H R Maxon

University of Cincinnati, Cincinnati, OH, United States

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Publications (60)340.41 Total impact

  • H R Maxon
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    ABSTRACT: Radioiodine-131 imaging is the traditional method of detecting residual or recurrent differentiated thyroid cancer. The stimulation of such tissues to take up radioiodine may be achieved either by complete cessation of thyroid hormone, by partial thyroid hormone withdrawal, or by the administration of recombinant human thyrotropin (TSH). Complete or partial thyroid hormone withdrawal may result in serum TSH concentrations adequate for radioiodine imaging in up to 90% of patients. When known or suspected recurrent or metastatic disease is not evident on radioiodine imaging, single photon emission tomographic imaging with either thallium-201 chloride or technetium-99m-MIBI compounds may detect up to 80%-90% of cancers at least 1 to 1.5 cm in size, although specificity is less than with 131I. Fluorine-18-FDG positron emission tomography is a somewhat less available but acceptable substitute for thallium-201 or 99mTc-MIBI imaging. Tumor foci that concentrate either TI-201 or 18FDG intensely with little or no 131I uptake appear to behave more aggressively than those concentrating 131I avidly.
    Thyroid 06/1999; 9(5):443-6. · 3.54 Impact Factor
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    ABSTRACT: Rhenium-188 (tin) hydroxyethylidine diphosphonate [188Re(Sn)HEDP] is a new radiopharmaceutical that localizes in skeletal metastases and emits beta particles that may be therapeutically beneficial. It was evaluated by in vitro and in vivo testing in the laboratory, in animals and in humans using 188Re from a variety of sources. It may be produced by a desk-top method developed previously for 186Re(Sn)HEDP using 188Re produced through neutron irradiation of either enriched 187Re or naturally occurring rhenium targets or the use of a 188W/188Re generator. So long as the mass of rhenium in the 188Re-perrhenate to be processed into 188Re(Sn)HEDP is at least 100 microg, satisfactory radiochemical yields and purity may be obtained by all methods. The 188Re(Sn)HEDP has biodistribution and radiation dosimetry characteristics that are similar to those noted previously for 186Re(Sn)HEDP and appears to result in similar benefits and toxicities in patients with skeletal metastases. External radiation exposure monitoring indicates that, only 4 hr after a therapeutic administration of 1110 MBq (30 mCi) of 188Re(Sn)HEDP, average exposure rates at 1 meter from the patient would be only 0.5 mR/hr. Same-day, on-demand, outpatient therapy of disseminated skeletal metastases appears to be feasible with 188Re(Sn)HEDP.
    Journal of Nuclear Medicine 04/1998; 39(4):659-63. · 5.77 Impact Factor
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    ABSTRACT: When macrometastases are delineated clearly using current radiographic techniques and/or physical examination and can be shown to concentrate 131I, the therapeutic activity to be administered may be determined quantitatively. Administrations of 131I that will deliver 30,000 rad to residual thyroid tissue or 10,000 +/- 2,000 rad to lymph node metastases will ablate them successfully 80% of the time, and bone marrow depression that is severe enough to require specialized treatment will be avoided if the whole blood dose from a single administration does not exceed 200 rad. When micrometastases are detected only by diagnostic radioiodine imaging and/or elevations of serum thyroglobulin levels, and when a clinical decision is made to treat them with radioiodine, then 131I may not be the isotope choice. With small lesions < 0.05 mm in diameter, the lower energy emissions of 125I therapy may be more suitable. With the advent of alternative methods of patient preparation for radioiodine therapy, empiric approaches that were derived from experience with endogenously hypothyroid patients will require full re-evaluation. Approaches based on quantitative radiodosimetric calculations will continue to be valid because they already consider individual differences in radioiodine kinetics.
    Thyroid 04/1997; 7(2):183-7. · 3.54 Impact Factor
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    ABSTRACT: Early diagnosis of osteomyelitis continues to be a clinical problem. Multiple imaging modalities are being used for the diagnosis of osteomyelitis, but none of them is ideal for all cases. The choice of modality depends on several factors based on an understanding of the pathophysiologic aspects of different forms of osteomyelitis. After a brief introduction outlining some basic principles regarding the diagnosis of osteomyelitis, pathophysiologic aspects are reviewed. Advantages and disadvantages of each imaging modality and their applications in different forms of osteomyelitis are discussed. The use of different imaging modalities in the diagnosis of special forms of osteomyelitis, including chronic, diabetic foot, and vertebral osteomyelitis, and osteomyelitis associated with orthopedic appliances and sickle cell disease is reviewed. Taking into account the site of suspected osteomyelitis and the presence or absence of underlying pathologic changes and their nature, an algorithm summarizing the use of various imaging modalities in the diagnosis of osteomyelitis is presented.
    European Journal of Nuclear Medicine 10/1995; 22(9):1043-63.
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    ABSTRACT: 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. 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. 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.
    Journal of Nuclear Cardiology 09/1995; 2(5):395-404. · 2.85 Impact Factor
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    ABSTRACT: 99mTc pentavalent dimercaptosuccinic acid [99mTc (V) DMSA], a useful agent for imaging thyroid medullary carcinoma and other tumors, can be reliably prepared by addition of NaHCO3 and then Na99mTcO4 to a commercial kit for 99mTc trivalent DMSA [99mTc (III) DMSA], followed by bubbling oxygen through the solution for 10 min. 99mTc (V) DMSA made by this method is radiochemically pure and stable for 24 h, and it gives a rat biodistribution similar to that of the agent made by previous methods. Clinical biodistribution and radiation dosimetry studies are planned.
    Nuclear Medicine and Biology 08/1995; 22(5):689-91. · 2.52 Impact Factor
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    ABSTRACT: A Monte Carlo model has been developed for simulation of dose delivery to skeletal metastases by the bone surface-seeking radiopharmaceutical 186Re (Sn)-HEDP. The model simulates: (1) the heterogeneous small scale geometry of the soft tissue/bone-spicule structure in the lesions as determined by histomorphometric measurements of histologic specimens, (2) the small scale spatial distribution of the radiopharmaceutical on the lesion bone spicule surface as determined by autoradiography, and (3) the 186Re beta and conversion electron decay spectrum and the associated charged particle transport within the modeled geometries. The results are compared with the commonly employed uniform lesion model, which assumes: (1) homogeneous lesion morphology, (2) uniform distribution of radioactivity within the lesion, and (3) complete energy deposition by charged particles within the lesion due to decay of this activity. Gamma and x-ray photons from the 186Re spectrum were assumed to escape from the lesion volume in both models. Results show a significant dependence on the bone volume fraction and hence on the histology of the lesion (lytic, blastic or mixed). The uniform lesion model calculations underestimate the radiation dose to blastic lesions by as much as a factor of 1.8. However, for lytic lesions with low bone volume fractions, both models provide similar dose values. These new model calculations provide a mechanism for optimizing treatment planning and dose response evaluations of therapeutic bone-seeking radiopharmaceuticals.
    Journal of Nuclear Medicine 03/1995; 36(2):336-50. · 5.77 Impact Factor
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    ABSTRACT: Thirty-one adult patients with clinical findings suggestive of pheochromocytoma were studied with I-123 MIBG. All patients had images obtained at 24 and 48 hours. Five patients had abnormal uptake proved to be because of I-123 MIBG avid tumors. The remaining 26 patients had no proven tumors and showed physiologic uptake in various organs. The 24-hour images were of high quality. In all cases, the 48-hour images contributed no significant additional information. Only in 1 patient did the 48-hour image add some certainty. Physiologic uptake was seen in the salivary glands, liver, G.I. tract, and urinary bladder in all patients (100%). Uptake was also observed in the lung and heart (90%), normal adrenal glands (32%), thyroid (29%), spleen (23%) uterus (13%), and neck muscles (6%). The authors' experience indicates that I-123 MIBG gives superior images compared to the previously used I-131 MIBG, that the optimum imaging time for adults is 18-24 hours, and that normal distribution patterns including uterine and neck muscle uptake should be familiar to physicians interpreting the studies.
    Clinical Nuclear Medicine 03/1995; 20(2):147-52. · 2.96 Impact Factor
  • Clinical Nuclear Medicine - CLIN NUCL MED. 01/1995; 20(2):147-152.
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    ABSTRACT: 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. 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). Thallium-201, MRI, and pentavalent DMSA provide adequate sensitivity for follow-up of selected patients with suspected recurrent noniodine concentrating thyroid carcinoma.
    American Journal of Otolaryngology 11/1994; 15(6):417-22. · 1.23 Impact Factor
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    ABSTRACT: Bone marrow depression following 131I therapy for metastatic thyroid cancer can occur in up to one-quarter of all patients so treated. An analysis was made of the 131I whole body (WB) retention and its relationship to activity in blood for 46 patients (45 adult, 1 adolescent in 49 total studies) to define the accuracy of utilizing WB external counting data as a predictor of blood dose in comparison to the more classical method which requires data from sequential blood samples. The mean percentage differences between blood dose estimates based on external WB counting and those calculated by the classical method lie within +/- 10%. The WB methodology provides a useful first-order approximation for hematopoietic dose estimates in adult patients undergoing 131I therapy for thyroid cancer.
    Nuclear Medicine and Biology 03/1993; 20(2):157-62. · 2.52 Impact Factor
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    ABSTRACT: For almost five decades, 131I treatment of thyroid cancer has been based empirically on administered activity rather than on actual radiation doses delivered. In 1983, we defined radiation dose thresholds for successful treatment. This report is concerned with the subsequent validation of those thresholds in 85 patients. The successful ablation of thyroid remnants occurred after a single initial 131I administration in 84% of inpatients and in 79% of outpatients when treatment was standardized to a radiation dose of at least 30,000 cGy (rad). Administered activities low enough to permit outpatient therapy could be used in 47% of the patients. Lymph node metastases were treated successfully in 74% of patients with a single administration of 131I calculated to deliver at least 8,500 cGy (rad). For athyrotic patients with nodal metastases only, success was achieved in 86% of patients at tumor doses of at least 14,000 cGy (rad). These success rates are equal to or better than those reported with empiric methods of 131I administration. The individualized treatment planning selectively allocates hospitalization and higher exposures to 131I to those patients who require them.
    Journal of Nuclear Medicine 07/1992; 33(6):1132-6. · 5.77 Impact Factor
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    ABSTRACT: Single intravenous injections of 30 to 35 mCi (1,110 to 1,295 MBq) of Re-186(Sn)HEDP previously have been shown to result in palliation of painful skeletal metastases from prostate cancer. There are no reports of patients receiving repetitive Re-186(Sn)HEDP therapy. We have followed two such patients who received multiple (five to seven) injections of Re-186(Sn)HEDP at 2-month intervals. Each experienced a sustained decrease in both pain and analgesic intake. The only evident clinical or biochemical toxicity was a mild progressive decline in their total platelet counts.
    Clinical Nuclear Medicine 02/1992; 17(1):41-4. · 2.96 Impact Factor
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    ABSTRACT: Rhenium-186 (tin)hydroxyethylidene diphosphonate (HEDP) is a new radiopharmaceutical that localizes in skeletal metastases in patients with advanced cancer. A single intravenous administration of approximately 34 mCi (1,258 MBq) resulted in significant improvement in pain in 33 of 43 evaluable patients (77%) following the initial injection, and in 7 of 14 evaluable patients (50%) following a second treatment. Patients responding to treatment experienced an average decrease in pain of about 60%, with one in five treatments resulting in a complete resolution of pain. The only adverse clinical reaction was the occurrence after about 10% of the administered doses of a mild, transient increase in pain within a few days following injection. Statistically significant but clinically unimportant decreases in total white blood cell counts and total platelet counts were observed within the first 8 weeks following the injection; no other toxicity was apparent. Rhenium-186(Sn)HEDP is a useful new compound for the palliation of painful skeletal metastases.
    Seminars in Nuclear Medicine 02/1992; 22(1):33-40. · 3.82 Impact Factor
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    ABSTRACT: 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.
    American journal of physiologic imaging 01/1992; 7(3-4):239-41.
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    ABSTRACT: Rhenium-186 (tin) hydroxyethylidene diphosphonate (HEDP) is a new radiopharmaceutical that simultaneously localizes in multiple skeletal metastases in patients with advanced cancer. A single intravenous administration of 30-35 mCi (1110-1295 MBq) is associated with a prompt, significant relief of osseous pain in about 80% of such patients. The efficacy of this new compound was evaluated further by utilizing a double-blind crossover comparison with 99mTc-methylene diphosphonate (MDP) as a radioactive placebo. The new rhenium compound resulted in a significantly (p less than 0.05) greater decrease in pain than did treatment with the radioactive placebo. Rhenium-186(Sn)HEDP appears to be a useful new compound for the palliation of painful skeletal metastases.
    Journal of Nuclear Medicine 11/1991; 32(10):1877-81. · 5.77 Impact Factor
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    ABSTRACT: 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.
    Radiology 08/1990; 176(1):155-9. · 6.34 Impact Factor
  • International Journal of Radiation Applications and Instrumentation Part B Nuclear Medicine and Biology 01/1990; 17(8).
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    ABSTRACT: This report provides dose-response models intended to be used in estimating the radiological health effects of nuclear power plant accidents. Models of early and continuing effects, cancers and thyroid nodules, and genetic effects are provided. Two-parameter Weibull hazard functions are recommended for estimating the risks of early and continuing health effects. Three potentially lethal early effects -- the hematopoietic, pulmonary and gastrointestinal syndromes -- are considered. Linear and linear-quadratic models are recommended for estimating cancer risks. Parameters are given for analyzing the risks of seven types of cancer in adults -- leukemia, bone, lung, breast, gastrointestinal, thyroid and ''other''. The category, ''other'' cancers, is intended to reflect the combined risks of multiple myeloma, lymphoma, and cancers of the bladder, kidney, brain, ovary, uterus and cervix. Models of childhood cancers due to in utero exposure are also provided. For most cancers, both incidence and mortality are addressed. Linear and linear-quadratic models are also recommended for assessing genetic risks. Five classes of genetic disease -- dominant, x-linked, aneuploidy, unbalanced translocation and multifactorial diseases --are considered. In addition, the impact of radiation-induced genetic damage on the incidence of peri-implantation embryo losses is discussed. The uncertainty in modeling radiological health risks is addressed by providing central, upper, and lower estimates of all model parameters. Data are provided which should enable analysts to consider the timing and severity of each type of health risk. 22 refs., 14 figs., 51 tabs.
    04/1989;
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    ABSTRACT: 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.
    Radiology 03/1988; 166(2):501-7. · 6.34 Impact Factor