Introduction to Radiologic Technology

Fundamentals of Radiography

• Definition: Process of creating digital or film images of internal anatomical structures using x-rays passed onto an Image Receptor ($IR$).

• Modalities: Traditional (analog film), Computed Radiography ($CR$ - photostimulable phosphor plates), and Digital Radiography ($DR$ - direct/indirect detectors).

• Clinical Roles:

  • Radiographer: Radiologic Technologist specializing in creating x-ray diagnostic images.

  • Radiologist: Medical physician who interprets radiographs to diagnose diseases and injuries.

Technical Parameters and Exposure Factors

• Exposure Factors:

  • $mAs$ (Milliamperage-Seconds): $\text{mAs} = \text{mA} \times \text{time}$; controls total photon quantity emitted.

  • $kVp$ (Kilovoltage Peak): Controls electrical potential across tube, beam energy, and penetration power.

  • $SID$ (Source-to-Image Distance): Distance from tube target to $IR$, measured manually with a tape measure.

• Interaction Characteristics:

  • Radiolucent: Easily penetrated by x-rays (e.g., soft tissues, fat, air).

  • Radiopaque: Absorbs/blocks x-rays (e.g., bone, metals, contrast, lead shielding).

Primary Image Quality Factors

• Evaluation Criteria:

  • $IR$ Exposure / Density: Overall image blackening on film or total exposure reaching digital detector ($RE$).

  • Subject Contrast: Brightness difference between adjacent tissues (Low = long scale/many grays; High = short scale/black-to-white).

  • Recorded Detail: Structural sharpness and accuracy of anatomical borders.

  • Distortion: Misrepresentation of true size (magnification) or shape (elongation/foreshortening).

Radiation Types and Beam Mechanics

• Radiation Classifications:

  • Primary: Initial x-ray beam exiting tube before entering patient.

  • Secondary: Radiation produced after interaction with matter (includes scatter).

  • Remnant: Exit beam reaching $IR$ to form image.

• Beam Phenomena:

  • Scatter Radiation: Deflected secondary radiation causing image fog and reduced contrast.

  • Attenuation: Total reduction in beam intensity via absorption and scattering.

• Focal Spot Size:

  • Large: Used for thicker body parts requiring higher $mAs$ to distribute heat.

  • Small: Used for extremities to maximize spatial resolution and recorded detail.

Equipment, Cassettes, and Bucky Systems

• Control Panel: Located behind lead-lined protective wall; controls exposure factors ($kVp$, $mA$, time).

• Relative Speed ($RS$): Screen/cassette sensitivity (commonly 200\nIRS and 600\nIRS).

• Scatter Control:

  • Grid: Alternating lead strips absorbing scatter on thick body parts.

  • Bucky: Table or wall unit housing a moving grid to absorb scatter without visible grid lines.

Accreditation Organizations

• JRCERT: Premier accrediting body for radiography education programs (accredited over $625$ programs).

• Joint Commission: Principal accrediting body for healthcare facilities and hospitals.

Individual Certification and Professional Credentials

• ARRT: Founded $1922$; national exam requires passing score of $75$ or higher.

• Requirements: Annual dues, 24\nCE credits every $2$ years, and mandatory CQR evaluation every $10$ years.

Professional Societies and Associations

• ASRT: National US society, founded $1920$, over $153,000$ members.

• MSRT & ISRRT: State-level (Michigan) and global professional societies, respectively.

• Medical/Radiological Associations:

  • ABR: Certifies radiologists, radiation oncologists, and medical physicists.

  • ACR: Principal professional organization for US radiologists.

  • AMA: Largest medical association for physicians globally.

  • ARRS: Oldest continuously operating US radiologic society.

  • RSNA: Founded $1915$ in Chicago; hosts world's largest annual radiology meeting ($50,000+$ attendees).