Here is the list of few questions asked by patients / relatives going for FDG PET-CT and few instructions given by PET-CT centers to the patients.
Why appointment is required for PET-CT scan?
PET-CT scan is done on basis of availability of radio-isotope such as FDG, PSMA or DOTA. These radio-isotopes have their half lives, so these can not be stored or preserved. Most of the the diagnostic centers or hospitals have to order these radio-isotopes from outside. So depending upon the number of patients they order the quantity of radio-isotopes.
Why only limited PET-CT scan can be done per day?
The diagnostic centers or hospitals have to take permission from AERB to operate the PET-CT scan. AERB is the government run body which gives license to operate any department which uses ionizing radiation, which includes X-ray, CT scan, PET-CT etc. According to the license the diagnostic centers or hospitals have access to limited quantity of FDG which could be either 500 mCi (millicurie) or 1000 mCi (=1 curie) per week. So they can not use more than this in a single week. So for even distribution of number of patients per week only limited numbers of patients are done per day.
What is the meaning of Whole body PET-CT scan?
According to the International standards, whole body PET-CT means scan from head to mid thigh. In cases of sarcoma scan from head to toe is performed. In cases of any primary cancer in finger, hand, foot or toe scans from head to toe are also performed.
My doctor has asked for PET-MR fusion. What does it mean?
Generally, in case of head and neck malignancy, e.g. tongue cancer, buccal mucosa cancer, palate cancer, PET-CT and MRI of neck is done on separate machines. After completion of both the scans fusion of PET image and MRI image is done on special software and it is called PET-MR fusion. It helps in better assessment of anatomy on MRI and disease activity on PET images.
Sometimes in case of brain pathology, like Parkinson’s disease, Alzheimer’s disease and epilepsy, PET-MR fusion is done.
Blood tests required before FDG PET scan?
Two blood tests are required before going for PET-CT scan. One is Blood sugar level and recent S. creatinine level (not later than 7-10 days). If blood sugar level is normal, then FDG can be injected and if S. creatinine level is normal, then intravenous contrast of CT scan can be injected.
If any report is abnormal, then patient has to contact either diagnostic center or his doctor for further instruction.
Any other investigations / reports required before PET scan?
If possible, patient should bring reports, films and CD of previous CT scan, MRI, PET-CT, X-ray, Sonography & Mammography or any other relevant previous investigations.
The following are few other documents that patient should bring while PET-CT scan.
- Recent and past blood reports including tumor markers
- Recent and past Biopsy reports
- All previous surgical / operative details
- All previous documents regarding patient’s medical history
Why old PET scans or any other scans are required?
Previous PET-CT scans or any other scans are required for comparison of disease. It will help to evaluate the changes in patient’s disease process, whether it has regressed or increase after any treatment.
Preparations before PET-CT scan.
Instructions to follow:
24 hours prior to appointment:
- Avoid carbohydrate and / or sugar containing foods; i.e. soft drinks, fruit juices, chocolates, cakes, pastry, ice-cream, desserts, cereal, potatoes, pasta, rice, soy products, flavored yoghurt, alcoholic beverages.
- Avoid strenuous exercise, caffeine or tobacco products.
- Have protein-rich diet and adequate amount of water to stay hydrated.
6-8 hours prior to appointment:
- Nil by mouth after midnight, except water.
- No tea, coffee or any other liquid should be taken.
- Essential medicines may be taken with water.
- Dose of insulin should be withheld prior to the scan, after having proper consultation with your treating doctor.
If patient is allergic to any medicines and / or he has got reactions during previous PET-CT, CT scan or MRI, then he should inform the PET-CT centre in advance, so the necessary arrangements can be done to avoid any reaction during present scan.
Instruction for female patients in reproductive age group.
Female patients in reproductive age group should confirm that whether they are pregnant or not. If the patient is not sure about her pregnancy, then UPT (urine pregnancy test) can be done before injecting the radio-isotope.
Instruction for lactating mothers.
It is recommended that the mother’s breast milk is stored before injecting the radio-isotope to feed the baby after the scan. Breast milk should be discarded for the first 2 hours after scanning. After 12-14 hours, direct breastfeeding can be done.
Any special requirement for clothes during winter?
During winter patient should wear long sleeve warm clothes to avoid brown fat activation, which interfere with evaluation of disease process in that particular area.
If possible, please make sure to remove all the ornaments.
Any accompanying person?
Any patient must be accompanied by an adult, who can give consent on behalf of patient. If patient has any serious complication during or after scan and he / she is not able to give any consent, then the accompanying person can give consent for shifting of patient to any critical care unit or any hospital.
If patient is admitted in any hospital then accompanying brother or sister should be there.
What is expected procedure time? Why?
The expected procedure time is approximately 3-4 hours.
When patient comes for PET-CT, his / her height and weight are recorded. Patient’s fresh blood sugar level is checked and if it is normal, then only FDG is injected. If patient’s blood sugar level is high then according to the sugar level short acting insulin injection is given after having consultation with his / her treating doctor. After insulin injection, at regular interval blood sugar levels are checked and if comes down within normal limits, then FDG is injected.
After FDG injection, patient becomes source of radiation and he / she is asked to rest in separate room so that FDG is evenly distributed in entire body. Patient is asked not to do any physical activity, otherwise FDG would be more concentrated, where there is more muscular activity and it would be less available for cancer site.
How patient will undergo PET-CT scan?
Patient has to lie down on PET-CT scanner quietly. He / she will be asked to breath-hold for few seconds during the scan for proper image acquisition. During scan intravenous contrast is also injected and after injection of contrast, patient may feel little bit warm.
Is the same scanning protocol applied to each and every patient who have different type of cancers?
Separate PET-CT protocols are used for different type of cancer. For example there will be different protocols for tongue cancer, lung caner, liver cancer or intestinal cancer.
If patient is child or mentally retarded, then how scan will be performed?
In such type of patients, if he / she can not lie down quiet for some time, then small dose of sedation would be required to perform the scan. Sedation is given by qualified anesthetists.
If patient has some reaction during or after scan, then what will happen?
If patient experiences any reaction, then stand by anesthetist will give the emergency treatment according to the symptoms of the patient.
Instructions after PET-CT
Once the PET-CT is complete, patient is asked to take more liquid for a day, which will help to excrete residual FDG more quickly from the body.
Patient is asked to flush twice after using the washroom for 24 hours after completion of the scan.
Patient has to make distance from children and pregnant lady for next 24 hours after the scan.
To know indications of PET-CT, kindly click here.
To know more about FDG, FDG uptake and SUVmax, kindly click here.