Three-dimensional aortic geometry mapping via registration of non-gated contrast-enhanced or gated and respiratory-navigated MR angiographies

BACKGROUND

The measurement of aortic dimensions and their evolution are key in the management of patients with aortic diseases. Manual assessment, the current guideline-recommended method and clinical standard, is subjective, poorly reproducible, and time-consuming, limiting the capacity to track aortic growth in everyday practice. Aortic geometry mapping (AGM) via image registration of serial computed tomography angiograms outperforms manual assessment, providing accurate and reproducible 3D maps of aortic diameter and growth rate. This observational study aimed to evaluate the accuracy and reproducibility of AGM on non-gated contrast-enhanced (CE-) and cardiac- and respiratory-gated (GN-) magnetic resonance angiographies (MRA).

METHODS

Patients with thoracic aortic disease followed with serial CE-MRA (n = 30) or GN-MRA (n = 15) acquired at least 1 year apart were retrospectively and consecutively identified. Two independent observers measured aortic diameters and growth rates (GR) manually at several thoracic aorta reference levels and with AGM. Agreement between manual and AGM measurements and their inter-observer reproducibility were compared. Reproducibility for aortic diameter and GR maps assessed with AGM was obtained.

RESULTS

Mean follow-up was 3.8 ± 2.3 years for CE- and 2.7 ± 1.6 years for GN-MRA. AGM was feasible in the 93% of CE-MRA pairs and in the 100% of GN-MRA pairs. Manual and AGM diameters showed excellent agreement and inter-observer reproducibility (ICC>0.9) at all anatomical levels. Agreement between manual and AGM GR was more limited, both in the aortic root by GN-MRA (ICC=0.47) and in the thoracic aorta, where higher accuracy was obtained with GN- than with CE-MRA (ICC=0.55 vs 0.43). The inter-observer reproducibility of GR by AGM was superior compared to manual assessment, both with CE- (thoracic: ICC= 0.91 vs 0.51) and GN-MRA (root: ICC=0.84 vs 0.52; thoracic: ICC=0.93 vs 0.60). AGM-based 3D aortic size and growth maps were highly reproducible (median ICC >0.9 for diameters and >0.80 for GR).

CONCLUSION

Mapping aortic diameter and growth on MRA via 3D image registration is feasible, accurate and outperforms the current manual clinical standard. This technique could broaden the possibilities of clinical and research evaluation of patients with aortic thoracic diseases.

[Computed tomographic measurement of coronary artery calcification in the assessment of cardiovascular risk: a descriptive study]

INTRODUCTION AND OBJECTIVES

Measurement of coronary artery calcification (CAC) is used in the evaluation of cardiovascular risk. We investigated its usefulness by comparing CAC assessment with that of various risk charts.

METHODS

We determined cardiovascular risk in patients without known atherosclerosis using the 1998 European Task Force (ETF), REGICOR (Registre Gironí del Corazón) and SCORE (Systematic Coronary Risk Evaluation) charts. CAC was assessed by computerized tomography and measurements were classified as low risk (i.e., score <1), intermediate risk (i.e., score 1-100), or high risk (i.e., score >100).

RESULTS

The study included 331 patients (mean age 54 [8.5] years, 89% male). In 44.1%, CAC was detected (mean score 96 [278]). The degree of agreement between the cardiovascular risk derived from the CAC score and that derived from the SCORE and ETF charts was acceptable: kappa=.33 (P<.05) and kappa=.28 (P<.05), respectively, but agreement was poor with the REGICOR chart: kappa=.02 (P=.32). The SCORE and ETF charts, respectively, classified 45.0% and 38.3% of patients with a CAC score >100 as high risk, whereas the REGICOR chart did not classify any of these patients as high risk. Male sex, older age, smoking history, and a family history of coronary heart disease were all associated with the detection of CAC.

CONCLUSIONS

Measurement of CAC demonstrated calcification in 44.1% of patients without known atherosclerosis. By regarding those with a CAC score > 100 as high-risk, 10.4% of patients evaluated using the SCORE chart would be reclassified as high risk, as would 11.6% of those evaluated using the ETF chart, and 18.9% of those evaluated using the REGICOR chart. Consequently, more patients would be eligible for preventative treatment.