radiobiology VII Flashcards
what are the hematopoietic components?
what is the graph of bone marrow responses?
bone marrow responds to inflammation with prompt mobilization of hematopoietic precursors
what are the hematologic effects at 3.4 Gy?
-early drops in leukocytes, rise and fall in platelets are extremely sensitive markers, plummeting at 25-30 days
-after 30 days, their levels rise due to bone marrow mobilization
-the hematocrit and hemoglobin decrease while nucleated RBCs (reticulocytes) increase over 60 days
-infections may be cause of death if bone marrow response is lost
-note the platelet counts have a 3 times higher count compared to leukocytes
what is the ARS case#4?
-the first person to die of the ARS was a 26-year old male involved in a critically accident in Los Alamos in march 1945
-he was exposed to total body to a mixture of neutrons and gamma-rays, the estimated equivalent dose being 6.35 Sv
-his right hand received a much higher dose of 200 Gy and his left hand received a dose of 30 Gy
-his red blood count changed little up to the time of his death
-the platelet count dropped before being restored by a transfusion and then fell again
-there was the characteristic early initial rise in the granulocyte count, but it fell to eventually zero by the time of his death
what is classic hematopoietic syndrome?
-the most recent person to die of the ARS was ALexander Litvienko, a former officer of the russian security service who received political asylum in great britain and was assassinated by the administration of polonium-210
-this radionuclide emits only alpha-particles that do not penetrate even a sheet of paper or the epidermis of human skin, so alpha-emitters can cause a significant damage only if ingested
-litvienko fell ill and was hospitalized on november 1st 2006, and died on november 23, just more than 3 weeks later
-scotland yard initially investigated claims that he had been poisoned with thallium because the distinctive effects include hair loss and damage to peripheral nerves
-polonium-210 was identified only after his death
-the administered activity was estimated to be about 2 GBq, which corresponds to about 10 mcg of polonium and is many times the mean lethal dose
what is cutaneous radiation syndrome?
non-penetrating Beta-particles and low energy photons
-itching and tingling (3 Sv)
-epilation, erythema, edema (6 Sv)
-dry desquamation, wet desquamation, ulceration and necrosis (10 Sv) + infection
-chronic, possibly severe, skin infections and recurrent ulceration may complicate the process
-localized radiation burns to the skin differ from thermal and chemical burns primarily in the delay between exposure and effect, and their tendency to undergo recurrent breakdown, even after a scar has formed
what is triage?
the average time to emesis decreases with increasing dose
-if a person vomits <2 h then NLT 3Gy
-if severe immediate diarrhea is observed, it is probably a supra-lethal dose; no treatment is useful
-the decline in the lymphocyte count (48h) allows an estimate to be made of the total body radiation exposure
-lymphocyte chromosomal aberrations
-after high doses, of course, lymphocytes disappear quickly and so this technique has several limitations
when can a bone marrow transplant occur?
what is the summary?
what are some example questions
what are some radio-isotopes used in research?
chemical and physical properties of the isotopes determine their _________ (do radioisotopes behave differently than ionizing radiation?)
cellular, sub-cellular and tissue localization
these properties determine the ____________________ of the radiation dose and thus their acute biological effects (do radioisotopes behave differently than ionizing radiation)
micro (cellular) and macro (organ) distribution
-acute effects of a widely distributed radioisotope are similar to acute radiation syndrome corresponding to the absorbed dose
-tritiated water (H3) distributes freely in body water and produces lethality, anomalies, stunting in rats fed with tritiated water during pregnancy ( at 1-3 Gy)
the chemical properties of the radio-active decay end-product determine the long-term/chronic effects of the administered radio-isotope
-ex: Zn65 causes changes in bioelectric activity of rabbit cerebral cortex, heart function, serology and immune functions
-Pu238,239,240,244 and Ra 224,226,228 carcinogenicity potential
-bone cancers (osteosarcomas) after Sr90 administration (regardless of the route of entry)
-I132,133,135 but not I131 can cause thyroid carcinomas
-NEED TO DETERMINE THE BIO-DISTRIBUTION OF THE RADIOACTIVE DECAY PRODUCTS
what are in vivo radiotracer kinetics?
-tissue activity
-standard uptake value (SUV)
-standard uptake ratio (SUR)
tissue compartmental modeling
-binding constants (kon)
-dissociation constants (koff)
what is medical internal radiation dose (MIRD)?
what is the legend for the radioisotope decay table?
what are decay properties of radioisotopes used in diagnostics and therapy?
what is the energy and dose-deposition simulation of radionuclides?
