Introduction
Image evaluation is one of the most important skills you’ll develop as a radiologic technologist. It’s not just about taking the image – it’s about assessing its diagnostic quality and determining whether it needs to be repeated. This blog post will walk you through a systematic approach to evaluate radiographs and identify both technical issues and pathological findings.
Why Image Evaluation Matters
When you critique an image, you’re asking several critical questions:
- Is this image of diagnostic quality?
- Will it provide the radiologist with the information they need?
- Does it clearly demonstrate the anatomical area of interest?
- Are there any pathological findings visible?
- Could I have produced a better image with different techniques or positioning?
Your ability to answer these questions accurately can directly impact patient care and radiation safety by reducing the need for repeat exposures.
A Systematic Approach to Image Evaluation
The 5-Step Method
To make image evaluation more manageable, follow this 5-step method:
1. Patient Information & Order Assessment
- Check the patient’s demographic information
- Review the clinical history and reason for examination
- Verify the correct procedure was performed
- Check proper marker placement and orientation
2. Technical Quality Evaluation
- Assess exposure (density/brightness and contrast)
- Check for proper collimation
- Evaluate for proper positioning
- Look for motion or artifacts
- Assess for proper penetration
3. Anatomical Accuracy
- Verify all required anatomical structures are included
- Check alignment and centering
- Assess for proper positioning per protocol
- Verify proper patient preparation if applicable
4. Pathology Recognition
- Identify any obvious abnormalities
- Note any potential pathological findings
- Recognize normal variants vs. abnormal findings
5. Final Decision
- Determine if the image is of diagnostic quality
- Decide if a repeat exposure is needed
- Consider if additional or modified views would be helpful
Detailed Critique Elements
1. Exposure Factors
Brightness/Density
- Overexposed: Image appears too dark (in conventional radiography) or too bright (in digital)
- Underexposed: Image appears too light (in conventional) or too dark (in digital)
- Look For: Ability to see both soft tissue and bony structures with appropriate detail
Contrast
- High Contrast: Sharp difference between blacks and whites, fewer gray tones
- Low Contrast: Many shades of gray, less distinction between structures
- Optimal Contrast: Depends on the anatomical area being imaged (chest requires long-scale contrast, extremities can use shorter-scale)
Penetration
- Underpenetrated: Bones appear very white, lacking detail within bony structures
- Overpenetrated: Bones appear too gray or transparent, lacking definition
- Properly Penetrated: Bony trabecular patterns visible, appropriate density through all structures
2. Positioning Assessment
Chest Radiography
- PA Projection:
- Full inspiration (10 posterior ribs visible)
- No rotation (medial ends of clavicles equidistant from vertebral column)
- Scapulae out of lung fields
- Proper centering (T4-T5 level)
- Proper collimation
- Lateral Projection:
- Full inspiration
- True lateral (superimposed posterior ribs)
- Arms raised sufficiently
- No rotation (superimposed thoracic vertebral bodies)
Abdominal Radiography
- AP Projection:
- Proper centering (L3 level)
- Proper collimation (diaphragm to symphysis pubis)
- No rotation (symmetric iliac wings)
- Proper exposure of whole abdomen
- No motion blur
Extremity Radiography
- Hand/Wrist:
- AP: Fingers slightly spread, no rotation
- Lateral: True lateral position of the wrist
- Oblique: Proper 45° rotation
- Knee:
- AP: No rotation (symmetric femoral condyles)
- Lateral: Superimposed femoral condyles, fibula posteriorly overlapped ~1/3 by tibia
- Weight-bearing (if ordered): Standing with equal weight distribution
Spine Radiography
- Cervical Spine:
- AP: Open mouth for odontoid (teeth not superimposed)
- Lateral: All 7 vertebrae and C7-T1 junction visible
- No rotation in either projection
- Lumbar Spine:
- AP: Spinous processes aligned in the center
- Lateral: Vertebral bodies superimposed, pedicles superimposed
3. Common Positioning Errors to Look For
Rotation
- Signs: Asymmetrical appearance of paired structures
- Example: In chest radiography, one clavicle appears shorter than the other
Improper Centering
- Signs: Important anatomy cut off or not centered in the collimation field
- Example: Cutting off the costophrenic angles on a chest radiograph
Improper SID (Source-to-Image Distance)
- Signs: Magnification issues, geometric unsharpness
- Example: Cardiac silhouette appears larger than actual size due to short SID
Improper Patient Preparation
- Signs: Presence of items that could obscure pathology
- Examples: Jewelry, clothing artifacts, or unprepared bowel in abdominal studies
Motion
- Signs: Blurring of structure outlines
- Example: Blurred cardiac silhouette due to cardiac motion or patient breathing
Pathology Recognition Basics
While detailed pathology recognition requires significant study, here are some fundamental patterns to look for:
Increased Density (Appears Whiter)
- Consolidation (pneumonia)
- Pleural effusion
- Masses/tumors
- Bone fractures (acute fracture lines)
- Foreign bodies
Decreased Density (Appears Darker)
- Pneumothorax
- Emphysema
- Bone destruction/lysis
- Air in abnormal locations (free air under the diaphragm)
Altered Contours or Alignments
- Fractures
- Dislocations
- Vertebral misalignments
- Abnormal organ contours
Size Abnormalities
- Cardiomegaly (enlarged heart)
- Organomegaly (enlarged liver, spleen)
- Atrophy or hypoplasia (smaller than normal structures)
Practice Exercise: Step-by-Step Image Critique
Example: PA Chest Radiograph Critique
- Patient Information:
- 65-year-old male
- Clinical history: Shortness of breath, productive cough
- Technical Quality:
- Exposure: Appropriately penetrated, lung markings visible through heart
- Contrast: Good contrast showing both soft tissue and bony structures
- Collimation: Proper field size including all lung fields
- Positioning Assessment:
- Patient Rotation: Minimal rotation (clavicles nearly symmetric)
- Inspiration: Adequate (10 posterior ribs visible above diaphragm)
- Scapulae: Rotated away from lung fields
- Centering: Properly centered at T4-T5
- Anatomical Structures:
- All lung fields included
- Both costophrenic angles visible
- Trachea and major bronchi visualized
- Heart and major vessels included
- Potential Pathology:
- Increased density in right lower lobe (potential pneumonia)
- Heart size slightly enlarged (potential cardiomegaly)
- No pneumothorax or pleural effusion identified
- Final Assessment:
- Diagnostic quality image
- Minimal rotation present but does not compromise diagnostic value
- Areas of concern: Right lower lobe consolidation, cardiac enlargement
Practice Methods to Improve Your Skills
- Create a Personal Library:
- Collect sample images with common pathologies
- Practice identifying normal vs. abnormal findings
- Review various positioning errors
- Use a Checklist Approach:
- Develop a written checklist for each common projection
- Systematically evaluate each element
- Compare your findings with reference materials
- Group Study Critiques:
- Share images with classmates
- Take turns critiquing and explaining findings
- Compare observations and interpretations
- Mock Evaluation Sessions:
- Set up timed sessions to simulate real-world pressure
- Complete full critiques within appropriate timeframes
- Have an instructor or peer review your evaluations
- Digital Software Practice:
- Use radiographic positioning software if available
- Practice manipulating images digitally to correct issues
- Learn how to optimize digital image display
Resources for Further Study
- Textbooks and References:
- Merrill’s Atlas of Radiographic Positioning & Procedures
- Bontrager’s Textbook of Radiographic Positioning and Related Anatomy
- Radiographic Image Analysis by Kathy McQuillen Martensen
- Online Resources:
- ASRT Directed Readings on Image Analysis
- Radiopaedia.org for pathology recognition
- MedPix Clinical Image Database
- Mobile Apps:
- Rad Tech Reference Guide
- Radiopaedia App
- Radiology Assistant
Conclusion
Image evaluation is a skill that develops over time with consistent practice. By following a systematic approach and understanding what makes a diagnostic quality image, you’ll build confidence in your ability to critique radiographs effectively. Remember that even experienced technologists continue to learn and refine these skills throughout their careers.
The more images you evaluate, the more patterns you’ll recognize, and the more confident you’ll become in your assessments. Don’t be discouraged if you miss findings initially – this is a normal part of the learning process. With practice and guidance from instructors, you’ll develop the critical eye needed for excellent radiographic image evaluation.
Quick Reference Guide: Common Projection Requirements
Chest X-ray (PA)
- Full inspiration (10 posterior ribs)
- No rotation (symmetric clavicles)
- Scapulae out of lung fields
- Full visualization of lung fields
- Proper penetration (faint outline of vertebrae visible through heart)
Abdomen (AP Supine)
- Diaphragm to symphysis pubis included
- Symmetric iliac wings (no rotation)
- Visible psoas muscle outlines
- Appropriate exposure of the entire abdomen
- Proper collimation
Hand (PA)
- All phalanges, metacarpals visible
- No rotation (lateral aspect of 5th digit straight)
- Soft tissue and bony detail both visible
- Proper collimation to include fingertips and wrist joint
Knee (AP)
- Equal joint spaces medially and laterally
- Symmetric femoral condyles (no rotation)
- Patella centered over femur
- 1⁄2 inch of proximal tibia/fibula shown
- 1-2 inches of distal femur shown
Lumbar Spine (AP)
- T12 through sacrum included
- Spinous processes aligned centrally
- Symmetric pedicles and transverse processes
- Clear visualization of intervertebral disc spaces
- No rotation (symmetric pedicles)
Cervical Spine (Lateral)
- All 7 cervical vertebrae and C7-T1 junction visible
- Proper alignment of posterior vertebral line
- Spinous processes fully visualized
- Mandible not superimposed on upper vertebrae
- Proper penetration to see bony details