Waterman F M, Hoh L L
Department of Radiation Oncology and Nuclear Medicine, Thomas Jefferson University Hospital, Philadelphia, PA 19107.
Int J Hyperthermia. 1995 Jan-Feb;11(1):121-30. doi: 10.3109/02656739509004953.
RTOG thermometry guidelines for clinical trials of hyperthermia using planar ultrasound recommended that temperatures be mapped in polyurethane catheters by use of single-junction copper-constantan thermocouples. These guidelines were based on an assumption that the error in temperature measurement due to thermal conduction would generally not exceed +/- 0.3 degrees C. The validity of this assumption was tested with a commercially available single-junction copper-constantan thermocouple. The width of the point spread function, an indicator of the relative magnitude of the conduction error, was five times greater than expected. As a result, the conduction error is projected to exceed 0.3 degrees C in a temperature gradient of only 1.5 degrees C/cm. This projection was confirmed by mapping a thermal peak which simulates a typical clinical temperature profile. This peak had an amplitude of 6 degrees C, a full-width at half-maximum of 3.5 cm, and a maximum gradient of approximately 3 degrees C/cm. Temperatures measured at 0.5-cm intervals over the span of this peak were in error by a mean of +/- 0.6 degrees C. It is strongly recommended that the RTOG guidelines be revised to replace copper-constantan thermocouples with manganin-constantan single- or multi-junction thermocouples which will assure that the conduction error will be < +/- 0.3 degrees C.
放射肿瘤学组（RTOG）关于使用平面超声进行热疗临床试验的温度测量指南建议，应使用单结铜-康铜热电偶在聚氨酯导管中绘制温度图。这些指南基于这样一个假设，即由于热传导导致的温度测量误差通常不会超过±0.3摄氏度。使用市售的单结铜-康铜热电偶对这一假设的有效性进行了测试。点扩散函数的宽度是传导误差相对大小的一个指标，比预期大五倍。因此，在仅1.5摄氏度/厘米的温度梯度下，传导误差预计将超过0.3摄氏度。通过绘制模拟典型临床温度分布的热峰证实了这一预测。该峰的幅度为6摄氏度，半高宽为3.5厘米，最大梯度约为3摄氏度/厘米。在该峰的跨度上以0.5厘米的间隔测量的温度平均误差为±0.6摄氏度。强烈建议修订RTOG指南，用锰铜-康铜单结或多结热电偶取代铜-康铜热电偶，以确保传导误差将<±0.3摄氏度。
