Dose reduction in dynamic CT stress myocardial perfusion imaging: comparison of 80-kV/370-mAs and 100-kV/300-mAs protocols.

OBJECTIVES: To determine the effect of reduced 80-kV tube voltage with increased 370-mAs tube current on radiation dose, image quality and estimated myocardial blood flow (MBF) of dynamic CT stress myocardial perfusion imaging (CTP) in patients with a normal body mass index (BMI) compared with a 100-kV and 300-mAs protocol. METHODS: Thirty patients with a normal BMI (<25 kg/m(2)) with known or suspected coronary artery disease underwent adenosine-stress dual-source dynamic CTP. Patients were randomised to 80-kV/370-mAs (n = 15) or 100-kV/300-mAs (n = 15) imaging. Maximal enhancement and noise of the left ventricular (LV) cavity, contrast-to-noise ratio (CNR) and MBF of the two groups were compared. RESULTS: Imaging with 80-kV/370-mAs instead of 100-kV/300-mAs was associated with 40% lower radiation dose (mean dose-length product, 359 ± 66 vs 628 ± 112 mGy[Symbol: see text]cm; P < 0.001 ) with no significant difference in CNR (34.5 ± 13.4 vs 33.5 ± 10.4; P = 0.81) or MBF in non-ischaemic myocardium (0.95 ± 0.20 vs 0.99 ± 0.25 ml/min/g; P = 0.66). Studies obtained using 80-kV/370-mAs were associated with 30.9% higher maximal enhancement (804 ± 204 vs 614 ± 115 HU; P < 0.005), and 31.2% greater noise (22.7 ± 3.5 vs 17.4 ± 2.6; P < 0.001). CONCLUSIONS: Dynamic CTP using 80-kV/370-mA instead of 100-kV/300-mAs allowed 40% dose reduction without compromising image quality or MBF. Tube voltage of 80-kV should be considered for individuals with a normal BMI. KEY POINTS: • CT stress perfusion imaging (CTP) is increasingly used to assess myocardial function. • Dynamic CTP is feasible at 80-kV in patients with normal BMI. • An 80-kV/370-mAs protocol allows 40% dose reduction compared with 100-kV/300-mAs. • Contrast-to-noise ratio and myocardial blood flow of the two protocols were comparable.

Silencing of fas-associated death domain protects mice from septic lung inflammation and apoptosis.

RATIONALE: A better understanding of the molecular mechanisms involved in the pathogenesis of sepsis and its resultant organ failure and new therapeutic approaches and targets are urgently needed. Accumulating evidence suggests that apoptosis plays an important role in the pathophysiology of sepsis and that apoptosis may be detrimental in septic acute lung injury (ALI). OBJECTIVES: We tested the hypothesis that systemic administration of small interfering RNA (siRNA) targeting Fas-associated death domain (FADD), which recruits procaspase-8 into the death-inducing signaling complex, may be protective in septic ALI and mortality. METHODS: Polymicrobial sepsis was induced by cecal ligation and puncture (CLP) in BALB/c mice. In vivo delivery of siRNA was performed by using a transfection reagent at 10 hours after CLP. As a negative control, animals received nonsense (scrambled) siRNA. MEASUREMENTS AND MAIN RESULTS: In CLP-induced septic mice, surface expression of death receptors was up-regulated, and FADD was highly expressed. DNA fragmentation ladder and transferase-mediated dUTP nick end labeling assays showed that treatment with FADD siRNA suppressed apoptosis induction in septic lungs. This siRNA treatment prevented the ALI development in CLP mice, as indicated by the findings that blood-gas derangements, histologic lung damage, and increased pulmonary inflammatory cells were greatly improved. Finally, FADD siRNA administration dramatically improved the survival of CLP mice. CONCLUSIONS: These results indicate the pathophysiologic significance of the death receptor apoptotic pathway, including FADD, in septic ALI and the potential usefulness of FADD siRNA for gene therapy of the septic syndrome.

Data on correlation between CT-derived and MRI-derived myocardial extracellular volume.

This article describes data related to a research article titled "Estimation of myocardial extracellular volume fraction with cardiac CT in subjects without clinical coronary artery disease: A feasibility study", Kurita et al. (in press) [1]. Myocardial extracellular volume fraction (ECV) is an imaging biomarker that can elevate in various heart diseases. This article describes correlation between CT-derived and MRI-derived ECV in 24 myocardial segments in 8 patients. CT-derived ECV was obtained from pre-contrast and delayed-phase images acquired by using dual-source CT system. MRI-derived ECV was obtained by using modified Look-Locker inversion recovery sequence implemented on a 3 T MRI system.

Estimation of myocardial extracellular volume fraction with cardiac CT in subjects without clinical coronary artery disease: A feasibility study.

BACKGROUND: Use of CT for assessment of extracellular volume fraction (ECV) is a new approach toward the evaluation of diffuse and focal myocardial fibrosis. It has recently been demonstrated that a hybrid algorithm of half- and full-scan reconstruction can improve image quality of delayed-phase CT. OBJECTIVE: The purpose of this study was to evaluate reproducibility of CT measurement of ECV of the myocardium using pre-contrast and delayed-phase CT, and to investigate the association between ECV and location, age and gender in subjects without clinical coronary artery disease. METHODS: Thirty-eight subjects (ages 45-78, mean 65 years, 14 females) without coronary artery stenosis, stress perfusion deficits or myocardial delayed enhancement on comprehensive cardiac CT comprise the study population. Delayed-phase CT was reconstructed with the hybrid algorithm. ECV was calculated as a ratio of the change in Hounsfield unit of the myocardium and the left ventricular (LV) blood before and after contrast administration, multiplied by (1-hematocrit). RESULTS: Good inter- and intra-observer agreement was observed in CT measurement of ECV (intraclass correlation coefficient: 0.968 and 0.971, respectively). Mean ECV was 26.1 ± 2.0% (range 22.6-30.0%), and was positively related to age (r = 0.46, p = 0.003). Mean ECV in males was lower compared with females (25.5 ± 2.0% vs. 27.1 ± 1.8%, p = 0.02). There was no statistically significant difference in ECV between anterior, septal, inferior, and lateral segments. CONCLUSIONS: CT measurement of myocardial ECV showed high inter- and intra-observer reproducibility, and age-related increase and gender-related difference of ECV were demonstrated. This might enable additional CT evaluation of diffuse and focal myocardial fibrosis in various pathological conditions as part of a comprehensive cardiac CT examination.

Radiation-induced organizing pneumonia after stereotactic body radiotherapy for lung tumor.

The aim of this retrospective study was to investigate characteristics of organizing pneumonia (OP) after stereotactic body radiotherapy (SBRT) for lung tumor. Between September 2010 and June 2014, patients who were diagnosed as Stage I lung cancer and treated with SBRT at our institution were included in this study. A total of 78 patients (47 males with a median age of 80 years) were analyzed. The median follow-up period was 23 months. Five patients (6.4%) developed OP at 6-18 months after SBRT. The cumulative incidence of OP was 4.3% (95% confidence interval [CI], 1.1-11.0) and 8.2% (95% CI, 2.9-17.0) at 1 and 2 years, respectively. Tumor location (superior and middle lobe vs inferior lobe) was shown to be a borderline significant factor for the occurrence of OP ( P: = 0.069). In the subgroup analysis of patients with a radiographic follow-up period at least 6 months, or who died within 6 months after SBRT, 7 of 72 patients (9.7%) developed Grade 2 or 3 radiation pneumonitis (G2/3 RP) at 2-4 months after SBRT. A statistically significant association between G2/3 RP in the subacute phase and OP was shown ( P: = 0.040). In two of the five patients who developed OP, the symptoms and radiographic change were improved rapidly by corticosteroid administration. One patient had relapsed OP after suspending the treatment and re-administration was required. Three patients with minor symptoms were managed without corticosteroid administration and OP resolved without any relapse. The radiation-induced OP should be considered as one of the late lung injuries after SBRT for lung tumors.

Myocardial delayed enhancement with dual-source CT: advantages of targeted spatial frequency filtration and image averaging over half-scan reconstruction.

BACKGROUND: Clinical utility of myocardial delayed-enhancement CT is currently limited because of relatively poor contrast-to-noise ratio (CNR) and artifacts. Targeted spatial-frequency filtration (TSFF) is a hybrid algorithm of half- and full-scan reconstruction that can achieve both high temporal resolution and improved stability of myocardial signal. OBJECTIVE: The purpose of this study was to evaluate image quality of delayed-enhancement CT using TSFF with image averaging and its reproducibility in infarct assessment in comparison with conventional half-scan reconstruction (HALF). METHODS: Forty patients with suspected coronary artery disease underwent delayed-enhancement CT with HALF and TSFF using dual-source CT. Two blinded readers independently determined the presence and size of delayed enhancement. Image quality, signal-to-noise ratio and CNR were assessed. The presence of delayed enhancement on CT was compared with magnetic resonance imaging in 12 patients. RESULTS: TSFF with averaging of 4 image stacks acquired during 1 breathhold demonstrated significantly better image quality compared with HALF. Good left ventricular lumen-myocardium contrast was consistently achieved with TSFF in patients who received iodine dose of >600 mg I/kg. The signal-to-noise ratio and CNR were 11.3 ± 4.2 and 4.5 ± 1.6 by TSFF, being significantly higher than those by HALF (7.9 ± 2.9 and 3.3 ± 1.8; P < .01 for both). Interobserver reproducibility of infarct sizing was markedly improved by using TSFF instead of HALF (intraclass correlation coefficient: 0.86 vs 0.50). Agreement with magnetic resonance imaging by kappa statistics was 0.85 with TSFF and 0.74 with HALF. CONCLUSIONS: TSFF with image averaging can significantly improve image quality of delayed-enhancement CT and considerably enhances interobserver reproducibility of infarct sizing.