Iodine-131 monitoring in sewage plant outflow.

Three different hospital sites (Oxford, Sutton and Guildford) have performed sampling of their local sewage plant outflow to determine levels of radioactivity resulting from iodine-131 patients undergoing radionuclide therapies. It was found that a maximum of 20% of activity discharged from the hospitals was present in the sewage plant final effluent channel. This is significantly below the level predicted by mathematical models in current use. The results further show that abatement systems to reduce public exposure are unlikely to be warranted at hospital sites.

False positive 131I whole body scans in thyroid cancer.

Well differentiated thyroid cancer is a rare disease in the UK. It is the only cancer which, having metastasized, remains curable by radioisotope therapy with 131I. The main indication for administering repeat doses of 131I is the appearance of abnormal uptake in a whole body scan following diagnostic or therapeutic 131I administration. False positive scans, showing the presence of 131I uptake in the absence of residual thyroid tissue or metastases can occur, although they are uncommon. Unless recognized as a false positive, 131I uptake may result in diagnostic error and lead to administration of an unnecessary therapy dose. We describe a series of nine patients in whom the scans showed false positive uptake of 131I, including cases where the cause of the uptake is still uncertain. We demonstrate the common sites of false positive uptake, discuss the underlying mechanisms and suggest a systematic approach to the interpretation of whole body scans in order to prevent unnecessary treatment with 131I.

Thyroid volume measurement in thyrotoxic patients: comparison between ultrasonography and iodine-124 positron emission tomography.

The aim of this paper was to compare ultrasound (US) assessment of thyroid volume with that obtained by positron emission tomography (PET), in patients scheduled for adaptive radioiodine therapy, in which 50 Gy was prescribed to the functional PET volume. Firstly a pilot study was performed to ascertain the optimum method for US assessment of thyroid volume. Then 17 comparative measurements of thyroid volume by US and PET were made on 15 patients (two male and thirteen female, ages 28-73 years) with suspected Graves' disease. This comparison showed that in normal sized and enlarged thyroid glands (n=13), the ratio of functional PET to anatomical US volume was approximately 2:3. However, using the same ellipsoid model, PET and US assessment of anatomical volume agreed within the measurement errors. Owing to the presence of nodules and non-uniform distribution of radioiodine, the functional PET volume and anatomical US volume are often not equivalent. If high-resolution emission tomography (e.g. PET) is unavailable, the comparative data presented in this paper could be used to derive the functional volume from the US volume for calculating functional thyroid dose in hyperthyroid patients undergoing radioiodine therapy.

Imaging metastatic testicular germ cell tumours with 18FDG positron emission tomography: prospects for detection and management.

The aim of this study was to investigate the role of positron emission tomography (PET) with [18F]fluoro-2-deoxyglucose (18FDG) in metastatic testicular germ cell tumours. Twenty-one patients with stage II-IV testicular germ cell tumours were imaged by PET with a multiwire proportional chamber PET system and 18FDG. Avid 18FDG uptake was seen in metastatic disease from primary seminoma and malignant teratoma. Normal tissue uptake was seen in differentiated teratoma or necrotic, fibrotic tissue. 18FDG standard uptake values and tumour to normal tissue ratios were 6.0 +/- 1.4 and 1.7 +/- 0.4 (mean +/- 1SD), respectively, for malignant tissue. Reduction of 18FDG tumour to normal tissue ratios from pre-treatment to on-treatment scans was predictive of response (n = 3). No significant reduction in 18FDG uptake was seen in patients not responding to therapy (n = 2). These results suggest a role for 18FDG PET in the detection and management of metastatic testicular germ cell tumours.