In vitro blood sample assessment: investigating correlation of laboratory hemoglobin and spectral properties of dual-energy CT measurements (ρ/Z)

Abstract

Objectives: Our study comprised a single-center retrospective in vitro correlation between spectral properties, namely ρ/Z values, derived from scanning blood samples using dual-energy computed tomography (DECT) with the corresponding laboratory hemoglobin/hematocrit (Hb/Hct) levels and assessed the potential in anemia-detection.

Methods: DECT of 813 patient blood samples from 465 women and 348 men was conducted using a standardized scan protocol. Electron density relative to water (ρ or rho), effective atomic number (Z_eff), and CT attenuation (Hounsfield unit) were measured.

Results: Positive correlation with the Hb/Hct was shown for ρ (r-values 0.37-0.49) and attenuation (r-values 0.59-0.83) while no correlation was observed for Z_eff (r-values -0.04 to 0.08). Significant differences in attenuation and ρ values were detected for blood samples with and without anemia in both genders (p value < 0.001) with area under the curve ranging from 0.7 to 0.95. Depending on the respective CT parameters, various cutoff values for CT-based anemia detection could be determined.

Conclusion: In summary, our study investigated the correlation between DECT measurements and Hb/Hct levels, emphasizing novel aspects of ρ and Z_eff values. Assuming that quantitative changes in the number of hemoglobin proteins might alter the mean Z_eff values, the results of our study show that there is no measurable correlation on the atomic level using DECT. We established a positive in vitro correlation between Hb/Hct values and ρ. Nevertheless, attenuation emerged as the most strongly correlated parameter with identifiable cutoff values, highlighting its preference for CT-based anemia detection.

Clinical relevance statement: By scanning multiple blood samples with dual-energy CT scans and comparing the measurements with standard laboratory blood tests, we were able to underscore the potential of CT-based anemia detection and its advantages in clinical practice.

Key points: Prior in vivo studies have found a correlation between aortic blood pool and measured hemoglobin and hematocrit. Hemoglobin and hematocrit correlated with electron density relative to water and attenuation but not Z_eff. Dual-energy CT has the potential for additional clinical benefits, such as CT-based anemia detection.

Keywords: Anemia; Blood; Computer-assisted radiographic image interpretation; Dual-energy computed tomography; X-ray computed tomography scanners.

Fig. 1

Standardized arrangement of blood samples to ensure proper assignment of anonymized blood samples after scanning

Fig. 2

Illustration of erythrocyte sedimentation rate using volume rendering images of one blood sample with visible sedimentation (a) and after 20 agitation cycles (b)

Fig. 3

Correct axis placement of the region of interest in the middle of the blood sample tube, avoiding wall contact

Fig. 4

Linear regression curves demonstrating the positive correlation found highest in tb DECT between Hb and attenuation for men (a) with an r-value of 0.83 and for women (b) with an r-value of 0.77

Fig. 5

Box-plot analysis for ρ (a, b) and attenuation (c, d) in a ds (a, c) and tb (b, d) DECT, illustrating the significant differences between measurements of blood samples with and without confirmed anemia from both sexes

Fig. 6

Anemia detection performance in DECT for men (a) and women (b), utilizing ρ and attenuation values for both scan modes, tb, and ds, in accordance with the WHO diagnostic criteria (Hb below 13 g/dL for men and below 12 g/dL for women)