Biomedical subjects
Publications and source records attributed to M V Merrick.
Techniques of prostatic lymphoscintigraphy using 99mTc phytate (TP) and 99mTc antimony sulphide colloid (ASC) have been evaluated in 30 patients. The most successful technique was a superficial perianal injection of ASC. In general, definition of the regional lymph nodes lacked the precision and clarity that would be required for the technique to be used in staging of prostatic or other pelvic tumours; further development of the technique is recommended.
Indirect voiding radionuclide cystourethrography has been compared with micturating cystourethrography in 57 children with urinary tract infections. A quasi-quantitative technique utilizing a mini-computer to optimize the images from the gamma camera has been shown to be at least as sensitive as conventional radiological techniques but to give these results without catheterization, at a lower radiation dose and at lower cost.
A new preparation of 111In DTPA for intrathecal administration has been tested and found to be a safe and highly efficacious cisternographic agent. The rate of removal of 111In DTPA from the C.S.F. and from the whole body has been measured and has been found to be of no diagnostic value in the distinction between patients with cerebral atrophy and those with normotensive hydrocephalus. Long-term retention studies show no evidence of significant long-term retention of indium in the C.S.F. The absorbed radiation dose has been investigated and found to be in good agreement with previous estimates based upon extrapolated data.
Seventy-four patients with carcinoma of the prostate were studied annually by combined radiological and 18F scintigraphy over a 5-year period. Of the patients who have no radiological evidence of bone metastases, 25% have a positive 18F bone scan. Follow-up of these patients has shown that scan abnormalities perceded x-ray changes from between 1 to 4 years. False negative scans were not seen with 18F which allows for greater accuracy in the detection of skeletal metastases. Teh accurate staging of carcinoma of the prostate cannot be made without bone scanning. Preliminary results with 111In bleomycin as an adjunct to 18F have shown this to be a useful radio-pharmaceutical to distinguish metastases from benign lesions, and further studies are warranted.
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Brain scans with 99mTc pertechnetate were compared with scans made after administration of 111Indium bleomycin in 38 patients scanned on 41 occasions. They gave similar results in 34 pairs of examinations, including cases in which both failed to detect the tumour. In seven cases, the two agents differed. In two of these bleomycin distinguished residual tumour from the effects of craniotomy more clearly than did pertechnetate; in three bleomycin apparently detected tumour not seen with pertechnetate, and in two the differences may have been due to technical factors, or are unexplained.
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74 patients with prostatic cancer were studied annually by combined radiological and fluorine-18 scan survey over a 5-year period. The results of the long term follow-up of bone cans is reported. At the time of the initial diagnosis 71-5% of the patients had advanced disease and 56% had radiological or scan evidence of metastases. A critical evaluation of the scans resulted in the detection of early bone lesions in 25% of patients with no radiological evidence of metastases. Follow-up of these patients has shown that scan abnormalities preceded radiological changes from between 1 to 4 years and there was good correlation proven histologically by bone biopsy or autopsy in more than half of the patients. In patients with a positive bone scan and positive X-rays the scan abnormalities were more extensive than the corresponding X-ray lesions. When bone healing occurred with endocrine treatment this was more readily apparent on the X-rays. False negative scans were not seen with fluorine-18 which allows for greater accuracy in the detection of skeletal metastases. Bone scanning has enabled correct staging to be carried out. This study confirms the high incidence of cardiac and vascular complications in patients treated with oestrogens.
The distribution of 111-In in the human body was studied after the injection of -111-In-bleomycin for tumour localization. Uptake in body organs was measured by quantitative scanning using a dual detector scanner. The estimated absorbed dose from an injection of 1 mCi was 0.3 rad to the whole body, and approximately 1 rad to bone marrow, kidneys, liver and spleen.
The potential value of indium-labelled bleomycin as a diagnostic scanning agent has been investigated in patients with a variety of malignant neoplasms involving the thorax, abdomen or pelvis. Sixty-five patients were scanned on 72 occasions, the optimum time to perform the examination being 72 hours after the intravenous injection of 2 mCi 111-In chelated to 2 mg bleomycin. Tumour uptake was visualized in 53 out of 62 scans in which tumour was present, but the extent of tumour was underestimated in seven cases, and over-estimated in five others. The latter were mostly due to uptake in infective lesions. These results indicate that the situations in which indium bleomycin is most likely to provide clinically relevant information are the distinction between recurrent tumour and post-radiotherapy changes in the thorax and pelvis, the diagnosis of recurrent carcinoma within the pelvis, and the distinction between bony metastases from carcinoma of the prostate and Paget's disease. Further clinical trials are necessary to assess these situations.
The discovery of a number of phosphate complexes labelled with 99-Tc-m that localize in bone has aroused wide-spread interest in bone scanning. The physiological properties of these and other clinically useful bone-seeking radiopharmaceuticals are compared, and their physical properties assessed in relation to the characteristics and limitations of avilable detector systems. A hypothesis is put forward to explain the behaviour of the technetium-labelled agents. It is concluded that although there are differences in biochemical behaviour between these agents, strontium and fluorine, all three may, under suitable conditions, give similar clinical information. The radiation dose received by the patients is least with the usual dose of 99-Tc-m and the blood clearance of the diphosphonate and pyrophosphate preparations is faster than that of strontium, although slower than fluorine. The psi-ray energy of technetium permits a much greater efficiency of detection than of fluorine. These factors, toghether with the general availability of 99-Tc-m and its relatively low cost make the technetium diphosphonate or pyrophosphate preparations the agents of choice for most skeletal radioisotope imaging. However, there are as yet insufficient follow-up studies to be able to assess the incidence of either false-negative or false-positive findings with these agents.
Under most circumstances 52Fe, 111In, and colloid show a similar distribution of marrow. The lesser uptake of 111In by liver and spleen may occasionally be of value in permitting visualization of that portion of the spinal marrow obscured by these organs in the colloid scan. However, in red cell aplasia, when there is dissociation between phagocytic and erythropoietic functions, scanning with 111In gives no information about erythropoietic tissue distribution. Therefore, indium cannot be used as an analog for iron in the study of the hematopoietic system.