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Now, the last part of this lecture is on the radiation syndrome.

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What is radiation syndrome? We are talking about in terms of massive exposure or

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nuclear accidents. Nothing to do with the medical imaging.

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It is more of a very high level of radiation.

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Acute radiation syndrome is also called as ARS.

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This occurs when whole body is exposed to high level of radiation in a very

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short period of time, such as when the bomb hit the Hiroshima and Nagasaki, a lot

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of people died, and those who survived experienced this acute radiation syndrome.

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The ARS can occur when it's acute and the radiation exposure is acute, involves

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whole body, and from external penetrating radiations such as X-rays, gamma rays,

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and neutrons.

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The acute radiation syndrome is divided further into hematopoietic,

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gastrointestinal, and neurovascular syndromes in order of occurrence.

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This figure shows you different portion of the phases of the acute radiation

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syndrome. I'm talking about very high radiation dose.

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Radiation occurring at a particular point within zero to 48 hours.

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The patient or the subject or the population experiencing can go through what is

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called as a prodromal state,

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and they can experience anorexia, nausea, vomiting, diarrhea, and so forth.

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Similar to any other infectious diseases.

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That's why sometimes it is difficult to diagnose this when it happens.

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But once the patient has survived prodromal stage, within the next 24

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hours, there is a latent period, which is called the effect do not show they are

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absent or almost diminished. In the next hours to 30 days, you see what

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is called as a manifest illness stage, where the bone marrow can be shown

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depressed, leukemia, leukopenia, vascular damage, and so forth can occur.

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After 60 days, the body can either recover or can lead to death.

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Shown bottom here is a color diagram showing as dose increases, the

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severity of the effects also increases.

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The time to onset of manifest illness also decreases when the dose goes higher and

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higher. These are the trigger levels with whole body dose.

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For hematopoietic syndrome to occur, the whole body should get anywhere from one to

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10 gray. A GI syndrome require doses to be greater than six gray, but

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lethal within 10 gray. And neurovascular syndrome usually occurs after

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a dose of 50 gray. In this discussion, we also define what is called as LD 50/30,

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which I'm going to discuss later. But given here is LD 50/30 is three gray.

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So now let's examine the acute radiation syndrome.

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The prodromal stage occurs within hours after whole body dose of greater than one

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gray, and that can last for hours or few days.

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The symptom includes nausea, vomiting, diarrhea, abnormal decreases in the white

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blood cell. The severity of this symptom is dose related.

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The latent state or incubation state follows prodromal stage.

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That can last for a week during which no visible symptoms occur.

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However, it is during this period that recovery or lethal effects have begun.

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The second type of ARS is called the hematopoietic syndrome.

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When the whole body doses is gray from one to 10 gray.

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In this case, the red and white blood cells of platelets are depleted in the bone

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marrow, resulting in systemic effects such as infection, hemorrhage, anemia,

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and impaired wound healing, et cetera.

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The recovery chances are high for exposure less than two gray, but low and even

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fatal for those receiving whole body greater than eight gray.

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The next type of ARS is the gastrointestinal syndrome, and that can occur with

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doses greater than six gray, doses greater than 10 gray are almost lethal.

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The prodromal stage occurs within hours, followed by latent period lasting up to

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five days, and the death primarily occurs within three to 10 days with no medical

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intervention or last up to two weeks with intensive care.

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So these cases are very difficult.

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Best example is workers and firefighters in Chernobyl disaster died from this

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syndrome. So the last of the ARS is the neurovascular syndrome.

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This occurs with whole body doses greater than 50 gray.

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Remember, this is a whole body dose, not any portion of the body dose.

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Results in death within two to three days due to cardiovascular shock with massive

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loss of serum and electrolyte. Ensuing circulatory problems of edema,

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increased cranial pressure, and cerebral anoxia cause death before any other

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changes in the body become significant.

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Books regarding from the survival of Hiroshima and Nagasaki have documented few

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people who have experienced this neurovascular syndrome going bonkers

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when they're walking around totally dazed and totally lost, who later died within

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two to three days. And probably the reason may be because of this neurovascular

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syndrome. To capture all these things, here is acute radiation syndrome

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is grouped under deterministic effect because they occur within a very short period

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of time. And here is the time when acute radiation syndrome experience

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occurs upon exposure. There's the lapse of time here, prodromal stage, which can go

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between zero and 48 hours. The following are the example, nausea and vomiting,

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headache, diarrhea, fever, disturbance of consciousness.

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Incubation time can take between zero to three weeks, and the onset phase

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is increases in exposure dose. These effects can show up, and later it can either

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lead to repair or to death.

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So coming back to the concept of LD 50/30, it is basically defined as follows.

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It is a whole body dose of irradiation that can be lethal in 50% of exposed

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population within 30 days. That's what LD 50/30 means.

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Quoted also are 50/30, LD 10/30, LD 50/60,

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and LD 100/60. In all these description, the first number is what

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percentage of the population will die.

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The second number will tell you within what time frame.

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So LD 50/30 means 50% of the population will die over 30 days, within 30

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days, is what this LD 50/30 means. For adult humans,

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the LD lethal dose, which is 50/30, is three gray.

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Means if adult humans are exposed to 300 rads of exposure, the whole

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body or three gray of exposure, they can experience this lethal dose.

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The lethal dose for humans are usually given also as LD 50/60.

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Means 50% of the population will die within 60 days, and this is about three to

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four gray without any medical intervention. This is a radiation hazard scale.

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This is put out by the CDC recently, giving an opportunity how to communicate with

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the public about large radiation doses.

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And instead of giving numbers, they give a color-coded diagram, make it easier to

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communicate. Shown here is one and two are within the range of normal, everyday

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radiation level. That is the background radiation level.

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Two is called the above the range of normal, everyday radiation level, but no

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health effect are expected. Three is increased risk of cancer later in life, and

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which the symptoms may can take decades to occur.

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Four and five are the most dangerous one.