Dual-head gamma cameras operated in coincidence mode are a new approach for tumour imaging using fluorine-18 fluorodeoxyglucose (FDG). The aim of this study was to assess the diagnostic accuracy of such a camera system in comparison with a full-ring positron emission tomography (PET) system in patients with lung cancer. Twenty-seven patients (1 female, 26 males, age 62±9 years) with lung cancer or indeterminate pulmonary nodules were studied on the same day with a full-ring PET scanner (Siemens ECAT EXACT) and a coincidence gamma camera system (ADAC Vertex MCD). Sixty minutes after injection of 185–370 MBq FDG, a scan of the chest was performed with the full-ring system. Approximately 2 h p.i., the coincidence camera study was performed. Coincidence gamma camera (CGC) and PET images with (PETac) and without attenuation correction (PETnac) were analysed independently by two blinded observers. In addition, FDG uptake in primary tumours and involved lymph nodes was quantified relative to normal contralateral lung (T/L ratios). All primary tumours were histologically proven. The lymph node status was histologically determined in 23 patients. In four patients, no lymph node sampling was performed because of extensive disease or concurrent illnesses. In the 27 patients, 25 primary lung cancers and two metastatic lesions were histologically diagnosed. The number of coincidences per centimetre axial field of view was 3.33±0.93×105 for the CGC and 1.09±0.36×106 for the dedicated PET system. All primary tumours (size: 4.6±2.6 cm) were correctly identified in the CGC and dedicated PET studies. T/L ratios were 4.7±2.5 for CGC and 6.9±2.8 for PETnac (P <0.001). Histopathological evaluation revealed lymph node metastases in 11 of 88 sampled lymph node stations (size: 2.3±1.0 cm). All lymph node metastases were identified in the PETac studies, while PETnac detected 10/11 and CGC 8/11. For positive lymph nodes that were visible in CGC and PETnac studies, T/L ratios were 3.7±2.3 for CGC and 6.6±3.1 for PETnac (P=0.02). The diameters of false-negative lymph nodes in the CGC studies were 0.75, 1.5 and 2 cm. False-positive FDG uptake in lymph nodes was found in two patients with all three imaging methods. For all lesions combined, T/L ratios in CGC relative to PETnac studies decreased significantly with decreasing lesion size (r=0.62; P<0.001). In conclusion, compared with a full-ring PET system the sensitivity of CGC imaging for detection of lung cancer is limited by a lower image contrast which deteriorates with decreasing lesion size. Nevertheless, the ability of CGC imaging to detect pulmonary lesions with a diameter of at least 2 cm appears to be similar to that of a full-ring system. Both systems provide a similar specificity for the evaluation of lymph node involvement.

Purpose:The aim of this study is to evaluate the functional metabolic information provided by IMT-SPECT (I-123-alpha-methyl-tyrosin single photon computed emission tomography) for the delineation of the target volume in brain gliomas in comparison with the MRI (magnetic resonance tomography), used routinely in the 3-dimensional treatment planning of brain tumors. Materials and Methods:In 60 patients with histologically verified brain gliomas (40% glioblastoma, 47% astrocytoma grade IIl and 13% astrocytoma grade II) an IMT-SPECT and a MRI were performed pretherapeutically, in the same week.A special software system allowed the fusion between the images obtained with the both methods.The uptake of IMT was compared to contrast enhancement in T1 and to signal hyperintensity in T2 weighted images on corresponding axial slices. Results:The mean tumor volume (T2 weighted images), the mean enhancement volume (T1 weighted images with Gd) and the mean hot spot volume (IMT-SPECT) were 76 cem, 19 ccm and 44 com.The mean volume of the IMT uptake which overlaps with the tumor volume (T2) was 27 ccm and with the enhancement volume (TI+Gd) 11 ccm.IMT uptake areas outside of the tumor borders in the MRI (T2) were observed in 25% of the patients and outside of the enhancement regions (TI+Gd) in 60%.The mean uptake index of the grade 1I, Ill and IV gliomas was 1.5, 1.6 and 1.4 (no statistical significance, p>0.5). Conclusions:In a significant number of patients the IMT-SPECT investigations improve the lesion detection and delineation in the planning process.Therefore, we have started to integrate this method in a prospective dose escalation study using radiosurgery as a boost following fractionated radiation therapy and to analyse the site of the tumor regrowth relative to the chosen target volume. 2062