Category Archives:Quality Control

Understanding The Difference Between kVp and mAs

Leave a comment Quality Control, Radiography

What are KVp and MAs?

To understand the difference between those two, you should first know that kilovolts (kV) and mAs are the two primary controls that we have with an X-Ray tube. They control the amount of radiation and the quality of the radiation beam or the X-ray beam.

In this week’s video, Eric from Olympic Health Physics talks about the difference between kilovolts (kV) and mAs and how each can be used because sometimes these two terms can be confused with each other.

What Does an X-Ray Tube Look Like?

The components that we’re going to be talking about with our X-Ray tube, in particular with kV and mAs is going to be the Heated Filament, the Anode which rotates around an axle or spindle and the Evacuated Chamber, which is where X-Ray production will take place.

Charges: Basic Electrostatic Force

Before we get too far into the operation of the X-Ray tube itself, let’s talk a little bit about charges

  • If we have two positive charges, they will repel from each other. 
  • If we have two negative charges, they will also repel from each other as we see here.
  • If we have two opposite charges, they’re going to be attracted towards each other.

The Anode And Cathode In an X-Ray Tube

If we apply those previous charges to the anode and cathode in an X-Ray tube, the cathode is held at a negative charge and the anode is held at a positive charge. When we put an electron in between the two, that electron is going to be attracted to or pulled towards the anode by the anode because an electron carries a negative charge. 

In conclusion, that electron is going to be pulled towards the anode and at the same time it’s being pulled towards the anode by the positive charges. It’s going to be pushed by the cathode because the negative charges on the cathode are going to repel or push the electron towards the anode.

The X-Ray Tube And The Heated Filament

In our X-Ray tube, the heated filament is going to boil off electrons.

The electrons are going to be created. If the filament is held at a negative charge and our anode is held out of a positive charge, the electrons will flow from the cathode towards the anode. Once they strike the anode, they will create X-Rays. 

We’re not really going into the formation of X-Rays and how they are formed, except to say that the interaction of the electrons with the anode will create two kinds of X-Rays.

How kVp is produced?

To understand how kVp is produced you should first know that within the X-Ray tube we can apply a potential difference.  This is a voltage difference between the cathode or the filament and the anode. This is where we create a potential difference. 

The bigger the voltage difference is or the stronger positive charge that we have on the anode, the stronger negative charge that we have on the cathode. 

The electrons will traverse the gap at a much higher rate. The velocity that the electrons accelerate across the gap of the chamber will be higher and higher as we increase the voltage of the tube. 

So that’s the voltage you’re seeing in the image above. If we have higher and higher energy electrons hitting the anode, the resultant X-Rays will also be higher energy. With higher energy of those, we end up with more penetrating power or the ability for the X-Rays to penetrate thicker and more dense body parts. 

In conclusion, the voltage difference between the cathode and the anode is kVp. 

As we increase the kVp or the voltage difference, we increase the speed at which the electrons traverse the chamber. They impact the anode at a higher and higher energy and create higher energy X-Rays.

If we decrease the voltage, then we will see a decrease in the energy of X-Rays and the X-Rays become less penetrating.

mAs: Introduction

mAs is milliamps seconds. It’s going to be directly proportional to the number of electrons that come off of the filament and are accelerated across the gap.

What exactly does that look like?

We have an X-Ray tube and we have a cathode. The electrons are moving across the tube towards the anode. It will produce a certain number of X-Rays with a certain number of electrons. If we increase the mAs, we increase the number of electrons and the number of X-Ray formed.

Remember that’s kVp, but we’ll increase the actual number of electrons and that’s going to increase the number of X-Rays.

So mAs is a control that’s directly proportional to radiation dose. If we double the mAs, then we’re going to double the radiation dose to the patient. 

What is mAs?

As was mentioned before, mAs is milliamp hour times seconds or times time. We can get rid of the “m” part and what we’re left with is just amps and seconds. 

What is an Amp?

An amp is just a Coulomb per second. 

What's a Coulomb?

A Coulomb is a unit of charge and electrons carry charge.  If we have our amps times seconds, that’s really just coulombs per second time because the seconds cancel out and we’re left with just Coulombs. 

Coulombs is a unit of charge and that’s going to be proportional to the number of electrons, which is going to be proportional to the number of X-Rays. 

So this is how we go from mAs (milliamp seconds) to the number of X-Rays. 

X-Ray Tube: Elements Explanation

Heated Filament

This is where the electrons come off and are accelerated towards the anode over this gap.

The Anode

The anode is going to be held at a positive charge and the voltage difference between the negative cathode and the positively charged anode. The higher that voltage difference is between these two, the faster the electrons will move from the cathode towards the anode and the higher energy the X-Rays will be that we produce. 

 And if we increase the mAs,  it’s going to be increasing the number of electrons that come off of the cathode and are accelerated towards the anode, increasing the number of X-Rays that are generated. 

kVp and mAs

kVp will control the penetrating power of your X-Ray beam or how energetic the X-Rays are and mAs will control the number of X-Rays. 

It is important to remember that If we increase the kVp or we increase the mAs, we’re going to see an increase in radiation dose. 

With increases in mAs, we’ll see better image quality in general. A better image quality because we’ll have less noise in the image. However, we want to weigh or balance the amount of mAs or radiation dose that we give against the resultant image quality

How Much Image Quality Do We Need?

We don’t want to just use as much mAs as possible. We want to be judicious with it because it does contribute to the radiation dose of the patient. 

Finally that was pretty much all you needed to know about the differences between kVp and mAs.

If you have any questions for us, feel free to drop them in the comments below and let us know how we can help. 

Click the image above to download the file

Our team is dedicated to ensuring that your facilities’ radiation safety program functions in accordance to regulatory standards, sound radiation safety principles, and most importantly serves to protect staff, patients, and the general public from the hazards associated with ionizing radiation. To this end, Olympic Health Physics can provide a physicist to your organization to fulfill the Duties of the Radiation Safety Officer. To learn more, check out our RSO Services or click the link below. 

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How To Use a Geiger Counter

Leave a comment Nuclear Medicine, Quality Control, Radiation Safety
How To Use a Geiger Counter

In this week’s video, Eric from Olympic Health Physics explains how to use a Geiger Counter. Throughout the video, he demonstrates the Ludlum 14C with a pancake detector. He provides an overview of how to test the battery, how to ensure the counter is working properly, and how to read the panel.

What Is A Geiger Counter?

A Geiger Counter or Geiger Meter is an electronic instrument used to detect and measure the amount of ionizing radiation levels. They are widely used in various applications, including radiation protection and safety, radiation dosimetry, and the nuclear industry. If you work in a Nuclear Medicine department, you likely have a Geiger Counter to measure radiation in different aspects, such as wipe tests, area surveys, or exposure rate measurements.

Three Essential Checks Before Using Your Geiger Counter

When you’re using a Geiger Counter, there are three things that you need to check before you start using it. Throughout this post, we will be showing the Ludlum 14C with a pancake detector. Please note that there are many different Geiger Counter makes and models, so check your user manual for specific criteria for your equipment. 

1. Is The Geiger Counter's Calibration Valid?

The first thing is you need to make sure that the Geiger Counter is in calibration. You need to look at the calibration label on it to make sure that it is still within calibration.

The calibration certificate usually includes the last date of calibration and the expiration date. The sticker also includes other useful information such as the model numbers, serial numbers, and efficiencies. 

Geiger Counter Calibration Certificate

2. Is The Geiger Counter Responding Appropriately?

The second thing that you need to do is make sure that the instrument responds to a radiation source.

On this specific instrument, we have a check source with a window that we can we can open. We can then put our pancake detector over the cesium button source located on the side of the instrument to ensure the instrument is actually responding to radiation.

3. Are the Batteries Operating Within the Test Range?

The last thing you want to do is check the batteries to ensure the batteries are operating within the battery test range.

To test the batteries, first remove the pancake detector from the front of the Geiger counter. Then, turn the Geiger counter on and turn the knob to the lowest range setting. Test the battery by depressing the battery button and looking to make sure that the indicator stays in the battery test range. As long as the indicator stays within the battery test range, the battery is operating effectively. 

Geiger Counter Battery Test Button

Understanding the Instrument Scale Readout

Understanding how to properly read the instrument scale readout is important to ensuring you have the correct information.

You’ll note on the Ludlum 14C Geiger counter instrument there are three different scales on the face of the survey meter. The first scale or the bottom scale is in milliroentgen per hour. You can also notice that the very bottom scale indicates “X100 ONLY”. The second scale or the mid-range scale is also in milliroentgen per hour. The upper scale that goes across the top  of the readout is in counts per minute.

Instrument Scale Readout

Below the instrument scale readout on the top of the meter are the various potentiometer values you can set for the Geiger counter. On this particular model, the Ludlum 14C, there are five potentiometer value setting options you can select. The value selected determines the multiplication factor for any reading that you see on the face of the survey meter. 

The bottom three options include X0.1, X1, and X10 coincide with the middle and top readout. X100 is used for the bottom readout only. And the X1000 option is used for the internal probe only. 

Potentiometer Value Options

To understand how the potentiometer options and scale readout work together, consider the following example:

You select the value of X1 from the options available. When you scan the radiation source with the pancake detector, the needle on the readout stops at blue line on the example readout photo. In this example, the appropriate reading would be on either the middle or top scale range, depending on what information you require. In addition, the potentiometer value is X1, meaning the multiplication factor is only one. Therefore, the value seen is the actual measurement. So for this example, the reading is either 4,000 counts per minute or 1.2 milliroentgen per hour.

Suppose you had selected X10 and the needle result was the same. You would them multiple your readout results by 10 to determine your final measurement reading. 

Sometimes on your survey meter, you may notice no deflection of the needle at all. If this happens, it can often be caused by having it set on too high of a scale. To fix this, flip down to the lowest potentiometer scale and you should start to see needle deflection. 

Audio and Speed

The Ludlum 14C Geiger Counter also offers two additional options: audio and speed.

To turn the audio on, flip the switch up and you will hear the audible clicks of radiation being detected. There is also a speed setting for fast or slow. The fast speed setting is good when looking for any kind of contamination. The slow setting is ideal when making a direct measurement of the check source. 

Audio and Speed Options
Click for a downloadable version.

So now you know the three things that you need to check before you use the instrument. Check the battery, check the calibration sticker to make sure that it’s still within calibration and check against a radiation source to make sure that the instrument responds to radiation. We also covered how to read the different scales on the Ludlum instrument so that you know which scales to use and how to use the the dial setting to select the right potentiometer on the instrument.

Questions and comments about radiation safety? Feel free to shoot them over to us. We’ll be happy to respond to any questions or comments that you have around radiation safety programs and be a resource for you.

Our team is dedicated to ensuring that your facilities’ radiation safety program functions in accordance to regulatory standards, sound radiation safety principles, and most importantly serves to protect staff, patients, and the general public from the hazards associated with ionizing radiation. To this end, Olympic Health Physics can provide a physicist to your organization to fulfill the Duties of the Radiation Safety Officer. To learn more, check out our RSO Services or click the link below. 

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The Duties and Responsibilities of the Radiation Safety Officer

Leave a comment Nuclear Medicine, Quality Control, Radiation Safety
The Duties and Responsibilities of the RSO

In this week’s video, Eric from Olympic Health Physics provides an overview of the duties and responsibilities of the RSO or Radiation Safety Officer.

This video covers the regulatory requirements and expectations of a medical RSO following the guidance in NUREG 1556, Vol. 9, Rev. 3. that is specific to medical licensees.

What Is a Radiation Safety Officer?

The Radiation Safety Officer or RSO is the person within a medical licensee facility who is responsible for overseeing and implementing the radiation safety program. They are the ones responsible for ensuring that the facility is compliant with all of the regulations and overseeing that radiation safety program.

Twelve General Duties and Responsibilities of the RSO

We’re going to go through some of the typical duties and responsibilities of the Radiation Safety Officer. It’s important to note there can be many additional duties assigned to the RSO. Below, we outline twelve general duties of the Radiation Safety Officer in relation to the regulatory requirements and expectations of a medical RSO following the guidance in NUREG 1556, Vol. 9, Rev. 3. that is specific to medical licensees.

1. Stop Work Authority

The first duty of the Radiation Safety Officer is Stop Work Authority. What does this mean?

It means that the Radiation Safety Officer has the ability to stop any work involving radioactive materials. This is usually spelled out in what’s called a Delegation of Authority that comes from the facilities administration and assigned by facility administration, as well as the Radiation Safety Officer. Stop Work Authority is usually used whenever there are unsafe work practices and something needs to be fixed or changed before the work can continue.

2. Overseeing the ALARA Program

The Radiation Safety Officer has a responsibility to ensure that radioactive doses are kept ALARA. ALARA is an acronym that stands for As Low As Reasonably Achievable. Within the facility, the RSO is responsible for ALARA and implementing an ALARA program.

3. Managing Radioactive Materials Usage

They also oversee all radioactive materials uses, including monitoring and surveying of all areas where radioactive materials are either used or stored.

4. Implementing Policies and Procedures

The RSO is responsible for drafting and implementing policies and procedures that deal specifically with the security of radioactive material, emergency procedures and operations that employ radioactive materials.

5. Training For Workers Handling Radioactive Materials

The Radiation Safety Officer typically conducts training for radioactive materials workers. They’re going to be providing training about the use and safety of radioactive materials within the facility.

6. Transportation, Delivery, and Radioactive Materials Limits

They are also  responsible for the safe transportation and delivery of radioactive materials. The RSO ensures the packages are checked in properly, that there are surveys of packages and all deliveries are documented. Radiation Safety Officers also ensure that the facility’s possession limits are adhered to. The possession limits are outlined in the radioactive materials license for the facility. The RSO is responsible for making sure that the facility doesn’t exceed radioactive material possession limits.

7. Dosimetry Program

The RSO is also going to oversee and potentially implement the dosimetry program. Dosimetry is how we measure or monitor radiation doses, such as occupational radiation exposure, for staff. 

8. Security of Radioactive Materials

Security of radioactive materials fall under the jurisdiction of the Radiation Safety Officer to ensure that any radioactive material is going to be secured from unauthorized removal. This is typically done in one of two ways. Either the radioactive material is going to be under lock and key of some sort, or it can also be under constant surveillance. So the radiation safety officer will be responsible for making sure that radioactive materials are secured in one of these two ways.

9. Documentation of the Radiation Safety Program

Documentation is a really big topic because any time we’re dealing with radioactive materials, we have to document most of the processes that go with them. Some of the documentation include surveys, inventory, receipt, and disposal of waste. All of these activities should be documented.

10. Liaison With Regulators

They’re also going to serve as a liaison with regulators and report any medical events or anything that’s a reportable event. The RSO will report events either to the state, if they’re in agreement state or to the NRC, if they’re not in an agreement state.

11. Managing the Radioactive Materials License

The Radiation Safety Officer may manage the radioactive materials license. This can include implementing any license conditions within the radioactive materials license, as well as submitting any amendments to the regulatory agency for changes to the license. Amendments are typically going to be for things like:

• changing an authorized user
• changing the radiation safety officer
• changing the address of the facility
• changing the name of the facility
• changing the proposed uses or the locations of those uses

All the above are typical things that would require submitted amendments.

12. Implement Corrective Actions

And lastly, the RSO implements any corrective actions for deficiencies or inefficiencies that are found in a radiation protection program, audits or external inspection conducted by a regulatory agency.

Duties of the RSO

So this gives you a high level overview of the duties and responsibilities of the Radiation Safety Officer. The RSO may have more duties than what we’ve listed here. It’s usually up to the organization on what those responsibilities and duties will be for the RSO, but this will give you a pretty good place to start to understand the role of an RSO.

Questions and comments about RSO duties? Feel free to shoot them over to us. We’ll be happy to respond to any questions or comments that you have around Radiation Safety Officers and be a resource for you.

Our team is dedicated to ensuring that your facilities’ radiation safety program functions in accordance to regulatory standards, sound radiation safety principles, and most importantly serves to protect staff, patients, and the general public from the hazards associated with ionizing radiation. To this end, Olympic Health Physics can provide a physicist to your organization to fulfill the Duties of the Radiation Safety Officer. To learn more, check out our RSO Services or click the link below. 

Contact Us for a No Obligation Quote

253-254-6988
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An ACR MRI Safety Manual Overview

Leave a comment Magnetic Resonance Imaging, Quality Control
An ACR MRI Safety Manual Overview

In this post, we are providing an overview of the 2020 ACR MRI Safety Manual.

In 2013, the ACR published a white paper on MRI safety, and then in 2020 there was an update to that white paper that came in manual form. The intent of this manual was to be used directly by radiology technologists and imaging centers to have policies and procedures that would be more directly applicable to safety in the clinical environment.

Most of the manual is essentially unchanged from the 2013 white paper. There are sections that are identical and there are other sections that are largely the same. Then, there’s been some changes since the 2013 white paper into the 2020 manual.

Watch the video below on our YouTube channel as Eric walks you through an overview of the ACR Safety Manual for Magnetic Resonance Imaging procedures. 

What Are The Significant Changes in The 2020 Manual?

The most significant change is the designation and delegation of duties of:

  • the MR MD or the MR Medical Director
  • the MR SO or the MR Safety Officer, and
  • the MR SE or the MR Safety Expert

The manual does a really good job of outlining a good MRI safety program structure with these three positions. 

Is The Manual a Requirement for ACR Accreditation?

One thing to point out about the manual is that even though it uses words like shall, will and must, the manual itself is not a requirement of ACR accreditation.

Whenever you apply for ACR accreditation or are inspected by an ACR inspector, they’re not going to check to see if you’ve implemented this particular manual. They’re going to look to see that you have safety policies in place. Those safety policies can be the ones out of the manual, which is the intent of them providing the MR Safety Manual. However, they can also differ from what’s in the manual. You are not necessarily beholden to the exact verbiage that’s in the manual, but it’s a really good starting point for developing your own policies and procedures for your specific MRI department.

ACR Manual on MR Safety

An Overview of the ACR Manual

The manual itself is 56 pages long. It’s quite a thorough manual and it provides excellent information on MRI safety. The idea behind it is that you use the manual and that you implement the policies and procedures in the manual, or at least some version of them in your own policies and procedures for your MRI department. You can find this MRI safety manual on the ACR website.

Table of Contents

The Table of Contents provides an overview of the manual’s general layout. You can see there are many different sections within the manual. Within these sections, there are specific policies or procedures that you’re going to need to be compliant with the ACR.

The Table of Contents from the ACR Manual on MR Safety
Example of MRI procedures and policies listed in the ACR Manual on MR Safety

Examples of Policies and Procedures

Within the safety manual, you can find policies or procedures on elements such as:

  • policies on personnel and non personnel
  • who MR technologists are
  • the differences between level one and level two trained staff
  • policy for screening right here staff as well as patient screening

We also have pediatric policy as well as policy for pregnancy. The manual cover things like sedation, as well as contrast policy. It covers implants, devices and objects and how we screen for them.

The manual discusses several things in the MRI environment, such as the different MRI zones, the MRI contrast agent safety and responding to codes. There is coverage on hearing protection as well as thermal heating. All of those topics are going to be found in the manual.

There’s also a new appendix. Appendix one talks about the organizational structure for the MRI safety program. Appendix two reviews facility safety designs. And Appendix three reviews emergency preparedness. 

And that’s a snapshot on the ACR MRI safety manual that came out in 2020. We’re sure there will be newer versions of this at some point in the future, but for now, this is a really good place to start and use as a resource for the development of your own policies and procedures in creating a safer MRI department for staff, patients and visitors.

If you have questions about the MRI safety manual or questions about MA safety in general, feel free to drop a comment or send us an email. We’ll be happy to take a look at your MRI department, talk about your policies and procedures and see how we might be able to help.

If you require assistance with your MRI safety program or MRI physics testing, please reach out or click here to learn more about our medical and health physics services. You can also always reach out to us if you have questions or want more information on why you should partner with us. 

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