Radiological imaging is at the heart of modern medical diagnosis. Every day, radiographers produce thousands of medical images that help clinicians detect, diagnose, and treat diseases.
To create a high-quality radiographic image, a radiographer must understand the physics behind X-rays, how images are formed, and the essential factors that influence image quality.
This guide provides detailed, clear, and exam-oriented notes on radiological images — ideal for radiography students, educators, and professionals.
⭐ What Is a Radiological Image?
A radiological image is a visual representation of internal body structures produced using X-rays or other radiation. The image is created based on the differential absorption of X-rays by various tissues.
How Tissues Appear on X-Ray Images
-
Bone (Radiopaque): Appears white because it absorbs more X-rays
-
Soft Tissue: Appears various shades of gray
-
Air (Radiolucent): Appears black because it allows X-rays to pass through
This difference in absorption forms the contrast seen on X-ray images.
⭐ How Radiological Images Are Formed
Radiographic image formation involves four major steps:
1️⃣ X-ray Production
High-speed electrons hit a tungsten target inside the X-ray tube, producing X-rays.
2️⃣ X-ray Interaction with Patient
X-rays are:
-
Absorbed
-
Scattered
-
Transmitted
depending on tissue type.
3️⃣ Image Detection
The transmitted radiation reaches:
-
Film (in conventional systems)
-
CR cassette
-
DR flat-panel detector
4️⃣ Image Processing
The image is developed chemically (film) or digitally (CR/DR) and displayed on a monitor.
⭐ Types of Radiological Images
Radiological imaging systems include:
📌 Conventional Radiography
Film-screen systems, now mostly outdated.
📌 Computed Radiography (CR)
Uses photostimulable phosphor plates.
📌 Digital Radiography (DR)
Uses flat-panel detectors for instant imaging.
📌 Fluoroscopy
Real-time moving X-ray images.
📌 CT Scan
Cross-sectional images reconstructed by computers.
📌 Mammography
High-resolution breast imaging.
⭐ Image Quality Factors Every Radiographer Must Know
To produce diagnostic-quality images, radiographers must control key factors:
1. Density / Brightness
Degree of image darkening — controlled by mAs.
2. Contrast
Difference between adjacent tissues — controlled by kVp.
3. Sharpness (Spatial Resolution)
Clarity of structural edges — affected by motion, focal spot size, and detector resolution.
4. Magnification
Caused by increased OID or decreased SID.
5. Distortion
Shape or size misrepresentation due to incorrect alignment.
6. Noise
Graininess in digital images from low exposure or electronic interference.
⭐ Factors That Affect Image Quality
Physical Factors
-
Tissue thickness
-
Tissue density
-
Atomic number
-
Scatter radiation
Technical Factors
-
kVp
-
mAs
-
Source-to-Image Distance (SID)
-
Object-to-Image Distance (OID)
-
Image receptor characteristics
⭐ Common Radiographic Artifacts
Artifacts are unwanted features that may mimic pathology. Examples include:
-
Motion blur
-
Grid cutoff
-
Double exposure
-
Processing errors
-
Digital detector defects
Radiographers must identify and prevent artifacts to avoid misdiagnosis.
⭐ Radiographic Image Evaluation Checklist
A high-quality diagnostic image must include:
✔️ Correct positioning
✔️ Proper exposure
✔️ Adequate contrast
✔️ Good sharpness (no motion)
✔️ Proper collimation
✔️ Presence of side markers & patient ID
✔️ No artifacts
This ensures the radiologist receives an optimal image for interpretation.
⭐ Radiographer’s Role in Image Formation
Radiographers are responsible for:
-
Selecting correct exposure factors
-
Positioning patients accurately
-
Using proper shielding and collimation
-
Ensuring radiation safety
-
Evaluating image quality
-
Minimizing repeat exposures (ALARA principle)
Their technical skill directly impacts diagnosis and patient safety.
⭐ PACS: Image Storage & Retrieval
Modern radiology uses the PACS (Picture Archiving and Communication System) to store, view, and share images digitally. PACS improves workflow efficiency and eliminates the need for physical films.
⭐ Radiation Protection in Radiography
Safety is essential in radiology. Radiographers must follow the ALARA principle:
“As Low As Reasonably Achievable.”
Key precautions include:
-
Lead apron
-
Thyroid shield
-
Gonadal protection
-
Beam collimation
-
Proper exposure settings
-
Maintaining distance when possible
⭐ Summary
Radiological images are essential tools for diagnosis. To produce high-quality images, radiographers must understand the science behind X-ray production, image formation, and quality control.
A well-trained radiographer ensures clear images, accurate diagnoses, and safe radiation practices.
⭐ Recommended Books for Radiography Students
-
Carlton & Adler – Principles of Radiographic Imaging
-
Bushong – Radiologic Science for Technologists
-
Bontrager & Lampignano – Radiographic Positioning & Anatomy
-
Clark’s Positioning in Radiography
