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Biomedical subjects

A C Otto

Publications and source records attributed to A C Otto.

At least 19 recordsLinked to original sources
PubMed1997

Radiation dose estimates of 186Re-hydroxyethylidene diphosphonate for palliation of metastatic osseous lesions: an animal model study.

A common complication in patients with breast or prostate cancer is bone metastases causing pain. New radionuclide therapy methods have recently been proposed for palliation, including 186Re-hydroxyethylidene diphosphonate (186Re-HEDP). This paper reports on the local development of 186Re-HEDP and the biodistribution studied in animals for eventual use in patients. Adult dose was computed assuming a 70 kg standard man. The 186Re was labelled to HEDP using standard techniques. The biodistribution in five Chacma baboons (Papio ursinus) was studied. Doses ranging from 39.4 to 44.9 MBq kg(-1) (mean 43.6 +/- 2.8 MBq kg[-1]) were administered, corresponding to an adult human dose of 2960 MBq (80 mCi). Whole-body images of the animals were obtained with a dual-headed scintillation camera on an hourly basis for 6 h post-injection and then daily for 3 days. The bone, soft tissue, kidneys and urinary bladder were considered source organs and data from these organs were used in a compartmental model to obtain the mean residence times of the radionuclide in the different source organs. Radiation dose estimates for 186Re-HEDP were subsequently obtained with the MIRDOSE 3 program. The estimated absorbed radiation doses to some of the organs (expressed in mGy MBq[-l]) were as follows: bone surface 1.69; kidneys 0.09; liver 0.04; ovaries 0.04; red marrow 0.75; total body 0.12; urinary bladder wall 0.43. 186Re-HEDP yielded an effective dose of 0.17 mSv MBq(-1). The radiation dose delivered to the bone marrow in this study did not cause any detrimental effect to the baboons, indicating that locally produced 186Re-HEDP is suitable for clinical use.

Adult↗
PubMed1996

Evaluation of reflux oesophagitis with technetium-99m-labelled sucralfate.

UNLABELLED: Sucralfate binds with denuded protein to form a stable complex to protect the damaged mucosa. By utilising this property, technetium-99m-labelled sucralfate can be used to demonstrate ulceration in the upper gastro-intestinal tract. AIM: The aim of this study was to evaluate 99mTc-labelled sucralfate in the diagnosis of grade II-III reflux oesophagitis. METHODS: Ten patients with endoscopic proof of grade II-III reflux oesophagitis and 10 patients with normal findings on oesophagoscopy were evaluated after they had swallowed 5 ml 99mTc sucralfate. Radionuclide imaging was done until activity in the oesophagus had ceased. RESULTS: Retention of activity from 10 minutes up to 1 1/2 hours could be demonstrated in 9 patients with endoscopically proven oesophagitis. In the control group complete clearance of activity was seen in 7 patients. Gastro-oesophageal reflux could be demonstrated in 4 patients. CONCLUSION: In conclusion we found 99mTc sucralfate to be a sensitive and specific method for the non-invasive diagnosis of grade II or grade III oesophagitis when compared with endoscopy [corrected].

Adult↗
PubMed1995

The effect of exercise on normal splenic volume measured with SPECT.

In a study group of 20 healthy young men, splenic volume was determined with SPECT before and after exercise. A randomly chosen control group of 10 comparable men was studied similarly, but without exercise intervention. The mean splenic volume did not change significantly in the control group (i.e., from 292.9 ml to 282.1 ml [P = 0.75]). The mean splenic volume decreased 60.1 ml from 279.4 to 219.3 ml (21.5%) in the study group and this was highly significant (P = 0.01). Although exercise induced splenic autotransfusion is generally considered to be unimportant in humans, significant splenic contractility was observed with this technique. In the normal individual with a large spleen or with functional splenomegaly, the contractility response may become more important and can now be measured in a quick and easy manner.

Adolescent↗
PubMed1995

Determination of glomerular filtration rate with radionuclide renography and direct urinary activity quantitation.

OBJECTIVE: The direct urinary activity quantitation method is quick (approximately 40 minutes), requires only a single blood sample, is performed as part of standard renal scanning and shows high accuracy compared with 24-hour creatinine clearance. The purpose was to evaluate the practical application and accuracy of this technique at our clinic. DESIGN: Direct urinary activity quantitation was done in patients scheduled for routine radionuclide renography and compared to standard multiple-blood-sample techniques by means of Cr-51-EDTA and Tc-99m-DTPA. SETTING: Academic Medical Complex, Department of Nuclear Medicine, Universitas Hospital, Bloemfontein. PARTICIPANTS: Fifteen patients scheduled for routine radionuclide renography (glomerular filtration rate (GFR) determination) were voluntarily enrolled in the study. The GFRs of selected patients varied over a wide range. Possible obstructive uropathy was excluded. MAIN OUTCOME MEASURES: GFRs obtained by the direct urinary method were compared with GFRs determined by multisample Cr-51-EDTA and Tc-99m DTPA. RESULTS: GFRs from the direct urinary method compared with multisample Tc-99m-DTPA showed differences from -19.85 to 22.95 ml/min with a mean of 0.2 (+/- 12.25) ml/min (r = 0.93). When compared with multisample Cr-51 EDTA, differences ranged from -34.35 to 21.05 ml/min with a mean of -4.25 (+/- 16.08) ml/min (r = 0.90). CONCLUSION: The direct urinary activity technique is CONCLUSION: The direct urinary activity technique is easily applied and highly accurate compared with previous standardised multisample radionuclide techniques for determination of GFR.

Adolescent↗
PubMed1994

Difference between splenic volume measured at necropsy and that measured in vivo by radionuclide tomography.

Reference values for splenic volume used in this study are based on necropsy measurements made in 1970. Because the volumes (measured by radionuclide tomography) seemed to be consistently greater than the necropsy values, the splenic volume in 35 healthy male volunteers ranging in age from 18-30 years (median age, 21 years) was studied. Their mean (SD) splenic volume was 281 (73) ml compared with 138 (34) ml in the reference group. The mean splenic volume in healthy volunteers seems to be significantly greater than in cadavers, and these results suggest that reference range for splenic volume in vivo should be revised.

Adult↗
PubMed1994

Staff radiation doses during eight years in a nuclear medicine radiopharmacy.

It is important that staff radiation doses be kept 'as low as reasonably achievable' (ALARA). Staff working in the radiopharmacy and nursing staff responsible for injecting radionuclides are being monitored constantly in our department. We report here on the effective doses and doses to the hands received by staff at two hospitals during 8 years from January 1985 to December 1992. In addition to the doses determined monthly by the South African Bureau of Standards' Radiation Protection Service (SABS), radiation doses received to the hands and whole body were measured every week using lithium fluoride thermoluminescent dosimetry (TLD). The workload (number of patient studies each year) and the estimated amount of 99Tcm received per month were also established, and results have been expressed in relation to these where possible. The combined radiation doses and the absorbed dose per unit activity a single radiographer would have received, since 1988 when radiopharmacy duties were centralized, were calculated. The highest total radiation dose received in any one year by any one person at hospital A was 223.53 mSv to the hands, and 10.20 mSv and 8.37 mSv to the whole body depending on the dosimeter used. The corresponding values for hospital B were 54.05 mSv to the hands and 6.94 mSv and 4.43 mSv to the whole body. If only one radiographer should do all the work the calculated highest dose received would be 447.06 mSv to the hands and 9.68 mSv SABS effective dose.(ABSTRACT TRUNCATED AT 250 WORDS)

Humans↗
PubMed1993

Verification of a varying threshold edge detection SPECT technique for spleen volume: a comparison with computed tomography volumes.

SPECT enables quantitation of organ volume with radionuclide techniques using threshold edge detection methods. Previous phantom studies showed that a negative correlation exists between volume and threshold value. In those studies, the use of calibration curves were believed to correct for volume dependence on threshold values. The aim of this study was to evaluate the accuracy of spleen volume determination in 20 patients with SPECT by employing a varying threshold edge detection technique with volumes derived from CT. All patients had both radionuclide and CT examinations that were reconstructed with a filtered backprojection algorithm. During SPECT reconstruction, transverse slices were obtained with attenuation correction (Method A) and without attenuation correction (Method B). CT volumes were calculated from manually drawn regions of interest, whereas SPECT volumes were calculated with an automated algorithm using previously determined calibration curves. A confidence interval for calculated SPECT volumes also was calculated because of possible errors in the threshold value. The spleen volumes studied ranged from 91.2 ml to 1660.1 ml. Regression analysis yielded equations of CT = 0.97 SPECT + 7.07 (r = 0.996) and CT = 1.05 SPECT - 19.25 (r = 0.990) between CT and SPECT spleen volumes with a standard error of the y estimates of 31.10 ml and 54.47 ml, respectively. A mean percentage difference of 10.5% +/- 7.6% and 11.4% +/- 6.6% in spleen volume was obtained for Methods A and B in comparison with CT spleen volumes. The threshold value varied between 40.9% and 32.4% for Method A and between 41.2% and 28.5% for Method B because the spleen volume is increased. The varying threshold edge detection technique described in this paper can be implemented successfully in the clinical setting.

Adult↗
PubMed1991

Reference values for red cell survival times.

The first purpose of this investigation was to investigate in 35 young normal male subjects the use of the Dornhorst function and the weighted-mean method to calculate reference values for mean red cell survival time with and without correction for elution of 51Cr. We compared survival times calculated with the Dornhorst and weighted-mean methods with survival time estimated with linear or exponential models. Two methods to correct for elution of 51Cr from red cells were investigated. For the first method, correction factors were generated using the Dornhorst function fitted to mean survival curves obtained from the normal subjects. In the second method, the new Dornhorst rate constant method, the survival time, corrected for elution of 51Cr, was directly calculated from the experimental survival curve without applying correction factors. Correction for elution using the Dornhorst rate constant method was not successful and resulted in nonphysiologic values. The 95% confidence range of red cell survival time for reference subjects without correction for 51Cr elution was 37-74 days for the weighted-mean method and 37 to 73 days for the Dornhorst method. The 95% confidence range for normal subjects when the survival curves were corrected for elution was 47-179 days for the Dornhorst method and 58-161 days for the weighted-mean method. The poor results obtained with the Dornhorst rate constant method and the large 95% confidence range were due to the rapid and large variation in elution rate of 51Cr from red cells.

Adult↗
PubMed1990

[A comparison of three different techniques for measuring glomerular filtration rate].

The clearance of inulin, creatinine and radioactive tracers from the blood may be used to measure glomerular filtration rate (GFR). These techniques, however, are usually invasive and time-consuming. Although the clearance of a radioactive tracer is usually applied in nuclear medicine for the determination of GFR, it is also possible to convert the concentration of the tracer in the kidneys to absolute GFR by means of a regression equation. As this new technique is much faster, we have compared it with the conventional technique. A good correlation was found with the standard radionuclide techniques (r = 0.91), but the reference method was under-estimated on the average by 14 ml/min. The new regression equation derived in our clinic will ensure future accurate GFR measurements within 6 minutes.

Chromium Radioisotopes↗
PubMed1990

Detecting asymptomatic coronary artery disease using routine exercise testing and exercise thallium scintigraphy in patients with atherosclerotic vascular disease.

ECG-monitored exercise testing has been proposed as a relatively inexpensive and effective means of screening for asymptomatic coronary artery disease in patients presenting for peripheral vascular surgery. Despite the fact that exercise thallium scintigraphy is also dependent on the patient's ability to exercise, using this test in conjunction with ECG-monitored exercise testing may enhance sensitivity and specificity of non-invasive evaluation. Thirty-two patients were subjected to ECG-monitored exercise testing, exercise thallium scintigraphy and coronary angiography. The sensitivity of ECG-monitored exercise testing for detecting coronary artery disease was calculated at 81.8% and the specificity at 87.5%, while the figures for exercise thallium scintigraphy were 73.1% and 33.3% respectively. Using these two methods in combination yielded a predictive accuracy of 90.6%. The only advantage of exercise thallium scintigraphy over exercise ECG appears to be in patients in whom the latter test could not be interpreted or was non-diagnostic.

Adult↗
PubMed1990

A comparison of the clinical relevance of thallium-201 and technetium-99m-methoxyisobutyl-isonitrile for the evaluation of myocardial blood flow.

Thallium-201 is at present the radiotracer of choice for the clinical evaluation of myocardial blood flow. Although different technetium-99m-isonitrile agents have been synthesised recently, only 99mTc-methoxyisobutyl-isonitrile (99mTc-MIBI) has proved to hold promise for clinical implementation. The myocardial distribution of 201Tl and 99mTc-MIBI was compared in a group of 20 patients, who underwent both 201Tl single photon emission computed tomography and 99mTc-MIBI study as well as coronary angiography. The sensitivity for predicting a lesion ranged from 25% to 88% in different areas of the heart and was comparable for the two radiopharmaceuticals. The specificity was greater than 80% for all regions except the inferior region where a specificity of 58% obtained by 99mTc-MIBI was better than the low specificity of 17% obtained with 201Tl (P less than 0.008).

Angiocardiography↗
PubMed1989

Left ventricular myxoma. A case report.

A 27-year-old woman with a systolic ejection murmur caused by a left ventricular myxoma is described. The diagnosis of this potential fatal condition was made by echocardiography. The clinical differences between atrial and left ventricular myxoma are discussed.

Adult↗
PubMed1989

99mTc ethoxy methylpropyl isonitrile: a radioactive tracer for myocardial perfusion imaging.

The initial experience with a new 99mTc labelled myocardial perfusion agent, ethoxy methylpropyl isonitrile (EMI), is described in the primate as model. Rapid biliary clearance of EMI ensures low radionuclide concentration in the liver and lungs after 60 min. Adequate visualization of the myocardium is therefore possible. Heart-to-lung and heart-to-liver ratios of 1.52 and 2.45 respectively were obtained. EMI is an efficient imaging agent to evaluate myocardial ischemia and infarction.

Animals↗
PubMed1988

Daily serial evaluation of left ventricular function with equilibrium radionuclide ventriculography following thrombolysis during acute myocardial infarction.

The changes in ventricular function after reperfusion by coronary thrombolysis are important when deciding about further definitive treatment necessary to ensure long-term vessel patency. The purpose of this study was to evaluate the early changes in left ventricular function after reperfusion. Left ventricular function was serially evaluated for 10 days in a group of 18 patients receiving intracoronary thrombolytic therapy for an acute myocardial infarction. Comparison of the global ventricular function in the successfully and unsuccessfully reperfused groups of patients showed significantly better function in the successful group than the unsuccessful group after the first day, which was maintained for the entire study period. Global and regional ventricular function in the successfully reperfused patients showed significant early improvement during the initial 72 h with maintenance of this improvement for the study period of 10 days. In the patients in whom reperfusion was unsuccessful, regional ventricular function showed no change, while the global function declined from day 5 to day 8 of the study period. This study then confirms the significant improvement in ventricular function after successful reperfusion. The time course pattern of the change in ventricular function indicates that the most significant improvement occurs within the first 72 h after reperfusion. These changes are similar to those previously reported in experimental animals.

Angioplasty, Balloon↗
PubMed1988

Investigation into the effect of Fenoterol on mucociliary clearance in patients with chronic bronchitis.

We investigated the effect of Fenoterol, a selective beta 2 adrenoceptor stimulant, on mucociliary clearance in 12 patients with chronic bronchitis. Mucociliary clearance was measured with a scintillation camera after inhalation of a 99mTc labelled aerosol. Fenoterol was administered one h after acquisition commenced and imaging was maintained for a further two h. Three regions of interest (ROI) were selected over each lung to generate time activity curves. Corrections for decay, alveolar deposition (using 24 h image), cough and movement of activity through each ROI were carried out. An exponential function was fitted to the clearance curves to determine clearance rates. The increase in percentage clearance after Fenoterol administration for the left and right whole lung ROI was 35% and 36% per h respectively (P = 0.006 and 0.020). Fenoterol enhances cilial clearance in chronic bronchitis patients.

Adult↗
PubMed1988

The effects of nisoldipine on left ventricular filling rate in patients with ischemic heart disease measured with radionuclide gated blood pool scintigraphy.

Nisoldipine is a newly developed calcium channel blocker with outstanding vasodilatory properties especially with regard to the coronary arteries. Thus it may find wide-spread application as a therapeutic agent in various ischemic heart disease syndromes. The purpose of this study was to evaluate the effect of nisoldipine on the diastolic function of the left ventricle (LV) in the clinical situation. A patient group on nisoldipine treatment was compared to a control group. In the nisoldipine group a maximum decrease of 17 mmHg in the mean systolic blood pressure with an increase in the mean peak ejection rate (0.78 EDV/s) and peak filling rate (0.52 EDV/s) were observed. Mean LV ejection fraction increased by 6.4% and the time to peak filling rate decreased by 36.5 ms. After eight weeks of treatment the acute effects of nisoldipine were similar to the previous study. Nisoldipine therefore tends to improve both the diastolic and systolic function of the left ventricle.

Adult↗
PubMed1987

Absolute left ventricular volume changes after sublingual nitroglycerine and nifedipine intervention.

The haemodynamic effects of two vasodilators, sublingual nitroglycerine and nifedipine, on absolute end-diastolic volume, end-systolic volume, stroke volume (SV), heart rate, systolic blood pressure (SBP), cardiac output (CO) and corresponding cardiac indices were measured in two different groups, each consisting of 20 ischaemic heart disease patients, with gated blood pool scintigraphy. A control study was done in 5 ischaemic heart disease patients without intervention. Direct measurement of left ventricular (LV) volume was done by correcting LV activity for tissue attenuation utilising a geometric method. With nifedipine intervention only SBP (125.25 +/- 19.8 mmHg) showed a significant mean decrease (11 mmHg). The other measured parameters did not change significantly. With nitroglycerine all the parameters except LV ejection fraction showed significant changes. Mean CO decreased by 8% while mean SV decreased by 16%. The results in the control group showed excellent repeatability. The absolute haemodynamic changes of future cardiac drugs might easily be measured in vivo by this non-invasive technique.

Administration, Oral↗