Metabolische Bildgebung zur Verlaufskontrolle stereotaktisch bestrahlter Gliome - Wertigkeit der ¹H-MR-Spektroskopie im Vergleich zur FDG-PET und IMT-SPECT

Zusammenfassung

Fragestellung: Bestimmung der klinischen Wertigkeit der ¹H-MR-Spektroskopie (¹H-MRSI) in der Nachsorge bestrahlter Gliome im Vergleich zur FDG-PET und IMT-SPECT. Patienten und Methoden: 24 Patienten mit bestrahlten Gliomen wurden untersucht (2-D-MR spektroskopische Bildgebung; PRESS; TE = 135 ms; 1,5T Magnetom Vision, Siemens; Voxelgröße 9 × 9 × 15 mm³). MR-Spektren (insgesamt n = 233) in tumorverdächtigen Arealen (n = 86) sowie in normalem Hirnparenchym (n = 147) wurden ausgewertet. Relative Signalintensitäten von Cholin (Cho), Creatin (Cr) und N-Acetyl-Aspartat (NAA) wurden berechnet. In n = 18 Fällen wurden FDG-PET- und in n = 14 IMT-SPECT-Untersuchungen durchgeführt sowie semiquantitativ ausgewertet. Basierend auf klinischen und MRT-Verlaufskontrollen wurden die Läsionen als neoplastisch (PT) oder nichtneoplastisch (nPT) eingestuft. Ergebnisse: Richtig positive Ergebnisse für die Diagnose von PT/nPT wurden in 88/89 % (¹H-MRSI), 73/100 % (PET) und 100/75 % (SPECT) der Fälle gefunden. Cho/Cr und Cho/NAA zeigten hochsignifikante Veränderungen und konnten zwischen PT und nPT trennen. Eine Korrelation der relativen Signalintensitäten mit der FDG- und IMT-Aufnahme war aufgrund der Lokalisationen der maximalen Traceranreicherungen und Signalintensitäten nur schwer möglich. Schlussfolgerung: IMT-SPECT ist bei bestrahlten Gliomen zur Detektion eines Progresses am besten geeignet. FDG-PET ist eine sensitive Nachweismethode für höhergradige Tumoren bei gleichzeitig hoher räumlicher Auflösung. Die ¹H-MRSI kann mit ihrer guten Sensitivität und Spezifität leicht in die MRT-Untersuchung integriert werden.

Abstract

Purpose: To evaluate the clinical value of 1H MR spectroscopy (1H MRSI) for follow-up of irradiated glioma compared to positron emission tomography (PET) with [18F]-2-fluoro-deoxy-D-glucose (FDG-PET) and single photon emission tomography with [123I]-a-methyl-L-tyrosine (IMT-SPECT). Materials and Methods: Twenty-four patients with irradiated gliomas were examined using 1H MRSI (2D spectroscopic imaging; PRESS; TE = 135 msec; 1.5T Magnetom Vision, Siemens; Voxel size 9 × 9 × 15 mm³). MR spectra (n = 233) were evaluated in areas suspicious of tumor (n = 86) as well as in healthy appearing brain tissue (n = 147). Relative signal intensity ratios of choline (Cho), creatine (Cr) and N-acetyl-aspartate (NAA) were calculated. PET scans (n = 19) were performed with 200 - 250 MBq FDG, IMT-SPECT examinations (n = 14) with 200 - 250 mBq IMT. Based on clinical and MRI/CT, follow-up lesions were classified as either neoplastic [PT] or non-neoplastic [nPT]. Results: True positive results for the diagnosis of PT/nPT were 88/89 % (1H MRSI), 73/100 % (PET) and 100/75 % (SPECT). Cho/Cr showed highly significant changes for PT. Determinating a correlation between Cho, Cr, NAA and IMT-SPECT as well as FDG-PET was not possible because of different location of maximum tracer uptake and acquired 2D 1H MRSI. Conclusion: IMT-SPECT seems to be superior to detect tumor progression in irradiated gliomas. 1H MRSI was more suitable than FDG-PET to differentiate between recurrence and radiation-induced changes. FDG-PET plays a role as sensitive method for detecting high-grade tumors. PET and SPECT allowed the examination of the entire tumor including surrounding brain tissue with higher spatial resolution than the acquired 2D 1H MRSI. A main limitation of our study was that only 2D 1H MRSI was used, with only parts of the tumor evaluated. The use of 3D MR spectroscopic imaging may further increase the diagnostic accuracy.

Key words

MR spectroscopy - positron emission tomography - single photon emission tomography - brain tumor - irradiation

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