On the Detectability of Acoustic Waves Induced Following Irradiation by a Radiotherapy Linear Accelerator

Hickling, Susannah; Léger, Pierre; Naqa, Issam El

doi:10.1109/tuffc.2016.2528960

Cited by 25 publications

(26 citation statements)

References 11 publications

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“…The temperature rise distribution T ( r , t ) due to the heat source term H ( r , t ) follows the equation:

ρ C_{v} \frac{\partial T (r, t)}{\partial t} = λ {normal∇}^{2} T false(bold-italicr, t false) + H false(bold-italicr, t false)

where C v is specific heat capacity and λ is the thermal conductivity. During a single x‐ray pulse, the thermal diffusion distance d th can be evaluated by:

d_{th} = 2 \sqrt{α_{th} τ_{p}}

where α th is the thermal diffusivity (~0.15 mm 2 /s for soft tissue), and τ p is the pulse duration which is around 3–6 μs for clinic Linacs . The thermal diffusion distance is less than 2 μm during the excitation pulse, which is much smaller than the scale of spatial resolution considered in this study, and hence negligible.…”

Section: Methodsmentioning

confidence: 97%

Toward in vivo dosimetry in external beam radiotherapy using x‐ray acoustic computed tomography: A soft‐tissue phantom study validation

et al. 2018

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“…The temperature rise distribution T ( r , t ) due to the heat source term H ( r , t ) follows the equation:

ρ C_{v} \frac{\partial T (r, t)}{\partial t} = λ {normal∇}^{2} T false(bold-italicr, t false) + H false(bold-italicr, t false)

where C v is specific heat capacity and λ is the thermal conductivity. During a single x‐ray pulse, the thermal diffusion distance d th can be evaluated by:

d_{th} = 2 \sqrt{α_{th} τ_{p}}

Section: Methodsmentioning

confidence: 97%

Toward in vivo dosimetry in external beam radiotherapy using x‐ray acoustic computed tomography: A soft‐tissue phantom study validation

et al. 2018

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“…must be convolved with the temporal profile of the heating pulse, S(t) :

p false(boldr, t false) = \int_{- \infty}^{+ \infty} d t^{'} p_{δ} false(boldr, t - t^{'} false) S false(t^{'} false) .

S(t) is dependent on the source of ionizing radiation. In the case of photon beams produced by clinical linear accelerators S(t) is often rectangular in shape, while clinical synchrocyclotrons produce proton beams with Gaussian shaped pulses, both with full‐width half‐maximum lengths on the order of several microseconds.…”

Section: Theorymentioning

confidence: 99%

“…Initial studies applying XACT to linac photon beam dosimetry focused on the detection of the acoustic waves induced following the irradiation of metal blocks due to the high Grüneisen coefficient of metals and, consequently, the resulting large induced acoustic signal‐to‐noise ratio (SNR). The detection of such induced acoustic waves was demonstrated using a single element immersion transducer, a hydrophone, and a commercial diagnostic ultrasound transducer . Additionally, the effect of changing different set‐up parameters and the link between deposited dose and acoustic signal were systematically investigated and analyzed .…”

Section: Linac Photon Beam Dosimetrymentioning

confidence: 99%

“…The detection of such induced acoustic waves was demonstrated using a single element immersion transducer, a hydrophone, and a commercial diagnostic ultrasound transducer . Additionally, the effect of changing different set‐up parameters and the link between deposited dose and acoustic signal were systematically investigated and analyzed . During this time, a comprehensive computer simulation workflow combining Monte Carlo dose calculations and acoustic wave transport techniques was developed to guide experimental investigations in this area.…”

Section: Linac Photon Beam Dosimetrymentioning

confidence: 99%

“…During this time, a comprehensive computer simulation workflow combining Monte Carlo dose calculations and acoustic wave transport techniques was developed to guide experimental investigations in this area. This simulation tool was validated experimentally using simple geometries with metal block measurements …”

Section: Linac Photon Beam Dosimetrymentioning

confidence: 99%

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Ionizing radiation‐induced acoustics for radiotherapy and diagnostic radiology applications

et al. 2018

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Acoustic waves are induced via the thermoacoustic effect in objects exposed to a pulsed beam of ionizing radiation. This phenomenon has interesting potential applications in both radiotherapy dosimetry and treatment guidance as well as low-dose radiological imaging. After initial work in the field in the 1980s and early 1990s, little research was done until 2013 when interest was rejuvenated, spurred on by technological advances in ultrasound transducers and the increasing complexity of radiotherapy delivery systems. Since then, many studies have been conducted and published applying ionizing radiation-induced acoustic principles into three primary research areas: Linear accelerator photon beam dosimetry, proton therapy range verification, and radiological imaging. This review article introduces the theoretical background behind ionizing radiation-induced acoustic waves, summarizes recent advances in the field, and provides an outlook on how the detection of ionizing radiationinduced acoustic waves can be used for relative and in vivo dosimetry in photon therapy, localization of the Bragg peak in proton therapy, and as a low-dose medical imaging modality. Future prospects and challenges for the clinical implementation of these techniques are discussed.

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Experimental evaluation of x‐ray acoustic computed tomography for radiotherapy dosimetry applications

et al. 2017

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Purpose: The aim of this work was to experimentally demonstrate the feasibility of x-ray acoustic computed tomography (XACT) as a dosimetry tool in a clinical radiotherapy environment. Methods: The acoustic waves induced following a single pulse of linear accelerator irradiation in a water tank were detected with an immersion ultrasound transducer. By rotating the collimator and keeping the transducer stationary, acoustic signals at varying angles surrounding the field were detected and reconstructed to form an XACT image. Simulated XACT images were obtained using a previously developed simulation workflow. Profiles extracted from experimental and simulated XACT images were compared to profiles measured with an ion chamber. A variety of radiation field sizes and shapes were investigated. Results: XACT images resembling the geometry of the delivered radiation field were obtained for fields ranging from simple squares to more complex shapes. When comparing profiles extracted from simulated and experimental XACT images of a 4 cm 9 4 cm field, 97% of points were found to pass a 3%/3 mm gamma test. Agreement between simulated and experimental XACT images worsened when comparing fields with fine details. Profiles extracted from experimental XACT images were compared to profiles obtained through clinical ion chamber measurements, confirming that the intensity of XACT images is related to deposited radiation dose. Seventy-seven percent of the points in a profile extracted from an experimental XACT image of a 4 cm 9 4 cm field passed a 7%/4 mm gamma test when compared to an ion chamber measured profile. In a complicated puzzle-piece shaped field, 86% of the points in an XACT extracted profile passed a 7%/4 mm gamma test. Conclusions: XACT images with intensity related to the spatial distribution of deposited dose in a water tank were formed for a variety of field sizes and shapes. XACT has the potential to be a useful tool for absolute, relative and in vivo dosimetry.

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On the Detectability of Acoustic Waves Induced Following Irradiation by a Radiotherapy Linear Accelerator

Cited by 25 publications

References 11 publications

Toward in vivo dosimetry in external beam radiotherapy using x‐ray acoustic computed tomography: A soft‐tissue phantom study validation

Toward in vivo dosimetry in external beam radiotherapy using x‐ray acoustic computed tomography: A soft‐tissue phantom study validation

Ionizing radiation‐induced acoustics for radiotherapy and diagnostic radiology applications

Experimental evaluation of x‐ray acoustic computed tomography for radiotherapy dosimetry applications

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