Reliability of 3D image analysis and influence of contrast medium administration on measurement of Hounsfield unit values of the proximal femur

The effect of contrast media on CT measures of bone mineral density: a systematic review

OBJECTIVE

The aim was to systematically assess the literature on possible effect of administration of iodinated contrast media on CT-estimated bone mineral density (BMD).

MATERIALS AND METHODS

The Web of Science and PubMed databases were searched. Studies that used both CT principles of BMD measurement (volumetric quantitative BMD and CT attenuation in Hounsfield Units) were included. The baseline patient data, skeletal site, contrast medium data (if reported), and change in BMD on contrast-enhanced CT scans were collected.

RESULTS

Sixteen studies met our review criteria, the majority of which was performed on lumbar spine, and the others on proximal femur. Almost all studies reported a significant increase in BMD values on the contrast-enhanced CT scans, ranging from 0.8 to 30.3%. The increase was most frequently reported to be about 10 to 15% for the spine and 5 to 10% for the femur. In addition to the difference in skeletal site, some authors found the contrast effect was age-, sex-, and contrast dose-dependent. BMD values in arterial phase were generally somewhat lower than in venous phase, and the effect of contrast in venous phase was more predictable.

CONCLUSION

The review revealed significant changes in BMD values between unenhanced and contrast-enhanced CT. The change was more pronounced in lumbar spine than in proximal femur and appeared to depend on age, sex, contrast dose, and postcontrast imaging protocol. The review suggests the understanding of all mentioned factors during the interpretation of BMD measured on contrast-enhanced CT.

Comparison of HU histogram analysis and BMD for proximal femoral fragility fracture assessment: a retrospective single-center case-control study

OBJECTIVES

To evaluate the feasibility of HU histogram analysis (HUHA) to assess proximal femoral fragility fractures with respect to BMD.

METHODS

This retrospective study included 137 patients with femoral fragility fractures who underwent hip CT and 137 control patients without fractures who underwent abdominal CT between January 2018 and February 2019. HUHA was calculated with the 3D volume of interest from the femoral head to the lesser trochanter. HUHA_fat (percentage of negative HU values) and HUHA_bone (percentage of HU values ≥ 125 HU) were assumed to be fat and bone components, respectively. Statistical significance was assessed using the area under the receiver operating characteristic curve (AUC), Spearman correlation (ρ), and odds ratio.

RESULTS

HUHA_fat was strongly positively correlated (ρ = 0.56) and BMD was moderately negatively correlated with fragility fractures (ρ =  - 0.37). AUC of HUHA_fat (0.82, 95% CI [0.77, 0.87]) significantly differed from that of BMD (0.69, 95% CI [0.63, 0.75]) (p < .001). The cutoff value was 15.8% for HUHA_fat (sensitivity: 90.4%; specificity: 67.7%) and 0.709 g/cm² for BMD (sensitivity: 87.5%; specificity: 51.5%), with higher HUHA_fat and lower BMD values indicating fragility fractures. The odds ratio of HUHA_fat was 19.5 (95% CI [9.9, 38.2], p < .001), which was higher than that of BMD, 7.4 (95% CI [4.0, 13.6], p < .001).

CONCLUSION

HUHA_fat revealed better performance than BMD and demonstrated feasibility in assessing proximal femoral fragility fractures.

KEY POINTS

• HUHA_fat showed a strong positive correlation (Spearman ρ = 0.56, p < .001), and BMD showed a moderate negative correlation (Spearman ρ =  - 0.37, p < .001) with proximal femoral fragility fractures. • HUHA_fat (AUC = 0.82) performed significantly better than BMD in assessing proximal femoral fragility fractures (AUC = 0.69) (p < .001). • The odds ratio of HUHA_fat for proximal femoral fragility fractures was higher than that of BMD (19.5 and 7.4, respectively; p < .001).