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Vascular damage
Vascular strain imaging for prevention of stroke: from bench to bedside
Stroke and transient ischemic attacks are leading causes of death and disability. They often occur without preceding clinical symptoms and are in many cases caused by the rupture of an atherosclerotic plaque in the carotid arteries. A noninvasive, patient-friendly, and inexpensive method is a prerequisite for timely detection of rupture prone plaques and prevention of stroke.
Ultrasound elastography is a method to characterize the mechanical properties of tissue by quantifying tissue deformation. Rupture-prone plaques are typically characterized by a large lipid pool that is covered from the blood by a thin fibrous cap. These plaques will deform more than stable fibrous plaques. The deformation of carotid plaques can be quantified using a linear array transducer positioned on the neck. However, since the artery is a circular structure, quantification of the deformation in all directions is required and this is not possible using conventional scanning. A compound strain imaging method to measure the deformation of plaques in carotid arteries in all directions was developed and patented (de Korte CL. Strain estimation and/or hardness imaging of tissue or tissue structures. US Patent US60708879 ). Based on this patent an NWO Vidi grant on ‘Non-invasive detection of vulnerable plaques in the carotid artery’ was awarded to de Korte in 2005. This project was carried out in collaboration with Philips Medical Systems and Samsung-Medison Ultrasound. The ultrasound machine donated for this Vidi project has been adapted for dedicated imaging sequences for the development of strain compounding in phantoms. In the first years of this project, we developed methods to accurately estimate radial strain in the carotid arterial wall based on cross-section images using vessel mimicking phantoms. For the clinical evaluation, Samsung-Medison implemented the compounding technique in two ultrasound machines. At the same time, negotiations on licensing of the patent by Samsung–Medison were started. The two machines were used for an in vivo validation study of strain compounding in collaboration with the department of Vascular Surgery of the UMC Utrecht. This study revealed a high sensitivity and specificity of compound elastography to identify atheromatous plaques (JACC Cardiovasc Imaging 2016a; Stroke 2016b). Since atheromatous plaques have all features of rupture prone plaques, this validation study warrants prospective studies to establish the predictive value of compound vascular strain imaging for the prevention of stroke. A large-scale, in vivo validation study in which compound carotid elastography in asymptomatic participants with an increased cardiovascular risk profile was compared with MRI has been executed as part of a Dutch Heart Foundation study (IN-CONTROL). This study revealed that compound strain imaging could discriminate between plaques with vulnerable and stable features. Finally, the technique is being upgraded to a full 3D techniques as part of an NWO Vici grant (de Korte 2010) and a patent has been filed to protect this innovative scanning procedure (Hansen, de Korte, Fekkes, Methods and low-cost apparatus for high resolution within breath-hold volumetric ultrasound strain elastography in arteries. US Patent pending).
Ultrasound elastography is a method to characterize the mechanical properties of tissue by quantifying tissue deformation. Rupture-prone plaques are typically characterized by a large lipid pool that is covered from the blood by a thin fibrous cap. These plaques will deform more than stable fibrous plaques. The deformation of carotid plaques can be quantified using a linear array transducer positioned on the neck. However, since the artery is a circular structure, quantification of the deformation in all directions is required and this is not possible using conventional scanning. A compound strain imaging method to measure the deformation of plaques in carotid arteries in all directions was developed and patented (de Korte CL. Strain estimation and/or hardness imaging of tissue or tissue structures. US Patent US60708879 ). Based on this patent an NWO Vidi grant on ‘Non-invasive detection of vulnerable plaques in the carotid artery’ was awarded to de Korte in 2005. This project was carried out in collaboration with Philips Medical Systems and Samsung-Medison Ultrasound. The ultrasound machine donated for this Vidi project has been adapted for dedicated imaging sequences for the development of strain compounding in phantoms. In the first years of this project, we developed methods to accurately estimate radial strain in the carotid arterial wall based on cross-section images using vessel mimicking phantoms. For the clinical evaluation, Samsung-Medison implemented the compounding technique in two ultrasound machines. At the same time, negotiations on licensing of the patent by Samsung–Medison were started. The two machines were used for an in vivo validation study of strain compounding in collaboration with the department of Vascular Surgery of the UMC Utrecht. This study revealed a high sensitivity and specificity of compound elastography to identify atheromatous plaques (JACC Cardiovasc Imaging 2016a; Stroke 2016b). Since atheromatous plaques have all features of rupture prone plaques, this validation study warrants prospective studies to establish the predictive value of compound vascular strain imaging for the prevention of stroke. A large-scale, in vivo validation study in which compound carotid elastography in asymptomatic participants with an increased cardiovascular risk profile was compared with MRI has been executed as part of a Dutch Heart Foundation study (IN-CONTROL). This study revealed that compound strain imaging could discriminate between plaques with vulnerable and stable features. Finally, the technique is being upgraded to a full 3D techniques as part of an NWO Vici grant (de Korte 2010) and a patent has been filed to protect this innovative scanning procedure (Hansen, de Korte, Fekkes, Methods and low-cost apparatus for high resolution within breath-hold volumetric ultrasound strain elastography in arteries. US Patent pending).
