Triple Ring Technologies, Inc., 39655 Eureka Drive, Newark, California 94560, USA.
Med Phys. 2013 May;40(5):051911. doi: 10.1118/1.4801908.
Reduction of radiation dose in x-ray imaging has been recognized as a high priority in the medical community. Here the authors show that a regional adaptive exposure method can reduce dose-area product (DAP) in x-ray fluoroscopy. The authors' method is particularly geared toward providing dose savings for the pediatric population.
The scanning beam digital x-ray system uses a large-area x-ray source with 8000 focal spots in combination with a small photon-counting detector. An imaging frame is obtained by acquiring and reconstructing up to 8000 detector images, each viewing only a small portion of the patient. Regional adaptive exposure was implemented by varying the exposure of the detector images depending on the local opacity of the object. A family of phantoms ranging in size from infant to obese adult was imaged in anteroposterior view with and without adaptive exposure. The DAP delivered to each phantom was measured in each case, and noise performance was compared by generating noise arrays to represent regional noise in the images. These noise arrays were generated by dividing the image into regions of about 6 mm(2), calculating the relative noise in each region, and placing the relative noise value of each region in a one-dimensional array (noise array) sorted from highest to lowest. Dose-area product savings were calculated as the difference between the ratio of DAP with adaptive exposure to DAP without adaptive exposure. The authors modified this value by a correction factor that matches the noise arrays where relative noise is the highest to report a final dose-area product savings.
The average dose-area product saving across the phantom family was (42 ± 8)% with the highest dose-area product saving in the child-sized phantom (50%) and the lowest in the phantom mimicking an obese adult (23%).
Phantom measurements indicate that a regional adaptive exposure method can produce large DAP savings without compromising the noise performance in the image regions with highest noise.
在医学领域，降低 X 射线成像中的辐射剂量已被视为当务之急。本文作者展示了一种区域自适应曝光方法，可降低 X 射线透视中的剂量面积乘积（DAP）。该方法特别针对儿科人群，旨在节省剂量。
扫描束数字 X 射线系统采用大面积 X 射线源和 8000 个焦点，并结合小面积光子计数探测器。通过采集和重建多达 8000 个探测器图像来获取成像帧，每个图像仅观察患者的一小部分。区域自适应曝光是通过根据物体的局部不透明度来改变探测器图像的曝光来实现的。对大小从婴儿到肥胖成人的一系列体模进行前后位成像，分别在有和没有自适应曝光的情况下进行。在每种情况下测量每个体模的 DAP，并通过生成代表图像中局部噪声的噪声数组来比较噪声性能。这些噪声数组是通过将图像分为约 6mm² 的区域、计算每个区域的相对噪声并将每个区域的相对噪声值放置在一维数组（噪声数组）中从最高到最低的顺序生成的。将具有自适应曝光的 DAP 与无自适应曝光的 DAP 的比值作为剂量面积乘积节省量进行计算。作者通过一个校正因子对该值进行了修正，该因子匹配相对噪声最高的噪声数组，以报告最终的剂量面积乘积节省量。
整个体模系列的平均剂量面积乘积节省量为（42±8）%，其中儿童大小的体模节省量最大（50%），模拟肥胖成人的体模节省量最小（23%）。
体模测量表明，区域自适应曝光方法可以在不影响噪声性能最高的图像区域的情况下，显著节省 DAP。
