Impact of Contrast Agent Viscosity and Fallopian Tube Inner Diameter on Tubal Visualization in MR...

MR-HSG offers radiation-free multiplanar visualization for evaluating fallopian tube patency, but persistent challenges in achieving consistent high-quality visualization, particularly in smaller-diameter segments, limit clinical adoption. Previous studies modifying contrast viscosity achieved only partial improvements. This study aimed to use standardized phantom models simulating the female pelvis to systematically explore factors affecting MR-HSG image quality and provide evidence-based guidance for protocol optimization.

Nine standardized phantoms were constructed using agar gel with embedded tubes of three inner diameters (4mm, 2mm, and 1.4mm) representing ampullary, isthmic, and interstitial segments. Three contrast agents with different viscosities were tested: gadolinium-saline (2.6 mPa·s), gadolinium-iopromide (7.9 mPa·s), and gadolinium-iodixanol (8.7 mPa·s) at 37°C. T1-weighted 3D-mDIXON sequences with keyhole technology were employed on a 1.5T MRI scanner. Signal intensity measurements and qualitative assessment (good/fair/poor) were performed by blinded evaluators.

No significant differences in signal intensity were found between contrast agents of different viscosities (P>0.05). However, tube diameter significantly affected imaging quality (P<0.001). The 4 mm tubes showed the highest SI (5554.49±1042) with 100% good imaging, the 2 mm tubes showed intermediate SI (733.65±78.76) with 100% fair imaging, and the 1.4 mm tubes showed the lowest SI (444.55±34.70) with 100% poor imaging across all contrast agents.

Fallopian tube inner diameter is the primary determinant of MR-HSG imaging quality, while contrast agent viscosity (within 2.6-8.7 mPa·s range) shows no significant effect under controlled conditions. This study provides foundational data for understanding physical factors affecting MRHSG quality and suggests that anatomical factors may be more critical than contrast properties for clinical protocol optimization, potentially reducing procedure costs while maintaining diagnostic quality.

Optimizing spatial resolution to minimize partial volume effects may be more beneficial than modifying contrast agent properties for improving visualization of narrow fallopian tube segments. Clinical validation studies are warranted to confirm these findings in the complex in vivo environment.