Our preoccupation with ultra-low dose radiation exposure. Low contrast resolution and cardiovascular CT imaging

Low kV and Low Concentration Contrast Agent with Iterative Reconstruction of Computed Tomography (CT) Coronary Angiography: A Preliminary Study

Background

The aim of this study was to evaluate the image quality and radiation dose of CT coronary angiography (CTCA) with low kV, low concentration contrast agent, and iterative reconstruction.

Material/Methods

Ninety cases were randomly divided into 3 groups according to contrast agent concentration: group A 270 mg/ml (100 kV), group B 350 mg/ml (120 kV), and group C 370 mg/ml (120 kV), with 30 cases per group. Tube current was 200–250 mAs. Collimator width was 128×0.6 mm. Rotation speed was 0.27 s. The CT value of the left and right coronary arteries and the ascending aortic root was measured. The SNR and CNR of the images were calculated to evaluate the image quality objectively. The CTDI, DLP, and contrast injection were recorded.

Results

There were no significant differences in sex, age, weight, height, and BMI among the 3 groups. There was no statistically significant difference between left and right coronary artery and ascending aortic root CT value, background noise, SNR, and CNR. Compared to B and C, the ED in group A decreased by about 27.58% and 28.21%, respectively. The total amount of iodine in group A was decreased by about 21.27% and 24.83%, respectively compared with groups B and C.

Conclusions

Low kV and low concentration contrast agent combined with iterative reconstruction for CTCA imaging produced image quality consistent with that of conventional CTCA and significantly reduced the dosage of the radiation and injected iodine.

Peri-procedural imaging for transcatheter mitral valve replacement

Mitral regurgitation (MR) has a high prevalence in older patient populations of industrialized nations. Common etiologies are structural, degenerative MR and functional MR secondary to myocardial remodeling. Because of co-morbidities and associated high surgical risk, open surgical mitral repair/replacement is deferred in a significant percentage of patients. For these patients transcatheter repair/replacement are emerging as treatment options. Because of the lack of direct visualization, pre- and intra-procedural imaging is critical for these procedures. In this review, we summarize mitral valve anatomy, trans-catheter mitral valve replacement (TMVR) options, and imaging in the context of TMVR.

Progression of coronary artery disease. Experience with computed tomography

Coronary artery disease (CAD) begins with asymptomatic atherosclerotic changes in the vessel wall. Gradual or abrupt progression of some of these early lesions eventually leads to symptomatic luminal narrowing. Coronary computed tomography angiography (CTA) allows for a minimally invasive assessment of these wall changes and of the severity of luminal narrowing, and is thus an attractive method for assessing progression/regression. However, because of the associated radiation exposure and concern about false-positive findings, CTA is not recommended as a clinical screening test. Owing to the significantly lower spatial resolution compared with invasive modalities, its application as a tool for clinical progression/regression trials is limited. Therefore, while there are extensive data from both CT coronary artery calcium scoring and CTA studies demonstrating the prognostic value of luminal stenosis as well as the extent and characteristics of plaque, data describing progression/regression are limited.

State-of-the-Art Updates on Cardiac Computed Tomographic Angiography for Assessing Coronary Artery Disease

OPINION STATEMENT

Cardiac computed tomographic angiography (CCTA) is a noninvasive imaging modality that is increasingly useful for the evaluation of coronary artery disease (CAD). Over the past decade, CCTA has consistently demonstrated an excellent sensitivity for the detection and exclusion of coronary atherosclerosis in patients with stable or acute chest pain symptoms. Large prospective registries have repeatedly demonstrated the prognostic significance of the presence, extent, or absence of CAD by CCTA. In response to initial concerns, technical advances have permitted a dramatic reduction in patient radiation exposure with preserved image quality. For many patients, the radiation dose of CCTA is less than half of that with conventional myocardial perfusion imaging while providing significantly more anatomic information. Furthermore, CCTA's excellent spatial resolution is increasingly being used for noninvasive assessment of coronary plaque, including the detection of higher-risk vulnerable plaque and association between plaque characteristics and ischemia. Finally, new promising techniques that incorporate physiology with anatomy, such as CT-based fractional flow reserve (FFR-CT) and CT perfusion (CTP), are allowing for the noninvasive hemodynamic assessment of coronary stenoses and improvements in the specificity of CCTA findings. Such advances augur a coming transition when CCTA will be a first-line test for the detection, exclusion, and even management of CAD in many patients.

Noninvasive testing strategies in symptomatic, intermediate-risk CAD patients: a perspective on the "PROMISE" trial and its potential implementation in clinical practice

While the results of the Prospective Multicenter Imaging Study for Evaluation of Chest Pain trial (PROMISE trial) are negative for the primary outcome, the results from this large, contemporary trial of >10,000 patients provide important insights into clinical management of patients presenting with chest pain. The results reinforce that while diagnostic testing is an important component of modern management, its choice should be directed by a clinician in a clinical context and with subsequent management in mind. Based on presentation and pre-test probability, the clinician will decide if any additional testing necessary is necessary and if that is the case chose the most appropriate test according to current guidelines, applied to the individual patient and clinical scenario.

Coronary CTA using scout-based automated tube potential and current selection algorithm, with breast displacement results in lower radiation exposure in females compared to males

PURPOSE

To evaluate the effect of automatic tube potential selection and automatic exposure control combined with female breast displacement during coronary computed tomography angiography (CCTA) on radiation exposure in women versus men of the same body size.

MATERIALS AND METHODS

Consecutive clinical exams between January 2012 and July 2013 at an academic medical center were retrospectively analyzed. All examinations were performed using ECG-gating, automated tube potential, and tube current selection algorithm (APS-AEC) with breast displacement in females. Cohorts were stratified by sex and standard World Health Organization body mass index (BMI) ranges. CT dose index volume (CTDIvol), dose length product (DLP) median effective dose (ED), and size specific dose estimate (SSDE) were recorded. Univariable and multivariable regression analyses were performed to evaluate the effect of gender on radiation exposure per BMI.

RESULTS

A total of 726 exams were included, 343 (47%) were females; mean BMI was similar by gender (28.6±6.9 kg/m(2) females vs. 29.2±6.3 kg/m(2) males; P=0.168). Median ED was 2.3 mSv (1.4-5.2) for females and 3.6 (2.5-5.9) for males (P<0.001). Females were exposed to less radiation by a difference in median ED of -1.3 mSv, CTDIvol -4.1 mGy, and SSDE -6.8 mGy (all P<0.001). After adjusting for BMI, patient characteristics, and gating mode, females exposure was lower by a median ED of -0.7 mSv, CTDIvol -2.3 mGy, and SSDE -3.15 mGy, respectively (all P<0.01).

CONCLUSIONS

We observed a difference in radiation exposure to patients undergoing CCTA with the combined use of AEC-APS and breast displacement in female patients as compared to their BMI-matched male counterparts, with female patients receiving one third less exposure.

Cardiac CT: atherosclerosis to acute coronary syndrome

Coronary computed tomographic angiography (CCTA) is a robust non-invasive method to assess coronary artery disease (CAD). Qualitative and quantitative assessment of atherosclerotic coronary stenosis with CCTA has been favourably compared with invasive coronary angiography (ICA) and intravascular ultrasound (IVUS). Importantly, it allows the study of preclinical stages of atherosclerotic disease, may help improve risk stratification and monitor the progressive course of the disease. The diagnostic accuracy of CCTA in the assessment of coronary artery bypass grafts (CABG) is excellent and the constantly improving technology is making the evaluation of stents feasible. Novel techniques are being developed to assess the functional significance of coronary stenosis. The excellent negative predictive value of CCTA in ruling out disease enables early and safe discharge of patients with suspected acute coronary syndromes (ACS) in the Emergency Department (ED). In addition, CCTA is useful in predicting clinical outcomes based on the extent of coronary atherosclerosis and also based on individual plaque characteristics such as low attenuation plaque (LAP), positive remodelling and spotty calcification. In this article, we review the role of CCTA in the detection of coronary atherosclerosis in native vessels, stented vessels, calcified arteries and grafts; the assessment of plaque progression, evaluation of chest pain in the ED, assessment of functional significance of stenosis and the prognostic significance of CCTA.

Missense mutations resulting in type 1 lissencephaly

Proper human brain formation is dependent upon the integrated activity of multiple genes. Malfunctioning of key proteins results in brain developmental abnormalities. Mutation(s) in the LIS1 gene or the X-linked gene doublecortin (DCX) results in a spectrum of disorders including lissencephaly, or "smooth brain", and subcortical band heterotopia, or "doublecortex". Here, we will focus on a particular subset of missense mutations in these two genes and their effect on protein structure and function.