title: Apparent diffusion coefficient for discriminating metastatic from non-metastatic lymph nodes in primary rectal cancer.
abstract: OBJECTIVE
  To investigate whether the apparent diffusion coefficient (ADC) could be used to discriminate metastatic from non-metastatic lymph nodes (LNs) in patients with primary rectal cancer.
  
  
  METHODS
  This study investigated 34 patients (male: 12, female: 22, mean: 62.7, range: 37-82) who underwent 1.5-T MRI with diffusion-weighted imaging (DWI) and subsequent surgical resection. A blinded radiologist measured the ADC value in each regional LN after referring to the T2-weighted images and DWI. The t-test was used to compare the mean ADC values of the metastatic and non-metastatic LNs. A ROC analysis was performed to calculate the diagnostic performance and obtain the optimal cut-off. The histopathological results were used as the reference standard.
  
  
  RESULTS
  114 LNs (46 metastatic and 68 non-metastatic) were matched and analyzed. The mean ADC of the metastatic LNs was significantly lower than that of the non-metastatic LNs (0.9 ± 0.15 × 10(-3) mm(2)/s; 1.1 ± 0.22 × 10(-3) mm(2)/s, P<0.0001). The area under the ROC curve was 0.734 (95% confidence interval, 0.644-0.812). When an ADC value of 1.0 × 10(-3) mm(2)/s was used as the cut-off, a maximum accuracy of 72% was calculated (sensitivity, 78%; specificity, 67%).
  
  
  CONCLUSIONS
  Although ADC could be used to discriminate metastatic from non-metastatic LNs, the diagnostic accuracy is approximately 70%.
authors.affiliation: Department of Radiology, Inje University College of Medicine, Haeundae Paik Hospital, Haeundae-ro 875, Haeundae-gu, Busan 612 030, Republic of Korea. Electronic address: seirosera@naver.com.
authors.forename: Een Young
authors.initials: EY
authors.lastname: Cho
authors.forename: Seung Ho
authors.initials: SH
authors.lastname: Kim
authors.forename: Jung-Hee
authors.initials: JH
authors.lastname: Yoon
authors.forename: Yedaun
authors.initials: Y
authors.lastname: Lee
authors.forename: Yun-Jung
authors.initials: YJ
authors.lastname: Lim
authors.forename: Seon-Jeong
authors.initials: SJ
authors.lastname: Kim
authors.forename: Hye Jin
authors.initials: HJ
authors.lastname: Baek
authors.forename: Choong Ki
authors.initials: CK
authors.lastname: Eun
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D002277:Carcinoma / Q000473:pathology* / Q000556:secondary*; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008198:Lymph Nodes / Q000473:pathology*; D008207:Lymphatic Metastasis; D008297:Male; D008875:Middle Aged; D012004:Rectal Neoplasms / Q000473:pathology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D016037:Single-Blind Method
keywords: Apparent diffusion coefficient; Diffusion-weighted magnetic resonance imaging; Lymph node; Lymphatic metastasis; Rectal cancer