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Biomedical subjects

M J O'Doherty

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

At least 73 records · Page 4Linked to original sources
PubMed1998

Can chest X-rays and ventilation/perfusion scans be interpreted reliably from personal computer screens?

A computer-based system is routinely used for home reporting of nuclear medicine scans performed out of hours in our unit. To report ventilation/perfusion scans (V/Q) adequately, chest radiographs are also digitized and transferred to the home personal computer. One hundred consecutive V/Q scans and their corresponding chest X-rays were reported on a personal computer and on a lightbox by two radiologists and two nuclear physicians. This study shows that ventilation/perfusion scans can be reliably reported from computer screen images. The loss of data when chest X-rays are digitized to a 512 x 512 matrix, however, results in considerable misinterpretation and the digitized chest X-ray may, at best, be unhelpful and, at worst, result in an incorrect V/Q scan report.

Diagnostic Errors↗
PubMed1998

Evaluating the Swirler nebulizer: a user's perspective.

The change from multi-use to single-use nebulizer systems could potentially result in greatly increased expense for aerosol ventilation imaging and a larger waste disposal problem. We have therefore investigated a new compact single-use nebulizer system, the Swirler (Amici), for ventilation lung imaging using 99Tcm-DTPA aerosol. Seventy-five patients requiring lung ventilation/perfusion imaging were studied. The ventilation imaging was assessed using three different fills: Group 1, 1000 MBq in 2 ml; Group 2, 1000 MBq in 4 ml; and Group 3, 2000 MBq in 4 ml. The nebulization times to give 1200 counts s-1 on the posterior ventilation image were similar for Groups 1 and 3 (mean 4 min) but slower for Group 2 (mean 6 min). Room contamination was very low when performed in a room with an extractor device. The mean room air contamination was 117.0 Bq l-1 min-1 for Group 1 amd 27.6 Bq l-1 min-1 for Group 2, comparable to previous nebulizers we have used. Dose rates measured at the surface of the lead shielded nebulizer were 6.8 microSv h-1 for 1000 MBq in 2 ml and 10.9 microSv h-1 for 2000 MBq in 4 ml. The mass median diameter (span) without the extension tubing was 1.39 microns (1.85) and with a small extension tube reduced to 1.11 microns (1.70). Qualitative and quantitative assessment of image quality showed good peripheral airways penetration of particles with no uninterpretable scans, comparable with other systems we have used. In practical terms, the device is much more compact than other systems and therefore generates a much smaller volume of waste. It is an easy device to use. However, when ventilating patients supine or erect, we found that it was necessary to use the small extension tube.

Aerosols↗
PubMed1998

Evaluation of fluorodeoxyglucose positron emission tomography in the management of soft-tissue sarcomas.

We performed a retrospective analysis to evaluate the ability of whole-body F-fluorodeoxyglucose positron emission tomography (FDG PET) to identify local recurrence and pulmonary metastases in patients with soft-tissue tumours after treatment. We compared the results of FDG PET with those of MRI for the detection of local recurrence, and with CT of the chest for pulmonary metastases. We assessed 62 patients of mean age 51 years, who had 15 types of soft-tissue sarcoma, after a mean follow-up of 3 years 2 months. For the detection of local disease, 71 comparisons showed that the sensitivity and specificity of FDG PET were 73.7% and 94.3%, respectively; there were 14 true-positive and five false-negative results. MRI had a sensitivity and specificity of 88.2% and 96.0% respectively. For the identification of lung metastases, 70 comparisons showed that the sensitivity and specificity of FDG PET were 86.7% and 100%, with 13 true-positive results and two false-negative results. CT of the chest had a sensitivity and specificity of 100% and 96.4%. Thirteen other sites of metastases were identified by FDG PET. FDG PET can identify both local and distant recurrence of tumour as a one-step procedure and will detect other metastases. It seems that all three methods of imaging are needed to define accurately the extent of disease, both at initial staging and during follow-up.

Adolescent↗
PubMed1998

Drug therapy alternatives in the treatment of thyroid cancer.

Therapy of thyroid cancers is based on the removal of the primary disease by surgery, replacement of the hormonal deficiencies and subsequent therapy of the recurrent and metastatic disease. The metabolic characteristics of many thyroid tumors mean that radionuclide techniques have been used in the identification of sites of tumour and their subsequent therapy. Differentiated thyroid cancers, papillary, follicular and mixed papillary follicular, are treated by surgery--usually a total or subtotal thyroidectomy. Postoperatively, patients have thyroxine as a replacement therapy and to suppress thyroid-stimulating hormone production. Radioiodine therapy is often given to ablate the thyroid remnant. This allows (a) adequate follow-up of patients using thyroglobulin measurements and assessment scans as necessary, and (b) further therapy with radioiodine for metastatic disease. Patients with a short effective half-life of radioiodide may require higher activities or pharmacological methods of prolonging the retention half-times of iodine. The use of chemotherapy in this group of tumors is limited and at best provides palliation. The overall prognosis is good for differentiated thyroid cancer; papillary carcinomas have an 80 to 90% 10-year survival, whereas follicular tumors are associated with a 65 to 75% 10-year survival. Medullary carcinomas may be sporadic or familial, and some of the latter form part of a multiple endocrine neoplasia syndrome (MEN). Primary treatment is surgery, and total thyroidectomy is usually recommended since tumours are often multifocal. The use of radiolabelled metaiodobenzylguanidine (MIBG) and 111In octreotide as potential therapeutic agents has been explored and may be potentially useful in palliative care. Chemotherapy is of limited benefit. The 10-year survival for medullary carcinomas is 60 to 70%. Anaplastic tumours of the thyroid are usually aggressive, with a high mortality. Treatment is palliative by surgical debulking; some patients may benefit from local radiotherapy or occasionally chemotherapy. The use of therapeutic doses of radionuclides is well tolerated, although it may be associated with a variety of mostly transient adverse effects, including gastritis, thyroiditis and sialadenitis. Therapy with high activities of radioiodine require radiation protection precautions. Despite retreatment with radioiodine there appear to be no long term effects on the fertility of patients, and healthy children are born to women receiving this treatment. 131I remains perhaps the most specific cancer therapy available today and has few adverse effects. It is difficult to see any marked improvement being developed for differentiated thyroid cancer, with the possible exception of targeted gene therapy.

Carcinoma, Medullary↗
PubMed1997

The effects of standardization and reference values on patient classification for spine and femur dual-energy X-ray absorptiometry.

The effect of two methods for standardizing dual-energy X-ray absorptiometry (DXA) measurements on patient classification by the T-score has been determined for a group of over 2000 patients. The methods proposed by the International DXA Standardization Committee and the European Community's COMAC-BME group were used in conjunction with young reference data from the major DXA manufacturers, the COMAC-BME group and the third US National Health and Nutrition Examination Survey (NHANES III). The two standardization techniques produced dissimilar classifications as measured by the kappa statistic (kappa = 0.34-0.90), especially for the femoral neck, with up to 24.3% of patients reclassified from osteopenic to normal and 18.6% reclassified from osteoporotic to osteopenic when the standardization method was changed. Considering the effects of both reference data and standardization techniques together, there was a wide variation of patient classification, with the number of patients classified as osteoporotic varying from 9.6% to 21.1% for the postero-anterior spine L2-4 region and from 2.3% to 27.6% for the femoral neck. The agreement between different classifications ranged widely, from very poor to excellent (kappa = 0.02-0.98). The creation of standardized reference data must be an important priority in order to harmonize patient management using standardized BMD measurements. The choice of standardization technique, however, must be addressed in light of the results presented here.

Absorptiometry, Photon↗
PubMed1997

Pulmonary technetium-99m diethylene triamine penta-acetic acid aerosol clearance as an index of lung injury.

Although the clearance of an inhaled nebulised radioaerosol has long been employed as a measure of lung function, this test has not found favour in nuclear medicine units to the extent that might originally have been anticipated. In this review the theoretical basis of solute transfer is considered and the measurement of radioaerosol clearance discussed. Thereafter the various clinical applications of alveolar permeability measurement are outlined. Finally, possible reasons for the restricted clinical use of the diethylene triamine penta-acetic acid clearance technique are considered. It is concluded that the technique should provide a rapid screening evaluation of the HIV+ve patient presenting predominantly with chest symptoms.

Administration, Inhalation↗
PubMed1997

Disposition of intravenous 123iodopentamidine in man.

This study compared the disposition of the radiopharmaceutical [123I]iodopentamidine with that of pentamidine after intravenous infusion by measuring plasma concentrations of each using scintilation counting and high-performance liquid chromatography (HPLC), respectively. There was rapid hepatic uptake and biliary excretion of the 123I label. Distribution kinetics of the 123I label were similar to those of pentamidine, but its elimination half-life (41 +/- 27 h) was longer than that of pentamidine measured by HPLC (11 +/- 8 h). [123I]iodopentamidine distribution reflects that of pentamidine, but elimination of the radiopharmaceutical appears slower.

Adult↗
PubMed1997

Pentavalent 99Tcm-DMSA imaging in patients with bone metastases.

Pentavalent 99Tcm-dimercaptosuccinic acid (99Tcm-(V)DMSA) has an established role in imaging medullary thyroid carcinoma. There have been case reports of uptake in bone metastases. Our aims were to compare 99Tcm-(V)DMSA with 99Tcm-hydroxymethylene diphosphonate (99Tcm-HDP) in bone metastases, to assess its value in imaging of bone metastases, and to assess the prospects of the beta-emitting analogues 186/188Re-(V)DMSA as palliative agents for painful bone metastases. Ten patients confirmed by a 99Tcm-HDP bone scan to have bone metastases secondary to carcinoma of the prostate, lung or breast were injected with 99Tcm-(V)DMSA (600 MBq). Whole-body scans acquired at 3 and 24 h were compared with the 99Tcm-HDP bone scans. 99Tcm-(V)DMSA showed high soft tissue background, kidney retention and avid uptake in most bone metastases: 86% of bone lesions identified on bone scans were detected with 99Tcm-(V)DMSA. The lesion-to-normal ratios were comparable to or lower than those for 99Tcm-HDP at 3 h, but increased by 24 h. Instances of abnormal uptake in liver, primary lung tumour, lymph nodes and pleural effusion were observed. We conclude that 99Tcm-(V)DMSA is a tracer for bone metastases (with lower sensitivity than 99Tcm-HDP) and soft tissue tumours. If 186/188Re-(V)DMSA behave similarly, they may find use in therapy for soft tissue tumours and bony metastases.

Bone Neoplasms↗
PubMed1997

Radioactively labelled diethylene triamine penta acetate lung scan in Pneumocystis carinii pneumonia and asymptomatic HIV-positive patients.

The objective of this study is to establish normal ranges for the assessment of lung permeability, using 99mTc DTPA (diethylene triamine penta acetate) aerosol by measuring the half-time of transfer from the lung in asymptomatic HIV-positive patients. Also to audit the use of the test in the clinical management of outpatients with symptoms suggestive of Pneumocystis carinii pneumonia (PCP). A retrospective analysis of data from outpatients' notes for the audit of symptomatic patients, and prospective acquisition of 'normal' data for HIV-positive asymptomatic patients who were non-smokers and smokers was performed. Over a period of 8 years, DTPA scans were performed on 400 asymptomatic HIV-positive patients (121 non-smokers and 279 smokers) and 188 symptomatic HIV-positive patients with symptoms suggestive of PCP. A biphasic curve of transfer of 99mTc DTPA with a half-time of less than 4 min, was considered diagnostic of PCP. The mean half-times (+/-SEM) for asymptomatic non-smokers was 61.4 +/- 3 min and for smokers was 21.9 +/- 0.8 min. In the symptomatic patients, 106 were treated for PCP and in 97 (91.5%) of these, the transfer was biphasic. Of the remaining 82 patients with respiratory pathology other than PCP, 71 (86.6%) had normal scans. The results show that smokers may have abnormal baseline scans 16/ 279 (5.7%) and therefore a baseline scan before symptoms should be recorded or a higher false positive rate can be expected. The test is however highly sensitive for the detection of PCP and allows the attending physician to initiate PCP treatment without delay.

AIDS-Related Opportunistic Infections↗
PubMed1997

Comparison of jet and ultrasonic nebulizer pulmonary aerosol deposition during mechanical ventilation.

Increased delivery of aerosol to a model lung (attached to a mechanical ventilator) has been demonstrated with an ultrasonic nebulizer as compared to a jet nebulizer. This study examined whether the increased aerosol deposition with an ultrasonic nebulizer could also be demonstrated in vivo. Seven patients (6 male and 1 female) were studied during mechanical ventilalion (Siemens Servo 900C, Middlesex, UK) after open heart surgery. Two studies were performed in each patient. In the first study, aerosol was delivered via a Siemens Servo 945 nebulizer system (high setting) driving a System 22 Acorn jet nebulizer (Medic-Aid, Sussex, UK) containing 3 mL (99m)technetium-labelled human serum albumin (99mTc-HSA) (50 microg; activity 74 MBq). In the second study, a DP100 ultrasonic nebulizer (DP Medical, Meylan, France) containing 12 mL 99mTc-HSA (50 microg; activity 185 MBq) was used. Pulmonary deposition was quantified using a gamma camera. The humidification of the circuit and the ventilator settings were kept constant according to the patient's clinical requirements. The total lung aerosol deposition (mean+/-SD), as a percentage of initial nebulizer activity, was greater using the ultrasonic nebulizer than using the jet nebulizer (53+/-1.4 vs 2.3+/-0.9%; p<0.002). The ultrasonic nebulizer was also associated with a reduction in the time required to complete nebulization (9 vs 21 min, respectively) (p<0.0001). Use of the DP100 ultrasonic nebulizer more than doubled lung deposition compared with the System 22 jet nebulizers in mechanically-ventilated patients. Their efficiency, speed of drug delivery, and compatibility with mechanical ventilator circuits make ultrasonic nebulizers potentially attractive for use during mechanical ventilation.

Administration, Inhalation↗
PubMed1997

PET scanning and the human immunodeficiency virus-positive patient.

UNLABELLED: The use of PET scanning in patients with human immunodeficiency virus infection and fever of unknown origin, confusion and/or weight loss was investigated. METHODS: Eighty patients were examined using PET. Fifty-seven patients had half-body scans with [18F]fluorodeoxyglucose (FDG), and 23 patients had brain studies performed with FDG. Fourteen patients also had [11C]methionine studies (2 chest, 1 abdomen and 11 brain) performed. RESULTS: Thirteen patients with lymphoma had the extent of the disease clearly identified in both nodal and extranodal sites. Patients with a variety of infections (Cryptococcus neoformans, Pseudomonas aeruginosa, Mycobacterium tuberculosis and Mycobacterium avium intracellulare) had disease localized for appropriate biopsy or sampling procedures. A half-body FDG-PET scan had a sensitivity of 92% and a specificity of 94% for localization of focal pathology that needed treatment. High uptake of FDG (greater than liver) had a positive predictive value for pathology needing treatment of 95%. FDG brain studies showed that 16 patients with CD4 T-lymphocyte counts less than 200 cells/ml had reduced cortical uptake compared with that in basal ganglia. FDG scans were abnormal in all 19 patients with focal space occupying lesions identified by magnetic resonance scans. The standardized uptake values (SUVs) over cerebral lesions due to toxoplasma were in the range of 0.14-3.7 (13 patients) and due to lymphoma were in the range of 3.9-8.7 (6 patients). Three more patients with progressive multifocal leukoencephalopathy had SUVs in the range of 1.0-1.5 over the lesions. Another patient had a low-grade oligodendroglioma (SUV = 2.9). Carbon-11-methionine uptake also was high in patients with cerebral lymphoma but did not add to the discrimination between toxoplasmosis and lymphoma in these patients obtained with the FDG scan. CONCLUSION: In hospitals with access to PET facilities, FDG scanning allows the rapid evaluation of the whole body, including the brain, of patients with human immunodeficiency virus infection, with a report potentially available within 4 hr of injection. Sites of infection and tumor were identified, and discrimination between cerebral pathologies was possible.

AIDS-Related Opportunistic Infections↗
PubMed1996

Radiation dose rates from patients receiving iodine-131 therapy for carcinoma of the thyroid.

Patients treated with radioiodine present a radiation hazard and precautions are necessary to limit the radiation dose to family members, nursing staff and members of the public. The precautions advised are usually based on instantaneous dose rates or iodine retention and do not take into account the time spent in close proximity with a patient. We have combined whole-body dose rate measurements taken from 86 thyroid cancer patients after radioiodine administration with published data on nursing and social contact times to calculate the cumulative dose that may be received by an individual in contact with a patient. These dose estimates have been used to calculate restrictions to patients behaviour to limit received doses to less than 1 mSv. We have also measured urinary iodide excretion in 19 patients to estimate the potential risk from the discharge of radioiodide into the domestic drainage system. The dose rate decay was biexponential for patients receiving radioiodine to ablate the thyroid after surgery (the ablation group, A) and monoexponential for these receiving subsequent treatments for residual or recurrent disease (the follow-up group, FU). The faster clearance in the follow-up patients generally resulted in less stringent restrictions than those advised for ablation patients. For typical activities of 1850 MBq for the ablation patients and 3700 MBq or 7400 MBq for the follow-up patients, the following restrictions were advised. Patients could travel in a private car for up to 8h on the day of treatment (for an administered activity of 1850 MBq in group A) or 4 and 2h (for activities of 3700 or 7400 MBq in group FU) respectively. Patients should remain off work for 3 days (1850 MBq/group A) or 2 days (up to 7400 MBq/group FU). Partners should avoid close contact and sleep apart for 16 days (1850 MBq/group A) or 4-5 days (3700 or 7400 MBq/group FU). Contact with children should be restricted according to their age, ranging from 16 days (1850 MBq/group A) or 4-5 days (3700 or 7400 MBq in group FU) for younger children, down to 10 days (1850 MBq/group A) or 4 days (up to 7400 MBq/group FU) for older children. The cumulative dose to nursing staff for the week after treatment was dependent on patient mobility and was estimated at 0.08 mSv for a self-caring patient to 6.3 mSv for a totally helpless patient (1840 MBq/group A). Corresponding doses to nurses looking after patients in group FU were 0.18-12.3 mSv (3700 MBq) or 0.36-24.6 mSv (7400 MBq). Sensible guidelines can be derived to limit the dose received by members of the public and staff who may come into contact with cancer patient treated with radioiodine to less than 1 mSv. The rapid clearance of radioiodine in patients treated on one or more than one occasion means that therapy could be administered at home to selected patients with suitable domestic circumstances. In most cases the restriction times, despite the high administered activities, are less than those for patients treated for thyrotoxicosis. The concentration of radioiodide in domestic drainage systems should not pose a significant risk.

Adult↗