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Topic: Convert PET raw data to SUV
Replies: 4   Last Post: Jun 11, 2014 10:49 PM

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Luca

Posts: 77
Registered: 6/6/12
Re: Convert PET raw data to SUV
Posted: Jul 23, 2012 7:02 AM
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Siti_Mustaqim <ctsalasiah1950@gmail.com> wrote in message <f8b06982-a10c-41d8-b6da-df8fac5ca27e@googlegroups.com>...
> Hi,
> Does anyone know how can I convert raw PET data (0 to 32767) unit BQML from Siemes PET/CT to Standardized Uptake Value? What is the supposed SUV range in the image?
> I followed this:



What an odd question... Are you confident enough with the topic??
1) Images written in dicom format are usually scaled (each slice independently) between 0 and 32767. This has nothing to do with PET raw data. It's dicom!
Using the coefficient provided in the dicom header you can scale the sliced to activity values. In the units specified in another header field. (kBq/cc, MBq/cc, uCi/cc etc...)

2) Once you have activity values you can apply one of the various definitions of SUV.


> actualActivity=tracerAct*(exp(-ellapsedTime*log(2)/halfLife));
> atualActivity=actualActivity*metadata.DecayFactor;
> suvFactor=WEIGHT*1000/actualActivity;
> SUV=PETraw*suvFactor;


You don't specify what are those variables. If I interpret correctly what you're doing it seems at least extremely odd to compute the decays of the injected activity (first line) and then multiply it again by a "DecayFactor".
Looks like your correcting twice for the activity decay. To which istant does your scanner decay-corrects the activity values? At which time is your dose calibrated? When was the patient injected?
When you know all this... Perform the proper decay corrections!
Then suvFactor defined as WEIGHT*1000/actualActivity may be correct. But it's just one of the possible definitions.

> And my SUV image is within [0,10.7633]. Is this correct?

It's sensible. The mean value across the whole the body should be a bit less than 1. With high uptake organ/lesion taking high values (i.e.: I've seen peak values up to 15 for some very high activity lesions)

> Thanks for any response. I really appreaciate it.

Then again... Read this paper:
"John W. Keyes, Jr.
SUV: Standard Uptake or Silly Useless Value?
J Nucl Med 1995 36:1836-1839"

SUV is meaningless and confounding, whatever the physicians might think of it!!! EVEN IF one could correct for all the errors introduced by the scanner and the reconstruction.



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