Chan K W, Chou C K, McDougall J A, Luk K H, Vora N L, Forell B W
Department of Radiation Research, City of Hope National Medical Center, Duarte, California 91010-0269.
Int J Hyperthermia. 1989 Jul-Aug;5(4):499-507. doi: 10.3109/02656738909140474.
The changes in heating patterns of interstitial microwave antennas at different insertion depths were investigated in a static phantom at 915 MHz. Antennas for the Clini-Therm Mark VI system were inserted 5-15 cm into muscle-equivalent material, through nylon catheters. The phantom was heated with arrays of antennas at 2 cm spacings for 60 s at 15 W per antenna. Midplane and transverse heating patterns were determined thermographically with the antennas inserted parallel or perpendicular to the split of the phantom. Hot spots, independent of heating near the junction plane, were observed in the midplane of the 2 x 2 and 2 x 4 arrays at 2.8 cm from the insertion end. The magnitudes of these hot spots were reduced by 40-45 per cent as insertion depth was increased from 7 to 10.5 cm. With insertion depths of more than 11.5 cm the hot spots gradually diminished and heating occurred mostly near the junction plane. The observed heating patterns were caused by changes in impedance of the antenna arrays at different insertion depths. The impedance mismatch had resulted in different wave propagation within the tissue material which produced different radiation patterns. During treatments, because heating varies with insertion depth, great care must be exercised in monitoring temperatures.
在915兆赫的静态仿真人体模型中，研究了不同插入深度下组织间微波天线加热模式的变化。将用于Clini-Therm Mark VI系统的天线通过尼龙导管插入到相当于肌肉的材料中5至15厘米深处。用间距为2厘米的天线阵列以每根天线15瓦的功率对仿真人体模型加热60秒。当天线平行或垂直于仿真人体模型的分割面插入时，用热成像法确定中平面和横向加热模式。在距插入端2.8厘米处的2×2和2×4阵列的中平面观察到与接合面附近加热无关的热点。随着插入深度从7厘米增加到10.5厘米，这些热点的强度降低了40%至45%。当插入深度超过11.5厘米时，热点逐渐减小，加热主要发生在接合面附近。观察到的加热模式是由不同插入深度下天线阵列阻抗的变化引起的。阻抗失配导致组织材料内不同的波传播，从而产生不同的辐射模式。在治疗过程中，由于加热随插入深度而变化，因此在监测温度时必须格外小心。
