Cardiac CT: A system architecture study

Abstract

Background: We are interested in exploring dedicated, high-performance cardiac CT systems optimized to provide the best tradeoff between system cost, image quality, and radiation dose.

Objective: We sought to identify and evaluate a broad range of CT architectures that could provide an optimal, dedicated cardiac CT solution.

Methods: We identified and evaluated thirty candidate architectures using consistent design choices. We defined specific evaluation metrics related to cost and performance. We then scored the candidates versus the defined metrics. Lastly, we applied a weighting system to combine scores for all metrics into a single overall score for each architecture. CT experts with backgrounds in cardiovascular radiology, x-ray physics, CT hardware and CT algorithms performed the scoring and weighting.

Results: We found nearly a twofold difference between the most and the least promising candidate architectures. Architectures employed by contemporary commercial diagnostic CT systems were among the highest-scoring candidates. We identified six architectures that show sufficient promise to merit further in-depth analysis and comparison.

Conclusion: Our results suggest that contemporary diagnostic CT system architectures outperform most other candidates that we evaluated, but the results for a few alternatives were relatively close. We selected six representative high-scoring candidates for more detailed design and further comparative evaluation.

Keywords: CT; Computed tomography; cardiovascular disease; cardiovascular imaging.

Fig. 1.

Triz Functional Diagram.

Fig. 2.

Single source-detector pair architectures. (a) Single-source CT, Full FOV (SSCT-FFOV). A third-generation architecture that employs a single x-ray source and detector combination. Left: Transaxial cross-section at the central longitudinal plane. Right: Longitudinal cross-section through the axis of rotation. (b) Single-source CT, Cardiac FOV (SSCT-CFOV).

Fig. 3.

Dual source-detector pair architectures. (a) Dual-source CT, Mixed FOV (DSCT-MFOV). This architecture employs two x-ray sources and two detectors, one that provides FFOV projections and one that provides CFOV projection. (b) Dual-source CT, Cardiac FOV (DSCT-CFOV).

Fig. 4.

Multiple source-detector pair architectures. (a) Triple-source CT, Cardiac FOV (TSCT-CFOV). This architecture employs three x-ray sources and detectors, each providing CFOV. (b) Triple-source CT, Mixed FOV (TSCT-MFOV). (c) Triple-source CT, Cardiac FOV, asymmetrical (TSCT-CFOV(A)). (d) Quintuple-source CT, Cardiac FOV (QSCT-CFOV).

Fig. 5.

Architectures with multiple sources in Z. (a) Dual Twin Z CT, Cardiac FOV (DTZCT-CFOV). This architecture employs two x-ray sources and detectors, each providing CFOV, and with each source containing two focal spots in the longitudinal direction, for reduced cone-beam effects. (b) Dual Twin Z CT, Cardiac FOV (DTZCT-CFOV). (c) Dual Linear Source CT, Mixed FOV (DLSCT-MFOV). (d) Dual Linear Source CT, Cardiac FOV (DLSCT-CFOV).

Fig. 6.

Inverted geometry architectures. (a) Inverted Geometry CT, Cardiac FOV (IGCT-CFOV). This architecture employs a 2D x-ray source and incorporates a CFOV. This topology permits a substantially smaller detector. (b) Inverted Geometry CT, Full FOV (IGCT-FFOV).

Fig. 7.

Stationary CT architectures. (a) Single Peek-hole Source Ring (SCT-SPHSR-CFOV). (b) Single Offset Source Arc (SCT-SOSA-CFOV). (c) Dual Offset Source Ring (SCT-DOSA-CFOV).

Fig. 8.

Semi-stationary architectures. (a) Ring Source, Dual Rotating Detector CT, Cardiac FOV (OSDRDCT-CFOV). This architecture employs a 360° ring x-ray source and two CFOV detectors mounted on a high-speed rotating gantry. This permits higher temporal resolution without the high cost of a full-ring stationary detector. (b) Ring Source, Dual Rotating Detector Inverse Geometry CT, Cardiac FOV (OSRDIGCT-CFOV). (c) Rotating Source, Ring Detector CT, Cardiac FOV (RSODCT-CFOV).

Fig. 9.

Novel architectures: (a) Sector Source CT, Cardiac FOV (CSCT-CFOV). This architecture employs rotating multi-spot x-ray source and rotates slowly in order to obtain projection images over multiple cardiac cycles. This permits very high temporal resolution without the challenges associated with fast gantry rotation. (b) Concentric Circling CT (CCCT-CFOV).

Fig. 10.

Plot of final total of weighted normalized scores.

Fig. 11.

Summary of all Candidate Architectures. The architectures that were eventually selected for further evaluation are indicated with a bold outline.