Your oncologist may be scheduling you for a quarterly PET scan. My quarterly PET scan occurred at the end of my second round of chemo, right in the midst of my transplant qualifying tests, so I’ve included it in this chapter. If you do not normally get these, or are on a different schedule, it will most likely be included in the list of shown on the Pre-Transplant tests and procedures page. Since this test is a commonly repeated one for cancer patients, I will outline it in detail here, and then just refer back to this chapter for repeat tests of the same.
A PET scan is a nuclear medicine imaging technique. Other related imaging systems are CT scans and MRI’s. The PET acronym stands for Positron Emission Tomography. The equipment itself resembles a CT scan (a donut-shaped ring) with a long tube (approximately five feet) attached to it, which is open at the far end. A patient is moved into the tube then slowly withdrawn at four-inch increments every six minutes as a three-dimensional image is taken. Generally a full-body scan is composed of two, thirty-five minute partial scans, one on your upper body (head in first) and the second on your lower body (feet in first). Unlike an MRI, which is very loud when in operation, there is very little noise from the PET equipment while it’s scanning.
There is very little pre-test prep work required for a PET scan. Generally the patient should avoid sugar, caffeine, and strenuous exercise in the 24 hours prior to the test. The patient must fast (no food) for four hours prior to the scan, although they may drink as much water as they like. These guidelines are a generalization and your specific instructions may differ somewhat. Always follow the instructions given by your test site.
Nuclear imaging tests are almost always done in radiation testing centers, and always under out-patient status. Once at the center a temporary IV is prepared and a glucose tracer is injected into your system. This tracer is allowed to disperse itself throughout your vascular system for about 45 minutes before the scan takes place. If your physician has authorized the use of a sedative, it will be administered orally prior to the tracer. Generally the sedative will make you very drowsy. It should be effective for four to eight hours, so you must have someone with you to drive you home if you use this option.
Once the glucose tracer is dispersed the scan takes place. The patient lies on a narrow metal tray which will move into and out of the scanner. The PET scan makes a 3-dimensional image which shows ‘hot spots’ where higher-than-normal levels of the glucose tracer are accumulating. Since damaged and defective cells require a large amount of glucose (sugar) to feed their accelerated growth-rate, these spots may indicate the presence of cancer. However healing injuries also fall into this category, so some hot spots may indicate normal bruising or some other relatively harmless form of tissue damage. To distinguish between these categories the hot spots are given a rating, and anything above a three is considered potentially cancerous.
Technicians administer this test, so you will not receive an analysis on-site. The results will be sent to your oncologist and will be available for review a few days after the test. If one or more hot spots are found, your oncologist may schedule a needle aspiration biopsy to confirm a diagnosis. I had several of these biopsies done in the aftermath of my transplant, and so far all of them have been negative. A biopsy may occur anywhere in the process, and if your disease is cancer, you probably had one or more before that diagnosis was made, completely outside of this transplant process. For those who have not had one, I will include the test in the Post-Transplant Issues page.
This is good place to discuss claustrophobia and its impact on the test. You must remain perfectly still during the scan. Often a foam wedge is placed beneath your knees to reduce lower back strain during the test, and your ankles will be secured together using Velcro™ to keep your feet still. I’ve never experienced claustrophobia from this particular restraint, and in fact for me it’s a good solution all the way around, however that’s not the case with my hands.
Generally the technicians will want to position your arms over your torso with your hands crossed at the wrist for the upper body scan. A Velcro™ wrap around your shoulders and chest holds your arms in place throughout the test. I’ve found that I can endure this restraint when I take the sedative, but not when I don’t. The two times I’ve done the test without a sedative I’ve had to have my hands free and hold them in place myself. You may find this difficult to do, so test it out before they begin the scan.
If you are a big person, you may find the tube to be tight at spots. The donut ring on the machines I’ve used is a little wider than the long tube attached, so that when I move from the ring into the tube, my shoulders are squeezed down to my elbows. The Velcro™ wrap helps minimize this effect, but it may increase your anxiety if you suffer from claustrophobia. The technicians will move you in and out of the tube a few times before they start the test so you can get a sense of how it will feel. Find the points that bother you and ask them for a solution – they’ve no doubt dealt with every such issue in the course of their work.
The tube may not only be tight to your shoulders, but also close to your face. Whether I take the sedative or not, I absolutely never open my eyes during the upper body scan, as I know that will set off an anxiety attack for me. If a scan is interrupted, it will have to be repeated in total, so find and address any issues at the start. Some patients like to have a cloth (dry or damp) over their eyes, but I can’t tolerate this, especially if my hands are bound – it’s just too restrictive for me. I simply must keep my eyes closed, and as long as I have enough distraction material planned for the thirty-five minute test, this has worked well for me.
For the upper body scan you’ll begin all the way inside the tube, and that actually may be a little reassuring for you, since the far end of the tube is open, and you can probably look backwards and out. As they begin the scan your line of sight to this open end will diminish, though, and the closed-in sense will increase. Keeping your eyes closed during the whole thing might be the best choice for you, as it is for me.
My overall strategy for this test is to a) take the sedative, b) let them secure my hands, c) keep my eyes closed, and d) use both relaxation (deep breathing) and distraction (poker and cooking) techniques. Find what works for you and use it!
Depending on your disease, you may receive only an upper or lower body scan, but both are included in the PAGs that follow. The first one is for me without a sedative:
PET Scan – Teri
|
Type
|
Rating
|
Duration
|
Tourniquet
|
Pressure
|
3
|
1-2 min.
|
Insert Needle to vein
|
Sharp Sting
|
2
|
5-10 sec.
|
Inject Glucose Tracer
|
None
|
0
|
30 sec.
|
Wait Time
|
None
|
0
|
45 min.
|
Upper Body Scan
|
Claustrophobia
|
8
|
35 min.
|
Lower Body Scan
|
Claustrophobia
|
5
|
35 min.
|
Based on my PAG, during the three to four-hour test there is a total of approximately 72 minutes of discomfort, almost all of it in the emotional anxiety rather than physical pain category. However this only applies if you are claustrophobic and do not take the sedative offered. If you’re not claustrophobic or if you are and do take a sedative, the rating and/or duration of discomfort may be reduced significantly. If you’re not at all claustrophobic, your discomfort may last no more than two minutes (tourniquet and needle insertion). Also note that the 72 minutes is for a full-body scan. If you’re only having a partial scan, both the discomfort and test time can be reduced by 35 minutes.
Here’s what my PAG looks like when I’ve reduced the issue of claustrophobia by the use of a sedative for relaxation in conjunction with a distraction technique:
PET Scan – Teri
|
Type
|
Rating
|
Duration
|
Tourniquet
|
Pressure
|
3
|
1-2
min.
|
Insert Needle to vein
|
Sharp
Sting
|
2
|
5-10
sec.
|
Inject Glucose Tracer
|
None
|
0
|
30
sec.
|
Wait Time
|
None
|
0
|
45
min.
|
Upper Body Scan
|
Claustrophobia
|
4
|
35
min.
|
Lower Body Scan
|
Claustrophobia
|
2
|
35
min.
|
As you can see I still have 72 minutes of test time listed, but now all of that time is rated at no more than a 4 (a manageable rating for me), while without the sedative 70 of those minutes are at a very high, 8 rating. Please consider all of these factors in filling out your own PAG here:
PET Scan –
|
Type
|
Rating
|
Duration
|
Tourniquet
|
|||
Insert Needle to vein
|
|||
Inject Glucose Tracer
|
|||
Wait Time
|
|||
Upper Body Scan
|
|||
Lower Body Scan
|
Since the tracer used is a nuclear medicine and will leech out of your skin for some hours after the test, you should keep your distance from children for the remainder of the day.
Whew, done! The other test descriptions are generally far shorter!
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