Combining perfusion and angiography with a low-dose cardiac CT technique: a preliminary investigation in a swine model

Abstract

Morphological and physiological assessment of coronary artery disease (CAD) is necessary for proper stratification of CAD risk. The objective was to evaluate a low-dose cardiac CT technique that combines morphological and physiological assessment of CAD. The low-dose technique was evaluated in twelve swine, where three of the twelve had coronary balloon stenosis. The technique consisted of rest perfusion measurement combined with angiography followed by stress perfusion measurement, where the ratio of stress to rest was used to derive coronary flow reserve (CFR). The technique only required two volume scans for perfusion measurement in mL/min/g; hence, four volume scans were acquired in total; two for rest with angiography and two for stress. All rest, stress, and CFR measurements were compared to a previously validated reference technique that employed 20 consecutive volume scans for rest perfusion measurement combined with angiography, and stress perfusion measurement, respectively. The 32 cm diameter volumetric CT dose index ($${\text{CTDI}}_{\text{vol}}^{32}$$ CTDI vol 32 ) and size-specific dose estimate (SSDE) of the low-dose technique were also recorded. All low-dose perfusion measurements (PLOW) in mL/min/g were related to reference perfusion measurements (PREF) through regression by PLOW = 1.04 PREF − 0.08 (r = 0.94, RMSE = 0.32 mL/min/g). The $${\text{CTDI}}_{\text{vol}}^{32}$$ CTDI vol 32 and SSDE of the low-dose cardiac CT technique were 8.05 mGy and 12.80 mGy respectively, corresponding to an estimated effective dose and size-specific effective dose of 1.8 and 2.87 mSv, respectively. Combined morphological and physiological assessment of coronary artery disease is feasible using a low-dose cardiac CT technique.

Dynamic CT myocardial perfusion without image registration

“…MI perfusion measurement also identified functionally significant stenoses with high accuracy, while only requiring two volume scans per measurement. Hence, accurate myocardial ischemia assessment, in the presence of motion without image registration, is feasible at a low dose (less than 3 mSv 15 – 18 ).…”

“…All volume scans were reconstructed with AIDR 3D (Canon Medical Systems) at 75% of the R-R interval with a voxel size of 0.43 × 0.43 × 0.50 mm. The V1 and V2 volume scans were then systematically selected for analysis 15 – 18 . For V1, volumetric region growing was used to measure the average enhancement of the aortic blood pool (Vitrea fX version 6.0, Vital Images).…”

“…However, our prior CT perfusion results that employed image registration 15 were discussed above. Additionally, as the raw data were previously acquired 15 , the limitations attributed to study design—central contrast injection, intracoronary adenosine, coronary balloon stenosis, small effective chest diameter, and acquisition timing—were all already addressed in detail and did not significantly impact the results of this work 15 – 18 , 29 .…”

“…Prior work in first-pass analysis (FPA) dynamic CT perfusion measurement has addressed some of these limitations via a new technique capable of accurate perfusion measurement with only two volume scans, where one volume scan may also double as a coronary CTA 15 – 18 . Yet, a remaining limitation of this motion-susceptible (MS) FPA technique is its reliance on image registration to minimize motion between the two volume scans of interest.…”

Low-dose quantitative CT myocardial flow measurement using a single volume scan: phantom and animal validation

“…30 Eventually, a comprehensive cardiac CT protocol was built, which enabled low-dose, vessel-specific 31,32 rest flow combined with CCTA, stress flow, and CFR measurement using only four prospectively acquired volume scans-two for rest and two for stress. 33 Yet, the major translational limitations of this comprehensive technique were: (1) its reliance on a specialized timing protocol for optimal acquisition of the four volume scans necessary for rest flow, CCTA, and stress flow measurement 34,35 and (2) its reliance on image registration to combat the effects of motion artifact between said volume scans. 24 Hence, the single-volume quantitative CT flow technique was developed as a solution, where the pre-contrast myocardial attenuation is estimated from the bolus tracking data, rather than from a separate volume scan, in turn, enabling quantitative flow measurement using a simplified protocol no different than a standard CCTA.…”