Multislice and Single-slice CT Quiz

Computed Tomography Equipment Techniques

• Multislice Computed Tomography (MSCT) is a CT system with multiple rows of CT detectors, creating images of multiple sections. It differs from conventional CT systems, which only have one row.

Seventh Generation (MS/MD CT)

• MSCT (or multi-detector row CT), allows for quicker scans with improved image resolution.
• The time required for one revolution (scan time) is shortened to 0.5 seconds.
• The width of the slice (tomographic plane) is reduced to 0.5 mm.
• These improvements significantly enhance CT-based diagnostic techniques.

Difference Between MSCT and SSCT

• The key difference lies in the detector arrangement.
• Single-slice computed tomography (SSCT) uses a one-dimensional detector arrangement with individual detectors arranged in a single row.
• Multislice computed tomography (MSCT) employ multiple rows of detectors.
• Increasing detector rows increases coverage and decreases the amount of gantry rotations needed to image the selected field of view (scan length), thus reducing stress on the X-ray tube.

Detector Array Characteristics

• The detector array consists of groups connected to the detection system's motherboard.
• These arrays can be selectively activated or deactivated to produce varying slice thicknesses.
• Inner detector rows are narrower than outer rows. This allows for selective activation of inner rows for adjusting slice thickness.

Types of Detector Arrays

• Matrix detectors: Parallel rows of equal thickness (e.g., Philips).
• Hybrid detectors: Smaller detector rows concentrated in the center (e.g., Siemens).
• Adaptive array detectors: Varying thicknesses of detector rows, wider towards the ends (e.g., Toshiba).

Significant Differences Between SSCT and MSCT

• Slice thickness and X-ray beam width: In SSCT, ideal slice thickness is determined by X-ray beam collimation. In MSCT, slice thickness is determined by detector configuration.
• Beam configuration effects: MSCT, using a cone-shaped beam, leads to more pronounced streak artifacts compared to the fan-shaped beam in SSCT.
• The z-axis width of the X-ray beam is wider when exiting a patient compared to entering, in both cases. This difference in image sampling, causes discrepancies at 0° and 180°, resulting in inconsistencies and partial volume streaking.

Advantages of MS/MD CT

• Fast imaging of large tissue volumes.
• Useful for studies with potentially moving patients.
• Ability to cover large body sections in short times with thin beams to enable high-detail slice images/three-dimensional (3D) images.
• Reduced x-ray tube strain compared to single row scanning due to the use of multiple arrays.

Pitch of MS/MD CT

• Beam pitch and detector pitch are crucial.
• Beam pitch = Table travel per gantry rotation divided by beam width.
• Detector pitch = Detector width divided by the number of active detectors.

Table of Scanning Time Comparison

• Comparing scanning times between single-row and multiple-row detectors reveals the benefits of multiple-row CT scanners in terms of faster scan times for various regions of the body.

Eighth Generation (Dual-source CT)

• DSSCT uses two X-ray tubes and corresponding detectors arranged at 90-degree angles within the gantry.
• These simultaneously rotate and acquire data, reducing scan time.
• This technology doubles the resolution and increases the speed of image acquisition compared to single source CT.

Dual Source Single Energy (DSSE)

• Fast volumetric coverage for obese patients.

Dual Source Dual Energy (DSDE)

• Combines dual-energy acquisition with data processing and sets X-ray tubes at differing settings to offer high specificity.

Single Source Dual Energy (SSDE)

• A single X-ray tube with fast kV switching (between low and high energies) is used.

• This technology is paired with a dual detector layer to acquire both low and high energy levels simultaneously.

• Differentiation between various materials is improved using two energy images because of unique attenuation profiles.

• Contrast generation depends on variable photon attenuation of body components like soft tissues, air, and calcium.

• Degree of attenuation is based on tissue composition and the energy level of the photons.