0:00

The next part is the magnification.

0:04

Let's define the field of view. The field of view is defined

0:08

as the size of the image seen at the image receptor, in

0:12

this case, an image intensifier.

0:14

Here's an X-ray source. This is the actual field of view in

0:18

the patient, but on the image it looks magnified.

0:23

So

0:24

the size of the input phosphor of the I.I.

0:27

will determine the field of view.

0:29

The most common is a nine-inch I.I.

0:32

Also available is the larger 12 to 16-inch I.I.,

0:36

and also smaller 14-inch and 6-inches.

0:39

The actual image diameter in patient is smaller

0:43

than due to geometric magnification.

0:47

This is a large, non-magnified field of view.

0:51

This is a small magnified field of view with six inches in

0:54

diameter.

0:56

You can see so many details in this one.

0:59

Here is basically showing example of I.I.

1:02

image magnifiers, which will reduce minification.

1:06

Less minification.

1:08

Same output phosphor, but the contribution from

1:12

normal tissue was this much.

1:15

Now that is shrinking and this is shrinking.

1:19

There is what is called electronic magnification.

1:22

It reduces the field of view, it reduces the minification,

1:26

and the displayed image is magnified,

1:29

and that's electronic magnification.

1:31

But in general, for a normal operation, here is an

1:35

image field of view, which is the nine-inch I.I.

1:37

size,

1:39

and its output is usually about two to four inches.

1:43

If you reduce the field of view to small,

1:47

but the amount of X-rays required to create the image quality is the

1:51

same.

1:52

The one of the way system does it by increasing the

1:56

radiation dose to the patient, so more X-rays reach this limited

2:00

area.

2:01

That's magnification penalty with respect to AI.

2:05

Whereas in electronic magnification, as in flat panel, it can

2:09

magnify the display image

2:12

and the kind of electronic adjustment to update the

2:15

image brightness.

2:18

This particular slide showing the difference in the magnification mode,

2:22

normal versus magnified. You can see the image magnified

2:26

with much better viewing for the physician.

2:30

The beam automatically collimated to the much smaller imaging area.

2:35

Automatic brightness control will increase the radiation dose.

2:39

Another aspect is the resolution in magnification mode.

2:43

If we magnify the resolution,

2:47

here is a 23 centimeter unmagnified of a tool used

2:51

for spatial resolution.

2:53

Here is 15 centimeter, you can begin to see the object, but here is

2:56

the magnitude. At 11 centimeter, the spatial resolution

3:00

much better, but the radiation dose penalty is quite high.

3:05

So how does it compare it here? For comparison purposes,

3:09

if you require 100 X-ray units, arbitrary units to

3:13

create an image with using a nine-inch I.I.,

3:16

if we magnify to six

3:19

inches,

3:20

the radiation dose will increase by 2.25 times.

3:24

And if the magnification is go to second level,

3:28

the radiation dose will go up almost by nine times.

3:33

This is what I meant is use of smaller field of view in flat panel

3:37

detector so you can automatically magnify to a larger

3:41

point.

3:43

The intense radiation dose flat panel versus image

3:47

intensifier is shown here. With image intensifier,

3:50

usually it goes off as the field of view changes.

3:54

It goes dramatic decrease, whereas in flat panel, it's

3:58

much slower decrease.

4:00

That is captured in the following slide called the dose rate.

4:04

The I.I. fluoro dose rate increases as one over

4:08

field of view squared, which means the field of view will make a lot

4:12

of difference in the radiation dose rate.

4:15

In the flat panel dose rate, it increases only by

4:19

approximately one over the field of view.

4:22

All factors considered, flat panel dose rates are much

4:26

lower

4:27

because it has better efficiency, increased lower depth, a smaller

4:31

field of view, and the equipment configuration.

4:35

Again, this is a busy slide showing different

4:38

fluoro more available on this particular system.