Vanishing Bone Metastases in Superior Vena Cava Obstruction.

Teaching Point: Intravertebral venous collateral formation can occur in thoracic venous obstruction syndrome and mimic metastatic bone lesions on contrast-enhanced imaging: vanishing bone metastases.

MRI in Early Onset of Creutzfeldt Jakob Disease.

Teaching point: Cortical diffusion restriction can be depicted by MRI in the early onset of Creutzfeld Jakob disease.

Nodular sclerosing Hodgkin's disease mimicking Riedel's invasive fibrous thyroiditis.

Riedel's thyroiditis appears in the form of a hard cervical mass with rapid onset, and it is associated with extensive fibrosis that compresses nearby structures, such as the trachea and supra-aortic vessels; its diagnosis is essentially histopathological. Although its histological characteristics have been well established, there are some diagnostic pitfalls. We report here the case of a 37-year-old woman, with clinical and histopathological data suggesting Riedel's disease. Fibrosis regressed after treatment with corticosteroids, relieving the compressed airways. However, in contrast with the latest knowledge on this disease, the IgG4 serum levels were consistently normal, and positron emission tomography in search of extensive fibrosis revealed an abnormal metabolic activity of the bone marrow. The final diagnosis revised by the histopathologist was that of nodular sclerosing Hodgkin's lymphoma. This case allows us to review the diagnostic approach when facing a thyroid mass with extremely rapid evolution.

Peripheral pulmonary arteries: identification at multi-slice spiral CT with 3D reconstruction.

Our objective was to analyze the peripheral pulmonary arteries using thin-collimation multi-slice spiral CT. Twenty consecutive patients underwent enhanced-spiral multi-slice CT using 1-mm collimation. Two observers analyzed the pulmonary arteries by consensus on a workstation. Each artery was identified on axial and 3D shaded-surface display reconstruction images. Each subsegmental artery was measured at a mediastinal window setting and compared with anatomical classifications. The location and branching of every subsegmental artery was recorded. The number of well-visualized sub-subsegmental arteries at a mediastinal window setting was compared with those visualized at a lung window setting. Of 800 subsegmental arteries, 769 (96%) were correctly visualized and 123 accessory subsegmental arteries were identified using the mediastinal window setting. One thousand ninety-two of 2019 sub-subsegmental arteries (54%) identified using the lung window setting were correctly visualized using the mediastinal window setting. Enhanced multi-slice spiral CT with thin collimation can be used to analyze precisely the subsegmental pulmonary arteries and may identify even more distal pulmonary arteries.

Dynamic computed tomography with low- and high-molecular-mass contrast agents to assess microvascular permeability modifications in a model of liver fibrosis.

Interstitial collagen formation and transformation of the fenestrated hepatic sinusoids into continuous capillaries are major ultrastructural changes that occur in liver cirrhosis and fibrosis. These modifications lead to progressive restriction of blood-liver exchanges. The purpose of our study was to evaluate the permeability changes in a model of hepatic fibrosis by using dynamic computed tomography (CT) enhanced with contrast agents of different molecular masses. Dynamic single-section CT of the liver was performed after intravenous bolus administration of a low-molecular-mass contrast agent (iobitridol) and an experimental high-molecular-mass agent (P840) in normal control rabbits and in rabbits with hepatic fibrosis. Hepatic, aortic and portal venous time-density curves were fitted with a dual-input one-compartmental model to calculate the hepatic mean transit time and distribution volume of the contrast agents. In the rabbits with liver fibrosis, the mean transit time of the high-molecular-mass agent was shorter than that of the low-molecular-mass agent (10.0+/-1.8 s and 12.0+/-1.2 s respectively; P<0.05). The distribution volume accessible to the high-molecular-mass agent was also smaller (22.2+/-4.8% compared with 32.0+/-6.7%; P<0.01). In the normal rabbits, the mean transit times of the high- and low-molecular-mass agents did not differ significantly, and nor did their distribution volumes. Our results demonstrate decreased sinusoidal permeability for the high-molecular-mass agent P840 in a model of hepatic fibrosis. Non-invasive assessment of permeability changes in liver fibrosis can be performed with dynamic CT and contrast agents of different molecular masses.