Pulse repetition time and contrast enhancement: simulation study of Gd-BOPTA and conventional contrast agent at different field strengths

Invest Radiol. 2008 Apr;43(4):267-75. doi: 10.1097/RLI.0b013e3181636eb8.

Abstract

Objectives: To investigate theoretically enhancement and optimal pulse repetition times for Gd-BOPTA and Gd-DTPA enhanced brain imaging at 0.23, 1.5, and 3.0 T.

Methods: The theoretical relaxation times of unenhanced, conventional contrast agent (Gd-DTPA) and new generation contrast agent (Gd-BOPTA) enhanced glioma were calculated. Then, simulation of the signals and contrasts as a function of concentration and pulse repetition time (TR) in spin echo sequence was done at 0.23, 1.5, and 3.0 T. The effect of echo time (TE) on tumor-white matter contrast was also clarified. Three patient cases were imaged at 0.23 T as a test of principle.

Results: Gd-BOPTA may give substantially better glioma-to-white matter contrast than Gd-DTPA but is more sensitive to the length of TR. These characteristics are accentuated at 0.23 T. Optimal TR lengths are shorter for Gd-BOPTA than for Gd-DTPA enhanced imaging at all field strengths. TR optimized for Gd-DTPA may thus give suboptimal contrast in Gd-BOPTA enhanced imaging. Higher enhancement with Gd-BOPTA is further accentuated by short TE.

Conclusion: Appropriate TRs at 0.23 T appear to be approximately 300 to 400 milliseconds and 250 to 300 milliseconds, at 1.5 T 500 to 600 milliseconds and 400 to 450 milliseconds and at 3.0 T 550 to 650 milliseconds and 475 to 525 milliseconds using Gd-DTPA and Gd-BOPTA, respectively. For Gd-BOPTA enhanced imaging, it seems justified to optimize TR according to contrast and seek options like parallel excitation (Hadamard encoding) for increasing the number of slices and SNR.

Publication types

  • Comparative Study

MeSH terms

  • Adult
  • Brain Neoplasms / diagnosis*
  • Computer Simulation
  • Contrast Media
  • Female
  • Gadolinium DTPA*
  • Glioma / diagnosis*
  • Humans
  • Magnetic Resonance Imaging / methods*
  • Male
  • Meglumine / analogs & derivatives*
  • Middle Aged
  • Models, Theoretical
  • Organometallic Compounds*

Substances

  • Contrast Media
  • Organometallic Compounds
  • gadobenic acid
  • Meglumine
  • Gadolinium DTPA