Widespread bone metastases can occasionally give rise to a uniform distribution of 99Tcm methylene diphosphonate resulting in a superficially normal appearance on the bone scan. The scans are recognizable by the high ratio of bone to soft tissue activity, the absence of focal lesions in the axial skeleton, and there are usually no renal images. These "superscans" can occasionally be misinterpreted as normal. An index of image quantitation related to the ratio of bone to soft tissue uptake is shown to be capable of clearly distinguishing these patients from patients in other categories. The condition is thought to be more frequently associated with prostatic carcinoma than with other aetiologies.
Further improvements have been made in the technique of human prostatic lymphoscintigraphy, allowing better anatomical localisation of the areas of uptake of activity. A single median injection into the capsule of 99mTc labelled antimony sulphide colloid has been found to give as good imaging as 2 injections on either side of the midline. By placing markers on the umbilicus, pubic symphysis and both anterior superior iliac spines, a "pelvic grid" can be superimposed on the antero-posterior view. Further help with accurate localisation may be attained by taking 3 views; antero-posterior, postero-anterior and lateral, in 9 instances, prostatic injection was performed without any sedation or anaesthesia. The resulting scintigrams were indistinguishable in quality from those of anaesthetised patients.
The conventional aluminium filtration of a general purpose X-ray tube in a district general hospital was replaced by an erbium filter for a 2-month period. The resulting reduction in skin dose was measured for a number of examinations using thermoluminescent dosimetry. The change in effective dose equivalent was calculated from these measurements and compared with previous theoretical estimates. The use of the erbium filter had no effect on radiograph quality. It was concluded that the use of an erbium filter resulted in a worthwhile reduction in radiation dose, and was a cost-effective method of dose reduction.
A simple method for demonstrating prostatic lymphatic drainage by transrectal injection of 99mTc labelled antimony sulphide colloid into the prostatic capsule has been developed. This technique may be readily applied in clinical practice with obvious potential in the assessment and follow-up of patients with carcinoma of the prostate.
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