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Biomedical subjects

A M Millar

Publications and source records attributed to A M Millar.

At least 19 recordsLinked to original sources
PubMed1997

Validation of a technique for the preparation of individual patient doses of 14C-urea.

A breath test employing 14C-urea is commonly used to detect the presence of Helicobacter pylori in the stomach of patients with peptic ulcer. 14C-urea is not available commercially as a radiopharmaceutical. It is available only as non-pharmaceutical grade material. A technique for preparing individual patient doses was therefore validated and methods for demonstrating the quality of the 14C-urea raw material and final product were developed. Individual patient doses, each containing 100 kBq 14C and 350 mg urea in 1 ml, were prepared and stored at -20 degrees C. Each batch consisted of approximately 400 doses. The activities of samples from each batch were measured by liquid scintillation counting immediately after preparation (99.6 +/- 4.9 kBq) and 6 months later (98.2 +/- 4.7 kBq). The chemical identity of the 14C-urea was demonstrated by a thin-layer chromatographic technique in which the 14C was shown to have the same Rf value as stable urea. The high radiochemical purity of the final product was demonstrated by the presence of only one peak on the thin-layer chromatogram. The radionuclide identity of the 14C-urea was demonstrated by beta-ray spectroscopy. This technique of preparing individual patient doses of 14C-urea results in a product that is stable for at least 6 months.

Breath Tests↗
PubMed1993

Effect of source and age of sodium pertechnetate Tc 99m on radiochemical purity of technetium Tc 99m exametazime.

The radiochemical purities of technetium Tc 99m exametazime prepared with one-hour-old or six-hour-old sodium pertechnetate Tc 99m from two manufacturers' generators were compared. Eluates from each manufacturer's generators were diluted immediately to provide two solutions of sodium pertechnetate Tc 99m. For the one-hour-old solution, eluate was diluted with 0.9% sodium chloride injection to a concentration of radioactivity of 38 mCi in 5.5 mL and used one hour later. For the six-hour-old solution, eluate was diluted to 65 mCi in 5.5 mL and used six hours later. Technetium Tc 99m exametazime was prepared by injecting 5.0 mL of one of the solutions into an exametazime kit to provide 30 mCi of technetium Tc 99m in 5.0 mL. At 2, 30, and 60 minutes after reconstitution of each kit, the radiochemical purity was measured by high-performance liquid chromatography with radiation detection. At two minutes, all the preparations retained high radiochemical purities. However, at 30 and 60 minutes, the radiochemical purities of technetium Tc 99m exametazime prepared with six-hour-old sodium pertechnetate Tc 99m were significantly lower than those of technetium Tc 99m exametazime prepared with one-hour-old sodium pertechnetate Tc 99m. Similar results were found for each manufacturer's generators. The radiochemical purity of technetium Tc 99m exametazime was affected by the age of the sodium pertechnetate Tc 99m from which it was prepared but not by the generator from which the sodium pertechnetate Tc 99m was obtained.

Humans↗
PubMed1992

A routine method for using sodium iodide to stabilize sodium pertechnetate [99Tcm] dispensed for the preparation of 99Tcm-exametazime.

When preparing 99Tcm-exametazime, it is important to use sodium 99Tcm-pertechnetate that is less than 2 h old. The addition of sodium iodide (NaI) to 99Tcm-pertechnetate is known to extend this time to 6 h. This paper describes a technique for implementing this in routine practice. Sterile kits consisting of 440 micrograms NaI and 1.0 ml sodium chloride injection in a vial with a nitrogen atmosphere were prepared and stored at room temperature, 4 degrees C and -22 degrees C. Titrimetric analysis of iodide showed that under each storage condition, kits were stable for 8 weeks. To determine the effectiveness of the kits, the radiochemical purity (RCP) of 99Tcm-exametazime was measured by high-performance liquid chromatography (HPLC). The validity of this technique was determined by simultaneous analysis with the conventional thin-layer/paper chromatography (TLC/PC) technique on 24 occasions, over a range of RCP (94.5-54.6%). Radiochemical purities measured by HPLC and TLC/PC were 81.2 +/- 10.2 and 81.5 +/- 10.5%, respectively, and did not differ significantly (P greater than 0.30). The correlation between the techniques was high (r = 0.98). 99Tcm-exametazime was prepared using 1 h-old 99Tcm-pertechnetate, 6 h-old 99Tcm-pertechnetate and 6 h-old 99Tcm-pertechnetate dispensed in a NaI kit. At the recommended expiry time for this radiopharmaceutical, i.e. 30 min after preparation, RCPs were found to be 88.4 +/- 2.4, 80.9 +/- 2.0 and 89.3 +/- 3.0%, respectively (n = 5 for each technique).(ABSTRACT TRUNCATED AT 250 WORDS)

Drug Stability↗
PubMed1990

An investigation of factors that might influence the radiochemical purity and stability of 99mTc-MAG3.

Technetium 99m mercaptoacetyltriglycine (99mTc-MAG3) was prepared from a commercial kit by various techniques to assess the effect of a number of variables on radiochemical purity and stability. Its radiochemical purity was determined by high performance liquid chromatography at 0 and 6 h after preparation and was found to be consistently greater than 95%. It has been demonstrated that the radiochemical purity of 99mTc-MAG3 prepared according to the manufacturer's instructions is not influenced by the volume of 99mTc generator eluate used, agitation, the presence of air in the reaction vial or the use of a 99mTc generator eluate with a 99Tc:99mTc ratio of 16:1. A modified method of preparation in which the MAG3 kit is reconstituted with saline before addition of 99mTc-pertechnetate has been shown to yield a satisfactory product and should help to minimise the radiation dose to the fingers of radiopharmacy staff.

Chromatography, High Pressure Liquid↗
PubMed1990

A comparison of cobalt (57Co) bleomycin scanning and contrast-enhanced CT scanning for assessment of the mediastinum in lung cancer.

Sixty patients with histologically proven lung cancer who had been accepted for mediastinoscopy or thoracotomy were prospectively entered into a study to evaluate computed tomographic (CT) scanning, 57Co-bleomycin scanning, and barium swallow in preoperative assessment of mediastinal lymph node metastasis. Fifty-six patients had thoracotomy at which all accessible lymph nodes were sampled. Twenty-four patients were found to have mediastinal tumor on histologic analysis of the resected mediastinal lymph nodes. Neither 57Co-bleomycin scanning nor barium swallow were clinically useful, with sensitivities of 21 percent and 11 percent respectively, whereas CT scanning was helpful. However, there was no clear cutoff point of node size to optimize sensitivity and specificity for CT scanning. When nodes greater than or equal to 15 mm were taken to indicate likely malignancy, the sensitivity was 58 percent and the specificity was 87 percent and when greater than or equal to 10 mm was used the sensitivity was 80 percent but the specificity was only 55 percent. There was no clear relationship between the size of the largest resected lymph node in each patient and the presence of malignant lymph nodes. Only 42 percent of patients with resected nodes greater than or equal to 2 cm had histologic evidence of metastases. We conclude that CT scanning should be used to indicate the presence and site of mediastinal lymph nodes, which, when visualized, should always be sampled and histologically examined prior to resection of primary tumor.

Aged↗
PubMed1990

99Tcm-MAG3: in vitro stability and in vivo behaviour at different times after preparation.

A kit for preparing technetium-99m mercaptoacetyltriglycine (99Tcm-MAG3), a new radiopharmaceutical for gamma camera renography, is available commercially. A drawback to the use of this kit is the recommended 1h expiry for 99Tcm-MAG3. This short expiry is a consequence of the possible growth of an impurity which undergoes hepatobiliary excretion and might interfere with renal imaging. Radiochemical purity of 99Tcm-MAG3 was measured by high performance liquid chromatography at 0, 1 and 6 h after preparation and was found to be consistently greater than 95. 99Tcm-MAG3 was shown to contain five impurities, one of which increased from 0.5% to 1% over 6 h. Dilution of 99Tcm-MAG3 eliminated this effect. A two-part clinical study was undertaken. For Part I, 99Tcm-MAG3 was prepared at 400 MBq/4 ml. For Part II, 99Tcm-MAG3 was prepared at 1 GBq/4 ml then subdivided and diluted to give single doses of 175 MBq/2.5 ml. In both parts, 10 patients were injected within 1 h after preparation and 10 were injected 5-6 h after preparation. From gamma camera images of the abdomen acquired 30 min after injection, the % injected 99Tcm in gall bladder and liver were calculated. In both parts, the % injected 99Tcm in gall-bladders and livers of the 1 h group were compared with those in the 5-6 h group and not found significantly different (p greater than 0.05). In conclusion, 99Tcm-MAG3 prepared according to the methods described, can be used up to 6 h after preparation.

Drug Stability↗
PubMed1989

Neutrophil activation during cell separation procedures.

Leucocytes labelled with 111In or 99Tcm are used as diagnostic agents for detecting sites of infection by scintigraphy. Before radiolabelling is performed, leucocytes are isolated from whole blood. The effect of isolation procedures on neutrophil activation has been studied by measuring the neutrophil elastase produced during incubation of whole blood with three erythrocyte sedimentation agents (dextran 70, hydroxyethyl starch and methylcellulose) and two density gradient media (Percoll and Mono-Poly Resolving Medium). Neutrophil elastase was measured using a standard radioimmunoassay. At 21 degrees C, dextran caused no elastase release while hydroxyethyl starch and methylcellulose induced significant release (p = 0.01 and p less than 0.01 resp.). All three agents caused significant elastase release at 37 degrees C. When whole blood was incubated with Percoll and Mono-Poly Resolving Medium, no release of neutrophil elastase was observed. These results show that neither density gradient medium induces neutrophil activation but that certain erythrocyte sedimentation agents do. Of the three sedimentation agents investigated, dextran is the agent of choice if neutrophil activation is to be minimized.

Cell Separation↗
PubMed1988

Effectiveness of acarbose, an alpha-glucosidase inhibitor, in uncontrolled non-obese non-insulin dependent diabetes.

The effect of acarbose, an alpha-glucosidase inhibitor, on glycaemic control, was compared with placebo in a double-blind, randomised, group comparison study during 16 weeks in 20 non-obese non-insulin dependent diabetic patients in whom sulphonylurea treatment had been withdrawn. There was significant deterioration in glycaemic control as assessed by HbA1 following withdrawal of the sulphonylurea. There was no significant improvement in HbA1 between weeks 0 and 16 in either the acarbose (11.3% and 12.4% respectively) or the placebo group (10.6% and 12.2% respectively). In both the acarbose and placebo treated groups fasting glucose and insulin concentrations were unaltered. This study also suggests that acarbose was not an effective substitute for sulphonylureas in non-obese Type 2 diabetes uncontrolled by diet alone.

Acarbose↗
PubMed1988

A reevaluation of an agent proposed for imaging oestrogen receptors: 17 alpha-[125I]-iodovinyl-11 beta-methoxyoestradiol-3-methyl ether ([125I]VMEME).

The metabolism of an iodinated steroid, 17 alpha-[125I]iodovinyl-11 beta-methoxyoestradiol-3-methyl ether ([125I]VMEME), previously proposed as a potential agent for imaging oestrogen receptor-containing tissues, has been studied and the conditions for synthesis and labelling redefined. It is confirmed that, although the compound does not itself have significant receptor-binding affinity, a metabolite is active. Because of its high solubility in fat and the consequential low contrast of small receptor-containing tumours, there is little prospect of successful early imaging of small axillary or internal mammary lymph node metastases from human breast cancer with this compound. Some more general implications of this finding are considered.

Animals↗
PubMed1987

The acute inflammatory response to myocardial infarction: imaging with indium-111 labelled autologous neutrophils.

The uptake of indium-111 labelled neutrophils was examined in 30 patients with acute myocardial infarction by planar imaging and single photon emission computed tomography. The time from venepuncture to reinjection of the autologous labelled neutrophils was less than 2.5 hours and imaging was carried out 24 hours later. Twenty three patients had a positive uptake of neutrophils in the myocardium and imaging was improved by single photon emission computed tomography. There was a significant difference between the intervals from the onset of chest pain to injection of labelled neutrophils between patients with positive and negative images; early reinjection was more likely to produce a positive image. Indeed, all nine patients reinjected within 18 hours of the onset of symptoms had positive images. The results suggest that the stimulus for activation and migration of neutrophils is transient; this is an important factor if neutrophil release products play a role in cell damage after coronary occlusion.

Acute Disease↗
PubMed1986

The preparation and in vivo behaviour of 111In-oxine labelled neutrophils separated from whole blood using mono-poly resolving medium.

using a single step separation procedure, we have developed a method for labelling human neutrophils with 111In-oxine. This method allows a rapid separation of neutrophils from whole blood, with negligible mononuclear or red cell contamination. Preliminary studies using 111In-labelled neutrophils show minimal lung retention and early accumulation in the spleen consistent with viable cells. In addition, focal accumulation of 111In has been imaged in patients with localized inflammation or sepsis.

Cell Separation↗
PubMed1985

A comparison of the economics of xenon 127, xenon 133 and krypton 81m for routine ventilation imaging of the lungs.

We have compared the cost of providing routine lung ventilation scintigraphy using 127Xe with other radioactive gases in 100 patients. The physical properties of 127Xe permit a logical imaging sequence where a ventilation study is only carried out if indicated by perfusion scintigraphy which is performed first. With 133Xe, all patients must be ventilated prospectively, or a preselection carried out based on radiographic appearances at the time of imaging. This results in a greater number of ventilation studies than with 127Xe. Despite the greater cost per study of 127Xe, the overall cost of providing a routine diagnostic service with this gas is no more than that of using 133Xe in selected patients. The cost of ventilating all patients prospectively with 133Xe is considerably greater than using 127Xe only when indicated by abnormal perfusion images. If ventilation imaging is to be available at all times, either isotope of xenon costs very much less than 81Krm. We conclude that 127Xe is the radiopharmaceutical of choice for routine lung ventilation scintigraphy.

Costs and Cost Analysis↗