直接度量X 光能譜，容易發生能量堆疊效應，除非將測量距離拉大，並加裝精準且微細之偵檢器準直儀方可為之，惟實際應用甚為困難。本文則使用間接度量方式，以PMMA 為散射材料，由高純鍺偵檢器搭配康普吞散射腔，度量90 度散射的X 光脈衝波高分佈，再反推重建入射之X 光能譜。電壓分別設定在65、80、100、120 kVp，本文將所度量到的90 度脈衝波高分佈(PHD, Pulse Height Distribution)，成功地反推重建獲得X 光能譜。除制動輻射外，鎢靶的Kα與Kβ特性輻射亦清楚顯現。當X 光電壓大於100 kVp 時，額外干擾的鉛Kα特性輻射將出現。

Due to the high fluence rate of diagnostic x-rays, the pill-up effect makes it difficult to detect x-ray spectrum directly, unless one increases the distance between the detector and the x-ray tube or adopts a fine collimator on the head of detector. Our experiment applied an indirect method, through measuring the pulse height distribution of Compton scattering photons at 90° angle, to reconstruct the primary x-ray spectrum. An HPGe detector measured the pulse height distribution that resulted from interactions of x-rays with the PMMA material. The x-ray spectra have been successfully reconstructed for tube voltages of 65, 80, 100, and 120 kVp. The spectra showed not only the bremsstrahlung continua but also the Kα and Kβ characteristic radiation peaks of tungsten . The spectra also exhibited extra energy peaks from the Kα characteristic radiations of lead when the tube voltage was larger than 100 kVp.