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Flow-sensitive MR imaging of ventriculoperitoneal shunts: in vitro findings, clinical applications, and pitfalls
M Castillo1, P A Hudgins, J A Malko
1Department of Radiology, Emory University School of Medicine, Atlanta, GA 30322.
Abstract:
To determine ventriculoperitoneal shunt patency during routine MR imaging of the head, 23 patients were studied with T1-weighted fast-field-echo scans. Without knowledge of the results of previous MR/CT studies or of the patients' clinical history, we reviewed the fast-field-echo studies and divided them according to those judged to have shunt flow (18) and those judged not to have flow (five). Fast-field-echo sequences showed high signal intensity, consistent with CSF flow and shunt patency in 17 medium-pressure systems and one high-pressure system. No signal was seen in five patients with high-pressure valve shunts. Combined clinical evaluation and MR/CT studies showed that three patients had probable shunt malfunction. One patient had true shunt malfunction; and although malfunction was thought to be present in two symptomatic patients, surgical revision showed the shunts to be patent. The possibility of temporary shunt obstruction is postulated to explain the clinical and MR findings in those two cases. The remaining two cases (9% of the patients) had no clinical evidence of shunt malfunction, and the MR findings probably reflected periodic CSF flow. One patient had an intracranial segment that was not connected and showed no flow on MR. No false-positive results (apparent flow in a nonfunctioning shunt) occurred. Using a standard medium-pressure shunt system, we constructed and imaged a phantom, which confirmed our clinical observations. T1-weighted fast-field-echo sequences may be useful in assessing patency of medium-pressure CSF shunt systems.
Insights
T1-weighted fast-field-echo MR imaging effectively assesses ventriculoperitoneal shunt patency. This technique shows high signal intensity consistent with cerebrospinal fluid flow, aiding in shunt evaluation and diagnosis.
Area of Science:
- Neurosurgery
- Radiology
- Medical Imaging
Background:
- Ventriculoperitoneal shunts are crucial for managing hydrocephalus.
- Assessing shunt patency non-invasively is essential for patient care.
- Routine magnetic resonance (MR) imaging is common for neurological conditions.
Purpose of the Study:
- To evaluate the utility of T1-weighted fast-field-echo MR sequences in determining ventriculoperitoneal shunt patency.
- To correlate MR findings with clinical assessments and other imaging modalities (MR/CT).
Main Methods:
- Twenty-three patients with ventriculoperitoneal shunts underwent head MR imaging.
- T1-weighted fast-field-echo sequences were used to assess cerebrospinal fluid (CSF) flow.
- MR findings were reviewed independently of clinical history and prior imaging results.
Main Results:
- Fast-field-echo sequences demonstrated high signal intensity, indicative of shunt flow, in 18 of 23 patients.
- Seventeen medium-pressure and one high-pressure shunt systems showed flow.
- Five patients with high-pressure valve shunts showed no signal.
- MR findings correlated well with clinical evaluations, identifying true and suspected shunt malfunctions, with a low rate of false positives.
Conclusions:
- T1-weighted fast-field-echo MR sequences show promise for assessing the patency of medium-pressure cerebrospinal fluid shunt systems.
- The technique can help differentiate between functioning and non-functioning shunts.
- Further investigation may refine its role in managing patients with shunted hydrocephalus.