image production - Image Acquisition & Evaluation (Pt 1)

What factors affect Receptor Exposure?

• mAs & kVp

• OID & SID

• Patient

• Grids

• Filtration & Beam Restriction

• Anode Heel

mAs has a _______ relationship with Receptor Exposure

Directly proportional

kVp has ____ with Receptor Exposure

Exponential Relationship

A 15% increase in kVp is equivalent to _____

Doubling the mAs

OID and SID have and ______ relationship with Receptor Exposure

Inverse Relationship

As OID increases, Receptor Exposure ______

Decreases, as scatter misses IR

As SID increases, receptor exposure ______

Decreases, due to inverse square law

What is the inverse square law formula?

Intensity1/Intensity2 = Distance2^2/Distance1^2

The use of a Grid ________ Receptor Exposure

Decreases, as scatter is absorbed

The use of Filtration ________ Receptor Exposure

Decreases, as low-energy X-rays are removed

Collimating a smaller Field Size _____ Receptor Exposure

Decreases, as the intensity of the Primary beam decreases

As the anode angle increases the Heel effect ____ and Receptor Exposure _____

Decreases and Decreases, as the focal spot size decreases, the created field size is reduced

Factors that affect Contrast have a influence on ____

Scatter

What factors affect Contrast?

• kVp
• Patient
• OID
• Grids
• Filtration & Beam Restriction

As kVp increases, Contrast ______

Decreases, as beam is more penetrative

As Patient Density & thickness vary, Contrast ________

Increase, due to differential absorption/attenuation

What is Differential Absorption/Attenuation

The difference between x-ray photons that are absorbed and those that penetrate the body, collectively they generate subject contrast

As OID Increases, Contrast _______

Increases, as noise is reduced

What is the Air gap technique?

A method to reduce scatter reaching the detector, reducing noise and improving image contrast

The use of a Grid and increased grid ratio, Contrast ______

Increases, as noise is reduced

The use of Filtration ________ Contrast

Decreases, as the overall beam energy is uniform

Collimating to a smaller Field Size _____ Contrast

Increases, as there are fewer matter interactions to create scatter

Factors that affect Recorded Detail / Spatial Resolution have a influence on ______

Penumbra

What is penumbra?

geometric unsharpness around the periphery of the image

What are the Factors that affect Recorded Detail / Spatial Resolution?

• Patient
• OID & SID
• Focal Spot Size
• Motion
• Angle

As Patient thickness vary, Spatial Resolution ______

Decreases, as natural OID is created with larger internal parts

As OID increases, Spatial Resolution ______

Decreases, as the difference between the actual part edge and the projected part edge increases

As SID increases, Spatial Resolution ______

Increases, as the difference between the actual part edge and the projected part edge decreases

As focal spot size increases, Spatial Resolution ______

Decreases, as the heel effect decreases and the divergence of the beam increases, and the penumbra is more pronounced

As motion occurs, Spatial Resolution ______

Decreases, as the edge of a part is exposed at multiple points

Angulation with the Part or Tube ________ Spatial Resolution

Decreases, as the difference between the actual part edge and the projected part edge increases

Factors that affect Distortion are influenced by _______ or _______

Size or Shape

What are the factors that affect Distortion?

• Patient
• OID & SID
• Angle

As Patient thickness vary, Distortion ______

Increases, as displacement and OID are created with larger or additional internal parts

As SID Increases, Size Distortion _______

Decreases, as the beam is more parallel when it reaches the part

As OID Increases, Size Distortion _______

Increases, as the beam is more divergent when it reaches the part

As anglulation increases, Shape Distortion _______

Increases

Part becomes Foreshortened as ______

Part isn't parallel to IR

Part Becomes Elongated as _______

Tube isn't Perpendicular to IR

What is the Anatomically Programmed Technique menu?

Preset techniques for individual exams

What is a Fixed kVp System?

Allows for consistent Contrast as only mAs is changed based on the patient

What is a Variable kVp System?

Allows for Dose efficiency but varied contrast

What are some special considerations warranting adjustment of technical factors?

• Casting
• Pathologic Factors
• Age
• BMI
• Use of Contrast
• Grids or OID

Patients with casts require an ____ in technical factors due to material present

Increase

Destructive Pathology require an ___ in technical factors

Decrease

Additive Pathology require an ___ in technical factors

Increase

Orthopedic Device require increased ________

kVp

Variation in BMI requires a change to ______

mAs

In pediatric CXR _____ is adjusted while ______ is consistent

kVp; mAs

In other pediatric exams _____ is adjusted while ______ is consistent

mAs; kVp

Use of Contrast Media require increased ______

kVp

Using Grids or the Air gap technique requires increased ________

mAs

Exams focused on Soft tissue structures require decreased ______

kVp

Internal Bleeding require an increase in _______

mAs

CXR with Pneumothorax requires ______ in technical factors

Decrease