In-Depth optimization and characterization of prostatic and penile vessel imaging with Ferumoxytol-enhanced magnetic...

Vasculogenic erectile dysfunction (ED) arises from impairment of the vascular supply to the penis and requires reliable quantitative imaging for diagnosis, management, and longitudinal monitoring, particularly after pelvic surgery or radiotherapy. Penile Doppler ultrasound is a manual examination and subject to substantial inter-observer variability in both acquisition and interpretation.

To develop and optimize a Ferumoxytol-enhanced magnetic resonance angiography (MRA) protocol for noninvasive, high-resolution imaging of prostatic and penile vasculature, and to design and implement study-specific physical and in silico phantoms for quantitative evaluation under controlled line pair, anatomically realistic, and physiological conditions.

Imaging was performed on a 1.5 T MRI scanner using T1-weighted TurboFLASH and T2-weighted turbo spin echo sequences using Ferumoxytol doses of 1-4 mg/kg. Line pair phantoms containing tubes with 0.5-6 mm inner diameter and 0.5-5 mm spacing were constructed to span the size range of prostatic and penile arteries. An anatomically derived anthropomorphic phantom was fabricated by segmenting penile vasculature from a patient CT angiogram, 3D-printing the resulting geometry, and embedding Ferumoxytol-loaded tubing to reproduce realistic vessel tortuosity. Protocol performance was assessed using signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and modulation transfer function metrics (MTF50 and MTF10). Numerical simulations were also performed to evaluate sequence behavior under flow conditions.

TurboFLASH was selected over TSE because Ferumoxytol-induced T1 shortening provided superior vessel conspicuity. Vessels larger than 1 mm were clearly visualized at all dose levels, with 2 mg/kg identified as the optimal dose. MTF50 indicated a nominal resolution of approximately 3 mm in both phantoms. MTF10 indicated effective resolutions of approximately 2 mm in the line pair phantom and 1 mm in the anthropomorphic phantom. Simulations demonstrated preserved contrast enhancement at a flow velocity of 100 mm/s.

Ferumoxytol-enhanced MRA shows promise for visualizing major prostatic and penile vessels relevant to ED diagnosis and management, including the accessory pudendal and internal pudendal arteries. Further anthropomorphic phantom refinement and in vivo patient studies are warranted to evaluate broader anatomic variability and clinical feasibility.