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Biomedical subjects

M J O'Doherty

Publications and source records attributed to M J O'Doherty.

At least 19 recordsLinked to original sources
PubMed1992

Pulmonary nuclear medicine.

This article reviews the contribution made by nuclear imaging to the assessment, diagnosis and monitoring of patients with respiratory disease. It focuses on several specific areas including the diagnosis of pulmonary embolism, the investigation of intrapulmonary infection and neoplasm and the role of positron emission tomography (PET) scanning.

HIV Seropositivity↗
PubMed1992

Preparation and stability of a radioiodinated pentamidine isethionate analog.

Iodopentamidine isethionate was heated for 70 min with [I-123]- or [I-125]-sodium iodide and ammonium sulphate in the absence of solvent at 140 degrees C. The product, [I-123]- or [I-125]-iodopentamidine isethionate, was purified by ion exchange chromatography. It was stable at room temperature in aqueous solution over several days, in human blood in vitro for at least 24 h (showing no binding to either cells or proteins), in urine over at least 15 h, and during nebulization in both ultrasonic and jet nebulizers.

Aerosols↗
PubMed1992

Ulcerative colitis developing after amoebic dysentery in a haemophiliac patient with AIDS.

Severe diarrhoea in patients with the acquired immune deficiency syndrome (AIDS) is usually a manifestation of gastrointestinal infection by a variety of organisms. We report a patient with low CD4 T cell counts who developed ulcerative colitis after amoebic dysentery. He subsequently developed acute ulcerative colitis with toxic dilatation while he was severely immunocompromised. He responded to corticosteroids and mesalazine and remains well on maintenance therapy.

Acquired Immunodeficiency Syndrome↗
PubMed1992

Delivery of a nebulized aerosol to a lung model during mechanical ventilation. Effect of ventilator settings and nebulizer type, position, and volume of fill.

Several factors may affect the delivery of a nebulized aerosol to the lung through an endotracheal tube during mechanical ventilation. To study these factors in vitro, a model representing ventilation of an adult patient was constructed by linking a Servo 900C ventilator to a standard humidified circuit and an endotracheal (ET) tube positioned within a pipe representing the trachea. This was connected via a filter to a lung simulator. Nebulizers filled with 99mTc human serum albumin were positioned in the circuit, and the delivery of nebulized aerosol through the ET tube into the filter was measured using a gamma camera. With the use of an inspiratory phase-activated System 22 Acorn jet nebulizer, typical adult ventilator settings, and a 3-ml nebulizer solution volume, 5.4% of the nebulizer dose reached beyond the end of the ET tube. This was increased by increasing the inspiratory time, reducing the respiratory rate or respiratory minute volume, and by repositioning the nebulizer on the inspiratory limb of the Y-piece and was reduced by slowing the driving gas flow to the nebulizer. Under the same conditions, delivery was 3.1 and 4.4% using the Samsonic and Fisoneb ultrasonic nebulizers, respectively. Increasing the fill volume and the addition of an aerosol storage chamber increased delivery with all three nebulizers. These experiments suggest some simple ways of improving aerosol delivery during mechanical ventilation, including increasing the volume of nebulizer fill, repositioning the nebulizer in the ventilator circuit, adding an aerosol storage chamber, and adjusting ventilator settings to maximize delivery.

Adult↗
PubMed1992

123I-methylene blue: an unsatisfactory parathyroid imaging agent.

This study was designed to examine the possible use of 123I-labelled methylene blue as a parathyroid imaging agent. Five patients were studied, all of whom had parathyroid adenomas which were successfully localized preoperatively with 201Tl and 99Tcm-sestamibi, and which were subsequently proven at surgery. The 123I-labelled methylene blue localized only one of these adenomas, was negative in two and had equivocal uptake in the remaining two patients. It is therefore concluded that compared to other radionuclide methods for localizing parathyroid adenomas this agent is unsatisfactory.

Adenoma↗
PubMed1992

Parathyroid imaging with technetium-99m-sestamibi: preoperative localization and tissue uptake studies.

The accepted radionuclide method for imaging abnormal parathyroid tissue has been the combined use of [99mTc]pertechnetate 201Tl-chloride. Various problems with this approach, however, have suggested the need for an improved parathyroid imaging agent. This study examined the use of 99mTc-sestamibi as a parathyroid imaging agent compared with 201Tl-chloride. Fifty-seven patients were scanned with both 99mTc-sestamibi and 201Tl preoperatively. There were 40 adenomas, of which 37 were localized with 201Tl and 39 with sestamibi. Fifteen patients had hyperplastic glands, of which 29 glands were localized with 201Tl and 32 with sestamibi. Possible differences in uptake of the two agents by thyroid and parathyroid tissue were examined by administering 10 MBq of each agent to patients undergoing surgical exploration and biopsy. Preoperatively 20 patients were studied (13 adenomas and 7 with hyperplasia). Thallium-201 uptake was higher in both the parathyroid and thyroid tissue than sestamibi. However, the uptake per gram of parathyroid tissue of sestamibi was higher than the uptake per gram of thyroid tissue. This was not true for 201Tl. Technetium-99m-sestamibi was at least as effective as 201Tl in parathyroid localization. This may be partly due to a higher target-to-background ratio, but also to the superior physical characteristics of 99mTc.

Adenoma↗
PubMed1991

Variability in the measurement of nebulized aerosol deposition in man.

1. This study was performed to determine the variability of two different scintigraphic methods of measuring pulmonary aerosol deposition, and to examine nebulizer particle size and drug output as potential sources of this variability. 2. A radioaerosol was produced from a 3 ml solution of 99mTc-labelled colloidal human serum albumin (0.05 mg, 37 MBq) using a standard jet nebulizer and air compressor. This was inhaled on three separate occasions by nine healthy male subjects. One one of these occasions, a further inhalation was performed to assess immediate repeatability using increased 99mTc activity (92 MBq). 3. Intrapulmonary aerosol deposition was measured with a gamma-camera and was corrected for tissue attenuation and geometric distribution by using two different methods. 4. Estimated mean pulmonary deposition was 4.3% of the nebulizer dose using a lung phantom correction method, and 6.1% using a tissue attenuation method. For these two methods respectively variability between subjects (coefficient of variation) was 54 and 47%. For both methods, within-subject variability (coefficient of variation) was 37% between occasions and 23% within occasions. 5. The particle-size output of several nebulizers was highly reproducible (coefficient of variation less than 4%), but the nebulizer mass and radionuclide output of two nebulizers was more variable (coefficient of variation 5-19%), and appeared to be an important contributor to the variability in pulmonary aerosol deposition. 6. The data presented here for pulmonary deposition, used with appropriate power statistics formulae, can be used to estimate the sample sizes required for comparative studies of lung aerosol deposition.

Aerosols↗
PubMed1991

Lung 99mTc DTPA transfer in renal disease and pulmonary infection.

The half-time of transfer of 99mTc DTPA (T50) is a useful method of assessing lung epithelial permeability, which has been shown to be altered in patients with acquired immunodeficiency syndrome (AIDS) who have Pneumocystis carinii pneumonia (PCP). The present study was designed to assess the usefulness of the T50 measurement in evaluating patients with renal transplants, breathlessness, and fever. An assessment was also made of the effect of renal failure on the T50 result. Sixty-eight non-smokers (12 normal subjects, ten patients with chronic renal failure not requiring dialysis (CRF), ten patients on haemodialysis (HD), ten patients on chronic ambulatory peritoneal dialysis (CAPD), 13 patients with functioning renal transplants (Tx), seven transplanted patients with PCP, two transplanted patients with cytomegalovirus pneumonia, and four transplanted patients with other lung infections), and 30 smokers (ten normal subjects, five CRF, five HD, five CAPD, five Tx) were studied. The lung epithelial permeability of the patients with renal failure, as judged by the whole lung T50, was not significantly different from that of the normal subjects. The T50 of transplanted smokers was significantly longer than that of the normal subjects who smoked and not significantly different from the transplanted non-smokers. Patients with PCP and CMV pneumonitis had significantly faster T50 values compared with all other patients with renal disease. This fast T50 suggests that the test may be of use in identifying patients who have an alveolitis as a cause for their fever when immunosuppressed following a renal transplant.

Adult↗
PubMed1991

Radiation dose rates from adult patients undergoing nuclear medicine investigations.

Adult patients undergoing nuclear medicine investigations may subsequently come into close contact with members of the public and hospital staff. In order to expand the available dosimetry and derive appropriate recommendations, dose rates were measured at 0.1, 0.5 and 1.0 m from 80 adult patients just before they left the nuclear medicine department after undergoing one of eight 99Tcm studies, an 123I thyroid, an 111In leucocyte or a 201Tl cardiac scan. The maximum departure dose rates at these distances of 150, 30 and 7.3 microSv h-1 were greater than those found in similar published studies of adult and paediatric patients. To limit the dose to an infant to less than 1 mSv, an 111In leucocyte scan is the only investigation for which it may be necessary to restrict close contact between the infant and a radioactive parent, depending on the dose rate near the surface of the patient, the parent's habits and how fretful is the infant. It is unlikely that a ward nurse will receive a dose of 60 microSv in a working day if caring for just one radioactive adult patient, unless the patient is classified as totally helpless and has undergone a 99Tcm marrow, bone or brain scan. The data and revised calculations of effective exposure times based on a total close contact time of 9 h in every 24 h period should allow worst case estimates of radiation dose to be made and recommendations to be formulated for other circumstances, including any future legislative changes in dose limits or derived levels.

Adult↗
PubMed1991

Folic acid absorption in patients infected with the human immunodeficiency virus.

To determine the folic acid absorption characteristics of patients with human immunodeficiency virus (HIV) infection, a prospective, controlled, result-blind single-dose oral absorption study was conducted. A total of 25 subjects were fasted and given 5 mg oral folic acid; blood samples were taken at time zero and after 30, 60, 90 and 180 min. Absorption of folic acid appears to be significantly impaired in HIV disease, irrespective of the stage of the disease and notwithstanding gastro-intestinal complaints, pathogen-negative diarrhoea or drug treatment. We here present functional data, complementary to previously reported structural and biochemical findings, to support the hypothesis that the virus can cause an enteropathy in the absence of opportunist infection. Folinic acid is absorbed by the same gut mechanism as folic acid, so caution may be needed when employing oral folinic acid rescue procedures in these patients, even when resting serum and red cell folate levels appear to be normal.

Absorption↗
PubMed1991

Pulmonary deposition of nebulised amiloride in cystic fibrosis: comparison of two nebulisers.

BACKGROUND Preliminary evidence suggests that regular inhalation of nebulised amiloride reduces sputum viscoelasticity, increases the clearance of sputum by mucociliary mechanisms and by coughing and reduces the rate of deterioration in lung function in patients with cystic fibrosis. These effects depend on adequate delivery of amiloride to the airways. This study was performed to quantify and compare pulmonary deposition of amiloride produced by two different nebuliser systems. METHODS The pulmonary deposition of nebulised amiloride (1 mg in 3 ml saline) was measured in eight patients with cystic fibrosis when given via a jet (System 22 with CR 60 compressor) and an ultrasonic (Fisoneb) nebuliser. Human serum albumin labelled with technectium-99m was used as an indirect marker for amiloride and its deposition in the lung was detected with a gamma camera. RESULTS Amiloride inhalation caused no side effects or changes in spirometric indices. The mean (SD) total pulmonary amiloride deposition was 57 (24) micrograms with the System 22 and 103 (53) micrograms with the Fisoneb nebuliser. Pulmonary deposition was completed more rapidly with the Fisoneb (4-5 minutes) than with the System 22 nebuliser (7-8 minutes) and the Fisoneb was preferred by the patients. CONCLUSIONS Both nebulisers appeared to deliver adequate amounts of amiloride to the lungs, but treatment with the Fisoneb nebuliser was quicker, more efficient, and more acceptable to the patients. Of the two nebulisers assessed, the Fisoneb would be preferred for clinical trials.

Administration, Inhalation↗
PubMed1991

Prophylaxis and treatment of Pneumocystis carinii pneumonia.

Although Pneumocystis carinii pneumonia (PCP) can occur in any patient with severe impairment of immunity, there has been a sharp rise in incidence with the spread of human immunodeficiency virus through the USA and Western Europe, where nearly 80% of patients with HIV infection have at least one episode of PCP during their lifetime (Murray et al, 1984).

Antimalarials↗
PubMed1991

Radiation dose rates from paediatric patients undergoing 99Tcm investigations.

Infants or children undergoing nuclear medicine investigations may subsequently come into close contact with nurses or parents responsible for their care. In order to estimate the radiation dose to these individuals, and to formulate appropriate recommendations, dose rates were measured at distances of 0.1, 0.5 and 1.0 m from 148 paediatric patients who had undergone one of 12 99Tcm studies. The maximum dose rates of 70, 14 and 5 microSv h-1 at these distances were not greater than the corresponding maximum values found in an earlier study of adult patients. However, the maximum dose rates per unit activity of 0.5, 0.2 and 0.1 microSv h-1 MBq-1 were greater than the corresponding maximum 99Tcm adult values, consistent with a general increase of dose rate per unit activity with decrease of body weight observed in the paediatric measurements. A parent caring for and feeding a young infant is most unlikely to receive a dose equivalent of 1 mSv, and a nurse attending to one young radioactive patient is most unlikely to receive a dose equivalent in a working day of 60 microSv. The data obtained should allow radiation doses to be estimated and appropriate recommendations to be formulated for other circumstances, including any future legislative changes in dose limits or derived levels.

Adolescent↗
PubMed1991

Which apparatus for inhaled pentamidine? A comparison of pulmonary deposition via eight nebulisers.

Aerosolised pentamidine 300 mg in 5 or 6 ml solution was administered via 8 different nebuliser systems to 12 patients with acquired immunodeficiency syndrome. Using 99mTc human serum albumin as an indirect marker for pentamidine, pulmonary, extrapulmonary (gastric and oropharyngeal) and alveolar deposition of pentamidine were measured using a gamma camera. Side effects (visual analogue scales) and changes in lung function associated with each treatment were also quantified. Deposition was completed more rapidly with the ultrasonic than the jet nebulisers. Mean total pulmonary depositions (mg +/- SEM) were Respirgard II, 6.1 +/- 0.5; Centimist, 7.3 +/- 1.0, System 22 Mizer, 14.3 +/- 2.1; System 22 Mizer with particle separator; 4.5 +/- 0.4; System 22 Mizer with Optimist 2, 6.3 +/- 0.9; Fisoneb, 6.0 +/- 1.2; Pentasonic (Portasonic); 4.6 +/- 0.9; Samsonic, 2.9 +/- 0.4. Differences between the nebulisers for peripheral lung and alveolar deposition reflected this pattern. Side effects scores were largest with System 22 Mizer, Pentasonic (Portasonic), and Fisoneb, and these produced the greatest oropharyngeal and gastric deposition. The largest reductions in lung function were associated with System 22 Mizer. A 300 mg dose of pentamidine nebulised via Respirgard II is known to be effective prophylaxis for Pneumocystis carinii pneumonia when given once monthly. Our results show that equivalent pulmonary deposition can be produced by other nebulisers. System 22 Mizer gives over twice the deposition associated with Respirgard II, and used with a pentamidine dose of 150 mg is likely to produce an adequate lung dose for prophylaxis. This nebuliser, however, is associated with more marked side effects.

Acquired Immunodeficiency Syndrome↗