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PubMed1992

Comparison between thallium-201, technetium-99m-sestamibi and technetium-99m-teboroxime planar myocardial perfusion imaging in detection of coronary artery disease.

Technetium-99m-sestamibi (MIBI) and 99mTc-teboroxime (TEBO) are two new myocardial perfusion imaging agents. The purpose of this prospective study was to compare MIBI and TEBO to 201TI planar imaging. Eighteen patients with significant coronary artery disease on coronary angiogram were submitted to three treadmill stress tests performed within 3 mo and were imaged with the three radiopharmaceuticals as follows. 1. TI: 2.2 mCi, immediate and delayed views (4 hr later, 8 min/view). 2. TEBO: 15-20 mCi at stress (1 min/view) and a second injection was repeated 4 hr later at rest (20-25 mCi). 3. MIBI: 15-18 mCi at stress (8 min/view) and 1-4 days later, 15-18 mCi at rest. Patients achieved similar levels of exercise. A blinded reading was performed by three observers. The left ventricle was divided into three segments/view and ischemic/normal wall ratios were also determined. Segmental comparison showed an agreement in 85% (138/162) of the segments between TI and TEBO, in 92% (149/162) between TI and MIBI and in 84% (136/162) between MIBI and TEBO. Abnormal TI, MIBI and TEBO studies were seen in 16 (89%), 16 (89%) and 15 (83%) patients, respectively, detecting 77, 75 and 65 abnormal segments. Ischemic-to-normal wall ratios were 0.75 +/- 0.06, 0.73 +/- 0.08 and 0.78 +/- 0.08 for TI, MIBI and TEBO, respectively. In conclusion, although the biologic characteristics of these agents are different, this study showed a good correlation between them in detection of significant coronary artery disease (high pretest likelihood population).

Aged↗

PubMed1991

Rapid preparation and quality control method for technetium-99m-2-methoxy isobutyl isonitrile (technetium-99m-sestamibi).

Technetium-99m-2-methoxy isobutyl isonitrile (99mTc-sestamibi) is a radiopharmaceutical that can be useful in the evaluation of patients with acute myocardial infarction. The current method for preparation requires a lengthy boiling water bath procedure and the recommended quality control procedure is cumbersome and time-consuming. Using a microwave oven, the heating time necessary to provide a labeling efficiency (averaging 97% for sestamibi-labeled with maximum allowable 99mTc activity and volume has been reduced to 10 sec. A new mini-paper chromatography (MPC) system has been developed to analyze the radiochemical purity of 99mTc-sestamibi involving a 1:1 chloroform/tetrahydrofuran developing solvent. The recommended thin-layer chromatography (TLC) system involving the use of an AI2O3-coated plate requires an average time for drying and development of 34.8 +/- 1.6 min (n = 58) to complete, whereas the new MPC system has an average developing time of 2.3 +/- 0.1 min (n = 26). For radiochemical purity values ranging from 71-99% (n = 31), the MPC and TLC methods correlated closely (r = 0.99) with a regression line of MPC% = 1.05 TLC%--5.75. The combined use of the microwave oven heating method and our quick quality control system will facilitate the rapid, emergency use of 99mTc-sestamibi and eliminate the need for advance preparation of multiple kits each day.

Chromatography, Paper↗

PubMed1990

Comparison of methods for calculating glomerular filtration rate: technetium-99m-DTPA scintigraphic analysis, protein-free and whole-plasma clearance of technetium-99m-DTPA and iodine-125-iothalamate clearance.

True glomerular filtration rate (GFR) was measured in normal volunteers and in patients with normal and impaired renal function by the iothalamate clearance (IC) method of Sigman. Within 24 hr, GFR was also determined by two other methods: technetium-99m- (99mTc) DTPA scintigraphic analysis (SA) utilizing a modification of the Gates computer program, and by measuring disappearance of 99mTc-DTPA from whole plasma (WPC) and from protein-free ultrafiltered plasma (PFPC). Determinations of GFR by IC and by PFPC methods were virtually identical (mean absolute error 5.36 ml/min, r = 0.99, p greater than 0.05). GFRs measured in protein-free, ultrafiltered plasma differed significantly from those obtained from whole plasma only in sicker patients and in those taking multiple medications (in whom alterations in protein-binding of DTPA may be seen). The SA method correlated less well with the iodine-125-(125I) IC method than did either the protein-free or whole-plasma clearance methods (mean absolute error 32.36 ml/min, r = 0.74, p less than 0.05). However, the SA method provided useful information with respect to differential (split) renal function.

Adult↗

PubMed1978

Characterization of tin-technetium colloid in technetium-labeled albumin preparations.

The Tc-99m human serum albumin (HSA) system has been reinvestigated with gel filtration as the assay method. Other than Tc-99m HSA, two radioactive components have been isolated by this technique. Both components are tin-technetium colloids of differing particle sizes, and the relative quantity of each one is pH-dependent. The colloid has been further characterized by protein-induced x-ray emission analysis (PIXE) and by tissue distribution in rats. By this gel-filtration method, commercial Tc-99m HSA kits have been evaluated and have revealed varying amounts of colloids present.

Animals↗

PubMed1978

Clinical comparison of cardiac blood pool visualization with technetium-99m red blood cells labeled in vivo and with technetium-99m human serum albumin.

Technetium-99m red blood cells (Tc-RBC) labeled by an in vivo technique were compared with two preparations of Tc-99m human serum albumin (HSA) for cardiac blood-pool imaging. Relative distribution of the tracers was analyzed on end-diastolic frames of gated blood-pool studies and on whole-body (head to mid-thigh) anterior pinhole images. The Tc-RBC demonstrated greater relative percentage localization in the cardiac blood pool, higher target-to-background ratios in the left ventricle, and less liver concentration. For cardiac blood-pool imaging, Tc-RBC labeled by the in vivo approach appears to be superior to the two Tc-HSA preparations studied.

Cardiac Volume↗

PubMed1995

Clinical comparison of technetium-99m-EC, technetium-99m-MAG3 and iodine-131-OIH in renal disorders.

UNLABELLED: Technetium-99m-ethylenedicysteine has recently been developed for renal function studies. The pharmacokinetics of 99mTc-EC were studied by constant infusion technique and compared with 99mTc-MAG3 and 131I-OIH in 11 patients with various renal disorders. METHODS: After giving a 7.4 MBq 131I-OIH and 90-110 MBq 99mTc-EC or 99mTc-MAG3 bolus, a constant infusion (1MBq/ml 99mTc-agent and 0.07 MBq/m 131I-OIH was started. Sixteen blood and five urine samples were obtained over three hr. RESULTS: The renal clearance of 99mTc-EC was higher than that of 99mTc-MAG3. The 99mTc-EC/OIH and 99mTc-MAG3/OIH ratios were 0.75 +/- 0.05 and 0.55 +/- 0.10 (p = 0.00087), respectively. The distribution volume of 99mTc-EC was also higher than that of 99mTc-MAG3 (15722 +/- 4644 and 9509 +/- 2788 ml/1.73m2, respectively; p = 0.072). The 99mTc-EC/OIH and 99mTc-MAG3/OIH distribution volume ratios were 1.03 +/- 0.14 and 0.55 +/- 0.10, respectively (p = 0.0003). The 60-min excretion values of 99mTc-EC and 99mTc-MAG3 were compared to that of OIH. The 99mTc-EC/OIH and 99mTc-MAG3/OIH excretion ratios were 0.96 +/- 0.06 and 1.07 +/- 0.10, respectively (p = 0.162). The protein binding of 99mTc-EC and OIH were found to be 34% +/- 4 and 66% +/- 5, respectively (p < 0.0001). The red cell binding of 99mTc-EC was negligible (3% +/- 1.2) in comparison to OIH (27% +/- 3; p < 0.0001). CONCLUSION: This limited study demonstrates the pharmacokinetic and renal clearance properties of 99mTc-EC. This agent has good potential for renal function evaluation.

Adolescent↗

PubMed1994

Evaluation of technetium-99m-L,L-EC in renal transplant recipients: a comparative study with technetium-99m-MAG3 and iodine-125-OIH.

UNLABELLED: The clinical usefulness of kit-formulated 99mTc-L,L-EC, a new renal tubular tracer agent based on a diaminodithiol ligand was evaluated in a large population of renal transplant recipients. METHODS: Fifty patients with transplants were studied. Five patients with renal insufficiency and five normal volunteers were also included to extend the range of renal function values. The labeling efficiency of 99mTc-L,L-EC in routine conditions, i.e., without HPLC purification, and the safety of the tracer were evaluated. RESULTS: The mean radiochemical purity of 99mTc-L,L-EC determined by thin-layer chromatography was 97.4%. No side effects or significant biochemical changes were observed. The clearance of 99mTc-L,L-EC and 125I-OIH ranged from 10.7 to 417.5 and from 27.6 to 602.7 ml/min/1.73 m2, respectively. The clearance of 99mTc-L,L-EC and 99mTc-MAG3 averaged respectively 71% and 52% of that of 125I-OIH. CONCLUSION: The labeling procedure of kit-formulated 99mTc-L,L-EC is easy and efficient. This tracer is safe and suitable for both imaging and quantitative measurement of the renal tubular function. Technetium-99m-L,L-EC represents an excellent alternative to 99mTc-MAG3.

Adult↗

PubMed1994

Technetium-99m-N,N-ethylenedicysteine--a comparative study of renal scintigraphy with technetium-99m-MAG3 and iodine-131-OIH in patients with obstructive renal disease.

UNLABELLED: Technetium-99m-labeled N,N-ethylenedicysteine (99mTc-EC) is a new renal imaging agent introduced as an alternative for 99mTc-labeled mercaptoacetyltriglycine (99mTc-MAG3), with similar renal excretion characteristics. To evaluate the diagnostic characteristics of this agent, a gamma camera study was performed. METHODS: Sixteen patients with obstructive renal disease and six normal controls were injected with 90 to 110 MBq of 99mTc-EC and 7.4 MBq 131I-labeled orthoiodohippurate (OIH). Serial images were obtained during 20 min for 99mTc-EC and 30 min for OIH. The study was repeated using 90 to 110 MBq 99mTc-MAG3 during the same week. RESULTS: Renograms, functional ratios and urinary excretion patterns of all three agents were similar. The mean time to peak activity values for OIH, 99mTc-EC and 99mTc-MAG3 were 4.25 +/- 0.37 min, 4.39 +/- 0.32 min and 4.00 +/- 0.24 min, respectively. The time from peak to 50% activity values for OIH, 99mTc-EC and 99mTc-MAG3 were 5.48 +/- 0.80 min, 6.93 +/- 0.69 min and 7.33 +/- 0.85 min, respectively. CONCLUSION: It is concluded that 99mTc-EC has excellent imaging characteristics and similar excretion properties to OIH. The advantages of 99mTc-EC over 99mTc-MAG3 are lower hepatobiliary uptake and simplicity of preparation.

Adult↗

PubMed1993

Technetium-99m-HMPAO-labeled leukocytes and technetium-99m-labeled human polyclonal immunoglobulin G in diagnosis of focal purulent disease.

To evaluate the usefulness of 99mTc-HMPAO-labeled leukocytes and 99mTc-labeled polyclonal human immunoglobulin G (Technescan HIG) in the diagnosis of focal purulent disease, 31 comparative scintigraphies were done in 30 patients with known or strongly suspected focal infection. Focal purulent disease was the final diagnosis in 19 patients. Technetium-99m-labeled leukocytes showed 16 true-positive, no false-positive, 11 true-negative and 3 false-negative findings. The corresponding figures for 99mTc-labeled HIG were 11, 2, 9 and 8. The sensitivity and specificity of imaging with labeled leukocytes were 84% and 100%, respectively, and with labeled HIG, 58% and 82%, respectively. The overall accuracy of the leukocyte scan was significantly better than that of the HIG scan (90% versus 67%, p < 0.001). Thus, if focal infection is suspected, scintigraphy with 99mTc-labeled leukocytes is the preferable method. No cases exhibited a better imaging result with 99mTc-HIG scintigraphy than with 99mTc-labeled leukocytes.

Female↗

PubMed1996

Uptake of technetium-99m-tetrofosmin, technetium-99m-MIBI and thallium-201 in tumor cell lines.

UNLABELLED: We investigated the kinetics, cellular uptake and intracellular distribution of 99mTc-tetrofosmin in tumor cell lines and compared them with those of 99mTc-MIBI and 201TI. METHODS: At specific intervals after incubation with radiotracers, cellular uptake was determined. Cells were also treated with nigericin, carbonyl cyanide m-chloro-phenylhydrazone (CCCP) and ouabain to determine their effects on the uptake of the tracers. RESULTS: Each tracer showed similar uptake kinetics in both cell lines, and a steady-state was maintained for at least 4 hr. Nigericin stimulated the uptake of both 99mTc-tetrofosmin and 99mTc-MIBI in HBL-2 cells, although it inhibited their uptake in SW-13 cells. Nigericin also inhibited 90% of 201TI uptake in both cell lines. Addition of CCCP caused 73%-97% release of accumulated 99mTc-MIBI from both cell lines with or without nigericin pretreatment, indicating that most of the accumulated 99mTc-MIBI was related to mitochondria. The effect of CCCP on accumulated 99mTc-tetrofosmin was less marked than that on 99mTc-MIBI in both cell lines, indicating that only a part of accumulated 99mTc-tetrofosmin, was related to mitochondria. Ouabain preincubation inhibited 74%-77% and 51%-53% of 201TI uptake in HBL-2 and SW-13 cells, respectively, as well as inhibited 22%-31% uptake of 99mTc-tetrofosmin in both HBL-2 and SW-13 cells. Uptake by the dead cells of either cell line was negligible for each tracer. CONCLUSION: Technetium-99m-tetrofosmin uptake depends on both cell membrane and mitochondrial potentials. Only a small fraction of 99mTc-tetrofosmin accumulates inside the mitochondria, while most 99mTc-MIBI accumulates inside the mitochondria. Thallium-201 uptake is partly independent of the Na+, K+ pump.

Carbonyl Cyanide m-Chlorophenyl Hydrazone↗

PubMed1996

Comparison of technetium-99m-HMPAO and technetium-99m-ECD cerebral SPECT images in Alzheimer's disease.

UNLABELLED: SPECT has shown increasing promise as a diagnostic tool in Alzheimer's disease (AD). Recently, a new SPECT brain perfusion agent, 99mTc-ethyl cysteinate dimer (99mTc-ECD) has emerged with purported advantages in image quality over the established tracer, 99mTc-hexamethylpropyleneamine oxime (99mTc-HMPAO). This research aimed to compare cerebral images for 99mTc-HMPAO and 99mTc-ECD in discriminating patients with AD from control subjects. METHODS: Twenty-four AD patients (mean age +/- s.d. = 68.9 +/- 8.2 yr) and 13 healthy subjects (68.4 +/- 8.0 yr) were scanned sequentially with 20 mCi of each tracer using the CERASPECT system within 1 mo. Scanning began on average 11.5 +/- 2.8 min after 99mTc-HMPAO injection and 41.8 +/- 10.1 min after 99mTc-ECD. A ratio, R, was derived of count densities in "typically affected" brain structures (parietal and temporal association cortices) to "unaffected" structures (cerebellum, basal ganglia, thalamus, occipital cortex, and sensorimotor cortex). RESULTS: Analysis of variance revealed significant interaction between diagnostic group and radiopharmaceutical (F = 4.71; df = 1.35; p = 0.04), with 99mTc-ECD demonstrating better separation of R values between AD patients and control subjects than 99mTc-HMPAO. Receiver operating characteristic (ROC) analysis, revealed no significant difference in the ability of the two tracers to correctly classify AD patients and control subjects. Both tracers showed high diagnostic accuracy (99mTc-ECD: sensitivity = 100%, specificity = 92%; 99mTc-HMPAO: sensitivity = 100%, specificity = 85%). CONCLUSION: Technetium-99m-ECD shows greater contrast than 99mTc-HMPAO between affected and unaffected brain structures in AD when patients are compared to age-matched control subjects. Both tracers perform equally well in correctly classifying patients and control subjects.

Aged↗

PubMed1997

Myocardial technetium-99m-tetrofosmin and technetium-99m-sestamibi kinetics in normal subjects and patients with coronary artery disease.

UNLABELLED: This study was designed to compare the tracer kinetics between 99mTc-sestamibi and 99mTc-tetrofosmin in a heterogeneous group of 24 patients admitted for routine perfusion imaging. METHODS: Twelve patients were studied with 99mTc-tetrofosmin and 12 with 99mTc-sestamibi. In each group, six patients had a low likelihood for coronary artery disease, and six patients had angiographically proven coronary artery stenoses of > 75% or previous myocardial infarction. Analysis of myocardial and liver uptake and clearance as well as target-to-organ contrasts were performed with planar stress images. RESULTS: Myocardial uptake of 99mTc-tetrofosmin was higher from 5 min (0.37 +/- 0.12 counts/pixel x MBq-1, p = 0.008) to 60 min (0.32 +/- 0.10 counts/pixel x MBq-1, p = 0.04) compared to 99mTc-sestamibi. Biological half-life for 99mTc-tetrofosmin (278 +/- 32 min) in normal myocardium was significantly shorter (p = 0.008) than for 99mTc-sestamibi (680 +/- 45 min). Biological liver half-life for 99mTc-tetrofosmin (67 +/- 16 min) was also significantly shorter (p = 0.02) than for 99mTc-sestamibi (136 +/- 18 min). Heart-to-lung ratios for 99mTc-tetrofosmin (2.49 +/- 0.43 at 5 min to 2.66 +/- 0.55 at 60 min) and 99mTc-sestamibi (2.52 +/- 0.37 at 5 min to 2.95 +/- 0.50 at 60 min) were similar. Whereas heart-to-liver ratios for 99mTc-tetrofosmin (1.04 +/- 0.24 at 5 min, increasing to 1.51 +/- 0.44 at 60 min) were significantly higher from 30-60 min postinjection (p = 0.05 at 30 min to p = 0.02 at 60 min) compared to the 99mTc-sestamibi (0.83 + 0.16 at 5 min to 1.08 +/- 0.27 at 60 min). CONCLUSION: Technetium-99m-tetrofosmin displays a shorter myocardial half-life compared to 99mTc-sestamibi. The rapid liver clearance of 99mTc-tetrofosmin, combined with comparable myocardial retention, resulted in higher heart-to-liver ratios but similar heart-to-lung contrasts compared to 99mTc-sestamibi from 30-60 min.

Coronary Disease↗

PubMed1997

SPECT imaging of normal subjects with technetium-99m-HMPAO and technetium-99m-ECD.

UNLABELLED: Technetium-99m-HMPAO and 99mTc-ECD have been used for regional cerebral blood flow (rCBF) studies using SPECT. However, details of the normal perfusion patterns of these agents still remain to be clarified. HMPAO-SPECT and ECD-SPECT images of normal individuals were investigated using an anatomical standardization technique. METHODS: Twenty healthy subjects participated in this study. In 10 of these, regional cerebral perfusion was measured with HMPAO, and in the other 10, ECD was used. All SPECT images were globally normalized to 50 counts/voxel, and then, each SPECT image was transformed into a standard brain anatomy format with the aid of x-ray CT of each subject and a computerized human brain atlas system (HBA). Mean and s.d. images for each tracer were calculated on a voxel-by-voxel basis. For comparison of these SPECT images with blood flow, rCBF images were generated using PET in a separate group of 10 healthy male subjects during an eyes-closed resting state. The PET images were globally normalized to 50 ml/100 g/min and anatomically standardized using each subject's MRI and the HBA for the SPECT images. RESULTS: In the HMPAO-SPECT images, relatively high radioactivities Were observed in the basal ganglia and cerebellum. In the ECD-SPECT images, high levels were observed in the medial aspect of the occipital lobe. These regions with high radioactivity were not apparent in the rCBF-PET images. CONCLUSION: While both HMPAO and ECD have been used to investigate rCBF, their perfusion patterns differ from rCBF-PET images. This presumably reflects differences in the mechanism of accumulation of each agent in the brain. For clinical diagnoses, these patterns must be taken into consideration.

Adult↗

PubMed1997

Intra-individual differences between technetium-99m-HMPAO and technetium-99m-ECD in the normal medial temporal lobe.

UNLABELLED: Regional distributions of 99mTc-hexamethyl propyleneamine oxime (99mTc-HMPAO) and 99mTc-ethyl cysteinate dimer (99mTc-ECD) were compared in the normal brain. METHODS: Six paid, healthy volunteers (mean age 26 yr) had high-resolution neuroperfusion SPECT using both 99mTc-HMPAO and 99mTc-ECD on separate days. RESULTS: Regional distribution of the two tracers differed. Technetium-99m-HMPAO accumulated more in the thalamus, frontal lobe, temporal lobe and cerebellum than 99mTc-ECD, which accumulated more in the occipital and parietal lobes. There was a considerable difference in the accumulation of the two tracers in the medial temporal lobe. The percent accumulations of 99mTc-HMPAO and 99mTc-ECD in the medial temporal lobe compared with the mean global cerebral cortical accumulation were 93.9% +/- 2.4% and 83.1% +/- 4.1% (mean +/- s.d.), respectively. CONCLUSION: The results suggest that 99mTc-HMPAO and 99mTc-ECD require specific and separate criteria for diagnosing temporal lobe pathologies, such as dementia and temporal lobe epilepsy.

Adult↗

PubMed1997

Acquisition protocol for breast cancer imaging with technetium-99m-labeled synthetic peptide and technetium-99m-MDP.

UNLABELLED: Technetium-99m-MDP and, recently, a 99mTc-labeled synthetic decapentapeptide have been shown to localize in breast lesions. Our goal was to develop an acquisition protocol to improve image quality, to improve detection of axillary lymph nodes with disease and to compare the utility of the new radiotracer to 99mTc-MDP. METHODS: Ninety-three patients with documented breast carcinoma were studied. Thirty-eight patients were studied in the supine position with anterior and lateral views: eight patients were injected intravenously with 600-740 MBq 99mTc-EPPT and 30 patients with the same activity of 99mTc-MDP. A second group of 55 patients was studied using the same total activity: 20 patients were injected with 99mTc-EPPT and 35 patients with 99mTc-MDP. To improve results, patients were positioned standing up with their arm raised. The breast with a marker over the nipple touched the collimator in the oblique-lateral position. Early planar images (2-5 min postinjection) were acquired with this positioning for the healthy and the tumor breast, collecting 1500 K counts in a 256 x 256 matrix. Imaging of the axillary regions was performed while the patients were positioned supine and a frontal image was obtained at 10-15 min postinjection for 1800 K counts. RESULTS: This diagnostic study produced good quality images, with the breast lesions and axilla visualized. The positions had limitations due to the overlapping of other organs and to the proximity with the chest wall. CONCLUSION: Using this protocol, all primary lesions and 50% of the axillary lymph nodes with 99mTc-MDP, and 35% with 99mTc-EPPT, were detected as documented by histology. Our protocol may represent an improvement in the diagnosis and staging of breast cancer.

Axilla↗

PubMed1997

Technetium-99m-HMPAO, technetium-99m-ECD and iodine-123-IMP cerebral blood flow measurements with pharmacological interventions in primates.

UNLABELLED: Technetium-99m-bicisate ethyl cysteinate dimer (ECD) presents a different pattern from cerebral blood flow (CBF) in the subacute phase of cerebral infarction, as measured by PET, perhaps due to lack of oxygen and enzyme activity; this pattern is contrary to that of hexamethyl-propyleneamine oxime (HMPAO) but similar to that of N-isopropyl-[123I]beta-iodoamphetamine ([123I]IMP). This study explores possible CBF differences among HMPAO, ECD and IMP, with various relevant drug interventions. METHODS: Anesthetized adult baboons were used in these SPECT studies. Four studies (n = 6 baboons for each study), one control study and three intervention studies involving intravenous acetazolamide, nimodipine infusion and intramuscular sumatriptan, were followed with 99mTc-HMPAO, 99mTc-ECD and [123I]IMP. The split-dose method was used as follows. For each tracer, intervention data from the second SPECT (SPECT-2) after the second tracer injection (444 MBq) reflected a change in CBF with respect to the baseline SPECT (SPECT-1) data from the initial injection (222 MBq). These changes as a ratio, R (R = SPECT-2/SPECT-1), for each study, and the R values for each tracer were compared to R values from the corresponding control studies, yielding a quantitative estimate of drug effects. RESULTS: There were no significant differences (p > 0.05) between HMPAO and ECD for the control, acetazolamide and sumatriptan studies, but there was indeed a difference between the two for the nimodipine study, indicating a nimodipine-dependent underestimation of CBF with ECD (and also with IMP), with respect to HMPAO. A further significant difference was that larger CBF increases were observed with acetazolamide, as measured with [123I]IMP. CONCLUSION: This is a crucial observation for the clinical interpretation of CBF SPECT data and should direct the choice of tracer for a specific examination.

Acetazolamide↗

PubMed1998

Discordance of technetium-99m-HMPAO and technetium-99m-ECD SPECT in herpes simplex encephalitis.

UNLABELLED: Technetium-99m-hexamethyl propyleneamine oxime (HMPAO) and 99mTc-ethyl cysteinate dimer (ECD) accumulate in brain tissue in proportion to regional cerebral blood flow in healthy subjects and in patients with a variety of neurological diseases. We report on four patients with herpes simplex encephalitis and the discordance between these two approved cerebral perfusion imaging radiopharmaceuticals. CONCLUSION: SPECT images showed unilateral regional increase of 99mTc-HMPAO uptake and decrease of 99mTc-ECD uptake in the affected temporal lobe.

Brain↗

PubMedDate not supplied

Reduced variability of interpretation and improved image quality with a technetium 99m myocardial perfusion agent: comparison of thallium 201 and technetium 99m-labeled tetrofosmin.

BACKGROUND: The purpose of this study was to determine the relative image quality and interobserver variability among four readers for 201Tl and 99mTc-labeled tetrofosmin myocardial perfusion images. 99mTc-labeled perfusion agents, with near-optimal physical characteristics for gamma camera imaging, may allow for superior image quality and improved consistency of interpretation. However, most studies to date have demonstrated only similarity in the diagnostic accuracy between technetium agents and thallium. Tetrofosmin is a recently developed 99mTc-labeled agent that has shown promising results in early clinical trials. METHODS AND RESULTS: A multicenter, open-label trial was performed during which treadmill exercise thallium and tetrofosmin scintigraphy was performed within a 2-week period of each other in 216 subjects. Image quality was evaluated subjectively and scans were interpreted in a blinded, independent fashion by four readers. Perfusion abnormalities were graded as consistent with ischemia, infarction, or mixed and were described both globally and regionally. Interobserver variability was assessed by use of the kappa statistic, and receiver-operator curves were compared for each observer for the diagnostic accuracy of each agent. More tetrofosmin images were of excellent quality than with thallium (52% vs 28%; p < 0.05), and when differences in quality were noted between the agents, tetrofosmin was more often superior (p < 0.0001). The interobserver variability was lower with tetrofosmin scintigraphy because generally higher kappa values were noted, especially in the lateral wall. Higher receiver-operator curve areas indicative of improved diagnostic accuracy were noted among the four readers for tetrofosmin in 80% of vascular territories. CONCLUSIONS: 99mTc-labeled tetrofosmin scintigraphy yields images of improved quality compared with thallium, and there is an overall improvement in the consistency of image analysis associated with the use of tetrofosmin.

Coronary Disease↗