Image Production · ARRT 2025
Image Evaluation and Grid Artifacts
Image evaluation criteria (positioning, technical factors, anatomy, no artifacts), grid errors, and the systematic approach to image critique for the ARRT.
Overview
Image Evaluation and Grid Artifacts is the close-the-loop chapter. Every image you produce must be evaluated before the patient leaves the room. The ARRT registry tests image evaluation in two forms: identify what's wrong with this image, and decide what to do (repeat, accept, or troubleshoot). Both require a systematic checklist.
The diagnostic-quality checklist in order: positioning (correct anatomy demonstrated, no rotation, central ray correctly placed), technical factors (adequate density, appropriate contrast, motion-free), anatomy (all required structures included, no clipping), no artifacts (no metal, jewelry, gowns with hooks, hair clips, motion blur, double exposure), correct markers (R or L lead marker visible inside the collimated field, anatomically correct side). If any item fails, the radiographer evaluates whether the image is still diagnostic for the clinical question. If yes, send it. If no, repeat, but document the repeat reason.
Grid artifacts are the most-tested image evaluation topic. Off-center grid: the central ray is not aligned with the grid centerline. The image is uniformly light because lead strips absorb most of the diverging beam. Off-level grid: the IR is tilted left-right. One side of the image is dark, the other light, with a smooth gradient. Off-focus grid: the SID is outside the grid's focal range. Lateral edges of the image are dark. Upside-down grid: the focused side faces down. Center of the image is properly exposed; both edges are dark and worsen toward the periphery. Solution: never lift a focused grid without confirming orientation arrows. Other artifacts to recognize: motion blur (soft, blurred edges), double exposure (overlapping images on the same IR), grid lines (Moiré with digital systems), Gibbs phenomenon (ringing at high-contrast edges in over-processed digital images), and image stitching errors (long-spine or long-bone composite images that don't align). Repeat exposure rate (REE) is a department-level QC metric, ideally <5%, anything above 8% triggers root cause analysis.
What you’ll learn in this chapter
The 10 lessons in this chapter break down as follows. The full lesson content is unlocked when you start a free account.
The Guiding Principle
- What Image Evaluation Aims For
Factors Affecting Detail
- Universal Factors Affecting Sharpness
- Dynamic Range: Digital’s Latitude Advantage
Error Case Studies
- Technical Factor Errors
- CR Equipment Handling Errors
- Grid Misalignment Artifacts
Knowledge Check
- Question 1 of 4 Quiz
- Question 2 of 4 Quiz
- Question 3 of 4 Quiz
- Question 4 of 4 Quiz
Key terms in this chapter
These are the 7 terms most likely to appear on the ARRT registry from this chapter. Use them as a flashcard pre-quiz.
- Diagnostic Quality Checklist
- Positioning, technical factors, anatomy, no artifacts, correct markers. Apply systematically to every image.
- Off-Center Grid Cutoff
- Uniform image light. Caused by misalignment of CR with grid centerline.
- Off-Level Grid Cutoff
- Smooth left-right density gradient. Caused by IR being tilted relative to CR.
- Off-Focus Grid Cutoff
- Lateral edges dark. Caused by SID outside the grid's specified focal range.
- Upside-Down Grid
- Center properly exposed, both edges dark and worsening peripherally. Always verify grid orientation arrows.
- Repeat Exposure Rate (REE)
- Department QC metric. Ideal <5%; >8% triggers root cause analysis.
- Lead Marker Rule
- R or L lead marker must be visible inside the collimated field, anatomically correct, before exposure.
Sample practice question: Image Acquisition
One free sample from the 98-question Image Acquisition bank. See the format, the rationale style, and the difficulty before you sign up.
An adult chest x-ray is performed at 80 kVp and 4 mAs at 72 inches SID. To maintain density at 40 inches SID, what new mAs is required?
Show answer and rationale
A, Incorrect: 1 mAs would result in significant underexposure. Apply the density maintenance formula.
B, Incorrect: Distance is decreasing, so mAs should decrease, but not by half.
C, Correct: Correct. Density maintenance formula: mAs₂ = mAs₁ × (SID₂² / SID₁²) = 4 × (40² / 72²) = 4 × (1600/5184) = 4 × 0.309 ≈ 1.2 mAs. Closer distance means more intensity, so less mAs is needed.
D, Incorrect: 13 mAs would more than triple the exposure. Reversed formula error, increasing distance requires more mAs, not less.
Read the full chapter, free.
The free tier unlocks one complete chapter (10 lessons), 50 practice questions, and 1 sample timed exam. No credit card required.
Frequently asked questions
What does the ARRT Radiography Image Production category cover?
Image Evaluation and Grid Artifacts is the close-the-loop chapter. Every image you produce must be evaluated before the patient leaves the room. The ARRT registry tests image evaluation in two forms: identify what's wrong with this image, and decide what to do (repeat, accept, or troubleshoot). Both require a systematic checklist.
How many lessons are in the Image Evaluation and Grid Artifacts chapter?
This chapter contains 10 lessons across 4 sections, plus a knowledge-check quiz at the end. The full lesson content is unlocked with a Premium subscription. The free tier includes the first chapter complete.
Is this chapter aligned with the ARRT 2025 Content Specifications?
Yes. Every chapter on this site maps directly to the ARRT Radiography Content Specifications effective 2025. This chapter falls under the Image Production domain of the official ARRT exam blueprint.