Validation of hybrid angular spectrum acoustic and thermal modelling in phantoms

Johnson, Sara; Christensen, Douglas A.; Dillon, Christopher; Payne, Allison

doi:10.1080/02656736.2018.1513168

Cited by 11 publications

(14 citation statements)

References 67 publications

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“…This included displaced‐water measurements for density, through‐transmission measurements for determining the speed of sound of the myometrium and fibroids, and radiation force balance‐generated insertion‐loss measurements of acoustic attenuation . Based on previous experimental studies using these techniques, expected accuracy of the acoustic property measurements was 0.1 and 16% for speed of sound and acoustic attenuation measurements, respectively …”

Section: Methodsmentioning

confidence: 99%

“…[34][35][36] Based on previous experimental studies using these techniques, expected accuracy of the acoustic property measurements was 0.1 and 16% for speed of sound and acoustic attenuation measurements, respectively. 37 For all the measured properties in this study, differences between fibroid and myometrium and in vivo and ex vivo measurements were evaluated with a two-tailed Student t test, using a p-value of 0.05 to indicate statistically significant differences.…”

Section: I Acoustic Property Determinationmentioning

confidence: 99%

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A tissue preparation to characterize uterine fibroid tissue properties for thermal therapies

et al. 2019

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Purpose Treating uterine fibroids with less invasive therapies such as magnetic resonance‐guided focused ultrasound (MRgFUS) is an attractive alternative to surgery. Treatment planning can improve MRgFUS procedures and reduce treatment times, but the tissue properties that currently inform treatment planning tools are not adequate. This study aims to develop an ex vivo uterine fibroid model that can emulate the in vivo environment allowing for characterization of the uterus and fibroid MR, acoustic, and thermal tissue properties while maintaining viability for the necessary postsurgical histopathological assessments. Methods Women undergoing a hysterectomy due to fibroid‐related symptoms were invited to undergo a preoperative pelvic MRI and to permit postoperative testing of their uterine specimen. Patients that declined or could not be scheduled for a pre‐operative MRI were still able to allow post‐operative testing of their excised tissue. Following surgical removal of the uterus, nonmorcellated tissues were reperfused with a Krebs‐Henseleit buffer solution. An MR‐compatible perfusion system was designed to maintain tissue viability inside the MR suite during scanning. MR imaging protocols utilized preoperatively were repeated on whole sample, reperfused ex vivo uterus specimens. Thermal properties including thermal diffusivity and thermal conductivity of the uterus and fibroids were determined using an invasive needle sensor device in 50% of the specimens. Acoustic property measurements (density, speed of sound and attenuation) were obtained for approximately 20% of the tissue samples using both through‐transmission and radiation force balance techniques. Differences between fibroid and uterus and in vivo and ex vivo measurements were evaluated with a two‐tailed Student t test. Results Fourteen patients participated in the study and measurements were obtained from 22 unique fibroids. Of the 16 fibroids available for preoperative MRI testing, 69% demonstrated classic hypo‐intensity relative to the myometrium, with the remainder presenting with iso‐ (25%) or hyper‐intensity (6%). While thermal diffusivity was not significantly different between fibroid and myometrium tissues (0.217 ± 0.047 and 0.204 ± 0.039 mm2/s, respectively), the acoustic attenuation in fibroid tissue was significantly higher than myometrium (0.092 ± 0.021 and 0.052 ± 0.023 Np/cm/MHz, respectively). When comparing in vivo with ex vivo MRI T1 and T2 measurements in fibroids and myometrium tissue, the only difference was found in the fibroid T2 property (P < 0.05). Finally, the developed perfusion protocol successfully maintained tissue viability in ex vivo tissues as evaluated through histological analysis. Conclusions This study developed an MR‐compatible extracorporeal perfusion technique that effectively maintains tissue viability, allowing for the direct measurement of patient‐specific MR, thermal, and acoustic property values for both fibroid and myometrium tissues. These measured tissue property values will enable further development and...

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Section: Methodsmentioning

confidence: 99%

Section: I Acoustic Property Determinationmentioning

confidence: 99%

A tissue preparation to characterize uterine fibroid tissue properties for thermal therapies

et al. 2019

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“…However, whilst Modified Rayleigh-Sommerfeld integral methods accounts for refraction during the transmission of an acoustic wave through a layered structure, they do not capture multiple reflections and cannot predict scattering resulting from step changes in tissue properties. The hybrid angular spectrum approach (HAS) [9,10] extends the angular spectrum method to provide a computationally efficient alternative to full-wave ultrasound simulation methods, allowing it to cope with more complex geometries than modified Rayleigh-Sommerfeld methods [9]. However, HAS does not resolve the fullwave physics of multiple scattering and internal reflections within each https://doi.org/10.1016/j.ultras.2020.106240 medium [6,10].…”

Section: Introductionmentioning

confidence: 99%

“…The hybrid angular spectrum approach (HAS) [9,10] extends the angular spectrum method to provide a computationally efficient alternative to full-wave ultrasound simulation methods, allowing it to cope with more complex geometries than modified Rayleigh-Sommerfeld methods [9]. However, HAS does not resolve the fullwave physics of multiple scattering and internal reflections within each https://doi.org/10.1016/j.ultras.2020.106240 medium [6,10]. Such deficiencies can be addressed using full-wave models such as finite-difference time domain (FDTD) approaches [11][12][13], and k-space pseudospectral methods [5,14,15].…”

Section: Introductionmentioning

confidence: 99%

A fast full-wave solver for calculating ultrasound propagation in the body

et al. 2021

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Therapeutic ultrasound is a promising non-invasive method for inducing various beneficial biological effects in the human body. In cancer treatment applications, high-power ultrasound is focused at a target tissue volume to ablate the malignant tumour. The success of the procedure depends on the ability to accurately focus ultrasound and destroy the target tissue volume through coagulative necrosis whilst preserving the surrounding healthy tissue. Patient-specific treatment planning strategies are therefore being developed to increase the efficacy of such therapies, while reducing any damage to healthy tissue. These strategies require to use high-performance computing methods to solve ultrasound wave propagation in the body quickly and accurately. For realistic clinical scenarios, all numerical methods which employ volumetric meshes require several hours or days to solve the full-wave propagation on a computer cluster. The boundary element method (BEM) is an efficient approach for modelling the wave field because only the boundaries of the hard and soft tissue regions require discretisation. This paper presents a multiple-domain BEM formulation with a novel preconditioner for solving the Helmholtz transmission problem (HTP). This new formulation is efficient at high-frequencies and where highcontrast materials are present. Numerical experiments are performed to solve the HTP in multiple domains comprising: (i) human ribs, an idealised abdominal fat layer and liver tissue, (ii) a human kidney with a perinephric fat layer, exposed to the acoustic field generated by a high-intensity focused ultrasound (HIFU) array transducer. The time required to solve the equations associated with these problems on a single workstation is of the order of minutes. These results demonstrate the great potential of this new BEM formulation for accurately and quickly solving ultrasound wave propagation problems in large anatomical domains which is essential for developing treatment planning strategies.

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“…The HAS technique has been computationally compared to acoustic FDTD simulations, demonstrating a normalized root mean square difference of 2.8% over a 301 × 301 × 300-voxel 3D breast model [ 23 ]. Additionally, HAS-simulated pressures have been compared to experimentally obtained pressures for propagation through an ex vivo skull [ 24 ], a photopolymer aberrator [ 25 ] and homogeneous gelatin phantoms [ 26 ]. However, these studies presented beam patterns whose magnitudes were self-referenced to the maximum value of each pattern instead of absolute measurement comparisons.…”

Section: Introductionmentioning

confidence: 99%

Experimental validation of acoustic and thermal modeling in heterogeneous phantoms using the hybrid angular spectrum method

Hansen

Christensen

Payne

2021

International Journal of Hyperthermia

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Purpose: The aim was to quantitatively validate the hybrid angular spectrum (HAS) algorithm, a rapid wave propagation technique for heterogeneous media, with both pressure and temperature measurements. Methods: Heterogeneous tissue-mimicking phantoms were used to evaluate the accuracy of the HAS acoustic modeling algorithm in predicting pressure and thermal patterns. Acoustic properties of the phantom components were measured by a through-transmission technique while thermal properties were measured with a commercial probe. Numerical models of each heterogeneous phantom were segmented from 3D MR images. Cylindrical phantoms 30-mm thick were placed in the pre-focal field of a focused ultrasound beam and 2D pressure measurements obtained with a scanning hydrophone. Peak pressure, full width at half maximum, and normalized root mean squared difference (RMSDn) between the measured and simulated patterns were compared. MR-guided sonications were performed on 150-mm phantoms to obtain MR temperature measurements. Using HAS-predicted power density patterns, temperature simulations were performed. Experimental and simulated temperature patterns were directly compared using peak and mean temperature plots, RMSDn metrics, and accuracy of heating localization. Results: The average difference between simulated and hydrophone-measured peak pressures was 9.0% with an RMSDn of 11.4%. Comparison of the experimental MRI-derived and simulated temperature patterns showed RMSDn values of 10.2% and 11.1% and distance differences between the centers of thermal mass of 2.0 and 2.2 mm. Conclusions: These results show that the computationally rapid hybrid angular spectrum method can predict pressure and temperature patterns in heterogeneous models, including uncertainties in property values and other parameters, to within approximately 10%.

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Validation of hybrid angular spectrum acoustic and thermal modelling in phantoms

Cited by 11 publications

References 67 publications

A tissue preparation to characterize uterine fibroid tissue properties for thermal therapies

A tissue preparation to characterize uterine fibroid tissue properties for thermal therapies

A fast full-wave solver for calculating ultrasound propagation in the body

Experimental validation of acoustic and thermal modeling in heterogeneous phantoms using the hybrid angular spectrum method

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