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Biomedical subjects

M K Loken

Publications and source records attributed to M K Loken.

At least 37 records · Page 2Linked to original sources
PubMed1986

Aerosol penetration ratio: a new index of ventilation.

Superimposition of nuclear medicine scintigrams and standard radiographs provides a unique opportunity for merging functional information intrinsic to nuclear medicine images with the high resolution anatomic detail of radiographs. A newly developed image processing system allows the merging of two separate films of greatly varying sizes to form a single composite image. Subsequent quantitative analysis of the composite image may be performed. Using the superimposition technique, [99mTc]DTPA aerosol ventilation scans (4.5 X 4.5 cm) were superimposed upon chest radiographs (35.6 X 43.2 cm) in 17 cystic fibrosis (CF) patients. Subsequent quantification of the area of nuclear scan ventilation and the radiographic lung area was then performed. A new quantitative radiologic index of ventilation, the aerosol penetration ratio (APR), was defined. Linear correlation of aerosol penetration ratio with residual volume (RV) as percent of total lung capacity (TLC) measured by body plethysmography was good. We conclude that the APR has validity as a physiologic parameter which localized regional excessive residual volume and correlates well with RV/TLC, the "gold standard" pulmonary function index of obstructive airway disease.

Adolescent↗
PubMed1985

Clinical use of indium-111 labeled blood products.

Following the introduction of In-111 oxine as a label for blood cells by McAffee and Thakur in 1976, these procedures have become increasingly important in the practice of nuclear medicine. Of particular interest are studies involving the use of labeled leukocytes for the detection of focal infection. The clinical utility of labeled platelets is less well developed, although the use of platelets to detect the formation of thrombi in blood vessels and on vascular grafts and prostheses is gaining prominence. This report summarizes the techniques presently employed at the University of Minnesota for the labeling of blood products, and their clinical use. Consideration also is given to the desired expertise and cost factors involved in the labeling of leukocytes and platelets.

Abdomen↗
PubMed1985

Effect of ethanol on droplet size, efficiency of delivery, and clearance characteristics of technetium-99m DTPA aerosol.

With recent technical advances in aerosol technology, the study of regional ventilation using [99mTc]DTPA aerosol has become increasingly popular. Using a cascade impactor, we have assessed droplet size distribution from a newly designed nebulizer. Delivery efficiency of [99mTc]DTPA aerosol to normal subjects was improved 70% with a 10% concentration of ethanol in the nebulizer. Using filter paper fixed to the delivery end of the aerosol device, and varying ethanol concentrations from 0-10%, an 87% increase of deposited radioactivity is measured. Use of higher concentration of ethanol to the nebulizer solution did not further improve delivery efficiency. The addition of ethanol did not alter clearance characteristics of [99mTc]DTPA from the lung nor did it affect droplet size distribution.

Adult↗
PubMed1985

Cardiopulmonary diagnoses by nuclear medicine techniques--where we have been, where we are, where we are going.

In order to not only survive, but to carry out our mission in health care delivery, nuclear medicine procedures will have to be competitive with the many other techniques that are available for assessing cardiopulmonary structure or function. Our tests must also be shown to be cost-effective. According to the American Heart Association, cardiovascular diseases alone had an economic cost of 56.9 billion dollars in 1983. Of this enormous sum only a very small percentage could be attributed to the performance of diagnostic nuclear medicine examinations. In addition to the economic cost, cardiovascular diseases accounted for 51% of all deaths in 1980. Statistics from the U.S. Department of Health show that 8.26 million (26.3%) of the national noninstitutionalized handicapped are the result of heart conditions and hypertension. These statistics are especially tragic since cardiovascular disease tends to strike a large proportion of persons in their most productive working years. We must avoid becoming penny wise and pound foolish when we decide whether or not to perform diagnostic examinations. Information obtained from these tests can be used to evaluate the effectiveness of therapy (or lack thereof), determine those patients who are at greatest risk of subsequent events and, therefore, require the most intensive investigation and therapy, and similarly identify that population at very low risk of having subsequent cardiac events and, therefore, requiring little, if any, therapy and no further investigation. Is such an approach economically feasible? An estimated 1.5 million Americans will have a heart attack this year, and about 550,000 of them will die. Of these persons, 350,000 will die before they reach the hospital. This leaves 1,150,000 persons who will be hospitalized due to myocardial infarction. As an example, if every one of these patients had a GBP study, at an estimated cost of +350.00 per examination, the cost would be about +400,000,000 or 0.7% of the total cost of cardiovascular diseases. This figure would roughly double if either a 201Tl or GBP study was performed with stress. Thus, our examinations constitute only a small percentage of the overall cost of cardiopulmonary disease. If one of these tests results in even a day early CCU to general bed transfer, early discharge, deferment of angiography, or surgery, or long-term medical therapy, then they will be cost-effective. We believe that a strong case can be made for optimism about the continued growth and expansion of nuclear techniques.(ABSTRACT TRUNCATED AT 400 WORDS)

Cardiovascular Diseases↗
PubMed1983

Low level radiation: biological effects.

It is imperative that physicians and scientists using radiations in health care delivery continue to assess the benefits derived, vs. potential risk, to patients and radiation workers being exposed to radiation in its various forms as part of our health delivery system. Insofar as possible we should assure our patients and ourselves that the benefits outweigh the potential hazards involved. Inferences as to the possible biological effects of low level radiation are generally based on extrapolations from those effects observed and measured following acute exposures to considerably higher doses of radiation. Thus, in order to shed light on the question of the possible biological effects of low level radiation, a wide variety of studies have been carried out using cells in culture and various species of plant and animal life. This manuscript makes reference to some of those studies with indications as to how and why the studies were done and the conclusions that might be drawn there from. In addition reference is made to the handling of this information by scientists, by environmentalists, and by the news media. Unfortunately, in many instances the public has been misled by what has been said and/or written. It is hoped that this presentation wil provide an understandable and reasonable perspective on the various appropriate uses of radiation in our lives and how such uses do provide significant improvement in our health and in our quality of life.

Abnormalities, Radiation-Induced↗
PubMed1982

Multiple "cold" areas demonstrated on bone scintigraphy in a patient with neuroblastoma.

A "cold" or photopenic defect on bone scintigraphy is a well recognized phenomenon and has been described in several conditions affecting bone. An unusual case of multiple "cold" defects in a patient with stage IV neuroblastoma is presented. A follow-up scan with the patient in clinical remission shows resolution of these "cold" defects. The patient subsequently relapsed and again multiple new "cold" defects were noted on bone scintigraphy. The possible etiology of "cold" defects is discussed.

Bone Marrow↗
PubMed1981

In-111-labeled leukocytes in the diagnosis of rejection and cytomegalovirus infection in renal transplant patients.

Indium-111-labeled (In-111) leukocytes have been shown to be useful in the localization of inflammatory processes, including renal transplant rejection. Using previously reported labeling methods, 63 studies with this agent have been performed in 53 renal transplant patients. Indications for study included suspected rejection or cytomegalovirus (CMV) infection. Studies were performed in 33 men and 20 women, with ages ranging from 6 to 68 years. Autologous cells were normally used for labeling, although leukocytes obtained from ABO-compatible donors were used in three subjects. Rectilinear scanner and/or scintillation camera images were obtained at 24 hours after intravenous administration of 0.1 to 0.6 mCi of In-111-leukocytes. There was abnormal uptake of In-111-leukocytes in the transplanted kidney in 11 of 15 cases of rejection. In three additional cases of increased transplant uptake, CMV infection was present in two. Abnormal lung uptake was present in 13 of 14 patients with CMV infection. In four additional cases, increased lung uptake was associated with other pulmonary inflammatory disease. Increased lung activity was not seen in patients with uncomplicated transplant rejection. These results suggest that In-111-leukocyte imaging may be useful in the differential diagnosis of rejection versus CMV infection in renal transplant patients.

Adolescent↗
PubMed1980

The scintigraphic appearance of the spleen following splenic artery resection.

Sequential 99mTc-sulfur colloid scans were performed on 4 patients following resection of the splenic artery and vein during donor pancreatectomy. Immediate postoperative scans showed markedly decreased or absent uptake. Over a period of two weeks the appearance returned to normal in 3 and peripheral defects were seen in 1. A patient studied after splenic artery ligation for trauma also demonstrated prompt recovery. These studies show that the normal spleen can tolerate ligation of the splenic artery and vein.

Colloids↗
PubMed1980

Localization of radiolabeled mouse alloantibody in a sarcoma induced by 3-methylcholanthrene.

The distribution of twice-purified I-125-labeled alloantibody, prepared from the serum of strain DBA/2J mice obtained after immunization with strain C3H/HeJ spleen cells, was studied in immunosuppressed DBA/2J mice bearing either an allogeneic C3H/HeJ MCA sarcoma (i.e., one induced by 3-methylcholanthrene) or a syngeneic MCA sarcoma. Radiolabeled antibody was isolated from labeled immune gamma globulin by adsorption onto C3H/HeJ red blood cells and elution from stroma prepared from these cells, followed by Sephadex G-200 gel filtration chromatography. This purified antibody bound specifically in vitro to C3H/HeJ red blood cells. In vivo this antibody localized preferentially in C3H/HeJ MCA sarcomas. An enrichment procedure was developed to increase the yield of radiolabeled alloantibody. The localization of I-131-labeled alloantibody in allogeneic tumor was visualized by external scintigraphy. Control I-131-labeled normal DBA/2J gamma globulin did not show such tumor localization.

Animals↗
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↗