The effect of air cooling on the radial temperature distribution of a single microwave hyperthermia antenna<i>in vivo</i>

Bs, Trembly; Eb, Douple; Pj, Hoopes

doi:10.3109/02656739109005000

Cited by 22 publications

(4 citation statements)

References 16 publications

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“…Air cooling significantly improved the radial uniformity of the temperature distribution of single antennas or arrays [64] and the area heated to a given temperature increased by a factor of four with air cooling [65].…”

Section: Mw Antenna Coolingmentioning

confidence: 99%

Interstitial microwave transition from hyperthermia to ablation: Historical perspectives and current trends in thermal therapy

Ryan¹,

Turner

Hamilton

2010

International Journal of Hyperthermia

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This work reviews the transition from hyperthermia to ablation for cancer treatment with interstitial microwave (MW) antennas. Early work utilising MW energy for thermal treatment of cancer tissue began in the late 1970s using single antennas applied interstitially or the use of multiple interstitial antennas driven with the same phase and equal power at 915 or 2450 MHz. The original antenna designs utilised monopole or dipole configurations. Early work in thermal therapy in the hyperthermia field eventually led to utilisation of these antennas and methods for MW ablation of tumours. Efforts to boost the radiated MW power levels while decreasing antenna shaft temperatures led to incorporation of internally cooled antennas for ablation. To address larger tumours, MW treatment utilised arrays that were simultaneously activated by either non-synchronous or synchronous phase operation, benefiting both hyperthermia and ablation strategies. Numerical modelling was used to provide treatment planning guidance for hyperthermia treatments and is expected to provide a similar benefit for ablation therapy. Although this is primarily a review paper, some new data are included. These new data show that three antennas with 2.5 cm spacing at 45 W/channel and 10 min resulted in a volume of 89.8 cm(3) when operated synchronously, but only 53.4 cm(3) non-synchronously. Efficiency was 1.1 (synchronous) versus 0.7 (non-synchronous). MW systems, treatment planning, and image guidance continue to evolve to provide better tools and options for clinicians and patients in order to provide better approach and targeting optimisation with the goal of improved treatment for the patient.

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Section: Mw Antenna Coolingmentioning

confidence: 99%

Interstitial microwave transition from hyperthermia to ablation: Historical perspectives and current trends in thermal therapy

Ryan¹,

Turner

Hamilton

2010

International Journal of Hyperthermia

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“…For example, sharp-tip and helical antennas with active cooling were used in the treatment of prostate cancer [29]. Air cooling significantly improved the radial temperature uniformity for single antennas or arrays [51], and increased the area heated by a factor of four [52].…”

Section: Evolution Of Mw Antennasmentioning

confidence: 99%

Interstitial microwave treatment for cancer: historical basis and current techniques in antenna design and performance

Ryan¹,

Brace

2016

International Journal of Hyperthermia

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The use of microwaves (MW) for thermal cancer treatment began in the late 1970s. At first, hyperthermia was induced by using single antennas applied interstitially. This was followed by arrays of multiple interstitial antennas driven synchronously at 915 or 2450 MHz. This early work focused on hyperthermia as an adjuvant therapy, but more recently has evolved into a thermally ablative monotherapy. Increased power required to thermally ablate tissues required additional developments such as internally cooled antennas. Larger tumours have also been ablated with MW antenna arrays activated synchronously or non-synchronously. Numerical modelling has provided clinical treatment planning guidance and device design insight throughout this history. MW thermal therapy systems, treatment planning, navigation and image guidance continue to evolve to provide better tools and options for clinicians and patients in order to provide targeting optimisation with the goal of improved treatment for the patient and durable cancer eradication. This paper reviews the history and related technological developments, including antenna design, of MW heating for both hyperthermia and ablation.

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“…Air-cooling has previously been shown to be effective for microwave antennas. 19,20 Trembly et al demonstrated enhanced thermal penetration in vivo for an air-cooled microwave antenna with 7.5 L min Ϫ1 airflow. Previous work with catheter-cooled designs ͑water flow in a closed catheter͒ of interstitial ultrasound applicators for hyperthermia has also shown considerable improvement in FIG.…”

Section: Discussionmentioning

confidence: 99%

Air‐cooling of direct‐coupled ultrasound applicators for interstitial hyperthermia and thermal coagulation

1998

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The feasibility of using air-cooling to improve the thermal penetration of direct-coupled interstitial ultrasound (US) applicators was investigated using biothermal simulations, bench experiments, phantom testing, and in vivo thermal dosimetry. Two applicator configurations using tubular US transducers were constructed and tested. The first design, intended for simultaneous thermobrachy-therapy, utilizes a 2.5 mm OD transducer with a central lumen to accommodate a radiation source from remote afterloaders. The second applicator consists of a 2.2 mm OD transducer designed for coagulative thermal therapy. Both designs provide cooling of the inner transducer surface by the counterflow of chilled air or CO2 gas through the annulus of the enclosed applicator. The average convective heat transfer (ha) associated with each applicator was determined empirically from curve-fits of radial steady-state temperatures measured in a tissue-mimicking phantom. High levels of convective heat transfer (ha > 500 W m-2 degrees C-1) were demonstrated in both designs at relatively low flow rates (< 5 L min-1). Transient and steady-state radial heating profiles were also measured in vivo (pig thigh muscle) with and without cooling. The therapeutic radius for hyperthermia (41-45 degrees C) was extended from 5-6 mm (without cooling) to 11-19 mm with air-cooling (4.8 L min-1, airflow 10 degrees C), effectively doubling and tripling the thermal penetration in vivo. Similar improvements were demonstrated at higher temperatures with the thermal coagulation applicator. Biothermal simulations, which modeled the physical, thermal, and acoustic parameters of the air-cooled applicator and surrounding tissue, were also used to investigate potential improvements in heating patterns. The simulated radial heating profiles with transducer cooling demonstrated significantly enhanced thermal penetration over the experimental range of convective transfer, and also agreed with in vivo results. These theoretical and experimental results clearly show air-cooling controls the transducer surface temperature, significantly increases thermal penetration, and produces a greater treatment volume for direct-coupled US applicators in hyperthermia and thermal coagulation.

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The effect of air cooling on the radial temperature distribution of a single microwave hyperthermia antennain vivo

Cited by 22 publications

References 16 publications

Interstitial microwave transition from hyperthermia to ablation: Historical perspectives and current trends in thermal therapy

Interstitial microwave transition from hyperthermia to ablation: Historical perspectives and current trends in thermal therapy

Interstitial microwave treatment for cancer: historical basis and current techniques in antenna design and performance

Air‐cooling of direct‐coupled ultrasound applicators for interstitial hyperthermia and thermal coagulation

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