Biomedical subjects

K S Sampathkumaran

Publications and source records attributed to K S Sampathkumaran.

9 recordsLinked to original sources

PubMed1990

Hospital-wide distribution of nuclear medicine studies through a broadband digital network.

Nuclear medicine provides a good environment for the evaluation of picture archiving and communication systems (PACS) because of the relatively small quantity of digital data that are generated, leading to reduced requirements for storage, display, and transmission compared with those found in radiology. The PACS in nuclear medicine is characterized by use of a single computer as a central storage, display, and analysis node. Images are acquired with use of small, low-cost computers attached to each camera. This network configuration offers advantages of convenience, but with great reliance on a single computer. A campus-wide picture network is under development at Washington University employing broadband cable television technology supplemented by baseband Ethernet (Digital Equipment Corp, Maynard, MA) components. All areas of diagnostic radiology and nuclear medicine are connected via a PACS testbed project. A radiology information system, supporting over 250 terminals, provides digital tracking of patients and report generation and retrieval. A new image workstation is under development in conjunction with Digital Equipment Corp. This system will permit display in multiple windows of report information and images from various modalities. A lung scan demonstration project is now beginning that is designed to test the value of a PACS in nuclear medicine. Digitally acquired chest radiographs will be displayed on an image workstation in nuclear medicine along with digital ventilation and perfusion lung scans. It is hoped that time-consuming logistic bottlenecks now encountered in lung scan interpretation will be reduced.

Computer Communication Networks↗

PubMed1989

Three-dimensional display of gated cardiac blood-pool studies.

There has been little interest in use of single photon tomography in gated cardiac blood-pool imaging. This fact arises most likely from two principal causes: the difficulty associated with interpretation of images presented as series of beating slices, and the formidable computational burdens involved in processing the data. We have addressed both of these issues. A new method, called volume rendering, is used to generate realistic and easily interpreted three-dimensional images of the cardiac blood pool. These images of the beating heart can be displayed in a continuously rotating cine format or viewed in any orientation selected by the observer. Total computation time for a 16-frame gated study, including filtered backprojection, spatial and temporal filtering, and volume rendering, is 82.7 min employing a 32-bit computer and an array processor. With greater use of the array processor it should be possible to reduce the time to approximately 40 min, thus making routine use of these three-dimensional images clinically feasible.

Data Display↗

PubMed1987

An efficient and cost effective nuclear medicine image network.

An image network that is in use in a large nuclear medicine department is described. This network was designed to efficiently handle a large volume of clinical data at reasonable cost. Small, limited function computers are attached to each scintillation camera for data acquisition. The images are transferred by cable network or floppy disc to a large, powerful central computer for processing and display. Cost is minimized by use of small acquisition computers not equipped with expensive video display systems or elaborate analysis software. Thus, financial expenditure can be concentrated in a powerful central computer providing a centralized data base, rapid processing, and an efficient environment for program development. Clinical work is greatly facilitated because the physicians can process and display all studies without leaving the main reading area.

Computer Communication Networks↗

PubMed1984

Improved interpretation of gated cardiac images by use of digital filters.

The authors describe a digital filter that greatly enhances the quality of gated cardiac blood-pool images. Spatial filtering is accomplished with a minimum-mean-square-error (Wiener) filter incorporating measured camera blur and Poisson noise statistics. A low-pass temporal filter is then applied to each pixel, with the cutoff frequency determined from measurements of frequency spectra in 20 patients. This filter was evaluated in routine clinical use for nearly one year and found to significantly improve chamber definition, delineate wall motion abnormalities better, and reduce noise. To quantitatively assess the effect of the filter on image interpretation, four experienced observers evaluated wall motion in a series of mathematically simulated left ventricular images. ROC analysis revealed that accuracy in assessing wall motion was significantly greater with the filtered images.

Evaluation Studies as Topic↗

PubMed1983

Analysis of cardiac diastolic function: application in coronary artery disease.

Separation of systolic and diastolic parameters in gated cardiac blood-pool imaging (RVG) was achieved with the retention of two harmonics in the Fourier-series representation of the time-activity curve. Regional and global analysis of left-ventricular peak filling rate (PFR) and time to peak filling (TPF) was performed in 18 control subjects, 20 patients with coronary artery disease (CAD) but with normal RVG (normal regional wall motion and ejection fraction, and 16 CAD patients with abnormal RVG. In regional analysis of CAD patients, the standard deviation of the TPF histogram identified 13/20 (65%) of normal RVG patients and 12/16 (75%) of abnormal RVG patients as abnormal. In global analysis of CAD patients, PFR values identified 10/20 (50%) of normal RVG patients and 11/16 (69%) of abnormal RVG patients as abnormal. Thus, left-ventricular systolic and diastolic parameters can be separately measured with retention of higher-order harmonics in the Fourier transform, and regional inhomogeneity of diastolic filling can be detected in CAD patients with normal resting ejection fraction and wall motion.

Computers↗

PubMed1983

Rapid digital filtering.

Image filtering with the larger, and potentially most valuable, digital filters is very time-consuming, thus precluding use of these filters in routine clinical applications. A recently developed algorithm for spatial-domain filtering is described, and its speed is compared with those of conventional methods with and without an array processor. Using the new Chebyshev method, a 64 by 64 pixel image can be filtered on a standard 16-bit minicomputer with filters of size 3 by 3 to 23 by 23 in 1.4-9.2 sec. The conventional spatial-domain algorithm requires 3.8-71 sec. With an array processor, filtering is accomplished in 0.19-0.54 sec. Filtering in the frequency domain requires 34 sec without an array processor and 0.12 sec with one. Thus with this new Chebyshev algorithm, clinically practical digital filtering can be performed with large filters even without an array processor.

Computers↗

PubMed1982

Design and application of finite impulse response digital filters.

The finite impulse response (FIR) digital filter is a spatial domain filter with a frequency domain representation. The theory of the FIR filter is presented and techniques are described for designing FIR filters with known frequency response characteristics. Rational design principles are emphasized based on characterization of the imaging system using the modulation transfer function and physical properties of the imaged objects. Bandpass, Wiener, and low-pass filters were designed and applied to 201Tl myocardial images. The bandpass filter eliminates low-frequency image components that represent background activity and high-frequency components due to noise. The Wiener, or minimum mean square error filter 'sharpens' the image while also reducing noise. The Wiener filter illustrates the power of the FIR technique to design filters with any desired frequency response. The low-pass filter, while of relative limited use, is presented to compare it with a popular elementary 'smoothing' filter.

Filtration↗

PubMed1982

Digital filtering in nuclear medicine.

Digital filtering is a powerful mathematical technique in computer analysis of nuclear medicine studies. The basic concepts of object-domain and frequency-domain filtering are presented in simple, largely nonmathematical terms. Computational methods are described using both the Fourier transform and convolution techniques. The frequency response is described and used to represent the behavior of several classes of filters. These concepts are illustrated with examples drawn from a variety of important applications in nuclear medicine.

Computers↗

PubMed1981

A new scintigraphic technique for assessment of right atrial function.

Gated radionuclide imaging with 99mTc-labeled red blood cells was employed to assess changes in right atrial (RA) volume in 17 subjects. Studies were repeated within two hours in five of 12 normal subjects and at two and ten days after infarction in five patients. Time-activity curves were generated for the RA and right ventricle (RV) from variable regions of interest defined by automatic edge detection. The RA time-activity curve exhibited four phases: filling, early emptying, equilibration, and late emptying. Repeated measurements of RA early emptying rates correlated closely in normals (r = 0.93). Early RA emptying and RV filling rates corresponded closely (r = 0.89). In four patients with infarction, the RA emptying rate was slowed on the first study but had normalized by 10 days. In a patient with inferior infarction and suspected RV infarction, the RA emptying rate was depressed and remained so for 10 days. Thus, relative changes in right atrial volume can be assessed reproducibly by a radionuclide technique, which is relatively independent of geometric assumptions. This technique offers great promise as a method to assess atrial function in health and disease.

Adult↗