Stability of Codman Hakim programmable valve pressure settings during 0.23 T portable magnetic resonance imaging: a prospective observational study

Background: Patients with hydrocephalus require multiple cranial imaging sessions for visualization of the ventricles following the implantation of a ventriculoperitoneal shunt (VPS) valve. However, conventional imaging methods have certain limitations: high-field-strength magnetic resonance imaging (MRI) equipment can interfere with the pressure setting of a Codman Hakim programmable valve, while mobile computed tomography (CT) exposes patients and medical staff to radiation. Low-field-strength portable MRI (pMRI) offers a safer and more convenient method for the monitoring of patients with hydrocephalus after VPS surgery. This study aimed to evaluate the stability of valve pressure setting during 0.23 T pMRI and to assess the image quality in patients with hydrocephalus. Methods: This prospective observational study involved 20 patients with hydrocephalus admitted to Zhujiang Hospital of Southern Medical University between September 2022 and September 2023. Eligible patients had hydrocephalus confirmed by recent routine imaging (1.5 T/3 T MRI or CT) and had undergone implantation of a non-MR-resistant Codman Hakim programmable valve. Participants were then subjected to pMRI (0.23 T), before and after which the valve pressure settings were verified via X-ray. Pressure stability was analyzed with the Wilcoxon signed-rank test. Image quality was evaluated through comparison of the Evans index (EI) measured on pMRI with that on standard CT (performed within 24 hours) via intraclass correlation coefficients (ICCs) and Bland-Altman analysis. Results: pretest, no significant pressure changes were observed (P=0.161). In the clinical study involving 40 pMRI sessions, the valve pressure setting remained unchanged in 30 (75.0%) sessions. Pressure deviations occurred in 10 (25.0%) sessions, but no change exceeded 20 mmH2O. There was no statistically significant difference between pre- and post-pMRI pressure settings (P=0.5552). Regarding image quality (n=22 paired scans), pMRI showed excellent agreement with CT for EI assessment, with an ICC of 0.981 [95% confidence interval (CI): 0.955-0.992; P