Dual-Energy CT for Imaging of Pulmonary Hypertension: Challenges and Opportunities

Abstract

Computed tomography (CT) is routinely used in the evaluation of patients with pulmonary hypertension (PH) to assess vascular anatomy and parenchymal morphology. The introduction of dual-energy CT (DECT) enables additional qualitative and quantitative insights into pulmonary hemodynamics and the extent and variability of parenchymal enhancement. Lung perfusion assessed at pulmonary blood volume imaging correlates well with findings at scintigraphy, and pulmonary blood volume defects seen in pulmonary embolism studies infer occlusive disease with increased risk of right heart dysfunction. Similarly, perfusion inhomogeneities seen in patients with PH closely reflect mosaic lung changes and may be useful for severity assessment and prognostication. The use of DECT may increase detection of peripheral thromboembolic disease, which is of particular prognostic importance in patients with chronic thromboembolic PH with microvascular involvement. Other DECT applications for imaging of PH include low-kilovoltage images with greater inherent iodine conspicuity and iodine-selective color-coded maps of vascular perfusion (both of which can improve visualization of vascular enhancement), virtual nonenhanced imaging (which better depicts vascular calcification), and, potentially, ventricular perfusion maps (to assess myocardial ischemia). In addition, quantitative assessment of central vascular and parenchymal enhancement can be used to evaluate pulmonary hemodynamics in patients with PH. The current status and potential advantages and limitations of DECT for imaging of PH are reviewed, and current evidence is supplemented with data from a tertiary referral center for PH.

Pulmonary Perfusion Changes as Assessed by Contrast-Enhanced Dual-Energy Computed Tomography after Endoscopic Lung Volume Reduction by Coils

“…In comparison with conventional CT, no additional cost, extra radiation dose, or extra intravenous iodine contrast medium injection is needed. Functional image processing is simply added, offering an invaluable and simultaneous exploration of the vascular anatomy, parenchymal morphology, and functional perfusion [14,15,16]. …”

Tailoring protocols for chest CT applications: when and how?

“…In order to define the quantity of iodinated CM in any voxel, the dual-energy CT data is post-processed and a mathematic algorithm is used to obtain an iodine map that is based on the known attenuation range values for iodine at 80 kVp and at 140 kVp and to measure its relative contribution to each voxel. In the specific case of pulmonary parenchyma, the calculation of iodine distribution, which depends on the microvascular circulation in the lung, can create color-coded pulmonary blood volume (PBV) maps that can be considered as a surrogate indicator of pulmonary perfusion (34). Furthermore, evaluation of morphologic features and anatomic structures is obtained merging image data from both energy levels to generate a hybrid image corresponding to a standard acquisition at 120 kVp.…”

Benefit of iodine density images to reduce out-of-field image artifacts at rapid kVp switching dual-energy CT

“…Material decomposition of DECT data can provide an iodine density image, which highlights contrast material signal, and a corresponding water density image, which simulates an unenhanced CT scan (14). The iodine density image is known to benefit many thoracoabdominal imaging indications, including to evaluate for possible pulmonary embolus (15), abdominal perfusion (16), and to detect hyper- or hypovascular masses in the liver and pancreas (17, 18). In addition to these diagnostic capabilities, iodine density images have also recently been shown to reduce intestinal peristalsis motion artifacts (19).…”