (20.6%). None of the factors examined was found to be significantly associated with saphenous neuralgia. The risk of developing limb edema was higher in diabetic patients and in patients in whom the distal anastomosis was performed below the knee. Although no case of limb edema was associated with signs of obstruction on RI venogram, 80% of the cases showed lymphatic obstruction on RI lymphograms.
Adult↗
Myocardial perfusion imaging and dynamic analysis with technetium-99m tetrofosmin.
Technetium-99m tetrofosmin is a new myocardial perfusion imaging agent that accumulates rapidly and shows slow clearance from the myocardium. Dynamic acquisition and SPECT imaging were performed in a total of 26 patients. Using exercise-rest protocol, the single-photon emission computed tomography (SPECT) findings of 130 myocardial segments were classified as infarction, ischemia and partial filling and compared to those with 201Tl. Complete concordance of findings was obtained in 108 segments (83%) between images with 99mTc tetrofosmin and 201Tl. Partial filling was observed in 24 segments with 201Tl and 14 segments with tetrofosmin, showing a greater number of ischemic regions in 201Tl. However, in comparison with coronary arteriography (n = 19), overall sensitivity and specificity for detecting coronary artery stenosis (> or = 75%) was 15 of 25 (0.60) and 27 of 32 (0.84), respectively, which did not differ significantly from those of 201Tl, which was 18 of 25 (0.72) and 27 of 32 (0.84), respectively. Graphic analysis that assumes unidirectional transfer of the tracer was applied to initial dynamic changes and uptake constant k and distribution volume V were computed. Multiple vessel disease and congestive heart failure showed a low perfusion index (k/V), and may be used in this type of tracer with unidirectional uptake. This preliminary study in the clinical trial showed the usefulness of 99mTc tetrofosmin as a myocardial perfusion imaging agent.
Coronary Angiography↗
[Evaluation of the safety and clinical usefulness of a new myocardial imaging agent, 99mTc-PPN1011--multicenter phase II clinical trial report].
A new myocardial perfusion imaging agent, 99mTc-1,2-bis[bis(2-ethoxyethyl phosphino]ethane (99mTc-PPN1011) was administered to 52 patients with various heart diseases each at rest and peak exercise on different days (Method A) and on the same day (Method B). The safety, optimal dosage, imaging procedures and the clinical usefulness were evaluated. No drug related adverse reactions were found. Image quality was considered adequate for diagnosis with as little as 185 MBq per injection, though the optimal dose range was 370-740 MBq. SPECT images were obtainable as early as 10 min, also until 3 hours after injection. There were no significant differences in clinical efficacy between method A and B, as well as sequential tests at rest and exercise. 99mTc-PPN1011 and 201T1 images in the same patient were compared segment by segment. Image quality of 99mTc-PPN1011 was significantly superior to that of 201T1. Analysis of images indicated that both agent were similar in diagnostic efficacy. It was concluded that 99mTc-PPN1011 is useful for myocardial perfusion imaging.
Adult↗
[Assessment of congenital heart disease by a thallium-201 SPECT study in children: accuracy of estimated right to left ventricular pressure ratio].
The characteristics of correlation between the right-to-left ventricular systolic pressure ratios (RVp/LVp) and the thallium-201 right-to-left ventricular (201Tl R/L) count ratios was investigated in children with various congenital heart diseases. High-resolution three-headed SPECT system equipped with either parallel-hole or fan-beam collimators was used. In a total of 102 patients, the correlation between RVp/LVp and 201Tl R/L average count ratios was good in both planar (r = 0.89, p = 0.0001) and SPECT studies (r = 0.80, p = 0.0001). Quantitative analysis of myocardial uptake by SPECT demonstrated the characteristic pattern of each disease as well as the differences in the right ventricular overload types. When the linear regression analysis was performed in each heart disease, ventricular septal defect showed most excellent correlation. Complex heart anomalies also showed positive correlation (r = 0.51, p = 0.05) with RVp/LVp, and it can be used to estimate right ventricular pressure. After surgical treatment of tetralogy of Fallot and pulmonary stenosis, the decrease of 201Tl R/L count ratio was in accordance with improvement of right ventricular overload. We conclude that 201Tl SPECT study can be a good indicator for estimation of right ventricular pressure.
Adolescent↗
[Characteristics of the myocardial SPECT images of 99mTc-MIBI and 99mTc-teboroxime].
Characteristics of the myocardial distribution of 99mTc-MIBI and 99mTc-Teboroxime was compared with the myocardial distribution of 201Tl. We made summed myocardial images, in which central three short-axis SPECT slices were added. Rectangular region of interest (ROI) was set on each myocardial segment, and mean counts of each myocardial region was obtained using summed short-axis images. The ratio of inferior-to-anterior mean counts (I/A) was 0.69 +/- 0.20 in 99mTc-MIBI and 0.62 +/- 0.16 in 201Tl. The ratio of inferior-to-lateral mean counts was 0.70 +/- 0.18 and 0.65 +/- 0.13, respectively. Both ratios in 99mTc-MIBI were significantly higher than those in 201Tl (p less than 0.05). 201Tl to 99mTc-MIBI ratios of these two values were 1.11 +/- 0.17 (I/A) and 1.08 +/- 0.16 (I/L). The ratios of I/A and I/L of 99mTc-MIBI were about 10 percent higher than those of 201Tl. 99mTc-Teboroxime dynamic short-axis SPECT images of every three-minute were obtained. The ratios of counts in each wall were calculated similarly. After about 8 minutes, gradual increase in hepatic activity can be a cause of quantitative error in the assessment of SPECT images. We obtained the data with a human cardiac phantom. The myocardial phantom filled with 99mTc or 201Tl was placed in the mediastinal portion that is surrounded by the lung (saw dust) and vertebra (plastic bar). The ratio of I/A was 0.79 and I/L was 0.85 in 201Tl. The I/A ratio was 0.93 and I/L was 0.97 in 99mTc. Both ratios in 99mTc were about 15 percent higher than those in 201Tl.(ABSTRACT TRUNCATED AT 250 WORDS)
Coronary Circulation↗
A simulation of dynamic SPECT using radiopharmaceuticals with rapid clearance.
Data acquisition in SPECT assumes that there is no change in radionuclide distribution during data collection. However, this assumption is not valid in radiopharmaceuticals with rapid temporal changes in radioactivity. Artifacts and quantitative errors are studied using phantom studies, mathematical models, and clinical myocardial data. Projection data of each model were sequentially multiplied by weighting coefficients that varied mono-exponentially with time, and the SPECT images were reconstructed. A long data acquisition time in comparison to the clearance of the tracer can be a significant cause of artifact. When the myocardial septum-to-lateral count ratio is used as an index of distortion, a shorter acquisition time than the effective half-life of the tracer is required to reduce the error of the septum-to-lateral count ratio to within 10%. Since 180 degrees rotation acquisition causes artifacts depending on the direction of rotation, 360 degrees acquisition is preferable. Continuous repetitive rotation acquisition is a suitable method for dynamic SPECT to reduce quantitative errors and artifacts.
Artifacts↗
[Phase 3 study of beta-methyl-p-(123I)-iodophenyl-pentadecanoic acid, a myocardial imaging agent for evaluating fatty acid metabolism--a multi-center trial].
A multi-center trial of beta-methyl-p-(123I)-iodophenyl-pentadecanoic acid (123I-BMIPP) was performed to assess its clinical usefulness in the evaluation of myocardial fatty acid metabolism in 587 patients with various heart diseases. 123I-BMIPP showed relatively decreased uptake compared with 201Tl in the myocardial lesions of 62% of patients with ischemic heart disease (IHD), 39% of those with cardiomyopathy and 32% of those with other heart diseases. In case of myocardial infarction, less uptake of 123I-BMIPP (Type B) than 201Tl was more frequently seen in patients with successful recanalization than in those without recanalization. The patients with matched distribution of the two tracers (Type E) increased in the direct proportion to the interval between the onset of myocardial infarction and the radionuclide studies. The uptake of 123I-BMIPP correlated well with myocardial viability evaluated by 201Tl exercise-redistribution studies. Type B was frequently seen in the areas with 201Tl redistribution, while Type E was seen in the fixed defect areas. In the other heart diseases studied, Type E was observed in approximately 60% of patients with dilated or secondary cardiomyopathies. Type B was seen in about 45% of patients with valvular heart diseases and myocarditis. Various types of mismatch between the two tracers were demonstrated in hypertrophic cardiomyopathy and hypertensive heart disease. It is concluded that 123I-BMIPP is a safe and useful agent for the diagnosis of various heart diseases, since it reflects myocardial fatty acid metabolism.
Adolescent↗
[Myocardial perfusion and clearance of 99mTc teboroxime assessed by SPECT].
99mTc teboroxime is a new myocardial imaging agent that has characteristics of high accumulation in the heart and rapid clearance. We performed tomographic teboroxime study and compared the findings with that of 201Tl. Myocardial teboroxime clearance was calculated by dynamic single photon emission computed tomography (SPECT) using continuous repetitive rotation acquisition method. Teboroxime SPECT image was reconstructed by the three-minute data started from 4 minutes after injection. In 45 myocardial regions (15 patients), complete agreement between 201Tl and 99mTc teboroxime was obtained in 33 regions (73%), when the findings were classified as normal, ischemia and infarction. Significant delay in clearance was seen in the region of coronary stenosis (greater than or equal to 75%) compared with that in the control region (p = 0.0087 at rest, and p = 0.0385 at peak exercise by paired T test). Septum-to-lateral ratios of the clearance and myocardial initial count showed positive correlation (r = 0.743). Further clinical application of this radiopharmaceutical is expected as a new myocardial imaging agent.
Coronary Circulation↗
Application of a continuous ventricular function monitor with miniature cadmium telluride detector to patients with coronary artery bypass grafting.
A continuous ventricular function monitor with a miniature cadmium telluride detector was evaluated and applied to patients with coronary bypass surgery (CABG). Ejection fraction (EF) at rest and change in EF from rest to exercise and postexercise (Y) measured with the device correlated with that of the gamma camera (X) (Y = 0.86x + 6.8(%), r = 0.87, n = 110, p less than 0.001, and Y = 0.96x + 0.4(%), r = 0.90, n = 37, p less than 0.001 respectively). Left ventricular function during and after supine ergometer exercise was monitored in 54 patients before and after CABG. The EF change from baseline to peak exercise improved from -5.9% +/- 8.9% before CABG to 7.2% +/- 7.9% after CABG (p less than 0.001). In all patients but two, a rapid EF increase just after exercise over baseline EF was observed. This EF "overshoot" during recovery increased from 11.5% +/- 6.5% to 16.4% +/- 6.0% (p less than 0.001) after CABG. The time from the cessation of exercise to EF overshoot decreased from 153 +/- 80 sec to 76 +/- 49 sec (p less than 0.001) after CABG. The continuous ventricular function monitor with a miniature cadmium telluride detector is able to measure EF reliably. Following successful aortocoronary bypass, EF response during exercise improved and the EF overshoot in the recovery phase became faster and higher.
Cadmium↗
Assessment of right ventricular overload by a thallium-201 SPECT study in children with congenital heart disease.
Thallium-201 planar and SPECT studies were performed in 38 children with congenital heart disease using high-resolution three-headed SPECT. The 201Tl total or average right ventricular-to-left ventricular (RV/LV) count ratios were measured by summed short-axis images. In the planar study, the RV/LV systolic pressure ratio correlated with 201Tl RV/LV average count ratio (r = 0.91) better than that in the SPECT study (r = 0.78). However, in the SPECT study, patients with atrial septal defect (n = 9), ventricular septal defect (n = 13), tetralogy of Fallot and double outlet right ventricle (n = 6) showed a characteristic distribution in the plot of RV/LV pressure ratio versus 201Tl RV/LV total count ratio. A prospective study showed that the RV/LV average count ratio was a good predictor of RV/LV pressure ratio (n = 19, r = 0.91). Three-headed SPECT is useful for pediatric cardiac studies, and the overload types found in congenital heart disease seemed to be differentiated by the SPECT study.
Adolescent↗
[Cardiac response to exercise before and after coronary artery bypass grafting: evaluation by continuous ventricular function monitor].
Cardiac response to exercise was evaluated with continuous ventricular function monitor (VEST) with cadmium telluride detector. Thirty-nine patients (30 male and 9 female, aged 57 +/- 8, 23 had old myocardial infarction) were monitored with VEST during and after supine ergometer exercise before and 4 weeks after coronary artery bypass grafting (CABG). Left ventricular ejection fraction (EF) responses were classified into 4 types; type A showed EF increase greater than 5% till end of exercise, type B demonstrated initial increase followed by decrease in EF, type C revealed no significant EF change, type D showed continuous EF decrease. Before CABG, each EF response type A, B, C, and D consisted of 4, 2, 12, 21 patients respectively and after CABG each type included 18, 10, 9, 2. The EF change from rest to peak exercise (delta EF-Ex) improved from -6.4 +/- 8.8% to 5.0 +/- 7.4% (p less than 0.001) after CABG. All patients showed rapid EF increase after exercise or "EF overshoot" (EF-OS). After CABG, the EF change from rest to EF-OS (delta EF-OS) and time to EF-OS (T-OS) were improved from 9.9 +/- 5.2% to 14.9 +/- 5.3% (p less than 0.001) and 162 +/- 86 sec to 80 +/- 48 sec (p less than 0.001) respectively. Type A, B patients showed higher delta EF-OS and shorter T-OS than type C, D patients, suggesting EF overshoot was contingent upon cardiac function during exercise. After CABG, in patients with myocardial infarction, T-OS shortened but delta EF-OS showed less improvement than patients without infarction, suggesting loss of myocardium hampered EF-OS.
Aged↗
[Assessment of myocardial viability by 24-hour imaging after stress thallium-201 scintigraphy].
Twenty-four-hour delayed imaging after stress thallium-201 scintigraphy was assessed for more accurate detection of viable myocardium. Thirty-two patients with coronary artery disease who showed fixed perfusion abnormality (FPA) at 3 hr imaging after stress Tl study were evaluated with 24 hr delayed imaging. Of 37 areas with FPA, 19 areas (51%) showed redistribution (RD) at 24 hr imaging. After successful coronary artery bypass grafting (n = 19) or transluminal coronary angioplasty (n = 3), stress Tl scintigraphy was performed. Of 13 areas with RD at 24 hr imaging, 12 revealed improvement of Tl uptake after revascularization. On the other hand, of 12 areas with FPA until 24 hr, 8 showed no improvement. In conclusion, conventional stress Tl-201 scintigraphy underestimates myocardial viability, and additional 24 hr imaging permits more accurate assessment of myocardial viability.
Adult↗
[Basic evaluation of an ambulatory ventricular function monitor with a a cadmium telluride detector].
The reliability of a new ambulatory ventricular function monitor (VEST) with cadmium telluride (Cd-Te) detector was validated. No counting loss was observed under 20 kcps. In phantom study, more than 200 ml with 6 cm distance from the detector and more than 300 ml with 6-12 cm distance, underestimation of volume was observed. Ejection fraction (EF) calculated in phantom study showed close value to the true EF in 50-400 ml of end-diastolic volume. In 10 patients, 1-2 cm detector shift toward right upper, upper and left showed underestimation of EF. Good correlation of gamma camera EF (X) and VEST EF (Y) was obtained (Y = 0.96X + 3.6(%), n = 37, r = 0.93, p less than 0.001). EF change from rest values, obtained from each comparable exercise and post exercise stage by gamma camera (X) and VEST (Y), showed good correlation (Y = 0.95X + 0.8, n = 20, r = 0.85, p less than 0.001). In conclusion Cd-Te VEST was considered as a reliable EF measurement technique similar to gamma camera.
Cadmium↗
[Clinical evaluation of 123I-MIBG for assessment of the sympathetic nervous system in the heart (multi-center clinical trial)].
Multi-center clinical trial of 123I-metaiodobenzylguanidine (123I-MIBG) was carried out to assess its utility as a scintigraphic imaging agent reflecting sympathetic neuronal function in cardiovascular field. Studies were performed on patients with heart diseases of three categories, myocardial infarction, angina pectoris and cardiomyopathy. Scintigraphic images, reflecting sympathetic neuronal function were obtained with 123I-MIBG from all of those categories of patients and the efficacy of the imaging was revealed in 781 (95.0%) out of 822 patients. In some patients abnormality was suggested in sympathetic neuronal function with 123I-MIBG imaging, in spite of normal findings with myocardial perfusion scintigraphy by 201TlCl. In all 981 patients studied with 123I-MIBG, there have been no severe adverse reactions, except complaints of burning on injection site of the agent or nausea, etc. from 4 patients. We conclude that 123I-MIBG imaging is one of the effective tools for diagnostic use reflecting topical sympathetic neuronal function in the heart, judging from its safety and efficacy.
3-Iodobenzylguanidine↗