title: Adrenal masses: correlation between CT attenuation value and chemical shift ratio at MR imaging with in-phase and opposed-phase sequences.
abstract: OBJECTIVE
  To correlate attenuation values at computed tomography (CT) with signal intensity at chemical-shift magnetic resonance (MR) imaging in adrenal masses.
  
  
  METHODS
  Thirty-eight patients with 47 adrenal lesions underwent MR imaging and unenhanced CT examinations. MR examinations, performed at 1.5 T, included T1-weighted imaging with fat and water in phase and gradient-echo imaging with fat and water out of phase (repetition time, 45-180 msec; echo time, 1.4-3.1 msec). Lesion-to-spleen signal intensity ratios were calculated for the in-phase and opposed-phase images. The chemical-shift ratio, a measure of signal intensity loss between in-phase and opposed-phase images, and the CT attenuation value (in Hounsfield units) were determined for each lesion.
  
  
  RESULTS
  A statistically significant correlation (0.85) was found between attenuation and chemical-shift-ratio values (P < .000001). Attenuation in six benign lesions was within 2 standard deviations of the mean attenuation in malignant lesions, and the chemical-shift ratio in eight benign lesions was within 2 standard deviations of the mean chemical-shift ratio in malignant lesions. Six of these eight lesions were misclassified on the basis of both attenuation and chemical-shift-ratio values.
  
  
  CONCLUSIONS
  CT attenuation values are highly correlated with chemical-shift ratios. Both values were indeterminate for a similar subset of benign lesions.
authors: Department of Radiology, Thomas Jefferson University Hospital, Philadelphia, PA 19107, USA.
authors: E K
authors: EK
authors: Outwater
authors: E S
authors: ES
authors: Siegelman
authors: A B
authors: AB
authors: Huang
authors: B A
authors: BA
authors: Birnbaum
mesh_terms: D000310:Adrenal Gland Neoplasms / Q000175:diagnosis*; D000311:Adrenal Glands / Q000000981:diagnostic imaging* / Q000378:metabolism; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D009682:Magnetic Resonance Spectroscopy / Q000295:instrumentation / Q000379:methods; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed / Q000295:instrumentation / Q000379:methods / Q000706:statistics & numerical data