• PET Imaging

    radiology-petct_01

    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

    DO NOT WEAR ANY METAL ON THE BODY

    • High protein/fat and low carbohydrate diet day before study (less cardiac activity)
    • NOTHING to eat for 6 hours prior to study
    • DRINK WATER ONLY, nothing else
    • DO NOT take cough syrup or throat lozenges
    • No IV fluids with glucose
    • No TPN
    • Can take medications, if tolerated, on an empty stomach
    • 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
    • Avoid children under 5 years old, pregnant, or trying to become pregnant women for 24 hours

    Diabetic Patients

    •Well controlled

    ◦ NO FOOD for 6 hours prior to study
    ◦ DRINK WATER ONLY, nothing else
    ◦ DO NOT take oral insulin medication

    • Poorly controlled

    ◦ Eat SMALL meal 4 hour prior to study with 10 U regular insulin
    ◦ DRINK WATER ONLY with your meal
    ◦ DO NOT take your medication if you have not eaten

    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