Doctor insights on:
Reasons For A False Positive Pet Scan
Following cancer surgery I had 2 clear pet scans. Now after 5 yrs the pet scan is abnormal. What can be the reason, what to do?
Abnormal PET....: It is difficult to say without knowing your exact history. What type of cancer was it? Was the pet performed at the same institution and interpreted by the same person? Abnormal pet could mean recurrence but without the report it is difficult to say. There are many causes of false positive on pet. Please look further into this calmly and discuss with your doctor to understand the details. ...Read more
Pet scans most often use a radioactive form of glucose, the energy source for most of the cells in our bodies. The pet scanner can detect and measure how much of the radioactive glucose analog, f-18 fdg, is in a particular organ or region. The areas using more glucose are hyper metabolic and generally more worrisome. Our brains and sometimes hearts prefer glucose as food, making ...Read more
Is it possible to get a false positive herpes culture test? How often does it occur? What is the reasoning for it?
Rarely if ever: False positive results are very unlikely for HSV culture. If the test was actually a DNA test (PCR test), there is a slightly higher chance of false pos, but still very unlikely. If you have had a positive culture or PCR, for sure you have herpes at whatever site was tested (genital, oral). But if a blood antibody test, not culture or PCR, false positive results are quite common. Good luck. ...Read more
If an ovarian cyst gave a false positive last yr and I've taken 3 tests last week and all r pos, could a cyst be the reason why again?
Preg test: I assume you are referring to a positive pregnancy test. If 3 tests report positive results then you need to see a doctor and determine if you are pregnant. Do not assume it is due to a cyst. If you are sexually active at all it could be a pregnancy. ...Read more
Hi, my boyfriend tested positive for oxazepam but has never taken it in his life. Could a sleep aid or even tramodol be a reason for a false positive?
False positives: Are very common when it comes to drug screening. Gas chromatography and mass spectrometry, however, don't lie. Ask to have the sample sent for definitive testing. ...Read more
Why is HIV PCR used to test blood at blood banks, babies and acute HIV symps but not as a diagnosis? Other than cost and false positive what could be the reason that some docs don't trust it? Thanks
PCR is a. .: ..complex test, & more technically difficult to perform accurately than the antibody tests. Because PCR detects viral-RNA (proteins within the HIV virus) it is positive early in the course of infection & is used to try to confirm/exclude HIV as a diagnosis for a set of symptoms. You are correct that there are more false positives with PCR than with antibody tests. Antibody tests are gold standard ...Read more
Which is better, pet scan or cisternogram? Father already had a cisternogram results borderline positive. Should pet scan be done or repeat cisterno
Thyroid from 4cm to 7.1cm. Uptake 20.5%/34%. Fnb significant # multinucleated giant cells with positive pet scan prior to surgery 4 breast ca surgery?
Goiter: A goiter, size increased from 4 cm to 7.1 cm? Suspicious needle biopsy and positive pet scan? Possible breast cancer? You need consult with surgery and endocrinology. More information is needed, but likely you will benefit from thyroid surgery. The pathology exam will make diagnosis, and cancer is a concern. This is complicated, so take a friend with you for your consult. ...Read more
What is the question:
Currently pet scans are widely use for evaluation of glucose metabolism in the body.
In oncology, is use to for initial metabolic characterization of tumors, metastases as well as for treatment response and surveillance. In cardiology, pet scans are use to assess heart ischemia and viability and in neurology the study is use to evaluate cognitive disorders, epilepsy and brain tumors ...Read more
Positron Emission: These studies are done by injecting a special "dye" that is attached to a specific molecule. Most of the pet today is done using FDG (a glucose/sugar look-a-like molecule). Wherever this molecule is used/concentrated, the pet scan is brighter. Hence, tumors/infections (which use a lot of energy/sugar/fdg) are bright on such studies. More: http://en. Wikipedia. Org/wiki/positron_emission_tomography. ...Read more
Probably: I would not recommend a child or pregnant woman be the companion. The amount of radiation dose is minimal to caretaker as long as has usual distance of 3.5 feet from patient. Study involves injection of isotope and sitting in quiet room for about 45 minutes. Then pet ct scan performed possibly for another half hour. Typical dose would be about 0.13 msv. Round-trip flight from new york to tokyo 0.13msv. ...Read more
Depends: Depends on what you are looking for. PET scan usually uses a glucose based tracer to evaluate metabolic activity which can be increased in tumors. All modalities have a certain rate of false positives and negatives. Sometimes multiple modalities can each give you different information to obtain a complete evaluation. ...Read more
Physiology of lesion: Pet scans most often use a radioactive form of glucose, the energy source for most of the cells in our bodies. The pet scanner can detect and measure how much of the radioactive glucose analog, f-18 fdg, is in a particular organ or region. The areas using more glucose are hyper metabolic and generally more worrisome. Our brains and sometimes hearts prefer glucose as food, making it hard to see. ...Read more
Depends: Radiation received from pet ct is relatively high compared to other imaging tests. Pet ct is mainly used for demonstrating metastatic disease, making decisions about effect of therapy, and looking for recurrence. Pet ct has helped prolong life because it can detect small lesions not seen by other tests. Wise decision should be made judging radiation risk versus positive benefit to the patient. ...Read more
Anatomy vs Physiolog:
Mri and ct look at the structure of the body, the anatomy, and the way diseases change or distort it.
Pet looks at the physiology, or how the body uses, or metabolizes something. For pet, the most common metabolism pathway looked at is how glucose is used. A low dose ct is often acquired at the same time as the pet (as in pet/ct scan), to correlate the pet findings with the ct anatomy. ...Read more
Fluorine 18: F18.Get a more detailed answer ›
No..: Not known to....Get a more detailed answer ›
Why PET?: Pet very valuable study to assess metabolic dysfnctn areas in brain due to many causes, and now we can inject newer chemicals to assess both alzheimer's and parkinson's, but really rather un-necessary and expensive test for stroke, as visualization readily available on an mri. ...Read more
Takes up tracer: Pet scans work by imaging a tracer that is a sugar analogue. Since tissue/cells that are more "metabolically active" take up more glucose tracer, we refer to that as "hypermetabolic". Diagnostically, this can mean a number of things and depends on the context. Inflammatory cells and malignant cells (cancer) are typically hypermetabolic. One would have to look at the context and medical history. ...Read more
GoBackToThePetBox: At your age the thymus is considered a residual organ, kind of like your appendix. Now, there are some theories as to its function later in life (an immune function or whatever), but overall it just sits there. Of course, it's made of living tissue so there will be some"activity"in it & rarely, can develop a tumor or infection. But in your case who knows? The people who ordered the test in the first place ...Read more
PET SCAN/OTHER SCAN: It depends on what you are looking for. So that reason is left to your physician, and he/she will order which test is suitable for your condition and what they are looking for. ...Read more
Discuss with doctor.: It is best to discuss your pet scan results with your physician so that you can be sure that you have a detailed and correct understanding of the scenario. If you have any specific questions, be sure to have them clarified. Without the results, it is difficult to answer your question. Hope this helps. ...Read more
Low Risk - Headache:
Florbetapir f18 (trade name amyvid) is a new pet imaging agent that helps to diagnose alzheimer's disease.
From the clinical trials, side effects (also called adverse reactions) were quite unusual, with no serious ones. The most common side effect was headache, occurring in 1.8% of the patients. Next was musculoskeletal pain (0.8%), followed by nausea and fatigue (each at 0.6%). ...Read more
Usually necrosis: PET scan uses F18 FDG (a glucose metabolite) to localize active metabolic processes such as tumors. The uptake of the radiopharmaceutical is considered hot when increased over normal tissues or background Sometimes central portion of tumor is photogenic or cold reflecting necrosis or death of some of tumor. Necrosis can be related to chemotherapy or on presentation when tumor outgrows blood supply ...Read more
Low risk: PET scans are low risk. There is a very small potential risk of an allergic reaction to the radioactive tracer that is used in the scan. The PET scans can show metabolic function in a way that other scans can not. They are often done before chemo so that after chemo they can track the progress of the treatment. ...Read more
If advise yes: You doctor is observing for recurrence at a focused area. Speak to your doctor for explanation and the reason ...Read more
No: F-18 has a half life of 110 minutes. Dose to the patient and those nearby exponentially decreases with time and will still be detectable by Geiger coming out of the patient for about 18 hours. Dose to people around the patient will be very low (difficult to calculate without TLD) measurements but likely well under 0.1 mSv) and can be further decreased by limiting time and increase in distance. ...Read more