Transcript No Slide Title

Problems and Pitfalls in the
Interpretation of PET/CT
George Segall, M.D.
Stanford University
False Negative FDG PET
Histology
Low-grade glioma
Low-grade lymphoma
Bronchoalveolar lung cancer
Hepatoma
Renal cell carcinoma
Prostate cancer
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
Physiologic Uptake
Tonsillar Hyperplasia
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?
a. Hyperplastic polyp
b. Adenomatous polyp
c. Adenocarcinoma
d. All of the above
Question 1
The correct answer is
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
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
• Respiratory
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
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