Regions of interest-based discriminant analysis of DaTSCAN SPECT and FDG-PET for the classification of dementia.

PURPOSE: Neuroimaging is increasingly used to support the clinical diagnosis of patients with cognitive impairment. Dopamine transporter (DAT) imaging, such as DaTSCAN SPECT, tests the integrity of the nigrostriatal pathway, whereas FDG-PET identifies typical patterns of cortical and subcortical hypometabolism. The aim of this study was to assess the relative contribution of DAT and regional glucose metabolism imaging to the differential diagnosis. PATIENTS AND METHODS: Twenty-seven subjects were investigated for neurodegenerative dementia associated with parkinsonism of variable severity by FDG-PET and DaTSCAN SPECT. They were grouped according to the clinically established diagnosis, including probable Alzheimer disease (5 subjects), corticobasal degeneration (6 subjects), Lewy body dementia (8 subjects), frontotemporal dementia (4 subjects), and Parkinson disease with dementia (4 subjects). Normalized FDG uptake and DAT uptake ratios were obtained by the BRASS software. We used a discriminant analysis with a stepwise method and a leave-one-out cross-validation. RESULTS: With the use of regional values of normalized FDG uptake, 85.2% and 55.6% of the patients were correctly classified by the discriminant analysis and the cross-validation, respectively. When DAT alone was considered, the results were 59.3% and 51.9%, whereas the combination of both DAT and normalized FDG uptake yielded 100% and 88.9% of accurate classifications. CONCLUSIONS: This automated analysis approach shows that the information provided by normalized FDG uptake and DAT is not redundant for the differential diagnosis of dementia and that taking into account both normalized FDG uptake and DAT uptake allows a better classification of individual patients. These results further support the usefulness of both modalities in the clinical workup of dementia.

Anatomically guided voxel-based partial volume effect correction in brain PET: impact of MRI segmentation.

Partial volume effect is still considered one of the main limitations in brain PET imaging given the limited spatial resolution of current generation PET scanners. The accuracy of anatomically guided partial volume effect correction (PVC) algorithms in brain PET is largely dependent on the performance of MRI segmentation algorithms partitioning the brain into its main classes, namely gray matter (GM), white matter (WM), and cerebrospinal fluid (CSF). A comparative evaluation of four brain MRI segmentation algorithms bundled in the successive releases of Statistical Parametric Mapping (SPM) package (SPM99, SPM2, SPM5, SPM8) using clinical neurological examinations was performed. Subsequently, their impact on PVC in (18)F-FDG brain PET imaging was assessed. The principle of the different variants of the image segmentation algorithm is to spatially normalize the subject's MR images to a corresponding template. PET images were corrected for partial volume effect using GM volume segmented from coregistered MR images. The PVC approach aims to compensate for signal dilution in non-active tissues such as CSF, which becomes an important issue in the case of tissue atrophy to prevent a misinterpretation of decrease of metabolism owing to PVE. The study population consisted of 19 patients suffering from neurodegenerative dementia. Image segmentation performed using SPM5 was used as reference. The comparison showed that previous releases of SPM (SPM99 and SPM2) result in larger gray matter regions (~20%) and smaller white matter regions (between -17% and -6%), thus introducing non-negligible bias in PVC PET activity estimates (between 30% and 90%). In contrary, the more recent release (SPM8) results in similar results (<1%). It was concluded that the choice of the segmentation algorithm for MRI-guided PVC in PET plays a crucial role for the accurate estimation of PET activity concentration. The segmentation algorithm embedded within the latest release of SPM satisfies the requirement of robust and accurate segmentation for MRI-guided PVC in brain PET imaging.

The role of interval nodes in sentinel lymph node mapping and dissection for melanoma patients.

UNLABELLED: In sentinel node (SN) biopsy, an interval SN is defined as a lymph node or group of lymph nodes located between the primary melanoma and an anatomically well-defined lymph node group directly draining the skin. As shown in previous reports, these interval SNs seem to be at the same metastatic risk as are SNs in the usual, classic areas. This study aimed to review the incidence, lymphatic anatomy, and metastatic risk of interval SNs. METHODS: SN biopsy was performed at a tertiary center by a single surgical team on a cohort of 402 consecutive patients with primary melanoma. The triple technique of localization was used-that is, lymphoscintigraphy, blue dye, and gamma-probe. Otolaryngologic melanoma and mucosal melanoma were excluded from this analysis. SNs were examined by serial sectioning and immunohistochemistry. All patients with metastatic SNs were recommended to undergo a radical selective lymph node dissection. RESULTS: The primary locations of the melanomas included the trunk (188), an upper limb (67), or a lower limb (147). Overall, 97 (24.1%) of the 402 SNs were metastatic. Interval SNs were observed in 18 patients, in all but 2 of whom classic SNs were also found. The location of the primary was truncal in 11 (61%) of the 18, upper limb in 5, and lower limb in 2. One patient with a dorsal melanoma had drainage exclusively in a cervicoscapular area that was shown on removal to contain not lymph node tissue but only a blue lymph channel without tumor cells. Apart from the interval SN, 13 patients had 1 classic SN area and 3 patients 2 classic SN areas. Of the 18 patients, 2 had at least 1 metastatic interval SN and 2 had a classic SN that was metastatic; overall, 4 (22.2%) of 18 patients were node-positive. CONCLUSION: We found that 2 of 18 interval SNs were metastatic: This study showed that preoperative lymphoscintigraphy must review all known lymphatic areas in order to exclude an interval SN.

Prediction of outcome in head-and-neck cancer patients using the standardized uptake value of 2-[18F]fluoro-2-deoxy-D-glucose.

PURPOSE: Tumor uptake of 2-[(18)F] fluoro-2-deoxy-D-glucose (FDG) may relate to outcome in cancer patients. Pretreatment FDG uptake was evaluated as a predictor of local control (LC) and disease-free survival (DFS) in patients with head-and-neck cancer managed primarily either by radiotherapy (RT) or surgery. PATIENTS AND METHODS: Tumor FDG uptake using the Standardized Uptake Value (SUV) was measured in 120 patients studied prospectively using positron emission tomography (PET). Treatment consisted of either radical RT with or without chemotherapy (73 patients) or radical surgery with or without postoperative RT (47 patients). Median follow-up of the surviving patients was 48 months. RESULTS: The median SUV was higher in 46 patients who failed treatment than in the remaining controlled patients (5.8 vs. 3.6, p = 0.002). In monovariate analysis, patients with tumors having high FDG uptake (SUV > median, 4.76) had poorer LC (p = 0.003) and DFS (p = 0.005). This difference was also observed when the RT and surgery groups were analyzed separately. In the multivariate analysis T-category (p = 0.005) and SUV (p = 0.046) remained independent adverse factors for LC, whereas N-category (p = 0.004), T-category (p = 0.02) and SUV (p = 0.05) were independent determinants of DFS. CONCLUSION: These results suggest that pretreatment tumor FDG uptake represents an independent prognostic factor in patients with head-and-neck cancers, whatever the primary treatment modality. Tumors having high FDG uptake are at greater risk of failure and should be considered for more aggressive multimodality therapy.

Standardized uptake value of 2-[(18)F] fluoro-2-deoxy-D-glucose in predicting outcome in head and neck carcinomas treated by radiotherapy with or without chemotherapy.

PURPOSE: In patients with head and neck cancer enrolled onto a prospective study of positron emission tomography (PET), pretreatment 2-[(18)F] fluoro-2- deoxy-D-glucose (FDG) uptake was evaluated as a predictor of local control and disease-free survival (DFS) after treatment by radiotherapy (RT) with or without chemotherapy. PATIENTS AND METHODS: We studied 63 patients with carcinomas of the head and neck who had an FDG-PET scan before radical RT. Tumor FDG uptake was measured with the semiquantitative standardized uptake value (SUV). All patients but one were treated with accelerated or hyperfractionated RT schedules. Thirteen patients received concomitant cisplatin-based chemotherapy. RESULTS: In 25 patients who presented with any component of treatment failure, the SUV was significantly higher than in the remaining patients without any such failure. Patients having tumors with high FDG uptake had a significantly lower 3-year local control (55% v 86%, P =.01) and DFS (42% v 79%, P =.005) compared with patients having low uptake tumors. In the multivariate analysis, the only factor that retained its significance for DFS was SUV category, whereas T category was of borderline significance. For local control, T category remained a significant factor, whereas a lower local control was observed for tumors with a high SUV compared with those with low SUV. CONCLUSION: FDG uptake, as measured by the SUV, has potential value in predicting local control and DFS in head and neck carcinomas treated by RT. High FDG uptake may be a useful parameter for identifying patients requiring more aggressive treatment approaches.