Cerebral staging of lung cancer: is one single contrast-enhanced T1-weighted three-dimensional gradient-echo sequence sufficient?

INTRODUCTION: Gadolinium-enhanced magnetic resonance imaging (MRI) is the gold standard for cerebral staging in thoracic oncology. We hypothesize that a minimalist examination, consisting of a single contrast-enhanced T1-weighted three-dimensional gradient-echo sequence (CE 3D-GRE), would be sufficient for the cerebral staging of nonsymptomatic lung cancer patients. METHODS: Seventy nonsymptomatic patients (50 % men; 62 years ± 10.2) referred for cerebral staging of a lung cancer were retrospectively included. All underwent a standard 3 T MRI examination with T1, FLAIR, T2* GRE, diffusion, and CE 3D-GRE sequences, for a total examination time of 20 min. The sole CE 3D-GRE (acquisition time: 6 min) was extracted and blindly interpreted by two radiologists in search of brain metastases. Hemorrhagic features of potential lesions and relevant incidental findings were also noted. Discrepant cases were reviewed by a third reader. The full MRI examination and follow-up studies were used as a reference to calculate sensitivity and specificity of the sole CE 3D-GRE. RESULTS: Thirty-eight point six percent (27 out of 70) of the patients had brain metastases. Performances and reader's agreement with the sole CE 3D-GRE sequence were excellent for the diagnosis of brain metastases (sensitivity=96.3 %, specificity=100 %, κ=0.91) and incidental findings (sensitivity=85.7 %, specificity=100 %, κ=0.62) but insufficient for the identification of hemorrhages within the metastases (sensitivity=33.3 %, specificity=85.7 %, κ=0.47). CONCLUSIONS: In the specific case of lung cancer, cerebral staging in nonsymptomatic patients can be efficiently achieved with a minimalistic protocol consisting of a single CE 3D-GRE sequence, completed if positive with a T2* sequence for hemorrhagic assessment, thus halving appointment delays.

Value of diffusion-weighted imaging to detect small malignant pelvic lymph nodes at 3 T.

OBJECTIVE: To investigate the usefulness of diffusion-weighted imaging (DWI) to discriminate between metastatic and non-metastatic small lymph nodes in pelvic carcinoma. MATERIALS AND METHODS: A total of 259 patients (180 normal, 79 metastatic) prospectively underwent DWI at 3 T. We measured the short-axis diameter and the mean apparent diffusion coefficient (ADC) value. Lymph nodes with a short-axis diameter larger than 8 mm were recorded as being suspected metastatic lymph nodes. Imaging data were correlated station by station with histopathological results. RESULTS: A total of 140 metastatic nodes were accurately matched with histology. On T2w, the short-axis diameter for non-metastatic and metastatic lymph nodes was 6.4 mm +/- 2.5 mm and 8.3 mm +/- 4.5 mm, respectively. Almost all metastatic or non-metastatic nodes had similar high signal intensity on DWI (except in 5 cases) with a homogeneous pattern. The mean ADC values (10(-3) mm(3)/s +/- standard deviation) of involved lymph nodes, control iliac nodes and control inguinal nodes were 924 +/- 217, 968 +/- 182 and 1,036 +/- 181, respectively. There were no statistically significant differences in the ADC of metastatic and non-metastatic nodes. CONCLUSION: Isolated measurement of mean ADC values in a suspected station does not contribute to the diagnosis of metastatic nodes, in patients with small ambiguous nodes.