Detecting myocardial salvage after primary PTCA: early myocardial contrast echocardiography versus delayed sestamibi perfusion imaging.
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The extent of myocardial salvage after primary percutaneous transluminal coronary angioplasty (PTCA) in acute myocardial infarction (AMI) is variable and cannot be predicted on the basis of either vessel patency or early regional wall motion assessment. The aim of this study was to evaluate the reliability of microvascular integrity, as shown by myocardial contrast echocardiography (MCE), as an indicator of tissue salvage and a predictor of late functional recovery, and to compare MCE with the quantification of tracer activity in sestamibi perfusion imaging. METHODS: Twenty-six patients with AMI who received successful treatment with primary PTCA were examined with MCE during cardiac catheterization immediately before and after vessel recanalization. Myocardial contrast effect was scored as 0 (absent), 0.5 (partial) or 1 (normal). Wall motion was assessed by two-dimensional echocardiography on admission and 1 mo later with a 16-segment model and 4-point score. Resting sestamibi SPECT was collected within 1 wk after AMI. The risk area was defined by MCE as the sum of the segments with no perfusion (score 0) before PTCA. Myocardial viability was defined by MCE as an increase in contrast score in the same segments after PTCA and by sestamibi SPECT as a preserved tracer activity (>60% of peak activity). The functional recovery after 1 mo detected by two-dimensional echocardiography was the reference standard for viability. RESULTS: A total of 50 segments showed perfusion defects before PTCA (risk area). Immediately after PTCA, the MCE score increased in 44 of 50 segments, whereas sestamibi SPECT showed preserved activity in 22 of 50 segments. After 1 mo, the wall motion score decreased in 22 of 50 segments (viable segments) and was unchanged in the remaining 28 segments. Thus, MCE showed a sensitivity of 91% and a specificity of 14% in detecting viable myocardium, whereas sestamibi SPECT showed a lower sensitivity (68%) but a significantly higher specificity (75%; P < 0.00001). The positive predictive values were 45% and 68% for MCE and SPECT (P < 0.005), respectively, and the negative predictive values were 67% and 71%, respectively. On a patient basis, SPECT was more specific (79% versus 21%; P < 0.01) and showed a higher overall predictive accuracy (88% versus 50%; P < 0.01) than MCE. CONCLUSION: The demonstration of microvascular integrity by MCE performed immediately after primary PTCA has a limited diagnostic value in predicting salvaged myocardium. Conversely, tracer activity quantification in resting sestamibi SPECT performed in a later stage is confirmed to be a reliable approach for recognizing myocardial stunning and predicting functional recovery. (+info)
Lobar decrease in 99mTc-GSA accumulation in hilar cholangiocarcinoma.
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Hilar cholangiocarcinoma can obstruct hepatic ducts and involve the portal veins. Both biliary stasis and decrease in portal venous flow are known to reduce 99mTc-diethylenetriamine pentaacetic acid-galactosyl human serum albumin (GSA) accumulation. The specific relationship between these pathological conditions due to hilar cholangiocarcinomas and 99mTc-GSA accumulation has never been clarified. METHODS: Sixteen patients with hilar cholangiocarcinomas who underwent 99mTc-GSA liver scintigraphy were reviewed. The relationship between significant decrease in 99mTc-GSA accumulation and lobar biliary stasis, or decrease in the portal venous flow, was evaluated. Average counts of region of interest placed in both right and left lobes were compared in the same transaxial SPECT section. Count ratios of right and left lobes were calculated. RESULTS: Significant lobar decrease in 99mTc-GSA accumulation was observed in 6 of the 16 patients. Ipsilateral portal venous stenosis or obstruction was seen in all these 6 patients, whereas ipsilateral portal venous stenosis or obstruction was seen in only 1 of the other 10 patients. Symmetric bile duct dilatation was seen in 13 patients, and asymmetric bile duct dilatation was seen in 3. Lobar decrease in 99mTc-GSA accumulation correlated well with decrease in ipsilateral portal venous flow (P < 0.0005). The count ratio was significantly reduced when unilateral portal venous flow decreased (P < 0.05). CONCLUSION: Using 99mTc-GSA liver scintigraphy, we can predict lobar decrease in ipsilateral portal venous flow and monitor hepatic functional lateralities in patients with hilar cholangiocarcinomas. (+info)
Automatic three-dimensional multimodality registration using radionuclide transmission CT attenuation maps: a phantom study.
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Coregistration of images from a single subject, acquired by different modalities, is important in clinical diagnosis, surgery and therapy planning. The purpose of this study was to evaluate, using a physical torso phantom, a novel, fully automated method for three-dimensional image registration of CT and SPECT, using radionuclide transmission (RNT) attenuation maps. METHODS: We obtained CT scans and SPECT scans paired with RNT maps of an anthropomorphic cardiac phantom. RNT attenuation maps were acquired using an uncollimated 99mTc-filled flood source. RNT and SPECT scans were acquired in the same spatial orientation (usual clinical practice in nonuniform attenuation correction). In addition, CT attenuation maps (CTMAPs) for 99mTc SPECT were generated from CT by linear energy scaling. RNT maps were registered to CT and CTMAPs by iterative simplex minimization of count difference and uniformity index (sum of RNT map intensity variances corresponding to each intensity level in the CT volume). In each iteration, three shifts and three angles were adjusted. To register SPECT to CT, we applied the RNT transformation parameters to SPECT. RESULTS: RNT maps could be registered to CT and CTMAP images using both criteria. The average three-dimensional distance between landmark and automated registration was 2.5 +/- 1.2 mm for count difference and 3.3 +/- 1.3 mm for uniformity index. The three-dimensional reproducibility errors were 1.2 +/- 0.7 mm for count difference, 2.1 +/- 0.5 mm for uniformity index and 2.3 +/- 1.0 mm for manual marker registration. The minimization of uniformity index was robust when up to 50% CT or RNT slices were missing and was not affected significantly (<2 mm) by realistic variation in CT values (+/- 12 Hounsfield units). CONCLUSION: In addition to typical use in nonuniform attenuation correction, RNT maps can be used for fully automated three-dimensional registration of SPECT to CT. Such registration is not affected by features and quality of SPECT images and avoids difficulties associated with fiducial markers. Our method can be applied to SPECT-CT registration of various organs, such as brain, heart, lungs, breasts and abdomen, including oncological scans. (+info)
Attenuation compensation in 99mTc SPECT brain imaging: a comparison of the use of attenuation maps derived from transmission versus emission data in normal scans.
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Brain SPECT imaging using 99mTc lipophilic tracers such as hexamethyl propyleneamine oxime (HMPAO) attempts to estimate cerebral, cerebellar and subcortical perfusion by assessing the relative amount of tracer uptake among these regions. Most commonly, comparison is made with cerebellar activity. Because the assessment of relative tracer uptake may be rendered inaccurate by photon attenuation by the nonuniform attenuation properties of the head, brain SPECT reconstructions have been compared using attenuation correction (AC) with various methods for estimating the attenuation map. METHODS: Patients underwent 99mTc-HMPAO brain SPECT with transmission line source AC hardware. In addition to the emission dataset, emission downscatter and transmission datasets were acquired. Iterative reconstructions using three different attenuation maps were investigated. These included: (a) that obtained from transmission imaging, (b) that obtained from segmentation of a reconstruction from a lower energy Compton scatter window and (c) a slice-independent, uniform, elliptical attenuation map. No AC was also compared. RESULTS: Count profiles in patients having brain perfusion SPECT scans showed a significant difference in region count estimates in the brain depending on whether AC is used as well as on the attenuation map used. Scatter-based AC is able to provide external contour detection and attenuation compensation based on that contour, whereas transmission-based AC provides external contour detection as well as internal, nonuniform attenuation estimation and AC. If one considers transmission AC to be the clinical "gold standard," non-attenuation-corrected as well as fixed-ellipsoid, uniform attenuation-corrected studies provided unreliable regional estimates of tracer activity. CONCLUSION: This study shows the significant difference in clinical brain SPECT count profiles depending on how and whether there is compensation for attenuation. Based on prior studies validating the improved quantitative accuracy of SPECT using transmission-based AC, this study suggests that clinical 99mTc brain perfusion SPECT would benefit from and, in situations demanding rigorous quantitative assessment, requires transmission-based AC. Estimating attenuation maps with scatter-based methods was the next most accurate (clinical) method tested and can be used if and when transmission imaging cannot be used. (+info)
Myocardial metabolism of 123I-BMIPP in a canine model with ischemia: implications of perfusion-metabolism mismatch on SPECT images in patients with ischemic heart disease.
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123I-(rho-iodophenyl)-3-R,S-methylpentadecanoic acid (BMIPP) is a fatty acid analog for SPECT imaging. This radiopharmaceutical possesses the unique property, that is, perfusion-metabolism mismatch on SPECT images in patients with ischemic heart disease. However, the reason of this mechanism remains unclear. METHODS: Using open-chest dogs under anesthesia, we made a system to release all the blood of the great cardiac vein outside without recirculation, if necessary. Left anterior descending artery (LAD) was occluded for 30 min after reperfusion. After the injection of BMIPP into LAD, blood samplings from the cardiac vein and abdominal aorta (6 dogs) or serial biopsy specimens from the LAD region (5 dogs) were performed, and then compared with the normal control. The catabolites of BMIPP, including backdiffusion of nonmetabolized BMIPP, were evaluated with high-performance liquid chromatography (HPLC) in the efflux study. Thin-layer chromatography (TLC) technique was introduced in the tissue analytical study. RESULTS: Although the rapid extraction of BMIPP from the plasma into the myocardium and the subsequent retention were unchanged, the early washout (8 min) of radioactivity significantly increased (51% +/- 12% to 65% +/- 7%; P < 0.05) with ischemia. The metabolites from the myocardium consisted of backdiffusion of nonmetabolized BMIPP, alpha, intermediate, and full oxidation metabolites. Among these metabolites, backdiffusion of nonmetabolized BMIPP in blood significantly increased (27.9% +/- 7.7% to 42.3% +/- 8.1%; P < 0.05), especially in the early phase with ischemia. In tissue, the radioactivity was concentrated in the triglyceride pool even in the early phase, and in addition, BMIPP and alpha-oxidized metabolite significantly decreased in the early phase with ischemia (t = 1 min after BMIPP injection, 25.9% +/- 8.6% to 14.5% +/- 2.1%, P < 0.01; t = 2 min, 8.9% +/- 5.0% to 4.5% +/- 1.7%, P < 0.05). CONCLUSION: These results show that backdiffusion of nonmetabolized BMIPP from the myocardium increased and BMIPP (long-chain fatty acids) in tissue decreased with ischemia, suggesting backdiffusion of nonmetabolized BMIPP might play an important role in myocardial perfusion-metabolism mismatch on SPECT images in patients with ischemic heart disease. (+info)
Assessment of regional and global left ventricular function by reinjection T1-201 and rest Tc-99m sestamibi ECG-gated SPECT: comparison with three-dimensional magnetic resonance imaging.
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OBJECTIVES: The purpose of this study was to test the ability of reinjection thallium-201 and rest technetium-99m sestamibi ECG (electrocardiographic)-gated SPECT (i.e., reinjection-g-SPECT [single-photon emission computed tomography] and MIBI-g-SPECT) to determine regional and global functional parameters. BACKGROUND: The ECG-gated perfusion SPECT was reported to provide accurate left ventricular ejection fraction (LVEF) using an automated algorithm. We hypothesized that other various functional data may be obtained using reinjection-g-SPECT and MIBI-g-SPECT. METHODS: Reinjection-g-SPECT, MIBI-g-SPECT, and three-dimensional magnetic resonance imaging (3DMRI) were conducted in 20 patients with coronary artery disease. Regional wall motion (RWM) and wall thickening (RWT) were analyzed using semiquantitative visual scoring by each g-SPECT and 3DMRI. The left ventricular end-systolic and end-diastolic volumes (EDV, ESV) and LVEF estimated by reinjection- and MIBI-g-SPECT were compared with the results of 3DMRI. RESULTS: A high degree of agreement in RWM and RWT assessment was observed between each g-SPECT and 3DMRI (kappa >.70, p < .001). The LVEF values by reinjection- and MIBI-g-SPECT correlated and agreed well with those by 3DMRI (reinjection: r = .92, SEE = 5.9%, SD of differences = 5.7%; sestamibi: r = .94, SEE = 4.4%, SD of differences = 5.1%). The same also pertained to EDV (reinjection: r = .85, SEE = 18.7 ml, SD of differences = 18.4 ml; sestamibi: r = .92, SEE = 13.1 ml, SD of differences = 13.0 ml) and ESV (reinjection: r = .94, SEE = 10.3 ml, SD of differences = 10.3 ml; sestamibi: r = .97, SEE = 6.7 ml [p < .05 vs. reinjection by F test], SD of differences = 6.6 ml [p < .05 vs. reinjection by F test]). CONCLUSIONS: Reinjection- and MIBI-g-SPECT provide clinically satisfactory various functional data. These functional data in combination with the perfusion information will improve diagnostic and prognostic accuracy without an increase in cost or the radiation dose to the patients. (+info)
Influence of a platelet GPIIb/IIIa receptor antagonist on myocardial hypoperfusion during rotational atherectomy as assessed by myocardial Tc-99m sestamibi scintigraphy.
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OBJECTIVES: This study evaluated the effect of the glycoprotein IIb/IIIa (GPIIb/IIIa) antagonist abciximab on myocardial hypoperfusion during percutaneous transluminal rotational atherectomy (PTRA). BACKGROUND: PTRA may cause transient ischemia and periprocedural myocardial injury. A platelet-dependent risk of non-Q-wave infarctions after directional atherectomy has been described. The role of platelets for the incidence and severity of myocardial hypoperfusion during PTRA is unknown. METHODS: Seventy-five consecutive patients with complex lesions were studied using resting Tc-99m sestamibi single-photon emission computed tomography prior to PTRA, during, and 2 days after the procedure. The last 30 patients received periprocedural abciximab (group A) and their results were compared to the remaining 45 patients (group B). For semiquantitative analysis, myocardial perfusion in 24 left ventricular regions was expressed as percentage of maximal sestamibi uptake. RESULTS: Baseline characteristics did not differ between the groups. Transient perfusion defects were observed in 39/45 (87%) patients of group B, but only in 10/30 (33%) patients of group A (p < 0.001). Perfusion was significantly reduced during PTRA in 3.3 +/- 2.5 regions in group B compared to 1.4 +/- 2.5 regions in group A (p < 0.01). Perfusion in the region with maximal reduction during PTRA in groups B and A was 76 +/- 15% and 76 +/- 15% at baseline, decreased to 56 +/- 16% (p < 0.001) and 67 +/- 14%, respectively, during PTRA (p < 0.01 A vs. B), and returned to 76 +/- 15% and 80 +/- 13%, respectively, after PTRA. Nine patients in group B (20%) and two patients in group A (7%) had mild creatine kinase and/or troponin t elevations (p = 0.18). Patients with elevated enzymes had larger perfusion defects than did patients without myocardial injury (4.2 +/- 2.7 vs. 2.3 +/- 2.5 regions, p < 0.05). CONCLUSIONS: These data indicate that GPIIb/IIIa blockade reduces incidence, extent and severity of transient hypoperfusion during PTRA. Thus, platelet aggregation may play an important role for PTRA-induced hypoperfusion. (+info)
Choroid plexus epithelial expression of MDR1 P glycoprotein and multidrug resistance-associated protein contribute to the blood-cerebrospinal-fluid drug-permeability barrier.
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The blood-brain barrier and a blood-cerebrospinal-fluid (CSF) barrier function together to isolate the brain from circulating drugs, toxins, and xenobiotics. The blood-CSF drug-permeability barrier is localized to the epithelium of the choroid plexus (CP). However, the molecular mechanisms regulating drug permeability across the CP epithelium are defined poorly. Herein, we describe a drug-permeability barrier in human and rodent CP mediated by epithelial-specific expression of the MDR1 (multidrug resistance) P glycoprotein (Pgp) and the multidrug resistance-associated protein (MRP). Noninvasive single-photon-emission computed tomography with 99mTc-sestamibi, a membrane-permeant radiopharmaceutical whose transport is mediated by both Pgp and MRP, shows a large blood-to-CSF concentration gradient across intact CP epithelium in humans in vivo. In rats, pharmacokinetic analysis with 99mTc-sestamibi determined the concentration gradient to be greater than 100-fold. In membrane fractions of isolated native CP from rat, mouse, and human, the 170-kDa Pgp and 190-kDa MRP are identified readily. Furthermore, the murine proteins are absent in CP isolated from their respective mdr1a/1b(-/-) and mrp(-/-) gene knockout littermates. As determined by immunohistochemical and drug-transport analysis of native CP and polarized epithelial cell cultures derived from neonatal rat CP, Pgp localizes subapically, conferring an apical-to-basal transepithelial permeation barrier to radiolabeled drugs. Conversely, MRP localizes basolaterally, conferring an opposing basal-to-apical drug-permeation barrier. Together, these transporters may coordinate secretion and reabsorption of natural product substrates and therapeutic drugs, including chemotherapeutic agents, antipsychotics, and HIV protease inhibitors, into and out of the central nervous system. (+info)