Imperial College London
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Professor Hashim Ahmed

Faculty of Medicine, Department of Surgery & Cancer

Chair in Urology (Clinical)
 
 
 
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Contact

 

hashim.ahmed

 
 
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Location

 

5L28Lab BlockCharing Cross Campus

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Summary

 

Publications

Citation

BibTex format

@article{Georgiou:2017:10.1002/mp.12044,
author = {Georgiou, PS and Jaros, J and Payne, H and Allen, C and Shah, TT and Ahmed, HU and Gibson, E and Barratt, D and Treeby, BE},
doi = {10.1002/mp.12044},
journal = {Medical Physics},
pages = {679--693},
title = {Beam distortion due to gold fiducial markers during salvage high-intensity focused ultrasound in the prostate},
url = {http://dx.doi.org/10.1002/mp.12044},
volume = {44},
year = {2017}
}
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RIS format (EndNote, RefMan)

TY  - JOUR
AB  - Purpose: High intensity focused ultrasound (HIFU) provides a non-invasive salvage treatmentoption for patients with recurrence after external beam radiation therapy (EBRT). As part of EBRTthe prostate is frequently implanted with permanent fiducial markers. To date, the impact of thesemarkers on subsequent HIFU treatment is unknown. The objective of this work was to systematicallyinvestigate, using computational simulations, how these fiducial markers affect the delivery of HIFUtreatment.Methods: A series of simulations was performed modelling the propagation of ultrasound pressurewaves in the prostate with a single spherical or cylindrical gold marker at different positions andorientations. For each marker configuration, a set of metrics (spatial-peak temporal-average intensity,focus shift, focal volume) was evaluated to quantify the distortion introduced at the focus. An analyticalmodel was also developed describing the marker effect on the intensity at the focus. The modelwas used to examine the marker's impact in a clinical setting through case studies.Results: The simulations show that the presence of the marker in the pre-focal region causes reflectionswhich induce a decrease in the focal intensity and focal volume, and a shift of the maximumpressure point away from the transducer's focus. These effects depend on the shape and orientation ofthe marker and become more pronounced as its distance from the transducer's focus decreases, withthe distortion introduced by the marker greatly increasing when placed within 5 mm of the focus.The analytical model approximates the marker's effect and can be used as an alternative method tothe computationally intensive and time consuming simulations for quickly estimating the intensity atthe focus. A retrospective review of a small patient cohort selected for focal HIFU after failed EBRTindicates that the presence of the marker may affect HIFU treatment delivery.Conclusions: The distortion introduced by the marker to the HIF
AU  - Georgiou,PS
AU  - Jaros,J
AU  - Payne,H
AU  - Allen,C
AU  - Shah,TT
AU  - Ahmed,HU
AU  - Gibson,E
AU  - Barratt,D
AU  - Treeby,BE
DO  - 10.1002/mp.12044
EP  - 693
PY  - 2017///
SN  - 0094-2405
SP  - 679
TI  - Beam distortion due to gold fiducial markers during salvage high-intensity focused ultrasound in the prostate
T2  - Medical Physics
UR  - http://dx.doi.org/10.1002/mp.12044
UR  - http://hdl.handle.net/10044/1/53560
VL  - 44
ER  -
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