Ryan T P, Taylor J H, Coughlin C T
Department of Medicine, Dartmouth-Hitchcock Medical Center, Hanover, NH 03756.
Int J Radiat Oncol Biol Phys. 1992;23(1):189-99. doi: 10.1016/0360-3016(92)90560-5.
A vaginal obturator was fabricated to be used in combination with implanted catheters to provide microwave hyperthermia and brachytherapy to the vulva and vaginal wall. This site is difficult to heat or irradiate solely with interstitial techniques. The obturator was modified to provide grooves for the mounting of interstitial catheters into the outer wall and was matched with a template for circumferential implants. Power deposition tests were done using arrays of three microwave antenna designs: dipole (hA = hB = 3.9 cm), helical (3.9 cm coil, shorted), and modified dipole (1.0 cm helix on dipole tip) to test the performance of the obturator. The obturator and four non-obturator catheters were positioned in muscle-equivalent phantom. Two obturator catheters along with two free-standing catheters formed the obturator array. Four freestanding catheters formed the non-obturator array. Power deposition or specific absorption rate (SAR) measurements were made along the central axis, bisect, and diagonal transect of each array. SAR results showed that antennas in the obturator wall radiated as dipole theory predicts, although with less power density when compared to antennas in the same catheters spaced 1.8 cm from the obturator. This could be compensated for by increasing the power to the antennas in the obturator by 42%. Adjacent pairs of antennas were placed 90 degrees out of phase for 0.25 sec and rotated around the array. Phase rotation demonstrated that the central array SAR peaks could be lowered from 100% to 50% SAR, with dipole antennas thus resulting in lowered peak temperatures and the ability to heat larger volumes by improving the distribution of power. With helical antennas, there was 50% SAR at the array center when operated coherently without phase rotation. Three patients were treated with the obturator and a custom-made template using dipole antennas, and temperatures were measured in five obturator catheters. Therapeutic heating was measured in the catheters on the obturator between antennas in contact with the vaginal mucosa.
制作了一种阴道闭孔器，用于与植入导管配合使用，对外阴和阴道壁进行微波热疗和近距离放射治疗。仅采用间质技术难以对该部位进行加热或照射。对闭孔器进行了改进，在外壁设置了用于安装间质导管的凹槽，并与用于圆周植入的模板相匹配。使用三种微波天线设计阵列进行了功率沉积测试：偶极子天线（hA = hB = 3.9厘米）、螺旋天线（3.9厘米线圈，短路）和改进型偶极子天线（偶极子尖端有1.0厘米螺旋），以测试闭孔器的性能。将闭孔器和四根非闭孔器导管放置在肌肉等效体模中。两根闭孔器导管与两根独立导管组成闭孔器阵列。四根独立导管组成非闭孔器阵列。沿着每个阵列的中心轴、平分线和对角横断面进行功率沉积或比吸收率（SAR）测量。SAR结果表明，闭孔器壁中的天线如偶极子理论所预测的那样辐射，尽管与距闭孔器1.8厘米的相同导管中的天线相比，功率密度较低。这可以通过将闭孔器中天线的功率提高42%来补偿。相邻的天线对异相放置0.25秒，并围绕阵列旋转。相位旋转表明，中心阵列的SAR峰值可从100%降至50% SAR，偶极子天线因此可降低峰值温度，并通过改善功率分布来加热更大的体积。对于螺旋天线，在无相位旋转的相干操作下，阵列中心的SAR为50%。三名患者使用闭孔器和定制模板，采用偶极子天线进行治疗，并在五根闭孔器导管中测量温度。在与阴道黏膜接触的天线之间的闭孔器导管中测量治疗性加热情况。
