Pour ne rien manquer sur le ct d’un patient polytraumatisé

Hôpitaux Universitaires de GenèveLa difficulté de l’interprétation du CT chez un patient polytraumatisé réside dans le fait que le radiologue est confronté à un grand nombre d’images, qu’il doit analyser dans un temps limité et des conditions difficiles. L’analyse initiale de l’examen est primordiale car l’attitude thérapeutique découle directement des premiers diagnostics radiologiques; toute une modification secondaire d’un résultat provisoire est ensuite difficile à corriger. Ceci impose une stratégie d’analyse efficace. Chez les patients sévèrement polytraumatisés, il est illusoire de vouloir établir immédiatement une liste exhaustive et détaillée de l’ensemble des lésions observables sur le CT. Il est donc nécessaire de procéder, dans un premier temps (lorsque le patient est encore sur la table d’examen), à une analyse systématique et ciblée de l’examen CT, afin de ne pas manquer des lésions vitales et de réaliser, si nécessaire, des coupes CT supplémentaires. Pour ne pas commettre d’erreur d’interprétation ou de méconnaitre une lésion importante pour la prise en charge immédiate du patient au CT, il convient de connaître les pièges diagnostics On peut diviser les erreurs diagnostiques en deux classes: les erreurs d’interprétation (banalisation d’une observation scanographique importante qui a été détectée par le radiologue) et les erreurs de perception (non-détection d’un élément présent sur le CT). Les erreurs d’interprétation sont liées à la mutiplicité des étiologies pouvant réaliser une image similaire. Les erreurs de perception proviennent de la petite taille et du contraste insuffisant des lésions. Pour chaque étage anatomique, nous allons passer en revue les pathologies le plus souvent associées à des erreurs d’interprétation et de perception lors de la phase initiale d’interprétation du CT d’un patient polytraumatisé

Imagerie des traumatismes du rachis

Hôpitaux Universitaires de GenèveLes lésions du rachis cervical représentent plus de la moitié de toutes les admissions en traumatologie vertébrale dans un centre d’urgence. Chez un patient qui a subi un traumatisme cervical mineur, il est important d’effectuer un examen clinique soigneux avant de demander une imagerie. Les patients qui répondent aux cinq critères NEXUS ne nécessitent pas d’imagerie. Les 3 vues classiques en radiologie standard (face, profil, transbuccale) sont souvent les premiers examens effectués chez un patient qui ne répond pas à tous les critères NEXUS. Avec une sensibilité de 60 à 80%, une radiographie cervicale normale n’est pas suffisante pour écarter absolument une fracture cervicale. La radiographie conventionnelle est généralement effectuée dans une position verticale et donne des informations utiles sur la statique, informations qui ne peuvent pas être obtenues par un scanner qui est réalisé en position couchée. La radiographie conventionnelle peut donc être utilisé comme un complément au CT. Les signes radiologiques standards seront abordés dans la présentation. Une IRM est réalisée comme un complément au CT en cas de déficit neurologique. Les fractures vertébrales thoraciques sont moins fréquentes que les fractures lombaires, et sont généralement associées à un traumatisme à haute énergie. La radiographie d’admission montre souvent des signes typiques d’ hémomediastin, également évocateurs d’une rupture aortique. De nombreuses classifications ont été proposées pour caractériser les fractures thoraco-lombaires, pour évaluer la stabilité et déterminer le traitement le plus approprié. Un des plus célèbres est la classification Denis, qui a divisé la colonne vertébrale TL en trois colonnes. Dans ce système, une fracture est instable lorsque la colonne médiane est rompue. Aujourd’hui, les nouvelles classifications (AO-Magerl, TLICS) ne considèrent que deux colonnes. La stabilité est principalement déterminée par l’intégrité de la colonne postérieure (éléments en arrière du corps vertébral). Nous verrons des exemples de fractures et de stabilité. Lorsque la paroi postérieure du corps vertébral n’est pas atteinte, aucun traitement spécifique n’est généralement nécessaire, sauf dans certains cas rares («split fracture»). Lorsque la paroi postérieure du corps vertébral est atteinte, sans fracture de la colonne postérieure, le fragment en saillie dans le canal rachidien peut être le plus souvent réduit par traction sur le ligament longitudinal postérieur (ligamentotaxis postérieure). Lorsque la fracture implique la colonne postérieure, elle est instable et nécessite une intervention chirurgicale. Quand il n’ya pas de rotation des fragments, cette lésion est dite de type B (classification AO). La fracture de Chance appartient à cette catégorie. Cette fracture est instable, mais la plupart des patients n’ont pas de déficit neurologique au moment de l’admission. Les fractures de Chance sont généralement subtiles et peuvent facilement être manquées sur les images axiales. Il est important d’effectuer des reconstructions MPR. L’atteinte de la colonne postérieure, associée à une rotation des fragments est considérée comme fracture de type C (classification AO)

Undiagnosed Myocardial Tear Blocked byan Omental Plug: Potentially LifethreateningCondition

Blunt chest trauma carries a high mortality when associated with cardiac rupture. Rapid diagnosis represents a true challenge for clinicians, with CT scan examination playing a central role. We report a case of a traumatic myocardial tear, plugged by the greater omentum through a diaphragmatic rent in an hemodynamically stable patient. This condition, identified during laparoscopy, was not suspected preoperatively at both clinical examination and CT. This case illustrates that a transparietal cardiac rupture can be sealed off by surrounding structures. This phenomenon explains why CT can be unable to detect traumatic cardiac rupture, with the potential risk of a delayed fatal bleeding. This case also emphasizes the risk of using laparoscopy in traumatic diaphragm rupture repai

Contrast enhanced ultrasonography versus MR angiography in aortocaval fistula: case report

Aortocaval fistula (ACF) is a rare, life threatening complication of abdominal aortic aneurysms. Time to diagnosis is crucial as preoperative diagnosis and early surgical intervention significantly improve the outcome. The clinical spectrum being varied, the challenge of prompt and reliable diagnosis rests on emergency radiology. While the gold standard for detecting ACF today is CT angiography (CTA), frequently complicating renal insufficiency discourages the use of iodinated contrast making MR angiography (MRA) a useful alternative. Contrast enhanced ultrasound (CEUS) provides a promising new diagnostic option allowing rapid, non invasive and bedside diagnosis, especially in hemodynamically unstable patients. We present a case of prompt diagnosis of ACF by CEUS in comparison to modern MRA, thus establishing the new potential role of CEU

Impact of the introduction of 16-row MDCT on image quality and patient dose: phantom study and multi-centre survey

The purpose was to compare the image quality and patient dose between 4- and 16-row MDCT units and to evaluate the dispersion of the dose delivered for common clinical examinations. Four 4- and 16-row MDCT units were used in the study. Image noise levels from images of a CatPhan phantom were compared for all units using a given CTDIvol of 15.0±1.0mGy. Standard acquisition protocols from ten centres, shifted from 4- to 16-row MDCT (plus one additional centre for 16-row MDCT), were compared for cerebral angiography and standard chest and abdomen examinations. In addition, the protocols used with 16-row MDCT units for diagnosis of the unstable shoulder and for cardiac examinations were also compared. The introduction of 16-MSCT units did not reduce the performance of the detectors. Concerning the acquisition protocols, a wide range in practice was observed for standard examinations; DLP varied from 800 to 5,120mGy.cm, 130 to 860mGy.cm, 410 to 1,790mGy.cm and 850 to 2,500mGy.cm for cerebral angiography, standard chest, standard abdomen and heart examinations, respectively.The introduction of 16-row MDCT did not, on average, increase the patient dose for standard chest and abdominal examinations. However, a significant dose increase has been observed for cerebral angiography. There is a wide dispersion in the doses delivered, especially for cardiac imagin

Case-based lung image categorization and retrieval for interstitial lung diseases: clinical workflows

Purpose: Clinical workflows and user interfaces of image-based computer-aided diagnosis (CAD) for interstitial lung diseases in high-resolution computed tomography are introduced and discussed. Methods: Three use cases are implemented to assist students, radiologists, and physicians in the diagnosis workup of interstitial lung diseases. Results: In a first step, the proposed system shows a three-dimensional map of categorized lung tissue patterns with quantification of the diseases based on texture analysis of the lung parenchyma. Then, based on the proportions of abnormal and normal lung tissue as well as clinical data of the patients, retrieval of similar cases is enabled using a multimodal distance aggregating content-based image retrieval (CBIR) and text-based information search. The global system leads to a hybrid detection-CBIR-based CAD, where detection-based and CBIR-based CAD show to be complementary both on the user's side and on the algorithmic side. Conclusions: The proposed approach is in accordance with the classical workflow of clinicians searching for similar cases in textbooks and personal collections. The developed system enables objective and customizable inter-case similarity assessment, and the performance measures obtained with a leave-one-patient-out cross-validation (LOPO CV) are representative of a clinical usage of the syste

Evaluation of a low-dose CT protocol with oral contrast for assessment of acute appendicitis

The aim of this study was to evaluate a low-dose CT with oral contrast medium (LDCT) for the diagnosis of acute appendicitis and compare its performance with standard-dose i.v. contrast-enhanced CT (standard CT) according to patients' BMIs. Eighty-six consecutive patients admitted with suspicion of acute appendicitis underwent LDCT (30mAs), followed by standard CT (180mAs). Both examinations were reviewed by two experienced radiologists for direct and indirect signs of appendicitis. Clinical and surgical follow-up was considered as the reference standard. Appendicitis was confirmed by surgery in 37 (43%) of the 86 patients. Twenty-nine (34%) patients eventually had an alternative discharge diagnosis to explain their abdominal pain. Clinical and biological follow-up was uneventful in 20 (23%) patients. LDCT and standard CT had the same sensitivity (100%, 33/33) and specificity (98%, 45/46) to diagnose appendicitis in patients with a body mass index (BMI) ≥ 18.5. In slim patients (BMI < 18.5), sensitivity to diagnose appendicitis was 50% (2/4) for LDCT and 100% (4/4) for standard CT, while specificity was identical for both techniques (67%, 2/3). LDCT may play a role in the diagnostic workup of patients with a BMI ≥ 18.

Comparative Performance Analysis of State-of-the-Art Classification Algorithms Applied to Lung Tissue Categorization

In this paper, we compare five common classifier families in their ability to categorize six lung tissue patterns in high-resolution computed tomography (HRCT) images of patients affected with interstitial lung diseases (ILD) and with healthy tissue. The evaluated classifiers are naive Bayes, k-nearest neighbor, J48 decision trees, multilayer perceptron, and support vector machines (SVM). The dataset used contains 843 regions of interest (ROI) of healthy and five pathologic lung tissue patterns identified by two radiologists at the University Hospitals of Geneva. Correlation of the feature space composed of 39 texture attributes is studied. A grid search for optimal parameters is carried out for each classifier family. Two complementary metrics are used to characterize the performances of classification. These are based on McNemar's statistical tests and global accuracy. SVM reached best values for each metric and allowed a mean correct prediction rate of 88.3% with high class-specific precision on testing sets of 423 ROI

Occult fractures of the scaphoid: the role of ultrasonography in the emergency department

Objective: To evaluate ultrasonography (US) performed by an emergency radiologist in patients with clinical suspicion of scaphoid fracture and normal radiographs. Materials and methods: Sixty-two consecutive adult patients admitted to our emergency department with clinical suspicion of scaphoid fracture and normal radiographs underwent US examination of the scaphoid prior to wrist computed tomography (CT), within 3days following wrist trauma. US examination was performed by a board-certified emergency radiologist, non-specialized in musculoskeletal imaging, using the linear probe (5-13MHz) of the standard sonographic equipment of the emergency department. The radiologist evaluate for the presence of a cortical interruption of the scaphoid along with a radio-carpal or scapho-trapezium-trapezoid effusion. A CT of the wrist (reference standard) was performed in every patient, immediately after ultrasonography. Fractures were classified into two groups according to their potential for complication: group 1 (high potential, proximal or waist), group 2 (low-potential, distal or tubercle). Results: A scaphoid fracture was demonstrated by CT in 13 (21%) patients: eight (62%) of them belonged to group 1 (three in the proximal pole, five in the waist), five (38%) to group 2 (three in the distal part, two in the tubercle). US was 92% sensitive (12/13) in demonstrating a scaphoid fracture. It was 100% sensitive (8/8) in demonstrating a fracture with a high potential of complication (group 1). Conclusions: Our data show that, in emergency settings, US can be used for the triage to CT in patients with clinical suspicion of scaphoid fracture and normal radiograph