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ISSN: 2157-7099
Journal of Cytology & Histology
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Discrepancies of 11C-MET Uptake and MRI Contrast Enhancement in a Glioblastoma: A PET/MRI Case Report

Tian J1*, Fu L1, Yuan J2, Liu J1, Chen X2, Shi H2 and Xu B1
1Department of Nuclear Medicine, The Chinese PLA General Hospital, Fuxing Rd. 28, Beijing, 100853, China
2Department of Pathology, The Chinese PLA General Hospital, Fuxing Rd. 28, Beijing, 100853, China
*Corresponding Author : Tian J
Department of Nuclear Medicine
The Chinese PLA General Hospital
Fuxing Rd. 28, Beijing, 100853, PR China
Tel: +8610 66887329
E-mail: [email protected]
Received: December 05, 2015; Accepted: February 01, 2016; Published: February 03, 2016
Citation: Tian J, Fu L, Yuan J, Liu J, Chen X, et al. (2016) Discrepancies of 11C-MET Uptake and MRI Contrast Enhancement in a Glioblastoma: A PET/MRI Case Report. J Cytol Histol S5:003. doi:10.4172/2157-7099.S5-003
Copyright: © 2016 Tian J, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

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Abstract

A 58-year-old female patient suffered from convulsion in the left upper limb and weakness in the left lower extremity for one month. In MR contrast-enhancing (CE) images, obvious rim-enhancement was only found in the frontal nodule, while fused 11C-MET PET/MRI images showed increased MET uptake not only in the right frontal lesion but also in the body of corpus callosum. We postulated the discrepancy between MRI CE and MET uptake for the corpus callosum lesion maybe due to the following two reasons: firstly, a relative low malignant potential where absent of BBB disruption; secondly, the special affinity of MET to the oligodendroglioma. In addition, the 1H-MRS, TDI and ASL data acquired simultaneously with PET scan indicated the frontal lesion had the features of typical malignant intracranial tumor. Finally, the pathological results confirmed the frontal lesion a WHO-IV grade glioblastoma with partial anaplasia oligodendroglioma. The imaging follow-up showed a newly abnormal CE in the body of corpus callosum, which was consistent with the previous increased MET uptake on PET/MRI examination. Our case indicates that one-stop multiparametric MET-PET/MRI has advantages for the management of intracranial tumor lesions by providing complementary information.

Keywords
Glioma; MRI; PET/MRI; MET; Oncology
Introduction
In the same way in which PET/CT has been shown to be a powerful multimodality imaging tool, PET/MRI could have the following advantages: improved soft-tissue contrast; the possibility of performing truly simultaneous instead of sequential acquisitions; and the availability of sophisticated MRI sequences, such as diffusion and perfusion imaging and MR spectroscopy (MRS), which made PET/MRI is perfectly suitable for neurologic imaging [1,2]. In addition, it is well known that in most brain tumors uptake of amino acids (AA) is elevated, which is probably due to increased carriermediated transport at the blood-brain barrier (BBB), rather than to gross BBB breakdown or increased incorporation of AA into tumor issue. Thus increased uptake is also seen in most low-grade gliomas in the absence of BBB damage; this is a substantial advantage of PET with amino acids over contrast-enhancing CT, MRI and 18F-FDG [3-5]. In this case report, we presented a case of 11C-MET PET/MRI for glioblastoma, which showed the discrepancy between MET uptake and MRI contrast enhancement (CE).
Case Report
A 58-year-old Chinese female patient has a history of convulsion in the left upper limb and weakness in the left lower extremity for one month. Physical examination indicated the muscle strength deceased to III grade with cutaneous hypoesthesia. In her routine blood test and tumor marker screen, no remarkable abnormalities were reported (Figure 1). In her first MRI scan, a white matter nodule with hypointense on T1 weighted imaging (T1WI) and heterogenous hyperintense on T2-weighted image with fluid attenuation inversion recovery (T2-FLAIR) images in the right frontal lobe was detected. In addition, diffuse abnormal signal was also observed in the white matter beside the right lateral ventricle and the body of corpus callosum on T1W and T2W structure images. After Gd-DTPA based contrast agent was administrated, the obvious rim-enhancement of the frontal nodule was detected (Figure 1c).
Prior to a surgical resection of the intracranial lesion, a carbon eleven labeled methionine positron emission tomography/magnetic resonance imaging was (11C-MET PET/MRI) was suggested for the purpose of accurate diagnosis. The scan was performed on an integrated PET/MRI system (Biograph mMR, Siemens Healthcare, Erlangen, Germany) at 15 minutes after intravenous injection of 8.9mCi (329MBq) of 11C-MET and covered the whole brain. The PET data were acquired with the duration of 10 minutes and its attenuation correction was done with the build-in Ultrashort echo-time sequence, as described [2]. The MRI scanning was performed simultaneously with PET imaging with the following sequence protocol: Sagital 3D-T1- magnetization prepared rapid gradient echo (3D-T1-mprage); transverse T2-FLAIR; transverse diffusion tracking density imaging (TDI) sequence; single voxel 1H-MRS and artery spin label (ASL). No MRI contrast agent was administered. Although diffuse abnormal signal was found in a relative diffused regions, the obvious MET uptake were only observed in the lesions located at right frontal lobe and the corpus callosum with the SUVmax up to 2.76 and 2.08, respectively (Figures 1a and 1b). MRS and ASL results indicated the frontal lesion had a typical spectrum of malignant brain tumor with hyperperfusion (Figures 2a and 2b). TDI showed the decreased fiber density in the corpus callosum lesion (Figure 2c). Based on the complementary information from the multiparametric imaging, a malignant glioma was considered from MET-PET/MR examination, and the lesion in the body of corpus callosum with the feature of increased MET uptake, lack of contrast enhancement (CE) and decreased fiber density might particularly be taken more attention for clinical treatment. After tumor resection, the clinical symptoms disappeared and the pathological results confirmed the frontal lesion a WHO-IV grade glioblastoma with partial anaplasia oligodendroglioma (Figure 3). In the follow-up MRI scan which was 7 months after surgery, a newly abnormal CE was found in the body of corpus callosum, which was consistent with the previous increased MET uptake and decreased fiber density on PET/MRI examination (Figure 4).
Discussion
11C-MET has been widely used for brain tumor imaging, which uptake is greater in high-grade than in low-grade gliomas and also correlates with prognosis and survival rate [3,6-8]. It is reported that the spatial extent of increased MET uptake can be larger than that of MR CE in glioma, which may include not only solid tumor but also the surrounding zone of tumor infiltration [9,10]. In this case, the lesion located in the body of corpus callosum was observed mild MET uptake in the absence of CE. We postulated this discrepancy between two modality imagings may be due to the lesion had a biological feature of lower potential malignancy, where BBB was relatively intact. In addition, MET uptake in brain tumors has a special phenomenon, which is its uptake differed with tumor type: in oligodendrogliomas uptake tends to be higher than in astrocytomas of the same histological grade, although they are clinically somewhat less aggressive than the latter [3,6,11]. Considering the partial anaplasia oligodendroglioma detected in the final specimen, we postulates the discrepancy might also due to the special affinity of MET to the oligodendroglioma. It is noted that the lesion in the body of corpus callosum was illustrated moderate CE in the seven moths after tumor resection, which probably indicates a tumor progression.
Hybrid PET/MRI system can provide morphological and biochemical/metabolic information. In combination of PET, at the base of structural MRI sequences, advanced MRI techniques including TDI, MRS and ASL sequences were employed to provide the multiparametric biological features of the brain tumor, including the microstructure of white matter, metabolism and regional blood flow. The complementary imaging information from one-stop MET-PET/ MRI scan increased the diagnostic accuracy. Particularly, the discrepancy between MET uptake and MR CE may arouse the clinical attention but only for the determination of tumor extent for tumor resection but the prognosis and choice of following treatment, which emphasized advantages of integrated PET/MR images for the management of intracranial tumor lesions.
References

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