Validation of brain tumour imaging with p-[123I]iodo-L-phenylalanine and SPECT.
OBJECTIVE
The aims of this prospective study were to validate single-photon emission computed tomography (SPECT) with p-[(123)I]iodo-L-phenylalanine (IPA) in brain tumours and to evaluate its potential for the characterisation of indeterminate brain lesions.


METHODS
In 45 patients with indeterminate brain lesions or suspected progression of glioma, amino acid uptake was studied using IPA-SPECT and compared with the final diagnosis established by biopsy or serial imaging. After image fusion of IPA-SPECT and magnetic resonance imaging, the presence of tumour was visually determined by two independent observers. IPA uptake was quantified as the ratio between maximum uptake in the suspicious lesion and mean uptake in unaffected brain.


RESULTS
Primary brain tumours were present in 35 cases (12 low-grade and 23 high-grade gliomas). Non-neoplastic brain lesions were confirmed in seven cases (three dysplasias, three inflammatory lesions, one lesion after effective therapy). Visual analysis showed a high concordance between the two observers (kappa=0.90, p<0.001), with sensitivity and specificity of 86% and 100% for the discrimination of primary brain tumours and non-neoplastic lesions. At 30 min p.i., IPA uptake in primary brain tumours was higher than that in non-neoplastic lesions (1.70+/-0.36 vs 1.14+/-0.18, p<0.05). Brain metastases showed no increased uptake (1.13+/-0.22, n=3). The persistent retention of IPA in low-grade gliomas without disruption of the blood-brain barrier was visualised up to 24 h p.i. Low-grade and high-grade gliomas showed equivalent IPA uptake (1.72+/-0.37 vs 1.67+/-0.36 at 30 min, p=0.745).


CONCLUSIONS
IPA shows long and specific retention in gliomas. IPA is a promising and safe radiopharmaceutical for the visualisation of gliomas and the characterisation of indeterminate brain lesions.
Hellwig
Dirk
D
Department of Nuclear Medicine, Saarland University Medical Center, 66421 Homburg/Saar, Germany. Dirk.Hellwig@uniklinik-saarland.de
Ketter
Ralf
R
Romeike
Bernd F M
BF
Sell
Nadja
N
Schaefer
Andrea
A
Moringlane
Jean R
JR
Kirsch
Carl-Martin
CM
Samnick
Samuel
S
D000328:Adult; D000368:Aged; D001932:Brain Neoplasms / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010649:Phenylalanine / Q000031:analogs & derivatives*; D019275:Radiopharmaceuticals; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods*
D019275:Radiopharmaceuticals; D010649:Phenylalanine; C049181:4-iodophenylalanine