François Gudinchet

Iterative reconstruction methods in two different MDCT scanners: Physical metrics and 4-alternative forced-choice detectability experiments – A phantom approach

This paper characterizes and evaluates the potential of three commercial CT iterative reconstruction methods (ASIR™, VEO™ and iDose⁴(™)) for dose reduction and image quality improvement. We measured CT number accuracy, standard deviation (SD), noise power spectrum (NPS) and modulation transfer function (MTF) metrics on Catphan phantom images while five human observers performed four-alternative forced-choice (4AFC) experiments to assess the detectability of low- and high-contrast objects embedded in two pediatric phantoms. Results show that 40% and 100% ASIR as well as iDose⁴ levels 3 and 6 do not affect CT number and strongly decrease image noise with relative SD constant in a large range of dose. However, while ASIR produces a shift of the NPS curve apex, less change is observed with iDose⁴ with respect to FBP methods. With second-generation iterative reconstruction VEO, physical metrics are even further improved: SD decreased to 70.4% at 0.5 mGy and spatial resolution improved to 37% (MTF(50%)). 4AFC experiments show that few improvements in detection task performance are obtained with ASIR and iDose⁴, whereas VEO makes excellent detections possible even at an ultra-low-dose (0.3 mGy), leading to a potential dose reduction of a factor 3 to 7 (67%-86%). In spite of its longer reconstruction time and the fact that clinical studies are still required to complete these results, VEO clearly confirms the tremendous potential of iterative reconstructions for dose reduction in CT and appears to be an important tool for patient follow-up, especially for pediatric patients where cumulative lifetime dose still remains high.

Imaging of cervico-thoracic lymphangiomas in children

This study was undertaken to define the role of ultrasound (US) and magnetic resonance (MR) imaging in the diagnosis and preoperative staging of cervicothoracic lymphangiomas in children. In a retrospective study, 11 patients with surgically and pathologically proved lymphangiomas had MR imaging and 6 of them underwent simultaneous US. US showed superficial hypoechogenic multilocular cystic masses with septa of variable thickness, but failed to demonstrate retropharyngeal, axillary or mediastinal extensions in all patients. All lesions were identified on both MR T1-weighted images (T1WI) and T2-weighted images (T2WI). T2WI provided the best tissue contrast between the lymphangiomas and surrounding tissues. T1WI after i.v. injection of gadolinium DOTA (Gd DOTA) in two patients provided additional information regarding the extent of the lesion. The authors concluded that although lymphangiomas have a distinctive sonographic appearance, MR imaging allowed a better tissue characterisation and tumour exten. T2WI and T1WI after i.v. injection of Gd DOTA are especially helpful for the diagnosis and preoperative staging of cervico-thoracic lymphangiomas in children.

Extraosseous Langerhans Cell Histiocytosis in Children

Langerhans cell histiocytosis, a rare disease that occurs mainly in children, may produce a broad range of manifestations, from a single osseous lesion to multiple lesions involving more than one organ or system. The clinical course varies widely in relation to the patients age. Multisystem disease may demonstrate especially aggressive behavior in very young children, with the outcome depending largely on the stage of disease and the degree of related organ dysfunction at the time of diagnosis. Extraosseous manifestations are less commonly seen than osseous ones and may be more difficult to identify. To accurately detect extraosseous Langerhans cell histiocytosis at an early stage, radiologists must recognize the significance of individual clinical and laboratory findings as well as the relevance of imaging features for the differential diagnosis. The pattern and severity of pulmonary, thymic, hepatobiliary, splenic, gastrointestinal, neurologic, mucocutaneous, soft-tissue (head and neck), and salivary involvement in Langerhans cell histiocytosis generally are well depicted with conventional radiography, ultrasonography, computed tomography, and magnetic resonance imaging. However, the imaging features are not pathognomonic, and a biopsy usually is necessary to establish a definitive diagnosis.

Fetal MRI as complement to US in the diagnosis and characterization of anomalies of the genito-urinary tract

The purpose of this study is to compare the accuracy of prenatal ultrasound (US) and prenatal magnetic resonance imaging (MRI) in the diagnosis and characterization of congenital abnormalities of the genito-urinary tract and to determine if the additional information obtained by MRI may influence the management of the fetus. We retrospectively evaluate 15 cases of congenital genito-urinary tract anomalies detected by prenatal US and with echographic inconclusive diagnosis. We compare the MRI findings with the US findings and the final diagnosis, obtained from neonatal outcomes, imaging studies and pathology records. Fetal US diagnosis was correct in 9 cases (60%) and MRI in 13 cases (86.7%). Prenatal MRI revealed additional information to US in 9 cases (60%), which modified the initial US diagnosis in 5 cases (33.3%) and changed the therapeutic approach in 5 fetuses (33.3%). Fetal MRI was better than US in cases of oligoamnios and in fetuses with genito-urinary pathology concerning the pelvic and perineum region. We believe that MRI should be considered as a complementary diagnostic method in cases of echographic suspicion of congenital pathology of the genito-urinary tract and inconclusive prenatal US.

Extra-osseous involvement of Langerhans' cell histiocytosis in children

The predominant clinical and radiological features of Langerhans’ cell histiocytosis (LCH) in children are due to osseous involvement. Extra-osseous disease is far less common, occurring in association with bone disease or in isolation; nearly all anatomical sites may be affected and in very various combinations. The following article is based on a multicentre review of 31 children with extra-osseous LCH. The objective is to summarise the diverse possibilities of organ involvement. The radiological manifestations using different imaging modalities are rarely pathognomonic on their own. Nevertheless, familiarity with the imaging findings, especially in children with systemic disease, may be essential for early diagnosis.

Solid pseudopapillary tumor of the pancreas in children: typical radiological findings and pathological correlation

We report a case series of three children with solid pseudopapillary tumor of the pancreas (SPT) in which a complete radiological work-up, including ultrasound, computed tomography scans, and MRI, has been carried out. The aim of this article is to highlight the characteristic imaging findings of SPT in the pediatric age group and to establish a correlation with typical histopathological findings of the lesion.

Perfusion-weighted magnetic resonance imaging patterns of hypoxic-ischemic encephalopathy in term neonates.

To determine whether an early magnetic resonance imaging (MRI) study using perfusion‐weighted imaging (PWI) may define the pattern of brain injury in term neonatal hypoxic–ischemic (HI) encephalopathy.

Magnetic resonance detection of myelodysplasia in children with Currarino triad

Purpose. To evaluate the role of MRI in the detection of myelodysplasia in children with Currarino triad. Materials and methods. Six patients (two girls, four boys, aged 7 months–14 years, mean age 6 years) were studied with MRI, voiding cystourethrogram and barium enema or fistulography. CT and ultrasonography were also performed in two patients. Results. All patients presented with partial agenesis of the sacrum. Three patients suffered from an intermediate form of anorectal malformation (ARM) and three had a high form of ARM. The presacral masses consistent with Currarino triad included anterior meningocoele in three patients, lipoma in two patients and anterior lipomeningocoele in one patient. MRI diagnosed tethering of the spinal cord in four of six patients. The tethering of the spinal cord was due to a lipomeningocoele in one patient, an intradural lipoma in one patient and a lipoma of the filum in two patients. Conclusion. The association of Currarino triad with tethered spinal cord seems more common than generally reported in the literature. Preoperative MRI of the lumbosacral spine is essential to detect significant myelodysplasia in all patients with Currarino triad.

Prenatal diagnosis of congenital lung malformations

Prenatal diagnosis of congenital lung anomalies has increased in recent years as imaging methods have benefitted from technical improvements. The purpose of this pictorial essay is to illustrate typical imaging findings of a wide spectrum of congenital lung anomalies on prenatal US and MRI. Moreover, we propose an algorithm based on imaging findings to facilitate the differential diagnosis, and suggest a follow-up algorithm during pregnancy and in the immediate postnatal period.

Temporal evolution of MR perfusion in neonatal hypoxic-ischemic encephalopathy

To illustrate the evolution of brain perfusion‐weighted magnetic resonance imaging (PWI‐MRI) in severe neonatal hypoxic‐ischemic (HI) encephalopathy, and its possible relation to further neurodevelopmental outcome.