Catherine Roy MD, Presenter: Nothing to Disclose

Andrea Matau, Abstract Co-Author: Nothing to Disclose

Gauthier Bazille, Abstract Co-Author: Nothing to Disclose

Remy Pasquali FRCPC, Abstract Co-Author: Nothing to Disclose

Herve Lang, Abstract Co-Author: Nothing to Disclose

To investigate the usefulness of diffusion-weighted imaging (DWI) to discriminate between metastatic and non-metastatic small lymph nodes in pelvic carcinoma.

259 patients (group I : 180 normal, group II: 79 metastatic) underwent prospectively DWI on 3T (Achieva, Philips Medical System). The group I consisted of various benign conditions : endometriosis (98 patients), leiomyomas (26 patients) or staging of prostatic carcinoma with negative laparoscopic lymphadenectomy (56 patients). The group II included 79 patients with pelvic carcinoma: prostatic carcinoma (PSA level 4 to 10 ng/mL)(16 cases), bladder carcinoma (24 cases) and gynaecological malignancies (39 patients). In addition to our routine protocol we performed an axial DW SE (TR/TE : 7000/55, 5mm, fat suppression, tf 41,EPI 41,32 slices, FOV : 120-288-340, Matrix size : 128-96,free breathing,3 min54) using b value of 0 and 1000s/mm2. ADC was measured by ROI (20 mm2). DW images were analysed by two experienced readers. We measured the short-axis diameter and the mean apparent diffusion coefficient (ADC) value. A short-axis diameter larger than 8 mm was recorded lymph nodes suspected of being metastatic. Metastatic lymph node involvement has been proven by histopathology obtained by surgery with lymph node localisation (64 patients) or CT-guided biopsy (15 patients). Imaging data were correlated station by station with histopathological 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 6.4mm ± 2.5mm and 8.3mm ± 4.5mm, respectively. All metastatic or non-metastatic nodes had similar high signal intensity on DWI with a homogeneous pattern. The mean ADC value (10-3 mm3/sec ± standard deviation) of involved lymph nodes, control iliac nodes and control inguinal nodes were, respectively, 924 ± 217 mm3/sec., 968 ± 182 mm3/sec., and 1036 ± 181 mm3/sec. There were no statistically significant differences in the ADC of metastatic and non-metastatic nodes (p=.23).

Isolated measurement of mean ADC value in a suspected small ambiguous node does not contribute to the diagnosis of metastatic nodes in pelvic carcinoma. Normal multiple pelvic lymph nodes are visible routinely on DW images.

Mean ADC value is not accurate enough to detect small pelvic metastatic node.

Roy, C, Matau, A, Bazille, G, Pasquali, R, Lang, H, Value of Diffusion-weighted (DW) MR Imaging to Detect Small Size Malignant Pelvic Lymph Nodes at 3 T in Pelvic Carcinoma.  Radiological Society of North America 2010 Scientific Assembly and Annual Meeting, November 28 - December 3, 2010 ,Chicago IL. http://archive.rsna.org/2010/9006208.html