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 Hyperglycemia > 150 mg/dL

Post Prandial Scan 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 • Fasting: Euglycemia 6 hours Diabetes 12 hours fed 04/25 fasting 05/08

Fasting Scan in a Diabetic 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.

Hyperglycemia 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)

Insulin Effect on FDG uptake 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)

False Positive FDG PET Physiologic Benign Neoplasm Adenoma Inflammatory Granuloma, sarcoid, rheumatoid Miscellaneous Prosthesis, grafts Fractures

Physiologic Uptake FDG subcutaneous infiltration 3

Physiologic Uptake Tonsillar Hyperplasia 3

Physiologic Uptake Talking Nakamoto. Radiology 2005;234;879-885

Physiologic Uptake: Brown Fat

Brown Fat • What is brown fat? • Methods to reduce FDG uptake Reassurance Heat Sedatives Beta blockers

Adenoma 74 yr old man with seizures and recent cognitive disorder

Adenoma  70 yr old man 2 months post chemoXRT for R piriform sinus cancer stage 3, T3N2M0.

Adenoma 63 y/o man 4 months post chemoXRT for R tonsil cancer T2N1M0

Adenoma Adrenal adenoma SUV adrenal 4.0 SUV liver 2.2 51 yr old man with colon cancer treated with rectosigmoid colectomy and adjuvant chemotherapy.

Adenoma 82 year old man with wt loss and liver mass

Question 1 Which of the following neoplasms have been associated with focal FDG uptake in the colon? Hyperplastic polyp b. Adenomatous polyp c. Adenocarcinoma d. All of the above

Question 1 The correct answer is d. All of the above 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. 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. d. All of the above

Nodular Hyperplasia 74 y/o man with metastatic disease to neck from unknown primary, now NED after chemoXRT

Infection 68 year old man with solitary lung nodule. Biopsy: aspergillosis 3

Granulomatous Disease 62 year old man with hilar and mediastinal adenopathy. Biopsy: sarcoidosis

Miscellaneous Causes Thyroiditis

Miscellaneous Causes Rib Fracture

Problems with CT Attenuation and scatter Beam hardening Volume averaging

Beam Hardening Gollub et al. J Nucl Med 2007;48:1583-1591

Beam Hardening

Volume Averaging Gollub et al. J Nucl Med 2007;48:1583-1591

Problems with PET/CT Patient movement Respiratory misregistration Attenuation correction

Patient Movement • Head movement Secure head, or use head holder

Respiratory Misregistration variation Partial expiration best: “Breathe in, exhale, don’t breathe” from Ben Yeh MD, UCSF

Respiratory Misregistration Sureshbabu and Mawlawi. J Nucl Med Technol 2005;33:156-161

Question 2 Respiratory misregistration in PET/CT is minimized when 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

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

Attenuation Correction Sureshbabu and Mawlawi. J Nucl Med Technol 2005;33:156-161

Attenuation Correction Sureshbabu and Mawlawi. J Nucl Med Technol 2005;33:156-161

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

Summary • CT artifacts can be avoided by optimizing technique • PET/CT artifacts can be reduced by proper patient preparation and instructions

3