Quantitative aspects of SPECT. EANM Post-Congress Symposium Bressanone/Brixen 1991.
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Biomedical subjects
Publications and source records attributed to G Riccabona.
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Single photon emission computed tomography (SPECT) using N-isopropyl-p-(123I)iodoamphetamine (123I-IMP) and 99Tcm-hexamethylpropyleneamine oxime (99Tcm-HMPAO) was performed in 25 patients with different clinical stages of AIDS encephalopathy. The average interval between the two examinations was 7 days. In 15 of the 25 cases (60%) 99Tcm-HMPAO scans were different from 123I-IMP scans. Uptake defects of different extent were observed in 8 of 25 cases (32%), of different extent and different location in 3 of 25 cases (12%) and of identical extent but of different location in 4 of 25 cases (16%). Differences in the uptake patterns of 123I-IMP and 99Tcm-HMPAO with regard to extent and/or location were more commonly shown in patients with early acquired immunodeficiency syndrome (AIDS) encephalopathy (P = 0.0372). In this group, 99Tcm-HMPAO showed uptake defects of greater extent more frequently than did 123I-IMP (P = 0.0156). Our data indicate different brain uptake mechanisms of 123I-IMP and 99Tcm-HMPAO in early and advanced AIDS encephalopathy.
The treatment of juvenile struma is the domain of the pediatrician, and operations are rarely necessary, even in struma-endemic regions. An absolute indication for surgery is diagnosed or suspected struma maligna: relative indications are hyperthyroidism and euthyroid goiter. The operative procedure in benign thyroid diseases is based on the pathogenesis: a tissue-saving technique is mandatory to prevent postoperative hypothyroidism. Therapeutic strategy in malignant diseases, i.e., the radicality of surgical and postoperative management, depends, as in adults, on the prognostic relevance of variable parameters.
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Bone mineral content (BMC) of the lumbar spine (L2-L4), femoral neck, Ward's triangle and the trochanteric region was measured in 52 consecutive patients on maintenance haemodialysis. In the whole group the median BMC value as percentage of sex- and age-matched normal means was significantly decreased only in Ward's triangle (91.7%; p less than 0.02). In patients with chronic interstitial nephritis there was a significant decrease in bone density in Ward's triangle and the trochanteric region (p less than 0.02). There was no correlation between BMC and time on dialysis or intact parathormone. BMC value did not predict the type of renal osteodystrophy, according to Delling. 17 patients underwent a second investigation after one year. There was a slight fall in mean BMC of the lumbar spine (-0.9%) and Ward's triangle (-1.1%). The fall in mean BMC of the trochanteric region was pronounced (-3.2%). We believe that the observed low demineralisation, which was more pronounced in patients with interstitial nephritis, may be attributable to early and carefully monitored therapy with vitamin D metabolites.
The flumazenil analogue, Ro 16-0154, a benzodiazepine partial inverse agonist, has been labeled by halogen exchange to enable SPECT investigations of central benzodiazepine receptors in the human brain. The purified 123I-Ro 16-0154 was found to be stable in rat brain preparations and to be metabolized in rat liver preparations. Its pharmacologic properties were comparable to those of flumazenil. The biodistribution in rats (1 hr postinjection) resulted in a high brain-to-blood ratio of 16. Clinical studies revealed images of the benzodiazepine receptor density in the brain. Since the receptor labeling was markedly reduced by injection of flumazenil, it was considered to be specific. Storage defects due to pathologic cerebral blood flow and changed receptor density were detected; this shows the potential usefulness of the substance for diagnostic purposes, e.g., the differential diagnosis of various forms of epilepsy.
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In tumours of the endocrine system there are very few real "tumour markers" (e.g. CEA); all other relevant tests measure by radioassay several endocrine materials which are produced in similar ways by tumours and normal glands. Therefore, tumour marker assays in endocrinology are usually performed in follow-up studies after more or less radical therapy of tumours of the pituitary gland, thyroid gland, parathyroid glands, endocrine pancreas and the adrenal glands. On the basis of approximately 3000 assays of HGH, prolactin, thyroglobulin, calcitonin, CEA, insulin, gastrin, cortisol and aldosterone (in part with suppression and/or stimulation techniques), it is shown that these mostly indirect tumour marker assays are very important in follow-up programmes after therapy of neoplasms of the endocrine system. Their sensitivity amounts to 80%, their specificity is of the same degree.
Determination of serum and urinary neopterin levels was performed daily in 30 patients undergoing kidney transplantation for treatment of end-stage renal failure. Neopterin serum levels were determined by RIA and urinary excretion by HPLC. In parallel, the same samples were tested for creatinine content. Results indicated a strong correlation between the clearance of neopterin and creatinine. This correlation was independent of the extent of functional impairment as well as of the different causes of renal insufficiency. As a consequence, a strong relationship between serum and urinary neopterin levels was only obtained when values were corrected for different renal function by dividing them by the creatinine levels. It thus appears that major attention has to be paid to the functional state of the kidney when studying neopterin serum and/or urine values. It also appears that under these prerequisites both methods of detection as well as both sample sources yield comparable results.
The presented data show that thyroid surgery for Graves' Disease had a high therapeutic efficiency in more than 500 own patients. Considering our actual knowledge about the pathogenesis of Graves' Disease it is obvious that inadequate results of surgery are mostly due to surgical technique, which is not radical enough. Therefore subtotal bilateral thyroidectomies leaving remnants of only 4-6 g are recommended. Even as adequate premedication has shrunk the lethality of surgery to 0--which is especially significant concerning the previously dreaded postoperative thyroid storm--complications such as vocal chord paralysis and tetany do occur in a few percent. These complications, however, can usually be controlled as well as the frequent postoperative hypothyroidism. Overall thyroid surgery for therapy of Graves' Disease seems the method of choice for the treatment of younger patients with considerable thyroid enlargement and with insufficient response to antithyroid drugs.
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After accidental incorporation of radionuclides in the organism uptake in the whole-body and in critical organs can be either reduced or blocked (prevention) by appropriate medication and behaviour. Effective half-lives after incorporation in critical organs can be shortened (therapy). For different fallout-radionuclides a variety of preparations exists for such purposes. For large-scale prevention only iodine administration seems appropriate to block the uptake of the generally occurring 131-I in the thyroid. Such an iodine prophylaxis, however, seems only necessary when drinking water concentrations exceed 5000 nCi/l. Excessive amounts of iodine can influence thyroid function significantly.
Between 1969-1984 (16 years) 17 patients with "malignant haemangioendothelioma" of the thyroid were admitted to our services. This type of cancer is usually found in patients with a long history of goiter and is a very aggressive tumor. Infiltration of surrounding tissues is mostly responsible for death by asphyxia or uncontrollable bleeding. Some patients die also from metastases, which were seen frequently in the lungs. A precise preoperative diagnosis of the disease can be achieved rarely, histological classification has improved using immunohistochemical assays of Factor-VIII antigen in tumor tissue. No "prescription" for therapy can be given: results of surgery, radiotherapy and chemotherapy do not show significant differences (also in a variety of combinations). If the diagnosis is properly established, palliation will be the only therapeutic goal.
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Average iodine serum levels of 2.5 mg/100 ml were obtained in 10 patients with an average burn area of 50% and treated with povidone-iodine. Simultaneous measurements of the thyroid hormones failed to reveal any significant impairment of thyroid function apart from depressed T3 coupled with increased reverse T3. Similar findings were obtained with a control group of 10 multiply-injured patients. If renal function is unimpaired the resorbed iodine is quickly excreted. No clinical signs of iodine intoxication were observed.
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