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Biomedical subjects

M K Loken

Publications and source records attributed to M K Loken.

At least 19 recordsLinked to original sources
PubMed1992

Nuclear medicine in the evaluation of organ transplants with special reference to heart and lung.

Organ transplantation has become routine in many hospitals throughout the world. Nuclear medicine techniques have played a significant role in the success of these programs through measurements of blood flow and function in these grafts, as well as assessments of infection and rejection. This paper emphasizes the present status of radiotracer methodology for evaluating heart and heart/lung transplants and also includes a brief summary of the development of nuclear medicine studies of other transplants.

Graft Rejection↗
PubMed1991

Radioiodine therapy in thyrotoxicosis.

One hundred and two patients (81 females, 21 males) suffering from thyrotoxicosis as diagnosed clinically and confirmed by laboratory investigations including the estimation of thyroid hormones in blood were treated with radioiodine (I-131) at the University of Minnesota Hospital between 1976 and 1986. Nine (9%) patients needed two and 3 (3%) patients needed three therapeutic doses of I-131. The age range of the patients was 17-82 years (mean 43, SD 17). The doses of I-131 administered ranged from 3.9 to 100 mCi (mean 13.7). Twenty of these patients received a relatively high dose from 20 to 100 mCi. The others were given smaller calculated doses based on radioiodine uptake and thyroid size is determined by palpation and nuclear scans. Of the 73 patients for whom follow-up information was available, 66 (90%) eventually became hypothyroid as judged by clinical criteria. These data also suggest that the incidence of hypothyroidism is quite independent of the dose (microCi/g thyroid) administered.

Adult↗
PubMed1989

Positron emission tomography (PET): a unique approach for the imaging of in vivo metabolism.

Positron Emission Tomography (PET) is a new diagnostic imaging modality which will be available for the study of patients in the greater Nebraska area beginning mid year 1989. This technology will provide unique information on regional function and blood flow in a variety of body organs. Our emphasis will be placed on the identification of the viability of heart muscle in patients suffering a myocardial infarction or following thrombolysis who are being considered for a bypass procedure or angioplasty. We will also use PET to identify epileptic foci and to aid in the diagnosis of Alzheimer's disease, and for the assessment of the efficacy of various treatments of brain and other organ tumors. Despite the relatively high fixed costs of PET, we are confident that the unique information provided by this technology will prove not only to be effacacious but cost effective as well. Thus reimbursement through medical insurance programs, including Medicare, is expected to occur for those studies identified above. Likely coverage for additional PET procedures, particularly in the evaluation of psychiatric disorders, will occur after efficacy and cost effectiveness of these studies have been demonstrated.

Brain↗
PubMed1979

Computer tomography, radionuclide imaging and ultrasonography in hepatic mass lesions.

The livers of 86 patients comprising this report were examined by both transmission computerized tomography (CT) and radionuclide scans (LS). Fifty-nine of them were also examined by gray-scale ultrasound (US). In a comparative study, the strengths and weaknesses of each modality were evaluated. CT demonstrated 85%. US 82%, and LS 73% of masses involving the liver. Because of better resolution and sectioning capabilities, together with stop-motion imaging, CT and US detected smaller and deeper mass lesions than did LS. However, LS was more informative in hepatocellular disorders than was US or CT. Our experience indicated that information obtained on the liver and surrounding structures by each imaging modality used here tends to be somewhat unique, and thus these procedures complement one another rather than being competitive.

Humans↗
PubMed1979

Mechanism of the hypocalcemic effect of mithramycin.

Mithramycin is effective in the treatment of hypercalcemia. The mechanism of its hypocalcemic effect was studied in six patients with hypercalcemia by serum 85Sr or 45Ca kinetic techniques. Mithramycin was given at two dosage levels (25 or 50 microgram/kg iv). Mithramycin at the low dosage had little effect on the rate of bone accretion. However, at both dosage levels, mithramycin caused an upward shift of the slope of the specific activity curve, indicating an inhibitory effect on bone resorption. This effect started 6-12 h after a 25-microgram/kg dose of mithramycin and lasted from 4-6 days. It appears that mithramycin has a preferential effect on bone resorption.

Calcium↗
PubMed1979

Ovarian imaging by the binding of radioiodinated chorionic gonadotropin: concise communication.

Previous studies have demonstrated the presence of specific, high-affinity receptors for human chorionic gonadotropin (HCG) in human and rat ovaries. In the present study, highly purified HCG was labeled with iodine-131 and used for the imaging of luteinized rat ovaries. Excellent images were obtained. The accumulation of radioactivity in the ovaries was completely inhibited by previous administration of excess unlabeled HCG. Time-course studies show that radioiodinated HCG was rapidly accumulated within 1 hr and largely cleared from the ovary at 24 hr. These results show the potential for imaging of endocrine target tissues by hormone-receptor binding, and the possibility of quantitation of hormone receptors in tissues under pathological conditions.

Animals↗
PubMed1979

Evaluation of three imaging instruments in dogs with liver hemotomas: concise communication.

Single-gamma emission computerized tomography (ECT) was compared with transmission computerized tomography (TCT) and scintillation-camera imaging (SC) in eight dogs with acute, solitary hematomas in the left liver lobe. The superior performance of TCT was attributed to its inherently better spatial resolution than those of ECT or SC, and to the fact that studies with TCT could be performed during apnea. ECT was more sensitive than SC to small changes in the spatial distribution of radionuclides. In addition, the ECT, by virtue of its sectioning capability, was more sensitive than is SC to differences in radionuclide concentrations at same depth in an organ.

Animals↗
PubMed1978

Scintigraphic visualization of myocardial infarcts in baboons using thallium-201 and technetium-99m pyrophosphate.

4 baboons with myocardial infarcts were evaluated using thallium-201 for myocardial imaging and 99Tcm pyrophosphate for infarct visualization. Scintiphotographic findings were compared with the size of myocardial infarcts calculated from measurements of the activity of MB isoenzymes of creatine kinase (CK-MB) in serum and in the myocardium at autopsy, as described by Sobel's method. Lack of thallium-201 accumulation was noted in left ventricular infarcts of 3 of the 4 baboons. These same areas localized 99Tcm pyrophosphate administered 24--30 h after infarction.

Animals↗
PubMed1977

Evaluation of early myocardial ischemia with thallium-201 in the pig.

Thallium-201 was found to be a reliable agent for detecting decreased myocardial perfusion in domestic pigs 1-4 hours after acute coronary occlusion. Substantial variation in myocardial-to-liver count ratios and diagnostic quality was observed in serial images performed in 3 normal pigs, although areas of 1-4 hours-old myocardial ischemia produced by acute circumflex coronary artery ligation in 6 pigs could be reliably detected by in vivo 201Ti imaging. After intravenous 201Ti administration, the animals were sacrificed and sections of normal and ischemic myocardium were counted in a scintillation well counter. The activity in the ischemic area in pigs averaged 12% of the activity in the normal area, and varied over a narrow range; in dogs the activity averaged 62% of normal, and varied over a wide range. The pig was a more consistent model than the dog.

Animals↗
PubMed1976

Use of 99mTc-sulfur colloid in evaluation of renal transplant complications.

Technetium-99m-sulfur colloid (TSC) was administered to 45 renal transplant patients. No TSC accumulation was seen in normally functioning transplant kidneys. Accumulation of TSC was found in 89% of transplants with rejection, in 30% of transplants exhibiting acute tubular necrosis, and in 30% of transplants of patients with sepsis. Renal accumulation of TSC in various transplant complications diminishes the value of this technique for monitoring transplant rejection.

Acute Kidney Injury↗