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M J O'Doherty

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

At least 55 records · Page 3Linked to original sources
PubMed1999

A PET study of 18FDG uptake in soft tissue masses.

A study was performed with the aim of investigating some of the methodological factors affecting the ability of quantitative 2-[18F]-fluoro-2-deoxy-d-glucose (FDG) positron emission tomography to assess tumour malignancy. Twenty-nine patients with soft tissue masses were studied using a 6-hour scanning protocol and various indices of glucose metabolism were compared with histological grade. Significant differences were observed in the time-activity response of benign and high-grade tumours. High-grade sarcomas were found to reach a peak activity concentration approximately 4 h after injection whereas benign lesions reached a maximum within 30 min. This translated to improved differentiation between these two tumour types using a standard uptake value (SUV) derived from images acquired at later times. An SUV measured 4 h post-injection was found to be as useful an index of tumour malignancy as the metabolic rate of FDG determined using either Patlak or non-linear regression techniques. Each of these indices had a sensitivity and specificity of 100% and 76% respectively for the discrimination of high-grade sarcomas from benign tumours.

Case-Control Studies↗
PubMed1999

Are restrictions to behaviour of patients required following fluorine-18 fluorodeoxyglucose positron emission tomographic studies?

The clinical use of positron emission tomography (PET) is expanding rapidly in most European countries. It is likely therefore that patients receiving the tracer fluorine-18 fluorodeoxyglucose (18FDG) will be discharged to come into contact with family members, members of the public and ward staff. There are few direct measurements on which to base any recommendations with regard to radiation protection, and so we have measured the dose rates from patients undergoing clinical PET examinations in our centre. Seventy-five patients who underwent whole-body and brain 18FDG PET examinations were studied. Dose rates were measured at 0.1, 0.5, 1.0 and 2.0 m from the mid thorax on leaving the department. The median administered activity was 323 MBq with a 95th percentile value of 360 MBq. The median dose rates measured at the four distances were 90.0, 35.0, 14.0 and 5.0 microSv h-1 (the median dose rates per unit administered activity at 2 h post injection were 0.31, 0.11, 0.04 and 0.02 microSv h-1 MBq-1). The corresponding 95th percentile values were 174.0, 69.0, 29.0 and 7.5 microSv h-1 (0.43, 0.2, 0.08 and 0.03 microSv h-1 MBq-1). A number of social situations were modelled and an annual dose limit of 1 mSv was used to determine whether restrictive behavioural advice was required. In the case of nursing staff on wards a value of 6 mSv was regarded as the annual limit, which translates to a daily limit of approximately 24 microSv. There is no need for restrictive advice for patients travelling by public or private transport when they leave the department 2 h after the administration of 18FDG. Similarly, there is no need for restrictive advice with regard to their contact with partners, work colleagues or children of any age, although it should be stressed that children should not accompany the patient to the scanning department. The only possible area of concern is in an oncology ward, where patients may be regularly referred for PET investigations and other high activity radionuclide studies and are partially helpless. Even in this area, however, it is unlikely that a nurse would receive a daily dose of more than 24 microSv. We conclude that there is no need for restrictive advice for patients undergoing 18FDG PET studies given the current administered activities.

Adolescent↗
PubMed1999

Radiation exposure of the families of outpatients treated with radioiodine (iodine-131) for hyperthyroidism.

Patients who receive radioiodine (iodine-131) treatment for hyperthyroidism (195-800 MBq) emit radiation and represent a potential hazard to other individuals. Critical groups amongst the public are fellow travellers on the patient's journey home from hospital and members of the patient's family, particularly young children. The dose which members of the public are allowed to receive as a result of a patient's treatment has been reduced in Europe following recently revised recommendations from ICRP. The annual public dose limit is 1 mSv, though adult members of the patient's family are allowed to receive higher doses, with the proviso that a limit of 5 mSv should not be exceeded over 5 years. Unless the doses received during out-patient administration of radioiodine can be demonstrated to comply with these new limits, hospitalisation of patients will be necessary. The radiation doses received by family members (35 adults and 87 children) of patients treated with radioiodine at five UK hospitals were measured using thermoluminescent dosimeters mounted in wrist bands. Families were given advice (according to current practice) from their treatment centre about limiting close contact with the patient for a period of time after treatment. Doses measured over 3-6 weeks were adjusted to give an estimate of values which might have been expected if the dosimeters had been worn indefinitely. Thirty-five passengers accompanying patients home after treatment also recorded the dose received during the journey using electronic (digital) personal dosimeters. For the "adjusted" doses to infinity, 97% of adults complied with a 5-mSv dose limit (range:0.2-5.8 mSv) and 89% of children with a 1-mSv limit (range: 0.2-7.2 mSv). However 6 of 17 children aged 3 years or less had an adjusted dose which exceeded this 1 mSv limit. The dose received by adults during travel was small in comparison with the total dose received. The median travel dose was 0.03 mSv for 1 h travel (range: 2 microSv-0.52 mSv for 1 h of travel time). These data suggest that hyperthyroid patients can continue to be treated with radioiodine on an out-patient basis, if given appropriate radiation protection advice. However, particular consideration needs to be given to children aged 3 years or younger. Admission to hospital is not warranted on radiation protection grounds.

Adolescent↗
PubMed1999

Evaluation of fluorine-18-fluorodeoxyglucose whole body positron emission tomography imaging in the staging of lung cancer.

BACKGROUND: Surgical resection of lung cancer remains the treatment of choice in appropriately staged disease, but conventional imaging techniques have limitations. Positron emission tomography (PET) may improve staging accuracy. METHODS: We studied whole body and localized thoracic PET in staging lung cancer. Standardized uptake value was calculated for the primary lesion. Ninety-seven patients under consideration for surgical resection were included. PET, computed tomography, and clinical staging were compared to stage at operation, biopsy, or final outcome. Mean follow up was 17.5 months. RESULTS: PET detected all primary lung cancers with two false-positive primary sites. Sensitivity and specificity for N2 and N3 mediastinal disease was 20% and 89.9% for computed tomography and 70.6% and 97% for PET. PET correctly altered stage in 26.8%, nodal stage in 13.4%, and detected distant metastases in 16.5%. PET missed 7 of 10 cerebral metastases. PET altered management in 37% of patients. PET staging (p<0.0001) and standardized uptake value (p<0.001) were the best predictors of time to death apart from operative staging. CONCLUSIONS: PET provides significant staging and prognostic information in lung cancer patients considered operable by standard criteria. Routine use of PET will prevent unnecessary operation and may be cost effective.

Adult↗
PubMed1999

Exposure of critical groups to nuclear medicine patients.

When a radiopharmaceutical has been administered to a patient, assessment of the risk to critical groups from emitted photon radiation is by measurement of the integral dose received by an individual, or by measurements of the dose rate external to the patient coupled with appropriate occupancy factors. Estimations have been made from the available data of the dose to critical groups exposed to patients who have undergone diagnostic or therapeutic procedures. These dose estimations can be used to assess the impact of the proposed changes in statutory requirements, and to allow appropriate recommendations to be formulated. Two areas for consideration are that pregnant staff exposed to nuclear medicine patients will require an abdominal surface dose limit lower than 2 mSv to restrict their foetal dose to 1 mSv, and the current UK restrictions for the behaviour of patients who have undergone 131I treatment are either already adequate or can even be relaxed in order to restrict the exposure of members of the public to the proposed lower dose limits. Agreement is needed on the value (e.g. 95th percentile) from a study of the dose to a number of individuals which should serve as the basis for radiation protection recommendations.

Breast Feeding↗
PubMed1999

Prospective evaluation of soft tissue masses and sarcomas using fluorodeoxyglucose positron emission tomography.

BACKGROUND: The differentiation of soft tissue sarcoma (STS) from benign masses is difficult owing to their clinical and radiological similarities. Accurate staging is hindered by the large number of sites at which metastases may be found. This study examined the value of whole-body [18F]2-fluoro-2-deoxy-D-glucose positron emission tomography (FDG PET) in patients presenting with soft tissue masses. METHODS: Thirty patients with a soft tissue mass suspected to be malignant were evaluated with FDG PET. The images were evaluated qualitatively and quantitatively for uptake of FDG to determine whether benign lesions could be differentiated from malignant tumours, and for the presence of metastases. RESULTS: Thirty-one masses were removed from 30 patients; 12 were benign and 19 were malignant STSs. Using qualitative assessment of the FDG PET images, all the high-grade STSs (n = 12) were correctly identified, but low-grade STS (n = 7) could not be differentiated from a benign lesion. Using a quantification assessment, there was a 95 per cent sensitivity and a 75 per cent specificity in diagnosing STS. Three patients had metastases at presentation; two were correctly identified by FDG PET. CONCLUSION: FDG PET has a role in distinguishing high-grade STS from low-grade or benign STS and may have a role in staging malignant tumours.

Adolescent↗
PubMed1999

Microbiological and radioactive contamination from radioaerosol ventilation scanning: is there a problem?

Radioaerosol lung imaging may result in (a) microbiological contamination of nebulizer circuits (a potential hazard to patients if the circuit is re-used), and (b) radioaerosol contamination of the atmosphere (a hazard to staff, particularly if inhaled, ingested or both). Altogether, 138 circuits were assessed for bacteriological contamination, 93 of which had been used for ventilation perfusion studies and 45 for lung permeability studies in human immunodeficiency virus (HIV) positive patients. The circuits used for ventilation/perfusion (V/Q) studies were re-used over a period of 1-5 days. The mouthpiece and Y-piece were changed between patients. The circuits used for permeability studies were changed in toto for each patient. Organisms belonging to normal respiratory flora were isolated from the Y-piece, mouthpiece or both in 9 of 138 cases. An additional case (from one of the HIV-positive patients) demonstrated a growth of methicillin-resistant Staphylococcus. We also demonstrated bacteriological growth, most likely of patient origin, in circuit tubing in 11 cases at the end of the first day's use and 9 cases by day 5. None of the circuits used for HIV-positive cases were culture-positive. Airborne radioactive contamination was assessed during radioaerosol inhalation with and without an air extractor device (Nederman) during 40 ventilation studies. The 20 studies with air extraction showed a large decrease in room air contamination. Nebulizer circuits can, and occasionally do, become contaminated with patients' organisms; this represents a potential infection control hazard and therefore re-use is contraindicated. The use of an air extractor will significantly reduce airborne radioaerosol contamination.

Aerosols↗
PubMed1999

Fluorodeoxyglucose PET in the evaluation of amputations for soft tissue sarcoma.

The aims of this study were to evaluate the uptake of fluorodeoxyglucose (FDG) in the stumps of patients who have had amputations for soft tissue sarcoma and assess its utility in identifying local recurrence of disease. Sixteen patients who had either an upper or a lower limb amputation were evaluated. FDG PET scans (half body scans to the stump +/- local emission transmission views of the stump) were performed as part of their routine follow-up for evidence of metastases over a number of years (mean = 2.6 years; range 0.25-8 years). Diffuse uptake was found in 10 stumps for up to 18 months post-surgery without any evidence of disease recurrence. Focal areas of uptake were associated with known pressure areas with skin breakdown that could be seen clinically. In the absence of localized clinical changes, these areas represented a recurrence and needed a biopsy.

Adolescent↗
PubMed1999

A one-hour walk-in service for wrist trauma imaging.

We investigated the feasibility of rapid imaging of wrist trauma following casualty presentation and any subsequent effect on image quality and interpretability. All patients referred for wrist imaging were injected with 370 MBq 99Tcm-hydroxymethyl diphosphonate (HDP) and imaged 1, 2 and 3 h later. Palmar images were acquired on a 256 x 256 x 16 matrix using a high-resolution collimator, 140 keV photopeak and a 20% window. The images were scored qualitatively by four qualified observers in three categories: image quality, lesion detection and lesion localization. Statistical analysis indicated a significant improvement in scan quality with time, the mean difference (+/- standard error of the mean) between the 1 and 3 h scans being 0.81 +/- 0.07 (P = 0.001). No significant differences were seen in lesion detection (0.05 +/- 0.08; P = 0.51) or localization (0.14 +/- 0.08; P = 0.10). We conclude that imaging of wrist trauma is possible as early as 1 h post-injection of 99Tcm-HDP, although negative studies at 1 h require a 3 h image to maintain diagnostic accuracy.

Adolescent↗
PubMed1998

Detection of lymphoma in bone marrow by whole-body positron emission tomography.

Positron emission tomography (PET) is a whole-body imaging technique using 18 fluorine-fluorodeoxyglucose (FDG), whose uptake is increased in tumor cells. Published studies have shown PET to be an effective method of staging lymphoma and to be more sensitive than CT at detecting extranodal disease. The purpose of this study was to determine whether the increased marrow uptake of FDG observed in some lymphoma patients during routine staging PET scans represented marrow involvement by disease. PET scans of 50 patients with Hodgkin's (12) and non-Hodgkin's (38) lymphoma were analyzed by three independent observers and the marrow graded as normal or abnormal using a visual grading system. Unilateral iliac crest marrow aspirates and biopsies were performed on all patients. The PET scan and marrow histology agreed in 39 patients (78%), being concordant positive in 13 and concordant negative in 26 patients. In 8 patients the PET scan showed increased FDG uptake but staging biopsy was negative; in 4 of these 8 patients the PET scan showed a normal marrow background with focal FDG "hot spots" distant from the site biopsied. In 3 patients the marrow biopsy specimen was positive but the PET scan normal; 2 of these 3 patients had non-Hodgkin's lymphoma whose malignant cells did not take up FDG at lymph node or marrow disease sites. Therefore, there were only 5 patients (10%) in whom there was a difference between the PET scan and biopsy result which could not be fully explained. Visual interpretation of marrow FDG uptake during whole-body staging PET scans can correctly assess marrow disease status in a high proportion of lymphoma patients. PET has the potential to reduce the need for staging marrow biopsy.

Biopsy↗
PubMed1998

Iodine-123 salmon calcitonin, an imaging agent for calcitonin receptors: synthesis, biodistribution, metabolism and dosimetry in humans.

Calcitonin is used to reduce high serum calcium levels in patients with malignancy, and as therapy for osteoporosis and Paget's disease. Receptors for the peptide have been identified in some human cancer cells including those of lung, breast, bone, prostate, and medullary carcinoma of the thyroid, suggesting that an imaging agent for the receptors might be useful in nuclear oncology. A modified chloramine-T method was used to label a pharmaceutical form of salmon calcitonin (SCT) with iodine-123. Labelling can be performed within 5 min including purification, resulting in >95% radiochemical purity and 70% yield. Digestion analysis shows labelling with two iodine atoms on the tyrosine residue. A Chinese hamster ovary cell-based assay showed that the receptor binding and activation were not impaired by the labelling. Biodistribution in mice was similar to that of commercially available mono-iodinated 125I-labelled SCT, kidney being the principal target organ. Evaluation in three patients previously diagnosed as having Paget's disease (injected with 37 MBq [123I]diiodotyrosyl22-SCT, containing less than 4 IU hormone, imaged dynamically up to 0.5 h and at intervals up to 24 h) shows early uptake in liver, kidney and sites of known Paget's disease but not in normal bone, and later uptake in thyroid and stomach. Blood clearance was fitted to a biexponential with half-lives of 3.4-7.4 min and 3-34 h. Radiation dosimetry was estimated using MIRDOSE 3. The highest doses (mean mGy/MBq) were to thyroid (6.8x10(-1)) and kidney (6.0x10(-2)), with a whole-body dose 3.0x10(-2). High performance liquid chromatography analysis revealed that urinary radioactivity was mostly in the form of iodide and diiodotyrosine within minutes of injection, indicating rapid in vivo breakdown. In summary, [123I]diiodotyrosyl22-SCT binds to calcitonin receptors and can image sites of Paget's disease but its imaging potential is not optimal because of rapid breakdown and clearance from target tissues, and an alternative radiolabelling approach is required.

Aged↗
PubMed1998

Pentavalent rhenium-188 dimercaptosuccinic acid for targeted radiotherapy: synthesis and preliminary animal and human studies.

Pentavalent rhenium-188 dimercaptosuccinic acid [188Re(V)DMSA] is a beta-emitting analogue of 99mTc(V)DMSA, a tracer that is taken up in a variety of tumours and bone metastases. The aim of this study was to develop the kit-based synthesis of the agent on a therapeutic scale, to assess its stability in vivo, and to obtain preliminary biodistribution and dosimetry estimates, prior to evaluation of its potential as a targeted radiotherapy agent. The organ distribution of 188Re in mice was determined 2 h after injection of 3 MBq 188Re(V)DMSA prepared from eluate from a 188W/188Re generator. Three patients with cancer of the prostate and three with cancer of the bronchus, all with bone metastases confirmed with a standard 99mTc-hydroxymethylene diphosphonate (99mTc-HDP) scan, were given 370 MBq 188Re(V)DMSA and imaged at 3 h and 24 h using the 155-keV gamma-photon (15%). Blood and urine samples were collected to determine clearance and to analyse the speciation of 188Re. Organ residence times were estimated from the scans, and used to estimate radiation doses using MIRDOSE 3. In mice, 188Re(V)DMSA was selective for bone and kidney. In patients, it showed selectivity for bone metastases (particularly those from prostate carcinoma) and kidney, but uptake in normal bone was not significantly greater than in surrounding soft tissues. Of the normal tissues the kidneys received the highest radiation dose (0.5-1.3 mGy/MBq). The images were strongly reminiscent of 99mTc(V)DMSA scans in similar patients. High-performance liquid chromatography analysis of blood and urine showed no evidence of 188Re in any chemical form other than 188Re(V)DMSA up to 24 h. In conclusion, 188Re(V)DMSA and its 186Re analogue warrant further clinical assessment as generator/kit-derived agents for treatment of painful bone metastases. These agents should also be assessed in medullary thyroid carcinoma and other soft tissue tumours which have been shown to accumulate 99mTc(V)DMSA.

Aged↗
PubMed1998

Therapeutic implications of thymic uptake of radioiodine in thyroid carcinoma.

The management of 38 consecutive patients with differentiated thyroid carcinoma in the period 1991-1996, who each received at least one therapy dose of iodine-131, was reviewed, looking in particular at those in whom anterior mediastinal uptake was demonstrated on scans taken 3 and 7 days post-therapy. Such activity was noted in ten patients. On the basis of clinical follow-up, thyroglobulin measurement and radiological and other scintigraphic imaging, in nine of the ten patients the anterior mediastinal activity was attributed to physiological thymic uptake. Of those nine, all were under 50 years of age; seven were considered disease free, one had residual disease in the neck and one had distant metastases. Physiological uptake by the thymus was more prominent on the 7-day scans and in patients with low tumour volumes. For appropriate patient management it is essential to recognise that physiological uptake of 131I by the thymus in patients under 50 years of age is a potential cause of false-positive therapy scans.

Adult↗
PubMed1998

The value of the chest radiograph in reporting aerosol ventilation-perfusion scans.

It has become accepted practice to have a chest radiograph (CXR) available for reference at the time of reporting a ventilation-perfusion (V/Q) scan. We designed a study to determine whether the availability of a CXR altered the interpretation of V/Q scans in our unit. One hundred consecutive V/Q scans were reported with and without reference to a CXR by two radiologists and two nuclear physicians. The V/Q reports were then compared. Our results show that the availability of a CXR has no effect on the V/Q scan report.

Aerosols↗