title: Respiratory-triggered versus breath-hold diffusion-weighted MRI of liver lesions: comparison of image quality and apparent diffusion coefficient values.
abstract: OBJECTIVE
  The purpose of our study was to compare respiratory-triggered and breath-hold diffusion-weighted liver MRI and to assess the agreement in the apparent diffusion co-efficient (ADC) values between the two sequences.
  
  
  METHODS
  Forty-eight patients (27 men, 21 women; mean age, 45.2 years) with focal liver lesions underwent respiratory-triggered and breath-hold diffusion-weighted MRI (DWI) in addition to routine MRI. Both sequences had identical imaging parameters except for signal averages, which were 6 in respiratory-triggered and 2 in breath-hold sequences. A total of 92 lesions (maximum of three lesions per patient; 37 benign, 55 malignant) were evaluated. Lesions were confirmed by typical imaging appearance, histopathology, or follow-up. Signal-to-noise ratio (SNR) of the liver, contrast-to-noise ratio (CNR), and relative contrast ratio of the lesions were measured in each DWI sequence and were statistically compared using the Mann-Whitney U test. The ADC values of normal liver and each category of liver lesions in the two sequences were compared for agreement using Pearson's coefficient and reliability analysis scale.
  
  
  RESULTS
  The SNR of the normal liver was significantly better on respiratory-triggered DWI than on breath-hold DWI. The mean CNR of metastases, hepatocellular carcinomas, and abscesses was significantly better in the respiratory-triggered DWI than in the breath-hold DWI sequences. The ADC values of liver and focal lesions measured by the two techniques showed good agreement. The SDs of the ADC values of normal liver were similar in the two sequences.
  
  
  CONCLUSIONS
  Respiratory-triggered DWI should be preferred over breath-hold DWI for the evaluation of focal liver lesions because it provides better image quality and SNR without any compromise in the calculated ADC values.
authors.affiliation: Department of Radiodiagnosis, All India Institute of Medical Sciences, Ansari Nagar, New Delhi 110029, India.
authors.forename: Harsh
authors.initials: H
authors.lastname: Kandpal
authors.forename: Raju
authors.initials: R
authors.lastname: Sharma
authors.forename: K S
authors.initials: KS
authors.lastname: Madhusudhan
authors.forename: Kulwant Singh
authors.initials: KS
authors.lastname: Kapoor
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D003287:Contrast Media; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D021621:Imaging, Three-Dimensional; D008113:Liver Neoplasms / Q000175:diagnosis*; D008297:Male; D008875:Middle Aged; D055425:Respiratory-Gated Imaging Techniques / Q000379:methods*; D018709:Statistics, Nonparametric
chemical_list: D003287:Contrast Media