Metal-Free Shunt Valves and Imaging: What Defit and Decurve Offer

Defit and Decurve are DESU’s metal-free shunt valves. Both are fixed-pressure silicone valves that contain no metal and are suitable for MRI and CT. Depus valves, by contrast, use a ruby ball and titanium spring mechanism, and adjustable Depus valves are read and set with the Depus Adjustment Kit. For every valve, imaging conditions are those stated in its instructions for use.

“Metal-free” describes two of the three valve families in DESU’s shunt systems, and imaging is one input to the choice of valve. The instructions for use and the radiology department’s own implant screening remain the reference for every scan.

What does “metal-free” mean for a shunt valve?

It means the valve is made without metal components. Two DESU valve families are built this way:

• Defit: a flat-bottom silicone valve with no metal parts, offered in Ultra Small, Small and Regular sizes and in low, medium and high fixed pressures. It is compatible with MRI and CT.
• Decurve: a round burr-hole valve with a reservoir, made of polypropylene and silicone elastomer, with no metal parts. It comes in 23 mm paediatric and 28 mm adult sizes, in low, medium and high fixed pressures, and is suitable for MRI and CT.

Both are supplied as a valve or as a ventriculoperitoneal (VP) kit with a 23 cm ventricular catheter, a 120 cm peritoneal catheter, a stylet and a right-angled connector.

Why does valve material matter for imaging?

People with a shunt are often imaged many times over the years. CT and MRI are the usual ways to look at ventricle size and at the brain itself when symptoms change or as part of follow-up. Before any MRI, radiology teams screen each implant to establish whether and how the patient can be scanned.

Metal in an implant is one of the things that screening looks for, because metal can interact with the scanner’s magnetic field and can affect image quality around the device. A metal-free valve that is suitable for MRI and CT removes the valve material from that list of questions. The instructions for use remain the reference for scanning conditions, and the rest of the implanted system is screened as usual.

How does a titanium-spring valve such as Depus differ?

Depus is built differently. It has a polysulfone valve body with a ruby ball and titanium spring mechanism that opens automatically under positive ventricular pressure. Fixed Depus valves come in low, medium and high pressures, in ventriculoperitoneal and lumboperitoneal kits.

Because the mechanism includes a titanium spring, Depus is not a metal-free valve. That is a statement about materials, not about whether a Depus patient can be scanned: the conditions for imaging a patient with a Depus valve are those in its instructions for use, and teams should follow them.

What changes with an adjustable valve?

Adjustable Depus valves, in paediatric and adult sizes, add another consideration: the pressure setting. The Depus Adjustment Kit supports non-invasive adjustment with three tools:

• Locator: identifies the valve and the target directions of the pressure levels.
• Magnet: sets the valve to the target pressure.
• Compass: checks the pressure level.

Since the valve is set with a magnet, its setting is part of planning for any MRI. Teams document the current level, follow the instructions for use for scanning, and use the compass to read the level whenever those instructions call for a check. The kit is non-sterile, kept in a reusable case and offered in 3 Pressure and 5 Pressure versions. Our article on adjustable VP shunts discusses MRI planning for adjustable valves in more detail.

How do the DESU valves compare for imaging?

When might a team prefer a metal-free valve?

The valve choice is the surgeon’s. Imaging is one input among several, and a metal-free valve tends to come up when:

• Frequent or lifelong imaging is expected, as in many patients with hydrocephalus from childhood.
• A fixed pressure category is clinically acceptable, since both metal-free valves are fixed-pressure.
• The hospital prefers not to manage a valve setting around imaging appointments.
• The required shape and size are available: flat-bottom Defit in three sizes, or burr-hole Decurve in paediatric and adult sizes.

Where the surgeon wants the option of changing the pressure after implantation, an adjustable Depus valve is the route, and imaging planning follows its instructions for use. Neither option is better in the abstract; the trade-off is between a valve whose material keeps imaging simple and a valve whose setting can be changed. Patients and families can find plain-language guidance in our patient guide on living with a shunt.

What “metal-free” does not mean

• It does not mean the valve is adjustable. Defit and Decurve are fixed-pressure.
• It does not replace MRI screening. Radiology teams still check the whole implanted system and follow the instructions for use.
• It is a description of the valve. Catheters, connectors and any antisiphon device are separate components of the kit, and the kit’s documentation is the reference for them.

Antibiotic-impregnated configurations of Defit and Decurve do not change the valve’s construction. In these, the antibiotic is impregnated into the material and released in a controlled manner over 28 days.

Talk to a DESU product specialist

If imaging is a deciding factor in your valve selection, we can go through the documentation for Defit, Decurve and Depus with your team. Write to sales@desu.tr, use the contact page, or request a quote.