Dual-energy CT Study Research Articles

SU‐E‐I‐98: Dose Comparison for Pulmonary Embolism CT Studies: Single Energy Vs. Dual Energy

Purpose:The purpose of this study was to assess and compare the size specific dose estimate (SSDE), dose length product (DLP) and noise relationship for pulmonary embolism studies evaluated by single source dual energy computed tomography (DECT) against conventional CT (CCT) studies in a busy cancer center and to determine the dose savings provided by DECT.Methods:An IRB‐approved retrospective study was performed to determine the CTDIvol and DLP from a subset of patients scanned with both DECT and CCT over the past five years. We were able to identify 30 breast cancer patients (6 male, 24 female, age range 24 to 81) who had both DECT and CCT studies performed. DECT scans were performed with a GE HD 750 scanner (140/80 kVp, 480 mAs and 40 mm) and CCT scans were performed with a GE Lightspeed 16 slice scanner (120 kVp, 352 mAs, 20 mm). Image noise was measured by placing an ROI and recording the standard deviation of the mean HU along the descending aorta.Results:The average DECT patient size specific dose estimate was to be 14.2 ± 1.7 mGy as compared to 22.4 ± 2.7 mGy from CCT PE studies, which is a 37% reduction in the SSDE. The average DECT DLP was 721.8 ± 84.6 mGy‐cm as compared to 981.8 ± 106.1 mGy‐cm for CCT, which is a 26% decrease. Compared to CCT the image noise was found to decrease by 19% when using DECT for PE studies.Conclusion:DECT SSDE and DLP measurements indicate dose savings and image noise reduction when compared to CCT. In an environment that heavily debates CT patient doses, this study confirms the effectiveness of DECT in PE imaging.

Dual-energy Computed Tomography in the Assessment of Vascular and Parenchymal Enhancement in Suspected Pulmonary Hypertension

To evaluate quantitative differences in central pulmonary artery (PA) and pulmonary global and regional enhancement in patients with and without pulmonary hypertension (PH) using dual-energy computed tomography (DECT). We retrospectively studied 391 thoracic DECT studies and identified 89 patients with PA pressure (PAP) data and a pulmonary angiogram. PH was defined as a mean PAP of ≥25 mm Hg on right heart catheterization (RHC) (n=19) or a systolic PAP of ≥40 mm Hg on echocardiography (n=20). PH absence was defined by entirely normal echocardiography or RHC (n=50). PA enhancement (PAenh) was calculated from DECT iodine images. Volumetric enhancement of each whole lung (WLenh), 6 standard lung regions (RLenh), and 24 two-dimensional standardized regions of interest (ROIenh) was performed in each patient using pulmonary blood volume analysis. Mean PAenh was greater in PH patients compared with controls (272 vs. 252 HU, P<0.05), with a reciprocal reduction in mean WLenh (27 vs. 32 HU, P<0.01). Mean ROIenh (n=2058) confirmed lower parenchymal enhancement in PH (27 vs. 32 HU, P<0.001), with greater mean ROIenh standard deviation (10.5 vs. 9.3, P<0.001). Mean intrapatient pulmonary enhancement variability was greater in PH patients than in controls for 6 RLenh (variance 37 vs. 22, P=0.02) and 24 ROIenh measures (variance 188 vs. 130, P=0.04). RLenh and ROIenh variance correlated with RHC pulmonary vascular resistance (PVR) (r=0.44, 0.48; P=0.04, 0.03, respectively). A ratio of PAenh/WLenh distinguished PH from non-PH patients (10.9 vs. 8.4, P<0.001) and correlated best with PVR (r=0.59, P=0.004). PH patients demonstrate increased PAenh with a reciprocal reduction and greater variation in parenchymal enhancement; a DECT ratio of central to parenchymal enhancement correlates with PVR and may help identify PH.

Relationship between structural joint damage and urate deposition in gout: a plain radiography and dual-energy CT study

ObjectivesThe aim of this work was to examine the relationship between joint damage and monosodium urate (MSU) crystal deposition in gout.MethodsPlain radiographs and dual-energy CT (DECT) scans of the feet...

First–Arterial-Pass Dual-Energy CT for Assessment of Myocardial Blood Supply: Do We Need Rest, Stress, and Delayed Acquisition? Comparison with SPECT

To compare the relative contributions of rest, stress, and delayed acquisitions with the accuracy of dual-energy (DE) computed tomography (CT) for the assessment of myocardial blood supply. With institutional review board approval and HIPAA compliance, 55 consecutive patients (10 women, 45 men; mean age, 62 years ± 10) clinically referred for cardiac single photon emission computed tomography (SPECT) who were known to have or were suspected of having coronary artery disease were prospectively enrolled. DE CT studies were acquired during adenosine stress, at rest, and after 6-minute delay. The DE CT iodine distribution maps were visually assessed for perfusion deficits or late iodine enhancement. Per-segment agreement between modalities was investigated with κ statistics. Test characteristics for the detection of perfusion deficits were calculated for combinations of rest, stress, and delayed DE CT acquisition, with SPECT as reference standard. At SPECT, 714 segments were considered normal, 192 showed fixed perfusion defects, and 29 showed reversible perfusion deficits. Sensitivity of rest-only DE CT was 92%, and specificity was 98%. Stress-only, rest-stress, stress and delayed, and the combination of all three had a sensitivity of 99% and a specificity of 97%. Of 29 segments with reversible perfusion deficits at SPECT, 13 (45%) were misclassified by using rest-stress DE CT as fixed perfusion deficits. With stress DE CT plus delayed acquisition, 13 of 192 (7%) segments with fixed perfusion deficits at SPECT were misclassified as reversible. Rest-stress acquisition should be the protocol of choice for assessment of the myocardial blood supply in DE CT. The accuracy of DE CT is not increased by the addition of a delayed DE CT acquisition, which may therefore be omitted to reduce radiation exposure. With rest-stress DE CT, almost one-half of defects that are reversible at SPECT were classified as fixed; radiologists and clinicians need to be aware of this incongruence when they interpret DE CT myocardial perfusion studies.

Tendon involvement in the feet of patients with gout: a dual-energy CT study

ObjectivesTo examine the frequency and patterns of monosodium urate (MSU) crystal deposition in tendons and ligaments in patients with gout using dual-energy CT (DECT).MethodsNinety-two patients with tophaceous gout had DECT...

La tomografía computarizada de doble energía: ¿para qué la quiero?

Dual-energy CT is one of the newest and most attractive fields in radiology today. New generation scanners can acquire datasets with different X-ray spectra, which facilitates the characterization of certain chemical elements, making it possible to detect functional alterations in the absence of morphologic or densitometric anomalies. The capability of characterizing these elements is enabling new applications to be developed for clinical practice and changing the way we work. The aim of this article is to explain what dual-energy CT studies are, the techniques available for performing them, the advantages and disadvantages of these studies, and what we might expect from this field in the future.

High-Temporal Resolution Dual-Energy Computed Tomography of the Heart Using a Novel Hybrid Image Reconstruction Algorithm

Dual-energy computed tomography (DECT) has been proposed for the comprehensive assessment of coronary artery stenosis and myocardial perfusion yet traditionally required reducing the temporal resolution of cardiac studies. We evaluated a reconstruction algorithm that preserves high temporal resolution at cardiac DECT. Twelve consecutive patients (3 women; mean [SD] age, 64 [10] years) with an abnormal single photon emission CT result underwent invasive coronary angiography and cardiac DECT. Dual-energy CT studies were reconstructed using the standard algorithm with 165-millisecond temporal resolution and a hybrid algorithm providing 83-millisecond temporal resolution. These studies were rated for coronary image quality and motion artifacts and compared with invasive coronary angiographic studies. One hundred sixty-eight coronary artery segments (82%) were evaluated. The standard 165-millisecond reconstruction provided 95% diagnostic segments compared with 100% using the 83-millisecond hybrid reconstruction. Image quality was rated significantly (P < 0.05) better with hybrid reconstruction and had 91.4% sensitivity, 94.7% specificity, 82.1% positive predictive value, and 97.7% negative predictive value for detecting significant stenosis versus 85.7%, 93.2%, 76.9%, and 96.1% with standard reconstruction, respectively. Hybrid image reconstruction mitigates the former limitations in temporal resolution of cardiac DECT.

Attenuation-based characterization of coronary atherosclerotic plaque: Comparison of dual source and dual energy CT with single-source CT and histopathology

Objective To compare different CT acquisition techniques regarding for attenuation-based characterization of coronary atherosclerotic plaques using histopathology as the standard of reference. Materials and methods In a post mortem study 17 human hearts were studied with dual-source CT (DSCT) and dual energy CT (DECT) mode on a DSCT as well as with 16-slice single-source CT (SSCT). At autopsy, atherosclerotic lesions were cut at 5 μm sections. Histopathologic classification of the plaques according to the American Heart Association (AHA) criteria was performed by two pathologists. Attenuation values of all plaques were measured in DSCT, DECT and SSCT studies, respectively and classified based on attenuation according to modified AHA criteria. Results 58 coronary plaques were identified at autopsy. Regardless of the CT technique only 52/58 plaques were found at CT (sensitivity = 89.6%). There was no significant difference between the mean attenuation values of different plaque types between DSCT, DECT, and SSCT: type IV: 11 HU/8 HU/19 HU; type Va: 44 HU/45 HU/52 HU; type Vb: 1088 HU/966 HU/1079 HU). The sensitivity for correct classification varied depending on the plaque type (type II = 0%, type III = 0%, type IV = 43%, type Va = 58%, Vb = 97%). Conclusion Independent of the used acquisition technique, SSCT, DSCT and DECT show similar results for attenuation-based characterization of atherosclerotic coronary plaques.

Comparison of Dual-Energy Computed Tomography of the Heart With Single Photon Emission Computed Tomography for Assessment of Coronary Artery Stenosis and of the Myocardial Blood Supply

To evaluate the performance of dual-energy computed tomography (CT) for integrative imaging of the coronary artery morphology and the myocardial blood supply, 36 patients (15 women, mean age 57 +/- 11 years) with equivocal or incongruous single photon emission CT (SPECT) results were investigated by a single-contrast medium-enhanced, retrospectively electrocardiographic-gated dual-energy CT (DECT) scan with simultaneous acquisition of high and low x-ray spectra. Thirteen patients subsequently underwent invasive coronary angiography (ICA). The DECT data were used to reconstruct anatomic coronary CT angiographic images and to map the myocardial iodine distribution within the left ventricular myocardium. Two independent observers analyzed all DECT studies for stenosis and myocardial iodine defects. A segmental comparison was performed between the stress/rest SPECT perfusion defects and DECT iodine defects and between the ICA and coronary CT angiographic findings for stenosis. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were estimated, along with the kappa statistics. Overall, DECT had 92% sensitivity and 93% specificity, with 93% accuracy for detecting any type of myocardial perfusion defect seen on SPECT. Contrast defects at DECT correctly identified 85 (96%) of 89 fixed and 60 (88%) of 68 reversible myocardial perfusion defects. The interobserver agreement was very good (weighted kappa = 0.87). Compared with ICA, coronary CT angiography had 90% sensitivity, 94% specificity, and 93% accuracy for the detection of >50% stenosis. In conclusion, our initial experience suggests that DECT, as a single examination, might be promising for the integrative analysis of the coronary artery morphology and the myocardial blood supply and is in good agreement with ICA and SPECT.

Abstract 4181: Dual-Energy CT of the Heart for Diagnosing Coronary Artery Stenosis and Myocardial Ischemia - Comparison with SPECT

A single dual-energy CT (DECT) scan can assess coronary anatomy and detect myocardial perfusion defects (PD) seen on SPECT. 28 patients underwent SPECT myocardial perfusion imaging, invasive coronary angiography (ICA), and a single contrast medium-enhanced, retrospectively ECG-gated DECT scan using a dual-source CT system with simultaneous acquisition of high and low x-ray spectra. Scan data was used to reconstruct anatomic coronary CT angiographic (cCTA) images and to map the myocardial iodine distribution on virtually non-contrast enhanced long- and short-axis views of the left ventricle. Two independent observers analyzed all DECT studies for coronary artery stenosis and myocardial blood-pool deficits. Segmental comparison was performed between DECT, ICA, and SPECT. Data were analyzed using the Bayesian model. 484 myocardial segments were evaluated. 135 segments in 21 patients showed blood-pool deficits on DECT. In all territories where DECT showed blood-pool deficits, SPECT or catheter angiography confirmed PD or critical stenosis. Overall, DECT had 94.4% sensitivity and 95.2% specificity with 95% accuracy for detecting PD seen on SPECT. In patients without significant stenosis and negative SPECT (n=7), DECT showed no sign of blood-pool deficits. Interobserver agreement was very good (weighted kappa = 0.87). Compared with ICA, cCTA reconstructions had 98% sensitivity, 88% specificity and 92% accuracy for detection of &gt;50% stenosis. Initial experience suggests that DECT may be promising for the comprehensive analysis of coronary artery morphology and the myocardial blood pool in good agreement with ICA and SPECT.

Myocardial Ischemia Diagnosed by Dual-Energy Computed Tomography

For decades, dual-energy imaging has been used for tissue differentiation with several x-ray–based imaging modalities, exploiting the fact that the tissues in the human body show different absorption characteristics when penetrated with different x-ray spectra, spectra that are typically generated by different kV settings of the x-ray tube. Recently, dual-source computed tomography (CT) with 2 x-ray tubes and 2 detector arrays mounted in the same gantry has become available.1 After experience with earlier experimental prototypes, this dual-source CT for the first time enables the clinical acquisition of dual-energy CT studies simultaneously with a single scan. We used a dual-source CT scanner (Definition, Siemens, Forchheim, Germany) in dual-energy mode for performing coronary CT angiography in a 74-year–old woman with suspected coronary artery disease and prior abnormal nuclear rest/stress single-photon emission CT (SPECT). The CT scan was acquired with retrospective ECG-gating and the following scan parameters: 330-ms gantry rotation, pitch 0.2, and 32×2×0.6-mm …