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R L Eisner

Publications and source records attributed to R L Eisner.

29 records · Page 2Linked to original sources
PubMed1986

Mapping of rRNA genes with integrable plasmids in Bacillus subtilis.

Integrable plasmids pGR102 and pWR103 containing ribosomal sequences from within the transcriptional units for 16S and 23S were used to transform Bacillus subtilis. To date, these plasmids integrated into 7 of 10 known rrn operons. Two such events occurred at unassigned operons, revealing a close linkage of the CAT gene of the plasmid to pha-1 situated between dal-1 and purB33 for rrnE and to thiA78 situated between glyB133 and re-12 for rrnD. All seven integration events that led to the loss of unique ribosomal BclI fragments can now be assigned to known rrn operons.

Bacillus subtilis↗
PubMed1986

Distance-weighted backprojection: a SPECT reconstruction technique.

A method of reconstruction of single-photon emission computed tomographic (SPECT) images--distance-weighted filtered backprojection--is described. The quality of SPECT images using the standard filtered backprojection algorithm for data obtained from 360 degrees acquisitions is limited by the loss of spatial resolution with distance, and the attenuation and scatter inherent in the planar images used for reconstruction. In contrast to the standard techniques in which a reconstructed pixel receives equal contributions from 180 degrees opposed views, distance--weighted filtered backprojection applies a variable weighting factor to the data such that the pixel receives greater weight from the closest planar views. Data derived from hot and cold spot phantoms as well as from various clinical studies show better spatial and contrast resolution with this new technique compared with the conventional 360 degrees algorithm.

Bone and Bones↗
PubMed1986

Fundamentals of 180 degree acquisition and reconstruction in SPECT imaging.

The accuracy of the reconstructed images obtained from a 180 degrees SPECT acquisition is directly related to the effects of resolution and attenuation in the acquired projection data. Computer simulation studies show that the tomographic point spread functions and the quality of 201Tl myocardial perfusion transaxial images depend upon the specific 180 degrees arc used for reconstruction. Significant distortions are predicted in 201Tl myocardial images reconstructed from both 180 degrees and 360 degree scans; with signal to noise being significantly better for 180 degree scans. An anterior 180 degrees scan with a starting angle between right lateral and 45 degrees RAO in 201Tl myocardial imaging is recommended. Reconstructed images acquired from 180 degrees and 360 degree elliptical orbits are predicted to show more distortion than those obtained from circular acquisitions.

Heart↗
PubMed1984

Advantages of list-mode data acquisition in gated blood-pool studies.

Because of physiologic R-R interval variability and arrhythmia, frame-mode acquisition of gated images may produce erroneous left ventricular volume curves, particularly in the diastolic filling phase. Eighteen patients in sinus rhythm underwent gated imaging in which both frame-mode and list-mode acquisitions were used. The systolic portions of the volume curves were similar in both studies, and the ejection fractions correlated well (R = 0.97). "Dropout" of data in the late diastolic phase, noted in 15 patients in whom frame mode was used, was not present in list mode, in which the atrial kick was clearly delineated. In additional patients with various arrhythmias, separate volume curves were obtained with list mode for premature, post-premature, and sinus beats. In patients with atrial fibrillation, a prominent peak mid-range on the R-R histogram was selected, and a complete volume curve was obtained. It was concluded that list-mode acquisition provided improved volume curves, with particular applicability in arrhythmic patients.

Journal Article↗
PubMed1984

I-123 HIPDM brain imaging with a rotating gamma camera and slant-hole collimator.

The performance of a slant-hole collimator was compared with that of a standard straight-bore, low-energy collimator for tomographic imaging of I-123-iodinated amine brain agents. Improved in-slice resolution was due to the greater proximity between collimator and the subjects' heads. We conclude that high quality tomographic images of the brain can be obtained from rotating cameras equipped with slant-hole collimators.

Brain↗
PubMed1982

Regional distribution of myocardial blood flow measured by single-photon emission tomography: comparison with in vitro counting.

An emission computed tomography system (SPECT), which uses a single large-field-of-view gamma camera, was evaluated for its ability to measure the relative distribution of myocardial blood flow and to assess the effect of attenuation, scatter, and cardiac motion on the tomographic images. Normalized regional myocardial counts from the SPECT images of the living dogs correlated closely with those from the anatomic slices and the samples counted at necropsy except for an over-estimate of tracer in the perfusion defect (SPECT) 57.7 compared to tissue count 32.1; p less than 0.05. The differences were less for the other imaging conditions. Heart and thorax motion, attenuation, and scatter contributed less than 25% to the over-estimate of defect counts. We conclude that the SPECT system accurately reflects regional distribution of myocardial blood flow except for overestimation of flow in regions of perfusion defects. Small perfusion defects might therefore be missed, but no artifactual defects are created.

Animals↗
PubMed1979

Theoretical resolution of computed tomography systems.

A simple analytic model is presented which is used to calculate the impulse response of a computed tomography system for parametric variations of the geometry. The model is useful for fan beam as well as parallel beam geometries. Results show that wide-aperture detector systems have intrinsic resolution limitations that are not mitigated by oversampling. Furthermore, the optimum focal spot size of the X-ray source is found to be dependent on the detector geometry.

Mathematics↗
PubMedDate not supplied

Differences due to collimator blurring in cardiac images with use of circular and elliptic camera orbits.

BACKGROUND: In cardiac imaging systems, an elliptic acquisition orbit about the patient can be used to enhance resolution of single photon emission computed tomography (SPECT) images by minimizing the distance between the object imaged and the rotating detector system. In this study artifacts from images acquired with the standard circular acquisition are compared with those acquired with various elliptic acquisitions. METHODS AND RESULTS: With the use of elliptic camera orbits of different eccentricities, simulated projection data were generated from a slice through the left ventricle (LV). The projection data included a simulation of the degradation due to the depth-dependent response of the collimator. As is common in many clinical systems, SPECT images were reconstructed with the standard filtered backprojection algorithm without correction for the collimator response. When the ratio of the major-to-minor axis of the acquisition arc is changed from 1 (circular) to 1.5 (elliptic), reconstructed SPECT images show an additional loss of counts (about 10%) in the apical region of the LV. The severity of the apical defect is also dependent on the starting angle of the acquisition arc. When the starting angle is changed from 0 degrees (detector parallel to the major axis of the LV) to 60 degrees, the ratio between the minimum count in the apical region and the maximum count in the left ventricular myocardial wall decreases by as much as 20%. CONCLUSIONS: SPECT image artifacts from elliptic acquisitions are significantly more severe than those from circular acquisitions. Because of the significant difference in images reconstructed from circular and elliptic acquisitions, standardized normal files acquired from circular acquisitions should not be used for comparisons with patient data acquired from elliptic acquisitions.

Algorithms↗