Di Giandomenico E, Genovesi N, Sciarra R, Angelone T, Toppetti A
Istituto di Scienze Radiologiche, Università degli Studi di Chieti.
Radiol Med. 1993 Apr;85(4):416-20.
A positive correlation between the attenuation values of blood in vitro and hemoglobin concentration has been described by other authors. Our study is aimed at: 1) investigating the influence of artifacts on the measurement of blood density in vivo, 2) verifying the possible correlation between blood values and Hounsfield's units (HU) in vivo, 3) assessing whether such a correlation may be useful in calculating hemoglobin concentration, 4) investigating whether a significant difference in blood density exists between normal and anemic subjects, and 5) investigating the eventual borderline density values which separate the two populations. Fifty adult patients underwent CT of the upper abdomen for several clinical reasons. Twenty-six males, mean age 63 +/- 15 SD, and 24 females, mean age 63 +/- 14 SD, were included in our series. The two groups were then subdivided into two additional groups including anemic and normal subjects -14 g/dl and 12 g/dl being taken as the borderline values for males and females, respectively. Blood density was measured after defining two regions of interest (ROI) on the aorta and inferior vena cava. The results show that: 1) there are few image artifacts, which are sometimes detected only because of different numbers in aorta and vena cava; for quantitative blood measurement, 4 HU was considered as an acceptable difference; 2) the correlation between HU and hemoglobin concentration which was found in vitro was also seen in vivo (r = 0.76, p < 0.001). Furthermore, high positive correlation was observed between attenuation values and red cell count (r = 0.68) or hematocrit (r = 0.75). 3) However, this correlation cannot be used to calculate the patients's blood count since HU dispersion relative to the regression line is too high. The straight line of regressed computation, reporting the density values on the abscissa axis, shows a b = 0.33 slope and the intersection point is a = -1.43, SE b = 0.04, SE a = 1.76 and SE estimate = 1.56. When the mean density value was 43 HU in our sample, the expected hemoglobin value was 12.76 g/dl (+/- 1.58 SD). 4) Nonetheless, a significant difference in blood attenuation values was seen between normal subjects and anemic patients (p < 0.001). 5) This difference identifies a borderline density value, below which the patient is sure to be anemic (99% confidence), but nothing else can be said on the patient's normality: the value is 33 HU for females and 36 HU for males. These values allowed 20% of anemic subjects to be correctly identified, versus 5% of the same group detected with diagnosis images.
其他作者曾描述过体外血液衰减值与血红蛋白浓度之间呈正相关。我们的研究旨在：1）调查伪影对体内血液密度测量的影响；2）验证体内血液值与亨氏单位（HU）之间可能存在的相关性；3）评估这种相关性是否有助于计算血红蛋白浓度；4）调查正常受试者与贫血受试者之间的血液密度是否存在显著差异；5）研究区分这两个人群的最终临界密度值。五十名成年患者因多种临床原因接受了上腹部CT检查。我们的研究系列纳入了26名男性，平均年龄63±15标准差，以及24名女性，平均年龄63±14标准差。然后将这两组再细分为另外两组，包括贫血和正常受试者——男性和女性的临界值分别取14 g/dl和12 g/dl。在主动脉和下腔静脉上定义两个感兴趣区域（ROI）后测量血液密度。结果表明：1）图像伪影很少，有时仅因主动脉和腔静脉中的数量不同才被检测到；对于定量血液测量，4 HU被视为可接受的差异；2）体外发现的HU与血红蛋白浓度之间的相关性在体内也可见（r = 0.76，p < 0.001）。此外，在衰减值与红细胞计数（r = 0.68）或血细胞比容（r = 0.75）之间观察到高度正相关。3）然而，这种相关性不能用于计算患者的血细胞计数，因为相对于回归线的HU离散度太高。回归计算的直线，横坐标为密度值，显示斜率b = 0.33，交点a = -1.43，标准误b = 0.04，标准误a = 1.76，标准误估计值 = 1.56。在我们的样本中，当平均密度值为43 HU时，预期的血红蛋白值为12.76 g/dl（±1.58标准差）。4）尽管如此，正常受试者与贫血患者之间的血液衰减值存在显著差异（p < 0.001）。5）这种差异确定了一个临界密度值，低于该值患者肯定贫血（99%置信度），但关于患者的正常情况无法得出其他结论：女性的值为33 HU男性为36 HU。这些值能够正确识别出20%的贫血受试者，而通过诊断图像检测到的同一组受试者为5%。
