Current Issue : January - March Volume : 2015 Issue Number : 1 Articles : 6 Articles
Background: A bone scan is a common method for monitoring bone metastases in patients with advanced prostate\ncancer. The Bone Scan Index (BSI) measures the tumor burden on the skeleton, expressed as a percentage of the total\nskeletal mass. Previous studies have shown that BSI is associated with survival of prostate cancer patients. The\nobjective in this study was to investigate to what extent regional BSI measurements, as obtained by an automated\nmethod, can improve the survival analysis for advanced prostate cancer.\nMethods: The automated method for analyzing bone scan images computed BSI values for twelve skeletal regions,\nin a study population consisting of 1013 patients diagnosed with prostate cancer. In the survival analysis we used the\nstandard Cox proportional hazards model and a more advanced non-linear method based on artificial neural\nnetworks. The concordance index (C-index) was used to measure the performance of the models.\nResults: A Cox model with age and total BSI obtained a C-index of 70.4%. The best Cox model with regional\nmeasurements from Costae, Pelvis, Scapula and the Spine, together with age, got a similar C-index (70.5%). The overall\nbest single skeletal localisation, as measured by the C-index, was Costae. The non-linear model performed equally well\nas the Cox model, ruling out any significant non-linear interactions among the regional BSI measurements.\nConclusion: The present study showed that the localisation of bone metastases obtained from the bone scans in\nprostate cancer patients does not improve the performance of the survival models compared to models using the\ntotal BSI. However a ranking procedure indicated that some regions are more important than others....
Background: Determination of regional lung air volume has several clinical applications. This study investigates the\nuse of mid-tidal breathing CT scans to provide regional lung volume data.\nMethods: Low resolution CT scans of the thorax were obtained during tidal breathing in 11 healthy control male\nsubjects, each on two separate occasions. A 3D map of air volume was derived, and total lung volume calculated.\nThe regional distribution of air volume from centre to periphery of the lung was analysed using a radial transform\nand also using one dimensional profiles in three orthogonal directions.\nResults: The total air volumes for the right and left lungs were 1035 +/? 280 ml and 864 +/? 315 ml, respectively\n(mean and SD). The corresponding fractional air volume concentrations (FAVC) were 0.680 +/? 0.044 and\n0.658 +/? 0.062. All differences between the right and left lung were highly significant (p < 0.0001). The coefficients\nof variation of repeated measurement of right and left lung air volumes and FAVC were 6.5% and 6.9% and 2.5%\nand 3.6%, respectively. FAVC correlated significantly with lung space volume (r = 0.78) (p < 0.005). FAVC increased\nfrom the centre towards the periphery of the lung. Central to peripheral ratios were significantly higher for the\nright (0.100 +/? 0.007 SD) than the left (0.089 +/? 0.013 SD) (p < 0.0001).\nConclusion: A technique for measuring the distribution of air volume in the lung at mid-tidal breathing is described.\nMean values and reproducibility are described for healthy male control subjects. Fractional air volume concentration is\nshown to increase with lung size....
Background: Diffusion-weighted MRI (DWI) has been used in neurosurgical practice mainly to distinguish cerebral\nmetastases from abscess and glioma. There is evidence from other solid organ cancers and metastases that DWI\nmay be used as a biomarker of prognosis and treatment response. We therefore investigated DWI characteristics of\ncerebral metastases and their peritumoral region recorded pre-operatively and related these to patient outcomes.\nMethods: Retrospective analysis of 76 cases operated upon at a single institution with DWI performed pre-operatively\nat 1.5T. Maps of apparent diffusion coefficient (ADC) were generated using standard protocols. Readings were taken\nfrom the tumor, peritumoral region and across the brain-tumor interface. Patient outcomes were overall survival and\ntime to local recurrence.\nResults: A minimum ADC greater than 919.4 Ã?â?? 10-6 mm2/s within a metastasis predicted longer overall survival\nregardless of adjuvant therapies. This was not simply due to differences between the types of primary cancer\nbecause the effect was observed even in a subgroup of 36 patients with the same primary, non-small cell\nlung cancer. The change in diffusion across the tumor border and into peritumoral brain was measured by the\nââ?¬Å?ADC transition coefficientââ?¬Â or ATC and this was more strongly predictive than ADC readings alone. Metastases with a\nsharp change in diffusion across their border (ATC >0.279) showed shorter overall survival compared to those\nwith a more diffuse edge. The ATC was the only imaging measurement which independently predicted overall survival\nin multivariate analysis (hazard ratio 0.54, 95% CI 0.3 ââ?¬â?? 0.97, p = 0.04).\nConclusions: DWI demonstrates changes in the tumor, across the tumor edge and in the peritumoral region which\nmay not be visible on conventional MRI and this may be useful in predicting patient outcomes for operated cerebral\nmetastases....
Background: Endobronchial ultrasonography (EBUS) has been applied as a routine procedure for the diagnostic\nof hiliar and mediastinal nodes. The authors assessed the relationship between the echographic appearance of\nmediastinal nodes, based on endobronchial ultrasound images, and the likelihood of malignancy.\nMethods: The images of twelve malignant and eleven benign nodes were evaluated. A previous processing\nmethod was applied to improve the quality of the images and to enhance the details. Texture and morphology\nparameters analyzed were: the image texture of the echographies and a fractal dimension that expressed the\nrelationship between area and perimeter of the structures that appear in the image, and characterizes the\nconvoluted inner structure of the hiliar and mediastinal nodes.\nResults: Processed images showed that relationship between log perimeter and log area of hilar nodes was lineal\n(i.e. perimeter vs. area follow a power law). Fractal dimension was lower in the malignant nodes compared with\nnon-malignant nodes (1.47(0.09), 1.53(0.10) mean(SD), Mannââ?¬â??Whitney U test p < 0.05)).\nConclusion: Fractal dimension of ultrasonographic images of mediastinal nodes obtained through endobronchial\nultrasound differ in malignant nodes from non-malignant. This parameter could differentiate malignat and\nnon-malignat mediastinic and hiliar nodes....
Background: CT perfusion images have a high contrast ratio between voxels representing different anatomy, such\nas tissue or vessels, which makes image segmentation of tissue and vascular regions relatively easy. However, grey\nand white matter tissue regions have relatively low values and can suffer from poor signal to noise ratios. While\nsmoothing can improve the image quality of the tissue regions, the inclusion of much higher valued vascular voxels\ncan skew the tissue values. It is thus desirable to smooth tissue voxels separately from other voxel types, as has been\npreviously implemented using mean filter kernels. We created a novel Masked Smoothing method that performs\nGaussian smoothing restricted to tissue voxels. Unlike previous methods, it is implemented as a combination of\nseparable kernels and is therefore fast enough to consider for clinical work, even for large kernel sizes.\nMethods: We compare our Masked Smoothing method to alternatives using Gaussian smoothing on an unaltered\nimage volume and Gaussian smoothing on an image volume with vascular voxels set to zero. Each method was tested\non simulation data, collected phantom data, and CT perfusion data sets. We then examined tissue voxels for bias and\nnoise reduction.\nResults: Simulation and phantom experiments demonstrate that Masked Smoothing does not bias the underlying\ntissue value, whereas the other smoothing methods create significant bias. Furthermore, using actual CT perfusion\ndata, we demonstrate significant differences in the calculated CBF and CBV values dependent on the smoothing\nmethod used.\nConclusion: The Masked Smoothing is fast enough to allow eventual clinical usage and can remove the bias of tissue\nvoxel values that neighbor blood vessels. Conversely, the other Gaussian smoothing methods introduced significant\nbias to the tissue voxels....
Background: Thermal ablation of colorectal liver metastases (CRLM) may result in local progression, which\ngenerally appear within a year of treatment. As the timely diagnosis of this progression allows potentially curative\nlocal treatment, an optimal follow-up imaging strategy is essential. PET-MRI is a one potential imaging modality,\ncombining the advantages of PET and MRI. The aim of this study is evaluate fluorine-18 deoxyglucose positron\nemission tomography (FDG) PET-MRI as a modality for detection of local tumor progression during the first year\nfollowing thermal ablation, as compared to the current standard, FDG PET-CT. The ability of FDG PET-MRI to detect\nnew intrahepatic lesions, and the extent to which FDG PET-MRI alters clinical management, inter-observer variability\nand patient preference will also be included as secondary outcomes.\nMethods/Design: Twenty patients undergoing treatment with radiofrequency or microwave ablation for (recurrent)\nCRLM will be included in this prospective trial. During the first year of follow-up, patients will be scanned at the VU\nUniversity Medical Center at 3-monthly intervals using a 4-phase liver CT, FDG PET-CT and FDG PET-MRI. Patients\ntreated with chemotherapy <6 weeks prior to scanning or with a contra-indication for MRI will be excluded. MRI will\nbe performed using both whole body imaging (mDixon) and dedicated liver sequences, including diffusion-weighted\nimaging, T1 in-phase and opposed-phase, T2 and dynamic contrast-enhanced imaging. The results of all modalities\nwill be scored by 4 individual reviewers and inter-observer agreement will be determined. The reference standard\nwill be histology or clinical follow-up. A questionnaire regarding patients� experience with both modalities will also be\ncompleted at the end of the follow-up year.\nDiscussion: Improved treatment options for local site recurrences following CRLM ablation mean that accurate\npost-ablation staging is becoming increasingly important. The combination of the sensitivity of MRI as a detection\nmethod for small intrahepatic lesions with the ability of FDG PET to visualize enhanced metabolism at the ablation\nsite suggests that FDG PET-MRI could potentially improve the accuracy of (early) detection of progressive disease,\nand thus allow swifter and more effective decision-making regarding appropriate treatment....
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