Assessment of VP Shunt Valve Settings Using Reconstructions from Non-Contrast Head CT: A Comparative Study with Conventional Radiographs.

PURPOSE: The aim of the study was to investigate whether the ventriculoperitoneal (VP) shunt valve setting can be reliably assessed using maximum intensity projection (MIP) reconstructions from non-contrast, full-dose head CT scans, and how this method performs in comparison to conventional lateral skull radiographs.

METHODS

This retrospective study included 41 adult patients (mean age 59 ± 25 years) with Codman Certas programmable VP shunt valves who underwent lateral skull X‑ray and a same-day, non-contrast head CT scan between January and July 2024. From the CT data, MIP reconstructions of the valve region were generated. Three neuroradiologists, blinded to each other's assessments, independently rated valve settings and image quality using a 5-point Likert scale. Mean reconstruction time was recorded. Radiation dose data were extracted from institutional dose-monitoring software.

RESULTS

Valve settings were identifiable in all 44 CT/X-ray image pairs, with 95% agreement between MIP and X-ray readings. MIP reconstructions were successfully generated (median CTDIvol 35.34 mGy (30.42; 40.32); mean reconstruction time 70 s). Image quality was rated lower for MIP (median 2 [IQR 2]) than for X‑ray (median 4 [IQR 1]; p < 0.001). In 45% of cases scanned with photon-counting CT, MIP quality was significantly higher (median 3 vs. 1; p < 0.001). Inter-reader reliability was good for MIPs (ICC = 0.82) and excellent for X‑rays (ICC = 0.97).

CONCLUSION

MIP reconstructions from non-contrast head CT allow reliable VP shunt valve setting assessment and may reduce the need for additional radiographs, especially when advanced CT systems are used.