Question to Ask Before Injection of 18F-FDG
| Questions about… | Relevance |
| Diabetes | |
| Current glucose level | Scanning 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 level | If 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). |
| Injection | Injection 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. |
| Staging | |
| Prior PET scan date | Physician 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 date | Physician 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 therapy | Chemotherapy 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 biopsies | If scanning takes place too soon after surgery for cancer, increased uptake from healing may interfere with image interpretation (9). |
| Prior malignancies | Although 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 biopsies | Questions 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 devices | Information 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. |
| Screening | |
| Coronary artery disease and pacemakers | Questions 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 objects | Artificial 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 min | Even 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. |
| Exercise | Questioning 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 injections | Intramuscular 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). |
| Infections | Infection 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 trauma | If 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. |
| Pain | Tensing 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 failure | In 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 disease | Answers to questions about chronic obstructive pulmonary disease can be another indicator of whether patient can lie flat. |
| Allergies | Use 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 reactions | If 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.