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Biomedical subjects

H R Maxon

Publications and source records attributed to H R Maxon.

67 records · Page 4Linked to original sources
PubMed1977

Metastatic pulmonary calcification in primary hyperparathyroidism.

Metastic pulmonary calcification (MPC) developed in a patient with primary hyperparathyroidism. Renal function was only minimally impaired (creatine clearance of 65 ml/min) the day prior to appearance of the lung infiltrate, but deteriorated (creatinine clearance of 14 ml/min) concomitantly with the appearance of MPC. Lung imaging with 99mTc bone-scanning agents helps differentiate MPC from other problems with similar clinical and roentgenographic findings, thus allowing prompt therapy.

Calcinosis↗
PubMed1975

Long-term observations of glucose tolerance in thyrotoxic patients.

In an attemp- to clarify the clinical importance of glucose intolerance associated with acute thyrotoxicosis, 22 patients had evaluations performed for glucose tolerance while thyrotoxic and at mean follow-up times of 8.8 months and 11.6 years after adequate antithyroid treatment. High incidences of glucose intolerance at long-term follow-up (32%) and of histories suggestive of diabetic diathesis (43%) support the hypothesis that there is an inherited relationship between diabetes mellitus and thyrotoxicosis and suggest that initial testing of all thyrotoxic patients for glucose intolerance is advisable. In addition, all thyrotoxic patients displaying diabetic glucose intolerance after a return to the euthyroid state should be considered to have permanent diabetes mellitus until proved otherwise.

Adult↗
PubMedDate not supplied

Cancer mortality following treatment for adult hyperthyroidism. Cooperative Thyrotoxicosis Therapy Follow-up Study Group.

CONTEXT: High-dose iodine 131 is the treatment of choice in the United States for most adults with hyperthyroid disease. Although there is little evidence to link therapeutic (131)I to the development of cancer, its extensive medical use indicates the need for additional evaluation. OBJECTIVE: To evaluate cancer mortality among hyperthyroid patients, particularly after (131)I treatment. DESIGN: A retrospective cohort study. SETTING: Twenty-five clinics in the United States and 1 clinic in England. PATIENTS: A total of 35 593 hyperthyroid patients treated between 1946 and 1964 in the original Cooperative Thyrotoxicosis Therapy Follow-up Study; 91 % had Graves disease, 79% were female, and 65% were treated with (131)I. MAIN OUTCOME MEASURE: Standardized cancer mortality ratios (SMRs) after 3 treatment modalities for hyperthyroidism. RESULTS: Of the study cohort, 50.5% had died by the end of follow-up in December 1990. The total number of cancer deaths was close to that expected based on mortality rates in the general population (2950 vs 2857.6), but there was a small excess of mortality from cancers of the lung, breast, kidney, and thyroid, and a deficit of deaths from cancers of the uterus and the prostate gland. Patients with toxic nodular goiter had an SMR of 1.16 (95% confidence interval [CI], 1.03-1.30). More than 1 year after treatment, an increased risk of cancer mortality was seen among patients treated exclusively with antithyroid drugs (SMR, 1.31; 95% CI, 1.06-1.60). Radioactive iodine was not linked to total cancer deaths (SMR, 1.02; 95% CI, 0.98-1.07) or to any specific cancer with the exception of thyroid cancer (SMR, 3.94; 95% CI, 2.52-5.86). CONCLUSIONS: Neither hyperthyroidism nor (131)I treatment resulted in a significantly increased risk of total cancer mortality. While there was an elevated risk of thyroid cancer mortality following (131)I treatment, in absolute terms the excess number of deaths was small, and the underlying thyroid disease appeared to play a role. Overall, (131)I appears to be a safe therapy for hyperthyroidism.

Adult↗
PubMedDate not supplied

Effects of thyroid status and choice of USP preparation on the pharmacokinetics of propylthiouracil in the beagle dog.

In vitro dissolution profile testing of 12 generic 6-propyl-2-thiouracil (PTU) formulations indicated significant differences in their solubilities in water and in 0.1N hydrochloric acid. Two products, representing the extremes of solubility, were subsequently tested for bioavailability. Bioavailability data from euthyroid, hyperthyroid, and hypothyroid beagle dogs indicated that the rate of PTU absorption varied appreciably between the two generic products studied. These results were consistent with the in vitro dissolution data. Comparisons of the pharmacokinetic parameters obtained for the euthyroid beagle dog to those reported for euthyroid man12 indicated that the beagle dog is an adequate model for PTU disposition in man. These combined results suggest that all generic formulations of PTU are not the same and that the most soluble product may be desirable in situations where rapid absorption is important, such as thyroid storm.

Animals↗
PubMedDate not supplied

Imaging modalities in the follow-up of non-iodine avid thyroid carcinoma.

INTRODUCTION: The treatment of primary thyroid cancer requires protracted follow-up because of to the possibility of the development of recurrent metastases many years after the initial diagnosis. Often such follow-up involves imaging at regular intervals with diagnostic I-131 studies. However, not all thyroid cancer concentrates I-131. The purpose of this article is to review the efficacy of alternative diagnostic imaging modalities for follow-up of thyroid carcinomas that do not concentrate radioiodine. MATERIALS AND METHODS: These procedures include the use of nuclear medicine imaging with thallium-201 (TI-201), Tc-99m-sestamibi, Tc-99m pentavalent dimercaptosuccinic acid (DMSA), radiolabeled anti-carcinoembryonic antigen antibodies, and radioiodinated-131 meta-iodobenzyl guanidine, as well as computerized x-ray tomography, magnetic resonance imaging (MRI), and ultrasound (US). RESULTS AND CONCLUSION: Thallium-201, MRI, and pentavalent DMSA provide adequate sensitivity for follow-up of selected patients with suspected recurrent noniodine concentrating thyroid carcinoma.

3-Iodobenzylguanidine↗
PubMedDate not supplied

Biokinetics and dosimetry analysis in healthy volunteers for a two-injection (rest-stress) protocol of the myocardial perfusion imaging agent technetium 99m-labeled Q3.

BACKGROUND: Trans (N,N'-ethylene bis(acetylacetoneimine)) bis(tris(3-methoxy-1-propyl) phosphine) 99mTc(III) (99mTc-Q3) has been developed for myocardial perfusion imaging. Biokinetic studies and dosimetry analysis have been completed for six healthy volunteers. METHODS AND RESULTS: The same-day two-injection protocol involved (1) an average rest injection of 241 MBq of 99mTc-Q3 followed by myocardial single-photon emission computed tomography (SPECT) at 15.0 minutes and a whole body (WB) scan at 1.5 hours; and (2) an average stress injection during treadmill exercise of 744 MBq of 99mTc-Q3 at 2.4 hours (postrest injection) followed by myocardial SPECT and additional WB scans at 1.5, 3.5, 6.5, and 21 hours poststress injection. Total urine was collected over 24 hours. Absolute organ activities were determined by conjugate counting methods. The two-injection data were simplified to a one-injection equivalent data set to facilitate dosimetry analysis. Decay corrected average percentage uptake values, plus or minus one standard deviation, for the myocardium were 1.4% +/- 0.2% at approximately 1.5 hours for both the postrest and poststress injections. The average biologic half-time for the myocardium was 26.4 hours. The highest organ uptake values included the gallbladder with 5.5% +/- 1.9% and the liver with 4.1% +/- 1.0% at the 1.5 hours poststress scan time. The sum of all gastrointestinal (GI) tract components was 18.8% +/- 9.4% at approximately 6.5 hours poststress injection (before any fecal elimination). The total 24 hour urine clearance was 17.1% +/- 2.4%. The gallbladder wall and upper large intestine wall received the highest doses at 0.024 and 0.023 mGy/MBq, respectively. CONCLUSION: The effective dose equivalent is estimated to be 0.01 mSv/MBq, which for an administration of 1110 MBq (30 mCi) is less than half that of a standard imaging protocol using 111 MBq (3 mCi) of 201Tl, and comparable to the published estimates for 99mTc-labeled sestamibi and 99mTc-labeled tetrofosmin (also normalized to 1110 MBq of administered activity). The 99mTc-Q3 exhibits myocardium uptake similar to that for these other two 99mTc agents.

Adult↗
PubMedDate not supplied

In vivo quantitation of lesion radioactivity using external counting methods.

Quantitative external counting methods for the in vivo determination of the activity uniformly distributed in an area of interest (lesion) have been developed. The theoretical work has been extended to include the effects of regions of differing attenuation coefficient and of non-target organ activity in the tissue surrounding the lesion. A clinical quantitative procedure utilizing a "calibrated" gamma camera and associated computer system is described. Studies including a bone substitute material in a water phantom confirmed the basic theoretical work.

Models, Structural↗
PubMedDate not supplied

Scintigraphic evaluation of duodenogastric reflux: significance in the diagnosis of acute cholecystitis.

Duodenogastric reflux (DGR) as seen on hepatobiliary scintigraphy has been reported as a useful secondary sign for the diagnosis of acute cholecystitis. We evaluated the association of reflux with cases of acute cholecystitis as compared to those with chronic cholecystitis or other conditions. Thirty-six of 198 patients referred for hepatobiliary imaging showed DGR (18%). Among 26 patients with acute cholecystitis, 6 (23%) had DGR as compared to 9/40 (23%) cases with chronic cholecystitis, 3/12 cases with acute pancreatitis, 4/13 cases with previous cholecystectomy, and 3/8 cases with duodenal ulcer. No statistically significant differences were found between the prevalence of DGR in cases with acute cholecystitis and those with chronic cholecystitis or other nonacute cholecystitis diagnostic categories. Although acute cholecystitis is a condition frequently associated with DGR, such reflux is a nonspecific finding and should not be considered as a secondary sign of acute cholecystitis when interpreting hepatobiliary scans.

Acute Disease↗