What is a RadiographyTechnique Chart for Rad Techs?
A standard Radiography technique chart is a written table that contains the following technical data to help radiographers obtain a consistent, standardized image while using the lowest radiation dose possible:
The body part imaged (hand, foot, skull, etc)
The kV or kilovolts required for the image (how strong of a beam)
The mAs or milliamperes per second (how long the beam emits)
Whether or not a grid is used (helps filter out scattered energy)
An “S” value or Sensitivity value (a key quality indicator)
For a portable technique chart you cand take with you, visit this link. To download a copy of my printable radiography techniques chart template, please visit this page.This particular template can be considered a universal radiography technique chart as well as a standard digital radiographic technique chart.
Below is a video representation of this article:
What is the purpose of a radiography techniques chart?
To list the exam parameters needed to obtain an optimal x-ray image, including kVp, mAs, SID, body part and patient size.
This chart is vital in the medical imaging field. It is used to image animals in a veterinary setting and humans in the medical setting. So, what is a technique chart? It is basically, a list of data that contains radiographic examination parameters used during the acquisition of an image. When a radiographer performs an x-ray examination on a patient, they have to set specific parameters on the x-ray equipment.
For instance, if you injure your leg in an accident and a doctor wants to know if you broke your leg, it needs to be examined with an x-ray. By getting an x-ray image, the doctor is able to see all the bones of the leg and determine if it is truly broken or not. A broken bone is called a fracture and could need medical treatment.
The chart contains all the different parameters or technical factors that the radiographer needs to capture a diagnostic image. Having a chart containing established technical parameters prevents technologists from the need to stop and calculate all of the components needed for a high-quality image by hand with each exposure. This is a great tool for pediatric chest x-ray technique charts. It also works for a suitable portable x ray techniques chart.
What is the importance of radiographic image quality?
An image produced resulting in nondiagnostic quality is useless to a radiologist. Poor image quality often requires a repeat of this image which gives the patient more radiation dose.
It is important that the image is of diagnostic quality. Inappropriate use of technical parameters during the capturing of an x-ray image could render the image completely useless. Or worse, it could hide the underlying problem by not properly identifying it. This could lead to a patient’s condition to become worse over time because the problem was not identified.
In these cases, the x-ray has to be repeated to capture a better image. But every repeat image gives the patient more radiation which we would like to avoid. That is why having a technique chart on the wall can help to choose the right technical factors to get the x-ray image done right the first time.
These x-ray technique charts are good for any body part. It also helps technologists abide by one of their fundamental underlying directives called ALARA. This stands for As Low As Reasonably Achievable. It directs us to capture images while using the lowest dose of radiation possible but still obtains a diagnostic image.
What is on the x ray techniques chart?
A standard technique chart contains several different pieces of information:
Object to be imaged – It lists the body part or parts that are to be examined like a skull, hand or foot.
Beam strength – The chart records the X-ray energy in kilovolts peak (kVp) that should be used during image capture. The kVp is the strength of the energy beam that is directed at the object being imaged.
Beam exposure time – The chart also contains a place to designate exposure time in milliamperes per second (mAs). The mAs is what tells the x-ray machine the length of time to emit the radiation beam.
Body habitus – The chart also contains the size of the patient or body habitus. For instance, it could have indicators for small, medium and large patient body habitus. A large patient will require stronger energy to penetrate the tissue whereas a smaller body type will require less energy. This is denoted on the illustration below on the far right columns labeled Small, Medium, and Large.
Grid use – Grids can be placed between the patient and the image receptor to reduce the scattered radiation (produced mainly by the Compton effect) and thus improve image contrast. Use of a grid depends on the size of the body part being imaged.
S# – The Sensitivity number is a value that represents the exposure received by the receptor in the imaging system. It represents key-value monitoring that a quality radiograph is obtained with the least amount of dose to the patient. The value is automatically recorded by the x-ray machine software for every exposure taken. The machine vendors help in establishing what a proper S number should look like on your machine.
What is mAs in radiology?
It stands for milli-amperes per second
Milliampere-seconds are a measure of radiation produced (milliamperage) given over a set period of time (seconds) from the x-ray machine.
What is kVp in radiology?
Peak kilovolt or Kilo Volt Peak
Kilovolt Peak or kVp is the technical factor known to control the quality of the x-ray beam produced by the machine. It also controls the contrast or grayscale of the ray image produced. The higher the kVp, the lower the contrast.
What is the 15% Rule in radiography?
The method of changing the kVp by 15% in either direction, up or down, which causes a doubling or halving of the mAs by 50%.
Effectively, when you change the kVp by 15%, either up or down, it is the same as doubling or reducing the mAs by 50%, depending on which was you changed the kVp.
What is radiographic contrast?
The degree of density difference between two areas on a radiographic image.
You’ve heard of 50 Shades of Gray? Well, in radiography, there are up to 65,536 shades of gray in a radiology image produced in radiography or computed tomography (Kimpe 2007). The monitors, however, that the radiologists use to diagnose the images only go up to 256 shades of gray.
How we post-process those shades are what determines the level of contrast between densities in the image. Using a chart like these as your chest x-ray technique chart will help dial in your diagnostic quality.
What does an x ray techniques chart look like?
Here’s an example of a fuji x ray technique chart:
Over time, you can customize this blank x-ray techniques chart to suit the specific X-ray machine that you are using. As examinations are completed and techniques are used, the radiographer will begin to make notes on the technique chart. These notes will indicate whether the kVp or mAs was too high or too low. A more accurate technique will be written on the chart so that as time passes the outcomes continue to improve.
You can see at the top of this sample chart, the parameters for using this as an x-ray technique chart for spine or even a chest x ray technique chart.
The history of the x ray techniques chart
Imagine the possibilities and excitement that surfaced when a physics professor back in 1895 realized there was a noninvasive way to see the bones of the human body. Non-invasive means you don’t have to cut open the body to see inside of it. It all goes back to November 8th, 1895. A physics professor named Wilhelm Conrad Rontgen discovered radiography while working in a darkened room in his laboratory.
He was experimenting with electrical charges flowing through a vacuum tube when a piece of paper coated with barium platinum cyanide began to glow next to him. By happenstance, it had been left near a cardboard covered tube. This leads him to conduct experiments with the fluorescent paper and the charged tube. That’s when he discovered that if he held his hand between the cardboard tube and the coated paper, he could see the silhouette of his hand bones on the paper. Eureka!
His research showed that x rays could penetrate human tissue. The German professor coined the radiation as unknown at the time. Thus, the value of “X “ in X-ray was born.
Rontgen first used radiography on his wife’s right hand. He used the rays and got a visible picture. He would write down the different technical factors that he used and note the quality of the image produced. Thus, the technique chart owes its origin to basic experiments. Using this technique of tracking improvements and writing down the change in parameters that lead to better imaging keeps the world of radiology moving forward at a fast pace.
From Wilhelm’s experiments, other radiographers around the world began to use the same techniques. In England, radiography was used in 1896. A doctor named John Hall-Edwards used it to trace a needle inside a hand. His colleague was pricked by a needle and it got stuck. Surprisingly, he was able to get a visual on the foreign body. The medical practice then spread to the United States.
Types of X Ray Techniques Chart
There are four types of radiography technique charts. The x-ray machine technique charts are used on different types of patients. You can adjust them according to the clients’ condition or history. They include the following;
-Automatic exposure controls
The technique chart uses fixed mAs. As for the kVp, it varies depending on the thickness of the part. Each anatomical area has an established plus factor and is measured with calipers. This means that the kilovolt varies at 2kVp at 2 cm thickness. This kind of medical imaging has a short scale contrast. Accordingly, the patient dose will be high. As for the exposure latitude, it tends to be less. Only the kVp is changed, all other factors are constant.
Advantage: background density will always be adequate as long as penetration is adequate. These charts are easy to construct.
Disadvantage: the scale of contrast will change slightly from patient to patient. This tends to encourage lower kVp values. It produces a relatively short scale of contrast and has reduced exposure latitude.
Fixed Kilovoltage (shown a fixed kVp technique chart)
This method is widely used in the medical profession. The chart highlights the maximum kVp. It then controls the mAs to the part thickness. It results in a long scale contrast. The patient’s dose is low due to the high kVp. The latitude here is great. Therefore, the exposures are consistent and accurate. The object being imaged can be measured with calipers and the mAs is selected from the chart. Only the mAs is changed and all other factors are constant.
Tips: To adjust the mAs, you can change the kVp by 2 cm thickness. For example, you can reduce the mAs by 30% for small anatomy. The large anatomy requires an increase of 30%. In other cases, if there is a swelling in a part, raise mAs by 50%.
Advantage: the scale of contrast is relatively constant for each examination. Exposure latitude improves and produces very consistent results. this method generally requires higher kVp settings than a fixed kVp technique chart but it reduces patient dosing by decreasing the mAs.
This method is mainly used for routine chest radiography and barium studies. The kVp is high and generally set greater than 100. Thickness can be about 21 cm. On that account, it has the highest exposure. It results in more exposure latitude, reduced patient radiation dose and produces less heat in the anode.
Automatic Exposure Controls (AEC)
The AEC is an exposure termination mechanism. It signals the machine to stop emitting radiation when a predetermined amount of radiation has been received. It works by terminating the exposure when the optical density is achieved. This setting allows the technologist to record one good AEC technique and never have to set manual techniques for speed again. It is consistent and achieves ideal density when used properly.
Computed Vs Digital Radiography
To begin with, computed radiography (CR) is analog and antiquated. Digital radiography or DR is the new process. They both have unique differences. Computed radiography uses cassettes to produce an image. On price matters, CR is more economical than digital radiography. The images that the CR produces are of lower quality. If the cassettes are not well-stored, it affects the standards. The radiographs get distorted with scratches. Also, it takes a while to process and view the images.
Digital radiography, on the other hand, has higher quality images. It uses an automatic image transfer to the computer. You can use a USB to move the content. The DR is pricey in terms of cost and maintenance. You can acquire the image much quicker. The radiation dose is about 20% less than the CR and has become part of a mandate by the Centers for Medicare Services that all facilities advance to this technology.
How to use an x ray techniques chart
A technique chart is easy to use. By now, you know the basics. Let’s delve into more details. To choose a quality kVp, you should first evaluate your patients. What are their medical histories? Do they have serious underlying conditions that could affect the beam penetration? Finally, you need to evaluate the patient’s body habitus. Thus, the type of kVp is solely determined by the patient. With the baseline data, you can reduce the patient dose or mAs. Low kVp produces whitewashed images. Also, too high kVp results in dark radiographs.
Also, the kilovolts will depend on the anatomy. By this, it is about the size or body habitus. You can adjust according to the body part too. An example is that for big anatomy, you need high kVp. You might need to increase the mAs by about thirty percent. If it is small anatomy, lower the mAs by 30%. This will guarantee you a better penetration.
Thus, if you need to examine athletes, keep in mind that they have stronger, denser muscle tissue. This means that you may have to increase the kVp. In contrast, infants and children have soft tissues and muscles. They need low radiation techniques. For this reason, you need to use a lower kVp than adults.
To get the best out of the chart, consider the following.
-The tissue type in the body
-The X-ray machine caliber
-The screen system that you are using.
Benefits of using the x ray techniques chart
X ray technique charts come with a lot of advantages. As a technologist, you can reap great benefits Here are some of the basic benefits:
1. Top-notch images
With a standard technique, the images will be of reproducible quality. This means that they are precise and consistent. If you do have to repeat an image, you can prevent future nondiagnostic quality images by recording what techniques finally worked with a difficult or unusual patient. This helps save time and money. The x-ray technique chart is a one-touch process.
With an x-ray technique chart, you can view the images more quickly than if you were manually calculating techniques. If you are using an AEC, it’s even better. This is also beneficial to patients because they don’t have to wait for long. Shorter exam times mean more patients can be examined in a standard work shift.
3. Suitable for busy clinics
Due to the efficiency, you can use the x-ray technique charts in big facilities where volumes are high. A common problem with busy facilities is dissatisfied patients due to waiting times. Technique charts help to speed things along a let technologists focus more on patient care and less on the technical factors needed for each exam.
The chart is versatile for all patients, equipment, and environments. They could be used with pediatric or geriatric patients. You can adjust the settings to suit the patients’ needs in a doctor’s clinic or busy hospital environment. This also translates to higher patient safety due to reduced repeat exams.
5. Easy usage
The technique cart involves simple controls. As a technologist, you can make changes as needed without any need for special access to machine software. The chart clearly outlines what techniques are needed for optimal imaging. A well thought out technique chart will last the duration of the equipment.
Xray technique charts provide a method of recordable, reliable consistency in the quality of image production. Technologists who use technique charts benefit from lower repeat rates. This keeps patients safe from too much radiation exposure which technologists strive for through the ALARA principle.
Over time, experiences technologists will know the information on the technique chart from memory and not have to refer to the chart. However, there will always be new technologists entering the field of radiography and that is why technique charts will always have value in the healthcare system.
This chart is universal for the following charts:
General x ray technique chart
Chest x ray technique chart
Abdomen x ray technique chart
Fixed kVp technique chart
Computed radiography technique chart
Radiography technique chart
kVp and mAs technique chart
digital radiographic technique chart
pediatric x ray technique chart
Fuji CR technique chart
Kimpe, T., & Tuytschaever, T. (2007). Increasing the number of gray shades in medical display systems–how
much is enough?. Journal of digital imaging, 20(4), 422–432. doi:10.1007/s10278-006-1052-3
Ron is huge radiology nerd. It started with Xray school at Pima Medical Institute in Mesa, AZ. He was crosstrained in CT during his Xray clinical rotations at Mesa General Hospital. Then immediately returned to school for ultrasound at Gateway Community College as he started his first job as an Xray/CT Tech. Not much later learned MRI out of necessity at his small rural hospital in Apache Junction, AZ. A decade later he found himself as a manager in a level one trauma center. Currently he is a system operations director over an entire hospital system and loves every minute of it.
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