* CT SYSTEM COMPONENTS & DATA ACQUISITION *

What is data acquisition in CT?

The process of obtaining information to create images.

What are the main components of a CT system?

Console/computer, patient table, and gantry.

What does the CT system console do?

Controls data acquisition, image processing, viewing, display, and storage.

True or False: The CT system console is also where images can be viewed and displayed.

True

What is the patient table made of?

Carbon graphite.

What is the weight limit for a CT patient table?

Up to 450 lbs.

In helical scanning, how does the table move?

Continuously during image acquisition.

What are the main components located in the CT gantry?

X-ray tube, filters, collimators, detectors, and generator.

What is the diameter range of a typical CT gantry?

70-90 cm.

What must CT x-ray tubes be able to handle?

High heat dissipation and high x-ray intensity.

What are the common focal spot sizes for CT tubes?

0.5 mm and 1.0 mm.

What is the typical kVp range for CT x-ray tubes?

120-140 kVp.

What is the function of a tube warm-up?

Prevents thermal shock and extends tube life.

True or False: You only need to warm up the CT tube if it has been idle for more than two hours.

True

What type of beam geometry was used in first-generation scanners?

Pencil beam.

What type of beam geometry was used in second, third, fourth, and sixth generation scanners?

Fan beam.

What beam geometry is used in seventh-generation CT scanners?

Cone beam.

What type of CT scanner was the fifth generation?

Cardiac scanner (electron beam).

What type of scanners are considered MDCT systems?

Seventh generation and higher.

What is the function of the CT generator?

Produces high voltage and transmits it to the x-ray tube.

True or False: High-frequency generators are the only type used in CT today.

True

What determines the range of exposure techniques in CT?

Generator power capacity.

What is the function of filters in CT?

Remove low-energy x-rays to create a uniform beam and reduce patient dose.

What is the purpose of collimators in CT?

Restrict x-ray path, reduce scatter, and define slice thickness.

What are pre-patient collimators?

Located before the patient; control slice thickness and patient dose.

What are post-patient (pre-detector) collimators?

Restrict unwanted x-rays before the detector and reduce scatter.

What is the function of CT detectors?

Capture x-rays exiting the patient and convert them into signals for image formation.

What are xenon gas detectors?

Detectors using pressurized xenon gas, 60-87% efficient, used in third-generation scanners.

What are solid-state detectors?

Scintillation detectors with photodiodes, 99-100% efficient, used in 3rd-7th generation scanners.

What are garnet detectors known for?

High speed and fast recovery, but expensive.

What is the difference between uniform and variable detector arrays?

Uniform arrays have detectors of equal size; variable arrays have smaller central detectors and larger outer ones.

True or False: The detector array is the CT system's input device.

True

What is the function of the data acquisition system (DAS)?

Amplifies, converts, and transmits signals from detectors to the computer.

What are the two main scanning methods in CT?

Axial (step-and-shoot) and helical (spiral).

Which generations of CT scanners used axial scanning?

First, second, third, and fourth generation.

Which generation introduced helical scanning?

Sixth generation.

What is slip ring technology?

A system that provides continuous power and data transfer, eliminating cable winding.

What are the two types of slip rings?

High-voltage and low-voltage.

True or False: Slip rings allow the x-ray tube to rotate continuously around the patient.

True

What is pitch in CT scanning?

The ratio of table movement per rotation to slice thickness.

What is the formula for pitch in single detector CT?

Pitch = table increment (I) ÷ slice thickness (S).

What does a pitch of 1 represent?

Table speed equals slice thickness.

What does a pitch less than 1 indicate?

Oversampling.

What does a pitch greater than 1 indicate?

Undersampling or gaps in data.

If the table moves 10 mm/sec and slice thickness is 5 mm, what is the pitch?

Pitch = 10 ÷ 5 = 2 (undersampling).

If the table moves 5 mm/sec and slice thickness is 10 mm, what is the pitch?

Pitch = 5 ÷ 10 = 0.5 (oversampling).

What is the formula for beam pitch in MDCT?

Beam Pitch = Table Increment ÷ (number of slices × slice thickness).

If the table moves 10 mm/sec, slice thickness is 1.25 mm, and there are 4 slices, what is the pitch?

10 ÷ (4×1.25) = 2.

If the table moves 5 mm/sec, slice thickness is 2.5 mm, and there are 4 slices, what is the pitch?

5 ÷ (4×2.5) = 0.5.

True or False: Increasing pitch shortens scan time but increases image noise slightly.

True

True or False: Increasing pitch increases patient dose.

False

What artifact can occur when pitch is too high?

Streak artifact.

What is the formula for SDCT anatomy coverage?

Coverage = Pitch × total acquisition time × (1 ÷ rotation time) × slice thickness.

What is the formula for MDCT anatomy coverage?

Coverage = Pitch × total acquisition time × (1 ÷ rotation time) × (slice thickness × slices per rotation).

What are advantages of MDCT systems?

Reconstruction anywhere in data, adjustable slice thickness, faster scans, overlapping reconstruction.

What is the difference between slice thickness and image thickness?

Slice thickness = how data was acquired; image thickness = how data is reconstructed for viewing.

What is dual-source CT?

CT system using two x-ray tubes and detectors at different energy levels for faster imaging.