title: Cellular Imaging Using Equivalent Cross-Relaxation Rate Technique in Rabbit VX-2 Tumor Model.
abstract: OBJECTIVE
  Equivalent cross-relaxation rate (ECR) imaging (ECRI) is a measurement technique that can be used to quantitatively evaluate changes in structural organization and cellular density by MRI. The aim of this study was to evaluate the correlation between the ECR value and cellular density in the rabbit VX2 tumor model.
  
  
  METHODS
  Five rabbits implanted with 10 VX2 tumors in the femur muscles were included in this study. We adopted the off-resonance technique with a single saturation transfer pulse frequency of 7 ppm downfield from water resonance. The ECR value was defined as the percentage of signal loss between the unsaturated and saturated images. ECR images were constructed based on the percentage of the ECR value. Pathological specimens were divided into 34 areas and classified into two groups: the viable group and the necrotic group. ECR values were measured and compared between groups. The correlation between the ECR value and cellular density was then determined.
  
  
  RESULTS
  The mean ECR value was significantly higher in the viable group than in the necrotic group (61.2% vs. 35.8%). The area under the curve that calculated by receiver operating characteristic curve was 0.991 at 7 ppm. The regression graph showed a linear relationship between the ECR value and cellular density; the correlation coefficient (r) was 0.858.
  
  
  CONCLUSIONS
  There is a strong association between the ECR value and cellular density in VX2 tumors and so ECRI could be a potentially useful technique for accurately depicting viable and necrotic areas.
authors.affiliation: Department of Radiology, Nara Medical University, Japan.
authors.forename: Hideyuki
authors.initials: H
authors.lastname: Nishiofuku
authors.forename: Shigeru
authors.initials: S
authors.lastname: Matsushima
authors.forename: Osamu
authors.initials: O
authors.lastname: Taguchi
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Inaba
authors.forename: Hidekazu
authors.initials: H
authors.lastname: Yamaura
authors.forename: Yozo
authors.initials: Y
authors.lastname: Sato
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Tanaka
authors.forename: Kimihiko
authors.initials: K
authors.lastname: Kichikawa