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Biomedical subjects

H R Maxon

Publications and source records attributed to H R Maxon.

At least 37 records · Page 2Linked to original sources
PubMed1990

Re-186(Sn) HEDP for treatment of painful osseous metastases: initial clinical experience in 20 patients with hormone-resistant prostate cancer.

Rhenium-186(tin) hydroxyethylidene diphosphonate (HEDP) is a new radiopharmaceutical that localizes in areas of osseous metastases in a manner similar to that of standard bone-scanning agents. It also emits beta particles with sufficient energy to be therapeutically useful. A single intravenous injection of about 33 mCi (1,221 MBq) was given to each of 20 elderly patients with advanced skeletal metastases from hormonally resistant prostate cancer. Prompt, significant relief of pain occurred 80% of the time with no significant side effects and only minimal, transient marrow toxicity. Re-186(Sn) HEDP appears to be a useful new agent for the palliation of painful osseous metastases in prostate cancer.

Adenocarcinoma↗
PubMed1989

A comparative study of indium-111 DTPA radionuclide and iothalamate meglumine roentgenographic arthrography in the evaluation of painful total hip arthroplasty.

Fifteen patients with painful total hip prostheses were referred for nuclear medicine and roentgenographic arthrography studies to exclude loosening of the acetabular and/or the femoral component. A new radioisotopic technique suitable for the evaluation of both components was developed using dual-isotope single-photon tomography with 99mtechnetium methylene diphosphonate bone imaging and indium-111 diethylenetriaminepentacetic acid arthrography. Thirteen of the 15 subjects were subsequently treated with additional surgery. The surgical findings were compared with the nuclear medicine and roentgenographic results. The overall diagnostic accuracy of both arthrographic procedures was approximately 80%, but the roentgenographic arthrogram was more sensitive and the radionuclide arthrogram was more specific.

Aged↗
PubMed1988

Re-186(Sn) HEDP for treatment of multiple metastatic foci in bone: human biodistribution and dosimetric studies.

Investigation of the biodistribution of subtherapeutic amounts of a new, chromatographically purified rhenium-186(tin) hydroxyethylidene diphosphonate radiopharmaceutical have been completed in five patients with metastatic carcinoma to bone. The new agent localizes in metastatic foci in bone in the same manner as do standard technetium-99m diphosphonate bone-scanning agents and appears able to deliver therapeutic radiation doses of thousands of rads (tens of grays) to these metastatic foci while limiting the total red marrow dose to less than 75 rad (0.75 Gy). The simultaneous treatment of multiple metastatic foci in bone appears feasible with this new agent.

Adult↗
PubMed1986

The chemistry of rhenium and technetium as related to the use of isotopes of these elements in therapeutic and diagnostic nuclear medicine.

The beta emitting isotopes 186Re and 188Re are logical choices on which to base therapeutic radiopharmaceuticals that might be expected to be analogous to diagnostic radiopharmaceuticals based on 99mTc. However, the chemistry of rhenium is sufficiently different from that of technetium so that the development of Re radiopharmaceuticals often cannot be predicated on the known chemistry and biological behavior of 99mTc radiopharmaceuticals. The relevant chemical differences involve the greater stability of the higher oxidation states of Re (and thus the greater tendency of reduced Re radiopharmaceuticals to undergo re-oxidation to perrhenate), and the greater substitution inertness of reduced Re complexes. These differences are illustrated in the preparation and use of 186Re (Sn)-HEDP and 99mTc(Sn)-HEDP diphosphonate radiopharmaceuticals designed, respectively, for palliative therapy and diagnosis of metastatic cancer to bone, and in the preparation and biodistribution of tr[186Re(DMPE)2Cl2]+ and [186Re(DMPE)3]+, analogs to the potential myocardial perfusion imaging agents tr-[99mTc(DMPE)2Cl2]+ and [99mTc(DMPE)3]+. [HEDP = (1-hydroxyethylidene)diphosphonate; DMPE = 1,2-bis(dimethylphosphino)ethane].

Animals↗
PubMed1985

Radiation-induced thyroid disease.

Ionizing radiation has been demonstrated to result in a number of changes in the human thyroid gland. At lower radiation dose levels (between 10 and 1500 rads), benign and malignant neoplasms appear to be the dominant effect, whereas at higher dose levels functional changes and thyroiditis become more prevalent. In all instances, the likelihood of the effect is related to the amount and type of radiation exposure, time since exposure, and host factors such as age, sex, and heredity. The author's current approach to the evaluation of patients with past external radiation therapy to the thyroid is shown in Figure 1. The use of prophylactic thyroxine (T4) therapy is controversial. While T4 therapy may not be useful in preventing carcinogenesis when instituted many years after radiation exposure, theoretically T4 may block TSH secretion and stimulation of damaged cells to undergo malignant transformation when instituted soon after radiation exposure.

Adenocarcinoma↗
PubMed1983

Relation between effective radiation dose and outcome of radioiodine therapy for thyroid cancer.

We used a combination of radioiodine scanning and quantitative radiation dosimetry to evaluate responses to therapeutic irradiation with 131I in 76 patients with thyroid adenocarcinoma. Fifty patients received 131I treatment for ablation of residual thyroid tissue after surgical thyroidectomy, and 26 had 131I treatment for metastatic thyroid cancer. Successful ablation was observed in patients receiving higher radiation doses to the thyroid--about 4.4 times those in patients whose lesions were not ablated--largely because of a longer effective half-life of 131I in residual thyroid tissue in the patients with ablated lesions. Patients with metastases that persisted after 131I therapy tended to have more advanced disease and received significantly lower radiation doses per millicurie of administered 131I than did persons whose lesions responded to treatment. Initial 131I treatment resulting in radiation doses of at least 30,000 rad to thyroid remnants and 8000 rad to metastases was associated with a significant increase in the rate of response to therapy.

Adenocarcinoma↗
PubMed1983

Low iodine diet in I-131 ablation of thyroid remnants.

A low-iodine diet was developed for used in decreasing iodine intake and excretion in patients undergoing evaluation with radioactive I-131 for ablation of thyroid remnants as treatment for thyroid cancer. It has been demonstrated to effectively lower iodine excretion to less than 25% of basal values. Preliminary calculations suggest that such iodine depletion may be potentially useful in increasing the radiation dose per mCi of administered activity in I-131 ablative therapy.

Adenocarcinoma↗
PubMed1983

Radiation absorbed-dose estimates for the liver, spleen, and metaphyseal growth complexes in children undergoing gallium-67 citrate scanning.

Quantitative conjugate-view external counting techniques were applied to estimate the radiation dose to the liver, spleen, and metaphyseal growth complexes (distal femur and proximal tibia) for ten pediatric patients undergoing gallium-67 scanning procedures. The effective half-life of Ga 67 in these organs was approximately 78 hours. The dose per unit of administered activity for the liver and spleen was between 0.3 and 4.0 rad/mCi (0.08 to 1.08 Gy/GBq) and 0.5 and 7.0 rad/mCi (0.13 to 1.89 Gy/GBq), respectively. For the metaphyseal growth plates, the range was 2.3 to 14.3 rad/mCi (0.62 to 3.86 Gy/GBq).

Adolescent↗
PubMed1983

Pilot study on the absolute and relative bioavailability of Synthroid and Levothroid, two brands of sodium levothyroxine.

The absolute and relative bioavailability of levothyroxine was determined in young, healthy male subjects after administration of i.v. solution, p.o. solution, or one of two brand-name, commercially available tablets. The mean dose size was about 0.18 mg. Serum concentration-time data were obtained over a period of 50 h. The absolute bioavailabilities of the two tablet preparations were 66% and 72%, respectively.

Adolescent↗
PubMed1982

Familial elevations of total and free thyroxine in healthy, euthyroid subjects without detectable binding protein abnormalities.

Elevations of serum thyroxine without thyrotoxicosis or binding protein abnormalities have been documented in 8 of 13 family members, representing 4 generations. This syndrome appears to represent an elevated threshold for the amount of free thyroxine substrate required to maintain adequate T3 production form the peripheral monodeiodination of T4. It reiterates the need for a prudent re-evaluation of all clinically euthyroid patients with elevated serum thyroxine concentrations before concluding that they are indeed thyrotoxic.

Adult↗
PubMed1982

Semiautomated system for simultaneous assays of serum vitamin B12 and folic acid in serum evaluated.

We evaluated performance characteristics of a semiautomated radioassay system (ARIA II, Becton Dickinson Immunodiagnostics) for simultaneous measurements of vitamin B12 and folic acid in serum. The system requires off-line boiling of samples, which are then processed on-line. The automated process includes dispensing of boiled samples, tracers, and binders (purified intrinsic factor and milk binder); incubation, separation of bound and free ligands; elution; counting radioactivity of 57Co and 125I; and data reduction. Results were compared with those obtained by a manual method (Diagnostic Products Corp.). Although the nonspecific binding of the ARIA II is more than double that of the manual system, the precision values are comparable (within- and between-assay CVs are less than 8.5%). Values obtained with these two systems correlated well except that folic acid concentrations obtained with ARIA II tended to be lower at high folic acid concentrations. We observed no significant total carryover or drift in the semiautomated system.

Autoanalysis↗
PubMed1982

Stability of immunologic activity of human prostatic acid phosphatase in serum.

The stability of the immunologic activity of human serum prostatic acid phosphatase (iPAP;EC 3.1.3.2) under various storage conditions was evaluated. Although more stable than the enzymic activity of serum PAP, serum iPAP was inactivated rapidly at room temperature at neutral and especially at alkaline pH. Purified iPAP in a phosphate buffer (pH 7.5) was stable for at least three days at room temperature but showed instability similar to that of serum iPAP when added to heat-treated serum (30 min at 56 degrees C, pH 8.3). Addition of a protease inhibitor, a sulfhydryl agent, or a chelating agent failed to preserve iPAP. Acidification of serum with an acetate buffer (5 mol/L, pH 5.0), 20 microliters/mL of serum, protected but could not restore serum iPAP activity. When stored at 24 degrees C, serum iPAP was most stable at pH 6.5. Acidification had little effect on PAP values by radioimmunoassay, iPAP values from acidified and unacidified serum samples being essentially the same. We recommend that blood samples drawn for PAP immunoassays be kept at 4 degrees C and that serum samples be separated and acidified as soon as practical. For long-term storage, acidified serum samples should be kept in small aliquots at -20 or -70 degrees C.

Acid Phosphatase↗
PubMed1981

Clinical significance of serum vitamin B12 measured by radioassay using pure intrinsic factor.

Serum vitamin B12 (B12) levels of 53 patients (15 with pernicious anemia) and 42 healthy volunteers were determined using crude intrinsic factor (IF), pure IF, and a mixture of crude IF + R-protein blocking agent (block IF). The radioassay using pure IF showed less sample-to-sample variation in nonspecific binding than the radioassay using block IF. The mean B12 levels in 42 healthy subjects were significantly higher with crude IF (499 +/- 23 pg/ml, 1 s.e.m.) than with pure IF (408 +/- 29 pg/ml) or with block IF (407 +/- 22 pg/ml). B12 levels were abnormally low in all 15 patients with pernicious anemia by pure IF (less than 100 pg/ml), in 14 patients by block IF (less than 150 pg/ml), and in only seven patients by crude IF (less than 200 pg/ml). Our data confirm previous reports that B12 deficiency can be diagnosed more reliably by measuring serum B12 levels with etiher pure IF or block IF.

Anemia, Pernicious↗