RAD Morgan exam 2.docx

RAD 2555

Summer 2024

QC Exam 1.5 Study Review

Quality Control = product or equipment driven;

• QC program is required by TJC. TJC Stamp of approval will allow for Higher quality patient care, accreditation, reimbursement
• Responsibility of all in department = radiologists, radiology managers, radiology supervisors, radiology directors, radiation physicists, quality control technologists, staff radiographers
• Phantoms simulate human tissues and are used to test and ensure the radiographic system's imaging capabilities and consistency. Utilized to evaluate image quality and system performance

Why is QC so important to our field?

• To identify areas needing improvement and reduce unnecessary exposure
  Before we analyze the data or results, we need to know how and why its important to collect data such as monitoring repeat rates to help identify technical or procedural issues, thereby minimizing patient exposure to radiation.
• CQI – Continuous Quality Improvement – ongoing process that never ends w/ QA and QC

Areas or testing for the department - visual inspection, environmental inspection, performance testing

3 Levels of QC and maintenance – routine, full inspection, and system adjustment

Level 1 – Noninvasive, Simple; (techs)

Level 2 – Noninvasive, Complex (could be techs, sometimes a lead tech or supervisor)

Level 3 – Invasive, Complex (physicists)

How often should equipment maintenance and calibration be performed in a radiology department?

Technically: As recommended by the manufacturer and regulatory guidelines. Regular maintenance and calibration schedules depend on specific guidelines to ensure the equipment operates safely and effectively.

AAPM – most annual maintenance is done 1x year at minimum, except for the CR calibration (1% tolerance) and Field Light Congruence/Collimator (2% tolerance of SID)

What is Initial Testing?
Acceptance testing is performed when new equipment is installed to verify it meets all specified performance criteria and ensure equipment meets specifications.

What is AEC purpose?
To ensure consistent image quality by adjusting exposure parameter of time. AEC adjusts exposure settings automatically to maintain optimal image quality, reducing variability in radiographic output. Do you remember what dose creep means?

Why do some tools use of a step wedge?
A step wedge (penetrometer) is used to evaluate the uniformity and exposure consistency across the X-ray field by showing varying densities.

Workstations = radiologists workstations are always more than the radiographer’s

(Many matrix sizes for radiologists workstation are:
2048x2560 – 4096x6144 🡪 which is always more than the x-ray tech’s monitors in the room.

The radiologists that read mammograms will have the highest matrix sizes and best screen resolution. You don’t necessarily need to know that exact number for radiologist’s matrix sizes, but you must know that Radiologists will have better resolution than techs; and Mammo Radiologists monitors have the highest resolution.

Latent image vs Manifest Image

Manifest image – visible image

Latent - invisible image on an unprocessed radiograph formed during exposure of the receptor

Brightness and contrast – can be adjusted for most digital images reducing the need for repeats and allowing optimal patient dose techniques to be utilized.

Brightness = monitor control 🡪 window level =sets midpoint of gray scale, affecting image brightness (increase level makes image appear darker; decreasing level makes image appear lighter)

Contrast = how many grays desired 🡪 window width = range of gray shades (narrow width increases contrast because there is fewer shades; wider width reduces contrast by showing more shades)

Luminance – visible light emitted
Florence – visible light only emitted while x-ray beam is on

Histograms

When we have more radiation scattered, what happens to the histogram? = Widens the histogram (more grays, more data to collect)

There will be poor Histogram Analysis when there is poor collimation leads to this error in CR and DR image processing or when part is not centered in the light field, or if light field is outside IR/plate

Helpful Summary – Table Form

Summarized QA Tests and Tools:

Quality Control Goals:

• Reduce patient exposure to radiation while maintaining optimal image quality.
• Ensure consistent and reliable radiographic procedures through regular testing and maintenance.

Quality Control Tests and Tools:

• Kilovoltage (kVp) Accuracy: Use a kVp meter; tolerance is ±5% of the set value.
• Focal Spot Size: Evaluate using a star pattern test to ensure image sharpness; 50% tolerance
• Half-Value Layer (HVL) Test: Determines beam filtration and ensures adequate patient protection.
  • Filtration – must be 2.5 ml/Al Eq
    Half-Value Layer (HVL) = the thickness of a specified material (usually aluminum for X-ray beams) that reduces the X-ray beam intensity by half. It's a measure of the beam's penetration and the effectiveness of the filtration.

Al Z# = 13

• • Understand the relationship:
  • The HVL is the thickness at which the beam intensity is reduced by half.
    • 2.5 ml/Al Eq is required in all total filtration of the x-ray tube and machine.
  • 0.5 mm comes from the inherent filtration (glass envelope/housing and oils)
  • 2.0 mm must come from added filtration (placed in the pathway of the beam before it enters the patient)
• Collimation Accuracy: Light field and x-ray beam alignment should be within 2% of the Source-to-Image Distance (SID).
• CR Accuracy: central ray must be within 1% +/-

Quality Control Frequencies:

• Digital Radiography Systems: Should be followed to manufacturers specifications (Some manufacturers even ask for Monthly QC tests to ensure optimal performance); often annually at minimum (except for Collimator/Light Field Accuracy/Congruency and CR accuracy which should be semi-annually)
• Lead Apron Inspection: Regular checks for cracks/holes using fluoroy; minimum yearly

Radiation Protection and Safety:

• Regularly inspect lead aprons to detect cracks or holes that could compromise protection; annual requirement minimum
• Monitor exposure reproducibility (+/- 5%) and linearity (+/- 10%)
  

Common Causes of Repeat Exposures:

• Incorrect patient positioning and improper exposure settings can increase repeat rates.
• Effective communication and proper technique reduce the need for repeat images.

Diagnosis Quality Assurance Methods with Patient Summaries:

Quality Control Math Examples

1. Light Field and Radiation Field Alignment = The light field and radiation field must align within 2% of the SID

Examples:
Problem 1: If the SID is 100 cm, determine the maximum allowable misalignment.

1. Determine the allowable misalignment percentage:
   • Allowable misalignment is 2% of SID.
2. Calculate the allowable misalignment:
   • SID = 100 cm
   • Allowable misalignment = 2% of 100 cm
     Allowable misalignment=2/100×100 cm = 2 cm
     

Problem 2: During a QA test, the observed misalignment between the light field and the radiation field is measured as 1.5 cm at an SID of 120 cm. Determine whether this misalignment is within acceptable limits.

1. Determine the allowable misalignment percentage:
   • Allowable misalignment is 2% of SID.
2. Calculate the allowable misalignment:
   • SID = 120 cm
   • Allowable misalignment = 2% of 120 cm

Allowable misalignment=2/100×120 cm=2.4 cm
3. Compare the observed misalignment with the allowable misalignment:

• • Observed misalignment = 1.5 cm
  • Allowable misalignment = 2.4 cm

Answer: The observed misalignment of 1.5 cm is within the allowable limit of 2.4

Problem 3: If the observed misalignment is 1.8 cm and the alignment tolerance is 2% of the SID, determine the SID.

1. Determine the allowable misalignment percentage:
   • Allowable misalignment is 2% of SID.
2. Set up the equation:
   • Allowable misalignment = 2% of SID

1.8 cm=0.02×SID

Solve for SID = SID=1.8 cm/0.02 = 90 cm

The SID is 90 cm

QA in CR imaging – we have learned this already; but think of these aspects now in QA mindset

• How often should CR caseates be erased? = daily
• Moire or Aliasing – grid lines are parallel to the direction of laser beam travel in a CR reader
• Phantom Imaging or Ghosting – erasure lamp is not working properly in PSP imagine, there is a fogged or appears to be another image on the cassette
• Line Artifact – dust in the path of the laser beam in the CR reader
  • Scratches, dust, or dirt on the PSP plate will appear white on the image

Artifacts = marks, spurious objects, motion, or unwanted optical density on the image that do not represent the anatomic structure
Errors/ Image Production mishaps: These are different kinds of artifacts which could be processing or exposure

• Processing artifacts – image artifact produced during the processing or acquiring of image: could be because of histogram analysis error or bad DELs
• Exposure artifacts could be foreign object, double exposure, grid cut off, patient motion, wrong IR selection

Controlling the factors below, radiographers can produce high-quality images. (How to get the best quality image)

Kilovoltage Peak (kVp):
The kVp determines the energy of the X-rays produced and influences the contrast and penetration of the X-ray beam. Higher kVp results in lower contrast but greater penetration, while lower kVp provides higher contrast and less penetration.

Milliamperage (mA) and Exposure Time (mAs):
The product of mA and exposure time (mAs) affects the quantity of X-rays produced, which impacts the image's density and noise. Higher mAs increases image exposure and reduces noise, but also increases radiation dose.

Object-to-Image Distance (OID):
OID is the distance between the object being imaged and the image receptor. A shorter OID reduces magnification and distortion, improving image sharpness.

Source-to-Image Distance (SID):
SID is the distance between the X-ray source and the image receptor. A longer SID decreases magnification and distortion, enhancing image resolution and sharpness.

Focal Spot Size:
The size of the focal spot affects the sharpness of the image. A smaller focal spot produces sharper images with better spatial resolution, while a larger focal spot may cause blurring.

Digital Detector Characteristics (for digital systems):
The resolution, pixel size, and dynamic range of digital detectors influence image quality. Higher resolution and smaller pixels provide better detail, while a wider dynamic range improves contrast.

Collimation:
Collimation restricts the size and shape of the X-ray beam to the area of interest, reducing scatter radiation and improving image contrast.

Reduce Patient Motion:
Motion during exposure can cause blurring and reduce image sharpness. Minimizing patient movement and using appropriate exposure times help maintain image clarity.

Consider how to Control Scatter Radiation:
Scatter radiation reduces image contrast and detail. Using grids, air gaps, and appropriate collimation reduces scatter and enhances image quality.

Image Processing (for digital systems):
Image processing algorithms adjust contrast, brightness, and noise levels to optimize image quality. Proper processing ensures accurate representation of anatomical structures.

Image contrast in radiography is the difference in optical density between different areas of an image. Factors that affect contrast, along with explanations for each.

Quality factors listed above go hand and hand with image contrast:

1. Kilovoltage Peak (kVp):
   kVp controls the energy of the X-ray beam. Lower kVp results in higher contrast because it produces a beam with lower penetration and more absorption differences between tissues. Higher kVp increases penetration and scatter, reducing contrast by creating a more uniform exposure across the image.
2. Scatter Radiation:
   Scatter radiation decreases image contrast by adding unwanted exposure to the image receptor, creating a foggy appearance. Techniques to reduce scatter, such as using grids, collimation, and appropriate kVp, help maintain higher contrast.
3. Beam Filtration:
   Beam filtration removes low-energy X-rays that contribute to scatter. While filtration is necessary for patient safety, excessive filtration can reduce contrast by increasing the proportion of higher-energy X-rays, which penetrate tissues more uniformly.
4. Patient Size and Tissue Composition:
   Larger patients or those with denser tissues produce more scatter, reducing contrast. Differences in tissue composition, such as bone versus soft tissue, affect contrast. Thicker or denser areas absorb more X-rays, enhancing contrast, whereas areas with similar composition reduce contrast.
5. Grid Use:
   Grids absorb scatter radiation before it reaches the image receptor, enhancing contrast. By selectively allowing primary radiation to pass, grids improve the visibility of details by reducing fogging and increasing contrast.
6. Collimation:
   Collimation reduces the size of the X-ray field, minimizing scatter radiation and improving contrast. By focusing the beam on the area of interest, collimation enhances the difference between light and dark areas of the image.
7. Image Processing (for digital systems):
   Digital image processing techniques can adjust contrast by modifying the brightness and contrast settings. Algorithms can enhance the visibility of specific structures, though excessive manipulation may alter diagnostic information.

Spatial resolution, or recorded detail, in radiography refers to the ability of an imaging system to distinguish small structures and detail in an image. Several factors directly influence spatial resolution, and understanding these can help optimize image quality.

Which of the following tests is most commonly used to evaluate the resolution of a radiographic system? **Spatial Resolution**
Line pair test - The line pair test is used to assess the spatial resolution of a radiographic system by measuring its ability to distinguish between closely spaced lines.

Factors that affect spatial resolution:

1. Focal Spot Size:
   A smaller focal spot size produces sharper images with better spatial resolution because it minimizes the penumbra (blur) around the edges of structures. Larger focal spots increase the penumbra and reduce image sharpness.
2. Source-to-Image Distance (SID):
   Increasing the SID reduces magnification and distortion, which enhances spatial resolution. A longer SID results in a more parallel X-ray beam, improving image clarity and reducing geometric unsharpness.
3. Object-to-Image Distance (OID):
   Reducing the OID decreases magnification and distortion, thereby improving spatial resolution. A shorter OID minimizes geometric unsharpness, resulting in sharper images.
4. Motion:
   Any motion of the patient or imaging equipment during exposure can cause blurring, which decreases spatial resolution. Immobilization techniques and shorter exposure times help minimize motion artifacts.
5. Detector/Film Resolution:
   The resolution capability of the detector or film-screen system determines the level of detail that can be recorded. Higher-resolution detectors or slower film-screen systems capture finer details, enhancing spatial resolution.
6. Matrix Size and Pixel Size (for digital systems):
   A larger matrix size and smaller pixel size provide greater spatial resolution because more pixels are available to represent small details in the image. This allows for more precise depiction of structures.
7. Collimation:
   Proper collimation reduces the amount of scattered radiation reaching the image receptor, which can blur the image and reduce spatial resolution. Limiting the beam to the area of interest enhances image detail.
8. Grid Use:
   Grids reduce the amount of scatter radiation reaching the image receptor, improving contrast and enhancing spatial resolution. This is particularly important for thicker body parts where scatter is more prevalent.

Image receptor exposure in radiography = amount of radiation reaching the image receptor (film or digital detector). Factors directly influence image receptor exposure:

1. Milliamperage (mA) and Exposure Time (mAs):
   The product of mA and exposure time (mAs) directly determines the quantity of X-rays produced. Increasing mAs increases the amount of radiation reaching the receptor, which increasing exposure. Decreasing mAs reduces exposure.

When using AEC, consider = Dose creep – progressive increase in dose to patients as technologists rely on automatic rescaling to compensate for overexposure

1. Kilovoltage Peak (kVp):
   kVp affects both the energy and the quantity of the X-ray beam. Higher kVp increases the penetrating power of the X-rays, allowing more radiation to reach the image receptor, increasing exposure. Higher kVp can produce more scatter, affecting the exposure.
2. Source-to-Image Distance (SID):
   As SID increases, the intensity of the X-ray beam reaching the image receptor decreases due to the inverse square law. This results in lower image receptor exposure. Decreasing the SID increases the beam intensity and exposure.
3. Object-to-Image Distance (OID):
   While OID primarily affects magnification and spatial resolution, increasing the OID can also result in less radiation reaching the image receptor bc increased scatter radiation absorption (thereby reducing exposure)
4. Beam Filtration:
   Beam filtration removes low-energy X-rays from the beam, reducing patient dose and altering the beam quality. Increased filtration reduces the overall exposure to the image receptor, while decreased filtration increases it.
5. Collimation:
   Collimation reduces the size of the X-ray field, decreasing the amount of scatter radiation and exposure to the image receptor. Proper collimation focuses the beam on the area of interest, improving image quality.
6. Patient Size and Tissue Composition:
   Larger or denser patients absorb more X-rays, reducing the amount of radiation reaching the image receptor. Adjustments in exposure factors, such as increasing mAs or kVp, may be necessary to compensate for this attenuation.
7. Grid Use:
   Grids are used to reduce scatter radiation and improve image contrast. However, grids also absorb some of the primary radiation, requiring an increase in mAs to maintain appropriate image receptor exposure.
8. Field Size:
   Larger field sizes allow more scatter radiation to reach the image receptor, increasing exposure. Reducing field size through collimation decreases scatter and exposure.

Filtration in radiography = to improve the quality of the X-ray beam by selectively removing low-energy X-ray photons.

1. Reduction of Patient Dose:
   Low-energy X-rays are not penetrating enough to contribute to image formation and are more likely to be absorbed by the patient's tissues. This absorption increases the patient's radiation dose without improving image quality. By filtering out these low-energy photons, the overall radiation dose to the patient is reduced
2. Improvement of Beam Quality:
   Filtration increases the average energy of the X-ray beam, often referred to as "hardening" the beam. A higher-energy beam is more penetrating and can produce clearer images, especially in thicker body parts, by reducing the differential absorption that can cause excessive image contrast or noise.
3. Reduction of Scatter Radiation:
   Although filtration primarily affects the primary beam, it indirectly reduces scatter by eliminating photons that are more likely to be scattered. This reduction in scatter enhances image contrast, making the image clearer and more diagnostically useful.
4. Compliance with Regulatory Standards:
   Many regulatory bodies mandate a minimum level of filtration for X-ray machines to ensure patient safety and consistent image quality. This is typically measured in terms of aluminum equivalence (e.g., 2.5 mm Al for diagnostic radiography).

Filtration in X-ray machines is typically achieved using materials like aluminum or copper, which are placed in the path of the X-ray beam. The amount and type of filtration can vary based on the type of examination and the specific requirements of the imaging system. Optimizing filtration, radiographers can ensure effective patient protection while maintaining high-quality diagnostic images.

When conducting an annual filtration quality assurance (QA) check for the half-value layer (HVL) in radiography, encountering an HVL measurement of less than 2.5 mm Al/Eq indicates that the X-ray beam is not adequately filtered.

1. Inadequate, Incorrect, or Damaged Filters:
   • Problem to consider: The total filtration, including both inherent (from the X-ray tube housing and materials) and added filtration, may be insufficient. Filters may be improperly installed, damaged, or made of incorrect materials, leading to insufficient filtration.
     1. Inspect filters for damage, ensure proper installation, and confirm they are made from appropriate materials like aluminum or copper. (physics)
     2. Verify that the correct amount of added filtration is present. This may involve checking and possibly replacing or adding aluminum filters. (physics)
2. Aging of X-ray Tube:
   • Problem to consider: Over time, the X-ray tube and its components may degrade, affecting the filtration properties.
     1. Inspect the X-ray tube and replace aging components as needed. Regular maintenance can help ensure consistent beam quality. (physics)
3. Equipment Calibration Issues:
   • Problem to consider: Calibration errors in the measurement equipment can lead to inaccurate HVL readings.
     1. Calibrate the measurement equipment before conducting HVL tests and ensure it is functioning correctly. (physics)
4. Human Error:
   • Problem: Mistakes in measurement procedures, such as incorrect placement of filters or measurement devices, can lead to inaccurate readings.
     1. Follow standardized procedures and double-check all setups before taking measurements to minimize errors. (physics)
5. Inherent Filtration Reduction:
   • Problem: Inherent filtration may be reduced due to changes in the tube housing or materials used in the X-ray unit.
     1. Check the X-ray tube housing for any changes or degradation that could affect inherent filtration. (physics)
6. Beam Quality Changes:
   • Problem: Changes in the beam quality due to power supply issues or variations in tube voltage can affect HVL measurements.
     1. Ensure the X-ray machine is operating at the correct voltage and is receiving stable power. Check the machine’s settings and recalibrate if necessary. (physics)

Focal Spot
The focal spot is the area on the anode target in the X-ray tube where the electron beam is focused and X-rays are produced. It is a critical component in determining image resolution and clarity. The focal spot size affects the sharpness and detail of the X-ray image:

• Small Focal Spot: Produces sharper images with better spatial resolution, as it minimizes the penumbra (blurring at the edges of structures). However, smaller focal spots have a limited capacity to dissipate heat, which can restrict the amount of current (mA) that can be used during imaging.
• Large Focal Spot: Allows for higher mA settings, which is useful for imaging larger body parts or for techniques requiring longer exposure times. However, it can result in reduced image sharpness due to increased penumbra.

Line Focus Principle
The line focus principle is a design feature of X-ray tubes that optimizes the effective focal spot size to improve image quality while managing heat dissipation. It involves angling the anode target to create a smaller effective focal spot while maintaining a larger actual focal spot for heat distribution.

• Actual Focal Spot: The physical area on the anode where electrons impact. It is larger to help spread out the heat generated during X-ray production.
• Effective Focal Spot: The size of the focal spot as seen from the perspective of the X-ray image receptor. It is smaller than the actual focal spot due to the angling of the anode target.

Benefits of the Line Focus Principle:

1. Improved Image Sharpness: By creating a smaller effective focal spot, the line focus principle enhances image sharpness and spatial resolution without compromising the tube's ability to handle heat.
2. Heat Management: The larger actual focal spot allows for better heat distribution, reducing the risk of damage to the anode and extending the life of the X-ray tube.

A quality assurance (QA) check revealing that the focal spot size is greater than 50% larger than its specified size indicates potential issues with the X-ray tube or its operation.