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In the development of cardiac CT, especially with the multi-detector

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CT, which led to the possibility of doing cardiac CT,

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from the beginning, there was a race to acquire the heart as

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fast as possible. The motivation to advancement were

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the goal is two ways. One is to image the entire heart

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in a single gantry rotation.

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One sweep of the gantry, the entire heart could be scanned,

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and that is the methodology taken by developing wide

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detector CT scanners, which I'm going to show you.

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The second method is to image the entire heart in a single

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heartbeat, and this was achieved with high-speed scanning

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using dual-source CT.

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The multi-detector technology from the beginning

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was racing to do this acquiring the heart because imaging

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heart was one of the most challenging for any imaging vendors

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because the heart beats very fast

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in all direction, and you want to freeze the motion of the heart to get an

1:03

image, and that's done in two ways.

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Here's an example of one particular vendor, which they

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continue to develop the number of detectors in a Z direction

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from 64 detector all the way to

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324 detector,

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which means if the patient is positioned and scanned

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the whole volume, if one scan can cover the

1:27

entire heart. The technique was 320-slice

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scanner, of which each of the detectors is about half a millimeter,

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so that leads to 160-millimeter beam width, which will cover

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the entire heart in one rotation.

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This is what happened with one of the vendors, which is heavily used these

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days. The advantage is they have a large scan

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range,

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which will minimize patient motion, not only in cardiac CT for

1:55

doing any other imaging.

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It also requires less contrast. It can reduce

2:01

the overall exam time because you are covering a larger volume.

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And if you want to do a step and shoot scanning, that is usually done with

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minimal overlap. So, this is the advantage of wide-detector CT.

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And one other example of wide-detector CT is advantageous when

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you're scanning a baby or a kid because a

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large volume of the scan can be acquired as fast as

2:25

possible.

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For example, one can acquire the entire heart.

2:31

Volume covers the entire heartbeat, one heartbeat or two

2:35

heartbeat, but you are covering the entire heart

2:39

with one rotation. That now is limited by how fast

2:43

the scanner can be rotated around the gantry, which means

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with the advanced scanner of 0.3 second or 300

2:50

millisecond, you are done with cardiac CT angiography in

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300 milliseconds.

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The second way to acquire the entire heart in one

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heartbeat was done by this particular vendor who developed what is called as the

3:05

dual-source CT. Two CT x-ray tube were placed

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inside the gantry with the detector on adjacent

3:12

side. And now, this particular vendor has

3:16

promoted this pretty exhaustively to acquire the entire

3:20

heart and shown to acquire the entire heart in one heartbeat.

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Even though the detectors are not as large as the other

3:28

vendor, the way to acquire cardiac

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imaging is done by moving the table faster through

3:36

the gantry and acquiring the images around the patient

3:40

as fast as possible, and then the entire heart is

3:44

now covered within one heartbeat.

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One of the advantage with the dual-source is

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it has higher temporal resolution, which means the

3:54

temporal resolution is the amount of time it takes to image a

3:57

heart or an organ. The minimal amount of time

4:01

required to acquire any CT image is one half of the

4:05

gantry rotation,

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which means if there is 300 millisecond or

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390 millisecond, the best temporal resolution you get is

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about 190 millisecond.

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Now, with the dual-source CT, you can go as much as

4:21

quarter of the rotation, which means among all the CTs

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right now, the best temporal resolution is achieved in the

4:28

dual-source CT because it only collects data related

4:32

to only one-quarter of the rotation time.

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And with the dual-source, it acquires so fast when the table is moved

4:41

quite fast, you are acquiring the data in such a way

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all the data of the heart is within this one heartbeat.

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That's how the different

4:51

way to acquire cardiac CT imaging.

4:55

With the volume imaging, the 320-slice

4:58

scanner, you can now acquire an entire heart in a

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very low dose. This is one example showing

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all these subjects were done on a 320 Canon

5:09

scanner

5:11

with 100 kV, and that resulted to an image

5:15

quality effective dose of 1.3 millisievert,

5:19

almost less than the current calcium scoring imaging.

5:23

And this is the type of images you can acquire now with this cenimetric

5:27

rendering of the heart, and you're able to diagnose very

5:31

subtle changes in the heart and with a very short period of time

5:35

available for the scanner.