Central Analytical Facilities
Welkom by Universiteit Stellenbosch

​NII PET-CT Scan Voorbereiding

​​​​​​​​​​​​​​​​​​Please note that our scanner acc​ommodates a maximum participant weight of 185 kg.

Scan participants should please not wear any jewellery and should avoid clothes with large metal buttons or buckles as these might cause image artefacts. Participants should please bring along a warm jersey as the scan room is cold.

Depending on the type of scan performed and exact clinical or research question, special metabolic preparation may be required. In the event that fasting is required, participants may bring along a meal for consumption after the scan (please make sure this is made clear to participants).

Research participants should please follow the preparation instructions provided by their study doctor, according to the relevant study protocol. Some suggested (generic) guidelines for metabolic preparation follow below.​​

F-18 FDG PET/CT general

Applies to scans for infection/inflammation (non-cardiac); malignancy; regional brain metabolism

  • Participants should not consume any food or sugar for 4-6 h prior to the injection of FDG. In practice, this means:

  • Participants scheduled to undergo the PET study in the morning should not eat after midnight and preferably have a light meal (no alcohol) during the evening prior to the PET study. Participants scheduled for an afternoon PET study may have a light breakfast before 08:00.

  • Parenteral nutrition and intravenous fluids containing glucose should be discontinued at least 4 h before the PET/CT examination. In addition, any infusion used to administer intravenous pre-hydration other than normal saline should be avoided.

  • Adequate pre-hydration is important. Advise participants to drink adequate amounts of ordinary (unflavoured, unsweetened) water prior to coming to the centre (unless clinically contraindicated)

  • Participants must avoid (extreme) exercise for 24 h before the study.

  • Medication must be taken as prescribed, unless specifically advised otherwise.

  • Chemotherapy, radiotherapy, surgery, colony-stimulating factor, or immunotherapy may have an effect on FDG uptake patterns. Contact the unit for more information and advice on optimal imaging time points post-therapy.

Diabetic Participants:

Hyperglycaemia and high insulin levels affect FDG uptake patterns and may confound results. Contact the unit for more information and advice.

Type II diabetes mellitus (controlled by oral medication)

         Two options for scheduling these studies should be followed:

    • Schedule in the first morning slot. These participants should not have anything to eat / drink in the morning except plain water, not take any diabetic medication but should bring a sandwich / snack together with their medication with them.

    • Schedule for a 13:00 slot. These participants should have a light breakfast together with all their medication at 06:00 whereafter they should consume nothing but plain water.

Type I diabetes mellitus and insulin-dependent type II diabetes mellitus

Ideally, an attempt should be made to achieve normal glucose values and insulin levels prior to the PET study, in consultation with the participant and their attending medical doctor.

    • If insulin injections are taken in the evenings only, then schedule the study in the first morning slot. These participants should not have anything to eat / drink in the morning except plain water, not take any diabetic medication (including insulin injection), but should bring a sandwich / snack together with their medication (for after the study) with them.

    • If insulin injections are taken in the morning, then schedule patient for a 13:00 slot. These participants should have a light breakfast together with all their medication, including the insulin injection at 06:00 whereafter they should take nothing but plain water.

​​F-18 FDG PET/CT for infection/inflammation (cardiac)

Applies to scans in which the presence or extent of cardiac inflammation or infection; or cardiac device infection, is being assessed.

  • Most important is that participants should undergo an extended fast (minimum of 12 hours fast before FDG injection) during which time patient can only drink plain water.

  • Also the participant should follow a high-fat, high-protein, very-low carbohydrate diet for the three days preceding the study, i.e.


  • ​No bread

  • No pap 

  • No rice

  • No samp 

  • No potatoes

  • No beans 

  • No pasta  

  • No crumbed foods

  • No soft-drinks (Coke, Fanta, Sprite, Stoney, etc.)


  • ​Meat

  • Chicken

  • Eggs

  • Butter

  • Cheese

  • Cabbage

  • Cauliflower

  • Broccoli

  • Spinach (nothing mixed in)

  • Onion

F-18 FDG PET/CT for investigation of hibernating myocardium (cardiac)

Applies to scans in which extent of viable, hibernating myocardium is being assessed.

In addition to the general preparation for an F-18 FDG study (see above), the day before the PET study participants should follow a fat-free diet:

  • No oil or butter

  • No full-cream yoghurt or milk

  • Preferably fish or lean meat

  • Plenty of fruit and vegetables

On the day of the study participant should drink plain water only (nothing to eat)


  • The following COMT-inhibitors (not applicable to brain tumour cases): Tolcapone (Tasmar®) and Entacapone (Comtan®) should be withheld for at least 5 half-lives (>15 hrs in the case of the products named here). This also applies to combination products containing either of these drugs: levodopa/carbidopa/entacapone (Stalevo®), in which case a temporary levodopa/carbidopa combination without entacapone (e.g. Sinemet®, Carbilev®) may be substituted for the required time prior to the study. This should be discussed with the referring doctor.

  • Reserpine (Reserpine®, Brinerdin®): should be withheld for 20 days prior to the investigation (5 half-lives) in consultation with the managing neurologist.

  • The above medications may be resumed as early as 10 hours after carbidopa administration (=5 half-lives).

  • Check patient is not allergic to carbidopa (for patients with movement disorders).

  • There is no need to withhold levodopa/carbidopa combinations (Sinemet®, Carbilev®, Madopar®); amantadine (Symmetrel®); pramipexole (Pexola®); Bromocriptine (Aspen Bromocriptine®, Parlodel®, Ropinirol (Requip®); etc.

  • Participants should fast for at least 4 hours prior to tracer injection. Generally, participants are told not to eat or drink anything (except plain, unflavoured water) from midnight the evening before the study. In cases where imaging is planned in the afternoon (after 13h00) a light meal (low in protein) is permitted before 08h00 on the day of the study, whereafter only plain water may be taken by mouth. These same guidelines are recommended for diabetic patients (with appropriate adjustments to medication scheduling).

  • Participants should be able to lie reasonably still for 10 min


No specific preparation is required. Encourage good hydration.


Because uptake of radiotracer by neuroendocrine tumour cells may be influenced by concurrent therapy with somatostatin analogues (Sandostatin, etc.), it is advisable to time serial PET scans at the same time point after the most recent dose of therapy (e.g. consistently scan serial studies at 4 weeks after the last dose). No other specific preparation is required. Encourage good hydration.​