radiation Flashcards
Discuss measuring radioactivity
The absorbed dose of radiation is the amount of ionization energy depoisited in matter by ionizing radiation - one gray (Gy) is equivalent to one juole per kilo.
The sievert is the IU of effective radiation dose and is obtained by multiplying the absorbed dose measured in gray by a quality factor to reflect the different effects of each radiation type and their protentional biological damage.
For beta and gamma radiation 1Sv = I Gr. Alpha and neutron radiation deposit more energy in tissue so the quality factor is higher.
Briefly discuss types of radiation
ALPHA: composed of two protons and two neutrons these do not penetrate the dermis but may cause local damage if ingested inhaled or absorbed through open wounds
BETA: consists of electron like paritcles travels about a metre through the air and stopped by clothing. Often causes radiation injury to exposed skin
GAMMA - have no mass and are similar to x-rays penetrating the body freely and causing the acute radiation syndrome if the trunk is involved
Neutrons - are produced only during nuclear detonations and while they can technically make an irradiated victim emit radiation this is not clinically significant
List effective dose of common radiology investigations
The average natural background radiation is 2mSv per annum in australia
FLight 0.003 mSv per hour
XR
- Extremity – 0.001mSV
- Chest – 0.1 msV
- Lumbar spine - 1.5mSV
- IVP - 3msv
- Barium enema - 8 mSV
CT
- Brain – 2.0 mSv
- CT L spine- 6 mSV
- Abdo pelvis - 14 msv
- CTPA, 3 phase liver - 15
Nuclear med -VQ -- 2.2 mSv -Bone 6.0 msv -Thyroid 5.0 msv Myocardial perfusion 9.0 msv
Discuss briefly pathophysiology of radiation damage
Radiation damages tissues both directly and indirectly by the production of free radicals from water mooecules.
Direct damage to cell membranes may cause changes in permeability and the release of lysosomes. Germinal, haemopoietic and GI epithelial cells are relatively radiosensitive The cells of bone, liver kidney cartilage muscle and nerve tissue are relatively radioresistent.
Lethal injuries are threshold dependent - cells are killed when they receive more than a certain radiation dose which varies with different tissues. Clinical expression occurs when the amount of cell killing cannot be compensated for by proliferation of viable cells.
For sublethal there is no threshold and consequence is based on statistical probability. Sublethal injury to chromosomes is the important effect. Double strand breaks are not easily repairable especially if the damage occurs simultaneously this results in broken chromosomes wihtout a template for repair THe exposed ends of chromosome fragment may join up at random resulting in morphological chromosomal abnormalities. THis is implicated in tumour development.
The estimated increase in lifetimme risk of fatal cancer is 0.008%/mSv of gamma radiation. Therefore someone exposed to 100mSv of gamma radiation has a 0.8% increased risk of lifetime cancer.
Radiation can produce infertility in both male and female parties.
Describe the acute radiation sydnrome
Refers to the effects of radiation on one or more body system. The hemopoietic tissue alone is affected at doses of 1-4 Gy and produces pancytopenia with its consequent risk of infection. Above 6 Gt GIT effects are manifest and the prognosis is poorer. The neurovascular syndrome occurs with doses above 20 G and is manifest by leaky capillariers hypotension and a progressive decline in mental fucntion with eventual death in weeks to months.
Describe Clinical features of acute raidation syndrome
Divided into 4 phases
1) Prodromal phase which generally last 48 hours
- due to the effects of radiation on cell membranes and the release of vasoactive amines. THe symptoms are non specific
- anorexia, nasuea and vomiting, weakness, fever and conjunctivitis, erythema and hyperaethesia.
- The time to emesis presence of diarrhoea and duration of symptoms are markers of severity
2) a latent period lasting hours to weeks
3) the manifest illness period
4) death or recovery
Dose
- 4G (effect haemopoetic) - latent period 2-20 days than rapid drop in WBC and platelets. Recovery likley after about 30 days
- 6GY (GIT) -prodome more severe, early bloody diarrhoea suggest death within 2 weeks. GIT will recur ain the manifest period and are due to loss of stem cells in the crypts. It is superimposed on the haemopoetic effect
- 20 GY ( neuro) - characterised by leakage of fluid into tissues and hypotension. Latent period is just a few days. Leakage into the brain causes neurog symptoms. At very high dose >30G there is incapacitation usually wihtin the first few minutes and certainly wihtin 40
Can estimated dose of radiation via time to GIT symptoms
Discuss IX and Management of radiation injury
In general patietn who do not vomit within 6-8 can be managed as in an OPD setting.
Lymph count s every 6-12 hours for 48 hours. Fall of 50% in the first 24 hours suggestie of potentially lethal radiation exposure.
MANAGEMENT
- Supportive
- Early GCSF of likley greater than 2-3 Gr
- monitoring for neutropenia and treating if signs of infection;
- Platelet infusion early especially if possible need for theatre
PROGNOSIS
The LD 50/60 is the dose at which half the vitims succumb within 60 days. Without treatment the LD50/60 is 3.5 to 4 Gy With treatment this increases to aroun 5-6 Gy. Early GCSF and ICU increases this to 6-8 Gr
COMBINED INJURIES
- increased mortality
- decreased healing
- all blood products should be irradiated to remove t-cell populations.
- Platelts if <20 or <75 if surgery is planned.
Discuss patient contaminated with radioactive material
Preparation are similar to patient contaminated with any hazardous chemical. Radioactive contamination has the advantage that it can be readily detected by instruments when on the skin. In general survivors of radiation accidents have not been sufficiently contaminated so as to post a threat to ED or hospital staff.
Discuss scene management of radiation injury - have a look at disaster medicine
For incidents involving small numbers of patients members of the rescue team should put on protective clothing normally used by personnel working with the radioactive material a that site. This includes gloves, facemask and cap.
Serious illness or injury is not due to radiation per se and should be treated on its own merits. Unless the patients condition is serious external decontamination begins at the secene so as to minimize internal contamination and incorporation of the radionuclide into the body tissues and to reduce the risk of contamination of other persons and the hospital environment.
Discuss managing a radiation incident in the ED
Elements of planning are similar to those for other types of emergency, including prevention, preparedness response and recovery.
Facilities using unsealed radioactive sources should be identified in advance (nuclear med, scientific lab and nucelar facilities).
AN ED response plan should be developed and emergency response team membership dessignated. Equipment for monitoring decontamination and contamination control should be in place.
A Decon area must be designanted and its be cable of adequate decon
Hospital protocols should include plans for dealing with
- relatives
- press and public
Timely release of information is important.
