Pandey Anil Kumar, Sharma Sanjay Kumar, Agarwal Krishan Kant, Sharma Punit, Bal Chandrasekhar, Kumar Rakesh
Department of Nuclear Medicine, All India Institute of Medical Sciences, New Delhi, India.
Indian J Nucl Med. 2016 Jan-Mar;31(1):20-6. doi: 10.4103/0972-3919.172346.
The role of (18)fluorodeoxyglucose positron emission tomography (PET) is limited for detection of primary hepatocellular carcinoma (HCC) due to low contrast to the tumor, and normal hepatocytes (background). The aim of the present study was to improve the contrast between the tumor and background by standardizing the input parameters of a digital contrast enhancement technique.
A transverse slice of PET image was adjusted for the best possible contrast, and saved in JPEG 2000 format. We processed this image with a contrast enhancement technique using 847 possible combinations of input parameters (threshold "m" and slope "e"). The input parameters which resulted in an image having a high value of 2(nd) order entropy, and edge content, and low value of absolute mean brightness error, and saturation evaluation metrics, were considered as standardized input parameters. The same process was repeated for total nine PET-computed tomography studies, thus analyzing 7623 images.
The selected digital contrast enhancement technique increased the contrast between the HCC tumor and background. In seven out of nine images, the standardized input parameters "m" had values between 150 and 160, and for other two images values were 138 and 175, respectively. The value of slope "e" was 4 in 4 images, 3 in 3 images and 1 in 2 images. It was found that it is important to optimize the input parameters for the best possible contrast for each image; a particular value was not sufficient for all the HCC images.
The use of above digital contrast enhancement technique improves the tumor to background ratio in PET images of HCC and appears to be useful. Further clinical validation of this finding is warranted.
由于与肿瘤及正常肝细胞（背景）相比对比度较低，（18）氟脱氧葡萄糖正电子发射断层扫描（PET）在检测原发性肝细胞癌（HCC）方面的作用有限。本研究的目的是通过标准化数字对比度增强技术的输入参数来提高肿瘤与背景之间的对比度。
将PET图像的横向切片调整至最佳对比度，并保存为JPEG 2000格式。我们使用847种可能的输入参数组合（阈值“m”和斜率“e”），通过对比度增强技术对该图像进行处理。将产生具有高二级熵值、边缘含量以及低绝对平均亮度误差值和饱和度评估指标的图像的输入参数视为标准化输入参数。对总共九项PET计算机断层扫描研究重复相同过程，从而分析7623张图像。
所选的数字对比度增强技术提高了HCC肿瘤与背景之间的对比度。在九张图像中的七张中，标准化输入参数“m”的值在150至160之间，另外两张图像的值分别为138和175。斜率“e”的值在4张图像中为4，3张图像中为3，2张图像中为1。发现为每张图像优化输入参数以获得最佳对比度很重要；一个特定值对所有HCC图像并不足够。
使用上述数字对比度增强技术可提高HCC的PET图像中的肿瘤与背景比值，且似乎很有用。这一发现值得进一步的临床验证。
