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Visualizing ventriculoperitoneal shunt valve settings with computed tomography, using extended CT scale
E Löfblad1, P E Åslund2, S Hagren1
1Uppsala University, Department of Surgical Sciences, Neuroradiology, Uppsala, Sweden.
Introduction:
Ventriculoperitoneal shunts are commonly evaluated using radiographs to confirm valve settings and catheter integrity. Although modern CT provides detailed soft tissue assessment, valve setting readouts have been unreliable due to insufficient spatial resolution and attenuation range. This study investigated whether image reconstructions with extended CT scale (ECTS) can enable reliable identification of valve settings for three common programmable shunt valve types on routine clinical CT examinations.
Methods:
Fifteen routine head CT examinations from 14 patients with programmable shunt valves (five each of Codman Hakim, Medtronic Strata and Miethke proGAV 2.0) were included. For each examination, multiple reconstructions were generated from raw data, including standard bone-kernel images and ECTS-based reconstructions. One representative image from each reconstruction was evaluated by 15 blinded reviewers, who recorded valve setting and confidence. Accuracy was assessed relative to clinically documented reference settings, with ±1 step considered an acceptable deviation.
Results:
All valve settings were correctly identified within ±1 step on ECTS reconstructions across all three valve types. ECTS significantly improved setting readout compared with standard reconstructions. Neither iterative reconstruction nor metal-artifact reduction provided additional benefit.
Conclusion:
ECTS reconstructions with a small FOV, derived from routine clinical CT head examinations, allowed reliable readout of programmable shunt valve settings for Codman Hakim, Medtronic Strata, and proGAV 2.0 valves. These findings represent an important step toward a unified CT-based approach for ventriculoperitoneal shunt evaluation.
Implications For Practice:
Head CT is commonly performed in patients with programmable shunts, often to rule out unintended valve settings or dysfunction. Every increased possibility to read the setting directly on CT, such as adding ECTS reconstructions, will directly benefit the patients through increased safety and decreased or waived need for additional projection radiography.
