Larson T R, Blute M L, Tri J L, Whitlock S V
Department of Urology, Mayo Clinic, Scottsdale, Arizona, USA.
Urology. 1998 Jun;51(6):908-15. doi: 10.1016/s0090-4295(98)00142-3.
To determine the design and performance characteristics of two microwave antennae for use in thermal treatment of benign prostatic hyperplasia.
Prostatron and Targis antennae were subjected to detailed physical examination and measurement. The heating patterns generated by these two types of antennae were characterized in detail using tissue-equivalent phantoms. Measurements of return loss as a function of frequency were conducted to evaluate the capacity of the antennae for impedance matching. Percent reflected power was calculated from the return loss results to provide a relative measure of potential for efficient delivery of thermal energy.
The Prostatron antenna was found to be a monopole design consisting of a coaxial cable with a 3.3-cm length of inner conductor exposed at the tip. The Targis antenna was observed to be a dipole design with a 2.8-cm helical coil attached through a ground connection and a tap point to a coaxial cable. The heating pattern of the Targis antenna was symmetric; that of the Prostatron was asymmetric with substantial back heating along the catheter axis in the direction of the microwave power source. The mean extension of the 30 degrees C isotherm in the direction of the power source with the Prostatron antenna (71.5 mm; 95% confidence interval [CI], 63.4 to 79.6 mm) was 55% greater (P < 0.0005) than that with the Targis antenna (46.0 mm; 95% CI, 38.2 to 53.8 mm). Return loss with the Targis antenna declined sharply to a relative minimum value of -32.9 dB (95% CI, -73.8 to 8.0 dB) at 915 MHz, providing evidence of this antenna's capacity for impedance matching; little change was observed with the Prostatron in return loss over a frequency range 100 MHz above and below this antenna's standard operating frequency of 1296 MHz. The mean reflected power of the Targis antenna (0.4%; 95% CI, 0.0% to 1.4%) was lower by more than 20-fold (P = 0.036) than that of the Prostatron antenna (11.0%; 95% CI, 3.4% to 18.7%); thus, the potential for efficient operation was greater with the Targis than the Prostatron antenna.
The Targis microwave antenna was found to provide a more targeted heating pattern and have a capacity for more efficient thermal energy delivery than the Prostatron antenna. These differences observed in vitro could potentially translate into clinical advantages in vivo, such as improved tolerability of microwave treatment, reduced risk of complications, greater thermoablative efficacy, and scalability.
确定用于良性前列腺增生热疗的两种微波天线的设计和性能特征。
对Prostatron和Targis天线进行详细的物理检查和测量。使用组织等效体模详细表征这两种天线产生的加热模式。测量回波损耗随频率的变化，以评估天线的阻抗匹配能力。根据回波损耗结果计算反射功率百分比，以提供热能有效传输潜力的相对度量。
发现Prostatron天线为单极设计，由一根同轴电缆组成，其尖端露出3.3厘米长的内导体。观察到Targis天线为偶极设计，通过接地连接和一个分接点连接到同轴电缆上的一个2.8厘米螺旋线圈。Targis天线的加热模式是对称的；Prostatron天线的加热模式是不对称的，沿导管轴朝着微波电源方向有大量的反向加热。使用Prostatron天线时，30℃等温线在电源方向上的平均延伸（71.5毫米；95%置信区间[CI]，63.4至79.6毫米）比使用Targis天线时（46.0毫米；95%CI，38.2至53.8毫米）大55%（P<0.0005）。Targis天线的回波损耗在915兆赫时急剧下降至相对最小值-32.9分贝（95%CI，-73.8至8.0分贝），证明了该天线的阻抗匹配能力；在Prostatron天线高于和低于其1296兆赫标准工作频率100兆赫的频率范围内，回波损耗变化不大。Targis天线的平均反射功率（0.4%；95%CI，0.0%至1.4%）比Prostatron天线（11.0%；95%CI，3.4%至18.7%）低20多倍（P = 0.036）；因此，Targis天线比Prostatron天线具有更高的高效运行潜力。
发现Targis微波天线比Prostatron天线提供更有针对性的加热模式，并且具有更高效的热能传输能力。在体外观察到的这些差异可能会转化为体内的临床优势，如提高微波治疗的耐受性、降低并发症风险、提高热消融疗效和可扩展性。
