Prof. Sabee Molloi Profile

Prof. Sabee Molloi

Professor and Vice Chairman of Research, Radiological Sciences at Univ. of California, Irvine

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Publications (16)

SPIE Journal Paper | 31 October 2023

Low-dose quantitative CT myocardial flow measurement using a single volume scan: phantom and animal validation

Logan Hubbard, Sabee Molloi

JMI, Vol. 10, Issue 05, 056002, (October 2023) https://doi.org/10.1117/12.10.1117/1.JMI.10.5.056002

KEYWORDS: Computed tomography, Animals, Tissues, Microspheres, Blood, Attenuation, Animal model studies, Data modeling, Myocardium, Arteries

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SPIE Journal Paper | 10 July 2023

Coronary artery calcium mass measurement based on integrated intensity and volume fraction techniques

Dale Black, Xingshuo Xiao, Sabee Molloi

JMI, Vol. 10, Issue 04, 043502, (July 2023) https://doi.org/10.1117/12.10.1117/1.JMI.10.4.043502

KEYWORDS: Calcium, Magnesium, Arteries, Reproducibility, Voxels, Calibration, Computed tomography, Linear regression, Optical simulations, Image segmentation

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PurposeAgatston scoring does not detect all the calcium present in computed tomography scans of the heart. A technique that removes the need for thresholding and quantifies calcium mass more accurately and reproducibly is needed.ApproachIntegrated intensity and volume fraction techniques were evaluated for accurate quantification of calcium mass. Integrated intensity calcium mass, volume fraction calcium mass, Agatston scoring, and spatially weighted calcium scoring were compared with known calcium mass in simulated and physical phantoms. The simulation was created to match a 320-slice CT scanner. Fat rings were added to the simulated phantoms, which resulted in small (30 × 20 cm2), medium (35 × 25 cm2), and large (40 × 30 cm2) phantoms. Three calcification inserts of different diameters and hydroxyapatite densities were placed within the phantoms. All the calcium mass measurements were repeated across different beam energies, patient sizes, insert sizes, and densities. Physical phantom images from a previously reported study were then used to evaluate the accuracy and reproducibility of the techniques.ResultsBoth integrated intensity calcium mass and volume fraction calcium mass yielded lower root mean squared error (RMSE) and deviation (RMSD) values than Agatston scoring in all the measurements in the simulated phantoms. Specifically, integrated calcium mass (RMSE: 0.49 mg, RMSD: 0.49 mg) and volume fraction calcium mass (RMSE: 0.58 mg, RMSD: 0.57 mg) were more accurate for the low-density stationary calcium measurements than Agatston scoring (RMSE: 3.70 mg, RMSD: 2.30 mg). Similarly, integrated calcium mass (15.74%) and volume fraction calcium mass (20.37%) had fewer false-negative (CAC = 0) measurements than Agatston scoring (75.00%) and spatially weighted calcium scoring (26.85%), on the low-density stationary calcium measurements.ConclusionThe integrated calcium mass and volume fraction calcium mass techniques can potentially improve risk stratification for patients undergoing calcium scoring and further improve risk assessment compared with Agatston scoring.

SPIE Journal Paper | 12 March 2019 Open Access

Initial evaluation of three-dimensionally printed patient-specific coronary phantoms for CT-FFR software validation

Lauren Shepard, Kelsey Sommer, Erin Angel, Vijay Iyer, Michael Wilson, Frank Rybicki, Dimitrios Mitsouras, Sabee Molloi, Ciprian Ionita

JMI, Vol. 6, Issue 02, 021603, (March 2019) https://doi.org/10.1117/12.10.1117/1.JMI.6.2.021603

KEYWORDS: Computed tomography, 3D printing, Arteries, Image segmentation, Software validation, Diagnostics, 3D image processing, Resistance, Distance measurement, Aorta

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Proceedings Article | 9 March 2018 Presentation + Paper

CT investigation of patient-specific phantoms with coronary artery disease

Lauren Shepard, Kelsey Sommer, Erin Angel, Vijay Iyer, Michael Wilson, Frank Rybicki, Dimitrios Mitsouras, Sabee Molloi, Ciprian Ionita

Proceedings Volume 10573, 105731V (2018) https://doi.org/10.1117/12.2292918

KEYWORDS: Computed tomography, Arteries, 3D printing, Angiography, Image segmentation

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Proceedings Article | 6 May 2004 Paper

Evaluation of a photon-counting x-ray imaging detector based on microchannel plates for mammography applications

Polad Shikhaliev, Tong Xu, Sabee Molloi

Proceedings Volume 5368, (2004) https://doi.org/10.1117/12.535476

KEYWORDS: Sensors, Microchannel plates, X-ray imaging, Electronics, X-rays, Photon counting, Modulation transfer functions, Image acquisition, Imaging systems, Prototyping

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SPIE Journal Paper | 1 October 2003

Vessel diameter estimation in x-ray angiographic images using a watergauge algorithm

Zikuan Chen, Tong Xu, Sabee Molloi

JEI, Vol. 12, Issue 04, (October 2003) https://doi.org/10.1117/12.10.1117/1.1605958

KEYWORDS: X-rays, Edge detection, Angiography, X-ray imaging, Detection and tracking algorithms, Imaging systems, Algorithm development, Densitometry, Convolution, Calibration

SPIE Journal Paper | 1 June 2003

Multiresolution vessel tracking in angiographic images using valley courses

Zikuan Chen, Sabee Molloi

OE, Vol. 42, Issue 06, (June 2003) https://doi.org/10.1117/12.10.1117/1.1571829

KEYWORDS: Wavelets, Angiography, Detection and tracking algorithms, Denoising, Algorithm development, Image resolution, Edge detection, X-rays, Stars, Image processing

Proceedings Article | 9 May 2002 Paper

Fast vessel identification using polyphase decomposition and intercomponent processing

Zikuan Chen, Sabee Molloi

Proceedings Volume 4684, (2002) https://doi.org/10.1117/12.467135

KEYWORDS: Image processing, Image fusion, Angiography, Binary data, Digital imaging, Image segmentation, Feature extraction, Visualization, Signal processing, Detection and tracking algorithms

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Proceedings Article | 9 May 2002 Paper

Vessel-valley-course generation algorithm for quantitative analysis of angiograms

Zikuan Chen, Sabee Molloi

Proceedings Volume 4684, (2002) https://doi.org/10.1117/12.467115

KEYWORDS: Angiography, Image segmentation, Quantitative analysis, Detection and tracking algorithms, Reconstruction algorithms, Stars, X-rays, Image processing algorithms and systems, Edge detection, Binary data

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Proceedings Article | 3 May 2002 Paper

Arbitrary shape region-of-interest fluoroscopy system

Tong Xu, Huy Le, Sabee Molloi

Proceedings Volume 4682, (2002) https://doi.org/10.1117/12.465621

KEYWORDS: X-rays, Fluoroscopy, Image filtering, X-ray imaging, Image quality, Chromium, Image segmentation, Visualization, Image processing, Modulation

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Proceedings Article | 3 May 2002 Paper

New detector concept for x-ray imaging using edge-on illuminated porous plates

Polad Shikhaliev, Sabee Molloi

Proceedings Volume 4682, (2002) https://doi.org/10.1117/12.465602

KEYWORDS: Microchannel plates, Sensors, X-ray imaging, Imaging systems, Electronics, X-rays, Quantum efficiency, X-ray detectors, Spatial resolution, Diagnostics

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Proceedings Article | 11 April 1996 Paper

X-ray beam equalization for digital fluoroscopy

Sabee Molloi, Jerry Tang, Martin Marcin, Yifang Zhou, Behzad Anvar

Proceedings Volume 2708, (1996) https://doi.org/10.1117/12.237780

KEYWORDS: X-rays, X-ray imaging, Chest, Image processing, Radiography, Attenuators, Image quality, Image intensifiers, Signal to noise ratio, Fluoroscopy

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The concept of radiographic equalization has previously been investigated. However, a suitable technique for digital fluoroscopic applications has not been developed. The previously reported scanning equalization techniques cannot be applied to fluoroscopic applications due to their exposure time limitations. On the other hand, area beam equalization techniques are more suited for digital fluoroscopic applications. The purpose of this study is to develop an x- ray beam equalization technique for digital fluoroscopic applications that will produce an equalized radiograph with minimal image artifacts and tube loading. Preliminary unequalized images of a humanoid chest phantom were acquired using a digital fluoroscopic system. Using this preliminary image as a guide, an 8 by 8 array of square pistons were used to generate masks in a mold with CeO². The CeO² attenuator thicknesses were calculated using the gray level information from the unequalized image. The generated mask was positioned close to the focal spot (magnification of 8.0) in order to minimize edge artifacts from the mask. The masks were generated manually in order to investigate the piston and matrix size requirements. The development of an automated version of mask generation and positioning is in progress. The results of manual mask generation and positioning show that it is possible to generate equalized radiographs with minimal perceptible artifacts. The equalization of x-ray transmission across the field exiting from the object significantly improved the image quality by preserving local contrast throughout the image. Furthermore, the reduction in dynamic range significantly reduced the effect of x-ray scatter and veiling glare from high transmission to low transmission areas. Also, the x-ray tube loading due to the mask assembly itself was negligible. In conclusion it is possible to produce area beam compensation that will be compatible with digital fluoroscopy with minimal compensation artifacts. The compensation process produces an image with equalized signal to noise ratio in all parts of the image.

Proceedings Article | 11 April 1996 Paper

Scatter-glare estimation for quantitative cardiac imaging

Sabee Molloi, Greg Wamsely, Yifang Zhou

Proceedings Volume 2708, (1996) https://doi.org/10.1117/12.237778

KEYWORDS: X-rays, Lead, Angiography, Cardiac imaging, Image acquisition, Image processing, Animal model studies, X-ray imaging, Error analysis, Convolution

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Convolution-filtering methods and direct beam stop techniques have previously been investigated for estimation of scatter-glare distribution in images acquired using digital fluoroscopic systems. The purpose of this study is to compare the error in scatter-glare estimation for a direct beam stop technique and a convolution technique. Also, the change in scatter-glare intensity due to contrast material injection for ventriculography and coronary arteriography was quantified. Three different methods were used to estimate scatter-glare intensity in humanoid chest phantom and animal model images. A lead strip was used to scan the x-ray field for direct measurement of scatter-glare intensity in every pixel in the image. An array of lead beam-stops were used in order to sample scatter-glare intensity. An interpolation technique was used to estimate scatter-glare intensity for the remaining pixels in the image. Scatter-glare intensity was also estimated using a convolution filtering technique. This technique utilizes exposure parameters and image gray levels to assign equivalent Lucite thicknesses for every pixel in the image. The thickness information is then used to estimate scatter-glare intensity on a pixel-by-pixel basis. Finally, an array of lead beam-stops were used to measure the change in scatter-glare intensity due to contrast material injection. This was done by leaving the array of lead beam-stops in the x-ray beam for ventriculography and coronary arteriography procedures. The results indicate that the array of lead beam-stops produces significant errors in estimating scatter-glare intensity. This is primarily due to the fact that contrast material injection significantly changes scatter-glare intensity. The scatter- glare intensity was changed by up to 19% and 88% during coronary arteriography and ventriculography, respectively. In conclusion, contrast material injection significantly changes the scatter-glare intensity during coronary arteriography and ventriculography procedures. Therefore, convolution-filtering techniques are more suited for cardiac imaging, where scatter- glare intensity significantly changes during image acquisition.

Proceedings Article | 1 May 1994 Paper

Geometric instability of ultrafast computed tomographic coronary calcium scores due to gray-scale nonuniformities

Herrick Wun, Robert Detrano, Xingping Kang, Paiboon Mahaisavariya, Sharon Nickerson, Sabee Molloi

Proceedings Volume 2168, (1994) https://doi.org/10.1117/12.174423

KEYWORDS: Calcium, Arteries, Ultrafast phenomena, Computed tomography, Blood, Heart, Tomography, Scanners, Analytical research, Chlorine

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Proceedings Article | 1 May 1994 Paper

Absolute volumetric blood flow quantification in rabbit brain using digital subtraction angiography

Atila Ersahin, Sabee Molloi, James Hicks, Yao-Jin Qian

Proceedings Volume 2168, (1994) https://doi.org/10.1117/12.174400

KEYWORDS: Blood circulation, Angiography, Arteries, Calibration, Image segmentation, Iodine, Staring arrays, Brain, Blood, Animal model studies

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Proceedings Article | 1 May 1994 Paper

Scatter and veiling glare corrections for quantitative digital subtraction angiography

Atila Ersahin, Sabee Molloi, Yao-Jin Qian

Proceedings Volume 2163, (1994) https://doi.org/10.1117/12.174253

KEYWORDS: X-rays, Lead, Convolution, Animal model studies, Point spread functions, Signal detection, Error analysis, X-ray imaging, Angiography, Physics

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