Computed tomography commissioning programmes: how to obtain a reliable MTF with an automatic approach?

The purpose of this study was to assess the spatial resolution of a computed tomography (CT) scanner with an automatic approach developed for routine quality controls when varying CT parameters. The methods available to assess the modulation transfer functions (MTF) with the automatic approach were Droege's and the bead point source (BPS) methods. These MTFs were compared with presampled ones obtained using Boone's method. The results show that Droege's method is not accurate in the low-frequency range, whereas the BPS method is highly sensitive to image noise. While both methods are well adapted to routine stability controls, it was shown that they are not able to provide absolute measurements. On the other hand, Boone's method, which is robust with respect to aliasing, more resilient to noise and provides absolute measurements, satisfies the commissioning requirements perfectly. Thus, Boone's method combined with a modified Catphan 600 phantom could be a good solution to assess CT spatial resolution in the different CT planes.

Severe postnatally acquired cytomegalovirus infection presenting with colitis, pneumonitis and sepsis-like syndrome in an extremely low birthweight infant.

Few cases of severe postnatally acquired cytomegalovirus (CMV) infection are reported in premature infants. We report on an extremely low birthweight (ELBW) preterm infant who presented with a sepsis-like syndrome and multiple organ involvement, notably pneumonitis and colitis. The course of infection was assessed by repeated analysis of urine, tracheal aspirates and blood. The patient was given intravenous ganciclovir. The clinical course was rapidly favorable. Development of neutropenia led to the discontinuation of the antiviral treatment after 28 days. Follow-up showed moderate white matter anomalies on cerebral MRI, a transient hypoacusis and a mild developmental delay at 18 months of corrected age. To the best of our knowledge, this is the first description of a severe combination of pneumonitis and colitis in postnatal CMV infection. Many issues remain controversial and are discussed. We propose that antiviral treatment should be considered in severe postnatal CMV infection in ELBW patients.

Perfusion abnormalities in hemimegalencephaly.

INTRODUCTION: Cerebrovascular changes are rarely discussed in patients with hemimegalencephaly. These alterations have previously been associated with epileptical activity. CASE: We report the case of a 36-week gestation neonate presenting with total right hemimegalencephaly, as demonstrated by a magnetic resonance imaging (MRI) performed in the first days of life. Perfusion-weighted imaging displayed a clear hypervascularization of the right hemisphere. Diffusion-tensor imaging showed an arrangement of white matter fibers concentrically around the ventricle on the right hemisphere. AngioMRI showed an obvious asymmetry in the size of the middle cerebral arteries, with the right middle cerebral artery being prominent. The baby was free of clinical seizures during his first week of life. An electroencephalogram at that time displayed an asymmetric background activity, but no electrical seizures. CONCLUSION: Perfusion anomalies in hemimegalencephaly may not necessarily be related to epileptical activity, but may be related to vessel alterations.

[Tumoral calcinosis in a child: a case report and review]. / Calcinose tumorale, à propos d'un cas pédiatrique.

Tumoral calcinosis (Ct) is a rare pathology of unknown origin.We present the clinical, imaging ( including CT and MRI), surgical and pathology findings of Ct in a 9 year-old boy who presented with an incidental finding of a large elbow mass. The MR aspect of Ct has been reported only once and this case is the second description in a child. The association of Ct and dermatomyositis, as reported hereby, has also been described only once. With respect to treatment alternatives, we believe that it is important for radiologists to recognise this rare pathology in pediatric patients.

Detection of ingested cocaine-filled packets--diagnostic value of unenhanced CT.

PURPOSE: Emergency departments are facing nowadays an increasing number of illegal drug-related health problems, associated with medicolegal and/or social consequences. Body stuffers are street cocaine dealers, who either store wrapped packets of drugs in their rectum or hastily swallow them, prompted by fear of police's arrest. These packets can be life threatening in case of leakage. We evaluate the diagnostic value of unenhanced multidetector CT (MDCT) for detection of cocaine-filled packets (CFP) ingested by body stuffers in a phantom model. MATERIALS AND METHODS: Our phantom simulated normal bowel contents in which a varying number of true and false CFP were randomly mixed. Both only differ in radiological density. During 18 different reading sessions, four radiologists independently evaluated the presence and number of true and false CFP. Interobserver agreement, sensitivity, specificity, positive and negative predictive value were calculated. RESULTS: Interobserver agreement for detection of any packets, for visualization of true, and false CFP was good (kappa=0.63, 0.74 and 0.58, respectively). Sensitivity, specificity, positive and negative predictive value for detection of any packets was 95.6%, 100%, 100% and 62.5%, respectively; for visualization of the true CFP 86.5%, 100%, 100% and 77.6%, respectively; and for the false packets 98.1%, 65%, 88.6% and 87.5%, respectively. CONCLUSION: Unenhanced MDCT without bowel preparation is a fast, reliable and easily reproducible imaging modality for the immediate detection of ingested CFP, thus facilitating medicolegal management of body stuffers.

Influence of cassette type on the DQE of CR systems.

In our recent paper by Monnin et al. [Med. Phys. 33, 411-420 (2006)], an objective analysis of the relative performance of a computed radiography (CR) system using both standard single-side (ST-VI) and prototype dual-side read (ST-BD) plates was reported. The presampled modulation transfer function (MTF), noise power spectrum (NPS), and detective quantum efficiency (DQE) for the systems were determined at three different beam qualities representative of paediatric chest radiography, at an entrance detector air kerma of 5 microGy. Experiments demonstrated that, compared to the standard single-side read system, the MTF for the dual-side read system was slightly reduced, but a significant decrease in image noise resulted in a marked increase in DQE (+40%) in the low spatial frequency range. However, the DQE improvement for the ST-BD plate decreased with increasing spatial frequency, and, at spatial frequencies above 2.2 mm(-1), the DQE of the dual-side read system was lower than that of the single-side one.

[Patient dose optimization in pediatric computerized tomography]. / Optimisation des doses en tomographie computérisée pédiatrique.

The development of CT applications might become a public health problem if no effort is made on the justification and the optimisation of the examinations. This paper presents some hints to assure that the risk-benefit compromise remains in favour of the patient, especially when one deals with the examinations of young patients. In this context a particular attention has to be made on the justification of the examination. When performing the acquisition one needs to optimise the extension of the volume investigated together with the number of acquisition sequences used. Finally, the use of automatic exposure systems, now available on all the units, and the use of the Diagnostic Reference Levels (DRL) should allow help radiologists to control the exposure of their patients.

An image quality comparison of standard and dual-side read CR systems for pediatric radiology.

An objective analysis of image quality parameters was performed for a computed radiography (CR) system using both standard single-side and prototype dual-side read plates. The pre-sampled modulation transfer function (MTF), noise power spectrum (NPS), and detective quantum efficiency (DQE) for the systems were determined at three different beam qualities representative of pediatric chest radiography, at an entrance detector air kerma of 5 microGy. The NPS and DQE measurements were realized under clinically relevant x-ray spectra for pediatric radiology, including x-ray scatter radiations. Compared to the standard single-side read system, the MTF for the dual-side read system is reduced, but this is offset by a significant decrease in image noise, resulting in a marked increase in DQE (+40%) in the low spatial frequency range. Thus, for the same image quality, the new technology permits the CR system to be used at a reduced dose level.

[Undifferentiated sarcoma of the liver: a rare tumor of childhood]. / Le sarcome indifférencié du foie: une tumeur rare chez l'enfant.

UNLABELLED: Undifferentiated sarcoma of the liver is a rare primary tumor of childhood: only about 150 cases have been reported in the literature. CASE-REPORT: A 10 year-old girl was admitted because of diarrhea and weight loss. Sonography, then CT-scan and MRI showed a large tumor of the liver. COMMENTS: In the differential diagnosis of primary liver tumors in children, one should think about undifferentiated sarcoma of the liver, especially if imaging shows haemorrhagic foci and if sonography and CT/MRI display a discordant appearance. Survival has improved in the last decade due to agressive surgery and intensive chemotherapy.

Management of patient dose and image noise in routine pediatric CT abdominal examinations.

The aim was to propose a strategy for finding reasonable compromises between image noise and dose as a function of patient weight. Weighted CT dose index (CTDI(w)) was measured on a multidetector-row CT unit using CTDI test objects of 16, 24 and 32 cm in diameter at 80, 100, 120 and 140 kV. These test objects were then scanned in helical mode using a wide range of tube currents and voltages with a reconstructed slice thickness of 5 mm. For each set of acquisition parameter image noise was measured and the Rose model observer was used to test two strategies for proposing a reasonable compromise between dose and low-contrast detection performance: (1) the use of a unique noise level for all test object diameters, and (2) the use of a unique dose efficacy level defined as the noise reduction per unit dose. Published data were used to define four weight classes and an acquisition protocol was proposed for each class. The protocols have been applied in clinical routine for more than one year. CTDI(vol) values of 6.7, 9.4, 15.9 and 24.5 mGy were proposed for the following weight classes: 2.5-5, 5-15, 15-30 and 30-50 kg with image noise levels in the range of 10-15 HU. The proposed method allows patient dose and image noise to be controlled in such a way that dose reduction does not impair the detection of low-contrast lesions. The proposed values correspond to high- quality images and can be reduced if only high-contrast organs are assessed.

Repeated surgical excision for an unusual variant of nephroblastoma: case report and review of the literature.

Bilateral fetal rhabdomyomatous nephroblastoma is a rare variant of Wilms' Tumor. The authors report the evolution over 48 months of a 10-month-old baby with bilateral nephroblastoma for which a left nephrectomy was initially performed. A right kidney tumor was enucleated preserving the kidney. The transformation of the primary tumor into a completely differentiated cystic nephroblastoma or nephromalike tumor and the appearance of a metachronous lesion was seen. This report emphasizes the role of nephron-sparing surgery in bilateral Wilms' Tumor when a benign transformation occurs under chemotherapy.

Paranasal sinuses in children: size evaluation of maxillary, sphenoid, and frontal sinuses by magnetic resonance imaging and proposal of volume index percentile curves.

Our objective was to establish the age-related 3D size of maxillary, sphenoid, and frontal sinuses. A total of 179 magnetic resonance imaging (MRI) of children under 17 years (76 females, 103 males) were included and sinuses were measured in the three axes. Maxillary sinuses measured at birth (mean+/-standard deviation) 7.3+/-2.7 mm length (or antero-posterior)/4.0+/-0.9 mm height (or cranio-caudal)/2.7+/-0.8 mm width (or transverse). At 16 years old, maxillary sinus measured 38.8+/-3.5 mm/36.3+/-6.2 mm/27.5+/-4.2 mm. Sphenoid sinus pneumatization starts in the third year of life after conversion from red to fatty marrow with mean values of 5.8+/-1.4 mm/8.0+/-2.3 mm/5.8+/-1.0 mm. Pneumatization progresses gradually to reach at 16 years 23.0+/-4.5 mm/22.6+/-5.8 mm/12.8+/-3.1 mm. Frontal sinuses present a wide variation in size and most of the time are not valuable with routine head MRI techniques. They are not aerated before the age of 6 years. Frontal sinuses dimensions at 16 years were 12.8+/-5.0 mm/21.9+/-8.4 mm/24.5+/-13.3 mm. A sinus volume index (SVI) of maxillary and sphenoid sinus was computed using a simplified ellipsoid volume formula, and a table with SVI according to age with percentile variations is proposed for easy clinical application. Percentile curves of maxillary and sphenoid sinuses are presented to provide a basis for objective determination of sinus size and volume during development. These data are applicable to other techniques such as conventional X-ray and CT scan.

Imaging of cavitary necrosis in complicated childhood pneumonia.

The aim of this study was to illustrate the chest radiographs (CR) and CT imaging features and sequential findings of cavitary necrosis in complicated childhood pneumonia. Among 30 children admitted in the Pediatric Intensive Care Unit for persistent or progressive pneumonia, respiratory distress or sepsis despite adequate antibiotic therapy, a study group of 9 children (5 girls and 4 boys; mean age 4 years) who had the radiographic features and CT criteria for cavitary necrosis complicated pneumonia was identified. The pathogens identified were Streptococcus pneumoniae( n=4), Aspergillus( n=2), Legionella( n=1), and Staphylococcus aureus( n=1). Sequential CR and CT scans were retrospectively reviewed. Follow-up CR and CT were evaluated for persistent abnormalities. Chest radiographs showed consolidations in 8 of the 9 patients. On CT examination, cavitary necrosis was localized to 1 lobe in 2 patients and 7 patients showed multilobar or bilateral areas of cavitary necrosis. In 3 patients of 9, the cavitary necrosis was initially shown on CT and visualization by CR was delayed by a time span varying from 5 to 9 days. In all patients with cavities, a mean number of five cavities were seen on antero-posterior CR, contrasting with the multiple cavities seen on CT. Parapneumonic effusions were shown by CR in 3 patients and in 5 patients by CT. Bronchopleural fistulae were demonstrated by CT alone ( n=3). No purulent pericarditis was demonstrated. The CT scan displayed persistent residual pneumatoceles of the left lower lobe in 2 patients. Computed tomography is able to define a more specific pattern of abnormalities than conventional CR in children with necrotizing pneumonia and allows an earlier diagnosis of this rapidly progressing condition. Lung necrosis and cavitation may also be associated with Aspergillus or Legionella pneumonia in the pediatric population.

Imaging of blunt arterial trauma of the upper extremity in children.

We report four patients with blunt arterial trauma of the upper limb following unusual mechanisms of injury in two patients (one fell on the handlebars of his bicycle, the second was crushed by a moving lawn mower) and due to bicycle accidents in two further patients. The use of digital subtraction angiography (DSA) in all patients, together with colour Doppler imaging (CDI) in one patient, provided optimum preoperative identification and localisation of the arterial lesions.

Brain involvement in haemolytic-uraemic syndrome: MRI features of coagulative necrosis.

We describe radiological demonstration of brain involvement in haemolytic-uraemic syndrome (HUS) in two siblings with a very different clinical course. While the brother presented with a mild, reversible encephalopathy, his sister developed high-signal lesions in the cortex, putamen and caudate nucleus on T1-weighted images, seen as dense areas on CT. Biopsy revealed coagulative necrosis due to microthrombosis without haemorrhage, calcification or infection. These findings suggest a possible prognostic role for MRI in cases of encephalopathy due to HUS.

Non-invasive imaging of the ring-sling complex in children.

The Ring-Sling Complex is an uncommon, congenital vascular and tracheobronchial malformation with a persistent high death rate. We report three patients in whom computed tomography (CT) and magnetic resonance imaging (MRI) were used for the preoperative diagnosis and for staging of the morphologic tracheal and vascular anomalies.

Fatal outcome in a female monozygotic twin with X-linked hypohydrotic ectodermal dysplasia (XLHED) due to a de novo t(X;9) translocation with probable disruption of the EDA gene.

UNLABELLED: Ectodermal dysplasias are a group of congenital disorders with defective development of the epidermis and its appendages. X-linked hypohydrotic ectodermal dysplasia (XLHED; OMIM 305100) is the most common form of ectodermal dysplasia. We report on two monozygotic twin girls with XLHED due to a t(X;9) translocation causing a disruption of the EDA gene and non random inactivation of the normal X chromosome. One of the girls died unexpectedly at 2.5 years of age. Autopsy revealed that lack of normal tracheobronchial secretions leading to complete tracheal obstruction by mucous debris was the probable cause of death. CONCLUSION: Morbidity and mortality of ectodermal dysplasias in infancy and early childhood can be significant. Early diagnosis by paediatricians is important and complications should be anticipated.

Lymphocytic interstitial pneumonia in children with AIDS: high-resolution CT findings.

Pulmonary involvement in children with acquired immunodeficiency syndrome (AIDS) represents a wide spectrum of diseases. Among the non-infectious, non-neoplastic affections associated with AIDS, lymphocytic interstitial pneumonia (LIP) is now a well-recognized entity, but its radiological pattern studied with high-resolution computed tomography (HRCT) has rarely been described in children. The aim of this study was to illustrate the HRCT spectrum of pulmonary involvement in children with LIP and to evaluate its usefulness in the early diagnosis of this entity. Twelve children with AIDS, aged 3-9 years (mean age 5 years 7 months), underwent chest radiographs and HRCT. A control group of 7 healthy aged-matched children was also studied in the same conditions. Diagnosis of LIP was based on clinical data and HRCT findings. Eight children of 12 had a reticulonodular pattern on chest radiographs. Two children had normal chest films and two children showed peribronchiolar thickening. High-resolution CT displayed micronodules, 1-3 mm in diameter, with a perilymphatic distribution in all patients. High-resolution CT demonstrated also subpleural nodules in children without reticulonodular opacities on chest radiographs. High-resolution CT is able to define a more specific pattern of abnormalities than conventional chest radiographs in children with LIP, allows an earlier and more confident diagnosis and may be useful for the detection of other pathologies associated with AIDS, such as opportunistic infections or superimposed malignancies.

[Percutaneous nephrostomy in treatment of urinary tract obstructions and malformations in the child]. / Place de la néphrostomie percutanée dans le traitement des lésions urinaires obstructives et malformatives chez l'enfant.

Percutaneous nephrostomy (NP) is a routinely applied procedure in adults, but sparsely reported in the pediatric population. We report the treatment of acute obstructive renal diseases in 15 children aged one day to 6 years. The causes of obstruction included pelvi-ureteral junction stenosis (10 cases) by calculus or complicated by pyonephrosis, vesico-ureteral junction stenosis (2 cases), urethral valves and stenosis (2 cases) and one complex urogenital malformation. Catheter placement was performed under ultrasonographic guidance without immediate complication. NP should be considered as a primary preoperative modality for urinary tract obstruction in the pediatric population.

An uncommon G375C substitution in a newborn with achondroplasia.

We report a G-to-T de novo transversion mutation causing the substitution of a glycine with a cysteine (G375C) in a newborn with achondroplasia. This rare observation confirms allelic heterogeneity.