Can PSMA and bone scan be done close together?

[EvFC]

Hello, does anyone know if there are issues with doing a bone scan and a PSMA scan within a day or two of each other? I know both use radiation, so I don’t know if any radiation remaining in the body would impact the other scan. Thank you!

ETA: just want to add a bit more context on this. My husband’s GP ordered a bone scan a week and a half ago, because of lower back pain. Yesterday we asked the surgeon oncologist (who we talked to for the first time) if he would sign off on a requisition for a private PSMA scan - he did. We want to get the PSMA scan done as soon as possible, so likely the upcoming week or early the following. We didn’t plan on both of these scans, but that’s where we are at. My husband wants to move forward with the bone scan still, because he thinks it might help rule out any possible false positives.

[Seasid]

I had first day a psma pet scan and the next day the nuclear medicine bone scan.

Some clinical trial patients of professor Emmett have both scans a same day.

The psma pet scan is a gallium 68 scan. I am not a doctor and I don't know if it is important or not.

[EvFC in reply to Seasid]

Thank you for sharing your experience. We are going to call the lab who does the PSMA on Monday, just to be sure.

[addicted2cycling in reply to EvFC]

Seasid wrote -- " ... The psma pet scan is a gallium 68 scan. I am not a doctor and I don't know if it is important or not ... "

My PSMA PET/CT scan a couple of months ago was the currently widely used PYLARIFY and not GA68.

pylarify.com/

[Justfor_]

In theory, less interaction, for a given time in between, will be achieved if PSMA is taken first. This because the half-life of the isotope used for PSMA is shorter, In practice scheduling reality can be on a totaly different basis. Bone scan, aka scintigraphy, uses a radiopharmaceutical readily available, so it can be done during any working hour. That of PSMA, shall be prepared and consumed within hours, consequently, labs group two to three tests on a fixed day (or mostly two days if there is high demand) of the week and stagger them within hours from one another. You will soon find out how things are set in your case. Best of luck.

[Xavier10]

often they do a CT scan at the same time. maybe that could take the place of the bone scan?

[spencoid2]

the radioactive tracers used in both PSMA scans and bone scans have short half lives. the one for the PSMA scan is 68 minutes and the bone scan is 6 hours so it probably makes sense to do the PSMA scan first if the two are to be followed closely. either way if they are two days apart i (not a radiologist) do not see a problem. Also each scan compares the uptake of the tracer to the background. As far as I can figure (not a radiologist) if both are looking for cancer i do not see a huge problem if one influences the other.

Are you having the PSMA first? If you have a choice that makes more sense to me?

[Retireddoc]

False positives with PSMA PET do occur but are relatively uncommon. Bone scan is very unlikely to be of any help in these cases because bone scans are actually less specific than PET and the radio tracer used in bone scans will be positive at any location/foci where there is active bone remodeling/osteoclastic activity. Bone scans are non specific; that is they will be positive at sites of tumor but also benign lesions, areas of trauma/old fractures, arthritis etc. PSMA PET scans are more specific and are more sensitive and that is why they have replaced bone scans in evaluation of metastatic prostate cancer.

The only downside is PET scans are more expensive.

It is not an issue having the tests several days apart.

In response to a comment also posted on this tread, PET always include a non contrasted CT at the same time to be used for reference and an aid in the interpretation.

[TeleGuy]

The answer is "yes."

While on a clinical trial, I regularly had a bone scan and PET scan the same day, but in that order. When they finished with the bone scan, they injected me with the FDG PET tracer. They said that the gamma camera for the bone scan would be confused by the energy from the PET tracer, but the PET scanner is selective for the energy level of the 18F emissions and doesn't see the emissions from the 99mTc used in the bone scan.. The scans worked just fine.

I think that bone scans are kind of Stone Age technology compared to PET scans and pretty redundant, but that's what the trial required.

[Jancapper in reply to TeleGuy]

Yes you are correct. Planner bone scans use older technology. Traditional bone scans use the radionuclide Tc99m, which has a 140 Kev characteristic X-ray and has a six hour half-life. These just “shoot” out in all directions with equal probability. The scanning camera uses only a single head to capture and construct the image. These images are of low quality. On the contrary, PET imaging with ether F-18 or Ga68, which are both positron emitters, use a newer technology. Positrons are highly energetic positively charged electrons. When they are emitted, they travel a very short distance and combine with an electron and annihilate. When this happens, two 511 Kev photons are released at exactly 180 degrees. So the PET camera uses this physical characteristic to its advantage. By employing two cameras, one on top and one on bottom, which then circle around the patient. PET images have superior resolution because the background noise is eliminated. The imaging software only registers a count or photon when a photon strikes both the top and bottom camera heads at precisely the same instant of time. So in theory, you could run a planner bone scan at the same time as a PET scan without crosstalk between the two scans.

[EvFC in reply to Jancapper]

Thank you! Is there any value with the bone scan providing an explanation for the back pain if it’s not mets? Or would an MRI be needed for this?

[Jancapper in reply to EvFC]

I can not comment due to lack of necessary knowledge. In general, all nuclear medicine scans can detect physiological abnormalities sooner than pure image modalities because they rely on molecular data.

[Justfor_ in reply to Jancapper]

Sorry to intrude into your otherwise correct description, but the PET scanner doesn't use any cameras at all. It comprises of a large number of detector modules arranged in the radial and longitudinal sense with reference to the bore axis, i.e. in a cylindrical ring topology.

https://radiologykey.com/basics-of-pet-scanning/

[tsim]

Yes, the half lives of both of the radiotracers are very short.

[SilverSeppi]

I see no need for a bone scan; the accuracy of a PSMA PET scan is much higher and has the same purpose.