Assessment of organ dose and image quality in head and chest CT examinations: a phantom study.

The purpose of this study is to assess dose for radiosensitive organs and image quality in head and chest computed tomography (CT) examinations. Our focus was in the brain, eye lens and lung organs using two protocols; one protocol with fixed mAs and filtered back projection (FBP) and another with tube current modulation (TCM) and sinogram affirmed iterative reconstruction (SAFIRE). Measurements were performed on a 128-slice CT scanner by placing thermoluminescent dosimeters (TLDs) in an anthropomorphic adult phantom. Results were compared to a CT-Expo software. Objective image quality was assessed in terms of signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR). SPSS software was used for data analyses. Results showed that, using TCM, doses were reduced by 22.84%-25.06% for brain, by 21.82%-23.48% for eye lens and by 54%-53.22% for lung with TLD and CT-Expo respectively. The increased SNR and CNR values achieved for scans performed with TCM combined with iterative reconstruction techniques were 38.68%-58.81% and 38.91%-43.60% respectively. We conclude that, using TCM, a significant mean organ dose reduction is achieved for brain, eye lens and lung organs. Then, combined with iterative reconstruction, image quality was well maintained in terms of SNR and CNR. Thus it is highly recommended in clinical practice optimization in head and chest CT examinations.

Dedifferentiated adamantinoma associated with fibrous dysplasia.

A 21-year-old patient presented with an aggressive lesion of the left tibia associated to lymph nodes and lung metastasis. Histological examination revealed a high grade spindle cell sarcoma involving some areas of cytokeratine positive cells. Ultrastructural examination showed the presence of epithelial features in the sarcomatoid cells. The diagnosis of dedifferentiated spindle-celled adamantinoma was established. A second lesion of the right tibia was diagnosed as fibrous dysplasia. The patient had a leg amputation. He died 2 years later with multiple lung and bone metastases. The diagnosis of dedifferentiated adamantinoma should be considered when a clinician is confronted with a tibial biopsy of a "keratin-positive sarcoma". The association with fibrous dysplasia in this case is discussed.

Bizarre Parosteal Osteochondromatous Proliferation: Nora's Lesion.

The purpose of this study was to review the imaging and anatomopathologic findings and to discuss the main differential diagnosis of bizarre parosteal osteochondromatous proliferation (BPOP) or Nora's lesion, a rare benign surface lesion of the bone. Histologically confirmed plain radiographs, ultrasound, CT and MRI images of four patients with BPOP were obtained and retrospectively reviewed. Three cases involving the hand and one involving the foot are reported. On plain radiographs, BPOP is a wellmarginated, calcified or ossified mass arising directly from the cortical surface of the underlying bone. Ultrasound images show a low echoic peripheral cap around the lesion. CT images show the wide base of the lesion. On MRI, BPOP was of a low signal on T1, enhancing following gadolinium administration. Underlying bone and adjacent surrounding soft tissues were normal.

[Cervicobrachial neuralgia revealing neurosarcoma]. / Névralgie cervicobrachiale révélatrice d'un neurofibrosarcome (MPNST) cervical.

Malignant peripheral nerve sheath tumor (MPNST) or neurofibrosarcoma, previously described as malignant Schwannoma or neurosarcoma, is an extremely rare cause of malignancy localized in the neck. Half of reported cases occurred in patients with neurofibromatosis in Von Recklinghausen disease type I. Typical features include high grade malignancy and a tendency to recurrence and distant metastases. We report the case of a 56-year-old woman with neurosarcoma of the neck, which was revealed by a cervicobrachial neuralgia. The physical examination found a mass on the left side of the neck. Plain radiographs showed osteoarthritis. MRI showed a well-defined paravertebral mass. Pathologic diagnosis was neurosarcoma. Radiotherapy was delivered.

[Aneurysmal bone cyst of the ethmoid bone]. / Kyste osseux anévrismal de l'ethmoïde.

Aneurysmal bone cysts is a benign, slow growing expansile lesion usually found in long bones or vertebrae. Only 5 cases of ABC of the ethmoid bone have been reported in the literature. Plain radiographs are not specific. CT and MRI are very useful to depict the extent of the lesion and demonstrate the presence of blood-fluid levels, which is a characteristic finding of ABC. We present one atypical case of ABC of the ethmoid bone in a 15-year-old female characterised by its extensive involvement and its rare location.

[Splenic nodules and sickle cell anemia]. / Nodules spléniques et drépanocytose.

OBJECTIVE: We report 4 patients with sickle cell anemia presenting with intra-splenic benign nodules corresponding to islands of preserved tissue within splenic ferro-calcinosis. MATERIAL AND METHODS: Ultrasound, CT and MRI findings were evaluated and compared to a follow-up study by ultrasound and CT done after 6 to 12 months. RESULTS: Ultrasound showed multiple well-defined rounded nodules appearing hypoechoic compared to the rest of the spleen that was hyperechoic. On CT, the nodules were homogenous, hypodense relative to the spleen, isodense to the liver in 3 cases and hypodense to the liver in 1 case. On MRI, the nodules appeared relatively hyperintense within low-signal-intensity spleens. The ultrasound and CT follow-up study demonstrated no remarkable change. CONCLUSION: In sickle cell patients, intra-splenic benign nodules corresponding to normal splenic tissue may be identified on imaging studies. The differential diagnosis is discussed.

[Non-vascular retroperitoneal emergencies]. / Urgences rétropéritonéales non vasculaires.

Acute renal disease, in the absence of trauma, consist of acute renal obstruction, renal infection or a combination of the two. The diagnosis of acute renal colic is usually performed with ultrasound or excretory urography whereas parenchymal involvement in renal infection is best demonstrated on computed tomography images. The aim of radiologic investigations is to look for complications in order to guide the treatment, particularly percutaneous procedures. Other less common acute renal diseases include renal vein thrombosis optimally analyzed with contrast injection to demonstrate renal function, and spontaneous renal hemorrhage, which implies careful renal assessment looking for a small tumor. Acute psoas compartment diseases include hematomas and abscesses. Computed tomography is the best diagnostic tool and the examination of choice for the follow-up lesions and to guide percutaneous drainage.

[Retroperitoneal vascular emergencies]. / Urgences rétropéritonéales vasculaires.

Ruptured abdominal aortic aneurysm is the major surgical emergency in the retroperitoneal compartment. Rupture of an abdominal aortic aneurysm is always fatal without urgent operative repair. Computed tomography is the reference standard for the diagnosis of ruptured abdominal aortic aneurysm in hemodynamically stable patients. At CT, the diagnosis is based on the combination of abdominal aortic aneurysm and extraluminal retroperitoneal blood. Retroperitoneal hemorrhage usually demonstrates both isodense and hyperdense areas. In most cases hemorrhage is located in psoas compartments and perirenal space. In the case of ruptured abdominal aortic aneurysm other findings may be demonstrated such as focal interruption of the aortic wall and active extravasation of contrast media in the retroperitoneal compartments. Inflammatory abdominal aortic aneurysm, that may present as acute abdominal pain, should be recognized and differentiated from ruptured abdominal aortic aneurysm. Inflammatory abdominal aortic aneurysm is characterized by a fibrotic process around the abdominal aorta that may entrap adjacent structures such as ureters, duodenum and inferior vena cava. Aortic dissection, mycotic aneurysm, and inferior vena cava thrombosis are less common. Complications occurring after emergency aneurysm replacement are also considered.

[Intraperitoneal vascular emergencies]. / Urgences vasculaires intrapéritonéales.

Intraperitoneal vascular lesions constitute severe causes of acute abdomen. These disorders include ischemia and infarction of colon and small bowel and abdominal hemorrhage. In case of intestinal ischemia, the radiologic procedures are performed in order to establish the diagnostic, identify the site of ischemia, and detect the etiology of ischemia. Plain radiography of the abdomen, ultrasonography, CT scan and angiography may be performed. In case of intestinal hemorrhage, angiography may be performed when endoscopy fails to establish the diagnosis. Embolization can be performed in selected cases.

[Acute pancreatitis]. / Pancréatite aiguë.

The diagnosis of acute pancreatitis is based on clinical examination and basic laboratory tests. The main role of sonography in acute pancreatitis is to evaluate gallstones and small fluid collections. However, sonography is frequently difficult due to intestinal ileus related to pancreatitis. CT is indicated early in the clinical course of acute severe pancreatitis when the diagnosis is uncertain or when complications such as abscess, hemorrhage, or necrosis, are suspected. In addition, CT may be used to assess the prognosis and follow-up of patients.

[Abdominal injuries]. / Traumatismes de l'abdomen.

Radiologic evaluation of abdominal trauma must provide a quick and accurate assessment of the lesions in order to improve the management of the patient. The technique used varies depending on the mechanism of the trauma (blunt trauma or stab wounds) and the hemodynamic status. Radiologic evaluation is usually performed in blunt trauma whereas stab wound trauma is usually explored surgically. The various techniques available are standard radiographs, ultrasonography, computed tomography and arteriography. The role of magnetic resonance imaging in the immediate evaluation is still not well defined. It appears to be a useful method in the delayed evaluation of diaphragmatic trauma. Computed tomography is the method most commonly performed in trauma patients. This technique is accurate and allows correct assessment of the lesions. The disadvantages are the radiation induced and the need for a hemodynamically stable patient. The aim of the radiologic evaluation is to provide the clinicians with an accurate description of the lesions. It can help in the management of the patient usually in association with clinical and laboratory data. It can also guide interventional procedures (drainage, embolization...). Finally, it allows radiographic follow-up when conservative treatment is performed.

[Septic thrombosis of the cavernous sinus complicating malignant staphylococcal infection of the face]. / La thrombose septique des sinus caverneux compliquant la staphylococcie maligne de la face.

Septic thrombosis of the cavernous sinuses most commonly follows staphylococcal infections of the middle third of the face. Orbital symptoms are constant. We report six cases diagnosed only by CT. At present, MR imaging is the diagnostic procedure of choice. Its findings are thought to reflect the septic nature of the thrombosis.

[A rare cause of multiple lacunae of the cranial vault and temporal bone in adults: histiocytosis X]. / Une cause rare de lacunes multiples de la voûte et de l'os temporal chez l'adulte: l'histiocytose X.

Histiocytosis X is an uncommon disease. Temporal bone involvement is a frequent head and neck manifestation. Most patients are under fifteen years of age. The authors report a case of a bilateral extensive temporal involvement complicated with vertigo and peripheric facial palsy. CT plays a dominant role in the diagnosis because of the ability to identify bone destruction, soft tissue involvement and intra-cranial histiocytosis more accurately.

[Mondini's malformation. Apropos of a case]. / La malformation de Mondini. A propos d'un cas.

Mondini's malformation is a rare internal ear malformation. It's often discovered in childhood in the course of perception deafness check up, or repetitive meningitis in some other cases. The authors report a case of complex Mondini's malformation with fistulas of cerebro-spinal-fluid in oval and round windows, and stress the interest of high resolution computed tomography.

[Extramedullary hematopoiesis: multiple mediastinal localizations]. / Hématopoïèse extra-médullaire: localisations médiastinales multiples.

Intrathoracic extra-medullary hematopoiesis is a compensatory mechanism usually seen in thalassemia. The authors report a case with multiple mediastinal localisations fortuitously discovered. CT has allowed diagnosis and led percutaneous biopsy.