CT lecture

Who created CT?

Godfrey Hounsfield and Allan Cormack.

What made CT technology possible?

Computers, slip-ring technology, and high frequency, high capacity X-ray tubes.

What are the four generations of CT scanners?

First: Translate-rotate, pencil beam, 1 detector

Second: Translate-rotate, fan beam, detector array

Third: Rotating fan beam and array of detectors

Fourth: Rotating fan beam with stationary array of detectors

What are radiography's 4 advantages over CT?

Portability, lower radiation dose, lower cost, superior spatial resolution.

What percentage of X-ray exams are CT scans and what dose do they deliver?

CT scans account for ~11% of X-ray exams but over two-thirds of total radiation dose.

How does the dose from an abdominal CT compare to an AP abdomen X-ray?

CT delivers ~50x higher dose than an X-ray (X-ray = 0.25 mGy).

What is the range of CT numbers (Hounsfield Units)?

-1000 to +1000.

What HU values represent key materials?

Air: -1000, Water: 0, Compact Bone: +1000.

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

WW controls contrast; WL controls brightness.

How has image matrix resolution improved in CT scanners?

Original: 80 × 80 = 6,400 pixels; Modern: 1024 × 1024 = 1,048,576 pixels.

Name 5 core components of a CT system.

Gantry, Table, Console, Processor System, High-voltage generator.

What is convolution in CT?

a digital image processing technique to modify images through a filter function.

Done by changing pixel values in the output image when we multiply pixel values in the input image by a weighting factor or convolution coefficient derived from an average value of surrounding pixels

What do different algorithms/filters in CT do?

Edge enhancement provides good detail with more noise; Smoothing reduces noise but less detail.

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

Faster volume coverage, continuous rotation and patient movement, reduces stair-step artifacts and misregistration.

What technology made spiral CT possible?

Slip-ring technology, continuous couch motion, high-load X-ray tube, spiral weighting algorithm, advanced cooling, mass memory buffer.

What issues arise with helical CT data acquisition?

No defined slice, increased effective slice thickness, streak artifacts, non-planar geometry.

What technique corrects issues arising with helical CT data acquisition?

Interpolation.

What registry must you have before becoming a registered CT tech?

Radiography, Nuclear Medicine, or Radiation Therapy (ARRT primary registry).

What education requirements began Jan 1, 2016, for CT techs?

16 hours of structured education in CT within 24 months of applying (RCEEM-approved or university).

What is required for clinical experience in becoming a CT tech?

Choose 25+ of 59 ARRT-listed procedures, 3-5 repetitions each, 125 total documented procedures, one procedure per patient per documentation.

What are the 3 ARRT exam sections and their question counts?

A. Patient Care and Safety – 36, B. Imaging Procedures – 75, C. Physics and Instrumentation – 54.

How many CE credits are required every 2 years?

24 CE credits.

Name 5 states that require CT licensure.

Michigan, Florida, Oregon, Tennessee, Wisconsin.

What are Michigan CT licensure requirements?

ARRT registered (radiographer or NMT) and 20 hours training or advanced CT certification.

What is the average pay for CT techs in Michigan vs. national?

Michigan: ~$67,000/year or $32/hr; National: ~$60,000/year or $29/hr.

What are examples of CT Specializations?

Cardiac CT, Interventional CT, Pediatric CT, 3D rendering/processing.

What's good about working in CT?

Cutting-edge tech, good pay, job security, independence, interesting cases.

What's bad about working in CT?

High stress, fast-paced exams, on-call & overtime, emergencies.

What's ugly about working in CT?

Smells/sights, pathogen exposure, angry patients/doctors, death.

what type of technology is CT

digital- always has been

what type of technology is x-ray

analog