높은 강도의 실시간 모니터링의 초음파 (HIFU) 절제를 집중<em> 체외</em> 집중 초음파에 대한 조화 운동 이미징을 사용하여 개 간을 (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
집중 초음파에 대한 조화 운동 이미징 (HMIFU)을 수행하고 높은 강도 (HIFU) 절제 초음파를 집중 모니터링 할 수있는 기술이다. 진동 운동은 함수 발생기를 사용하여 25 Hz의 진폭 변조 신호를인가하여 소자 (93) 및 4.5 MHz의 중심 주파수 HIFU 변환기의 포커스에서 생성된다. 68kPa 피크 압력 64 요소 및 2.5 MHz의 촬상 센서는 공 초점으로 무선 주파수 (RF) 채널 데이터를 취득하는 HIFU 변환기의 중앙에 배치된다. 이 프로토콜에서, 시험 관내 개과 간 7 W의 음향 파워 HIFU를 사용하여 열 삭마의 실시간 모니터링을 설명한다. HIFU 치료는 2 분 동안 조직에 도포되며, 절제 영역은 1000 프레임 / 초로 발산 또는 평면파 이미징을 사용하여 실시간으로 이미징된다. RF 채널 데이터의 매트릭스는 화상 재구성에 대한 희소 행렬에 의해 승산된다. 보기의 재구성 필드는 워싱턴을 발산 90 °이다적이 및 평면파 이미징 20mm 및 데이터는 80 MHz에서 샘플링된다. 재구성 4.5 디스플레이 프레임 레이트로 실시간으로 화상하기 위해 그래픽 처리 장치 (GPU)에 대해 수행된다. 재구성 된 RF 데이터의 1-D 정규화 상호 상관이 초점 영역에서의 축 변위를 추정하는 데 사용된다. 초점 심도의 피크 – 투 – 피크 변위 크기 때문에 병변의 형성 티슈의 강성을 나타낸다 열 절제 동안 감소한다. 평면파의 초점 영역의 변위 신호 대 잡음비 (SNR의 D) 그 평면파 촬상를 나타내는 전파를 발산에 비해 1.4 배 높았다 더 변위 웨이브 촬상 발산보다 HMIFU 품질 맵핑 생성하도록 나타난다.
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 병변의 실시간 모니터링은 적절하고 효율적인 병변 전달을 보장하는 것이 중요하다. 병변의 형태로서, 조직은 경직 및 여기 하의 움직임 진폭은 감소한다. 조직의 변위를 유도하는 음향 방 사력에 티슈 결과 영역 HIFU 적용. 변위의 상대적인 변화는 조직 강성 상대적으로 변화의 대리입니다. 이 기술은 다른 방법에 기초하여 초음파 대조 처리를 중지하지 않고 HIFU 병변을 모니터링하는 장점을 ?…
Disclosures
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 |
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