In vitro calibration of a system for measurement of in vivo convective heat transfer coefficient in animals

Tangwongsan, Chanchana; Chachati, Louay; Webster, John G.; Farrell, Patrick V.

doi:10.1186/1475-925x-5-57

Cited by 5 publications

References 17 publications

(19 reference statements)

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Fast‐Response Variable‐Stiffness Magnetic Catheters for Minimally Invasive Surgery

Piskarev,

Sun,

Righi

et al. 2024

Advanced Science

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In minimally invasive surgery, such as cardiac ablation, magnetically steered catheters made of variable‐stiffness materials can enable higher dexterity and higher force application to human tissue. However, the long transition time between soft and rigid states leads to a significant increase in procedure duration. Here, a fast‐response, multisegmented catheter is described for minimally invasive surgery made of variable‐stiffness thread (FRVST) that encapsulates a helical cooling channel. The rapid stiffness change in the FRVST, composed of a nontoxic shape memory polymer, is achieved by an active cooling system that pumps water through the helical channel. The FRVST displays a 66 times stiffness change and a 26 times transition enhancement compare with the noncooled version. The catheter allows for selective bending of each segment up to 127° in air and up to 76° in water under an 80 mT external magnetic field. The inner working channel can be used for cooling an ablation tip during a procedure and for information exchange via the deployment of wires or surgical tools.

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Fast‐Response Variable‐Stiffness Magnetic Catheters for Minimally Invasive Surgery

Piskarev,

Sun,

Righi

et al. 2024

Advanced Science

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Direct thermography—a new in vitro method to characterize temperature kinetics of ablation catheters

Fiek¹,

Gindele

Bary

et al. 2013

J Interv Card Electrophysiol

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Experimental investigation of thermal effects in HIFU-based external valvuloplasty with a non-spherical transducer, using high-resolution MR thermometry

et al. 2009

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Real-time image-guided extracorporeal high intensity focused ultrasound (HIFU) has been suggested for minimally invasive treatment of valvular dysfunction in the saphenous vein. Local application of heat on the perimeter of the valve zone was previously reported to induce a partial shrinkage of the collagen, which may correct valvular function. In our study, a novel MR compatible HIFU device has been investigated. This device is based on a non-spherical geometry, with two active elements that create a focusing line which is orthogonal to the beam main axis, aiming to cover the valve longitudinally. The prototype performance was characterized by electro-acoustical measurements of the pressure field and by high-resolution MR thermometry. Pressure and thermal fields were found in good agreement with the theoretical predictions. To investigate the therapeutic potential, fresh samples of excised human veins were filled with an agarose gel, embedded in porcine muscle and exposed to HIFU. The power level applied during a fixed duration of 30 s was varied such that the absolute temperature at focus ranged between 52 degrees C and 83 degrees C. Targeting was achieved under MR guidance using a MR compatible XZ positioning system. A dedicated waterproof miniature loop coil was specifically built to achieve high-resolution MRI image-based targeting (0.25 mm x 0.25 mm x 3 mm voxel) and thermometry (0.4 mm x 0.4 mm x 4 mm voxel). The vein wall was clearly identified on MR images before and after HIFU treatment. The thermal buildup created by the non-spherical transducer could be characterized from MR thermometry data. Shrinkage of the vein wall (above 65 degrees C) was determined by absolute temperature and was not a cumulative thermal dose effect.

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In vitro calibration of a system for measurement of in vivo convective heat transfer coefficient in animals

Abstract: Background: We need a sensor to measure the convective heat transfer coefficient during ablation of the heart or liver.

Cited by 5 publications

References 17 publications

Fast‐Response Variable‐Stiffness Magnetic Catheters for Minimally Invasive Surgery

Fast‐Response Variable‐Stiffness Magnetic Catheters for Minimally Invasive Surgery

Direct thermography—a new in vitro method to characterize temperature kinetics of ablation catheters

Experimental investigation of thermal effects in HIFU-based external valvuloplasty with a non-spherical transducer, using high-resolution MR thermometry

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