assessment of recurrent brain tumor
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Assessment of Recurrent Brain Tumor by 18F-FDG PET and SPECT Using 201Tl, 99mTc-MIBI, and 99mTc-ECD
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Background
To differentiate between recurrent brain tumor and radiation necrosis is a difficult diagnostic problem.Neither the symptoms nor the conventional radiographic findings clearly distinguish tumor from necrosis.Sampling error in biopsying such lesions may lead to misdiagnosis.
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Background201Tl SPECT
changes in blood flow, BBB breakdown, transmembrane transport into viable tumor cell proportional to Na/K ATPase
99mTc-MIBI SPECT electronic potential across the cell membrane, blood flow,
metabolic activity of the cell18F-FDG PET
Increased expression of glucose transporter molecules, Increased hexokinase, reduced glucose-6-phosphotase
In vitro studies: Vialble cancer cell number are best correlated with FDG uptake in brain tumor.
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Background
We reported a case of hypothalamus tumor who had been treated with radiotherapy. Recurrent lesion was suspected on MR images.18F-FDG PET, SPECT using 201Tl, 99mTc-MIBI, and 99mTc-ECD were used together to define the nature of the lesion and to guide treatment planning.
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Case presentation
Clinical history 49 y/o female 89-4: Left hypothalamus tumor found at KHVGH.
MRI: T1W1:homogeneous, hypointensity, enhancement(-). Biopsy can not be performed due to the deep location.
89-6: arranged R/T presumed low-grade glioma. (61.2 Gy/34 fractions)
91-7: Right side headache. MRI found a new lesion in right frontal and corpus callosum region, measuring about 2 cm.
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TIWI
hypointensity with heterogenous enhancement
T2WI
edema around the lesion
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Case presentation18F-FDG PET at VGH, Taipei Head and neck and brain imaging from head to sh
oulder was performed at 45mins after intravenous injection of 11.64mCi of 18F-FDG.
Siemens EXACT HR+ scanner Fasting for 6 hrs was required proor to the scannin
g. Imaging was reconstructed iteratively with attenuat
ion correction.
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Case presentationSPECT 201Tl: 5mCi, 99mTc-MIBI: 30mCi
acquire images 15 mins after injection. 60 projections, 60s per view, 128x128 matrix Semi-quantitative analysis:
The L/N ratio: average counts for the ROI in the lesion to its mirror image in normal brain tissue.
99mTc-ECD: 20mCi Acquire images 30 mins after injection. 60 projections, 60s per view, 128x128 matrix
(triple-head gamma camera, fanbeam collimator)
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FDG-PETThallium
MIBI ECD
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Case presentationThe L/N ratio: Tl: 2.71, MIBI: 7.94
The imaging results of 18F-FDG PET, 201 Tl and 99mTc-MIBI SPECT are indicative of viable tumor.
The patient went on 2nd R/T in 92-4. (50.4Gy)
Follow-up exams with MRI, 201 Tl and 99mTc-MIBI SPECT were performed in 92-8.
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89-4
92-8
Pre-R/T91-10
1st R/T
2ndR/T
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91-10 post 1st R/T 92-8 post 2nd R/T
Thallium
MIBI
MRI (T1WI)
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92-8 post 2nd R/T
T1WI C(+) Thallium
A new lesion in left mesial temporal.
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Summary89-4: left hypothalamus tumor89-6: 1st radiotherapy 91-10: right frontal new lesion on MRI recurrence or radiation necrosis? 18F-FDG PET, SPECT of 201Tl, 99mTc-MIBI were compatible with r
ecurrence.
92-4: 2nd radiotherapy 92-8: follow-up clinical symptom deterioration right frontal lesion progression: T1WI(+), Tl(+), MIBI(+). a new lesion in left mesial temporal: T1WI(+), Tl(+), MIBI(-).
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Discussion
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Recurrent tumor vs radiation necrosis
Similar symptomsOverlapping onset time radiation necrosis: within 1 to 2 years after
treatment is complete
MRI: indistinguishable contrast enhancement central necrosis variable edema and mass effect radiation necrosis: sometimes distant from the
tumor site
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Recurrent tumor vs radiation necrosis
201Tl SPECT Yoshii et al. have shown the superiority of Tl-201 SPECT ov
er MRI. (Eur J Nucl Med 1993,20:39) Dierckx et al.
90 patients for diagnosing brain tumor Sensitivity: 71.7%, specificity: 80.9% (Eur J Nucl Med 1994,21:621)
99mTc-MIBI SPECT Yamamoto et al. compared MIBI with Tl in 21 patients and fo
und same accuracy (90%). (Nucl Med commun 2002,23:1183) O’Tuama et al. compared MIBI and Tl in 19 children with brai
n tumors. sensitivity: 67% for both specifisity: 91% for Tl, 100% for MIBI (J Nucl Med 1993,34:1045)
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Recurrent tumor vs radiation necrosis
18F-FDG PET Int J Cancer 2001,96:191: 47 patients, recu
rrence after R/T Sensitivity: 75%, specificity: 81%
In our patient, MRI can not reliably distinguish recurrence from necrosis. FDG-PET, Tl and MIBI SPECT showed increased uptake.
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Recurrent tumor vs radiation necrosis
Uptake ratio in Tl and MIBI SPECT: Kosuda et al. (Tl, L/N ratio)
Recurrence: 1.7 to 12.6. All but one >2.5 Necrosis: always <=2.5 (Ann Nucl Med 1993,7:25
7)
Yamamoto et al. (L/N ratio) Cutoff value: Tl:2.40, MIBI: 5.89 accuracy: 90% (Nucl Med commun 2002,23:118
3)
Cutoff of Tl among previous reports: 1.5~2.5
In our patient, L/N ratio: Tl: 2.71, MIBI: 7.94, indicative of viable tumor.
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201Tl SPECT v.s. 18F-FDG PETBlack et al. equally good correlation with glioma grade sensitivity for recurrence: Tl:100%, PET:90.9%.
Kahn D et al.(19 pts, recurrence): ComparableOne disappointing report for PET (Am J Neuroradiol 1998)
86% and 22% (white matter); 73% and 56% (gray matter)
Difficulty in detection Low-grade tumor have metabolic activity resembling white m
atter. High-grade tumor have metabolic activity resembling gray m
atter.
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201Tl SPECT v.s. 18F-FDG PET
In our patient, Tl and MIBI SPECT offered equal information as FDG-PET.
Considering cost, availability, simplicity, ease of interpretation, SPECT should be considered in such cases.
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201Tl v.s. 99mTc-MIBIComparable in previous reportsIn our patient, the new left mesial temporal lesion is Tl(+), MIBI(-). L/N ratio of Tl: 2.67.B. BAGNI et al.: Lesions are more easily detected in frontal-parietal
area than in temporal lobes. (Nucl Med Commun 1995,16:258)
A false-negative MIBI SPECT was reported by Goethals I et al. Suggest other mechanism involved in MIBI accum
ulation. (Clin Nucl Med 2003,28:299)
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Conclusion
201Tl and 99mTc-MIBI SPECT, 18F-FDG PET provide useful information when encountering a contrast-enhancing mass on MRI in patients with previous radiation therapy for brain tumors.201Tl and 99mTc-MIBI SPECT provide equally useful information as 18F-FDG PET.
The discrepancy in the present case needs more study to survey.
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Thank you for your attention!