Simultaneous high-pitch multi-energy CT pulmonary angiography using a dual-source photon-counting-detector CT: A phantom experiment.

PURPOSE: A dual-source CT system can be operated in a high-pitch helical mode to provide a temporal resolution of 66 ms, which reduces motion artifacts in CT pulmonary angiography (CTPA). It can also be operated in a multi-energy (ME) mode to provide iodine maps, beneficial in the evaluation of pulmonary embolism (PE). No energy-integrating detector (EID) CT can perform simultaneous ME and high-pitch acquisition. This phantom study aimed to evaluate the ability of a photon-counting-detector (PCD) CT to perform simultaneous high-pitch and ME imaging for CTPA. METHODS: A motion phantom was used to mimic the respiratory motion. Two tubes filled with iodine with intravascular thrombus mimicked by injecting glue within the tubes were placed along with 5, 10, and 15 mg/mL iodine samples, on a motion phantom at 20 and 30 revolutions per minute. Separate high-pitch and ME EID-CT scans and a single high-pitch ME PCD scan were acquired and virtual monoenergetic images and iodine maps reconstructed. Percent thrombus occlusion was measured and compared between static and moving images. RESULTS: When there was motion, EID-CT ME suffered from significant motion artifacts. The measured iodine concentrations with PCD-CT in high-pitch ME were more stable when there was a motion, with a lower standard deviation than EID-CT in ME mode. The estimated percent thrombus occlusion dropped significantly with applied motion on EID-CT, while PCD-CT high-pitch ME mode showed good agreement between measurements on static or moving images. CONCLUSION: PCD-CT with combined ME and high-pitch mode facilitates simultaneous accurate iodine quantification and assessment of intravascular occlusion.

Vascular Applications of Dual-Energy Computed Tomography.

Dual- or multi-energy CT imaging provides several advantages over conventional CT in the context of vascular imaging. Specific advantages include the use of low-energy virtual monoenergetic images (VMIs) to boost iodine attenuation to salvage suboptimal enhanced studies, perform low-contrast material dose studies, and increase conspicuity of small vessels and lesions. Alternatively, high-energy VMIs reduce artifacts caused by some metals, endoprosthesis, calcium blooming, and beam hardening. Virtual non-contrast (VNC) images reduce radiation dose by eliminating the need for a true non-contrast acquisition in multiphasic CT studies. Iodine maps can be used to evaluate perfusion of tissues and lesions.

CTA of Acute Pulmonary Embolism: Best Practices.

Pulmonary CTA is a commonly performed study and the radiologist's role is not limited to simply producing a report. The process from identifying the appropriate patients who will benefit from the study to improving performance in the radiology department requires the radiologist's involvement, expertise, and leadership. The focus of this narrative review is to highlight the different steps and the ways to improve the quality in the assessment of thromboembolic disease where the radiologists can have an impact. This article provides an update on the commonly used and more recently published clinical decision tools, specific parameter adjustments of pulmonary CTA for more challenging patients and potential improvement for the radiology department.