Mori Shinichiro, Endo Masahiro, Nishizawa Kanae, Ohno Mari, Miyazaki Hiroaki, Tsujita Kazuhiko, Saito Yasuo
Department of Medical Physics, National Institute of Radiological Sciences, Chiba 263-8555, Japan.
Phys Med Biol. 2005 Nov 21;50(22):N359-70. doi: 10.1088/0031-9155/50/22/N02. Epub 2005 Nov 1.
The prototype cone-beam CT (CBCT) has a larger beam width than the conventional multi-detector row CT (MDCT). This causes a non-uniform angular distribution of the x-ray beam intensity known as the heel effect. Scan conditions for CBCT tube current are adjusted on the anode side to obtain an acceptable clinical image quality. However, as the dose is greater on the cathode side than on the anode side, the signal-to-noise ratio on the cathode side is excessively high, resulting in an unnecessary dose amount. To compensate for the heel effect, we developed a heel effect compensation (HEC) filter. The HEC filter rendered the dose distribution uniform and reduced the dose by an average of 25% for free air and by 20% for CTDI phantoms compared to doses with the conventional filter. In addition, its effect in rendering the effective energy uniform resulted in an improvement in image quality. This new HEC filter may be useful in cone-beam CT studies.
原型锥形束CT（CBCT）的束宽比传统的多排探测器CT（MDCT）更大。这会导致X射线束强度出现不均匀的角分布，即所谓的足跟效应。CBCT管电流的扫描条件在阳极侧进行调整，以获得可接受的临床图像质量。然而，由于阴极侧的剂量比阳极侧大，阴极侧的信噪比过高，导致剂量不必要地增加。为了补偿足跟效应，我们开发了一种足跟效应补偿（HEC）滤波器。与传统滤波器相比，HEC滤波器使剂量分布均匀，在空气比释动能率方面剂量平均降低了25%，在CTDI体模方面剂量降低了20%。此外，其使有效能量均匀的效果提高了图像质量。这种新型HEC滤波器可能在锥形束CT研究中有用。
