PET scanners -- SNR versus NECR....

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In summary, the conversation discusses the differences between 2D and 3D PET scanners in terms of SNR and NECR. While 2D PET scanners have a higher SNR due to the presence of septa between detector rings, 3D PET scanners have a higher NECR, which is linearly proportional to SNR. The speaker also clarifies that SNR and NECR are not exactly the same, but are related in a linear manner. There is some confusion regarding these terms, but the speaker has discussed this with their lecturer who confirmed that PET has a higher SNR and NECR.
  • #1
BobP
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In PET, 2D PET scanners have a superior SNR to 3D PET scanners as the influence of scatter and random events is lowered by the septa between detector rings. However, the NECR (noise-equivalent count rate), which is linearly proportional to SNR, is higher in 3D PET scanners. These two facts seem to contradict each other and I am therefore slightly confused.

Please can someone clarify the situation for me
 
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  • #2
BobP said:
...the NECR (noise-equivalent count rate), which is linearly proportional to SNR...
Shouldn't that be '...inversely proportional to SNR...' ?
 
  • #3
Tom.G said:
Shouldn't that be '...inversely proportional to SNR...' ?
Not according to my lecturer...
 
  • #4
BobP said:
However, the NECR (noise-equivalent count rate), which is linearly proportional to SNR, is higher in 3D PET scanners. These two facts seem to contradict each other and I am therefore slightly confused.

That sounds similar to Noise-Equivalent Temperature. Is NECR the number of signal counts needed to match the internal noise of the sensors?
 
  • #5
Drakkith said:
That sounds similar to Noise-Equivalent Temperature. Is NECR the number of signal counts needed to match the internal noise of the sensors?
The NEC is the true count rate of a theoretical image without any scatter or random events which would give the same statistical quality image as a real image which includes scatter and randoms.
 
  • #6
Okay. So it seems to me that the NECR for 3D PET is higher than that of 2D PET because the 3D PET real images are noisier and require more integration time to reach the same SNR as a 2D PET image.

In other words:

Real 2D PET
Signal: 100
Noise: 20
SNR: 5

Ideal 2D PET
Signal: 50
Noise: 10
SNR: 5
NECR: 50

Real 3D PET
Signal: 200
Noise: 40
SNR: 5

Ideal 3D PET
Signal: 100
Noise: 20
SNR: 5
NECR: 100I hope my terminology is okay, I'm used to talking about digital camera sensors and images, not PET sensors.
 
  • #7
Drakkith said:
Okay. So it seems to me that the NECR for 3D PET is higher than that of 2D PET because the 3D PET real images are noisier and require more integration time to reach the same SNR as a 2D PET image.

In other words:

Real 2D PET
Signal: 100
Noise: 20
SNR: 5

Ideal 2D PET
Signal: 50
Noise: 10
SNR: 5
NECR: 50

Real 3D PET
Signal: 200
Noise: 40
SNR: 5

Ideal 3D PET
Signal: 100
Noise: 20
SNR: 5
NECR: 100I hope my terminology is okay, I'm used to talking about digital camera sensors and images, not PET sensors.
Well my lecturer said that SNR is basically the same as NECR. So it have a lower SNR and a higher NECR :)
 
  • #8
BobP said:
Well my lecturer said that SNR is basically the same as NECR. So it have a lower SNR and a higher NECR :)

They certainly aren't the same, but you'll probably need to talk to your lecturer about this. Right now I'm mostly guessing at what all this means.
 
  • #9
Ref post #2
Tom.G said:
Shouldn't that be '...inversely proportional to SNR...' ?
Ref post #3
BobP said:
Not according to my lecturer...
Ref post #7
BobP said:
Well my lecturer said that SNR is basically the same as NECR. So it have a lower SNR and a higher NECR :)

Posts #3 and #7 seem to conflict with each other. Please clarify.
 
  • #10
Tom.G said:
Ref post #2

Posts #3 and #7 seem to conflict with each other. Please clarify.
Sorry. When I say "basically the same" I mean a high SNR = high NECR...
so they are linearly related...but I clarified this issue with my lecturer..

He said PET has a higher SNR and a higher NECR :)
 

FAQ: PET scanners -- SNR versus NECR....

1. What is a PET scanner and how does it work?

A PET (Positron Emission Tomography) scanner is a medical imaging device used to produce detailed images of the body's metabolic and biochemical processes. It works by detecting the gamma rays produced by a radioactive substance injected into the body, which is absorbed by tissues and organs at different rates depending on their level of metabolic activity.

2. What is SNR and why is it important in PET scanners?

SNR (Signal-to-Noise Ratio) is a measure of the strength of the PET scanner's signal compared to the background noise. In PET imaging, a higher SNR indicates a more accurate and reliable image, as it reduces the impact of noise on the image quality.

3. What is NECR and how does it differ from SNR?

NECR (Noise-Equivalent Count Rate) is a measure of the scanner's ability to acquire and process valid data while minimizing the impact of noise. It takes into account both the signal strength and the noise level, and is used to evaluate the scanner's performance in dynamic imaging studies.

4. Why is there a trade-off between SNR and NECR in PET scanners?

As the SNR increases, the NECR decreases, and vice versa. This is because increasing the signal strength often leads to an increase in noise levels, and vice versa. Therefore, there is a trade-off between the two, and a balance must be struck to optimize the scanner's performance for different types of imaging studies.

5. How can SNR and NECR be improved in PET scanners?

There are several ways to improve SNR and NECR in PET scanners, including increasing the amount of radioactive substance injected, optimizing data acquisition and image reconstruction algorithms, and using advanced detector technology. Additionally, proper calibration and maintenance of the scanner can also help improve these performance measures.

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