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
George Segall, M.D.
VA Palo AltoHealth Care System
Stanford University
Problems and Pitfalls in the Interpretation of PET/CT
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
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
Diabetes12 hours
fed 04/25 fasting 05/08
Post Prandial Scan
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
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
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
False Positive FDG PET
Physiologic
Benign Neoplasm
Inflammatory
Miscellaneous
Adenoma
Granuloma, sarcoid, rheumatoid
Prosthesis, grafts
Fractures
Physiologic Uptake
FDG subcutaneous infiltration
Physiologic Uptake
Tonsillar Hyperplasia
Talking
Nakamoto. Radiology 2005;234;879-885
Physiologic Uptake
Physiologic Uptake: Brown Fat
Brown Fat
• What is brown fat?
• Methods to reduce FDG uptake
Heat
Reassurance
Sedatives Beta blockers
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
51 yr old man with colon cancer treated with rectosigmoid colectomy and adjuvant chemotherapy.
SUV adrenal 4.0SUV liver 2.2
Adenoma
Adrenal adenoma
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?
a. Hyperplastic polyp
b. Adenomatous polyp
c. Adenocarcinoma
d. All of the above
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.
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
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
• Head movement
Secure head, or use head holder
Patient Movement
• Respiratory variation
from Ben Yeh MD, UCSF
Partial expiration best:
“Breathe in, exhale, don’t breathe”
Respiratory Misregistration
Respiratory Misregistration
Sureshbabu and Mawlawi. J Nucl Med Technol 2005;33:156-161
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
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