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Biomedical subjects

O Geatti

Publications and source records attributed to O Geatti.

At least 37 records · Page 2Linked to original sources
PubMed1994

[Scintigraphy in the diagnosis of thyroid carcinoma].

Thyroid scans yield functional information useful in the differential diagnosis of thyroid nodules and are usually performed with TcO4-99m for its favourable physical properties, availability, low cost and good correlation with I123. Cold thyroid nodules are very frequent and generally due to benign diseases. To distinguish the minority representing carcinomas, classes of risk must be selected, according to multiple factors, including external radiation exposure, sex, age, iodine intake and thyroid morphology. These patients will undergo fine needle biopsy which can make the final diagnosis. Its accuracy is often preferred as a first line modality in the diagnostic approach to thyroid nodules. Tumour imaging agents are very useful in the staging and follow-up of thyroid carcinomas, but are rarely needed in the primary diagnosis of the disease.

Antibodies, Monoclonal↗
PubMed1993

L-thyroxine overdose: a case of marked, severe, prolonged, excess ingestion and review of the literature.

A case of a man with thyroid cancer who ingested between 0.9 and 3.3 mg l-thyroxine per day for over 10 years (the highest dose for 3 years) is reported. This had been prescribed for suppression of TSH for a well differentiated thyroid cancer. He was essentially asymptomatic and suffered no apparent ill effects from this prolonged and markedly excessive dosage of l-thyroxine. The literature lists a wide range of ill effects from both chronic and acute thyroid hormone overdosage but also records many examples of tolerance to excessive levels of exogenous thyroid hormone. The various circumstances leading to thyroid hormone overdose and potential ill-effects are reviewed.

Adult↗
PubMed1993

L-thyroxine malabsorption due to the injection of herbal remedies.

Two patients are described in whom the absorption of l-thyroxine was impaired by non-prescription herbal and nutritional remedies. The absorption of thyroid hormones is discussed and an approach to the problem of patients who appear to be unresponsive to the usual doses of thyroid hormones is suggested.

Absorption↗
PubMed1992

Bilateral testicular neuroblastoma. Scintigraphic depiction and therapy with I-131 MIBG.

The authors describe a 29-year-old man who had a 16-year history of neuroblastoma and uncommon manifestations. At age 13, he was diagnosed with stage III retroperitoneal ganglioneuroblastoma that was resected. Ten years later, bilateral testicular enlargement and a pelvic mass from infiltration of the neuroblastoma became palpable. Metastatic involvement was depicted with MIBG, a radiotracer that concentrates in tissues of the sympathetic nervous system. Using I-131 MIBG, the tumors were treated with therapeutic doses of radiation and a partial response was obtained. This case is unique because of the massive degree of bilateral testicular infiltration and its occurrence as a late manifestation of neuroblastoma in early adulthood.

3-Iodobenzylguanidine↗
PubMed1991

Radiolabelled semisolid test meal clearance in the evaluation of esophageal involvement in scleroderma and Sjogren's syndrome.

Esophageal involvement by scleroderma is frequent. Investigation by manometry or radiography is invasive and nonphysiological. Scintigraphy of the clearance of small radiolabelled liquid boluses in the supine position, while sensitive and noninvasive, may also be nonphysiological and does not allow the simultaneous determination of gastric emptying. We thus studied the esophageal clearance of a semisolid test meal ingested in the upright position. Forty-seven patients with scleroderma and 24 with Sjogren's syndrome were compared with ten normal controls and ten patients with gastric emptying abnormalities but no esophageal involvement. Results of scintigraphy were also correlated with manometry and contrast radiography. Quantitative evaluation of esophageal tracer retention at ten minutes postingestion was: (mean +/- SD), 2.8 +/- 1.0% in normals, 2.9 +/- 0.9% in gastric dysmotility, 4.8 +/- 2.9% in Sjogren's syndrome, and 22.3 +/- 25.0% in scleroderma; similar results were found at 20 and 60 minutes. The T 1/2 of gastric emptying was 47.1 +/- 5.7 minutes in normals, 95.9 +/- 25.3 minutes in gastric dysmotility, 62.9 +/- 19.5 minutes in Sjogren's syndrome, and 52.9 +/- 13.5 minutes in scleroderma. We conclude that esophageal clearance of a semisolid test meal is a sensitive index of esophageal dysmotility and correlates well with results from manometry and contrast radiography but is noninvasive and quantifiable. The simultaneous measurement of gastric emptying is also possible in many cases.

Adult↗
PubMed1991

A comparison of scintigraphy, thermography, ultrasound and phlebography in grading of clinical varicocele.

Varicocele, a varicosity of the pampiniform plexus, usually on the left side, is a common urologic problem. It may be associated with symptoms of local discomfort or abnormal spermatogenesis. Internal spermatic vein phlebography is the "gold standard" investigative technique, but it is invasive. Noninvasive studies include: labeled blood-pool scintigraphy, thermography and ultrasound. Two hundred sixty-three patients were investigated with various combinations of these modalities. The degree of abnormality for each modality was graded semiquantitatively and the results compared. In addition, the results of semen analysis were correlated to imaging results. Ninety-six patients were investigated with all four tests (scintigraphy, thermography, ultrasound and phlebography). The correlation of positive phlebography to positive scintigraphy was 98%, to thermography 100% and to ultrasound 98%. The concordance (grade for grade) was 71% for scintigraphy, 68% for thermography and 62% for ultrasound. There was no obvious correlation between abnormalities of semen analysis and grading of varicocele. We conclude that the diagnostic accuracy and grading of severity by noninvasive techniques (including scintigraphy) compare very favorably with that of phlebography. Moreover, scintigraphy allows the noninvasive evaluation of reflux through the internal spermatic vein, which may be useful in planning therapy.

Adult↗
PubMed1990

Late presentation of metastatic pheochromocytoma: a problem case solved by I-131 MIBG scintigraphy.

A patient presented with recurrent pheochromocytoma 10 years following the apparently successful surgical cure of a right adrenal pheochromocytoma. Conventional medical imaging techniques, (chest radiograph, abdominal ultrasound, and abdominal CT) suggested local recurrence for which surgery was planned. I-131 MIBG scintigraphy revealed disseminated metastatic disease that rendered attempts at surgical cure futile. The patient was treated with three therapeutic doses of I-131 MIBG with good symptomatic palliation and improvement of some biochemical parameters.

3-Iodobenzylguanidine↗
PubMed1990

Adrenal cortical adenoma causing Cushing's syndrome: correct localization by functional scintigraphy despite nonlocalizing morphological imaging studies.

A 60-year-old woman with Cushing's syndrome in whom high-dose dexamethasone failed to suppress glucocorticoids was studied by ultrasound and CT. Neither of these morphological studies was interpreted as revealing any adrenal abnormality. Functional imaging with NP-59 (131-I-beta-iodomethylnorcholesterol) revealed unequivocal, intense, unilateral uptake in the left adrenal gland and subsequent surgery removed a 2.5 cm adrenocortical adenoma from this site. Following surgery the patient was temporarily adrenocortically insufficient but later returned to normal. It is unusual for adrenocortical adenomas causing Cushing's syndrome not to be correctly located by CT. NP-59 scintigraphy in addition to being highly accurate in the location of adrenocortical adenomas also has the advantage of correctly depicting bilateral cortical nodular hyperplasia in which CT will frequently reveal only the largest nodule, which may be incorrectly designated a unilateral adenoma. Furthermore, scintigraphy provides evidence of suppression of the contralateral, normal adrenal cortical tissue in Cushing's syndrome caused by an adrenal adenoma and predicts the vulnerability of such patients to postoperative adrenocortical insufficiency.

Adenoma↗
PubMed1989

Scintigraphic depiction of an insulinoma by I-131 metaiodobenzylguanidine.

Scintigraphy with I-131 metaiodobenzylguanidine (MIBG) was effective in depicting a pancreatic insulinoma in a patient suffering from intermittent hypoglycemia. This observation widens the range of neuroendocrine tumors that take up to I-131 MIBG and supports the concept that many tumors of the amine precursor uptake and decarboxylation system may be imaged in this way.

3-Iodobenzylguanidine↗
PubMed1989

Alterations of iodine-131 MIBG biodistribution in an anephric patient: comparison to normal and impaired renal function.

Iodine-131 metaiodobenzylguanidine (MIBG) is an effective agent for the scintigraphic portrayal of pheochromocytomas of all types. Iodine-131 MIBG is a relatively stable radiopharmaceutical that is primarily excreted in the urine. Therefore, impaired renal function would be expected to alter [131I]MIBG pharmacokinetics which would thus affect blood levels, as well as scintigraphy. An 18-yr-old anephric male presented with hypertension and suspected pheochromocytoma. We have compared the [131I]MIBG scintigraphy and blood clearance kinetics in this anephric patient, two patients with renal insufficiency and four patients with normal renal function. The degree of renal insufficiency was directly correlated to the CPM/image (an index of whole-body retention) on all 3 days of imaging and the slower clearance of radioactivity from the blood. The relative distribution of radioactivity between the plasma and cell fractions was greatest in the patients with renal insufficiency. We therefore suggest that attention be paid to plasma creatinine levels prior to the administration of [131I] MIBG to permit accurate interpretation of scintigraphy. In addition, the effect of renal insufficiency on radiation dosimetry should be considered. It may thus be prudent to reduce the administered dose of [131I]MIBG given to anephric or renally insufficient patients to decrease radiation dose.

3-Iodobenzylguanidine↗
PubMed1988

The intraperitoneal delivery of radiolabeled monoclonal antibodies: studies on the regional delivery advantage.

The i.p. delivery of murine monoclonal antibody was compared with i.v. delivery in normal mice and rats, in normal nude mice and in those with i.p. human ovarian carcinoma xenografts. In normal rats, all classes of antibodies and antibody fragments evaluated were cleared from the peritoneal cavity at comparable rates. The regional delivery (Rd1) advantage to the peritoneal cavity following i.p. delivery was thus most dependent on the rate of clearance of the antibody or fragment from the blood stream. Determining the exact i.p. delivery advantage was problematic due to the difficulty in reliably obtaining peritoneal fluid later than 9-10 h after i.p. injection in normal animals. During the first 9 h following i.p. injection, the Rd(0-9/0-9) was, for a murine IgG2ak Fab greater than F(ab')2 greater than IgG (at 13.6 greater than 10 greater than 7.9). Two murine IgMs evaluated differed in Rd(0-9) at 27.1 and 9.2 respectively. When blood levels were extrapolated to infinity, these Rd (0-9/affinity) values were considerably lower with the Fab having the highest Rd at 4.67. The i.p. Rd advantage was almost solely due to the i.p. antibody levels seen in the first 24 h after injection, as after that time, blood levels become comparable to those seen following i.v. injection. Normal tissues obtained at sacrifice 5-7 days after i.p. injection. Normal tissues obtained at sacrifice 5-7 days after i.p. or i.v. injection in rats showed comparable levels of radioantibody activity, whether the injection was i.p. or i.v. (except for higher diaphragmatic levels following i.p. delivery). In nude mice with i.p. human-derived ovarian tumors, intact IgG clearance from the peritoneal cavity to the blood was considerably slower than in normal animals, and early i.p. tumor uptake of specific antibody was significantly higher than that following i.v. antibody delivery. With higher early tumor uptake and lower systemic exposure, early tumor/nontumor ratios were significantly greater than those for i.v. delivery, though not beyond 48 h after i.p. injection. This study demonstrates the pharmacokinetic rationale for i.p. monoclonal antibody delivery, especially for agents cleared rapidly from the blood, such as antibody fragments. In addition, definite i.p. delivery benefit for antibody specific to i.p. tumors in the i.p. ovarian cancer system was shown soon after injection. These data regarding i.p. antibody delivery should be useful in rationally planning diagnostic and therapeutic studies involving the i.p. delivery of unmodified and immunoconjugated monoclonal antibodies.

Animals↗
PubMed1988

Systemic perfusion: a method of enhancing relative tumor uptake of radiolabeled monoclonal antibodies.

We evaluated the feasibility of systemic vascular perfusion with saline (mimicking plasmapheresis) as a method to enhance tumor-specific monoclonal antibody (MoAb) tumor/background ratios. Initially, groups of rats were injected intravenously (i.v.) with 131I-5G6.4 MoAb (murine IgG2aK reactive with ovarian carcinoma). These animal's radioactivity levels were determined by dose calibrator and they were imaged before and after perfusion which was conducted at 4 or 24 h post-antibody injection. Animals were sacrificed after perfusion, as were controls, and normal organ radioactivity levels determined. In addition, nude mice bearing HTB77 ovarian cancers subcutaneously were injected i.v. with 131I-5G6.4 MoAb and were imaged before and after systemic perfusion with saline 24 h post-5G6.4 injection. Perfusion in rats dropped whole-body 5G6.4 levels significantly at both perfusion times (P less than 0.0005). The drop in whole-body radioactivity with perfusion was significantly greater for the animals perfused at 4 h post i.v. 5G6.4 antibody injection (48.3 +/- 5.1%) than for those perfused at 24 h post i.v. antibody injection (32.9 +/- 2.9%) (P less than 0.025). In the nude mice with ovarian cancer xenografts, gamma camera images of tumors were visually and quantitatively (by computer image analysis) enhanced by perfusion, with a 2.33-fold greater decline in whole body uptake than in the tumor (P less than 0.05). These studies show that (1) much background antibody radioactivity can be removed using whole-body perfusion with saline, (2) that the decline in whole body activity is larger with 4 than 24 h perfusion and (3) tumor imaging can be enhanced by this approach.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Gastrointestinal iodine-131-meta-iodobenzylguanidine activity.

Radioactivity in the colon during 131-I-meta-iodobenzylguanidine (MIBG) scintigraphy may obscure or be mistaken for tumor uptake. Fecal excretion of radioactivity was examined in eight patients following therapeutic 131-I-MIBG administration (123-218 mCi, 4.551-8.066 GBq) and was found to be 0.02-1.93% of the administered dose. Semiquantitative grading of colonic activity on scintigraphy was inversely related to fecal excretion. An additional patient with marked colonic activity was studied before and after an enema: all visible gut activity was evacuated. We conclude that radioactivity in the colon seen in 131-I-MIBG scintigraphy is due largely to gut excretion of 131-I and is not due to 131-I-MIBG uptake in the autonomic innervation of the gut. Laxatives and enemas are suggested for patients in which such gut radioactivity may lead to difficulties in interpretation.

3-Iodobenzylguanidine↗
PubMed1987

[Pituitary prolactin reserve in acute exacerbation of chronic respiratory insufficiency].

The level of pituitary prolactin reserve (PPR) was studied in 56 patients with chronic respiratory failure (CRF) in the acute stage after injections of metoclopramide and Thyrotropin Releasing Hormone (TRH). PPR was low in 90% of the subjects in both groups so that the pathogenic mechanism is more likely to be hypophyseal than hypothalamic and due to the reduced synthesis of PRL by the pituitary gland as a result of inadequate ATP synthesis and/or functional alterations to the receptors or pituitary cells following hypoxaemia and hypercapnia.

Acidosis, Respiratory↗