Effect of mitochondrial viability and metabolism on technetium-99m-sestamibi myocardial retention

This study investigated the mechanism of myocardial retention of technetium-99m-sestamibi.^99mTc-sestamibi was injected intravenously into guinea pigs, and the myocardium was homogenized and fractionated by differential centrifugation. More than 90% of myocardial^99mTc-sestamibi was localized within the mitochondrial fraction. Calcium was found to release^99mTc-sestamibi from the mitochondrial fraction, with an IC₅₀ of 2.54±0.98 mM. This effect was potentiated by NaCl, and inhibited by the mitochondrial calcium channel blocker ruthenium red. In vitro uptake of^99mTc-sestamibi was found to increase from 10.5% ± 3.0% to 61.2% ± 0.2% with the addition of 10 mM succinate, indicating that respiration is involved. Since irreversible ischemia results in cellular and mitochondrial calcium overload and loss of mitochondrial metabolic function,^99mTc-sestamibi should not be retained in necrotic or irreversibly ischemic myocardium, and could potentially act as a sensitive indicator of myocardial cell viability.     

Uptake and release of two new Tc-99m labeled myocardial blood flow imaging agents in cultured cardiac cells

Two new neutral lipophilic ^99mTc labeled molecules, chloro (methyboron (1-)-tris[1,2-cyclohexane-dionedioxime 91-)]-N,NNNN) (SQ 30217) and Bis [1,2-cyclohexanedione dioximato (1-)-0]-[1,2-cyclohexanedione dioximato (2-)-0] borato (2-N,NNNN) -chloro Tc (SQ 32014), were studied in cultures of beating myocardial cells of newborn rats. The uptake and release kinetics, the effects of various pH levels of the medium, and the effects of three metabolic inhibitors, i.e, ouabain, cyanide and iodoacetate were assessed. Results show that T_1/2 of uptake were 2 min with both tracers, and T_1/2 of release were 12 and 13 min with SQ 32014 and SQ 30217, respectively. The intra/extracellular tracer concentrations was about 15 times higher with SQ 30217 than with SQ 32014. Intracellular concentration was decreased for both tracers at high pH levels, and was only moderately modified otherwise, including in the presence of the metabolic inhibitors. It is concluded that both tracers present very interesting properties for myocardial blood flow imaging, although a higher contrast should be expected with SQ 30217 than with SQ 32014.     

Fission Mo-99/Tc-99m generators —A study of their performance and quality

Five ^99mTc-generators, based on fission Mo-99, from five different manufacturers were studied in April and May of 1977 — with regard to their performance and to the quality of the eluates. The study covers types of generators not already dealt with in a previous publication [5].One generator was overloaded with Mo-99; one generator had Tc-99m yields below 70%. One generator yielded eluates containing appreciable -emitting impurities other than Mo-99. Two generators yielded eluates containing trace amounts of Al⁺⁺⁺.The content of - and pure -emitting nuclidic impurities (other than Tc-99) were in all cases below the limits set in the DLS 79 [2] monograph on Tc-99m pertechnetate obtained from fission Mo-99.     

Technetium-99m tetrofosmin rest/stress myocardial SPET with a same-day 2-hour protocol: comparison with coronary angiography A Spanish-Portuguese multicentre clinical trial

Technetium-99m tetrofosmin (Myoview) has unique properties for myocardial perfusion imaging very early after injection of the tracer. We used a very short same-day rest/stress protocol, to be performed within 2 h and evaluated its diagnostic accuracy. The study included 144 patients from seven Spanish and four Portuguese centres with a diagnosis of uncomplicated coronary artery disease (CAD); 78 patients (54%) had no history of prior myocardial infarction. Patients were injected with 300 MBq^99mTc-tetrofosmin at rest and 900 MBq approximately 1 h later at peak exercise. Single-photon emission tomographic (SPET) acquisitions were initiated within 5–30 min post injection. The results were compared with those of coronary angiography (CA). The data of 142 patients were completely evaluable (two with non-evaluable images were excluded). The quality of rest images was excellent or good in 86%, regionally problematic in 7%, poor but well interpretable in 5% and non-evaluable in 2%. The overall sensitivity for the detection of CAD was 93%, the specificity 38% and the accuracy 85%. The localization of defects by SPET in relation to the perfusion territories of stenosed vessels (50%) was achieved with a sensitivity of 64% for the left anterior descending artery, 49% for the left circumflex artery and 86% for the right coronary artery, and an accuracy of 71%, 72% and 73% respectively. Concordance of SPET and CA was 62% for single-vessel disease and 68% for multivessel disease. In conclusion, this Spanish-Portuguese multicentre clinical trial confirmed, in a considerable number of patients who underwent coronary angiography, the feasibility of^99mTc tetrofosmin (Myoview) rest/stress myocardial SPET using a very short protocol (2 h).The results contained herein were presented in part at the 2nd International Conference of Nuclear Cardiology, held in Cannes, France, on 23–26 April 1995     

A single-strip mini-paper chromatographic method for rapid purity-control of 99mTc-labeled radiopharmaceuticals

A single-strip miniaturized paper chromatographic method (Mini-PC) was developed using 80%–90% acetone solvent for rapid purity-control of ^99mTc-radiopharmaceuticals. Routine ^99mTc-radiopharmaceuticals (eight kinds of kit made agents) and diluted agents (in which radiochemical impurities might be formed) were analyzed by Mini-PC and other methods. This showed that, compared with the other methods, the Mini-PC technique is useful for the simple and rapid routine analysis of radiochemical impurities of kit made ^99mTc-radiopharmaceuticals.     

Adenosine technetium-99m sestamibi single-photon emission tomography for the assessment of jeopardized myocardium early after acute myocardial infarction

This study investigated the value of technetium-99m sestarnibi scintigraphy in identifying patients at risk for post-infarct ischaemia (=jeopardized myocardium), especially within the reperfused infarct region. In 51 patients with a recent (99mTc-sestamibi single-photon emission tomography (SPET) and dobutamine stress echocardiography (DSE) were performed and correlated with the presence of significant coronary artery stenosis [% diameter stenosis (DS) >50%] on quantitative coronary angiography. Regional perfusion activity was analysed semiquantitatively (score 0–4) on a 13-segment left ventricular model. DSE was used for the estimation of the infarct size (low-dose DSE) and for concomitant evaluation of ischaemia (high-dose DSE). A reversible perfusion defect within the infarct region was observed in 20 of the 37 patients with a significant infarct-related lesion (sensitivity of 54%) and only in one patient without a significant infarct-related lesion (specificity of 93%). Further analysis revealed that the scintigraphic assessment of jeopardized myocardium was fairly good in patients with a moderate (DS 51%–64%) infarct-related stenosis but was inadequate in patients with a severe (DS65%) infarct-related stenosis (sensitivity of 80% vs 36%,P<0.01), while the echocardiographic detection of ischaemia was not influenced by stenosis severity (sensitivity of 73% in both subgroups). This scintigraphic under-estimation of jeopardized myocardium was mainly related to a severely impaired myocardial perfusion under baseline conditions, as was evidenced by a significantly more severe rest perfusion score in the infarct region in patients with a severe stenosis as compared to those with a moderate stenosis (average score: 1.5±0.7 vs 2.1±0.6,P<0.01), while infarct size on echocardiography was similar for both subgroups. It may be concluded that early after an acute myocardial infarction, adenosine^99mTc-sestamibi SPET may underestimate reperfused but still jeopardized myocardium, particularly in patients with a severe infarct-related stenosis. In these patients the evaluation of the ischaemic burden on rest-stress scintigraphy is hampered by the presence of a severely impaired myocardial perfusion in resting conditions.     

PET tomography in studies of distributions of 7.6-min potassium 38 in the dog heart

Potassium 38 emits a 2.68-MeV (max) positron, followed promptly by a 2.17-MeV -ray in 99.8% of its disintegrations. A positron is emitted also, followed by a 3.94-MeV -ray, in 0.2% of the decays. The pairs of 511-keV PET^±-quanta, which are emitted at 180±0.3° to each other, are in true coincidence with the prompt -rays emitted by the daughter nucleus, within the resolving time of PET instrumentation. Studies made with phantoms by means of a commercial version of the MGH PET camera demonstrated that quantitatively satisfactory images are derived, despite the presence of the prompt -rays. Two-dimensional (2-D) focal-plane images reveal high uptake of³⁸K promptly in the myocardium of dogs, under barbiturate sedation. Third-dimensional (3-D) transverse section PET tomographic images, through four 1.0-cm-thick heart slices orthogonal to the plane of the 2-D images and with 1.4-cm sequential spacing, show³⁸K uptake to be concentrated especially highly in the left ventricle, as expected. Peak levels of activity were observed over the myocardium at 12 s after intravenous bolus injection of ionic³⁸K. Dynamic mode 2-D images were taken at intervals as short as 0.5 s and extending to 1 h.     

Brain perfusion scintigraphy with99mTc-HMPAO or99mTc-ECD and123I-β-CIT single-photon emission tomography in dementia of the Alzheimer-type and diffuse Lewy body disease

Dementia of the Alzheimer-type (DAT) is characterized by progressive cognitive decline, variably combined with frontal lobe release signs, parkinsonian symptoms and myoclonus. The features of diffuse Lewy body disease (DLBD), the second most common cause of degenerative dementia, include progressive cognitive deterioration, often associated with levodopa-responsive parkinsonism, fluctuations of cognitive and motor functions, psychotic symptoms (visual and auditory hallucinations, depression), hypersensitivity to neuroleptics and orthostatic hypotension. A recent report suggests that positron emission tomography studies in patients with degenerative dementia may be useful in the differential diagnosis of DAT and DLBD. However, the diagnostic role of single-photon emission tomography (SPET) studies remains to be established. The aim of this study was therefore to evaluate regional cerebral perfusion [with either technetium-99m hexamethylpropylene amine oxime (^99mTc-HMPAO) or^99mTc-ethyl cysteinate dimer (^99mTc-ECD) SPET] and striatal dopamine transporter density [using iodine-123 2-carboxymethoxy-3-[4-iodophenyl]tropane (¹²³I--CIT) SPET] in patients with DAT and DLBD. Six patients with probable DAT and seven patients with probable DLBD were studied. Blinded qualitative assessment by four independent raters of^99mTc-HMPAO or^99mTc-ECD SPET studies revealed bilateral temporal and/or parietal hypoperfusion in all DAT patients. There was additional frontal hypoperfusion in two patients and occipital hypoperfusion in one patient. In the DLBD group, regional cerebral perfusion had a different pattern. In addition to temporoparietal hypoperfusion there was occipital hypoperfusion resembling a horseshoe defect in six of seven patients. In the DAT group, the mean 3-h striatal/cerebellar ratio of¹²³I--CIT binding was 2.5±0.4, with an increase to 5.5±1.1 18 h after tracer injection. In comparison, in the DLBD patients the mean 3-h striatal/cerebellar ratio of¹²³I--CIT binding was significantly reduced to 1.7±0.3, with a modest increase to 2.1±0.4 18 h after tracer injection (P<0.05, Scheffe test, ANOVA). These results suggest that^99mTc-HMPAO or^99mTc-ECD and¹²³I--CIT SPET may contribute to the differential diagnosis between DAT and DLBD, showing different perfusion patterns and more severe impairment of dopamine transporter function in DLBD than in DAT.     

Dose reduction in subsecond multislice spiral CT examination of children by online tube current modulation

The potential of online tube current modulation in subsecond multislice spiral CT (MSCT) examinations of children to reduce the dose without a loss in image quality is investigated in a controlled patient study. The dose can be reduced for oval patient sectional view without an increase in noise if the tube current is reduced where the patient diameter and, consequently, attenuation are small. We investigated a product version of an online control for tube current in a SOMATOM Sensation 4 (Siemens, Forchheim). We evaluated image quality, noise and dose reduction for examinations with online tube current modulation in 30 MSCT of thorax/abdomen and abdomen and compared mA s for tube current modulation to the mA s in standard weight-adapted children protocols. Image quality was rated as very good, good, diagnostic and poor in a consensus by three radiologists. Noise was assessed in comparison to 24 MSCT examinations without tube current modulation measured as SD in ROIs. The dose was reduced from 26 to 43% (mean 36%), depending on the patients geometry and weight. In general, no loss of image quality was observed. Measured noise showed a decrease up to 26% and an increase up to 36%, although there was no decrease of image quality. Online tube current modulation is now used as a standard in MSCT at our institution. Dose in MSCT examinations of children can be reduced substantially in routine examinations by online tube current modulation without a loss of image quality.     

Species and immunoglobulin preparation related effects on the biodistribution of technetium-99m-labelled immunoglobulin G in a baboon model

Technetium-99m-labelled immunoglobulin G (^99mTc-IgG) is a convenient and useful radio-pharmaceutical for the scintigraphic detection of inflammatory foci. However, unfavourable physiological biodistribution patterns such as high activities in the liver and especially in the kidneys impede the efficacy of this agent. This report describes biodistribution studies in the baboon model of various thiol reduction-mediated ^99mTc-labelled immunoglobulins, including human IgG preparations (Sandoglobulin and Sigma: -globulins prepared from Cohn fractions II and III) as well as baboon IgG preparations (Sigma: -globulins prepared from Cohn fractions II and III and IgG isolated from the serum obtained from specific animals). The biodistribution studies demonstrated differences in kidney concentration, i.e. human IgG (Sandoglobulin) > baboon IgG (cross-over animal experiments with IgG isolated from the serum of the different animals) > human IgG (Sigma) baboon IgG (Sigma)baboon IgG (own IgG isolated from the serum of a specific animal, labelled with ^99mTc and reinjected). Differences in liver concentration were also observed: human IgG (Sandoglobulin)<human IgG(Sigma)baboon IgG (Sigma)baboon IgG (own IgG)IgG (cross-over). Characteristic were the relatively high activities in the liver and kidneys compared to those in other organs with high blood supply, and a relatively high retention in the blood pool. The results indicate that the effect of the heterologous antibody system is insignificant. These studies also demonstrate the suitability of the baboon model for evaluation of ^99mTc-IgG preparations for scintigraphic purposes and suggest that damage to the Fc portion of the IgG molecule during Sandoglobulin preparation may be the cause of the high kidney accumulation of ^99mTc-Sandoglobulin.     

Pretargeting in tumored mice with radiolabeled morpholino oligomer showing low kidney uptake

We have recently shown that accumulation in mouse kidneys of technetium-99m labeled phosphorodiamidate morpholinos (MORFs) increases with the number of cytosines in the base sequence. To improve tumor/kidney ratios in tumored mice, pretargeting studies were performed with a cytosine-free MORF. An 18-mer MORF (5-TCTTCTACTTCACAACTA) was conjugated to the anti-CEA antibody MN14 (Immunomedics) and administered to nude mice bearing LS174T tumors. Thereafter, the ^99mTc-labeled cytosine-free cMORF (5-TAGTTGTGAAGTAGAAGA-amide-MAG₃) was administered. For comparison, the identical study was repeated but with our original pair of 18-mer MORFs (5-GGGTGTACGTCACAACTA-conjugated MN14 and ^99mTc-labeled 5-TAGTTGTGACGTACACCC-amide-MAG₃). Surface plasmon resonance was used to show that the hybridization affinities of the original and the modified pair of MORFs were essentially equal. Hybridization of the cytosine-free cMORF-^99mTc to MN14-MORF was demonstrated in vitro by size-exclusion high-performance liquid chromatography. At 3 h, kidney levels in normal mice were 2.0%ID/organ for the modified cMORF vs. 4.1%ID/organ for the original cMORF sequence, while at 24 h, these values were 0.9% vs 1.8%ID/organ. Pretargeting studies in tumored mice receiving 25 g of conjugated antibody, 0.5 g of labeled cMORF 48 h later, followed by imaging and sacrifice at 3 h showed that kidney levels were reduced using the cytosine-free cMORF. Moreover, tumor accumulation was about 3.6%ID/g and was independent of sequence. The whole-body images clearly reflected the improved tumor to kidney ratios. By choosing a cytosine-free base sequence for pretargeting studies, kidney accumulation of cMORF-^99mTc was reduced without adversely influencing tumor accumulation. The lowering of kidney radioactivity levels in this way may be important to reduce toxicity to this organ in connection with pretargeting radiotherapy studies.     

Bromine-82 contamination in fission product 99mTc-generator eluate

Following receipt of fission product ^99mTc-generators, results of radionuclide purity analysis, performed within 30 min after the first elution, demonstrated detectable levels of a contaminate radionuclide not previously reported. Gamma spectroscopy and half-life determinations confirmed the presence of ⁸²Br. Bromine-82 activity, in eluates from the first elution of 30 generators, received weekly during a 7-month period, ranged from 0.22 Ci (8.235 kBq) to 0.67 Ci (24.68 kBq) per eluate. The ratio of ⁹⁹Mo to ^99mTc ranged from 0.13 nCi to 0.39 nCi per mCi ^99mTc. The presence of ⁸²Br in ^99mTc-generator eluate resulted in falsely elevated ⁹⁹Mo assay determinations using whole vial ⁹⁹Mo assay procedures. For every 0.1 Ci ⁸²Br present in ^99mTc eluate the ⁹⁹Mo assay results were elevated by 1 Ci. Gamma spectroscopy of eluates from additional elutions of these generators failed to detect the presence of ⁸²Br demonstrating the displacement of monovalent bromine anions from the alumina column during the first elution.     

201Tl in the scintigraphic evaluation of the “cold” thyroid areas

²⁰¹Tl-chloride, which has a metabolic behaviour similar to that of potassium and cesium, has been used in 68 patients for the evaluation of thyroid nodules previously recognized as cold on ¹³¹I or ^99mTc scans.All patients were re-examined with gamma-camcra and/or sequential scintigraphic recordings during 60 min after i.v. administration of thallium. In some cases, simultaneous imaging and integral digital plot with ¹³¹I or ^99mTc and ²⁰¹Tl were performed.In all 12 malignant nodules, ²⁰¹Tl has showed a high uptake, while it did not concentrate in 47 benign nodules (cystic or macrofollicular adenomas); thallium uptake was nevertheless found in 10 solid neoformations in which histological pictures were negative for malignancy or atypical lesions.The computerized study of the ²⁰¹Tl intranodular concentration, with the analysis of its dynamic function curves, seems to offer further possibility in differentiating and in a more objective evaluation of the cold areas on the thyroid scan.     

Results of brain scanning with different radioisotopes (99mTc-PP, 99mTc-DTPA, 67Ga citrate)

Summary A comparison of the results obtained by ^99mTc-DTPA, ^99mTc-PP and ⁶⁷Ga-citrate scanning in ten meningioma patients is reported. The association of conventional brain scanning, bone scanning and tumor-positive scanning makes it possible to identify the primary tumor, its real extent, the perifocal damage and the contiguous bone damage.

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Ergebnisse der Hirn-Szintigraphie mit verschiedenen Substanzen

Zusammenfassung Die Verfasser vergleichen die abgegebenen Ergebnisse von ^99mTc-DTPA, ^99mTc-PP und ⁶⁷Ga-citrate bei 10 Patienten, von Meningiom befallen. Die Vereinigung der üblichen Hirn-Szintigraphie, der Knochen-Szintigraphie und der positiven Tumor-Szintigraphie erlauben die Identifizierung des ursprünglichen Tumors, seiner wirklichen Ausdehnung, des perifokalen Schadens und der angrenzenden Knochen-Veränderung.

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Etude comparative de la scintigraphie cérébrale avec differenis radio-elements (99^mTc-PP. 99^mTc-DTPA, 67 Ga citrate)Première partie: Etude des méningiomes

Résumé Les auteurs comparent les résultats de la scintigraphie cérébrale avec ^99mTc-DTPA, ^99mTc-PP et ⁶⁷Ga-citrate dans 10 cas de meningiome. L'association de la scintigraphie cérébrale conventionnelle, de la scintigraphie osseuse et de la scintigraphie néoplastique positive consent d'individualiser le foyer néoplastique, l'extension, le damage periphocale et l'altération osseuse concomitante.

     

Usefulness of different myocardial sampling zones for the postmortem diagnosis of myocardial infarction

Summary The diagnosis of myocardial infarction requires the use of a group of tests that are very efficient, quick and inexpensive. Another important consideration is the choice of myocardial sampling zones, especially in cases of differential diagnosis between a cardiac injury secondary to a trauma or violent asphyxia and others, secondary to myocardial infarction. The aim of this work was to choose, through discriminant analysis, the most useful zones of cardiac tissue for the quantification of free fatty acids and free carnitine and for the performance of the K/Na quotient, as biochemical parameters for the postmortem diagnosis of myocardial infarction. According to the discriminant analysis performed, seven zones of cardiac tissue are necessary to achieve a differential diagnosis among myocardial infarction, other natural deaths, and violent deaths with a 71.9% efficacy. Greater diagnostic efficacy was found (78.1%) for differentiating between natural deaths and violent deaths. Offprint requests to: E. Lachica     

Die besonderen konstruktionsmerkmale des japanischen „Tan-to“-(Messers) als Kriterien für dessen Gefährlichkeit

Zusammenfassung Es wird auf die besondere Klingenform japanischer Blankwaffen und auf die Neuentwicklung eines Verwandlungs-Tan-to verwiesen. Bei letzterem läßt sich die Klinge in der Handgriffmitte um 90° drehen und arretieren, eine ideale Fixierung dieses Messers durch Faustschluß am Quergriff. Durch diese Bedingungen ist eine hohe Verletzungsgefährdung mit tödlichem Ausgang gegeben. Diese seit kurzer Zeit im Handel erhältlichen Messer sollten nach § 37 Waff G umgehend als verbotene Gegenstände definiert werden.     

Three-dimensional display of myocardial perfusion detection of ischemic lesions using a new image subtraction method

A recent, commercially available computer program for the three-dimensional (3D) display of single-photon emission tomography (SPET) data was used to study myocardial perfusion in patients with coronary artery disease (CAD). To enable the detection of small ischemic lesions, the authors proposed a new distance-subtraction method: after suitable centering of the axial slices, 3D distance-shaded images of the stress study were subtracted from the corresponding views of the rest study. With this technique, small changes in surface-to-observer distance were highlighted, thus enabling us to detect nontransmural ischemic areas of the myocardium. General characteristics and possibilities of the subtraction technique were tested on a simple myocardial phantom. Some clinical results of the application of this method on CAD patients are presented and discussed. In CAD patients in whom only nontransmural ischemic lesions are present, the subtraction of distance-shaded images is decisive for a correct diagnosis.     

Survival benefit after revascularization is independent of left ventricular ejection fraction improvement in patients with previous myocardial infarction and viable myocardium

Purpose This study was designed to assess the relationships among myocardial viability, changes in left ventricular (LV) ejection fraction after coronary revascularization and long-term event-free survival in patients with previous myocardial infarction and LV dysfunction. Methods We studied 253 patients with previous myocardial infarction and evidence of dysfunctional viable myocardium as assessed by echocardiography and ^99mTc-sestamibi imaging. Coronary revascularization was performed in 142 patients, while 111 were medically treated. In revascularized patients, echocardiography was repeated 12 months later to detect LV ejection fraction improvement, defined as an increase of 5% compared with baseline. All patients were followed for a mean period of 52±29 months. Cardiac death and non-fatal myocardial infarction were considered as events. Results Event-free survival was higher in revascularized than in medically treated patients (P<0.001). Ejection fraction increased by 5% in 82 (58%) revascularized patients, and the extent of viable myocardium was the strongest predictor of such improvement (P<0.001). Event-free survival was similar for patients with (n=82) and patients without (n=60) LV ejection fraction improvement after revascularization, and it was better in revascularized than in medically treated patients in the presence of either substantial (5 viable segments) or low–intermediate (1–4 viable segments) viability (both P<0.01).Conclusion In patients with previous myocardial infarction and evidence of viable myocardium, coronary revascularization procedures improve outcome at long-term follow-up independently of LV ejection fraction improvement.     

Sodium bicarbonate-augmented stress thallium myocardial scintigraphy

It is well known that sodium bicarbonate in pharmacological doses induces transient alkalosis, causing intracellular transport of serum potassium. The aims of this study were (a) to investigate whether, in humans, myocardial thallium-201 uptake can be augmented by pretreatment with a single bolus of sodium bicarbonate at a pharmacological dose, (b) to verify general safety aspects of the intervention and (c) to evaluate the clinical implications of augmentation of ²⁰¹Tl uptake, if any. Routine exercise myocardial scintigraphy was performed twice in eight adult volunteers (five normal and three abnormal), once without intervention and the second time (within a week) following intravenous administration of sodium bicarbonate (88 mEq in 50 ml) as a slow bolus 1 h prior to the injection of ²⁰¹Tl. Conventional myocardial thallium study was compared with sodium bicarbonate interventional myocardial scintigraphy with respect to myocardial uptake (counts per minute per mCi injected dose), washout patterns in normal and abnormal myocardial segments, and overall clinical interpretation based on planar and single-photon emission tomographic (SPET) images. All patients remained asymptomatic after the intervention. A mean increase of 53% in myocardial uptake of thallium was noted in post-exercise acquisitions after the intervention, confirming uptake of the tracer via the potassium-hydrogen pump and its augmentation by transient alkalosis. The washout pattern remained unchanged. The visual quality of planar and SPET images improved significantly after the intervention. Out of the five abnormal myocardial segments identified in three cases, four showed significant filling-in after the intervention, causing the diagnosis to be upgraded from partial scar to ischaemia, or from ischaemia to normal. The overall scan impression changed in two out of three such cases. Sodium bicarbonate augmentation may have significant implications for stress-thallium scintigraphy and may be a new parameter for defining myocardial viability.     

The “water-ida”: A simple means to separate duodenal from gallbladder activity on cholescintigraphic studies

In some ^99mTc-iminodiacetic acid studies, separation of the gallbladder from the duodenum can be difficult, despite multiple views. When faced with this problem, we have had the patient ingest 250 cc of tap water. This ingestion clears the duodenum of activity and has allowed us to see the residual activity in the gallbladder. This waterida view may be a useful addition in difficult to interpret hepatobiliary studies.