Refactor: Update Vanderbilt module variables to match OSIPI Lexicon

[Aarshpatel12]

Summary

This PR addresses Issue #106 by refactoring the Vanderbilt University Medical Center (DS_BW) module to align with the OSIPI Lexicon variable naming standards.

Changes

• Renamed parameters in src/original/DS_BW_VanderBiltUMC_USA/dcemri.py:
  • Kt -> Ktrans
  • ve -> v_e
  • vp -> v_p
• Updated test/test_DS_BW_VanderBilt.py to match the new function signatures.
• Fixed minor typos in SciPy imports (cumulative_trapezoid, curve_fit).

Dependencies

• This PR builds upon the Python 3 upgrades from PR Feat: Upgrade Vanderbilt code to Python 3 and add unit tests (Fixes #102) #139.

Verification

• Ran pytest locally.
• Result: 3 tests passed with new variable names.