PT - JOURNAL ARTICLE AU - Dirk Pauleit AU - Frank Floeth AU - Lutz Tellmann AU - Kurt Hamacher AU - Hubertus Hautzel AU - Hans-W. Müller AU - Heinz H. Coenen AU - Karl-J. Langen TI - Comparison of <em>O</em>-(2-<sup>18</sup>F-Fluoroethyl)-<span class="sc">l</span>-Tyrosine PET and 3-<sup>123</sup>I-Iodo-α-Methyl-<span class="sc">l</span>-Tyrosine SPECT in Brain Tumors DP - 2004 Mar 01 TA - Journal of Nuclear Medicine PG - 374--381 VI - 45 IP - 3 4099 - http://jnm.snmjournals.org/content/45/3/374.short 4100 - http://jnm.snmjournals.org/content/45/3/374.full SO - J Nucl Med2004 Mar 01; 45 AB - The aim of this study was to compare PET with O-(2-18F-fluoroethyl)-L-tyrosine (18F-FET) and SPECT with 3-123I-iodo-α-methyl- l-tyrosine (123I-IMT) in patients with brain tumors. Methods: Twenty patients with a suspected brain tumor were investigated by 18F-FET PET, 123I-IMT SPECT, and MRI within 3 wk. Region-of-interest analyses were performed on coregistered PET/SPECT/MRI images and the tumor-to-brain ratio (TBR), muscle-to-brain ratio (MBR), cerebellum-to-brain ratio (CerBR), and sinus-to-brain ratio (SBR) were calculated. In addition, the presence of tumor and the discrimination of anatomic structures on 18F-FET PET and 123I-IMT SPECT images were visually determined by 3 observers who were unaware of clinical data. Results: The TBR of 18F-FET and 123I-IMT uptake in cerebral tumors showed a highly significant correlation (r = 0.96; P &lt; 0.001). In the visual analysis for the presence or absence of tumors, no differences for 123I-IMT SPECT and 18F-FET PET were found in 19 of 20 patients; in one patient a low-grade glioma was only identified on 18F-FET PET images but not on 123I-IMT SPECT images. The contrast between tumor and normal brain was significantly higher in 18F-FET PET (TBR, 2.0 ± 0.9) than in 123I-IMT SPECT (TBR, 1.5 ± 0.5). The discrimination of anatomic structures yielded a significantly better score on 18F-FET PET images (rating score, 2.6 ± 0.9) compared with 123I-IMT SPECT images (rating score, 1.7 ± 0.9). The uptake of 18F-FET in the muscles was significantly higher compared with 123I-IMT (MBR 18F-FET, 1.4 ± 0.3; MBR 123I-IMT, 0.6 ± 0.2; P &lt; 0.001) and 18F-FET demonstrated a significantly higher blood-pool radioactivity than 123I-IMT (SBR 18F-FET, 1.3 ± 0.2; SBR 123I-IMT, 0.8 ± 0.2; P &lt; 0.001). Conclusion: The significant correlation of the TBRs of 18F-FET and 123I-IMT indicates that clinical experiences of brain tumor diagnostics with 123I-IMT SPECT might be valid for 18F-FET PET although substantial differences of the physiologic behavior were identified in extracerebral tissue. As 18F-FET PET allows improved discrimination of anatomic structures and the tumor-to-brain contrast was significantly superior compared with 123I-IMT SPECT scans, the results are encouraging for further evaluation of 18F-FET for imaging brain tumors.