0:00

That is the uniqueness of the mammography system.

0:03

Now, how is the mammography system itself designed?

0:08

This is a very schematic diagram of a typical mammography

0:12

system,

0:13

and this is taken from one of my publications, and this publication

0:17

will be listed under this lecture at the end.

0:21

This is a typical mammography system, which has an X-ray tube,

0:25

which has an X-ray spectrum. The X-ray tube can be a molybdenum

0:28

target with the molybdenum filter placed inside here,

0:32

and this X-ray spectrum interacts with the breast, which is compressed.

0:36

I'll tell you the reason why it is to be compressed.

0:39

And the X-rays coming out of the patients are now captured by a grid,

0:43

passes through a grid so that extraneous scatter radiation do not

0:47

contribute to the image that's all taken.

0:49

And finally, there is a digital detector.

0:52

It can be a film screen system

0:54

or a digital detector to create an image.

0:58

So there is a challenge here in this one.

1:01

It is uniquely positioned in a way so that this is a

1:05

typical layout of the mammography X-ray tube

1:08

design, and this is where the breast is positioned.

1:12

And if you look in here, we are designing in such a way

1:17

the cathode of this facing, or the element which

1:21

creates electrons, are facing towards the patient,

1:24

and these electrons will hit the target, and the target will

1:28

produce X-rays passing through the filter and so forth.

1:33

Because of the heel effect,

1:35

the intensity of the X-rays is more highest around

1:39

this area, and we want the highest intensity

1:42

X-rays to be hitting the chest wall side

1:46

compared to the nipple side. And that's why this design is set in

1:50

such a way, this is utilizing the maximum way.

1:54

So if you look in here, this is the cathode, which is the filament with the

1:58

anode. The electrons hit the target, creates X-rays

2:02

of high intensity, are in this direction towards the anode.

2:05

There is some of the self-absorption, and this is the intensity

2:09

because of the heel effect. So the heel effect on the

2:13

cathode intensity is greater than the anode intensity.

2:16

Because of that, the X-ray tube cathode is positioned over the chest

2:20

wall.

2:22

This is the front side and the lateral side.

2:26

If you look at the front side, there is a film cassette here, which is the

2:29

reciprocating grid. The grid moving back and forth to

2:33

block off a lot of the scatter when you're taking an image.

2:36

And the typical grid ratio used in

2:39

mammography is 5:1.

2:42

When I say grid ratio, the height of the septa

2:46

versus the distance between the two septa.

2:49

Because the distance between the

2:51

focal spot and the

2:55

detector is small, the reciprocating grid is

2:58

typically 5:1. There is also a

3:02

phototimer detector here.

3:05

The function of the phototimer detector is moment the image

3:09

is begin to take, it will sense in a fraction of a

3:12

millisecond what's the thickness of this particular object

3:16

is, the breast is.

3:18

Based on the thickness of the object, this phototimer will

3:22

reset the X-ray tube to deliver the right

3:26

amount of X-ray dose passing through the object.

3:30

This is the side view. There is also this compression paddle,

3:35

which is one thing which a lot of women going to screen

3:38

mammogram hate because of the compression created.