george segall, m.d
DESCRIPTION
Problems and Pitfalls in the Interpretation of PET/CT. George Segall, M.D. Stanford University. False Negative FDG PET. Low-grade glioma Low-grade lymphoma Bronchoalveolar lung cancer Hepatoma Renal cell carcinoma Prostate cancer. Histology. Size. < 10 mm. Post prandial scans. - PowerPoint PPT PresentationTRANSCRIPT
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George Segall, M.D.
VA Palo AltoHealth Care System
Stanford University
Problems and Pitfalls in the Interpretation of PET/CT
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False Negative FDG PET
Histology
Size
Post prandial scans
Hyperglycemia
Low-grade gliomaLow-grade lymphomaBronchoalveolar lung cancerHepatomaRenal cell carcinomaProstate cancer
< 10 mm
> 150 mg/dL
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57 year old man with stage IV left tonsillar scca treated with chemoradiation 21 months ago. Patient was lost to follow-up until he was referred for PET/CT. Coronal images show low FDG uptake in the brain, and high uptake in the heart and skeletal muscles.
Post Prandial Scan
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• Fasting:
Euglycemia 6 hours
Diabetes12 hours
fed 04/25 fasting 05/08
Post Prandial Scan
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51 year old man with colon polyps and a stricture referred for PET/CT to evaluate for possible malignancy. Fasting blood glucose level = 289 mg/dL. Coronal images show a good quality scan with normal FDG biodistribution.
Fasting Scan in a Diabetic
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69 year old man with 2.3 cm RUL NSC lung cancer. FBS = 309 mg/dL. No insulin was given. Coronal images show a good quality scan with high FDG tumor uptake (max SUV 5.4)
Hyperglycemia
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63 year old man with 5 cm RUL adenocarcinoma. FBS = 299 mg/dL; 90 minutes after 15u of reg insulin IV FBS = 179 mg/dL at which time FDG was injected. Coronal images show a “muscle scan” with faint tumor uptake (max SUV = 2.0)
Insulin Effect on FDG uptake
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False Positive FDG PET
Physiologic
Benign Neoplasm
Inflammatory
Miscellaneous
Adenoma
Granuloma, sarcoid, rheumatoid
Prosthesis, grafts
Fractures
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Physiologic Uptake
FDG subcutaneous infiltration
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Physiologic Uptake
Tonsillar Hyperplasia
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Talking
Nakamoto. Radiology 2005;234;879-885
Physiologic Uptake
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Physiologic Uptake: Brown Fat
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Brown Fat
• What is brown fat?
• Methods to reduce FDG uptake
Heat
Reassurance
Sedatives Beta blockers
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74 yr old man with seizures and recent cognitive disorder
Adenoma
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70 yr old man 2 months post chemoXRT for R piriform sinus cancer stage 3, T3N2M0.
Adenoma
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63 y/o man 4 months post chemoXRT for R tonsil cancer T2N1M0
Adenoma
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51 yr old man with colon cancer treated with rectosigmoid colectomy and adjuvant chemotherapy.
SUV adrenal 4.0SUV liver 2.2
Adenoma
Adrenal adenoma
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Adenoma
82 year old man with wt loss and liver mass
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Question 1
Which of the following neoplasms have been associated with focal FDG uptake in the colon?
a. Hyperplastic polyp
b. Adenomatous polyp
c. Adenocarcinoma
d. All of the above
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Question 1
Gollub et al. Combined CT Colonography and 18F-FDG PET of Colon Polyps: Potential Technique for Selective Detection of Cancer and Precancerous Lesions. AJR Am J Roentgenol. 2007 Jan;188(1):130-8.
d. All of the above
The correct answer is
Friedland et al. 18-Fluorodeoxyglucose positron emission tomography has limited sensitivity for colonic adenoma and early stage colon cancer. Gastrointest Endosc. 2005 Mar;61(3):395-400.
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Nodular Hyperplasia
74 y/o man with metastatic disease to neck from unknown primary, now NED after chemoXRT
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Infection
68 year old man with solitary lung nodule. Biopsy: aspergillosis
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Granulomatous Disease
62 year old man with hilar and mediastinal adenopathy. Biopsy: sarcoidosis
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Miscellaneous Causes
Thyroiditis
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Miscellaneous Causes
Rib Fracture
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Problems with CT
Attenuation and scatter
Beam hardening
Volume averaging
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Beam Hardening
Gollub et al. J Nucl Med 2007;48:1583-1591
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Beam Hardening
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Volume Averaging
Gollub et al. J Nucl Med 2007;48:1583-1591
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Problems with PET/CT
Patient movement
Respiratory misregistration
Attenuation correction
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• Head movement
Secure head, or use head holder
Patient Movement
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• Respiratory variation
from Ben Yeh MD, UCSF
Partial expiration best:
“Breathe in, exhale, don’t breathe”
Respiratory Misregistration
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Respiratory Misregistration
Sureshbabu and Mawlawi. J Nucl Med Technol 2005;33:156-161
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Question 2
Respiratory misregistration in PET/CT is minimized when
a. CT is performed in end inspiration
b. CT is performed in mid expiration
c. CT is performed in end expiration
d. CT is performed during quiet breathing
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Question 2
The correct answer is
b. CT is performed in mid expiration
Sureshbabu W, Mawlawi O. PET/CT Imaging Artifacts. J Nucl Med Technol 2005;33:156-161
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Attenuation Correction
Sureshbabu and Mawlawi. J Nucl Med Technol 2005;33:156-161
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Attenuation Correction
Sureshbabu and Mawlawi. J Nucl Med Technol 2005;33:156-161
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Summary
• False negative FDG PET can be reduced by careful patient selection for appropriateness and proper preparation
• False positive FDG PET can be reduced by correlation with CT and knowledge of potential pitfalls
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Summary
• CT artifacts can be avoided by optimizing technique
• PET/CT artifacts can be reduced by proper patient preparation and instructions
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