68Ga-PSMA CT Scan Accuracy

[E2-Guy]

Does anyone know how small of a malignant lymph node the 68Ga-PSMA CT scan can Identify?

[Justfor_]

Widespread misconception that drags its origins from usual imaging. PET is not a geometrical instrument. It is an isotope emission detection and ranging one. If enough isotope (68Ga for example) is concentrated into a 1 mm lesion, it will light up. On the other hand, if a lesion of 10 mm won't source enough isotope, it will pass unnoticed.

[E2-Guy in reply to Justfor_]

Thank you!

[GP24]

A node with an average SUV will show up on a PSMA PET/CT with a lower limit of 3 to 4 mm.

[E2-Guy in reply to GP24]

Thank you!

[Justfor_ in reply to GP24]

Tall Allen interviewing Andrei Iagaru, MD Stanford University Hospital, posed almost the same question. Watch the answer he received in min 29:00 of the following video:

youtube.com/watch?v=Kuelxko...(Not working as expected?)

healthunlocked.com/prostate...

This question is akin to inquiring for the size or the weight of an object to keep it afloat. Cork will float, iron will sink, irrespectively of size or weight. It is the specific weight of the object that does the trick.

[GP24 in reply to Justfor_]

I did not intend to imply that your post was wrong. I just wanted to provide a simple rule of thumb.

[Tall_Allen]

5 mm is the usual limit because the CT part of the scan can't discern anything smaller than that. Its sensitivity (ability to detect cancer in LNs if it is really there) is less than 50% when PSA is elevated.

[E2-Guy in reply to Tall_Allen]

Thank you Tall_Allen for your as usual informative reply! I couldn't seem to find the answer on Goggle.

[tango65]

It depends on the expression of PSMA in the cancer cells and the axial resolution of the scanner.

"Axial resolution is the ability to see the two structures that are side by side as separate and distinct when parallel to the beam."

The regular PET machine could detect lesions around 4 mm and bigger if they have a PSMA expression higher than the background.

Digital PET machines have a better axial resolution and could detect smaller lesions.

If the PSMA expression is very high, for example a SUV of 25 it is possible that both types of machine could detect smaller lesions.

[E2-Guy in reply to tango65]

Thank you Bro!

[d3is4me in reply to tango65]

Hi Tango Very interested in your comment"Digital PET could detect smaller lesions"My local Imaging clinic have recently installed a GE OMMNI LEGEND Digital Pet which they claim is the world's best?? I cannot find any info on the smallest lesions it can detect any info on Digital Pet's would be appreciated.

[Hidden]

luv ya Ron Ron!

[E2-Guy in reply to Hidden]

Luv Ya too Bro! I just wanted to know about the accuracy of the scan since I am going to give a little presentation on PCa to our Expats club and what I'm currently doing (using the tE2 gel which has turned out to be a 'wonder' hormone for me). Several years ago when my PSA was well above the .2 recurrence level I ventured down under to Australia for the 68Ga CT scan which identified 8 infected sacral Lymph nodes. My surgeon in CA (who performed my robotic RP 20 years ago) convinced me that we should surgically remove them…I think he needed more practice with his robot! After the surgery and my PSA continued to climb, Tall_Allen stated that he thought the surgery was a waste of time & money since only the larger lymph nodes were identified. As usual, he was right!

[Seasid in reply to E2-Guy]

Interesting. What was your PSA?

[E2-Guy in reply to Seasid]

.006

[j-o-h-n]

Bad, bad Leroy Brown smallest sedan in the world wide Scan.....

j-o-h-n <===<<< Senior management is about to spike my spikes....

Good Luck, Good Health and Good Humor.

j-o-h-n Tuesday 04/04/2023 6:03 PM DST