Amiodarone-Induced Hyperthyroidism in a Patient with Functioning Papillary Carcinoma of the Thyroid and Extensive Hepatic Metastases

Thyroid hormone producing thyroid carcinoma is an uncommon cause of thyrotoxicosis. A patient with extensive hepatic metastases from well-differentiated carcinoma is presented. Administration of amiodarone for atrial fibrillation led to the development of hyperthyroidism. Precipitation of thyrotoxicosis by iodine-containing compounds in patients with thyroid carcinoma is rare. The relatively high iodine load and the slow elimination of amiodarone complicate the clinical management of such patients.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/63161/1/thy.2005.15.1337.pd

PET imaging in pediatric oncology

High-quality PET imaging of pediatric patients is challenging and requires attention to issues commonly encountered in the practice of pediatric nuclear medicine, but uncommon to the imaging of adult patients. These include intravenous access, fasting, sedation, consent, and clearance of activity from the urinary tract. This paper discusses some technical differences involved in pediatric PET to enhance the quality of scans and assure the safety and comfort of pediatric patients.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46711/1/247_2003_Article_1112.pd

Inhibition of Neutral Amino Acid Transport Across the Human Blood-Brain Barrier by Phenylalanine

The delivery of large neutral amino acids (LNAAs) to brain across the blood-brain barrier (BBB) is mediated by the L-type neutral amino acid transporter present in the membranes of the brain capillary endothelial cell. In experimental animals, the L-system transporter is saturated under normal conditions, and therefore an elevation in the plasma concentration of one LNAA will reduce brain uptake of others. In this study, we used positron emission tomography (PET) to determine the effect of elevated plasma phenylalanine concentrations on the uptake of an artificial neutral amino acid, [ 11 C]-aminocyclohexanecarboxylate ([ 11 C]ACHC), in human brain. PET scans were performed on six normal male subjects after an overnight fast and again 60 min after oral administration of 100 mg/kg of phenylalanine. The plasma phenylalanine concentration increased by an average of 11-fold between the first and second scans. This increase produced a reduction in [ 11 C]ACHC uptake in all brain regions but not in scalp. The mean ± SD influx rate constant for whole brain decreased after phenylalanine ingestion from 0.036 ± 0.002 to 0.019 ± 0.004 ml/g/min. Kinetic analysis of the effect of plasma phenylalanine concentration on the rate of [ 11 C]ACHC uptake is compatible with a model of competitive inhibition so that large increases in the concentration of one LNAA in plasma will reduce the brain uptake of other LNAAs across the human BBB.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65880/1/j.1471-4159.1995.64031252.x.pd

Courses of Malignant Pheochromocytoma

Survival of patients with metastatic pheochromocytoma that have exceeded 30 years without therapy to reduce tumors have been reported. We reviewed the records of 38 patients with malignant pheochromocytoma who had received 131 I-metaiodiobenzylguanidine ( 131 I-MIBG) treatments between 1981 and 1996 to evaluate longevity. Survival from diagnosis to last follow-up exceeded 5 years in 21 of 38 (55%) and ≥10 years in 50%. In 17 of 21, the interval from diagnosis to 131 I-MIBG therapy was greater than 5 years. Survival following 131 I-MIBG was ≥5 years in 12 of 17 and ≥10 years in 7 of 17 patients despite continued evidence of excessive circulating catecholamines. Objective responses to 131 I-MIBG therapy were seen in about 30% and were usually of a few years, duration, but one individual exhibited marked reductions in volume and function of tumors that have persisted for 21 years. No feature, including a remission of >5 years following surgical excision, was found to predict prolonged survival. In summary, many patients with malignant pheochromocytoma will follow a course extending over many years. The role of 131 I-MIBG therapy in longevity is uncertain, but this radiopharmaceutical reduces evidence of tumors in some patients. Criteria for selecting patients who will benefit from treatment remain to be determined.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73567/1/annals.1353.053.pd

Scintigraphic detection of sinusitis

Radionuclide scintigraphy is useful in the diagnosis of sinusitis. Three cases are described, using different radionuclide agents ( 99m Tc-MDP, 67 Ga-citrate and 111 Inleukocytes) in which sinusitis was discovered, though clinically unsuspected. The advantages and limitations of these agents are briefly reviewed.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46826/1/259_2004_Article_BF00286775.pd

Efficacy of radioactive iodine treatment of graves’ hyperthyroidism using a single calculated 131I dose

Abstract Objective To evaluate the success rate of therapeutic administration of a single calculated 131I activity for eliminating hyperthyroidism due to Graves’ disease. Methods and materials Patients with Graves’ hyperthyroidism underwent pinhole thyroid imaging, 24-h radioactive iodine uptake (RAIU) measurements and clinical examination and received a calculated 131I activity of 0.2 mCi per estimated gram of thyroid tissue, adjusted for the 24-h RAIU. The goal of RAI treatment was to achieve hypothyroidism within 3–6 months of 131I administration. Response to RAI therapy was assessed at 7 weeks and 3 months by clinical and biochemical follow-up. Results The study included 316 hyperthyroid patients with Graves’ disease (F238:M78, mean age 42.1 ± 16 y, 4–94). 179 patients (56.6%) had no prior therapeutic intervention (treatment-naive patients), whereas 6 patients had prior thyroid surgery, and 131 (41.5%) had been treated with anti-thyroid medications. The mean estimated thyroid gland size was 50.2 g ± 18, range 15–100. Mean RAIU was 0.57 ± 0.17 (normal 0.07–0.30). RAI doses ranged from 5 to 70 mCi (mean dose = 18.1 mCi). Successful treatment of hyperthyroidism at our institution was obtained after a single therapeutic 131-I activity administration in 295 of 316 (93.3%) patients. Multivariate logistic regression analysis demonstrated that failure of 131I therapy was associated with previous PTU therapy (p <  0.001). The mean response time after successful RAI therapy was 110.2 days, with cumulative response of 25% at 61 days, 50% by 84 days and 75% by 118 days after radioiodine administration. The mean time to respond for those on prior PTU medications was 297 days compared to 116 days for those on MMI and 109 days for those not previously treated with antithyroid medications. In patients with persistent hyperthyroidism, failure of RAI therapy was documented in 16 patients (76.2%) within (less than) one year after 131I administration and in 5 patients (23.8%) more than one year after initial therapy, considered late failure. Conclusion Successful 131I therapy for Graves’ hyperthyroidism with a single calculated dose can be achieved in the majority (> 90%) of patients, adjusting for the thyroid size and 24 h uptake measurement.https://deepblue.lib.umich.edu/bitstream/2027.42/146543/1/40842_2018_Article_71.pd

Pheochromocytoma, polycythemia and venous thrombosis

Polycythemia is rarely associated with pheochromocytoma. A patient with a 22-year history of malignant pheochromocytoma is presented in whom major complications developed as a result of long-standing polycythemia, apparently due to secretion of erythropoletin by the tumors. Despite attempts to reduce tumor burden by surgery, chemotherapy, and large doses of 1-131-metalodobenzyl guanidine, polycythemia persisted. Extensive venous thrombosis developed requiring hospitalization and anticoagulation. Thus, polycythemia itself may be a cause of major morbidity in patients with pheochromocytoma, and prophylactic measures may be warranted. Review of the 130 patients with benign and malignant pheochromocytoma studied since the introduction of I-131-metaiodobenzylguanidine in 1980 revealed another six patients with hematocrits over 50 but only one had a hematocrit greater than 55 and required regular phlebotomy. In contrast, anemia (hematocrit less than 35) due to variety of causes was present in 18 cases.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/26991/1/0000558.pd

Clinical utility of nuclear imaging in the evaluation of pediatric adrenal neoplasms

Adrenal neoplasms rarely occur in children. They can be diagnosed in the presence of endocrine, metabolic or neurological problems, an abdominal mass, more rarely an adrenal incidentaloma, or in the context of an adrenal mass discovered in the evaluation of childhood cancer including hematologic malignancy. According to standard medical practice, pediatric malignancies are almost always evaluated by 18F-fluorodeoxyglucose positron emission tomography with computed tomography ([18F]FDG PET/CT). Nuclear imaging using specific radiotracers is also an important tool for diagnosing and staging neuroblastoma, pheochromocytoma, hormone hypersecretion, or indeterminate adrenal masses. The Hippocratic oath “primum non nocere” encourages limitation of radiation in children per the ALARA concept (as low as reasonably achievable) but should not lead to the under-use of nuclear imaging because of the potential risk of inaccurate diagnosis or underestimation of the extent of disease. As in adults, nuclear imaging in children should be performed in conjunction with hormone evaluation and morphological imaging

Effect of Aspartame-Derived Phenylalanine on Neutral Amino Acid Uptake in Human Brain: A Positron Emission Tomography Study

The possible effects of elevation of the plasma phe-nylalanine level secondary to the ingestion of aspartame on brain amino acid uptake in human subjects have been investigated by means of positron emission tomography (PET). 1-[ 11 C]Aminocyclohexanecarboxylate ([ 11 C]ACHC) is a poorly metabolized synthetic amino acid that crosses the blood-brain barrier by the same carrier that transports naturally occurring large neutral amino acids. Quantitative test-retest PET studies were performed on 15 individuals. Seven received two identical baseline scans, whereas eight received a baseline scan followed by a scan performed ∼40–45 min following ingestion of an orange-flavored beverage containing 34 mg/kg of body weight of the low-calorie sweetener aspartame, a dose equivalent to the amount in 5 L of diet soft drink consumed all at once by the study subjects, weighing an average of 76 kg. The 40–45-min interval was selected to maximize the detection of possible decreases in ACHC uptake resulting from increased competition for the carrier, because the plasma phenylalanine level is known to peak at this time. We observed an 11.5% decrease in the amino acid transport rate constant Kt and a smaller decrease in the tissue distribution volume of ACHC (6%). Under conditions of normal dietary use, aspartame is thus unlikely to cause changes in brain amino acid uptake that are measurable by PET.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65668/1/j.1471-4159.1991.tb02047.x.pd