Yüksek Yoğunluk Gerçek zamanlı izleme Ultrason (HIFU) Ablasyonu Odaklı<em> İn Vitro</em> Odaklı Ultrason Harmonik Hareket Görüntüleme kullanma Köpek karaciğerler (HMIFU)
Summary
This article describes real-time monitoring of HIFU ablation in canine liver with high frame rate ultrasound imaging using diverging and plane wave imaging. Harmonic Motion Imaging for Focused Ultrasound is used to image the decrease of acoustic radiation force induced displacement in the ablated region.
Abstract
Odaklı Ultrason Harmonik Hareket Görüntüleme (HMIFU) gerçekleştirmek ve yüksek yoğunluklu (HIFU) ablasyon odaklanmış ultrason izleyebilirsiniz bir tekniktir. Bir salınım hareketi fonksiyon jeneratörü kullanılarak 25 Hz genlik modülasyonlu sinyal uygulayarak 93-elemanı ve 4.5 MHz merkez frekansı HIFU dönüştürücünün odağı oluşturulur. 68kPa tepe basıncı ile 64 eleman ve 2.5 MHz transdüser görüntüleme odaksal radyo frekans (RF) kanal verilerini elde etmek için HIFU transdüser merkezinde yer almaktadır. Bu protokol, in vitro olarak, köpek Karaciğerlerde 7 W akustik güç ile HIFU kullanan termal ablasyon gerçek zamanlı izleme tarif edilmektedir. HIFU tedavisi 2 dakika boyunca dokuya uygulanır ve ablasyon bölgesi 1000 kare / saniyeye kadar konuyu farklı açılardan ya da düzlem dalga görüntüleme kadar kullanarak gerçek zamanlı olarak görüntülü. RF kanal veri matrisi görüntü oluşturmak için seyrek bir matris ile çarpılır. Görüş yeniden alan wa ayrılan 90 ° olduğuA.Ş. ve düzlemsel dalga görüntüleme için 20 mm ve veri 80 MHz'de örneklenir. Rekonstrüksiyon 4.5 ekran kare hızında gerçek zamanlı görüntü için Grafiksel Processing Unit (GPU) üzerinde yapılır. Yeniden RF veri 1-D normalleştirilmiş çapraz-korelasyon fokal bölgesinde bulunan eksensel yer değiştirmeleri tahmin etmek için kullanılır. Odak derinliği tepe-tepe yer değiştirme büyüklüğü nedeniyle lezyonun oluşumuna doku sertleşme anlamına gelir ısı ablasyon sırasında azalır. Düzlem dalga için odak alanında deplasman sinyal-gürültü oranı (SNR d) düzlem dalga görüntüleme gösteren dalga ayrılan nazaran 1.4 kat daha fazlaydı iyi deplasman dalga görüntüleme ayrılan daha HMIFU kalitesini haritalar üretmek gibi görünüyor.
Introduction
High Intensity Focused Ultrasound (HIFU) is a technique that generates temperature elevation at the focal region and can be used to ablate cancerous tissue 1. Temperature elevation at the focus causes thermal lesions in the tissue 2. In order to avoid overtreating a region and to reduce treatment duration, it is imperative to reliably monitor the ablation. Magnetic resonance-guided focused ultrasound (MRgFUS) is the main technique used in clinic to guide and monitor HIFU treatment 3. MRI provides high spatial resolution images of the treated region with tissue displacement or thermal dose but has a frame rate of 0.1-1 Hz and is costly. Several ultrasound-based techniques such as B-mode imaging 4, passive acoustic mapping 5, shear wave imaging 6 and acoustic radiation force impulse 7 have been developed to guide and monitor thermal ablation. However, B-mode imaging and passive acoustic mapping do not provide imaging of mechanical properties of the ablated region which is useful to the operator to improve lesion delivery.
Shear wave imaging and acoustic radiation force impulse can both characterize the elasticity of the tissue by measuring acoustic radiation force-induced displacements 7,8. However, in both methods, the HIFU treatment is typically interrupted to monitor the ablation. Our group has developed a technique called Harmonic Motion Imaging for Focus Ultrasound (HMIFU) which can monitor the HIFU treatment with ultrasound without stopping the ablation9,10. Briefly, a HIFU transducer sends an amplitude-modulated wave to the region to ablate while simultaneously generating an oscillatory motion in the focal region. A co-axially aligned ultrasound transducer is used to image this oscillation. The magnitude of the induced motion is related to the stiffness of the tissue.
To ensure proper lesion delivery, the temporal resolution of real-time monitoring is of key interest in ablation guidance. Recently, our group has shown real-time streaming of displacement at a frame rate up to 15 Hz, imaged with diverging waves in a narrow field of view and using a fast image reconstruction method 11. Several beamforming techniques can be used to image the displacements. A large field of view can be obtained with diverging wave imaging by changing the delay profile but the axial direction is not aligned with the HIFU beam on the lateral regions and the wave is attenuated due to geometric spreading in the lateral direction, which can affect the quality of the displacement estimation. In contrast, the lateral field of view for plane wave is upper bounded by the active aperture but the axial direction is aligned with the HIFU beam at the focus and there is no geometric spreading in the lateral direction. Depending on the type of application, one or the other imaging method can be selected. The objectives of this protocol are to show how plane wave imaging can provide real-time streaming of displacements images using HMIFU during ablation and to compare the quality of the motion estimation between diverging and plane wave imaging.
Protocol
Representative Results
Discussion
HIFU lezyonlarının Gerçek zamanlı izleme, uygun ve verimli bir lezyon teslimini sağlamak için önemlidir. Lezyon formları gibi, doku sertleşir ve uyarma altında hareket genliği azalır. Doku değiştirmesini uyaran bir akustik radyasyon yürürlükte doku sonuçları bir bölgede HIFU uygulanması. Yerinden göreceli değişim doku sertliği göreli bir değişim vekil olduğunu. Bu teknik, diğer ultrason tabanlı yöntemlerin aksine tedavi durmadan HIFU'nun lezyonu takip avantajını sunmaktadır. Bu ça…
Declarações
The authors have nothing to disclose.
Acknowledgements
This work was supported by the National Institutes of Health (R01-EB014496). The authors would like to thank Iason Apostolakis for his contribution to the experiments.
Materials
| P4-2 Phased array | ATL | ||
| H-178 HIFU transducer | Sonic Concepts | ||
| 3-D positioner | Velmex Inc. | ||
| AT33522A function generator | Agilent Technologies | ||
| V-1 ultrasound system | Verasonics | ||
| 3100L RF amplifier | ENI | ||
| Matching network | Sonic Concepts | ||
| Degasing system | Sonic Concepts | ||
| Programming software | Matlab | ||
| Jacket software package | Accelereyes |
Referências
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