Residual cardiomyocytes and scintigraphic findings in advanced coronary artery disease: correlation with technetium-99m-tetrofosmin and thallium-201 single photon emission computed tomography.
A 68-year-old man suffering from chronic heart failure due to coronary artery disease (CAD) underwent rest technetium-99m (99mTc)-tetrofosmin and thallium-201 (201Tl) with reinjection studies, but died thereafter. The heart was removed and sectioned into short-axis slices and examined by gross and microscopic pathologic methods. A close correlation between the amount of residual cardiomyocytes and the level of regional tracer activity in the left ventricular wall was obtained for redistribution 201Tl, reinjection 201Tl and rest 99mTc tetrofosmin images. The correlation coefficients were r=0.901 for the 201Tl redistribution images, r=0.913 for the 201Tl reinjection images and r=0.917 for the rest 99mTc-tetrofosmin images. This case report provides further evidence of the validity of SPECT tetrofosmin imaging for the determination of myocardial viability in CAD. (+info)
Comparative study of 99mTc-ECD and 99mTc-HMPAO for peri-ictal SPECT: qualitative and quantitative analysis.
OBJECTIVES: Most studies that clinically validated peri-ictal SPECT in intractable partial epilepsy had used technetium-99m-hexamethylpropylene amine oxime (99mTc-HMPAO or 99mTc-exametazime) as the radiopharmaceutical. Because of some theoretical advantages, technetium-99m-ethyl cysteinate diethylester (99mTc-ECD or 99mTc-bicisate) is increasingly being used instead. This study compares unstabilised 99Tc-HMPAO and 99mTc-ECD in the performance of peri-ictal SPECT in partial epilepsy. METHODS: The injection timing and localisation rates in 49 consecutive patients with partial epilepsy who had peri-ictal injections with unstabilised 99mTc-HMPAO were compared with 49 consecutive patients who had peri-ictal injections with 99mTc-ECD. Quantitative cortical/subcortical and cortical/extracerebral uptake ratios were also compared. Subtraction SPECT coregistered to MRI (SISCOM) was performed in patients whose interictal SPECTS were available. RESULTS: In the 99mTc-ECD patients, the latency from seizure commencement to injection was shorter (median 34 v 80 seconds, p<0.0001) and there was a lower rate of postictal injections (16.3% v 57.1%, p<0.0001). The cortical/extracerebral and cortical/subcortical uptake ratios were greater in the 99mTc-ECD images (median 5.0 v 3.6, and 2.5 v 2.2 respectively; both p<0.005), but the relative peri-ictal increase in uptake in the cortical focus did not differ significantly (median 37.0% v 37.0%; p>0.05). Blinded review of the SISCOM images were localising in a higher proportion of the 99mTc-ECD patients (40/45 (88.9%) v 25/37 (67.6%), p<0.05), and had a better concordance with EEG, MRI, and with the discharge diagnosis. CONCLUSION: 99mTc-ECD compares favourably with unstabilised 99mTc-HMPAO as a radiopharmaceutical for peri-ictal SPECT studies. Its use results in earlier injections and less frequent postictal injections than unstabilised 99mTc-HMPAO, thereby enhancing the sensitivity and the specificity of peri-ictal SPECT for the localisation of intractable partial epilepsy. (+info)
Prospective validation of single plasma sample 99mTc-ethylenedicysteine clearance in adults.
99mTc-L,L-ethylene, L, dicysteine (EC) clearance shows strong correlation with orthoiodohippurate clearance, and it is possible to estimate effective renal plasma flow from 99mTc-EC clearance. In routine clinical studies, it is practical to use the one or two plasma sample method instead of multiple plasma samples for clearance determination. A single-sample technique was developed for 99mTc-EC, and a regression formula was generated. A prospective study tested the validity of this regression formula. METHODS: The study population was composed of 26 patients with a wide range of renal function. Multiple plasma sample 99mTc-EC clearances were calculated from all patients using the open two-compartment model. Single plasma sample clearances were also determined from the 54-min plasma sample using the regression formula published previously. RESULTS: The multiple-sample plasma clearance of 99mTc-EC ranged from 46 to 668 mL/min with a mean of 300.76 +/- 150.73 mL/min. The clearances obtained from the 54-min plasma sample ranged from 49 to 699 mL/min, with a mean of 297.39 +/- 152.23 mL/min. There was an excellent correlation between the clearances obtained by the two techniques (r = 0.99, slope = 0.9911). The standard error of estimation was found to be 25.9 mL/min. CONCLUSION: This study suggests that 99mTc-EC clearance can be estimated from 54-min plasma samples with an acceptable error of estimation for most routine clinical studies. (+info)
Extracorporeal rheopheresis in the treatment of acute ischemic stroke: A randomized pilot study.
BACKGROUND AND PURPOSE: Extracorporeal rheopheresis is a safe method to optimize hemorheology. Our aim was to determine whether treatment with extracorporeal rheopheresis in patients with acute ischemic hemispheric stroke improves cerebral perfusion as assessed with serial 99mTc-ethyl-cysteinate-dimer single-photon emission CT (99mTc-ECD SPECT). We also investigated how clinical outcome is associated with treatment and imaging results. METHODS: Thirty-three patients (mean age, 64+/-10 years) with acute ischemic hemispheric stroke were included in a prospective, randomized, parallel group pilot study. First treatment with or without extracorporeal rheopheresis took place within 12 hours after the onset of symptoms and was repeated 3 times at intervals of 24 hours. Hemorheological parameters were measured before and after each session. Each patient underwent 99mTc-ECD SPECT immediately before treatment, 6 to 8 hours after treatment, and after 5 days. A semiquantitative SPECT graded scale was used to measure depth and extent of activity deficits and thus to quantify the perfusion deficit. RESULTS: Seventeen patients were actively treated with extracorporeal rheopheresis, and 16 patients did not receive extracorporeal rheopheresis. After 3 months, no differences were found in the functional or neurological outcome. Despite a rapid, sustained decrease of plasma viscosity and erythrocyte aggregation in the rheopheresis group, there was no significant difference in the SPECT graded scale after therapy between the 2 groups. Patients with early reperfusion (decrease in the SPECT graded scale >25% 6 to 8 hours after therapy compared with the baseline examination) experienced a better functional outcome (Modified Rankin Scale) after 3 months compared with patients without reperfusion (P=0.04). CONCLUSIONS: Since quantitative flow mapping and clinical follow-up did not reveal any differences between patients who were treated with extracorporeal rheopheresis and controls, it appears very unlikely that extracorporeal rheopheresis enhances reperfusion after acute cerebral ischemia. (+info)
Imaging experimental intraabdominal abscesses with 99mTc-PEG liposomes and 99mTc-HYNIC IgG.
OBJECTIVE: To evaluate the accuracy of technetium-99m-labeled polyethylene glycol-coated liposomes (99mTc-PEG liposomes) and technetium-99m-labeled nonspecific human immunoglobulin G (99mTc-HYNIC IgG) for the scintigraphic detection of experimental intraabdominal abscesses in comparison with that of a standard agent, gallium-67 citrate. BACKGROUND: Scintigraphic imaging techniques can be very useful for the rapid and accurate localization of intraabdominal abscesses. Two newly developed radiolabeled agents, 99mTc-PEG liposomes and 99mTc-HYNIC IgG, have shown to be excellent agents for imaging experimental focal infection, but have not yet been studied in the detection of abdominal abscesses. METHODS: Intraabdominal abscesses were induced in 42 rats using the cecal ligation and puncture technique. Seven days later, randomized groups of rats received 99mTc-PEG liposomes, 99mTc-HYNIC IgG, or 67Ga citrate intravenously. The rats were imaged up to 24 hours after the injection. The biodistribution of the radiolabel was determined by counting dissected tissues ex vivo. Macroscopic intraabdominal abnormalities and focal uptake on the images were independently scored on a semiquantitative scale. RESULTS: 99mTc-PEG liposomes provided the earliest scintigraphic visualization of the abscess (as soon as 2 hours after the injection vs. 4 hours for the other two agents). Liposomes, IgG, and gallium all showed similarly high absolute uptake in the abscess. Focal uptake of liposomes and gallium correlated best with the extent of the macroscopic abnormalities. CONCLUSIONS: 99mTc-PEG liposomes and 99mTc-HYNIC IgG performed at least as well as the standard agent, 67Ga citrate, in the detection of experimental intraabdominal abscesses, with obvious advantages such as lower radiation exposure and more favorable physical properties. Of the two technetium agents, the liposomes seemed to be superior, providing the earliest diagnostic image and the best correlation with the inflammatory abnormalities. In addition, the preferential localization of radiolabeled PEG liposomes holds promise for targeted delivery of liposome-encapsulated drugs. (+info)
Simultaneous SPECT studies of pre- and postsynaptic dopamine binding sites in baboons.
The central nervous system dopamine transporters (DATs) and dopamine D2/D3 receptors are implicated in a variety of neurological disorders. Both sites are also targets for drug treatment. With the successful development of [99mTc]TRODAT-1, single-isotope imaging studies using this ligand for DAT imaging can be complemented by additional use of 123I-labeled D2/D3 receptor ligand co-injected to assess both pre- and postsynaptic sites of the dopaminergic system simultaneously. METHODS: Twelve SPECT scans of the brain were obtained in two baboons after intravenous administration of 740 MBq (20 mCi) [99mTc]-TRODAT-1 (technetium, [2-[[2-[[[3-(4-chlorophenyl)-8-methyl-8-azabicyclo[3,2,1]oct-2-yl]methyl ](2-mercaptoethyl) amino]ethyl]-amino]ethanethiolato (3-)]- oxo-[1R-(exo-exo)]) and 185 MBq (5 mCi) [123I]iodobenzamide or [123I]iodobenzofuran. SPECT data were acquired by a triple-head gamma camera equipped with ultra-high-resolution fanbeam collimators (scan duration = 210 min). Two sets of SPECT data were obtained using energy windows of 15% centered on 140 keV for 99mTc and 10% asymmetric with a lower bound at 159 keV for 123I. After coregistration with MRI, region-of-interest analysis was performed using predefined templates from coregistered MRI. In blocking studies, baboons were pretreated with N-methyl-2beta-carbomethoxy-3beta-(4-fluorophenyl)tropane (CFT, 14 mg) or raclopride (14 mg) to block DAT or D2/D3 binding site, respectively. RESULTS: Image quality of dual-isotope studies was similar to that obtained from single-isotope studies. When one site was blocked with CFT or raclopride, the binding of the respective ligand to the other site was not affected. CONCLUSION: This is the first example that clearly demonstrates the feasibility of simultaneous imaging of both pre- and postsynaptic sites of the dopaminergic system in baboons with dual-isotope SPECT studies. With or without corrections for cross-contamination of 123I into the 99mTc window, striatum-to-cerebellum ratios (target-to-nontarget) of dual-isotope experiments did not differ significantly from single-isotope experiments. This method may be a valuable and cost-effective tool for gaining comprehensive information about the dopaminergic system in one SPECT imaging session. (+info)
Use of subtraction ictal SPECT co-registered to MRI for optimizing the localization of seizure foci in children.
Ictal SPECT studies are increasingly used to localize seizure foci in children with refractory epilepsy, but few studies have reported on ictal-interictal subtraction images co-registered to MRI at this age. METHODS: Twenty-seven children with partial epilepsy (aged 3 mo-18 y) underwent ictal ethyl cysteinate dimer (ECD) SPECT (20 mCi/1.73 m2) combined with video-electroencephalography (EEG) and interictal ECD SPECT followed 2 d later by three-dimensional MRI. Ictal-interictal and interictal-ictal subtraction images were computed by registering and normalizing the ictal to the interictal SPECT scans for each child. The ictal, interictal SPECT and subtraction images were registered to each child's MRI. Difference images (ictal-interictal) were then superimposed on MRI for anatomic localization of the perfusion changes. Intra- and interobserver reproducibility and "facility of interpretation" of overlay images were compared with standard analysis of the non-coregistered ictal and interictal scans. RESULTS: Overlay images allowed the detection of at least one hyperperfused focus in 93% of the children, compared with 74% using ictal and interictal scans separately. Seizure onset was suspected clinically, on EEG or on MRI in 20 children. Overlay images were concordant (n = 11) or larger (n = 7) than the suspected focus in 18 of 20 (90%), whereas these images failed to show any abnormality in 1 child and were discordant with MRI in another patient. In the remaining 7, images showed cortical localization in 6 patients. Among the 5 patients who underwent electrocorticography, overlay images were concordant in 3, larger in 1 and absent in 1. The intra- and interobserver reproducibility and facility of interpretation were significantly higher using overlay images than standard analysis, even when ictal and interictal SPECT were co-registered. CONCLUSION: The co-registration of ictal-interictal subtraction SPECT images to MRI seems to be a helpful technique in localizing the onset of seizure and guiding the intracranial recording in childhood epilepsy. Moreover, this method improves sensitivity, enhances intra- and interobserver reproducibility and makes interpretation easier. (+info)
In vivo and in vitro characterizations of three 99mTc-labeled monoclonal antibody G250 preparations.
In previous clinical studies, excellent visualization of tumor lesions has been observed with 131I-labeled monoclonal antibody (mAb) G250 in patients with renal cell carcinoma (RCC). In several cases, 131I-cG250 immunoscintigraphy disclosed tumor lesions that were not visualized by radiography or CT. To improve image quality, we aimed to develop a 99mTc-labeled mAb G250 preparation for radioimmunodetection of RCC. We studied in vitro stability, biodistribution and imaging potential of three 99mTc-labeled G250 preparations in nude mice with subcutaneous RCC xenografts.125I-G250 and the nonspecific mAb 131I-MN14 were used as control antibodies. METHODS: The mAb G250 was labeled with 99mTc according to three methods using: (a) S-hydrazinonicotinamide (HYNIC), (b) S-benzoylmercaptoacetyltriglycine (MAG3) and (c) a direct labeling method (Schwarz method). The stability of all preparations was tested in serum at 37 degrees C during 48 h. In addition, diethylenetriamine pentaacetic acid, cysteine and glutathione challenge assays were performed. RESULTS: All preparations showed good stability in serum during the 48-h incubation period. 99mTc-G250 (Schwarz) showed release of the radiolabel at a 100-fold or higher molar excess of cysteine and at a 10,000-fold or higher molar excess of glutathione. 99mTc-MAG3-G250 showed release of the radiolabel at a 10,000-fold molar excess of cysteine. 99mTc-HYNIC-G250 was stable under all conditions. Tumors were clearly visualized with all preparations. 99mTc-G250 (Schwarz) showed significantly lower blood levels (3.8 %ID/g) compared with all other preparations (11.2, 13.4 and 13.4 %ID/g for 99mTc-HYNIC-G250, 99mTc-MAG3-G250 and 125I-G250, respectively, 48 h postinjection). At 48-h postinjection, mean tumor uptake was very high with all mAb G250 preparations: 92.4 (99mTc-HYNIC-G250), 125.9 (99mTc-MAG3-G250), 29.4 (99mTc-G250 Schwarz) and 75.4 (125I-G250) %ID/g. Mean tumor uptake of the nonspecific 131I-MN14 mAb was 6.6 %ID/g. CONCLUSION: In this study, 99mTc-HYNIC-G250 showed excellent in vitro stability and tumor targeting. Moreover, this preparation could be labeled with high efficiency (>95%) at room temperature within 15 min. Therefore, 99mTc-HYNIC-G250 seems to be an ideal candidate for radioimmunodetection of RCC. (+info)