Stochastic vs Non-Stochastic Effects

I was asked a question about the difference between stochastic and non-stochastic effects of radiation, and I decided to make my answer public.

Everyone is concerned about how radiation dose affects their body. The way the human body responds to radiation dose (dose-response) is classified into two broad categories of health effects: stochastic and non-stochastic. Non-stochastic is also called deterministic.

Stochastic Effects
Stochastic effects are typically associated with long-term, low-level (chronic) exposure to radiation. The word "Stochastic" refers to the likelihood or probability that an effect will happen. In the diagnostic range of x-radiation that Radiographers and the general public are exposed to, increased levels of exposure make these health effects more likely to occur, but do not influence the type or severity of the effect.

The primary stochastic effects are: Cancer and genetic defects.

Cancer is considered by most people as the primary health effect from radiation exposure.

Radiation can also cause changes in DNA, the "blueprints" that ensure cell repair and replacement. Changes in DNA are called mutations.

Sometimes the body fails to repair these mutations or even creates mutations during repair. The mutations can be teratogenic or genetic. Teratogenic mutations are caused by exposure of the fetus in the uterus and affect only the individual who was exposed. Genetic mutations are passed on to offspring.

In summary, Stochastic effects are:

*totally random (occur by chance)

*appear in non-exposed persons as well as exposed persons

*No Threshold--any dose can cause an effect

*the likelihood of an effect increases as the radiation dose increases, but a single photon can cause an effect

*the severity of the response is independent of the dose (the severity of cancer is not associated with the amount of dose received. You are more likely to get cancer if you receive a higher dose, but the severity of the disease is not based on the dose)

Non-Stochastic (Deterministic) Effects

Non-stochastic effects are those in which the severity of the effect varies with the dose and for which a threshold value exists.

Non-stochastic effects appear in cases of exposure to high levels of radiation, and become more severe as the exposure increases. Short-term, high-level exposure is referred to as 'acute' exposure.

Many non-cancerous health effects of radiation are non-stochastic.

Unlike cancer, health effects from 'acute' exposure to radiation usually appear quickly. Acute health effects include burns and radiation sickness.

Radiation sickness is also called 'radiation poisoning.' It can cause premature aging or even death. If the dose is fatal, death usually occurs within two months. The symptoms of radiation sickness include: nausea, weakness, hair loss, skin burns or diminished organ function.

Summary of non-stochastic effects:

*Threshold--A certain minimum dose must be exceeded before the particular effect is observed. Because of this minimum dose, the non-stochastic effects are also called Threshold Effects. The threshold may differ from individual to individual

*The severity of the effect increases with the size of the dose received by the individual. (More dose more severe effect)*There is a clear relationship between exposure to radiation and the observed effect on the individual.

Examples of Non-Stochastic effects:

RTC 100--Powerpoint Presentation

View Presentation here:

Comparison of Meiosis and Mitosis

Mitosis Animation

RTC 201--The Cell Cycle

View and Chat

RTC 201--The Human Cell

View and Chat

RTC 100--Technique Chart

View Presentation here:

RTC 100--Group 6 Presentation

View the presentation and chat

RTC 100--Group 5 Presentation

Topic for Group 5

What factors are used to determine the quality of a radiographic image? What makes an image good, and conversely, what do people see when they look at an image and determine that it is bad?
Discuss the geometric factors and subject factors that affect image quality. Make sure to include images and diagrams to illustrate your answers and emphasize your key points

RTC 100--Group 2 Presentation

Topic for Group 2

Describe the various components of a typical x-ray tube. Make sure you have a clearly labeled diagram of the x-ray tube. What is the function of each component? What are the differences between a stationary anode tube and a rotating anode tube? Also discuss recent innovations in x-ray tube design. What design features have been introduced, and how do these new design features improve on what existed in the older tubes?

RTC 100--Group 1 Presentation

Group 1 presented information on the X-ray Operator Console.

Take a picture of a typical x-ray operator's console. Discuss each of the dials, switches, displays, and buttons on or connected directly to the operator's console. What is the purpose of each component of the console, and how does it impact the production of x-rays and/or the appearance of the radiographic image?

RTC 100--Group 3 Presentation

The first three group presentations went off successfully on Thursday, November 6th.

All the group members did well, and I am extremely proud of the effort that was made.

Below is group three's presentation. I will be posting each presentation online in the upcoming weeks.

Group 3's topic was:

Take pictures of the equipment in your energized x-ray lab. (Table, bucky tray, vertical cassette holder, grid, generator, high tension cables, tube housing, collimator, etc.) Describe the purpose of each bit of equipment in your x-ray room. Your discussion should answer the questions what does it do, or what is it used for?

Judge for yourself how well they did.

RTC 100--PowerPoint Presentation Topics Groups 7 & 8

The following topics will be presented on Thursday November 20, 2008.

Topic for Group 7

Provide details of the use of intensifying screens in Radiography. Use a diagram to discuss the details of the structure of an intensifying screen. Discuss the various screen-film combinations. Describe the handling and cleaning of intensifying screens. What is the result of poor film/screen contact? (Show an image) How is radiographic technique adjusted for variations in screen speed?


Topic for Group 8

Radiography has gone filmless. No film? Just as photography is now predominantly digital, radiography is heading in that direction as well. Discuss the major forms of digital radiography now in use. How do they compare to traditional (film or analog) radiography? For example, how has the introduction of filmless radiography affected Radiology department expenses, workflow, and number of repeats?

Do not get caught up with details of the technology or how digital radiography works. The intent of your presentation is to introduce the class to the current trend in imaging, and the advantages and disadvantages of going digital. Crucial questions that should be answered are: is it cost effective? Does it save on patient radiation dose? Does it expand the availability of images? Are there any adjustments that have to be made by the radiographer to their technique and the way imaging devices are handled? What about workflow? Are there any improvements in patient throughput when we go from film to filmless?

RTC 100 and RTC 201--Quiz 2

The second round of quizzes is scheduled for Friday, October 17th.

Check your e-mail for more details.

RTC 100--Power Point Topics: Groups 4-6

The following topics will be presented on Thursday November 13, 2008.

Topic for Group 4 (Christina)

What is the purpose of a radiographic Technique Chart? What are the four major exposure factors? Explain the adjustments that have to be made when each of the four factors is changed. In other words, what adjustments must be made to factors 2, 3, and 4 when factor 1 is increased or decreased?
What are the three major patient factors that influence technique selection? Show an example of a typical radiographic technique chart.


Topic for Group 5 (Mathew)

Answer the following questions in your presentation:
What factors are used to determine the quality of a radiographic image? What makes an image good, and conversely, what do people see when they look at an image and determine that it is bad?
Discuss the geometric factors and subject factors that affect image quality. Make sure to include images and diagrams to illustrate your answers and emphasize your key points



Topic for Group 6 (Winton)


List and discuss the three categories of Radiographic Image Artifact presented in chapter 15. Explain the causes of exposure artifacts using actual images to illustrate your answer. Describe the types of artifacts caused during film processing. Also discuss how improper handling and storage of film can cause artifacts. Show examples of the artifacts you discuss.

X-Ray Production--Bremsstrahlung and Characetristic X-Rays

Energy cannot be destroyed..its is tranformed from one type to another. This restatement of the principle of "conservation of energy" is demonstrated in the x-ray tube.

The electrons possess kinetic energy once they start to move. This kinetic energy is based on their velocity (K.E =1/2 x mass of the electron x velocity squared). When the electrons interact with the atoms of the anode target material their kinetic energy is transformed into electromagnetic energy (heat and x-rays).

The process is very inefficient---less than one percent of the kinetic energy results in x-rays.

Two types of x-rays are produced--Bremsstrahlung and Characetristic.





View the animations above. Distinguish between Bremss and Characteristic X-rays.

How is each type produced?

The diagram to the right shows the range of x-ray energies produced in a Tungsten target and their relative intensities. There are more photons at 59.3 kev, for example, than at any other energy level.

Distinguish between Bremsstrahlung and Characetristic x-rays on the diagram. Which type is more abundant? What is the range of energy values for each type?

X-Ray Production--The X-Ray Tube

X-rays are produced when fast moving electrons interact with atoms of a high atomic number target.

Whenever a potential difference is established between the cathode and anode of an x-ray tube the negatively charged electrons move rapidly from cathode to anode. The fancy physics term--potential difference simply means that the kilovolatge selected at the operator's console makes the anode highly positive with respect to the cathode.

Opposites attract---so the electrons at the cathode are strongly attracted to the anode and rush across at a very high velocity as soon as the potential difference is established (when you press the exposure button).

Whenever you select a higher kV the potential difference increases along with the energy of the electrons. This results in higher energy x-rays being produced.



In the video, the waveform diagram at the top of the screen shows how the voltage supply changes as the exposure progresses. The waveform shown is single phase, full wave rectified. The voltage varies in intensity from zero to peak intensity and back to zero in a repeating pattern.

Note that the x-rays produced (shown on the oscilloscope at the bottom of the screen) vary in intensity in a similar pattern to the voltage.

It is very important to understand how the various voltage waveforms (single phase or three phase) affect the quality and quantity of x-rays produced.

Electric Charge and Static Electricity

The existence of electric charge is based on the protons and electrons in the atom. The amount of charge on a single proton is equal to the amount of charge possessed by a single electron.

A proton and an electron have an equal amount but an opposite type (sign) of charge. Proton positve (+), electron negative (-). Thus, if an atom contains equal numbers of protons and electrons, the atom is described as being electrically neutral. On the other hand, if an atom has an unequal number of protons and electrons, then the atom is electrically charged (and in fact, is then referred to as an ion rather than an atom).

Any atom which contains less electrons than protons is said to be positively charged. Conversely, any atom which contains more electrons than protons is said to be negatively charged.

-Neutral or uncharged atom--Equal numbers of protons and electrons (p=e)
-Positively Charged Ion--Possesses more protons than electrons (Neutral atom lost electrons)
-Negatively Charged Ion--Possesses more electrons than protons (Neutral atom gained electrons)

The process of an electron leaving one material and moving to reside in another object is a common occurence. As clothes tumble in the dryer, electrons are leaving one bit of clothing and going to another. The object that loses the electrons will become positive, and the one that gains the electrons becomes negative.

When two dissimilar materials are rubbed together (friction) charges can build up in both materials. These charges are called electrostatic charges. Anyone who has felt the "zap" of an electric spark after walking across a carpet and then touching a metal door knob has experienced the effect of two objects rubbing together to create electrostatic charges.

These static charges can be useful, or a nuisance. They can even be downright dangerous. Watch the video clip below, and comment on what you see. (Post a comment on the blog by clicking the comment button at the end of this post)

What caused the dangerous event shown in the video?


In Radiography, electrostatic charges are sometimes discharged when the technologist handles the film before processing.

RTC 201--Power Point Presentation Topics

The following topics will be presented by the second year students on Friday, November 21, 2008. Grading Criteria for all Power Point presentations will be posted on this Web Log in a subsequent post. Keep checking in.

1. Discuss the structure of a human cell (There are many different types of cell in the human body so focus on the "generalized cell" that includes features from all cell types). Describe the purpose and function of each component of the cell. Include diagrams and images of the cell produced by the electron microscope.


2. The cell cycle is often described as a process of division allowing the duplication of cells. Discuss the various phases of the human cell cycle. Also, how does the process of Mitosis differ from the process of Meiosis

3. Discuss the effects of ionizing radiation on the human cell. Include the types of cell death, and other effects such as mitotic delay, reproductive failure, and interference of cell function

4. What is the role of each of the following organizations in Radiation Safety: (What are they responsible for, or what do they do)
-Nuclear Regulatory Commission
-National Council on Radiation protection and Measurements
-Food and Drug Administration
-International Council on Radiation Protection and Measurements
Which state agency in New Jersey is responsible for Radiation safety in the state? What is their role in ensuring that the public is protected.

5. Discuss the sources of radiation exposure to human beings. What percentage of exposure occurs from natural sources, and artificial sources? Compare the exposure levels from each of the following medical sources:
-diagnostic radiology (focus on CT and Fluoroscopy)
-dental radiology
-interventional radiology
-nuclear medicine
-radiation oncology

6. Discuss the various devices used to detect and/or measure radiation. Which device is used for each type of radiation and how does it work. Cover in detail the methods and types of personnel monitors. What are the dose limits for occupational, non-occupational, critical organs, embryo and fetus?

RTC 100--Power Point Presentation Topics

The following topics will be presented on Thursday November 6, 2008.

1. Take a picture of a typical x-ray operator's console. Discuss each of the dials, switches, displays, and buttons on or connected directly to the operator's console. What is the purpose of each component of the console, and how does it impact the production of x-rays and/or the appearance of the radiographic image?

2. Describe the various components of a typical x-ray tube. Make sure you have a clearly labeled diagram of the x-ray tube. What is the function of each component? What are the differences between a stationary anode tube and a rotating anode tube? Also discuss recent innovations in x-ray tube design. What design features have been introduced, and how do these new design features improve on what existed in the older tubes?

3. Take pictures of the equipment in your energized x-ray lab. (Table, bucky tray, vertical cassette holder, grid, generator, high tension cables, tube housing, collimator, etc.) Describe the purpose of each bit of equipment in your x-ray room. Your discussion should answer the questions what does it do, or what is it used for?

Geiger Muller Counter

A Geiger Muller counter is used to detect Radioactivity

Radioactivity--Alpha and Beta Particles...Gamma Rays

An Alpha particle is like the nucleus of the Helium atom. It has two neutrons and two protons bound together. Because of its composition, it has a much greater mass than the Beta particle which has the mass of an electron. Alpha particles have minimal penetrating ability. They are absorbed by a sheet of paper. However, their ability to ionize is extremely high (Ionization means their ability to break molecular bonds and to remove electrons from atomic orbits). The bottom line is, they are not able to penetrate materials but they do a lot of damage close to the point where they originate.

Negative Beta particles are similar in mass and charge to electrons. And although they have greater penetrating ability than Alpha particles their range is still limited. They can be absorbed by a sheet of aluminum foil. Beta particles cause ionization, but not as significant as Alpha particles. Beta particles vary widely in energy. Their ability to ionize depends on their Kinetic Energy as they leave the nucleus. In general, the ionization produced by Beta particles is spread out over a greater distance from the source (point of origin) than Alpha particles, but still in a localized area around the source.

Gamma rays originate in the nucleus as a product of radioactive decay, but they are quite different from Alpha and Beta particles. They are a member of the Electromagnetic spectrum. Therefore, they travel at the speed of light, and consist of photons which have no mass. Gamma rays have the ability to penetrate long distances from the source. It takes at least 7cm of lead to absorb Gamma rays. They are able to ionize material that is at a great distance from the source. However, their ionizing ability is less than that of Alpha and Beta particles.

RTC 100 and RTC 201--Quiz 1

Quiz 1 is scheduled for Friday September 26th for RTC 100 and RTC 201.

Anyone who hasn't signed up for gmail as yet may miss out on Quiz updates.

Once you have signed up for gmail send an e-mail to radprof08@gmail.com.

How to Learn Power Point

If you have never used Power Point before then the best way to progress is to open up the program on your computer and play around for a while to see how much you can learn on your own.

It is also a great group activity. If the group members get together and ensure that everyone in the group learns to use the program all the group members will earn credit.

For First year students: on Thursday, September 19, I will stay 30 minutes after class to see if you are making progress in learning Power Point and help you along if you haven't made progress.

For Second Year students: I will be available on Friday, September 20 after class for the same purpose.

Welcome to the Fall 2008 Semester

The ECC Radiography program has evolved over the summer months. A few changes have been made, and undoubtedly, as a result of these changes many of you are coming into this new semester with very high levels of anxiety. For those of you who are new to the professional portion of this program the trepidation may be at an all time high.

You can release a few of your stressful thoughts starting right now. Go ahead, exhale. Your education is in good hands. As long as you are willing to do your part by applying yourself, I will do my best to guide you in a direction that will lead you to success.

How do I define success? Delivery of quality patient care is the standard by which a successful radiographer is judged. If you can deliver that consistently you are successful. But what will it take for you to be able to reach that goal?

Knowing your craft, that's how. Being skilled and compassionate, that's how. The skill part I can help you with...the compassion part will have to come from you.

Radiography is a culture; and like any other culture it has its dress code, its conduct, its language, and its traditions. Welcome to the Radiography culture.

Learn to use Power Point

The power point presentation below was created by a Radiography student. The use of power point is a requirement in all my classes.