Development and validation of a low dose simulator for computed tomography

To develop and validate software for facilitating observer studies on the effect of radiation exposure on the diagnostic value of computed tomography (CT). A low dose simulator was developed which adds noise to the raw CT data. For validation two phantoms were used: a cylindrical test object and an anthropomorphic phantom. Images of both were acquired at different dose levels by changing the tube current of the acquisition (500 mA to 20 mA in five steps). Additionally, low dose simulations were performed from 500 mA downwards to 20 mA in the same steps. Noise was measured within the cylindrical test object and in the anthropomorphic phantom. Finally, noise power spectra (NPS) were measured in water. The low dose simulator yielded similar image quality compared with actual low dose acquisitions. Mean difference in noise over all comparisons between actual and simulated images was 5.7 +/- 4.6% for the cylindrical test object and 3.3 +/- 2.6% for the anthropomorphic phantom. NPS measurements showed that the general shape and intensity are similar. The developed low dose simulator creates images that accurately represent the image quality of acquisitions at lower dose levels and is suitable for application in clinical studies.Radiolog

Radiation dose reduction at a price: the effectiveness of a male gonadal shield during helical CT scans

BACKGROUND: It is estimated that 60 million computed tomography (CT) scans were performed during 2006, with approximately 11% of those performed on children age 0–15 years. Various types of gonadal shielding have been evaluated for reducing exposure to the gonads. The purpose of this study was to quantify the radiation dose reduction to the gonads and its effect on image quality when a wrap-around male pediatric gonad shield was used during CT scanning. This information is obtained to assist the attending radiologist in the decision to utilize such male gonadal shields in pediatric imaging practice. METHODS: The dose reduction to the gonads was measured for both direct radiation and for indirect scattered radiation from the abdomen. A 6 cm(3 )ion chamber (Model 10X5-6, Radcal Corporation, Monrovia, CA) was placed on a Humanoid real bone pelvic phantom at a position of the male gonads. When exposure measurements with shielding were made, a 1 mm lead wrap-around gonadal shield was placed around the ion chamber sensitive volume. RESULTS: The use of the shields reduced scatter dose to the gonads by a factor of about 2 with no appreciable loss of image quality. The shields reduced the direct beam dose by a factor of about 35 at the expense of extremely poor CT image quality due to severe streak artifacts. CONCLUSION: Images in the direct exposure case are not useful due to these severe artifacts and the difficulties in positioning these shields on patients in the scatter exposure case may not be warranted by the small absolute reduction in scatter dose unless it is expected that the patient will be subjected to numerous future CT scans

RETRATO DE SEÑOR [Material gráfico]

Copia digital. Madrid : Ministerio de Educación, Cultura y Deporte. Subdirección General de Coordinación Bibliotecaria, 201

Posttraumatic levels of liver enzymes can reduce the need for CT in children: a retrospective cohort study

BACKGROUND: Computed tomography (CT) is the gold standard in the initial evaluation of the hemodynamically stable patient with suspected liver trauma. However, the adverse effects of radiation exposure are of specific concern in the pediatric population. It is therefore desirable to explore alternative diagnostic modalities. Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) are hepatic enzymes, which are elevated in peripheral blood in relation to liver injury. The aim of the present study was to investigate a potential role of normal liver transaminase levels in the decision algorithm in suspected pediatric blunt liver trauma. METHODS: Retrospective analysis of consecutively collected data from children (0–17 years) with blunt liver trauma, admitted to a single trauma centre in Denmark, between 2000 and 2013. Patients underwent abdominal CT during initial evaluation, and initial AST and/or ALT was measured. Based on local guidelines, we set the threshold for blood AST and ALT level to 50 IU/L. Nonparametric statistical tests were used. RESULTS: Sixty consecutive children with liver injury following blunt abdominal trauma were enrolled in the study. All patients with normal AST and/or ALT level were treated conservatively with success. Information on both AST and ALT was available in 47 children. Of these 47 children, three children had AST and ALT levels ≤50 IU/L. These children suffered from grade I liver injuries, and were treated conservatively with no complications. DISCUSSION: All children who presented with blunt liver injury and AST and ALT levels ≤50 IU/L did not require treatment. These findings indicate that AST and ALT could be included in an updated management algorithm as a screening method to avoid abdominal CT. Notable limitations to the study was the retrospective method of data collection, without inclusion of a control group. CONCLUSIONS: CT seems superfluous in the initial evaluation of hemodynamically stable children with suspected blunt liver injury and blood AST and ALT levels ≤50 IU/L

MR fluoroscopy in vascular and cardiac interventions (review)

Vascular and cardiac disease remains a leading cause of morbidity and mortality in developed and emerging countries. Vascular and cardiac interventions require extensive fluoroscopic guidance to navigate endovascular catheters. X-ray fluoroscopy is considered the current modality for real time imaging. It provides excellent spatial and temporal resolution, but is limited by exposure of patients and staff to ionizing radiation, poor soft tissue characterization and lack of quantitative physiologic information. MR fluoroscopy has been introduced with substantial progress during the last decade. Clinical and experimental studies performed under MR fluoroscopy have indicated the suitability of this modality for: delivery of ASD closure, aortic valves, and endovascular stents (aortic, carotid, iliac, renal arteries, inferior vena cava). It aids in performing ablation, creation of hepatic shunts and local delivery of therapies. Development of more MR compatible equipment and devices will widen the applications of MR-guided procedures. At post-intervention, MR imaging aids in assessing the efficacy of therapies, success of interventions. It also provides information on vascular flow and cardiac morphology, function, perfusion and viability. MR fluoroscopy has the potential to form the basis for minimally invasive image–guided surgeries that offer improved patient management and cost effectiveness

Posterior fossa epidural hematomas in children: clinical experience with 40 cases

Object. Traumatic posterior fossa epidural hematoma (PFEDH) is rare, but among children it may have a slightly higher incidence. With the widespread use of CT scanning, the diagnosis of PFEDH can be established more accurately, leading to an increased incidence of the lesion and possibly to a better patient prognosis. This study presents 40 pediatric cases with PFEDH