Carlo N. De Cecco

Prognostic Value of Quantitative Contrast-Enhanced Cardiovascular Magnetic Resonance for the Evaluation of Sudden Death Risk in Patients With Hypertrophic Cardiomyopathy

Background— Hypertrophic cardiomyopathy (HCM) is the most common cause of sudden death in the young, although not all patients eligible for sudden death prevention with an implantable cardioverter-defibrillator are identified. Contrast-enhanced cardiovascular magnetic resonance with late gadolinium enhancement (LGE) has emerged as an in vivo marker of myocardial fibrosis, although its role in stratifying sudden death risk in subgroups of HCM patients remains incompletely understood. Methods and Results— We assessed the relation between LGE and cardiovascular outcomes in 1293 HCM patients referred for cardiovascular magnetic resonance and followed up for a median of 3.3 years. Sudden cardiac death (SCD) events (including appropriate defibrillator interventions) occurred in 37 patients (3%). A continuous relationship was evident between LGE by percent left ventricular mass and SCD event risk in HCM patients (P=0.001). Extent of LGE was associated with an increased risk of SCD events (adjusted hazard ratio, 1.46/10% increase in LGE; P=0.002), even after adjustment for other relevant disease variables. LGE of ≥15% of LV mass demonstrated a 2-fold increase in SCD event risk in those patients otherwise considered to be at lower risk, with an estimated likelihood for SCD events of 6% at 5 years. Performance of the SCD event risk model was enhanced by LGE (net reclassification index, 12.9%; 95% confidence interval, 0.3–38.3). Absence of LGE was associated with lower risk for SCD events (adjusted hazard ratio, 0.39; P=0.02). Extent of LGE also predicted the development of end-stage HCM with systolic dysfunction (adjusted hazard ratio, 1.80/10% increase in LGE; P<0.03). Conclusions— Extensive LGE measured by quantitative contrast enhanced CMR provides additional information for assessing SCD event risk among HCM patients, particularly patients otherwise judged to be at low risk.

State of the Art: Iterative CT Reconstruction Techniques

Owing to recent advances in computing power, iterative reconstruction (IR) algorithms have become a clinically viable option in computed tomographic (CT) imaging. Substantial evidence is accumulating about the advantages of IR algorithms over established analytical methods, such as filtered back projection. IR improves image quality through cyclic image processing. Although all available solutions share the common mechanism of artifact reduction and/or potential for radiation dose savings, chiefly due to image noise suppression, the magnitude of these effects depends on the specific IR algorithm. In the first section of this contribution, the technical bases of IR are briefly reviewed and the currently available algorithms released by the major CT manufacturers are described. In the second part, the current status of their clinical implementation is surveyed. Regardless of the applied IR algorithm, the available evidence attests to the substantial potential of IR algorithms for overcoming traditional limitations in CT imaging.

Dual-energy CT: oncologic applications.

OBJECTIVE Dual-energy CT (DECT) is an innovative imaging technique that operates on the basic principle of application of two distinct energy settings that make the transition from CT attenuation-based imaging to material-specific or spectral imaging. The purpose of this review is to describe the use of DECT in oncology. CONCLUSION Applications of DECT in clinical practice are based on two capabilities: material differentiation and material identification and quantification. The capability of obtaining different material-specific datasets (iodine map, virtual unenhanced, and monochromatic images) in the same acquisition can improve lesion detection and characterization. This approach can also affect evaluation of the response to therapy and detection of oncology-related disorders. DECT is an innovative imaging technique that can dramatically affect the care of oncologic patients.

Dual energy CT (DECT) of the liver: conventional versus virtual unenhanced images

ObjectiveTo compare image quality and noise of conventional unenhanced (CU) and virtual unenhanced (VU) images in patients who underwent hepatic dual energy computed tomography (DECT) and to assess potential radiation dose reduction.Materials and methodsForty consecutive patients were studied. Mean CU and VU image quality and noise were analyzed by two blinded radiologists using a five-point grade scale. The effective radiation dose of a triple-phase protocol (CU, arterial and DE portal phases) were compared with that of a dual-phase protocol (arterial and DE portal phases).ResultsNo significant difference in mean image quality was observed between VU (3.92 ± 0.85) and CU images (4.20 ± 0.72). A significant difference in mean image noise was observed between VU and CU (P < 0.01). The dose reduction achieved by omitting the unenhanced acquisition was 30.47 ± 7.07% (P < 0.01). In 6 patients, a complete VU liver image was not obtained.ConclusionsVU images can be obtained with similar image quality as CU. This approach favors a reduction in patient’s radiation exposure. Nevertheless, a complete abdominal DECT is possible only in patients with a low body mass index, due technical limitations of the present DECT systems.

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

PURPOSE 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. MATERIALS AND METHODS 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. RESULTS 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. CONCLUSION 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.

Anatomic variations of the hepatic arteries in 250 patients studied with 64-row CT angiography

The aim of our study was to determine the frequency of different hepatic arterial variants identified on abdominal CT angiography (CTA) with a 64-row CT system and a high resolution protocol. A total of 250 consecutive abdominal CTAs performed on a 64-row CT system were evaluated. Two radiologists in consensus analyzed arterial phase images; the anatomical findings were grouped according to Michels’ classification. An anomalous arterial pattern was observed in 34% of the cases. The most common anomaly was Michels type III (9.2%), followed by types II and V (5.2%), type VI (4.0%), types IV, VII, and IX (2.0%), and type VIII (0.6%). No cases of type X were detected. Unclassified variations were observed in 3.3% of the cases. The new generation of 64-row MDCT allows optimal visualization of splanchnic vascular anomalies with a minimally invasive examination. This visualization is extended to those vessels with a small caliber and slow flow resulting in difficult recognition by classic angiographic studies. The knowledge of anomalous arterial patterns could be very useful in the preoperative planning of surgical and interventional liver procedures.

Coronary Artery Computed Tomography Scanning

A 46-year-old woman with diabetes mellitus and a body mass index of 32 kg/m2 reports repeated episodes of chest pain after moderate activity. single photon emission computed tomography myocardial perfusion imaging demonstrates no electrocardiographic (EKG) abnormalities and a small fixed perfusion defect in the posterior left ventricle. Prospectively EKG-triggered coronary CT angiography (CCTA), performed with a radiation dose of 3.5 mSv, demonstrates unremarkable coronary arteries with no evidence of stenosis or atherosclerosis (Figure 1). Figure 1. Unremarkable coronary CT angiography study with no evidence of stenosis or atherosclerosis. Cx indicates circumflex artery; D1, first diagonal; LAD, left anterior descending; LM, left main; OM1, first obtuse marginal; and RCA, right coronary artery. A 63-year-old man with treated hypertension and hyperlipidemia experiences diffuse chest pain and shortness of breath after a long distance flight. Catheter angiography 2 years earlier was normal. At emergency department arrival, his EKG demonstrates no signs of myocardial injury. Cardiac troponin I is 0.04 ng/mL. An EKG-synchronized acute chest pain CCTA examination demonstrates extensive noncalcified plaque of the mid left anterior descending coronary artery causing severe stenosis with signs of acute myocardial hypoperfusion in the anterior and apical left ventricle (Figure 2). The patient undergoes successful revascularization with a drug eluting stent. Figure 2. Coronary CT angiography examination ( A–C ) demonstrates extensive noncalcified plaque of the mid left anterior descending coronary artery causing severe stenosis (arrows) with signs of acute myocardial hypoperfusion in the anterior and apical left ventricle (arrowheads). The obstructive lesion is confirmed by cardiac catheterization ( D ). CCTA has left the early stages of clinical evaluation and matured into a robust diagnostic technique in both elective and emergent settings. Technological innovations are continuously improving the diagnostic performance and decreasing the radiation dose associated with this test. In this Clinician Update, we provide an updated summary on the state-of- …

Diagnostic value of quantitative stenosis predictors with coronary CT angiography compared to invasive fractional flow reserve

OBJECTIVE To evaluate the diagnostic performance of CCTA-derived stenosis predictors including CT-FFR for the detection of ischemia-inducing stenosis compared to invasive FFR. MATERIALS AND METHODS Stenosis parameters were assessed using dual-source CT (DSCT). All patients underwent both CCTA and invasive FFR within 3 months and were retrospectively analyzed. Observers visually assessed all CCTA studies and performed multiple lesion measurements. Lesion length/minimal luminal diameter(4) (LL/MLD(4)), transluminal attenuation gradient (TAG), corrected coronary attenuation (CCO) and CT-FFR were calculated. RESULTS The cohort included 32 patients (58±12 years, 66%male). Among 32 coronary lesions, 8 (25%) were considered hemodynamically significant with an FFR <0.80. Compared to invasive FFR, the per-vessel sensitivity and specificity of CCTA, CT-FFR, LL/MLD(4), CCO and TAG for detecting hemodynamically significant lesions were 100% and 54%, 100% and 91%, 85% and 92%, 66% and 88%, 37% and 58%, respectively. Receiver operating characteristics analysis resulted in an area under the curve of 0.91 for CT-FFR (p=0.0005), 0.88 for LL/MLD(4) (p<0.0001), 0.85 for CCO (p<0.0001). TAG with an AUC of 0.67 (p=0.152) was unable to discriminate between vessels with or without hemodynamically significant lesions. CONCLUSION CT-FFR, LL/MLD(4) and CCO provide enhanced diagnostic performance over CCTA analysis alone for discrimination of hemodynamically significant coronary stenosis.

Monoenergetic extrapolation of cardiac dual energy CT for artifact reduction

Background Monoenergetic extrapolation of cardiac dual-energy computed tomography (DECT) could be useful in artifact reduction in clinical practice. Purpose To evaluate the potential of monoenergetic extrapolation of cardiac DECT data for reducing artifacts from metal and high iodine contrast concentration. Material and Methods With IRB approval and in HIPAA compliance, 35 patients (22 men, 61 ± 12 years) underwent cardiac DECT with dual-source CT (100 kVp and 140 kVp). Contrast material injection protocols were adapted to the patient’s weight using non-ionic low-osmolar 370 mgI/mL iopromide. Datasets were transferred to a stand-alone workstation and dedicated monoenergetic analysis software was used for postprocessing. Reconstructions with the following five photon energies were generated: 40 keV, 60 keV, 80 keV, 100 keV, and 120 keV. Artifact severity was graded on a 5-point Likert scale (0, massive artifact; 5, absence of artifact). The size of artifact and image noise (expressed as HU) in anatomic structures adjacent to the artifact were measured. Quantitative and subjective image quality was compared using Friedman and Wilcoxon tests. Results We observed artifacts arising from densely concentrated contrast material in the superior vena cava (SVC) in 18 patients, from sternal wires in 14, from bypass clips in eight, and from coronary artery stents in seven. Artifact size in monoenergetic reconstructions from 40 to 120 keV decreased from 21.3 to 19 mm for the SVC (P < 0.001), from 8.4 to 2.6 mm for sternal wires (P < 0.001), from 6.4 to 2.2 mm for bypass clips (P < 0.001), and from 5.9 to 2.7 mm for stents (P < 0.001), respectively. The quality score changed from 0.2 to 3.8 for the SVC (P < 0.001), from 0.1 to 4 for sternal wires (P < 0.001), from 0 to 3.9 for bypass clips (P < 0.001), and from 0 to 3.9 for stents (P < 0.001). Lowest noise in adjacent structures was found at 80 keV for the SVC (39.1 HU), for sternal wires (33.3), for bypass clips (26.9), and for stents (33.9). Conclusion A significant reduction of high-attenuation artifacts can be achieved by use of higher monoenergetic energy levels with cardiac DECT. However, image noise in anatomic structures affected by artifacts is lowest at 80 keV, which suggests an evaluation approach that makes use of multiple energy levels for a complete diagnosis.

Dual-energy CT of the pancreas: improved carcinoma-to-pancreas contrast with a noise-optimized monoenergetic reconstruction algorithm

PURPOSE To evaluate a novel monoenergetic reconstruction algorithm (nMERA) with improved noise reduction for dual-energy CT (DECT) of pancreatic adenocarcinoma. MATERIALS AND METHODS Sixty patients with suspected pancreatic carcinoma underwent dual-source dual-energy CT with arterial phase. Images were reconstructed as linearly-blended 120-kV series (M_0.6) and with the standard monoenergetic (sMERA) and the novel monoenergetic algorithm (nMERA) with photon energies of 40, 55, 70 and 80 keV. Objective image quality was compared regarding image noise, pancreas attenuation, signal-to-noise ratio (SNR) and pancreas-to-lesion contrast. Subjective image quality was assessed by two observers. RESULTS Thirty pancreatic adenocarcinomas were detected. nMERA showed significantly reduced image noise at low keV levels compared with sMERA images (55 keV: 7.19 ± 2.75 vs. 20.68 ± 7.01 HU; 40 keV: 7.33 ± 3.20 vs. 37.22 ± 14.66 HU) and M_0.6 (10.69 ± 3.57 HU). nMERA pancreatic SNR was significantly superior to standard monoenergetic at 40 (47.02 ± 23.41 vs. 9.37 ± 5.83) and 55 keV (28.29 ± 16.86 vs. 9.88 ± 7.01), and M_0.6 series (11.42 ± 6.00). Pancreas-to-lesion contrast peaked in the nMERA 40 keV series (26.39 ± 16.83) and was significantly higher than in all other series (p<0.001). nMERA 55 keV images series were consistently preferred by both observers over all other series (p<0.01). CONCLUSIONS nMERA DECT can significantly improve image quality and pancreas-to-lesion contrast in the diagnosis of pancreatic adenocarcinoma.