Assessment of Recurrent Brain Tumor by 18F-FDG PET and SPECT Using 201Tl, 99mTc-MIBI, and 99mTc-ECD

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.

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.

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.

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.

TIWI

hypointensity with heterogenous enhancement

T2WI

edema around the lesion

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.

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)

FDG-PETThallium

MIBI ECD

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.

89-4

92-8

Pre-R/T91-10

1st R/T

2ndR/T

91-10 post 1st R/T 92-8 post 2nd R/T

Thallium

MIBI

MRI (T1WI)

92-8 post 2nd R/T

T1WI C(+) Thallium

A new lesion in left mesial temporal.

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(-).

Discussion

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

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)

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.

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.

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.

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.

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)

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.

Thank you for your attention!