Medical Imaging: X-ray Fundamentals

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Questions and Answers

The fixed spatial resolution characteristic of direct digital systems is determined by the [blank] and [blank] size.

TFT, DEL (correct)

Sensing area, DEL

Pixel pitch, DEL

CCD, DEL

Which of the following control the subject contrast of the exit / remnant x - ray signal in digital imaging? (Select all that apply)

Photon energy (correct)

Kilovoltage (correct)

Rescaling

Windowing

Lookup table

Which of the following pathologic conditions probably will require a decrease in exposure factors?

Osteosclerosis

Osteochondritis

Osteomyelitis

Osteoporosis (correct)

An algorithm, as used in x - ray imaging, is / are [blank].

a series of variable instructions Signup and view all the answers

The chest radiograph shown in Figure 4-1 demonstrates a [blank] artifact.

Aliasing artifact Signup and view all the answers

The components of a detector element (DEL) include which three of the following? (Select all that apply)

Capacitor Signup and view all the answers

Geometric sharpness is inversely influenced by [blank].

OID Signup and view all the answers

The part of a detector element (DEL) that stores electrical charges is the [blank].

capacitor Signup and view all the answers

The radiograph shown in Figure 4-2 demonstrates an example of a [blank] artifact.

exposure artifact Signup and view all the answers

An increase in kilovoltage will have which of the following effects on the remnant beam / signal? (Select all that apply)

Increased production of scattered radiation Signup and view all the answers

Factors that can impact image spatial resolution / image sharpness include (Select all that apply)

Focal spot size Signup and view all the answers

The x - ray image seen in Figure 4-3 is most likely the result of [blank].

insufficient mAs factors Signup and view all the answers

The function of the backup timer in automatic exposure control devices is to (Select all that apply)

Prevent patient overexposure Signup and view all the answers

Which of the following groups of exposure factors will produce the greatest receptor exposure?

400 mA , 70 ms Signup and view all the answers

Which of the following is / are directly related to photon energy?

Wavelength Signup and view all the answers

An x - ray image of the ankle was made at 40 - inch SID , 200 mA , 50 ms , 70 kV , 0.6 - mm focal spot , and minimal OID. Which of the following modifications would result in the greatest increase in magnification?

4 - inch OID Signup and view all the answers

Grid cutoff due to off - centering would result in [blank].

overall loss of receptor exposure Signup and view all the answers

The postprocessing function that removes high frequency noise from the x - ray image is [blank].

smoothing Signup and view all the answers

An exposure of 500 mA and 70 kV has been selected for an AP projection of the abdomen using AEC. If 90 ms has been selected for the backup time , and the minimum response time is 25 ms , the milliampere seconds exposure will be at least [blank] mAs.

12.5 Signup and view all the answers

The lateral coccyx image shown in Figure 4-4 was made using AEC but is overexposed. This is most likely a result of [blank].

incorrect centering of the part Signup and view all the answers

Which of the following units is / are used to express resolution?

Line pairs per millimeter Signup and view all the answers

If an IR exposed using a 12 : 1 ratio grid exhibits loss of signal at its lateral edges , it is probably because the [blank].

SID was too great Signup and view all the answers

Foreshortening can be caused by [blank].

the radiographic object being placed at an angle to the IR Signup and view all the answers

Acceptable method ( s ) of minimizing motion unsharpness is / are (Select all that apply)

patient instruction Signup and view all the answers

Using fixed milliampere seconds and variable kilovoltage technical factors , each centimeter increase in patient thickness requires what adjustment in kilovoltage?

Increase 2 kV Signup and view all the answers

In which of the following systems does the radiographer select the anatomic part from the console menu?

APR Signup and view all the answers

Which of the following statements is / are true regarding the location of the artifact seen in the erect PA chest shown in Figure 4-5?

The object is located within the IP Signup and view all the answers

Which of the following can impact the remnant signal? (Select all that apply)

Pathology Signup and view all the answers

X - ray photon energy is inversely related to [blank].

Photon wavelength Signup and view all the answers

The PA chest image shown in Figure 4-6 exhibits which of the following qualities? (Select all that apply)

Adequate inspiration Signup and view all the answers

The device that functions to terminate the x - ray exposure following ionization of a particular quantity of an air is the [blank].

AEC Signup and view all the answers

Compared with a low - ratio grid , a high - ratio grid will (Select all that apply)

Absorb more primary radiation Signup and view all the answers

A decrease in kilovoltage will result in (Select all that apply)

A decrease in receptor exposure Signup and view all the answers

Select the true statement ( s ) regarding Figure 4-7 (Select all that apply)

The airway is adequately demonstrated Signup and view all the answers

The primary function of x - ray beam filtration is to [blank].

reduce patient skin dose Signup and view all the answers

The exposure factors of 400 mA , 70 ms , and 78 kV were used to produce a particular image receptor exposure. A similar image could be produced using 500 mA , 90 kV , and [blank] ms.

28 Signup and view all the answers

An exposure was made at a 36 - inch SID using 300 mA , a 30 - ms exposure , and 80 kV and an 8 : 1 grid. It is desired to repeat the radiograph using a 40 - inch SID and 70 kV. With all other factors remaining constant , what new exposure time will be required?

0.07 Signup and view all the answers

The part of a detector element ( DEL ) that functions as a switch / gate to release charges for readout is the [blank].

TFT Signup and view all the answers

An exposure was made using 300 mA , 40 ms exposure , and 85 kV. Each of the following changes will decrease the receptor exposure by one - half , except a change to [blank] mAs.

10 Signup and view all the answers

Which of the following groups of digital technical factors would be most appropriate for the radiographic examination shown in Figure 4-8?

300 mA , 20 ms , 84 kV Signup and view all the answers

All of the following affect the exposure rate of the primary beam , except

Field size Signup and view all the answers

Which of the following has the greatest effect on radiographic IR exposure?

SID Signup and view all the answers

Subject contrast is related to (Select all that apply)

Atomic number of tissue being traversed Signup and view all the answers

What grid ratio is represented in Figure 4-9?

10 : 1 Signup and view all the answers

A 5 - inch object to be radiographed at a 44 - inch SID lies 6 inches from the IR. What will be the image width?

5.7 inches Signup and view all the answers

An image demonstrating many brightness levels , or shades of gray , with only slight difference between the levels / shades is said to possess (Select all that apply)

Long - scale contrast Signup and view all the answers

The term pixel is associated with all of the following , except

How much of the part is included in the matrix Signup and view all the answers

Spatial resolution / detail sharpness can be improved by decreasing (Select all that apply)

The OID Signup and view all the answers

Which of the following devices is used to overcome severe variation in patient anatomy or tissue density, providing more uniform receptor exposure?

Compensating filter Signup and view all the answers

The tiny increased brightness , dropout artifacts , seen in the proximal portion of the CR image of the radius shown in Figure 4-10 are representative of [blank].

dust / dirt on the PSP Signup and view all the answers

Radiographic images , for medicolegal reasons , are required to include the following information:(Select all that apply)

The patient's name and / or identification number Signup and view all the answers

Special considerations / conditions that often require increase from typical technical factors include (Select all that apply)

Excessive BMI Signup and view all the answers

The distance between the center of one pixel and the center of an adjacent pixel is termed [blank].

pixel pitch Signup and view all the answers

Because of the anode heel effect , the intensity of the x - ray beam is greatest at the [blank] of the beam.

cathode end of the beam Signup and view all the answers

The differences between CR and DR include (Select all that apply)

CR uses IPs Signup and view all the answers

Which two of the following are associated with the term " voxel "?

Measure in Z direction Signup and view all the answers

Using a 48 - inch SID , how much OID must be introduced to magnify an object 2 times?

24 - inch OID Signup and view all the answers

A particular radiograph was produced using 12 mAs and 85 kV with a 16 : 1 ratio grid. The radiograph is to be repeated using an 8 : 1 ratio grid. What should be the new milliampere seconds value?

8 Signup and view all the answers

Pathologic or abnormal conditions that would require a decrease in exposure factors include all of the following , except

Pneumonia Signup and view all the answers

Analog - to - digital conversion is required in which of the following imaging system?

CR Signup and view all the answers

The photostimulable phosphor ( PSP ) plates used in CR are constructed in layers that include (Select all that apply)

Support layer Signup and view all the answers

For the same field of view ( FOV ) , spatial resolution will be improved using [blank].

a larger matrix Signup and view all the answers

Which of the following are methods of limiting the production of scattered radiation? (Select all that apply)

Restricting the field size to the smallest practical size Signup and view all the answers

The PA erect chest images seen in Figure 4-11 were made of the same patient within 24 h. Which of the following statements are true regarding the images? (Select all that apply)

Figure 4-11A was performed at 6 feet , whereas Figure 4-11B was performed at much shorter SID Signup and view all the answers

Study Notes

Image Acquisition and Technical Evaluation

TFT and DEL size: Determine the fixed spatial resolution of direct digital imaging systems.
Subject Contrast Control: Kilovoltage, photon energy, and windowing control the contrast of the exit/remnant x-ray signal.
Decreased Exposure Factors: Osteoporosis requires a decrease in exposure factors.
Algorithms in X-ray Imaging: Algorithms are a series of variable instructions.
Aliasing Artifact: The chest radiograph of Figure 4-1 demonstrates this artifact.
Detector Element (DEL) Components: The sensing area, TFT, and capacitor are DEL components.
Geometric Sharpness and Distance: Object Image Distance (OID) inversely affects geometric sharpness. Source-to-Image Receptor Distance (SID) is directly related to sharpness.
DEL Capacitor Function: The capacitor stores electrical charges.
Exposure Artifact: Figure 4-2 displays an exposure artifact.
Kilovoltage Effect on Remnant Beam: Increasing kilovoltage increases scattered radiation and exposure rate, but decreases contrast.
Image Spatial Resolution Factors: Patient factors, focal spot size, and SID impact image sharpness.
Insufficient mAs Factors: Figure 4-3 displays a low mAs factor.
Backup Timer Function: The backup timer in AEC prevents overexposure and tube overheating.
Maximum Receptor Exposure: 400 mA, 70 ms, and 78 kV exposure factors yield maximum receptor exposure.
Photon Energy and Kilovoltage: Kilovoltage is directly related to photon energy.
Greatest Magnification Increase: A 4-inch OID results in the greatest magnification increase.
Grid Cutoff: Off-centering results in an overall loss of receptor exposure in a grid image.
Postprocessing Smoothing: Smoothing removes high-frequency noise.
AEC Minimum Exposure: The minimum milliseconds in AEC is 25 ms, so 500 mA at 70 kV would mean at least 12.5 mAs to work.
Overexposed AEC Image: Incorrect centering of the part leads to an overexposed AEC image (Figure 4-4).
Resolution Units: Line-spread function and line pairs per millimeter express image resolution.
Grid Signal Loss: Lateral signal loss is caused by too-great of a SID.
Foreshortening Cause: The angled position of the object in relation to the IR causes foreshortening.
Motion Unsharpness Minimization: Suspended respiration, short exposure times, and patient instructions reduce motion blur.
Kilovoltage Adjustment for Patient Thickness: A 1 cm increase in patient thickness requires increasing kV by 2 kV.
Anatomic Part Selection: The radiographer selects the anatomic part in the APR system.
Artifact Location: The artifact in the Figure 4-5 PA chest image is within the patient.
Remnant Signal Factors: Tissue density, pathology, and beam restriction impact the remnant signal.
Photon Energy and Wavelength Relation: Photon energy and wavelength are inversely related.
PA Chest Image Qualities: Adequate penetration, long-scale contrast, and adequate inspiration (Figure 4-6).
Automatic Exposure Control (AEC): AEC terminates exposure based on air ionization.
High-Ratio Grid vs. Low-Ratio Grid: High-ratio grids absorb more scattered radiation, and less centering latitude. (low ratio grids are better for smaller parts.)
Decreased Kilovoltage Effects: Decreased kilovoltage results in decreased photon energy and receptor exposure but also decreased sharpness.
Figure 4-7 Image Analysis: Insufficient receptor exposure is noted for adequate vertebrae visualization.
X-ray Beam Filtration Purpose: Reducing the patient skin dose is the purpose of x-ray beam filtration.
Similar Receptor Exposure with Different mA and ms: Exposure factors of 500 mA , 8 ms, and 90 kV (similar to that example in the question) require 28 ms as the new exposure time.
TFT Function: The TFT acts as a switch/gate for charge release.
mAs Decrease in Imaging: Changes in mA or ms (but not kV) will change the image receptor exposure by half.
Technical Factors for Figure 4-8: Image examination requires a 300 mA, 20 ms, 84 kV image.
Exposure Rate Factors: Milliamperage, kilovoltage, and distance, but not field size, affect primary beam exposure rate.
Greatest Effect on IR Exposure: SID has the greatest effect on IR exposure.
Subject Contrast Factors: Differential tissue absorption and atomic numbers of tissues affect subject contrast.
Grid Ratio: Figure 4-9 shows a 10 : 1 grid ratio.
Image Width Calculation: The image width is 5.7 inches.
Long Scale Contrast Characteristics: A large dynamic range with minimal differences between brightness levels is long-scale contrast.
Pixel Term Exclusion: The pixel term is not associated with the amount of part encompassed in the matrix.
Spatial Resolution Improvement: Decreasing OID and minimizing motion improve spatial resolution/detail sharpness.
Compensating Filter Use: Compensating filters overcome variations in patient anatomy providing a uniform image.
CR Image Artifacts: Dust or dirt on the PSP causes increased brightness artifacts.
Required Image Information: Patient name/ID and a left/right marker are required for images.
Conditions Requiring Increased Factors: Excessive BMI and skeletal sclerosis.
Pixel Pitch Definition: The distance between the center of one pixel and the neighboring center is termed pixel pitch.
Anodic Heel Effect: The intensity of x-ray beam is greatest at the cathode end for the heel effect.
CR vs. DR Differences: CR utilizes IPs, and images are not displayed immediately.
Voxel Association: Volume element and Z-direction measurements are associated with voxel.
Magnification with OID: A 24 - inch OID is needed to provide a double magnification image from a 48-inch SID.
Grid Ratio and mAs: Using an 8 : 1 instead of a 16 : 1 grid requires an increased mAs by a factor of 2.
Decreased Exposure Circumstances: Emphysema, not osteoporosis, requires a decreased exposure.
Analog-to-Digital Conversion System: CR (Computed Radiography) requires analog-to-digital conversion.
PSP Plate Layers: Light shield, support, and electroconductive layers constitute a PSP plate.
Larger Matrix Improvement: A larger matrix yields better spatial resolution for the same field of view.
Limiting Scatter Radiation Production: Restricting the field size and using a high-ratio grid limits the production of scattered radiation.
Figure 4-11 Image Analysis: Figure 4-11B demonstrates both magnification of the heart shadow and insufficient inspiration.
mAs Adjustment for Grid: A 12 : 1 grid requires a 15 mAs increase.
Smallest Matrix Image: Image 1 in Figure 4-12 has the smallest matrix size.
Shape Distortions: Elongation and foreshortening are types of shape distortion.
Matrix Size Influence: An increased matrix size increases resolution and reduces pixel size, for equivalent FOV.
Milliamperage for mAs: A 0.05 s duration requires 600 mA to produce 30 mAs.
SID's Impact on Sharpness: SID is directly related to sharpness/detail, not inversely.
mAs Adjustment for Different SID and Grid: Maintaining the same receptor exposure, an increase in SID (from 36 inches to 42 inches) and a reduced grid ratio (from 12 to 5) requires a 6.5 mAs increase, to compensate.
Maximum Receptor Exposure Factors: 200 mA, 60 ms, and a 36-inch SID result in maximum receptor exposure.
Image Resolution Enhancement Factors: Decreasing DEL size and increasing fill factor enhance image resolution.
Digital Imaging and Brightness: Window level adjustments, but not IR exposure, are associated with image brightness in digital imaging.
Kilovoltage Effect on Digital Imaging: Kilovoltage affects photon energy and image penetration, impacting contrast.
Image Consistency: Linearity ensures consistent exposure at adjacent mA stations.
mAs for Double Receptor Exposure: Doubling mAs from 2 to 4 yields a doubled receptor exposure in this scenario.
Spatial Resolution Factors: Factors affecting image sharpness include focal spot size, subject motion, and source-to-object distance (SOD).
Grid Use Considerations: Large or dense objects and higher kilovoltage often require grids for better image quality and lower patient dose.
Figure 4-13 Error Identification: Incorrect centering of the x-ray tube relative to the grid (not the patient or collimator) leads to the shown error.
mAs and Patient Dose Relationship: mAs and patient dose are directly proportional.
Image Plate Front Material: Carbon fiber and magnesium are acceptable materials for image plate fronts.
Exposure Factor Adjustments for Pathology: Emphysema necessitates lower exposure factors compared to other pathologies.
Pixel Size from Matrix and FOV: A 512 X 512 matrix with a 20 cm FOV indicates 0.40 mm pixel size.
Exposure Time Reduction: Using higher mA and kV values reduces required exposure time.
Kilovoltage Inconsistencies: Kilovoltage is directly proportional, not inversely proportional, to wavelength.
Spatial Resolution in CR Imaging Factors: Pixel pitch and sampling frequency influence spatial resolution in CR.
Figure 4-14 Analysis: Line A, from CR, exhibits a greater dynamic range than Line B, from film.
Exposure Artifacts: Double exposure and motion, but not image fading, are exposure artifacts (these are separate concepts from resolution or contrast, or other imaging image display attributes).
Kilovoltage and Exposure Rate: Increased kilovoltage increases exposure rate .
Foreshortening Cause: Improper part alignment leads to foreshortening.
Image Distortion Causes: Misalignment in the tube-part-IR relationship produces shape distortion.
Reduction of Magnification Distortion: Increasing the SID minimizes magnification.
Grid and mAs Relationship: Use increased mAs with an 8:1 grid (versus no grid), to maintain the same receptor exposure. (the specific mAs has been provided in the context).
Reduced Receptor Exposure in Figure 4-15 Image: Image A in Figure 4-15 likely required less exposure to achieve the same image quality.
Factors Affecting Exposure Rate and SID: An increase in SID decreases exposure rate, and a decrease in SID would increase exposure rate.
Matrix Size and Pixel Size: An increase in matrix size results in smaller pixel size, which is associated with increased resolution.
Distortion Causes: Tube angle, part position, and positioning methods cause image distortion.
SID Increase to Overcome Magnification: Increasing SID by 42 inches alleviates magnification issues with a 6-inch OID.
Field Size and Scatter: Reducing field size decreases the amount of scatter.

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Description

This quiz covers essential concepts in medical imaging, focusing on x-ray technology. Topics include detector elements, image resolution, exposure factors, and artifacts. Gain a deeper understanding of how these elements impact the quality of radiographic images.