0:00

Now for colonic distension, we had switched to, um,

0:04

using carbon dioxide, um, many, many years ago, over,

0:09

I would say 10 years ago.

0:11

Uh, and have had great success, uh,

0:13

using an electronic method.

0:15

This is, uh, displayed here.

0:18

Why use carbon dioxide is

0:20

because it has high liquid solubility,

0:22

high partial pressure gradient.

0:24

Uh, so what that means is that there's actual resorption

0:27

of CO two across the, um, colonic mucosa.

0:32

And after the exam is over, um, there's resorption, uh,

0:37

of the CO two making the,

0:39

the exam much more comfortable for patients.

0:41

And this has been, um, demonstrated in, uh, trials.

0:45

Um, so what I have demonstrated here is the

0:48

mechanical device.

0:50

Uh, this is a consumable tubing that's used.

0:53

Uh, there's a balloon at the end that can be inflated.

0:56

This is a fluid catch, uh,

0:58

particularly important if you're performing tagging,

1:01

uh, which is recommended.

1:02

Uh, and then a one-way filter.

1:05

And, uh, this is the end of the chip that goes into the, uh,

1:09

electronic insufflator.

1:11

And it senses, uh, pressure in the, uh, rectal bolt

1:17

for image acquisition.

1:18

According to guidelines,

1:19

what's recommended is at least a 16 slice, multi detector CT

1:24

for your tube settings, either 25 up to 50 AS

1:28

or you can use auto MA KVP.

1:30

Most sites use the one 20 KVP, um,

1:34

for a lower dose.

1:36

You can, and it has been shown to be effective.

1:38

Uh, in published trials, you can decrease to a hundred kvp

1:43

slice thickness of 1.25 of young leaders.

1:47

Um, what's required is scanning in two opposing positions,

1:50

and typically this is in the sup line of prone acquisitions.

1:54

In patients with a large BMI, you can perform, uh, right

1:59

and left lateral decubitus as an option.

2:02

After performing, uh, supline

2:04

and prone acquisitions, if you do not have sufficient, uh,

2:08

insufflation or adequate, um,

2:11

cleansing in a particular area, you can perform focused,

2:14

limited, uh, decubitus view, um, of the particular segment.

2:18

Typically, this will be, uh, in the sigmoid area.

2:23

Remember to acquire your skin and exploration. Um, why?

2:27

Because this will allow for the diaphragms to move up

2:31

and it increases the body cavity size

2:33

so you have more adequate, um, distension of the colon.

2:39

What about radiation?

2:41

And just to put this in perspective, um, you can see

2:44

that the average annual natural background dose that you

2:47

and I receive just walking on this earth is at

2:51

three milli secrets.

2:52

If you live in an area at a higher altitude, uh,

2:56

the average background dose is at 12 milli

2:58

Secrets. Uh,

2:59

and so you do get higher dose, uh,

3:02

when you live in a higher altitude.

3:04

For CT colonography,

3:06

we have actually achieved very low dose,

3:08

and you can see that, um,

3:09

what I have listed here is pulled right off

3:11

of our CT scanner

3:13

and the dose length product, um, including Supline Pro,

3:18

um, series, is that about 200, um, uh,

3:22

milli grace per sonometer.

3:24

When you multiply it by the con conversion factor

3:26

for estimated dose, this is an equivalent

3:29

of about three milli.

3:31

So using this type of a protocol that I delineate

3:36

to you on the prior slide, we can achieve a very low dose

3:41

that's equivalent to the annual, uh, background dose.

3:44

Um, the health physics society has put out this statement,

3:47

which is below 50 to a hundred milli.

3:50

The risk of health effects are either too small

3:52

to be observed or actually non-existent.

3:55

And so we are orders of magnitude below that.

3:58

And so there, um, there's no clear risk.

4:02

This was a study, uh, performed looking at the, um,

4:06

benefit risk, uh, ratio.

4:08

And so they looked at the estimated, um, colorectal cancers

4:12

that are prevented from performing screening CTC every five

4:16

years versus the estimated

4:19

radiation induced cancers from performing screening

4:22

CTC every five years.

4:24

And they found that there was a very high benefit, um,

4:28

to risk ratio at 24, uh, to 35 to one.

4:32

So meant that there was clear higher benefit, um,

4:36

in detecting many more, um, uh, cancers

4:39

that could be prevented, uh, than actually causing, uh,

4:42

radiation induced, uh,

4:43

cancers from the CTC c every five years.

4:48

This is what we wanna see as a well distended, uh, colon.

4:52

Um, uh, for the CT C on the S scouts,

4:55

you should train your technologist to look for this.

4:57

In particular, you wanna make sure that your rectal sigmoid,

5:00

um, is well distended

5:02

because, uh,

5:03

most colorectal cancers occur in the rectal sigmoid.

5:06

Uh, so again, make sure that, uh,

5:09

your technologists are trained, uh, to, uh, in particular,

5:14

uh, assure they can have adequate distension.

5:16

Um, in this area, there are two methods for interpretation,

5:21

primary two D interpretation,

5:22

and this is what's demonstrated here.

5:24

We have a large display, your axial, supine,

5:28

and prone images, um,

5:30

and, uh, you vigorously would scroll from the rectum, uh,

5:35

all the way to the cecum using colon tracking.

5:39

Um, if you find something suspicious on the two D views,

5:42

you'll put an arrow

5:44

or, um, some, uh, indication that we found something.

5:48

This arrow should then translate automatically, uh,

5:51

to see

5:57

Q uh, and, uh, there's a nice, uh, donated polyp

6:01

that's demonstrated on the pro view.

6:04

Uh, this particular software also allows you

6:06

to automatically measure the, uh, volume of the lesion,

6:11

the maximum diameter, and then the distance from the rectum.

6:15

And all of these can be easily, uh, imported into a, uh,

6:19

radiology report.

6:22

Here's another patient. And you can see on the supline

6:25

there's a homogeneous soft tissue, uh,

6:28

spherical type lesion, uh, located along the posterior wall

6:32

of the segments of the sigmoid.

6:34

Uh, in the opposing view, uh,

6:36

we have found a similar appearance, um, for this lesion.

6:40

Uh, and this was a nice demonstration of a large, uh, cile,

6:45

uh, polyp that you can see also on the, um,

6:48

sub volume Q view, uh, right below.

6:54

And again, uh, this software easily allows you to measure

6:58

maximum volume, the diameter,

7:01

and then the distance, uh, from the rectum.

7:06

There's primary three D interpretation

7:08

where you basically use your fly-through

7:11

as your primary view to find lesions.

7:15

Um, and here we have found, uh,

7:18

immediately a very large donated polyp.

7:22

Um, you can put a cursor on it

7:24

or an arrow, it automatically translates into your two dus.

7:28

Uh, and you can see this on both the sagittal.

7:31

Here's the coronal and here's the axial.

7:35

Um, and again, uh, software allows you

7:38

to easily measure this, uh, automatically.

7:42

Here's a different platform, uh, that has the FLA

7:46

or the dissection view on top.

7:48

This patient has a large, uh, sigmoid carcinoma, uh,

7:53

with several large polyps as well.

7:55

Um, you can see that there is some distortion

7:58

of the lesions on the flatt dissection.