PURPOSE: To prospectively compare positron emission tomography (PET) imaging of regional lymph node basins to sentinel node biopsy (SNB) in patients with American Joint Committee on Cancer (AJCC) stage I, II, and III melanoma localized to the skin. METHODS: Patients with cutaneous melanoma with Breslow's depth greater than 1 mm (AJCC T2-4N0M0) or localized regional cutaneous recurrence (TxN2bM0) underwent whole-body imaging of glucose metabolism with fluorodeoxyglucose (FDG) PET followed by SNB. PET scans were interpreted in a blinded fashion and compared with histologic analyses of SNB specimens and clinical follow-up examination. Nodal tumor volumes were estimated. RESULTS: Eighty-nine lymph node basins were evaluated by FDG-PET and SNB in 70 assessable patients. Eighteen patients (25.7%) had lymph node metastases at the time of FDG-PET imaging: 17 proved by SNB (24.3%) and one by follow-up examination (1.4%). Median tumor volume in positive sentinel node basins was 4.3 mm3 (range, 0.07 to 523 mm3). Sensitivity of SNB for detection of occult regional lymph node metastases was 94.4%, specificity was 100%, positive predictive value (PPV) was 100%, and negative predictive value (NPV) was 98.6%. Sensitivity of FDG-PET was 16.7%, specificity was 95.8%, PPV was 50%, and NPV was 81.9%. At a median follow-up duration of 16.6 months, seven patients (10%) developed recurrent disease. PET predicted one recurrence (14.3%) in a node basin missed by SNB. CONCLUSION: FDG-PET is an insensitive indicator of occult regional lymph node metastases in patients with melanoma because of the minute tumor volumes in this population. FDG-PET does not have a primary role for staging regional nodes in patients with clinically localized melanoma.

No abstract

Objective Selective focal MR‐Signal (diffusion‐) changes in the CA‐1 sector of the hippocampus have been described in transient global amnesia (TGA), but the pathophysiological substrate of these lesions is largely unknown. As several imaging and epidemiological findings point to a vascular origin an analysis of the temporal evolution of the hippocampal apparent diffusion coefficient (ADC) changes may offer new understanding of the pathomechanisms of TGA. Methods The time course of the ADC of hippocampal DWI lesions in TGA patients was studied using serial 3 T high‐resolution MR‐imaging within 1‐10 days as well as 4‐6 months after TGA. ADC values from 76 MR‐studies were analyzed and expressed as ratio ADC (rADC) in reference to the unaffected hemisphere. Results Twenty‐nine patients with TGA showed 34 DWI lesions with corresponding T2 lesions in the CA‐1 sector of the hippocampal cornu ammonis within a time window of 24‐72 h after onset. Ratio ADC decreased below 1.0 (0.66 ± 0.08) 24 h after the acute TGA episode and did show a further significant decrease to 0.57 ± 0.1 after 3 days (p < 0.05). After 72 h, rADC increased and normalized around day 10 with rADC values of 1.0 (p < 0.05). Interpretation The temporal evolution of the rADC in hippocampal signal changes in TGA shows a time course previously described for ischemic lesions in human stroke patients. This might imply a vascular origin of diffusion changes leading to a transient perturbation of memory relevant circuits in the hippocampus. Ann Neurol 2007

No abstract

FDG-PET reliably detects lymph node tumor deposits greater than approximately 80 mm(3) volume, but sensitivity falls rapidly below this. This amount of tumor is most likely to occur in patients with AJCC stage III or IV disease.