99mTc-MIBI stress-rest myocardial perfusion scintigraphy in patients with complete left bundle branch block.

BACKGROUND: Patients with complete left bundle branch block (LBBB) often show a false-positive ischaemic pattern in the interventricular septum on thallium-201 (201TI) stress-rest myocardial perfusion scintigraphy. Equivocal results have been reported with technetium-99m labelled hexakis-methoxyisobutyl isonitrile (99mTc-MIBI) in such patients. The aim of this retrospective study was to determine the effect of LBBB on the septal uptake of 99mTc-MIBI during stress-rest single photon emission computed tomography (SPECT) scintigraphy. METHODS: We studied 75 consecutive patients with LBBB, referred for 99mTc-MIBI stress-rest SPECT. Studies were evaluated by visual analysis using a semi-quantitative grading technique. In all patients with abnormal septal segments, the presence or absence of ischaemic heart disease was confirmed either clinically or by means of angiographical examination. RESULTS: Forty-three patients (57.3%) had completely normal studies. Only 15 (20%) had septal abnormalities (11 with reversible and 4 with fixed defects), while 17 patients (22.7% had abnormal segments in areas other than the interventricular septum. Except for 1 patient lost to follow-up, ischaemic heart disease was confirmed in all the patients with septal changes. CONCLUSION: We conclude that 99mTc-MIBI is more specific than 201TI for identifying ischaemic heart disease in the presence of LBBB.

Brain uptake of iodine-131 metaiodobenzylguanidine following therapy of malignant pheochromocytoma.

Intracranial metaiodobenzylguanidine (MIBG) uptake is occasionally and only faintly visualized on diagnostic studies. Recently, intense normal cerebellar uptake was described on posttherapy MIBG images. Experience at the University of Michigan with posttherapy MIBG scintigraphy of pheochromocytoma was reviewed. The patterns and correlates of intracranial uptake after therapeutic 1-131 MIBG in 25 patients (61 patient treatment encounters) were evaluated by review of records and blinded consensus interpretation of diagnostic and posttherapeutic MIBG scans. Thirty-nine (64%) patient treatment encounters demonstrated at least faint (grade 1) MIBG uptake in one or more brain sites; the most common site was the cerebellum. There was a statistically significant relation between intracranial uptake and 1) size of therapeutic dose and 2) patient age, but no relation between intracranial uptake and gender, body mass index, plasma epinephrine level, plasma norepinephrine level, urine metanephrine level, or the therapy-to-imaging interval. Although the influence of age on the pattern and intensity of intracranial uptake is unexplained, the relation to therapy dose may be explained by the possible generation of MIBG metabolites that can cross the blood-brain barrier (high activity administered and the delay until imaging). Further studies are needed to define mechanisms of intracranial uptake and relation to responses and toxicity after MIBG therapy of neuroendocrine tumors.

Imaging infection and inflammation in an African environment: comparison of 99Tcm-HMPAO-labelled leukocytes and 67Ga-citrate.

A considerable segment of the population of South Africa has a disease spectrum similar to those of the industrialized countries. However, a much larger proportion of its inhabitants comes from historically disadvantaged communities and is plagued by diseases typical of the developing world. Infectious diseases head the list as a cause of mortality in certain age groups. We have studied 108 patients presenting with a wide array of infections. Fifty-eight patients were examined with 67Ga-citrate and with 99Tcm-HMPAO-labelled leukocytes, 40 with leukocytes alone and 10 who had a high pre-test probability of tuberculosis with 67Ga only. The sensitivity and specificity of 99Tcm-labelled leukocyte scintigraphy in the 58 patients who had both studies were 89 and 84%, respectively, while the corresponding values for 67Ga scintigraphy were 81 and 74%, respectively. The overall sensitivity and specificity for 99Tcm-labelled leukocytes for detecting inflammatory sites in all 98 cases were 92 and 89%, respectively. Although labelled leukocytes were the better of the two agents for the early diagnosis of infections with a high probability of neutrophil infiltration, 67Ga remains an excellent alternative. It is the first choice in patients in whom tuberculosis or a neoplastic process is suspected as a cause of fever. It is also safer to use in areas where labelling of leukocytes is inadvisable because of inadequate sterility or where the risk is high of infecting other patients or staff with HIV.

Analysis of radiation doses received by the public from 131I treatment of thyrotoxic outpatients.

Radiation doses to the family and general public from 131I therapy of outpatients were assessed for comparison with the 1990 International Commission on Radiation Protection (ICRP) dose limits. Doses to family members of such patients, measured by previous workers, were converted to show that on average 5.6 +/- 3.7 microSv MBq-1 is received by the spouse and 1.5 +/- 0.87 microSv MBq-1 by other family members. It was deduced that the average dose to the spouse (D microSv MBq-1) when couples sleep apart for T days after administration is given by: D = 2.528 + 3.072e-0.11T if an effective half-life, T(eff), of 6.35 days is used. The cumulative effect of repeated treatments should be considered and in view of ALARA it is recommended that couples sleep apart for at least 14 days after each administration, even if this is below limits permitted by authorities. The dose to a pregnant colleague or family member other than the wife should be below 2 mSv if the total administered activity is not more than 600 MBq. If the wife is pregnant, couples should sleep apart for at least 30 days after administration.

Splenic regeneration and phagocytic function after partial splenectomy in baboons.

Total splenectomy, especially in children, results in diminished ability to combat infection by capsulated bacteria. It is, however, uncertain how much splenic tissue is needed to maintain this ability. In this experimental study on baboons, in situ remnants after partial splenectomy were examined to evaluate regeneration and phagocytic function after injection of dual-labelled liposomes into their splenic arterial supply. The results showed that resection of as much as two-thirds of the spleen in baboons allowed sufficient regeneration to support adequate macrophage phagocytic function.

[Preoperative special tests and intraoperative arterial oxygen partial pressure during one-lung ventilation]. / Preoperatiewe spesiale ondersoeke en intraoperatiewe arteriële suurstofspanning tydens eenlongnarkose.

The value of preoperative lung function tests was examined in 11 patients as a method to predict changes in intraoperative PaO2 (dPaO2) during one-lung ventilation in pulmonary surgery. Ventilation (Kr-81m and Xe-133) and perfusion (Tc-99m microspheres) to the lung to be operated upon significantly predicted the intra-operative decrease in PaO2. The correlation between ventilation percentage to the diseased lung and dPaO2 was 0.87 (SEE = 9.99) and between perfusion and dPaO2 0.84 (SEE = 9.51).

Biodistribution of 131I-radiolabelled plasma low density lipoprotein in hyperlipidaemic vervet monkeys.

Low density lipoprotein (LDL) labelled with 131I has been administered to 6 Vervets 2 of which were high responders to an atherogenic Western diet in terms of plasma cholesterol, 2 were low responders and 2 were fed a high carbohydrate control diet. The ratio of hepatic to cardiac activity was recorded for up to 10 days after administration of the labelled LDL. Liver activity had a longer biological half life in the high-responders and this can be interpreted in terms of a variation of hepatic metabolism of LDL, with direct relevance to the human situation.

The technetium-99m DTPA partition test in the diagnosis of tuberculous meningitis.

Although the blood/cerebrospinal fluid (CSF) bromide concentration ratio is sensitive and specific in the diagnosis of tuberculous meningitis (TBM), bromide-82 is not always available since it is not generally used in nuclear medicine. The use of technetium-99m diethylenetriamine penta-acetic acid (DTPA) for a partition test was compared with that of 82Br in 22 cases. Seven patients were diagnosed as having TBM, 9 patients had viral meningitis and 5 patients had septic meningitis. One normal control subject was also studied. Although the mechanism of transfer of substances across the blood-brain barrier as well as the factors affecting it are still unclear, both 82Br and 99mTc-DTPA cross the blood-brain barrier to a greater extent in TBM than in viral meningitis. Both tracers thus yield decreased serum/CSF concentration ratios in TBM. The accuracy of the 82Br partition test was found to be 90,9% if a critical serum/CSF ratio of 1,3 was chosen, compared with 86,9% for the 99mTc-DTPA partition test if a critical value of 3 was chosen. The use of 99mTc-DTPA offers various advantages, including general availability, lower cost and radiation dose per MBq, as well as the possibility of concomitant brain scintigraphy.

Optimisation of density and contrast yielded by multiformat photographic imagers used for scintigraphy.

The maximum optical density (MOD) and contrast (characterised by an effective gamma, gamma eff) yielded by multiformat photographic imagers used for scintigraphy, was determined by densitometry of a computer image, which consisted of a pattern of uniform squares containing known counts. A series of clinical scintigrams were photographed using various MOD and gamma eff values, and were graded by three experienced clinicians. It was found that a MOD of 1.6 and a gamma eff of 2.9 yielded optimal images for general use if bone scintigrams are also to be photographed. Lesion detectability in phantom images using extreme MOD and gamma eff values that were still clinically acceptable was determined. At very low false-positive rates (less than or equal to 1%) the higher gamma eff yielded a significantly greater lesion detectability (p = 0.02) at an information density of 2200 counts cm-2 in accordance with White-head's theory. It is concluded that quantification and optimisation of density and contrast factors are important and that the technique described enables quality control of multiformat imagers with respect to these factors.

Ventilation-perfusion imaging in evaluating regional lung function in nonpenetrating injury to the chest.

The extent of chest wall and lung injury after nonpenetrating injury to the chest (NIC) determine how aggressive and invasive management modalities should be. We investigated the value of ventilation (133Xe) and perfusion (99mTc) studies as indicators of extent of lung injury in 28 patients with moderate to severe unilateral NIC. The ventilation-perfusion (V/Q) abnormalities were compared with parameters conventionally used to evaluate NIC. All studies were carried out within 24 h of NIC and repeated 24 h later. Ventilation (p less than 0.001) and perfusion (p less than 0.01) abnormalities were more extensive soon after NIC than suggested by chest roentgenograms. Chest x-ray film changes lagged behind V/Q changes on admission and also after 24 h. The extent of ventilation, perfusion, and chest x-ray film abnormalities on admission were all predictors of increased morbidity. V/Q studies may be useful to define the extent as well as the changes in regional lung function following NIC.

The elimination of errors caused by prior technetium-99m scintigraphy on iodine-131 thyroid uptake measurements.

Coincidence summing of technetium-99m (99mTc) pulses may disturb iodine-131 (131I) thyroid uptake measurements if these are obtained after 99mTc thyroid scintigraphy performed on the same day. The magnitude of the error was assessed in 26 patients. It was found that when pre-dose measurements were subtracted, the 6-hour and 24-hour 131I uptakes could be falsely decreased by up to 137 percentage points using a lower discriminator level of 250 keV and by up to 35 percentage points with a discriminator level of 300 keV. When pre-dose measurements from 99mTc were ignored, there was a general increase in 131I uptake values at 6 hours. Increases of up to 22 and 9 percentage points occurred when 250 keV and 300 keV lower discriminator levels respectively were used. These errors may be eliminated by performing 131I uptake measurements through a 1 mm lead filter.

Mitral subannular left ventricular aneurysm. A case report.

A mitral subannular left ventricular aneurysm in an Ovambo man is described. This condition should be suspected in patients of negroid descent presenting with mitral incompetence and a localised bulge on the left heart border on chest radiography. Mitral and aortic subannular aneurysms are discussed, including the diagnostic use of ECG gated cardiac blood pool imaging.

Systemic lupus erythematosus with coronary vasculitis and massive myocardial infarction. A case report.

A 32-year-old white woman presented with angina pectoris and an acute myocardial infarction (MI) complicated by congestive cardiac failure. Other symptoms and results of immunological investigation were highly suggestive of systemic lupus erythematosus (SLE). Thallium-201 scintigraphy confirmed an extensive MI, as initially suspected from an ECG. Cardiac catheterization delineated a poorly contracting left ventricle secondary to MI. Selective coronary angiography showed features suspicious of coronary arteritis involving the left anterior descending and left circumflex coronary arteries. Right ventricular endomyocardial biopsy failed to show any 'small-vessel disease', vasculitis or myocarditis. We suggest that the acute MI was caused by coronary arteritis due to SLE. Overview of the literature indicates that coronary arteritis is not as rare a complication of SLE as previously believed; however, acute MI is most unusual.

[The effect of heparin induced increase of free plasma thyroxine on cardiac rhythm after myocardial infarction]. / Die effek van heparien-geïnduseerde styging in vrye plasmatiroksien op die hartritme na miokardiale infarksie.

It is well known that an acute myocardial infarction is accompanied by a rise in levels of plasma free fatty acids (FFA), which may lead to a subsequent increase in cardiac arrhythmias. Administration of heparin to patients after an acute myocardial infarction gives rise to an increase both in plasma FFA levels and plasma free thyroxine levels. If administered without a fatty meal the rise in FFA is not accompanied by an increase in arrhythmias. The effect of the heparin-induced rise in plasma free thyroxine on cardiac rhythm has never been investigated. The aim of the present study was to investigate a possible arrhythmic effect of a heparin induced increase in plasma free thyroxine in a group of patients with acute myocardial infarction. We were able to confirm a significant heparin-induced rise in plasma free thyroxine levels, as measured by the effective thyroxine ratio. Although a slightly significant increase in ventricular premature beats could be demonstrated after heparin administration when using the Wilcoxon rank sum test for statistical analysis (but not when the paired t-test was utilized), no significant correlation with free thyroxine levels could be found. Heparin administration to patients suffering from myocardial infarction seems to be safe in terms of a possible arrhythmic effect.

[Study of space-occupying lesions in the liver using technetium-99m tin colloid and indium-113m chloride]. / Ondersoek van ruimteopnemende letsels in die lewer met tegnesium-99m-tinkolloïed en indium-113m-chloried.

Liver scanning with radiocolloids is an important method to determine the presence, the position and the size of space-occupying lesions in the liver. Unfortunately, this information is nonspecific and it is not possible to distinguish between tumours, abscesses or cysts. Thirty-six patients in whom a definite diagnosis of hepatoma, amoebic liver abscess or echinococcus cyst had been made were examined with technetium-99m tin colloid and indium-113m chloride. The amoebic liver abscesses were avascular, showed a hyperaemic area surrounding the abscess and appeared smaller on the indium than on the technetium scan. The hepatomas showed greater vascularity and absence of the hyperaemic area. Cysts were avascular, did not show a hyperaemic rim and the size was equal on both scans. The experience of the observers had an influence on the accuracy of interpretation of the scans; experienced observers made a correct diagnosis in 73% of cases. It is suggested that simultaneous 99mTc tin colloid and 113mIn-chloride scans provide additional specificity in the differential diagnosis between hepatoma, amoebic liver abscess and echinococcus cysts.

Hepatobiliary scintigraphy in surgical patients.

Hepatobiliary scintigraphy as an investigative procedure has a definite role in the investigation of the surgical patient with various biliary problems. As it outlines the functional anatomy of the biliary tract, it has been employed for some time in the diagnosis of acute cholecystitis. In addition, it has a place in the investigation of patients with chronic cholecystitis, common bile duct obstruction and biliary leaks and in evaluating the integrity of biliary bypass procedures.

The role of kidney uptake of Tc-99m pertechnetate during quantitation of gastric scintigraphy.

It is shown that during quantitative gastric scintigraphy with Tc-99m pertechnetate significant errors may occur if kidney uptake is ignored. The magnitude of the error was assessed in 12 patients, and could lead to an over-estimation of gastric uptake by up to 20%.