Article Figures & Data
Figures
- FIGURE 1.
Effect of exercise on skeletal muscle 18F-FDG uptake. Maximum-intensity-projection image of 18F-FDG PET study demonstrates prominent diffuse 18F-FDG uptake in skeletal and cardiac muscles in patient who performed strenuous exercises in the 2 d before undergoing PET.
- FIGURE 2.
Effect of metformin on intestinal 18F-FDG uptake. (A) Coronal 18F-FDG PET image of diabetic patient while on metformin demonstrates prominent bowel activity. (B) Prior 18F-FDG PET study of same patient while not on metformin shows only mild tracer activity in bowel.
- FIGURE 3.
(A) Maximum-intensity-projection image shows intense bilateral radiotracer activity (arrows) in cervical and supraclavicular regions secondary to activation of BAT. (B and C) Axial non–contrast-enhanced CT (B) and PET (C) images localize radiotracer activity to cervical adipose tissue.
Tables
Dietary Instructions • Complete food fasting is required, including cessation of tube feedings, dextrose-containing intravenous fluids, and parenteral hyperalimentation (minimum of 6 h before scan). • Only plain water is permitted; flavored water is not allowed (6 h before scan). • Absolutely no sugar or carbohydrate intake of any kind is allowed, including candy or breath mints (6 h before scan). • No caffeine, alcohol, and nicotine products are allowed (12 h before scan). • A high-protein, low-carbohydrate diet is required (24 h before scan). Sample menu: Main course: Beef, turkey, pork including bacon, fish, chicken, eggs. Vegetables: Broccoli, asparagus, cauliflower, zucchini, spinach, mushrooms. Desserts: Cheese, cottage cheese. Drinks: Unsweetened black coffee, unsweetened tea, water. Artificial sweeteners are not permitted. Carbohydrates/sugars to be avoided: Bread, bagels, cereal, cookies, toast, pasta, crackers, muffins, peanut butter, nuts, fruit, fruit juice, potatoes, candy, rice, cornbread, carrots, beets, chewing gum, mints, cough drops, and sweet soft drinks. • Patients are encouraged to stay well hydrated. Recommend 2 L of plain drinking water in the 4-h period immediately before PET/CT. Continued hydration as tolerated is recommended after scan completion to enhance 18F-FDG excretion. Activity Restriction (Minimum 24 h Before Study, Although 48 h Is Ideal) • Exercises such as jogging, cycling, weightlifting, strenuous housework, yard work, and sexual activity should be avoided. • Patients are advised not to chew gum. Medications • All prescription medications should be taken as directed (insulin and oral hypoglycemics are discussed under “Diabetic Patients”). Diabetic Patients • Home blood glucose checks should be performed in the days leading to the PET exam to ensure adequate blood glucose levels (≤200 mg/dL). • All prescription oral diabetes medications should be taken as directed. • Metformin may be discontinued for 2 days before the study if there are gastrointestinal tumors (to minimize inadvertent gastrointestinal uptake) or if there has been prominent gastrointestinal uptake on prior PET studies. • Patients on regular insulin should take their normal amount of insulin along with breakfast by 6 am. They should be scheduled between 12 noon and 1 pm. Alternatively, those receiving evening or bed-time long-acting insulin should be scheduled at 7 am after an overnight fast. • Patients on continuous insulin infusion/pump are scheduled early in the morning (by 8 am) and eat breakfast after the PET study. The insulin pump is kept on the night/basal setting until after the PET study. Strategies for addressing hyperglycemia (>200 mg/dL) immediately before 18F-FDG PET study: • Reschedule scan, encourage frequent home blood glucose checks, and ask patient to contact primary care physician for further guidance on glycemic control (OR) • Start regimen of intravenous short-acting regular insulin. (Implementation requires staff with extensive training on use of intravenous insulin, frequent blood sugar monitoring, and identification and correction of potential hypoglycemia.) 2 units for blood sugar between 201 and 250 mg/dL. 3 units for blood sugar between 251 and 300 mg/dL. 4 units for blood sugar between 301 and 350 mg/dL. 5 units for blood sugar between 351 and 400 mg/dL. Target blood sugar is ≤200 mg/dL. 18F-FDG is injected at least 60 min (ideally 90 min) after insulin administration. Premedication (as Needed) • For patients with head and neck cancer, claustrophobia, anxiety, or a need to relax skeletal muscles: Oral alprazolam, 0.5 mg, at the time of 18F-FDG injection. (Patients should be warned against driving because of sedating effects and psychomotor impairment.) • For patients with prominent brown adipose tissue uptake: Oral β-blocker propranolol, 20 mg, 1 h before 18F-FDG injection. (Heart rate and blood pressure monitoring must be performed while the patient is in the PET clinic.) Environmental Conditions • Patients should avoid cold exposure for 2 d before the study. • Patients should avoid air conditioning on the day of the study. • Patients should keep the car windows rolled up during travel to the PET/CT clinic and, if necessary, use a car heater on cool days. • Patients should wear warm clothing, including long pants or slacks, long sleeves in summer (no shorts or tank tops), and a sweater, jacket, and cap on cold or even slightly cool days. • Maintain a warm room temperature (minimum, 75°F), and provide warm blankets during the uptake period. Category SNMMI (2) EANM (3) ACR (5) NCI (4) Proposed standard protocol Fasting period At least 4–6 h At least 6 h Minimum of 4 h Minimum of 4 h Minimum of 6 h Hydration Oral hydration with water 1 L of water by mouth 2 h before injection; 0.5 L of water during uptake period as tolerated Typically oral hydration, intravenous in special circumstances At least 2–3 (12 oz [355 mL] each) glasses of water during fasting and 250–500 mL of water after injection and before scanning 1–2 L of plain water as tolerated during the 4 h immediately before PET/CT scan Diet Not stated Not stated Not stated Low-carbohydrate diet for 24 h High-protein, low-carbohydrate diet for 24 h Physical activity/exercise restriction Not stated At least 6 h before PET study 1 d before scan 1 d before scan Avoid for minimum of 24 h (ideally 48 h) before scan Medications Not stated Take as prescribed Not stated Not stated Take as directed Glucose level before tracer injection 150–200 mg/dL <120 mg/dL (<7 mmol/L) Not stated Nondiabetic patients,<120 mg/dL; diabetic patients, 150–200 mg/dL <200 mg/dL Premedication Lorazepam or diazepam before 18F-FDG injection to reduce uptake by BAT and skeletal muscle or β-blockers to reduce BAT uptake Sedatives such as short-acting benzodiazepines in patients with head and neck tumors, anxiety, or claustrophobia Premedication for anxiety, if indicated, without mention of a specific recommendation A sedative such as diazepam in extremely anxious patients or when area of interest is head and neck Oral alprazolam, 0.5 mg, for patients with head and neck cancer, claustrophobia, or anxiety; oral β-blocker (propranolol, 20 mg) 1 h before 18F-FDG injection for patients with prominent BAT Timing of PET Not stated 10 d after last chemotherapy dose; 3 mo after radiation Not stated At least 2 wk after end of a specific chemotherapy cycle; 6–8 wk or longer after radiation therapy At least 2 wk after end of last chemotherapy cycle; 6-8 wk after surgery; 12 wk after radiation
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