Filtration in Clinical CT

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What is the main purpose of filtration in clinical CT?

To increase beam softness

To remove long-wavelength x rays (correct)

To enhance image contrast

To decrease patient dose

Which type of filtration contributes to producing uniform beam hardening in clinical CT?

Flat filters

Inherent filtration with 3 mm Al-equivalent thickness

No filtration is involved in beam hardening

Added filtration made of copper sheets (correct)

What effect does filtration have on the mean energy of the x-ray beam in CT?

Shifts the energy distribution to lower wavelengths

Increases the mean energy (correct)

Decreases the mean energy

No effect on the mean energy

Why is additional filtration introduced into the beam for a circular object in CT imaging?

To correct beam-hardening effects Signup and view all the answers

What material is typically used for added filtration in clinical CT?

Copper Signup and view all the answers

What is the thickness range of added filtration filters used in clinical CT?

0.1 to 0.4 mm Signup and view all the answers

What material are shaped filters, such as the 'bowtie' filter, typically made of in CT imaging?

Teflon Signup and view all the answers

Why are bowtie filters used in CT imaging?

To shape the beam and ensure uniform fluence at the detector Signup and view all the answers

What is the purpose of collimation during CT imaging?

To restrict the x-ray beam to the anatomy of interest Signup and view all the answers

What problem does overscanning pose in CT imaging with multi-row detectors?

Increased dose to the patient Signup and view all the answers

What is the purpose of adaptive section collimation in CT imaging?

To block exposure of tissue outside the imaged volume Signup and view all the answers

What do CT detectors convert the radiation beam from the patient into?

Electric signals Signup and view all the answers

Which factor contributes to detector efficiency by capturing photons transmitted from the patient?

Capture efficiency Signup and view all the answers

What does absorption efficiency refer to in terms of CT detectors?

The number of photons absorbed by the detector Signup and view all the answers

What is meant by conversion efficiency for CT detectors?

The ability to convert absorbed x-ray signals into electrical signals accurately Signup and view all the answers

What is indicated by an overall efficiency value less than 1 for CT detectors?

Required increase in patient radiation dose Signup and view all the answers

Which type of detector directly converts x-ray energy into electrical energy?

Gas-ionization detectors Signup and view all the answers

What is the basic configuration of a gas-ionization detector?

Series of individual gas chambers separated by tungsten plates Signup and view all the answers

What is used as the gas in gas-ionization detectors?

Xenon Signup and view all the answers

Which type of detector has a quantum detection efficiency (QDE) range of 95% to 100% for solid-state models?

Scintillation detectors Signup and view all the answers

Why is it important for x-ray detectors in CT systems to be stable with time?

To improve image quality consistency Signup and view all the answers

What is the purpose of the detector electronics (DAS) in CT systems?

Encoding measurements into binary data Signup and view all the answers

Which material is commonly used as a scintillator in CT imaging due to its desirable properties?

$CdWO_4$ (Cadmium Tungstate) Signup and view all the answers

What happens when x-rays fall onto a scintillation crystal in a scintillation detector?

$X$-rays generate flashes of light or scintillations Signup and view all the answers

What is the primary function of the detector electronics in CT systems?

'Measure the transmitted radiation beam' Signup and view all the answers

Which type of detector arrays are used in modern MSCT scanners?

Solid-state detector arrays Signup and view all the answers