CT lecture

🧠 CT History & Development

Q: Who created CT?
 A: Godfrey Hounsfield and Allan Cormack
(Wilhelm Roentgen discovered X-rays)

Q: What made CT technology possible?
 A:

  1. Computers

  2. Slip-ring technology

  3. High frequency, high capacity X-ray tubes

Q: What are the four generations of CT scanners?
 A:

  • First Generation: Translate-rotate motion, pencil beam, one detector

  • Second Generation: Translate-rotate, fan beam, detector array

  • Third Generation: Rotating fan beam and array of detectors

  • Fourth Generation: Rotating fan beam and stationary array of detectors

⚙ CT vs. Radiography

Q: What are radiography's 4 advantages over CT?
 A:

  1. Portability

  2. Lower radiation dose

  3. Lower cost

  4. Superior spatial resolution (film: 100 lp/mm vs. CT: 1-2 lp/mm)

Q: What percentage of X-ray exams are CT scans, and what dose do they deliver?
 A: CT = ~11% of X-ray exams, but over two-thirds of total radiation dose

Q: How does the dose from an abdominal CT compare to an AP abdomen X-ray?
 A: CT delivers ~50x higher dose (X-ray = 0.25 mGy)

📏 CT Image Concepts

Q: What is the range of CT numbers (Hounsfield Units)?
 A: -1000 to +1000

Q: What HU values represent key materials?
 A:

  • Air: -1000

  • Water: 0

  • Compact Bone: +1000

Q: What do Window Width (WW) and Window Level (WL) control?
 A:

  • WW: Contrast

  • WL: Brightness

Q: How has image matrix resolution improved in CT scanners?
 A:

  • Original: 80 × 80 = 6,400 pixels

  • Modern: 1024 × 1024 = 1,048,576 pixels

🧩 CT Components

Q: Name 5 core components of a CT system:
 A:

  1. Gantry

  2. Table

  3. Console

  4. Processor System

  5. High-voltage generator

(Also: Storage system, film printer, transformer, camera, table/gantry control)

💡 Image Formation & Processing

Q: What is convolution in CT?
 A: A digital image processing technique to modify pixel values using surrounding pixels via a convolution kernel

Q: What do different algorithms/filters do?
 A:

  • Edge enhancement: Good detail, more noise

  • Smoothing: Less noise, but less detail

🔄 Helical/Spiral CT

Q: What are the benefits of helical/spiral CT over conventional CT?
 A:

  • Faster volume coverage

  • Continuous rotation and patient movement

  • Reduces stair-step artifacts and misregistration

Q: What tech made spiral CT possible?
 A:

  • Slip-ring technology

  • Continuous couch motion

  • High-load X-ray tube (200 mA+)

  • Spiral weighting algorithm

  • Advanced cooling

  • Mass memory buffer

Q: What issues arise with helical CT data acquisition?
 A:

  • No defined slice

  • Increased effective slice thickness

  • Streak artifacts

  • Non-planar geometry

Q: What technique corrects these issues?
 A: Interpolation

🎓 Becoming a CT Technologist

Q: What registry must you have before becoming a registered CT tech?
 A: Radiography, Nuclear Medicine, or Radiation Therapy (ARRT primary registry)

Q: What education requirements began Jan 1, 2016?
 A: 16 hours of structured education in CT within 24 months of applying (RCEEM-approved or university)

Q: What is required for clinical experience?
 A:

  • Choose 25+ of 59 ARRT-listed procedures

  • 3-5 repetitions each

  • 125 total documented procedures

  • One procedure per patient per documentation

Q: What are the 3 ARRT exam sections and their question counts?
 A:
A. Patient Care and Safety – 36
B. Imaging Procedures – 75
C. Physics and Instrumentation – 54
Total: 165 questions

Q: How many CE credits are required every 2 years?
 A: 24 CE credits

📍 CT Licensure & Pay

Q: Name 5 states that require CT licensure.
 A: Michigan, Florida, Oregon, Tennessee, Wisconsin (among others)

Q: Michigan CT licensure requirements?
 A:

  • ARRT registered (radiographer or NMT)

  • 20 hours training OR advanced CT certification

Q: Average pay in Michigan vs. national?
 A:

  • Michigan: ~$67,000/year or $32/hr

  • National: ~$60,000/year or $29/hr

🧑‍⚕ Specialization & Work Environment

Q: Examples of CT Specializations?
 A:

  • Cardiac CT

  • Interventional CT

  • Pediatric CT

  • 3D rendering/processing

Q: What's good about working in CT?
 A:

  • Cutting-edge tech

  • Good pay

  • Job security

  • Independence

  • Interesting cases

Q: What's bad about working in CT?
 A:

  • High stress

  • Fast-paced exams

  • On-call & overtime

  • Emergencies (Code Blue)

Q: What's ugly about working in CT?
 A:

  • Smells/sights

  • Pathogen exposure

  • Angry patients/doctors

  • Death