Abstract
OBJECTIVE: To investigate the feasibility of using modified time-of-flight magnetic resonance venography (mTOF-MRV) to evaluate the anatomical variations of the internal iliac vein (IIV). METHODS: This retrospective study included 158 patients suspected of iliac vein compression syndrome (IVCS) who underwent pelvic mTOF-MRV between June 2021 and March 2024. Fourteen patients with post-thrombotic syndrome (PTS) were excluded, leaving 144 eligible patients (52 males, 92 females; mean age 53 ± 16 years). Two radiologists independently evaluated image quality using a 4-point scale and analyzed IIV anatomical features via multiplanar reconstruction (MPR), maximum intensity projection (MIP), and volume rendering (VR) techniques. Inter-observer agreement was assessed using Cohen's kappa coefficient and intraclass correlation coefficient (ICC). RESULTS: Inter-observer agreement for image quality was good (K=0.893), and for objective measurements was excellent (ICC [95 % confidence interval]: 0.893 [0.845-0.941]). Four IIV anatomical variation types were identified: Type I (unilateral single IIV draining to ipsilateral CIV bilaterally, 30.56 %), Type II (one/both pelvic cavities with two IIVs draining to ipsilateral CIV, 55.56 %), Type III (one IIV draining to ipsilateral CIV and the other to contralateral CIV, 11.80 %), and Type IV (other variations, 2.08 %). Left CIV compression was the most common (86.11 %). CONCLUSION: The mTOF-MRV clearly visualizes IIV anatomy and variations. The proposed classification system aids preoperative planning and postoperative hemodynamic evaluation for pelvic venous disorders.