Different projections are taken at different angles and they encounter different attenuation due to the anatomy and it is read. The info is then recorded and a profile is produced which makes a sinogram. The sinogram cannot be read so recon algorithm is applied so it can be read

There is less attenuation

table translates to first bit of anatomy and it is repeated until planned vol is covered. it starts and stops. no overscans. not constantly irradiating

patient constantly moving through gantry as tube rotates around patient. volumetric data used to reconstruct images in 3d once acquired

affects visibility and detection. graininess can be seen as a result of random variation in the ct number of similar materials

being able to recognise objects that have similar densities as separate from each other

being able to separate small objects from each other measured in line pairs

distortion and error unrelated to subject

beam passes through a dense area and the low energy photons are absorbed and the high energy ones remain and this is the increased average beam energy

not enough photons or data. passing through dense areas of anatomy means there’s increased attenuation so photons are removed so there’s less signal and more noise

Electrical conductive, rings and brushes that transmit an electrical energy across a surface. Allows continuous rotation of the gantry. ScanTime is reduced. Made spiral and helical scanning possible.

Thinner in the middle and thicker on the edges . There is an even number of photons, so the image quality is better.

continuous, volume scanning patient is being constantly translated through the gantry. There is a big load on the tube, so not a lot of anatomy is covered and the scan time is longer

A single row of detectors replaced with multiple rows. covers more anatomy, faster, scan, time, large number of detectors and better you and better usage of the tube output

It is good for bone visualisation. You can reconstruct multiple planes. It is a quick procedure cross-sectional so you can see different axes. There is no superimposition of anatomy and the whole body coverage in a trauma situation

this converts measured data to an image. It is fast and direct. It is part of the post processing. attenuation measurement is taken at a particular angle till enough is taken then spatial distribution can be worked out and then made into a sinogram. sharpens image. back projection produces blurry images.

KV determines energy level and penetrating power of x-ray beam. It affects patient dose, image noise and contrast. High KV, with the same Mas reduces noise decreases image contrast and increases patient dose. lower kv- Reduces radiation risk

Mas is the product of the x-ray tube current and exposure time, and it determines the number of photons in the x-ray beam . It affects patient dose and image noise. higher mas value reduces image noise and improves low contrast resolution. This is important for brain and abdomen scans as there is a differentiation of structures with differences in density is required lower mas when imaging anatomy of inherent high tissue contrast, such as bone and lung

MAS delivery is optimised to adapt appropriate Mas to the individual . The scanner measures the patient and insures there is consistent image quality and the dose is low as reasonable as possible for all body sizes. it depends on patient size, attenuation profile of patient in z direction, online angular attenuation profile during tube rotation.

One 360° rotation. More rotations, more samples. Shorter rotation time means optimal contrast enhancement, and freezing the motion. Longer rotation time can be used when patient movement is small and when increased dose and samplings are needed to improve image details.This also improves resolution

The pitch is the amount the table move in a rotation . It is a helical scan parameter. It is the relationship between table travel and detector coverage per rotation. Higher pitch faster the table travels and shortest duration. Pitch = table feed per rotation / z coverage. Higher the pitch better image quality.

Arms raised above the head benefits for patient dose and image quality Less image artefacts from beam, hardening and photon starvation

Space where is Central ray of radiation beam passes. Mas modulation is needed to function properly, so the patient needs to be centred at the isocentre of the gantry. measurements will only be accurate if patient is at isocenter. Patient positioning is important because they need to be at the isocenter so appropriate Mas can be calculated. The correct dose will be given and the image quality will be better.

Increase scan time. Increased radiation dose achieve same Image quality decreased affect of partial volume. Less photon information so less signal more noise

Distance between each recon image, no gaps between data

kernel applies maths algorithm that digitally filters the raw data during recon. Give image a specific impression between noise and spatial resolution. Sharp kernels have high spatial resolution and increased noise so it is better for lung and bone Smooth kernels have low spatial resolution and decrease noise and this improves low contrast resolution, so it is better for soft tissue

Allows measurement of material density in voxel calibrated to water which is 0