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E V Di Bella

Publications and source records attributed to E V Di Bella.

8 recordsLinked to original sources
PubMed2001

Compartmental modeling of technetium-99m-labeled teboroxime with dynamic single-photon emission computed tomography: comparison with static thallium-201 in a canine model.

UNLABELLED: Di Bella EVR, Ross SG, Kadrmas DJ, et al. Compartmental modeling of technetium-99m-labeled teboroxime with dynamic single-photon emission computed tomography: Comparison with static thallium-201 in a canine model. Invest Radiol 2001;36:178-185. RATIONALE AND OBJECTIVES: A compartmental modeling approach to deriving kinetic parameters from a time series of single-photon emission computed tomography (SPECT) images of technetium-99m-labeled (99mTc-) teboroxime may have value for semiquantitative assessment of myocardial perfusion. This study investigated the value of the kinetic parameters derived from a two-compartment model of 99mTc-teboroxime for measuring myocardial perfusion and compared it with static thallium-201 (201Tl) uptake and microsphere-measured blood flow in dogs. METHODS: Experiments were successfully conducted in 9 of 11 open-chest dogs. During adenosine stress, a single complete set of projections of 201Tl uptake was acquired. 99mTc-teboroxime was then injected during adenosine stress, and a complete set of projections was acquired every 5.7 seconds for 17 minutes. Resting studies were performed on 4 of the animals. All of the projection sets were reconstructed with an iterative algorithm and incorporated corrections for attenuation and the geometric response of the collimators. Regional kinetic parameters (washin and washout) were determined semiautomatically from the time series of reconstructed 99mTc-teboroxime images and registered with microsphere data. Regional washin estimates were compared with 201Tl intensities and myocardial blood flows determined from microspheres. RESULTS: Optimally scaled 99mTc-teboroxime washin parameters and 201Tl uptakes were correlated with microsphere-determined blood flows (r = 0.91, y = 0. 99x + 0.01, and r = 0.92, y = 0.88x + 0.28, respectively). In six of the studies, the left anterior descending coronary artery was occluded, and stress occluded-to-normal (O/N) ratios were calculated. The O/N ratios were 0.32 +/- 0.17 as determined from microspheres injected with 201Tl and 0.38 +/- 0.29 from microspheres injected with 99mTc-teboroxime (P = NS). The O/N ratios were 0.48 +/- 0.16 for static 201Tl uptake and 0.27 +/- 0.21 for 99mTc-teboroxime washin (P < 0.05). CONCLUSIONS: Both 201Tl uptake and 99mTc-teboroxime kinetic parameters were well correlated with flow. The 99mTc-teboroxime washin parameters offer semiquantitative flow values and provide greater defect contrast than can be obtained with 201Tl uptake values.

Animals↗
PubMed2001

Feasibility of dual-isotope coincidence/single-photon imaging of the myocardium.

UNLABELLED: Hybrid PET scanners offer the possibility of obtaining myocardial viability information from coincidence imaging of the positron emitter (18)F-FDG and perfusion measurements from a single-photon tracer-potentially simultaneously. This new approach is less costly and more readily available than dedicated PET and offers potential for improved FDG resolution and sensitivity compared with SPECT with 511-keV collimators. Simultaneous imaging of the coincidence and single-photon events offers the further advantages of automatic image registration and reduced imaging time. However, the feasibility of simultaneous coincidence/single-photon imaging or even immediately sequential imaging is unknown. In this study, the potential of using standard low-energy high-resolution (LEHR) collimators with hybrid PET to obtain coincidence and SPECT data was assessed. METHODS: Phantom and human studies were performed to investigate the effect of LEHR collimators on FDG coincidence imaging with a hybrid PET system, the effect of the presence of (99m)Tc during FDG coincidence imaging with LEHR collimators, and the effect of the presence of FDG during (99m)Tc SPECT imaging. RESULTS: FDG images were somewhat degraded (a measure of myocardial nonuniformity increased 10%) with LEHR collimators. With 148 MBq (4 mCi) (99m)Tc present during FDG imaging of a phantom, image quality was maintained and the number of detected coincidences changed by <5%. With (99m)Tc/(18)F whole-body ratios of 7:1, crosstalk from (18)F photons accounted for the majority of counts in the (99m)Tc SPECT images and resulted in severe artifacts. The artifacts were decreased with a simple crosstalk correction scheme but remained problematic. CONCLUSION: (99m)Tc/(18)F ratios of at least 9:1 and state-of-the-art reconstruction and crosstalk correction are likely to be required to perform immediately sequential coincidence/single-photon imaging of the myocardium with clinically useful results. Additional challenges remain before simultaneous imaging of coincidence events and single photons can be realized in practice.

Feasibility Studies↗
PubMed2001

Reconstruction of dynamic renal tomographic data acquired by slow rotation.

UNLABELLED: Nuclear medicine renal studies can be performed using slow-rotation SPECT, but reconstruction of such data is largely underdetermined. METHODS: A new method of reconstruction of data acquired using slow camera rotations was developed. In this method we used a factor model of the data in which the factors and factor coefficients were determined by modeling their relationship directly with the projection measurements. This was done by solving a least-squares problem that fits the projections of factors and factor coefficients to the projection data with nonnegativity constraints imposed on the solution. The method was tested on computer simulations and applied to experimental renal (99m)Tc-mercaptoacetyltriglycine canine and patient studies. RESULTS: Computer simulations showed that the extracted time-activity curves of kidneys agreed well with the simulated curves for data with noise levels similar to those in the experimental studies. In the canine study, the method showed that >2 factors were necessary to adequately reproduce the kinetics of the kidney. In the patient study, the method was able to extract separate factors that correspond to the kidney cortex and the kidney pelvis. CONCLUSION: The computer simulation, the canine study, and the patient study all show that reconstructions of the data obtained with 1 detector displayed artifacts, whereas reconstructions of the data obtained with 2 and 3 detectors were free of artifacts. Computer simulations showed that the method gives accurate results that allow quantitation.

Algorithms↗
PubMed2000

Factor analysis with a priori knowledge--application in dynamic cardiac SPECT.

Two factor analysis of dynamic structures (FADS) methods for the extraction of time-activity curves (TACs) from cardiac dynamic SPECT data sequences were investigated. One method was based on a least squares (LS) approach which was subject to positivity constraints. The other method was the well known apex-seeking (AS) method. A post-processing step utilizing a priori information was employed to correct for the non-uniqueness of the FADS solution. These methods were used to extract 99mTc-teboroxime TACs from computer simulations and from experimental canine and patient studies. In computer simulations, the LS and AS methods, which are completely different algorithms, yielded very similar and accurate results after application of the correction for non-uniqueness. FADS-obtained blood curves correlated well with curves derived from region of interest (ROI) measurements in the experimental studies. The results indicate that the factor analysis techniques can be used for semi-automatic estimation of activity curves derived from cardiac dynamic SPECT images, and that they can be used for separation of physiologically different regions in dynamic cardiac SPECT studies.

Animals↗
PubMed1999

Blind estimation of compartmental model parameters.

Computation of physiologically relevant kinetic parameters from dynamic PET or SPECT imaging requires knowledge of the blood input function. This work is concerned with developing methods to accurately estimate these kinetic parameters blindly; that is, without use of a directly measured blood input function. Instead, only measurements of the output functions--the tissue time-activity curves--are used. The blind estimation method employed here minimizes a set of cross-relation equations, from which the blood term has been factored out, to determine compartmental model parameters. The method was tested with simulated data appropriate for dynamic SPECT cardiac perfusion imaging with 99mTc-teboroxime and for dynamic PET cerebral blood flow imaging with 15O water. The simulations did not model the tomographic process. Noise levels typical of the respective modalities were employed. From three to eight different regions were simulated, each with different time-activity curves. The time-activity curve (24 or 70 time points) for each region was simulated with a compartment model. The simulation used a biexponential blood input function and washin rates between 0.2 and 1.3 min(-1) and washout rates between 0.2 and 1.0 min(-1). The system of equations was solved numerically and included constraints to bound the range of possible solutions. From the cardiac simulations, washin was determined to within a scale factor of the true washin parameters with less than 6% bias and 12% variability. 99mTc-teboroxime washout results had less than 5% bias, but variability ranged from 14% to 43%. The cerebral blood flow washin parameters were determined with less than 5% bias and 4% variability. The washout parameters were determined with less than 4% bias, but had 15-30% variability. Since washin is often the parameter of most use in clinical studies, the blind estimation approach may eliminate the current necessity of measuring the input function when performing certain dynamic studies.

Brain↗
PubMed1998

Iterative reconstruction of fluorine-18 SPECT using geometric point response correction.

UNLABELLED: This article demonstrates resolution recovery in 18F SPECT image reconstruction by using an iterative algorithm that corrects for the system geometric response. METHODS: Patient and phantom studies were performed using a Picker PRISM 3000 three-detector SPECT system (Picker International, Inc., Cleveland, OH) to image 18F with 511 keV collimators. A measured point response function of the imaging system was used in an iterative reconstruction algorithm in which the projector and backprojector modeled the system point response function by using an efficient layer-by-layer blurring technique. The blurring function was a five-element kernel in the shape of a cross. The iterative reconstruction algorithm was an ordered-subset maximum-likelihood expectation maximization algorithm. RESULTS: The iterative reconstruction algorithm with geometric response correction showed an improvement in resolution over the filtered backprojection reconstruction and the iterative reconstruction without correction. CONCLUSION: The proposed iterative reconstruction algorithm with geometric response correction is efficient and effective with significant resolution recovery.

Aged↗
PubMed1996

Attenuation artifacts in SPECT: effect of wrap-around lung in 180 degrees cardiac studies.

UNLABELLED: We estimated that in 75%-90% of PET 82Rb patients the left lung appeared to wrap around the anterior aspect of the left ventricle. We used clinical PET 82Rb myocardial perfusion studies as the input to a SPECT computer simulation model to determine if patients with left lung wrap-around displayed consistent artifacts in reconstructed SPECT images. In particular, we sought an explanation for the hot lateral wall seen in SPECT images from normal female and male patients. METHODS: Attenuated SPECT 201Tl emission data were simulated from a mid-ventricular slice in 10 randomly selected clinical PET 82Rb studies with left lung wrap-around. In these same cases, the influence of left lung wrap-around was removed by assigning the left lung an attenuation coefficient which matched that of the heart. Five randomly selected clinical PET 82Rb studies without left lung wrap-around were also processed with our model. RESULTS: In all 10 cases with left lung wrap-around, reconstructed SPECT images showed the hot lateral wall artifact with a mean septal-to-lateral wall count ratio of 0.86. With left lung wrap-around removed in the same 10 patients, reconstructed images did not show hot lateral wall (mean septal-to-lateral wall count ratio = 1.07). The 5 cases without left lung wrap-around did not show hot lateral wall (mean septal-to-lateral wall count ratio = 1.04) and the ratios changed little with the filling of the left lung (mean septal-to-lateral wall count ratio = 1.05). CONCLUSION: Results of our PET-to-SPECT computer simulation model showed that the hot lateral wall artifact found in SPECT myocardial perfusion images was related to the orientation and positions of the left ventricle and the left lung.

Artifacts↗