Biomedical subjects

K S Malagari

Publications and source records attributed to K S Malagari.

5 recordsLinked to original sources

PubMed2004

Threshold selection in virtual bronchoscopy: phantom study and clinical implications.

PURPOSE: To investigate the effect of the threshold selection on the apparent diameter of a virtual bronchus and the virtual wall morphology and to examine the parameters that can affect the selection of the appropriate threshold for virtual bronchoscopy with single slice computed tomography. MATERIAL AND METHODS: A bronchial phantom containing plastic tubes simulating the airways of the tracheobronchial tree was constructed. The diameters of the virtual images of these tubes were measured using various thresholds for two different materials surrounding the tubes: air and water. These measurements were correlated with the density in HU of the walls. Furthermore, data from 20 virtual bronchoscopies in patients were retrospectively analyzed in the same way. RESULTS: The diameter of a virtual bronchus is strongly affected by the selected threshold. The appropriate threshold for accurate diameter representation depends on the density of the bronchial wall. CONCLUSION: Our results suggest that in clinical practice a single threshold value cannot be used for imaging all segments of the tracheobronchial tree. While a value of -520 is appropriate for the trachea and lobar segments, values down to -720 could be needed on the level of segmental and subsegmental bronchi. At these levels, a threshold value about 65 HU more negative than the value where the artificial holes appear on the virtual bronchial walls could be used.

Bronchoscopes↗

PubMed1995

Digital chest radiography: comparison of unprocessed and processed images in the detection of solitary pulmonary nodules.

PURPOSE: To compare the accuracy with which simulated solitary pulmonary nodules can be identified on digital images of the chest that are unprocessed, processed with adaptive spatial filtering, or processed with global filtering. MATERIALS AND METHODS: Six experienced chest radiologists evaluated 408 test radiographs (136 from each of the three types, half with simulated nodules) and judged whether a nodule was present. Data from the 2,448 observations were evaluated by means of a receiver operating characteristic curve with location methods. RESULTS: Accuracy was significantly better with the adaptive filter technique than with the global technique (P < .05), and it was better with adaptive filtering than with no processing in the detection of pulmonary nodules in the mediastinal-subdiaphragmatic areas (P < .05). No significant difference was found between no processing and global filtering. CONCLUSION: Adaptive filtration is superior to global filtration in the identification of solitary pulmonary nodules and is superior to no processing in nodules projected over the radiopaque areas of the thorax on digital images.

Algorithms↗

PubMed1992

Enhancement of chest images by automatic adaptive spatial filtering.

Postprocessing of the image data is an exciting capability of digital radiography that may improve diagnostic performance. We present a new algorithm that selectively enhances edges and contrast in both lungs and mediastinum while minimally amplifying noise in chest images. Using different size kernels, two smoothed images are generated from the original chest image. The two regions of interest (lungs and mediastinum) are identified based on the distribution of pixel values in the image. A modified nonlinear unsharp mask subtraction technique is then applied. The resulting image has enhanced high- and middle-frequency information in the mediastinum without distorting lung parenchyma or significantly enhancing noise. We consider that the technique employed in this study could be suitable for routine use although its true effectiveness in improving diagnostic accuracy awaits observer-performance evaluation that is currently under way.

Adult↗

PubMedDate not supplied

Complications of percutaneous nephrostomy, percutaneous insertion of ureteral endoprosthesis, and replacement procedures.

PURPOSE: The aim of the present study was to record and identify the frequency of complications following percutaneous nephrostomy, replacement of nephrostomy drains and percutaneous insertion of ureteral endoprostheses. METHODS: During a 10-year period 341 patients were referred to our department with indications for percutaneous nephrostomy and/or percutaneous insertion of a ureteral endoprosthesis, and a total of 1036 interventional procedures were performed (nephrostomy, catheter change, stenting). RESULTS: There were three major complications (0.29%): two patients died during the first 30 days after the procedure, due to aggravation of their condition caused by the procedure, and one patient had retroperitoneal bleeding requiring surgery. There were 76 complications of intermediate severity (7.33%): catheter or stent displacement (n = 37, 3.57%) catheter occlusion (n = 18, 1.73%), hematuria (n = 12, 1.16%), and urinary tract infection (n = 9, 0.87%). The 55 minor complications (5.3%) comprised inflammation of the skin at the site of insertion of the percutaneous catheter. CONCLUSION: The small number of complications observed during acts of interventional uroradiology prove transcutaneous manipulations to be safe medical procedures.

Adolescent↗

PubMedDate not supplied

Percutaneous metallic self-expandable endoprostheses in biliary obstruction caused by metastatic cancer.

BACKGROUND/AIMS: Up to now, all reports about metallic stents concerned mostly patients with obstructive jaundice due to primary cancer although some of these series included a small number of patients with metastatic disease as a cause of occlusion of the bile ducts. The question of whether they should be used in patients with biliary obstruction due to metastatic disease, and consequently have a limited life expectancy, is investigated. PATIENTS AND METHODS: Between January 1994 and April 1995, we inserted percutaneously 20 metallic self-expandable endoprostheses in 14 patients with obstructive jaundice due to metastatic disease. RESULTS: Twelve patients died with a mean survival of 144.6 (range 25-338) days without any evidence of biliary reobstruction. For 2 patients, we have followup no longer than 30 days. Thirty day mortality was 7.2% (1/14). Jaundice reoccurred in one patient but wasn't related to stent obstruction, and he died during the first 30 days. We had 2 cases with moderate hemobilia. CONCLUSION: We believe that the use of metal stents in patients with obstructive jaundice due to metastatic disease is justified. Their high initial cost is offset by their prolong patency, decreased complication rate and shorter hospitalization.

Aged↗