Amr M. Ajlan

Coronary computed tomography angiography for stable angina: past, present, and future.

Although the clinical use of computed tomography in cardiac imaging had slow beginnings, it has seen rapid development over the past decade. This review aims to discuss the state of the technology and to help clarify its role in the diagnosis and management of coronary artery disease. This article highlights major historic perspectives, the accuracy of coronary computed tomography angiography in evaluating obstructive coronary artery disease, associated radiation exposure issues, considerations in patient selection, and ongoing clinical and technologic advancements.

MRI for the diagnosis of cardiac and liver iron overload in patients with transfusion-dependent thalassemia: An algorithm to guide clinical use when availability is limited

To the Editor: Iron overload (IOL) in the heart and liver is a common complication in transfusion-dependent thalassemia (TDT) and is associated with increased risk of morbidity and mortality. Owing to the different mechanisms of iron accumulation and the wide scope of disease severity, iron-loading rate varies between organs and, consequently, different organs are affected unevenly. Nowadays, several measurement methods are available to diagnose and quantify IOL in the various organs. Serum ferritin (SF) has been the standard IOL measure in patients with TDT, especially through serial assessment. Although inexpensive, practical, and commonly available, SF does not always predict body iron as it is an indirect indicator of tissue iron burden and is influenced by several factors such as infection and inflammation. Its correlation with liver iron concentration (LIC), specifically, is significant but varies with assessment method and disease, while its correlation with cardiac iron is poor. SF<1000 ng/mL has been associated with improved survival, while levels >2500 ng/mL indicate increased risk of cardiac morbidity and mortality. Alternatively, liver biopsy is a direct measure of iron in the liver; nevertheless, it is invasive and associated with risks and sampling and measurement errors. Direct tissue-iron measurement in the heart is not possible. Magnetic resonance imaging (MRI) has emerged as a non-invasive alternative for quantifying both liver (by R2 or T2* MRI) and heart (by cardiac T2* MRI) iron by overcoming shortcomings of SF measurement and liver biopsy. The technique is sensitive, validated, and internationally reproducible and enables better tailoring of iron-chelation therapy (ICT) by allowing identification of patients at risk of organ-specific morbidity and monitoring of ICT effectiveness in the liver and heart. Moreover, specific thresholds of LIC and cardiac T2* have been associated with clinical morbidities and mortality (LIC >7 mg/g dry weight associated with clinical morbidity; cardiac T2* <20 ms associated with arrhythmias, <10 ms associated with heart failure and death). Therefore, monitoring of liver and heart iron by MRI is considered a standard of care in thalassemia. Despite the established utility and widespread use of MRI, it is not always available or affordable, especially in resource-poor regions where TDT prevalence is highest. Moreover, in healthcare centers with large patient volumes, assessment for all patients at regular intervals is not always feasible because of financial constraints. Furthermore, although international guidelines recommend standard monitoring of liver and cardiac iron by MRI (every 6 months to 2 years, depending on several factors and IOL status), they do not provide sufficient guidance on when or whom to assess with MRI, especially when resources are limited and patient prioritization should be considered. To address the gaps in MRI utilization for TDT management in resource-poor settings, a panel of thalassemia experts from the Middle East, North Africa, and Asia Pacific regions met and proposed a simple and practical algorithm based on their experience of limitations and obstacles encountered with MRI utilization in those regions. The algorithm can guide the use of MRI for the detection and monitoring of IOL in TDT while considering its availability and accessibility for patients. Three scenarios were proposed based on availability and accessibility of MRI. Scenario 1: MRI available and accessible for all patients Age is the main determinant for initial MRI measurement. Consequently, in an ideal situation whereby MRI is easily accessible, all TDT patients aged 10 years, regardless of all other characteristics, would be candidates for baseline IOL screening by liver and heart MRI (based on validated methods and standard calibration). Of note, and in view of the recently published reports describing the early occurrence of liver and cardiac iron loading in children with TDT, MRI could still be requested in patients <10 years old informed by physician discretion, based on transfusion burden, SF levels, clinical complication profile, and MRI availability (Figure 1). Scenario 2: MRI available but not accessible for all patients Where MRI is not accessible for all patients, those aged 10–18 years with SF >2500 ng/mL should be prioritized, followed by any patient with SF >2500 ng/mL to optimize chelation therapy and prevent complications. In addition, patients with an increasing SF trend despite iron chelation should be considered for MRI screening as increasing SF levels could reflect an increase in organ iron loading. Liver and heart examination should be performed simultaneously when possible. The frequency of follow-up testing depends on the baseline reading: repeat MRI annually when cardiac T2* <20 ms or LIC >7 mg/g dry

Low-dose attenuation correction in diagnosis of non-alcoholic fatty liver disease

BackgroundNon-enhanced computed tomography (CT) is a valuable modality in the diagnosis of non-alcoholic fatty liver disease (NAFLD). However, it is not clear if low-dose CT attenuation correction (CTAC) scans have the same accuracy to diagnose NAFLD. Our aim is to evaluate the diagnostic accuracy of low-dose CTAC in the diagnosis of NAFLD using non-enhanced CT as a gold standard.MethodsA total of 864 patients who underwent a clinically indicated hybrid nuclear imaging scanning between May 2011 and April 2014 were included in the study. Diagnosis of fatty liver was established if an absolute liver attenuation was <40 Hounsfield units and/or a liver-to-spleen ratio was <1.1. The diagnostic accuracy parameters were calculated to detect NAFLD by low-dose CTAC using unenhanced CT as a gold standard.ResultsThe prevalence of fatty liver by diagnostic CT and low-dose attenuation correction were 9.9 and 12.9% (using liver attenuation <40HU and liver-to-spleen ratio <1.1), respectively, with 32.9 and 34.9% (using absolute liver attenuation or ratio-to-spleen criteria), correspondingly. Low-dose CTAC had sensitivity (81.3%), specificity (94.0%), positive predictive value (60.2%), and negative predictive value (97.8%) using both diagnostic criteria. Using either of the diagnostic criteria resulted in sensitivity (76.8%), specificity (83.5%), PPV (66.3%), and NPV (89.5%).ConclusionLow-dose CT could be used as a tool to rule out the presence of fatty liver if neither liver attenuation of less than 40 HU nor liver-to-spleen below 1.1 is present.

Coronary-pulmonary arterial fistula in a neonate with pulmonary atresia—ventricular septal defect and single coronary artery

In cases of pulmonary atresia with ventricular septal defect (PA‐VSD), coronary‐pulmonary arterial fistula (CPAF) as the main source of pulmonary blood supply is extremely rare. These fistulae may arise from the left coronary artery, right coronary artery, or a single coronary artery. Fistulae from a single coronary artery are unusual. We are reporting a case of PA‐VSD with single coronary artery and CPAF as the main source of pulmonary supply in addition to two major aortopulmonary collateral arteries (MAPCAS). Successful surgical correction with VSD closure and right ventricle (RV) to the pulmonary artery (PA) conduit was made.

Detectability of choledocholithiasis on CT: The effect of positive intraduodenal enteric contrast on portovenous contrast-enhanced studies.

Background/Aim: To retrospectively assess the accuracy of intravenous (IV) contrast-enhanced multidetector CT (MDCT) in choledocholithiasis detectability, in the presence and absence of positive intraduodenal contrast. Patients and Methods: Over a 3-year period, patients in whom endoscopic retrograde cholangiopancreatography (ERCP) was performed within a week from a portovenous (PV)-enhanced abdominal CT were identified. The final cohort consisted of 48 CT studies in which the entire common bile duct (CBD) length was visualized (19 males, 29 females; mean age, 68 years). We identified two groups according to the absence (n = 31) or presence (n = 17) of positive intraduodenal contrast. CT section thickness ranged from 1.25 to 5 mm. Two radiologists, blinded to clinical information and ERCP results, independently evaluated the CT images. Direct CBD stone visualization was assessed according to previously predefined criteria, correlating with original electronic CT reports and using ERCP findings as the reference standard. A third reader retrospectively reviewed all discordant results. The diagnostic performances of both observers and interobserver agreement were calculated for both groups. Results: 77%–88% sensitivity, 50%–71% specificity, and 71%–74% accuracy were obtained in the group without positive intraduodenal contrast, versus 50%–80% sensitivity, 57%–71% specificity, and 59%–71% accuracy in the group with positive intraduodenal contrast. With the exception of the positive predictive value (PPV), all diagnostic performance parameters decreased in the positive intraduodenal contrast group, mostly affecting the negative predictive value (NPV) (71%–78% vs 50%–67%). Conclusion: PV-enhanced MDCT has moderate diagnostic performance in choledocholithiasis detection. A trend of decreasing accuracy was noted in the presence of positive intraduodenal contrast.

The reproducibility of coronary artery calcium scoring on different software platforms

Coronary Artery Calcium Score (CACS) is commonly used to risk-stratify asymptomatic patients with intermediate risk for coronary ar-tery disease (CAD) [1] and in patients in whom treatment decisionsare still uncertain. Coronary artery calcium is usually assessed via anon-contrast electrocardiographic (ECG) gated study and quantifiedusing a score developed by Agatston et al. [2] The score is based onthe volume and density of calcium deposits and the X-ray attenuationcoefficient. The CACS has been shown in many studies to predict out-comes [3–5]. However, there is scarce data documenting the reproduc-ibility of CACS using different software platforms. Thus, the aim of thisanalysis is to evaluate the reproducibility of CACS using two differentcommercial softwares.A total of 159 clinically indicated patients who underwent CACSusing a 64-slice multi-detector computed tomography (CT) system(General Electric VCT Milwaukee, WI) with non-enhanced prospectiveECG gating were included. The CT scan parameters were as follows:tube voltage of 120 kV, tube current of 200 mAs, rotation time of400 ms, and collimation of 0.4 mm. The examination was performedin a cranio-caudal direction during deep inspiratory breath holding.All images were reconstructed in 3 mm slice thickness. The data setswere evaluated using two different commercially available softwares:software A (4DM Calcium score, INVIA, Ann Arbor, MI) and software B(Smart score, General Electric, Milwaukee, WI). Two, blinded indepen-dent and experienced readers evaluated each dataset. Each softwaredetected coronary arterial calcifications based on a threshold of 130Hounsfield units. The resultant calcium scores were divided into differ-ent groups (i.e. 0, 1–9, 10–99, 100–399, ≥400), as previously described[4]. The correlation between the different CACS was performed usingSpearman rank correlation. In addition, Bland–Altman plots were usedto evaluate the reproducibility CACS score.Almost half of the included patients were females (51%). The meanage was 62 ± 12 years old. Diabetes mellitus, hypertension and dyslip-idemia were highly prevalent in the study population (52%, 91% and88%, respectively). The mean heart rate at the scan time was 68 ± 9beats per minute, while the mean body mass index was 29 ± 6 kg/m

CT Evaluation of the Myocardial Supply-Fast kV-Switching Dual-Energy CT

Cardiovascular computed tomography (CT) has undergone significant technical developments over the past decade. The introduction of multi-detector row computed tomography (MDCT) with wider detector coverage, faster gantry rotation speed, multiple X-ray sources, electrocardiographic (ECG)-based tube current modulation, and integration of new iterative reconstruction algorithms has allowed for tangible improvements in diagnostic accuracy. Utilizing these technical advancements, recent attempts have been made to develop CT myocardial perfusion (CTP) imaging strategies. Moreover, the evaluation of myocardial perfusion defects on routine coronary CT angiography (cCTA) has been shown to be of additional value above that of assessing coronary anatomy alone, particularly in the acute chest pain setting. Unfortunately, there are many limitations that currently hinder CT perfusion with single-energy CT imaging, including artifacts. This chapter provides an overview of the role of single-source dual-energy CT in the evaluation of the myocardial perfusion and the current state of Rapid-kVp switching dual-energy CT.