Question to Ask Before Injection of 18F-FDG

Questions about…Relevance
 Current glucose  levelScanning is contraindicated when blood glucose is >150–200 mg/dL. Facility reschedules scan in most cases (1) or may apply wait-period protocol.
 Usual glucose levelIf blood glucose is higher or lower than usual for individual patient, physician may reschedule scan.
 Time of last insulin  dose*Use of insulin degrades scans; insulin may need to be withheld, its timing altered, or diabetes management temporarily changed (1,2).
InjectionInjection questions are asked for use by technologist and as quick reference for interpreting physician but do not substitute for entering dose on scan order or in medical record. For computerized dose tracking and SUV computation, dose is input before scanning.
 Prior PET scan  datePhysician may want to compare current scan with prior scan. Patient can confirm any scans found in medical records. Technologist will scan patient in same position as before unless new information dictates otherwise.
 Prior CT scan datePhysician may want to refer to most current CT scan when interpreting PET scan. Contrast agent from recent scan may attenuate PET signal and cause facility to apply its wait-period protocol (7).
 Chemotherapy and  radiation therapyChemotherapy or radiation therapy may change physiology and thus uptake; questions on therapy are asked for use by technologist and for interpreting physician’s reference (8,9).
 Date of recent  surgeries or  biopsiesIf scanning takes place too soon after surgery for cancer, increased uptake from healing may interfere with image interpretation (9).
 Prior malignanciesAlthough patients are scanned per indication on order, knowledge of prior cancers such as melanoma may require that scan range be changed (3).
 Prior surgeries or  biopsiesQuestions about whether patient has ever had surgery may elicit a problem the patient has with lying flat or still and may be helpful for physician when viewing altered physiology or anatomy.
 Prior experience  with medical  devicesInformation gained by asking if patient has prior experience with implants, intravenous lines, or ostomy sites may help in determining placement of bags on imaging table (after emptying, if involving urine) and patient’s ability to lie flat with such devices in place.
 Coronary artery  disease and  pacemakersQuestions about coronary artery disease may elicit a problem the patient has with lying flat or still. Coronary artery disease can affect clearance of intravenous contrast agents. It is helpful to know in advance that scout scan will show a pacemaker, and technologist can ensure that its implantation date was at sufficient interval before scan, in accord with facility’s protocol (10).
 Metallic objectsArtificial joints, shrapnel, and other metallic objects may cause CT attenuation and star artifact, which, depending on type of scanner software, may affect SUV. Physician should be aware of such objects in case patient departs, and thus cannot be questioned, before images are ready for interpretation (11).
 Claustrophobia  and lying supine  for 30 minEven if patient denied, at scheduling, being claustrophobic or unable to lie supine, the question should be asked again before injection. Simply showing scanner to patient may reveal need for anxiolytic medication and rescheduling. Questioning also allows technologist to confirm that medicated patients have driver.
 ExerciseQuestioning about exercise allows technologist to confirm compliance with prior instruction not to engage in strenuous exercise for 24–48 h before scan (2,4).
 Intramuscular  injectionsIntramuscular injections such as flu or other vaccinations can cause increased uptake. Awareness of any such injections is important in image interpretation, especially for melanoma patients (3).
 InfectionsInfection can cause increased uptake, especially in chemotherapy patients. Awareness of current infection allows scan to be rescheduled, if necessary, to prevent difficulty with differentiating between infection uptake and cancer uptake (12).
 Recent traumaIf patient has sustained recent trauma, such as car accident or fall, uptake from healing may interfere with image interpretation (12). Type of trauma may also affect patient’s ability to lie flat and still during scanning.
 PainTensing muscles near site of pain can cause increased muscle uptake, just as occurs during exercise. Inquiring about pain can also elicit whether patient can lie still and flat.
 Renal failureIn facilities that use intravenous contrast agents, knowledge of patient’s renal function is important. Also, dialysis patients requiring PET may need to be scheduled for nondialysis day, depending on facility’s protocol.
 Chronic obstructive  pulmonary  diseaseAnswers to questions about chronic obstructive pulmonary disease can be another indicator of whether patient can lie flat.
 AllergiesUse of intravenous contrast may be contraindicated in patients allergic to iodine or seafood. Also, in emergencies, medical responders need to be aware of any known allergies (13).
 Contrast reactionsIf intravenous contrast is to be given, patient must be questioned not only about renal function and allergies but about any prior contrast reaction, no matter how minor. In such cases, supervising physician must approve administration, facility’s intervention protocol must be followed, and patient may need to sign statement about past reaction (13).
  • * For insulin-dependent diabetic patients.