Published on January 24, 2016
1. How to Perform F-18 FDG PET/CT Imaging Jiraporn Sriprapaporn, M.D. Div. of Nuclear Medicine, Department of Radiology Faculty of Medicine Siriraj Hospital Mahidol University Last updated on 24 January 2016
2. PET/CT: Procedure Guidelines SNMM guideline EANM guideline 2006 2015 Jiraporn_PET/CT in Onco 2016
3. Procedure Guideline for Tumor Imaging with F-18 FDG PET/CT 1.0* Dominique Delbeke, R. Edward Coleman, Milton J. Guiberteau, et al. J Nucl Med Vol. 47 No. 5 885-895, 2006 http://snmmi.files.cms-plus.com/docs/jnm30551_online.pdf Jiraporn_PET/CT in Onco 2016
4. Procedure Guideline for Tumor Imaging with 18F-FDG PET/CT 1.0* I. PURPOSE II. BACKGROUND INFORMATION AND DEFINITIONS III. EXAMPLES OF CLINICAL OR RESEARCH APPLICATIONS IV. PROCEDURE A. Patient preparartion B. Information Pertinent to Performing Procedure C. Precautions D. Radiopharmaceutical E. Image acquisition F. Interventions G. processing H. Interpretation: Normal physiologic distribution I. Reporting J. QC K. Sources of errors: Normal Variants, pitfalls & artifacts V. QUALIFICATION OF PERSONNELS VI.ISSUESREQUIRINGFURTHERCLARIFICATION Jiraporn_PET/CT in Onco 2016
5. III. EXAMPLES OF CLINICAL OR RESEARCH APPLICATIONS Indications for 18F-FDG PET/CT include: 1. Differentiating benign from malignant lesions 2. Searching for an unknown primary tumor when metastatic disease is discovered as the first manifestation of cancer or when the patient presents with a paraneoplastic syndrome 3. Staging known malignancies 4. Monitoring the effect of therapy on known malignancies 5. Determining whether residual abnormalities detected after treatment represent tumor or posttreatment fibrosis or necrosis 6. Detecting tumor recurrence, especially in the presence of elevated levels of tumor markers 7. Selecting the region of a tumor most likely to yield diagnostic information for biopsy 8. Guiding radiation therapy planning 9. Nononcologic applications, such as evaluation of infection and atherosclerosis 10. 18F-FDG PET/CT is not equally effective for all malignancies, but other tracers are available. Jiraporn_PET/CT in Onco 2016
6. Appropriate PET Scan Timing Jiraporn_PET/CT in Onco 2016 Postbiopsy 1 Wk Postsurgery 6 Wks Post CMT 4-6 Wks Post ERT 4-6 Months • Alavi A. PET and PET/CT: A Clinical Guide • Cook GJ, et al. Sem Nucl Med 2004
7. IV. PROCEDURE A. Patient Preparation Major goals to minimize tracer uptake in normal tissues, such as the myocardium and skeletal muscle, while maintaining uptake in target tissues (neoplastic disease). 1. Before arrival a) Fast and not consume beverages, except for water, for at least 4–6 h before the administration of 18F-FDG to decrease physiologic glucose levels and to reduce serum insulin levels to near basal levels. b) Oral hydration with water is encouraged. c) IV fluids containing dextrose or parenteral feedings also should be withheld for 4–6 h. d) IV contrast material should not be administered if serum creatinine > 2.0 mg/dL. Jiraporn_PET/CT in Onco 2016
8. A. Patient Preparation 2. Before injection a) For brain imaging, the patient should be in a quiet and dimly lit room since the injection throughout the uptake phase. b) For body imaging, the patient should remain seated or recumbent since the injection throughout uptake phase to avoid muscular uptake. c) Check blood glucose level Tumor uptake of 18F-FDG is reduced in hyperglycemic states. Most institutions reschedule the patient if the blood glucose level is greater than 150–200 mg/dL. Reducing the serum glucose level by administering insulin can be considered, but the administration of 18F-FDG should be delayed after insulin administration (duration of the delay depends on the type and route of administration of insulin). d) For CT scan, an intraluminal GI contrast agent may be administered for better visualization of the GI tract unless it is medically C/I or unnecessary for the clinical indication (see Section E.2.b.). Jiraporn_PET/CT in Onco 2016
9. TABLE 2: Patient Preparation Recommendations (Surasi DH, JNMT 2014) 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 carbo- hydrate diet for 24 h Physical activity/exercis e 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 before18F-FDG inj. to reduce uptake by BAT & 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 CMT dose; 3 mo after RT Not stated At least 2 wk after end of a specific CMT cycle; 6–8 wk or longer after RT At least 2 wk after end of last CMT cycle; 6-8 wk after surgery; 12 wk after RT
10. B. Information Pertinent to Performing Procedure 1. Focused history: type and site of cancer, dates of diagnosis and treatment (biopsy results, surgery, radiation, chemotherapy, and administration of bone marrow stimulants and steroids), and current medications. 2. History of diabetes, fasting state, and recent infection 3. Patient’s ability to lie still for the duration of the acquisition (15–45 min) 4. History of claustrophobia 5. Patient’s ability to put his or her arms overhead Jiraporn_PET/CT in Onco 2016
11. C. Precautions 1. Protect workers from radiation hazard; pregnant nurses 2. Check for adverse reactions of any drug 3. Try to avoid radiation hazard to the patient; instrument, acq protocol, R’pharm dose 4. Minimizing radiation exposure to the patient’s family and to the general public, where appropriate. 5. Weight and size tolerances of equipment Pregnant women should not undergo F-18 FDG PET-CT. F-18 FDG does cross the placenta. Breast-feeding is not recommended for 10 hrs after administration of F-18 FDG. Jiraporn_PET/CT in Onco 2016
12. D. F-18 FDG Radiation Dosimetry for Adults and Children Patient Administered activity Organ receiving the largest radiation dose, mGy/ MBq (rads/mCi) Effective dose,mSv/MBq (rems/mCi) Adult 370–740 MBq (10–20 mCi) Bladder, 0.16* (0.59) 0.019 (0.070) Child (5 yr) 5.18–7.4 MBq/kg (0.14–0.20 mCi/kg) Bladder, 0.32# (1.2) 0.050 (0.18) * Voiding interval, 3.5 h. Changes in bladder wall dose are approximately linear with changes in voiding interval; therefore, for a voiding interval of 2.0 h, dose to bladder wall would change by a factor of 2/3.5 # Voiding interval, 2.0 h. Data are from International Commission on Radiological Protection. Radiation Dose to Patients from Radiopharmaceuticals. St. Louis, MO: Elsevier; 2000:49. ICRP publication 80. The effective dose for PET/CT is about 5 to 80 mSv (0.5–8.0 rems) Jiraporn_PET/CT in Onco 2016
13. E. PET/CT Acquisitions 1. Field of view, positioning, and preacquisition preparation A. Skull base–to–mid thigh imaging [from the external auditory meatus to the midthigh region.] is generally recommended for most tumor types. B. Whole-body tumor imaging (vertex-to-toe) is performed for tumors with a high likelihood of scalp, skull, or brain involvement or lower extremity involvement. [M. melanoma, MM] C. Limited-area tumor imaging can be considered when critical abnormalities are likely to be localized in a known region of the body (e.g., SPN, probable lung CA, evaluation of hilar LN involvement, H & N cancer, and monitoring of Rx of LABC). However, performing whole-body tumor imaging offers the advantage of staging the entire body. Jiraporn_PET/CT in Onco 2016
14. E. PET/CT Acquisitions D. For body imaging, the arms should be elevated over the head. E. For imaging of the head and neck, the arms should be positioned along the side. [Arms along the side may produce beam-hardening artifacts over the torso.] F. The patient should void the bladder before the acquisition of the images to limit the radiation dose to the renal collecting system and bladder. G. Metallic objects should be removed from the patient whenever possible. Arms up Arms down Jiraporn_PET/CT in Onco 2016
15. E. PET/CT Acquisitions 2. Protocol for CT imaging 2.1 AC/AL CT 2.2 diagnostic CT A. If the CT scan is obtained for AC/AL, a low mAs setting is recommended to decrease the radiation dose to the patient. B. For a diagnostic CT scan, standard CT mAs settings are recommended. IV or oral contrast material may be used. A separate CT acquisition may be necessary for a particular region of the body. High intravascular concentrations of IV contrast material may cause an attenuation correction artifact on the PET image, but the impact usually is modest. AC:Attenuation Correction AL:Anatomy Localization Jiraporn_PET/CT in Onco 2016
16. E. PET/CT Acquisitions 2. Protocol for CT imaging C. An intraluminal GI noncaloric contrast agent may be administered to provide adequate visualization of the GI tract unless it is medically contraindicated Collections of highly concentrated barium or iodinated contrast agents can result in an attenuation correction artifact that leads to a significant overestimation of the regional F-18 FDG concentration Diluted oral contrast agents cause less overestimation and do not affect PET image quality. Jiraporn_PET/CT in Onco 2016 Contrast medium increased SUV, but not clinically significant !
17. E. PET/CT Acquisitions 2. Protocol for CT imaging D. Shallow breathing during the CT acquisition is preferred. PET and CT images match as closely as possible Respiratory motion results in inaccurate localization of lesions at the base and periphery of the lungs, in the dome of the liver, or near any lung–soft tissue interface. Motion correction or respiratory gating is recommended when available. Jiraporn_PET/CT in Onco 2016
18. E. PET/CT Acquisitions 3. Protocol for F-18 FDG PET Imaging A. The radiopharmaceutical should be injected at a site contralateral to the site of concern. Emission images should be obtained at least 45 min after F-18 FDG injection, some facilities image at 60 or 90 min. The F-18 FDG uptake time should be constant for comparison by use of SUV. B. The emission image acquisition time varies from 2 to 5 min or longer per bed position for body imaging and is based on the administered activity, patient BW, and sensitivity of the PET scanner. Typically, for imaging skull to midthigh, about 7-8 bed acquisition. Jiraporn_PET/CT in Onco 2016
19. E. PET/CT Acquisitions 3. Protocol for F-18 FDG PET Imaging C. Semiquantitative estimation of tumor glucose metabolism by use of the SUV is based on relative lesion radioactivity measured on AC PET images and normalized for the injected dose and BW, lean body mass, or BSA. Individual PET/CT scanner Serum glucose level F-18 FDG dose administration Uptake time Type of reconstruction algorithms Type of attenuation maps Size of the ROI Uptake distribution in the body Methods of analysis (e.g., maximum and mean). D. Semiquantitative estimation of tumor metabolism can be based on the ratio of F-18 FDG uptake in a lesion to F-18 FDG uptake in internal reference regions, such as the blood pool, mediastinum, liver, and cerebellum. Jiraporn_PET/CT in Onco 2016
20. Factor affecting SUV measurement [2008: https://www.aapm.org/meetings/08SS/documents/Mawlawi.pdf Jiraporn_PET/CT in Onco 2016 1. Patient Factors ◦ Patient size ◦ Fasting period ◦ Blood Glucose level 2. Radiotracer ◦ Amount of radiotracer injected ◦ Extravasation 3. Scan Conditions – Uptake time post injection – Patient stress during uptake (room temperature, etc.) – Patient motion during acquisition – PET/CT vs Dedicated PET 4. Intrinsic System Parameters and Capability (Scanner specifications) – Calibration – QA – Maintenance of operating parameters – Performance characteristics of scanners – Partial Volume Effects (PVE) – Image processing algorithms 5. Others ◦ ROI ◦ Contrast media, both oral & IV contrast increase in SUV values
21. SUV Jiraporn_PET/CT in Onco 2016 SUVmax is generally preferred because it’s more reproducible. Factors affecting SUV are ◦ Patient: Pt size- BW, BSA Serum glucose level ◦ Instrument: Scan specification ◦ Radiopharmaceutical: Dose injected Extravasation of radiotracer alterWB distribution ◦ Uptake time after F-18 FDG injection ◦ Image protocol & processing ROI: Position & size used for SUV calculation, PVE E. Coleman
22. SUV (Standardized Uptake Value) Or SUR : Standardized Uptake Ratio Semi-quantitative measurement of degree of F-18 FDG accumulation in the ROI to the total injected dose and the patient's BW. [R41. Lowe VJ, Naunheim KS. Thorax 1998] Malignant tumors: increased glycolytic rate increase glucose uptake high SUV Concentration in ROI (uCi/g) SUVbw = --------------------------------------- Injected Dose (mCi) / BW (kg). Jiraporn_PET/CT in Onco 2016
23. F. Interventions 1. Intense urinary bladder tracer activity degrades image quality and can confound the interpretation of findings in the pelvis. Hydration and a loop diuretic, without or with bladder catheterization, may be used. 2. Keeping the patient in a warm room for 30–60 min before the injection of F-18 FDG, particularly in cold climates and air-conditioned environments, will help to minimize brown fat uptake. Lorazepam or diazepam given before the injection of 18F-FDG may reduce uptake by brown adipose tissue or skeletal muscle. Beta-blockers also may reduce uptake by brown fat. Jiraporn_PET/CT in Onco 2016
24. PET emission data consist of the number of events along lines of response (LOR) between detector pairs. The emission data must be corrected for detector efficiency (normalization), system dead time, random coincidences, scatter, attenuation, and sampling nonuniformity. Scanners with retractable septa can acquire data in both 2D and 3D modes, whereas scanners wo septa acquire data in the 3D mode only. Datasets acquired in the 3D mode can be rebinned into 2D data and reconstructed with a 2D algorithm or can be reconstructed with a fully 3D algorithm. Iterative reconstruction are available in both 2D and 3D modes, replacing FBP methods used previously. For a given algorithm, the appropriate reconstruction parameters will depend on the acquisition mode, the type of scanner, and the imaging task. It is good to archive reconstructions both with and without AC [to resolve issues arising from potential artifacts generated by the CT-based AC procedure.] The reconstructed images can be displayed in transaxial, coronal, and sagittal planes and as a rotating maximum-intensity projection (MIP) image. G. Processing 1. PET reconstruction: Jiraporn_PET/CT in Onco 2016
25. Methods of Attenuation Correction 1. CT transmission imaging with PET/CT scanners CT energies (40–140 keV) 2. Transmission scanning with an isotopic source (Ge-68): dedicated PET scanners Jiraporn_PET/CT in Onco 2016
26. G. Processing 3. Display: With an integrated PET/CT system, typically the software packages provide registered and aligned CT images, F-18 FDG PET images, and fusion images in the axial, coronal, and sagittal planes as well as MIP images for review in the 3D cine mode. F-18 FDG PET images with and without AC should be available for review. Jiraporn_PET/CT in Onco 2016 • LUNGS: Activity in AC < NAC (Lung has low attenuation) • LIVER: Activity in AC is more uniform than NAC (Liver is deep and is attenuated by other structures) • SKIN: Skin activity is evident on NAC but not in AC. (Skin is superficial & has less attenuation) NAC AC
27. Attenuation-corrected (AC) vs Nonattenuation-corrected (NAC) Images Jiraporn_PET/CT in Onco 2016http://www.med-ed.virginia.edu/courses/rad/petct/Interpretation.html MIP MIP AC NAC
28. Display of PET-CT Images MIP MIP: Maximum Intensity Projection Jiraporn_PET/CT in Onco 2016
29. F-18 FDG Imaging Avoid caloric intake least 4-6 hours prior to FDG-PET study with good hydration.. FBS 70-110 mg/dL is ideal for FDG-PET > 200 mg/dL reshedule Hyperinsulinemia increase FDG uptake in skeletal muscle. No regular insulin SC injected within 4 hrs of having FDG administration. IV. inject 140-200 uCi/Kg of F-18 FDG (10-20 mCi) 60 minutes after F-18 FDG was injected, low-dose CT scan is performed followed by whole-body PET scan. Whole-body study: Skull base-to-mid thigh, vertext-to-mid thigh, vertext-to-toe. PET scan time: 2-3 min/ bed position depending on type of PET scanner. CT scan: low mAs scan is adequate for attenuation correction & anatomical localization. High mAs scan is needed for diagnostic CT scan. Oral contrast and IV contrast for diagnostic CT as requested. Jiraporn_PET/CT in Onco 2016
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