Unintended and accidental medical radiation exposures in radiology: guidelines on investigation and prevention.

This paper sets out guidelines for managing radiation exposure incidents involving patients in diagnostic and interventional radiology. The work is based on collation of experiences from representatives of international and national organizations for radiologists, medical physicists, radiographers, regulators, and equipment manufacturers, derived from an International Atomic Energy Agency Technical Meeting. More serious overexposures can result in skin doses high enough to produce tissue reactions, in interventional procedures and computed tomography, most notably from perfusion studies. A major factor involved has been deficiencies in training of staff in operation of equipment and optimization techniques. The use of checklists and time outs before procedures commence, and dose alerts when critical levels are reached during procedures, can provide safeguards to reduce the risks of these effects occurring. However, unintended and accidental overexposures resulting in relatively small additional doses can take place in any diagnostic or interventional x-ray procedure and it is important to learn from errors that occur, as these may lead to increased risks of stochastic effects. Such events may involve the wrong examinations, procedural errors, or equipment faults. Guidance is given on prevention, investigation, and dose calculation for radiology exposure incidents within healthcare facilities. Responsibilities should be clearly set out in formal policies, and procedures should be in place to ensure that root causes are identified and deficiencies addressed. When an overexposure of a patient or an unintended exposure of a foetus occurs, the foetal, organ, skin, and/or effective dose may be estimated from exposure data. When doses are very low, generic values for the examination may be sufficient, but a full assessment of doses to all exposed organs and tissues may sometimes be required. The use of general terminology to describe risks from stochastic effects is recommended rather than the calculation of numerical values, as these are misleading when applied to individuals.

Three-dimensional simulation of lung nodules for paediatric multidetector array CT.

The purpose of this study was to develop and validate a technique for three-dimensional (3D) modelling of small lung nodules on paediatric multidetector array computed tomography (MDCT) images. Clinical images were selected from 21 patients (<18 years old) who underwent MDCT examinations. Sixteen of the patients had one or more real lung nodules with diameters between 2.5 and 6 mm. A mathematical simulation technique was developed to emulate the 3D characteristics of the real nodules. To validate this technique, MDCT images of 34 real nodules and 55 simulated nodules were randomised and rated independently by four experienced paediatric radiologists on a continuous scale of appearance between 0 (definitely not real) and 100 (definitely real). Receiver operating characteristic (ROC) analysis, t-test, and equivalence test were performed to assess the radiologists' ability to distinguish between simulated and real nodules. The two types of nodules were also compared in terms of measured shape and contrast profile irregularities. The areas under the ROC curves were 0.59, 0.60, 0.40, and 0.63 for the four observers. Mean score differences between simulated and real nodules were -8, -11, 13, and -4 for the four observers with p-values of 0.17, 0.06, 0.17, and 0.26, respectively. The simulated and real nodules were perceptually equivalent and had comparable shape and contrast profile irregularities. In conclusion, mathematical simulation is a feasible technique for creating realistic small lung nodules on paediatric MDCT images.

Dose reduction in paediatric MDCT: general principles.

The number of multi-detector array computed tomography (MDCT) examinations performed per annum continues to increase in both the adult and paediatric populations. Estimates from 2003 suggested that CT contributed 17% of a radiology department's workload, yet was responsible for up to 75% of the collective population dose from medical radiation. The effective doses for some CT examinations today overlap with those argued to have an increased risk of cancer. This is especially pertinent for paediatric CT, as children are more radiosensitive than adults (and girls more radiosensitive than boys). In addition, children have a longer life ahead of them, in which radiation induced cancers may become manifest. Radiologists must be aware of these facts and practise the ALARA (as low as is reasonably achievable) principle, when it comes to deciding CT protocols and parameters.

Hepatocellular carcinoma in glycogen storage disease type Ia: a case series.

We present a series of 8 patients (6 males, 2 females) with hepatocellular carcinoma (HCC) and glycogen storage disease type Ia (GSD Ia). In this group, the age at which treatment was initiated ranged from birth to 39 years (mean 9.9 years). All patients but one were noncompliant with treatment. Hepatic masses were first detected at an age range of 13-45 years (mean 28.1 years). Age at diagnosis of HCC ranged from 19 to 49 years (mean 36.9 years). Duration between the diagnosis of liver adenomas and the diagnosis of HCC ranged from 0 to 28 years (mean 8.8 years, SD = 11.5). Two patients had positive hepatitis serologies (one hepatitis B, one hepatitis C). Alpha-fetoprotein (AFP) was normal in 6 of the 8 patients. Carcinoembryonic antigen (CEA) was normal in the 5 patients in which it was measured. Current guidelines recommend abdominal ultrasonography with AFP and CEA levels every 3 months once patients develop hepatic lesions. Abdominal CT or MRI is advised when the lesions are large or poorly defined or are growing larger. We question the reliability of AFP and CEA as markers for HCC in GSD Ia. Aggressive interventional management of masses with rapid growth or poorly defined margins may be necessary to prevent the development of HCC in this patient population.

Imaging of paediatric mediastinal masses.

A review of mediastinal masses in children is important for several reasons. First, the mediastinum is the common location for thoracic masses in children. Second, the type and frequency of masses differ in children compared with adults. Third, anatomic variations can be misinterpreted as mediastinal masses. Lastly, there are special technical considerations for imaging mediastinal masses in children. This article is derived from a literature review and the author's personal experience with imaging mediastinal masses. Figures are used to illustrate the spectrum of lesions in the anterior, middle and posterior mediastinum in children. Familiarity with the types of masses, frequency of presentation and imaging features are extremely valuable in determining the appropriate subsequent care for the child.

Transhepatic catheterization using ultrasound-guided access.

The efficacy and safety of ultrasound guidance to obtain transhepatic access for cardiac catheterization were investigated in this study. The transhepatic route for access to perform cardiac catheterization has become an acceptable alternative when conventional routes of access have failed. However, the use of ultrasound to guide transhepatic access has not been reported in the literature. We performed a retrospective chart review. Patient characteristics, indications for catheterization, procedures performed, and complications were recorded. All patients who underwent transhepatic cardiac catheterization at Duke University Medical Center were included in this study. Eight patients underwent 12 catheterizations. The median age was 5.3 years (range, 9 months to 13 years) and median weight 18.7 kg (range, 7.1-44.8 kg). Seven catheterizations were diagnostic and 5 were interventional. There were no complications. Transhepatic access with ultrasound guidance is a safe and effective option for obtaining venous access for cardiac catheterization.

Hepatic storage of glycogen in Niemann-Pick disease type B.

We report 2 patients with confirmed Niemann-Pick disease, type B, with previous diagnoses of glycogen storage disease based on excessive glycogen on liver biopsy specimens. These cases emphasize the importance of a complete evaluation, including biochemical confirmation, for patients with suspected metabolic storage diseases.

Reliability of CXR for the diagnosis of bronchopulmonary dysplasia.

BACKGROUND: Bronchopulmonary dysplasia (BPD) continues to be prevalent, despite new treatment, in part because of increased survival in less mature infants. Investigations of new treatments have been hampered by a lack of universally accepted diagnostic criteria. Radiographic scoring systems have been developed to provide objective assessment of lung injury and risk for chronic lung disease. OBJECTIVE: We sought to test the reliability of a recently reported system using chest radiography as the main tool for diagnosis of BPD. MATERIALS AND METHODS: One hundred chest radiographs, half demonstrating BPD and the other half without BPD, were analyzed by pediatric radiologists and by a neonatologist, using the Weinstein score (1-6, depending on increasing radiographic severity). The reliability of this scoring system was tested by kappa (k) statistics. RESULTS: Reliability at the lowest threshold (dividing score 1 from score > or = 2) was unacceptably low in this population. Reliability increased with inclusion of higher BPD scores in the comparison groups: 1-3 versus 4-6. CONCLUSION: Using the chest radiograph for the prediction of BPD is not reliable between different observers except at the two extremes of the disease.

Minimizing radiation dose for pediatric body applications of single-detector helical CT: strategies at a large Children's Hospital.

Adjustments of the standard helical CT protocols for adults can result in reduced radiation dose when imaging children. It is the radiologist's responsibility to critically evaluate the CT techniques used at their institution. Adjustments to CT protocols should be made to choose the appropriate mA and pitch when imaging children.

Helical CT of the body: are settings adjusted for pediatric patients?

OBJECTIVE: Our objective was to determine whether adjustments related to patient age are made in the scanning parameters that are determinants of radiation dose for helical CT of pediatric patients. SUBJECTS AND METHODS: This prospective investigation included all body (chest and abdomen) helical CT examinations (n = 58) of neonates, infants, and children (n = 32) referred from outside institutions for whom radiologic consultation was requested. Information recorded included tube current, kilovoltage, collimation, and pitch. Examinations were arbitrarily grouped on the basis of the individual's age: group A, 0-4 years; group B, 5-8 years; group C, 9-12 years; and group D, 13-16 years old. RESULTS: Thirty-one percent (18/58) of the CT examinations were of the chest and 69% (40/58) were of the abdomen. Sixteen percent (9/58) of the CT examinations were combined chest and abdomen. In 22% (2/9) of these combined examinations, tube current was adjusted between the chest and abdomen CT; in one (11%) of these examinations, the tube current was higher for the chest than for the abdomen portion of the CT examination. The mean tube current setting for chest was 213 mA and was 206 mA for the abdomen, with no evident adjustment in tube current based on the age of the patient. Fifty-six percent of the examinations of neonates, infants, or children 8 years old or younger were performed at a collimation of greater than 5 mm and 53% of these examinations were performed using a pitch of 1.0. CONCLUSION: Pediatric helical CT parameters are not adjusted on the basis of the examination type or the age of the child. In particular, these results suggest that pediatric patients may be exposed to an unnecessarily high radiation dose during body CT.

Differentiating normal from abnormal inferior thoracic paravertebral soft tissues on chest radiography in children.

OBJECTIVE: The purposes of this investigation were to define the normal appearances, define factors that have the potential to influence appearance, and establish defined criteria to differentiate normal from abnormal appearances of posteroinferior paravertebral soft tissues on chest radiography in children. SUBJECTS AND METHODS: Paravertebral soft tissues were evaluated on frontal chest radiographs in 23 children with documented abnormalities and 275 children without abnormalities in the region. The frequency of visualization, course, width, and factors (patient positioning, age, and sex) potentially influencing the appearance of paravertebral soft tissues were determined. Inferolateral course and width greater than that of the adjacent pedicle were evaluated as criteria for abnormality. RESULTS: Only 28% of the children without abnormalities had paravertebral soft tissues visualized, and the frequency of visualization directly increased with age (p = 0.001). For identification of abnormal cases on the left side, width greater than the adjacent pedicle had a sensitivity of 100% and a specificity of 98%, and inferolateral course had a sensitivity of 86% and a specificity of 95%. Visualization on the right side (n = 5) was always abnormal. Six normal cases had a width greater than that of the adjacent pedicle on the left side on initial radiographs obtained with supine positioning and met normal criteria on repeated radiographs with upright positioning. CONCLUSION: Width greater than the adjacent pedicle is the best radiographic criterion for differentiation of abnormal from normal left-sided paravertebral soft tissues, particularly on radiographs obtained with upright positioning. Identifiable right-sided paravertebral soft tissue is always abnormal. These criteria are useful aids in determining the need for additional imaging, such as CT.

Elevated renal rind.

We describe the findings from a group of five infants ranging in age from 3 weeks to 13 months who had shock of differing causes. In each case, sonographic evaluation of the abdomen revealed bilateral perirenal hyperechoic bands several millimeters thick, surrounding a thin, hypoechoic rim of fluid. The findings were identified during the acute phase of each child's illness and persisted after the patient's condition had clinically improved, eventually resolving in the three surviving children. We have dubbed this sign the "elevated renal rind." We believe that the changes are likely secondary to systemic inflammatory mediators and do not reflect localized intraabdominal disease.