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Positron emission tomography, also called PET imaging or a PET scan, is a type of nuclear medicine imaging.

Nuclear medicine is a branch of medical imaging that uses small amounts of radioactive material to diagnose or treat a variety of diseases, including many types of cancers, heart disease and certain other abnormalities within the body.

Patient Preparation

• High protein/fat and low carbohydrate diet day before study (less cardiac activity)
• NOTHING to eat or drink for 4 hours prior to study
• No IV fluids with glucose
• No TPN
• Can take medications
• Obtain glucose (needs to be less than 200mg/dL)
• Avoid Injecting same side as lesion (can get axillary uptake)
• Encourage lots of water
• Foley; Hydrate 1000-1500cc; Furosemide 20mg IV slow injection over 1 min
• Breast Feeding: Stop for 8 hours (do not hold infant against breast for 4 hours)

Diabetic Patients

• Well controlled- overnight fast, no insulin or hypoglycemics (1st pt scanned)
• Poorly controlled - 4 hour fast after light meal with 10 U regular insulin

After Injection

• Relax for 30 minutes (may need sedation)
• Do not talk, eat or chew (increased uptake in neck region)
• Stay in dimly lit quiet area

FDG Adminitration

• Whole body:10-20mCi (140microCi/kg)
• Brain only (10mCi)
• Pediatric 140microCi/kg
• T 1/2 110 min

Imaging Delay

• Brain 30 min after injection
• Whole Body 45min after injection

Brain Imaging

• 1 min acquisition for positioning
• 3D acquisition for 8 min
• Calculated attenuation correction

Whole Body Imaging

• Head to thigh
• 5-7 bed positions
• 4 min emission/ 2.5 min transmission per bed position

Effects of Radiation Therapy on PET Imaging

• Hypermetabolic (lung esophagus myocardium, usu subside 4-8 weeks)
• Hypometabolic (bone marrow, spine, brain)

Post Operative Changes

• Need to wait 6-8 weeks after surgery to do scan after thoracotomy

False Positives

• Acute infections, TB, sarcoid

False Negatives

• <7mm in lung, esp at bases, < 10mm in liver
• Carcinoid, bronchoalveolar, mucinous and lobular cancers

Benign Lesions

• Hyperplasia (G-CSF, anemia, Cushing's, Grave's, Paget's, fibrous dysplasia)
• Ischemia
• Benign tumors (mixed salivary tumors, villous adenoma, adrenal adenoma, angiomyolipoma)
• Inflammation

Adrenal Adenoma vs Carcinoma

• AJR 1997:168:1357-1360
• 33 adrenal lesions in pt with NSCLC; 27/33 (mets at biopsy)
• 92% sensitivity; 100% specific

Lung Cancer Staging

• Lancet 2002; 359:1388-93
• 188pts randomized to routine eval or routine plus PET
• Routine: 39 pt (41%) had futile thoracotomy
• Routine + PET: 19pts (21%) had futile thoracotomies