0:01

In this part of the lecture, I want to focus on the

0:04

fundamental of CT image quality,

0:07

because the topic discussed under this section is very

0:11

critical to understand and the physics behind

0:15

it and how it can impact the diagnosis and so forth.

0:19

When I want to talk about CT image quality, I like

0:22

to look at the scan parameters,

0:26

which impacts both the patient dose and image quality in CT.

0:31

It's almost like looking like a chef at the ingredients

0:35

before you're making a dish.

0:37

So you have various ingredients here,

0:40

and the dish taste depends on how the ingredients are mixed and matched.

0:45

Similar analogy can be thought for the CT, the scan parameter.

0:49

Among the scan parameters, which impact both the image

0:53

quality or radiation dose in CT,

0:57

I like to group into three different buckets.

0:59

The primary factors on the left-hand side is very

1:03

important for anyone to understand the basic principle of CT.

1:08

And because especially if you're involved or you want

1:12

to change anything or adjust the protocol or modify a CT

1:16

clinical protocol,

1:18

understanding these principles really have an impact on how

1:22

you can adjust the protocol.

1:25

I call this first set as primary factors because the

1:29

primary factors do impact both the image

1:33

quality and the radiation dose.

1:36

And I consider them because they are

1:39

two side of the coin. If any one side is

1:43

scratched, the coin value will go.

1:45

So therefore, if the radiation dose is too low or too high,

1:50

that can impact the image quality or the patient dose.

1:53

If the image quality is very poor, it impacts the diagnosis for the

1:57

radiologist. So that's why these things play a very

2:01

important role in understanding.

2:03

The second bucket, also called as the secondary factors, are the

2:07

following here, listed here.

2:10

They do have a secondary effect because

2:14

these are post-reconstructed images, impact other images.

2:19

The acquisition is already done.

2:22

So the secondary factor impact the image quality, not the patient

2:26

dose, because the patient dose depends on the primary factors,

2:30

and the secondary factors impact the image quality or

2:34

how the image shows up and so forth.

2:37

The other factors are the third category, which to some

2:41

extent we do not have control, such as the patient size,

2:45

which impact both the patient dose and the image quality.

2:49

The patient motion, again, that impacts the image quality, and if

2:53

it has to be repeated, that impacts the patient dose.

2:56

The efficiency of the detectors. In fact, that has improved a

3:00

lot these days with the new technology.

3:03

The last one is the training and experience.

3:06

Even though this appears differently than the scan parameter,

3:10

I like to group this very important because especially in the

3:14

CT, when we do lot of contrast injection,

3:18

the training and experience of a technologist become very critical

3:22

when to really start the scan, monitoring the bolus

3:25

tracking, and starting the scan. So the training and the experience become very

3:29

important. In addition, how do you position the patient?

3:33

It's very important because that will also impact the image

3:36

quality and the patient dose and so forth.