Effects of spatial and temporal resolution for MR image‐guided thermal ablation of prostate with transurethral ultrasound

Pisani, Laura; Ross, Anthony B.; Diederich, Chris J.; Nau, William H.; Sommer, F. Graham; Glover, Gary H.; Butts, Kim

doi:10.1002/jmri.20339

Cited by 34 publications

(18 citation statements)

References 40 publications

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“…The temperature measurements for feedback control are acquired using MR thermometry which has limited spatial and temporal resolution, and noiselimited temperature accuracy, affecting treatment control and the heating pattern produced in tissue [60,61]. The uncertainty in temperature, T ( C), is related to the uncertainty in phase in the MR signal when using the PRF shift method.…”

Section: Mri Thermometry: Considerations For Feedback Controlmentioning

confidence: 99%

MRI-controlled transurethral ultrasound therapy for localised prostate cancer

Chopra

Burtnyk

N’Djin

et al. 2010

International Journal of Hyperthermia

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Minimally invasive treatments for localised prostate cancer are being developed with the aim of achieving effective disease control with low morbidity. High-temperature thermal therapy aimed at producing irreversible thermal coagulation of the prostate gland is attractive because of the rapid onset of thermal injury, and the immediate visualisation of tissue response using medical imaging. High-intensity ultrasound therapy has been shown to be an effective means of achieving thermal coagulation of prostate tissue using minimally invasive devices inserted into the rectum, urethra, or directly into the gland itself. The focus of this review is to describe the work done in our group on the development of MRI-controlled transurethral ultrasound therapy. This technology utilises high intensity ultrasound energy delivered from a transurethral device to achieve thermal coagulation of prostate tissue. Control over the spatial pattern of thermal damage is achieved through closed-loop temperature feedback using quantitative MR thermometry during treatment. The technology, temperature feedback algorithms, and results from numerical modelling, along with experimental results obtained in animal and human studies are described. Our experience suggests that this form of treatment is technically feasible, and compatible with existing MR imaging systems. Temperature feedback control algorithms using MR thermometry can achieve spatial treatment accuracy of a few millimetres in vivo. Patient-specific simulations predict that surrounding tissues can be spared from thermal damage if appropriate measures are taken into account during treatment planning. Recent human experience has been encouraging and motivates further evaluation of this technology as a potential treatment for localised prostate cancer.

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Section: Mri Thermometry: Considerations For Feedback Controlmentioning

confidence: 99%

MRI-controlled transurethral ultrasound therapy for localised prostate cancer

Chopra

Burtnyk

N’Djin

et al. 2010

International Journal of Hyperthermia

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“…In the simulation study, the temperature of the transurethral device was maintained at 37 C to match the in vivo conditions used experimentally. Prostate tissue was considered to undergo irreversible thermal damage when the temperature was elevated to 55 C. Since the resolution of MR thermometry measurements affects treatment accuracy [42,54,55], the numerical simulations were performed using realistic conditions for MR temperature feedback which incorporated appropriate temperature noise, spatial and temporal resolution parameters observed in previous in vivo studies, as described in Table III [46,48].…”

Section: Numerical Simulationsmentioning

confidence: 99%

Investigation of power and frequency for 3D conformal MRI-controlled transurethral ultrasound therapy with a dual frequency multi-element transducer

N’Djin

Burtnyk

Bronskill

et al. 2012

International Journal of Hyperthermia

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Transurethral ultrasound therapy uses real-time magnetic resonance (MR) temperature feedback to enable the 3D control of thermal therapy accurately in a region within the prostate. Previous canine studies showed the feasibility of this method in vivo. The aim of this study was to reduce the procedure time, while maintaining targeting accuracy, by investigating new combinations of treatment parameters. Simulations and validation experiments in gel phantoms were used, with a collection of nine 3D realistic target prostate boundaries obtained from previous preclinical studies, where multi-slice MR images were acquired with the transurethral device in place. Acoustic power and rotation rate were varied based on temperature feedback at the prostate boundary. Maximum acoustic power and rotation rate were optimised interdependently, as a function of prostate radius and transducer operating frequency. The concept of dual frequency transducers was studied, using the fundamental frequency or the third harmonic component depending on the prostate radius. Numerical modelling enabled assessment of the effects of several acoustic parameters on treatment outcomes. The range of treatable prostate radii extended with increasing power, and tended to narrow with decreasing frequency. Reducing the frequency from 8 MHz to 4 MHz or increasing the surface acoustic power from 10 to 20 W/cm(2) led to treatment times shorter by up to 50% under appropriate conditions. A dual frequency configuration of 4/12 MHz with 20 W/cm(2) ultrasound intensity exposure can treat entire prostates up to 40 cm(3) in volume within 30 min. The interdependence between power and frequency may, however, require integrating multi-parametric functions in the controller for future optimisations.

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“…Hyperthermia has been used clinically as both a stand-alone strategy and as an adjuvant for radiation therapy [49]. However, ablating tumor tissue requires high temperatures (> 43 °C) that can result in edema and necrosis in nearby tissues [50]. Although mild hyperthermia (40 °C - 43 °C) does not directly kill tissue, it has been shown to sensitize the tumor to chemotherapeutics as well as to increase vascular permeability and tumor blood flow compared with normal vasculature, thereby increasing the extravasation of macromolecules [51, 52].…”

Section: Systemic Delivery Of Elp With Local Hyperthermiamentioning

confidence: 99%

Drug delivery to solid tumors by elastin-like polypeptides

McDaniel¹,

Callahan²,

Chilkoti³

2010

Advanced Drug Delivery Reviews

190

150

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Thermally responsive elastin-like polypeptides (ELPs) are a promising class of recombinant biopolymers for the delivery of drugs and imaging agents to solid tumors via systemic or local administration. This article reviews four applications of ELPs to drug delivery, with each delivery mechanism designed to best exploit the relationship between the characteristic transition temperature (T t ) of the ELP and body temperature (T b ). First, when T t >> T b , small hydrophobic drugs can be conjugated to the C-terminus of the ELP to impart the amphiphilicity needed to mediate the self-assembly of nanoparticles. These systemically delivered ELP-drug nanoparticles preferentially localize to the tumor site via the EPR effect, resulting in reduced toxicity and enhanced treatment efficacy. The remaining three approaches take direct advantage of the thermal responsiveness of ELPs. In the second strategy, where T b < T t < 42 °C, an ELP-drug conjugate can be injected in conjunction with external application of mild hyperthermia to the tumor to induce ELP coacervation and an increase in concentration within the tumor vasculature. The third approach utilizes hydrophilic-hydrophobic ELP block copolymers that have been designed to assemble into nanoparticles in response to hyperthermai due to the independent thermal transition of the hydrophobic block, thus resulting in multivalent ligand display of a ligand for spatially enhanced vascular targeting. In the final strategy, ELPs with T t < T b are conjugated with radiotherapeutics, injtect intioa tumor where they undergo coacervation to form an injectable drug depot for intratumoral delivery. These injectable coacervate ELP-radionuclide depots display a long residence in the tumor and result in inhibition of tumor growth.

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Effects of spatial and temporal resolution for MR image‐guided thermal ablation of prostate with transurethral ultrasound

Cited by 34 publications

References 40 publications

MRI-controlled transurethral ultrasound therapy for localised prostate cancer

MRI-controlled transurethral ultrasound therapy for localised prostate cancer

Investigation of power and frequency for 3D conformal MRI-controlled transurethral ultrasound therapy with a dual frequency multi-element transducer

Drug delivery to solid tumors by elastin-like polypeptides

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