Technical analysis of volume-rendering algorithms: application in low-contrast structures using liver vascularisation as a model

AIM: To assess the influence of pre-set volume-rendering opacity curves (OC) on image quality and to identify which absolute parameters (density of aorta, hepatic parenchyma and portal vein) affect visualization of portal vascular structures (low-contrast structures). MATERIALS AND METHODS: Twenty-two patients underwent a dual-phase spiral CT with the following parameters: collimation 3 mm, pitch 2, increment 1 mm. Three scans were performed: one without contrast medium and the latter two after the injection of contrast material (conventionally identified as 'arterial' and 'portal'). The images were sent to a workstation running on an NT platform equipped with post-processing software allowing three-dimensional (3D) reconstructions to generate volume-rendered images of the vascular supply to the liver. Correlation between the absolute values of aorta, liver and portal vein density, OC parameters, and image quality were assessed. RESULTS: 3D images generated using pre-set OC obtained a much lower overall quality score than those produced with OC set by the operator. High contrast between the liver and the portal vein, for example during the portal vascular phase, allows wider windows, thus improving image quality. Conversely, the OC in the parenchymal phase scans must have a high gradient in order to better differentiate between the vascular structures and the surrounding hepatic parenchyma. CONCLUSIONS: Image features considered to be of interest by the operator cannot be simplified by the mean of pre-set OC. Due to their strong individual variability automatic 3D algorithms cannot be universally applied: they should be adapted to both image and patient characteristics.     

MR findings in lipoma arborescens of the knee: our experience

PURPOSE: This paper describes the role of MR imaging in the identification of the different macroscopic patterns of lipoma arborescens. MATERIALS AND METHODS: Between June 1995 and January 2004, a total of 6387 MR examinations of the knee were retrospectively assessed for the presence of lipoma arborescens. The MR examinations were performed using a superconductive 0.5 T MR unit with a transmitting/ receiving coil dedicated for the extremities. The MR images were acquired with SE T1-weighted, GE T2-weighted and STIR sequences in sagittal, coronal and axial planes with 3-mm thickness and 1-mm gap. RESULTS: Lipoma arborescens was identified in 9 patients (mean age: 36 years). In 2/9 cases a localized lipoma arborescens was detected as a well-marginated single nodule on the suprapatellar bursa without irregularity or synovial hyperplasia. In the remaining 7 cases diffuse lipoma arborescens was identified on the wall of the suprapatellar bursa. In one case of diffuse lipoma arborescens there was involvement of both knees. In all cases the MR findings were verified at surgery and the final diagnosis was made by histological examination. CONCLUSIONS: MR imaging shows a high accuracy in the identification and characterization of lipoma arborescens, due to its multiplanar capabilities and high contrast resolution. MRI allows correct evaluation of size and grade, accurate treatment planning and effective follow-up, avoiding the need for synovial biopsy.     

Benign focal liver lesions: spectrum of findings on SonoVue-enhanced pulse-inversion ultrasonography

The prevalence of benign focal liver lesions (BFLL) is high both in the general population and in patients with known malignancies. The gray-scale ultrasound (US) technique is usually the first-line imaging modality used in the radiological workup of such lesions, but unfortunately it lacks specificity. Furthermore, Doppler examination may often be unsatisfactory owing to motion artefacts, or when small or deeply located lesions are evaluated. Recently, microbubble-based contrast agents used in combination with gray-scale US techniques, which are very sensitive to nonlinear behavior of microbubbles, have led to a better depiction of both microvasculature and macrovasculature of focal hepatic masses, thus improving the reliability of using US in the assessment of liver tumors. This review illustrates the spectrum of enhancement patterns of BFLL on contrast-enhanced ultrasonography with SonoVue, a second-generation microbubble-based contrast agent.This paper is based on a work accepted for presentation as a scientific paper at the Scientific Assembly and Annual Meeting of the ECR 2004.     

Effect of fatty acids on arenavirus replication: inhibition of virus production by lauric acid

Summary.  To study the functional involvement of cellular membrane properties on arenavirus infection, saturated fatty acids of variable chain length (C10–C18) were evaluated for their inhibitory activity against the multiplication of Junin virus (JUNV). The most active inhibitor was lauric acid (C12), which reduced virus yields of several attenuated and pathogenic strains of JUNV in a dose dependent manner, without affecting cell viability. Fatty acids with shorter or longer chain length had a reduced or negligible anti-JUNV activity. Lauric acid did not inactivate virion infectivity neither interacted with the cell to induce a state refractory to virus infection. From mechanistic studies, it can be concluded that lauric acid inhibited a late maturation stage in the replicative cycle of JUNV. Viral protein synthesis was not affected by the compound, but the expression of glycoproteins in the plasma membrane was diminished. A direct correlation between the inhibition of JUNV production and the stimulation of triacylglycerol cell content was demonstrated, and both lauric-acid induced effects were dependent on the continued presence of the fatty acid. Thus, the decreased insertion of viral glycoproteins into the plasma membrane, apparently due to the increased incorporation of triacylglycerols, seems to cause an inhibition of JUNV maturation and release. Received August 2, 2000 accepted September 21, 2000     

Laparoscopic Right Hemicolectomy for Ileocolic Intussusception Secondary to Caecal Neoplasm

Intussusception in adults is a rare cause of abdominal pain. Unlike its paediatric counterpart, intussusception in adults is associated with obvious pathology. We describe a case of ileocolic intussusception extending to the splenic flexure. We were able to reduce the intussusception partially and pedicle was stapled carefully. The specimen was delivered through a small incision and right hemicolectomy was performed adhering to oncological principles. We recommend laparoscopic-assisted surgery is considered for adult intussusceptions.     

Influence of convolution filtering on coronary plaque attenuation values: observations in an ex vivo model of multislice computed tomography coronary angiography

Attenuation variability (measured in Hounsfield Units, HU) of human coronary plaques using multislice computed tomography (MSCT) was evaluated in an ex vivo model with increasing convolution kernels. MSCT was performed in seven ex vivo left coronary arteries sunk into oil followingthe instillation of saline (1/∞) and a 1/50 solution of contrast material (400 mgI/ml iomeprol). Scan parameters were: slices/collimation, 16/0.75 mm; rotation time, 375 ms. Four convolution kernels were used: b30f-smooth, b36f-medium smooth, b46f-medium and b60f-sharp. An experienced radiologist scored for the presence of plaques and measured the attenuation in lumen, calcified and noncalcified plaques and the surrounding oil. The results were compared by the ANOVA test and correlated with Pearson’s test. The signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated. The mean attenuation values were significantly different between the four filters (p < 0.0001) in each structure with both solutions. After clustering for the filter, all of the noncalcified plaque values (20.8 ± 39.1, 14.2 ± 35.8, 14.0 ± 32.0, 3.2 ± 32.4 HU with saline; 74.7 ± 66.6, 68.2 ± 63.3, 66.3 ± 66.5, 48.5 ± 60.0 HU in contrast solution) were significantly different, with the exception of the pair b36f–b46f, for which a moderate-high correlation was generally found. Improved SNRs and CNRs were achieved by b30f and b46f. The use of different convolution filters significantly modifief the attenuation values, while sharper filtering increased the calcified plaque attenuation and reduced the noncalcified plaque attenuation.     

Long-term experience with implanted intrathecal drug administration systems for failed back syndrome and chronic mechanical low back pain

Background  

Continuous intrathecal drug delivery has been shown in open studies to improve pain and quality of life in those with intractable back pain who have had spinal surgery. There is limited data on long term effects and and even less for patients with mechanical back pain without prior spinal surgery.     

PAQR3: a novel tumor suppressor gene

PAQR3, also known as RKTG (Raf kinase trapping to Golgi), is a member of the progestin and adipoQ receptor (PAQR) family. The role of PAQR3 as a tumor suppressor has recently been established in different types of human cancer in which PAQR3 exerts its biological function through negative regulation of the oncogenic Raf/MEK/ERK signaling. Multiple studies have found that PAQR3 downregulation frequently occurs in human cancers and is very often associated with tumor progression and shortened patients’ survival. Moreover, restoring the expression of PAQR3 could induce apoptosis and inhibit proliferation and invasiveness of cancer cells. Downregulation of PAQR3 by oncogenic microRNAs has also been reported. In this review, we summarized current knowledge concerning the role of PAQR3 in tumor development. To our knowledge, this is the first review on the role of this novel tumor suppressor.     

Loco-regional treatment of hepatocellular carcinoma: Role of contrast-enhanced ultrasonography

Hepatocellular carcinoma (HCC) is one of the few cancers for which locoregional treatments (LRTs) are included in international guidelines and are considered as a valid alternative to conventional surgery. According to Barcelona Clinic Liver Cancer classification, percutaneous treatments such as percutaneous ethanol injection, radiofrequency ablation and microwave ablation are the therapy of choice among curative treatments in patients categorized as very early and early stage, while transcatheter arterial chemoembolization is considered the better option for intermediate stage HCC. A precise assessment of treatment efficacy and surveillance is essential to optimize survival rate, whereas residual tumor requires additional treatment. Imaging modalities play a key role in this task. Currently, contrast-enhanced computed tomography/magnetic resonance imaging are considered the standard imaging modalities for this purpose. Contrast enhanced ultrasound (CEUS), using second generation contrast agents, plays an increasingly important role in detecting residual disease after LRTs. CEUS is a straightforward to perform, repeatable and cost-effective imaging modality for patients with renal failure or iodine allergies. Due to the ability to focus on single regions, CEUS can also provide high temporal resolution. Moreover, several studies have reported the same or better diagnostic accuracy as contrast-enhanced computed tomography for assessing tumor vascularity 1 mo after LRTs, and recently three-dimensional (3D)-CEUS has been reported as a promising technique to improve the evaluation of tumor response to therapy. Furthermore, CEUS could be used early after procedures in monitoring HCC treatments, but nowadays this indication is still debated, and data from literature are conflicting, especially after transcatheter arterial chemoembolization procedure.     

Risk factors for development of primary cancer in the gastric stump. Intragastric nitrites and nitroso-compounds after surgery for duodenal ulcer

Results are reported from a study on the presence and concentration of nitrites and nitroso-compounds in the gastric juice of 53 patients operated on for duodenal ulcer and in 15 controls. The investigations were made after various postoperative intervals. In the patients who had undergone Billroth II operation, the concentrations of nitrites and of nitroso-compounds were higher than in those with Billroth I operation and in the controls. It is concluded that patients with Billroth II operation may be particularly susceptible to subsequent primary neoplasm of the gastric stump, as a result of the carcinogenic action of these substances.