Prof. Yi-Hwa Liu Profile

Prof. Yi-Hwa Liu

Associate Professor at Yale Univ

SPIE Involvement:

Author

Publications (5)

Proceedings Article | 18 March 2008 Paper

Generic iterative reconstruction of multi-pinhole SPECT

William Ryder, Matthew Brennan, Albert Sinusas, Yi-Hwa Liu

Proceedings Volume 6913, 69132M (2008) https://doi.org/10.1117/12.769519

KEYWORDS: Sensors, Collimators, Single photon emission computed tomography, Reconstruction algorithms, Expectation maximization algorithms, Image processing, Monte Carlo methods, Heart, Signal to noise ratio, Spatial resolution

Read Abstract +

Proceedings Article | 17 March 2008 Paper

Hotspot quantification of myocardial focal tracer uptake from molecular targeted SPECT/CT images: experimental validation

Yi-Hwa Liu, Zakir Sahul, Christopher Weyman, William Ryder, Donald Dione, Lawrence Dobrucki, Choukri Mekkaoui, Matthew Brennan, Xiaoyue Hu, Christi Hawley, Albert Sinusas

Proceedings Volume 6915, 69150N (2008) https://doi.org/10.1117/12.768985

KEYWORDS: Single photon emission computed tomography, Image segmentation, Signal attenuation, Error analysis, X-ray computed tomography, Computed tomography, In vivo imaging, Heart, Medicine, X-ray imaging

Read Abstract +

We have developed a new single photon emission computerized tomography (SPECT) hotspot quantification method incorporating extra cardiac activity correction and hotspot normal limit estimation. The method was validated for estimation accuracy of myocardial tracer focal uptake in a chronic canine model of myocardial infarction (MI). Dogs (n = 4) at 2 weeks post MI were injected with Tl-201 and a Tc-99m-labeled hotspot tracer targeted at matrix metalloproteinases (MMPs). An external point source filled with Tc-99m was used for a reference of absolute radioactivity. Dual-isotope (Tc-99m/Tl-201) SPECT images were acquired simultaneously followed by an X-ray CT acquisition. Dogs were sacrificed after imaging for myocardial gamma well counting. Images were reconstructed with CT-based attenuation correction (AC) and without AC (NAC) and were quantified using our quantification method. Normal limits for myocardial hotspot uptake were estimated based on 3 different schemes: maximum entropy, meansquared-error minimization (MSEM) and global minimization. Absolute myocardial hotspot uptake was quantified from SPECT images using the normal limits and compared with well-counted radioactivity on a segment-by-segment basis (n = 12 segments/dog). Radioactivity was expressed as % injected dose (%ID). There was an excellent correlation (r = 0.78-0.92) between the estimated activity (%ID) derived using the SPECT quantitative approach and well-counting, independent of AC. However, SPECT quantification without AC resulted in the significant underestimation of radioactivity. Quantification using SPECT with AC and the MSEM normal limit yielded the best results compared with well-counting. In conclusion, focal myocardial "hotspot" uptake of a targeted radiotracer can be accurately quantified in vivo using a method that incorporates SPECT imaging with AC, an external reference, background scatter compensation, and a suitable normal limit. This hybrid SPECT/CT approach allows for the serial non-invasive quantitative evaluation of molecular targeted tracers in the heart.

Proceedings Article | 6 March 2006 Paper

A new approach of 3D SPECT reconstruction for near-field coded aperture imaging

Baoming Hong, Zhiping Mu, Yi-Hwa Liu

Proceedings Volume 6142, 61424D (2006) https://doi.org/10.1117/12.653300

KEYWORDS: Coded apertures, Expectation maximization algorithms, 3D image reconstruction, 3D image processing, Single photon emission computed tomography, Near field, Coded aperture imaging, Reconstruction algorithms, Collimation, Image restoration

Read Abstract +

Proceedings Article | 26 June 1992 Paper

Blind deconvolution of 2D and 3D fluorescent micrographs

Vijaykumar Krishnamurthi, Yi-Hwa Liu, Timothy Holmes, Badrinath Roysam, James Turner

Proceedings Volume 1660, (1992) https://doi.org/10.1117/12.59544

KEYWORDS: Point spread functions, Deconvolution, Expectation maximization algorithms, Reconstruction algorithms, 3D image processing, Computer simulations, Optical transfer functions, 3D modeling, Photomicroscopy, Calibration

Read Abstract +

This paper presents recent results of our reconstructions of 3-D data from Drosophila chromosomes as well as our simulations with a refined version of the algorithm used in the former. It is well known that the calibration of the point spread function (PSF) of a fluorescence microscope is a tedious process and involves esoteric techniques in most cases. This problem is further compounded in the case of confocal microscopy where the measured intensities are usually low. A number of techniques have been developed to solve this problem, all of which are methods in blind deconvolution. These are so called because the measured PSF is not required in the deconvolution of degraded images from any optical system. Our own efforts in this area involved the maximum likelihood (ML) method, the numerical solution to which is obtained by the expectation maximization (EM) algorithm. Based on the reasonable early results obtained during our simulations with 2-D phantoms, we carried out experiments with real 3-D data. We found that the blind deconvolution method using the ML approach gave reasonable reconstructions. Next we tried to perform the reconstructions using some 2-D data, but we found that the results were not encouraging. We surmised that the poor reconstructions were primarily due to the large values of dark current in the input data. This, coupled with the fact that we are likely to have similar data with considerable dark current from a confocal microscope prompted us to look into ways of constraining the solution of the PSF. We observed that in the 2-D case, the reconstructed PSF has a tendency to retain values larger than those of the theoretical PSF in regions away from the center (outside of those we considered to be its region of support). This observation motivated us to apply an upper bound constraint on the PSF in these regions. Furthermore, we constrain the solution of the PSF to be a bandlimited function, as in the case in the true situation. We have derived two separate approaches for implementing the constraint. One approach involves the mathematical rigors of Lagrange multipliers. This approach is discussed in another paper. The second approach involves an adaptation of the Gershberg Saxton algorithm, which ensures bandlimitedness and non-negativity of the PSF. Although the latter approach is mathematically less rigorous than the former, we currently favor it because it has a simpler implementation on a computer and has smaller memory requirements. The next section describes briefly the theory and derivation of these constraint equations using Lagrange multipliers.

Proceedings Article | 1 May 1991 Paper

Preliminary tests of maximum likelihood image reconstruction method on 3-D real data and some practical considerations for the data corrections

Yi-Hwa Liu, Timothy Holmes, Matthew Koshy

Proceedings Volume 1428, (1991) https://doi.org/10.1117/12.44141

KEYWORDS: 3D image processing, 3D modeling, 3D image reconstruction, Image restoration, Point spread functions, Data corrections, Luminescence, Expectation maximization algorithms, Laser systems engineering, Microscopy

Read Abstract +

View contact details

UPDATE YOUR PROFILE

Is this your profile? Update it now.

Sign into your SPIE.org account

Don’t have a profile and want one?

Create an account on SPIE.org

Keywords/Phrases

Search In:

Publication Years