why the measurement of part thickness is critical to the accurate use of technique charts

why the measurement of part thickness is critical to the accurate use of technique charts

Objectives

1. Explain why the measurement of part thickness is critical to the accurate use of technique charts.

Technique charts provide pre-installed guidelines that allow radiographers to reduce repeats and limits the exposure to the patients to an appropriate level.  The technique uses a standard manual that is used in individual examinations, thus maintain constancy in quality.

2. Describe the basic components of the human body.

The human body is composed of water that accounts for 60%-90% of cell structure and other body fluids. Proteins, minerals, carbohydrates, and fats form the remaining tissue. The body is composed of a set of six elements that make up 99% of the mass. These elements are oxygen (65%), calcium (1.5%), phosphorus (1.2%), carbon (18%), nitrogen (3.2%) and hydrogen 9.2%). The remaining 0.85% is made of combined elements, including sodium, sulfur, magnesium, potassium, and chlorine.

3. Differentiate how attenuation of the radiograph beam differs in human tissues and body parts.

The differences between human tissue and body part attenuation is contrasted by the densities and the differences in tissue thickness. The density of the tissue will determine how much the X-rays are attenuated.

4. Explain the effect that a pathological condition can have on radiation absorption and the radiograph image.

Pathological conditions end up affecting the human body and introducing various structural, functional, and compositional aspects of tissues. They, therefore, affect the general thickness of body tissue as well as the composition which influences absorption. The result of an examination will, therefore, be different due to the addition of variations due to the effects of the disease.

5. Differentiate between pathological conditions, which result in increased attenuation versus those which result in decreased attenuation of the x-ray beam.

Additive pathological conditions cause an increase in tissue thickness and composition, which leads to more attenuation of X-ray beams. An example of such a condition is pneumonia that causes lung tissue to be filled with fluid, which absorbs more rays compared to air. Destructive pathological conditions, on the other hand, reduce the tissue thickness, thus reducing attenuation of x-ray beams. An example is emphysema that increases the air in lung tissue that results in lesser attenuation.

6. State the effect of using three-phase equipment on technical factors and patient dose.

The phase X-ray systems produce high-frequency beams that have a short exposure time of 1ms. This equipment has high effective energy increased loading and a general reduction in motion and image blur. The quality of the image is, therefore, better compared to single-phase equipment.

7. Explain the function and operation of a falling load generator.

Falling lead generators produce X-ray exposure and limit the exposure to the shortest possible time. This generator operates the x-ray tube during the exposure period at the highest possible kilowatt rating.

8. Describe the principles of fixed kVp technique theory.

The kvp is maintained at a constant in a specific range of substances with specific densities, while the mAs is varied depending on the image.

9. Discuss the primary advantages and disadvantages of fixed kVp technique systems.

Fixed kvp reduce the X-ray dosage received by the patient while providing a consistent production of a quality image. In addition to the reduction of wearing of X-ray tubes, image receptor exposures are also consistent when using fixed kvp.

10. Demonstrate how to establish fixed kVp for various subject parts.

In fixed kvp technique, the first step involves the separation of the anatomical parts into small, medium, and large categories depending on the range of thickness. A medium-sized phantom is chosen at the start with 80kvp and systematically increase the mAs by twenty (e.g., 40, 60,80) until an appropriate OD is achieved.

11. Describe a variable kilovoltage technique system.

Variable kilovoltage systems are the oldest techniques that were used before the invention of fixed systems. These systems allow a small change in the exposure incrementally to compensate for the variation of the thickness of body parts. They, therefore, produce images of high quality in resolution and contrast, which enhances the visibility of finer details.

12. Discuss the primary advantages and disadvantages of variable kVp technique systems.

Variable kvp techniques allow small changes in kvp while maintaining the mAs and time variables during exposure in an incremental manner depending on the thickness of tissues. This produces images of high quality in contrast and resolution. This allows for more details and finer to be viewed. This technique, however, increases the complexity of imaging and examination.

13. State the 2 kVp rule.

The 2 kvp rule states that in each 1cm of the tissue thickness, the kvp is increased on decreased by 2.

14. Explain why more than a single kilovoltage scale is required with a variable kVp system.

The thickness of the body part being examined determines the kvp with variable mAs used for individual parts. The variability of the single kilovoltage scale is influenced by the differences in the thickness of body parts. The progression values selected might be too low for penetration in different body parts due to density differences.

15. Describe the placement and function of a phototimer and an ionization chamber automatic exposure.

16. Describe how to modify image density, contrast, and time when using automatic exposure control.

The mAs is varied either by increasing or decreasing by a scale value of 25%-30%. An initial amount of radiation is selected and calibrated depending on the energy responses and image quality standards.

17. Explain the effect of collimation of phototimed image quality.

Actively collimating to the volume of interest reduces the overall integral dose to the patient and thus minimizes the radiation risk. Less volume irradiated will result in less x-ray scatter incident on the detector. This results in improved subject contrast and image quality.

18. Provide solutions to minimum response time and back-up time problems.

The use of Automatic Exposure Control can be helpful in is the selection of sensors and kvp in order to generate consistent response time and image quality. The devices produce x-ray beams at an optimal density.

19. Explain how to modify the suggested technical factors on an anatomically programmed control unit.

The kilovoltage, which determines the image quality influences the wavelength of the rays being produced. The sharpness of the image can be improved by inserting the atomic part, which is of interest nearest to the receptor. Plastic inserts can be used in this process that provides accurate projections.

20. Differentiate between AEC and APR.

APR are critical components of X-rays circuits that allow the selection of body parts and reprogramming of exposure factors. AEC are devices that automatically controls exposure by determining the amount of radiation that is received by IR. AEC systems automatically stop radiation as soon as the IR is exposed to the specific amount

21. Discuss methods of reducing patient exposure dose through effective communication.

The patient can be informed of the risks involved with the X-ray imaging process and motivated to consider alternatives. Radiologists equipped with knowledge about x-ray imaging can initiate interactions with patients and explain the damages caused by the ionization of tissues. The exposure to radiation is the primary contributor to changes in the molecular structure of the cell and DNA, which can result in cell death or changes in genetic encoding. This exposes the cell to cancerous mutation,

22. Describe various methods of reducing patient exposure dose through effective positioning

The use of posteroanterior positioning has also been found to reduce exposure dosages in women by 38% and testicular dosage in men by 76% compared to anteroposterior positioning.

Camera positioning can also be used to reduce the amount of x-ray dosage by placing the sensor as close as possible to the interested area. This reduces the additional radiation received by other parts of the body that are not of interest.

23. Evaluate various exposure factors for the most effective methods of reducing patient exposure dose under various clinical conditions.

Modern radiography techniques that make use of non-fluoroscopic systems have been found to reduce the amount of exposure to the lowest possible level.  This technique reduces the number of additional x-rays received by the patient ad body tissues. Adjustment of the frame rate to lower than 3/sec in each frame during imaging procedures regulates the energy in the individual image frames as well as x-ray dosage. This allows for the customization of individual imaging sessions for each patient, depending on the medical examination required. The general advantage of this technique is the reduction in the amount of exposure and ionization of body tissues and cells.

Define Terminology:

AEC- Automatic Exposure Control is an x-ray exposure termination device.

APR- Anatomically programmed radiography is a technique by which graphics on the console guide the technologists in the selection of a desired kVp and mAs.

Optimal kVp- This is the grading score that produces the best quality image at the lowest possible damages to the patient.

Ionization chamber- This is a detector that is filled with gas and measures the charge and exposure when the gas is ionized by photons.

Entrance skin exposure dose- This is the measure of the amount of radiation that is being absorbed by the skin when exposed to the patient.

Falling load generator- This is an automatic device equipped with a microcontroller processor that controls the amount of exposure and ensure the lowest amount possible at a high mAs setting.