Publications by authors named "Inki Hong"

9 Publications

  • Page 1 of 1

Fabrication of Flexible pH-Responsive Agarose/Succinoglycan Hydrogels for Controlled Drug Release.

Polymers (Basel) 2021 Jun 22;13(13). Epub 2021 Jun 22.

Center for Biotechnology Research in UBITA (CBRU), Department of Bioscience and Biotechnology, Konkuk University, Seoul 05029, Korea.

Agarose/succinoglycan hydrogels were prepared as pH-responsive drug delivery systems with significantly improved flexibility, thermostability, and porosity compared to agarose gels alone. Agarose/succinoglycan hydrogels were made using agarose and succinoglycan, a polysaccharide directly isolated from . Mechanical and physical properties of agarose/succinoglycan hydrogels were investigated using various instrumental methods such as rheological measurements, attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopic analysis, X-ray diffraction (XRD), and field-emission scanning electron microscopy (FE-SEM). The results showed that the agarose/succinoglycan hydrogels became flexible and stable network gels with an improved swelling pattern in basic solution compared to the hard and brittle agarose gel alone. In addition, these hydrogels showed a pH-responsive delivery of ciprofloxacin (CPFX), with a cumulative release of ~41% within 35 h at pH 1.2 and complete release at pH 7.4. Agarose/succinoglycan hydrogels also proved to be non-toxic as a result of the cell cytotoxicity test, suggesting that these hydrogels would be a potential natural biomaterial for biomedical applications such as various drug delivery system and cell culture scaffolds.
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http://dx.doi.org/10.3390/polym13132049DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8272162PMC
June 2021

Impact of respiratory motion correction on lesion visibility and quantification in thoracic PET/MR imaging.

PLoS One 2020 4;15(6):e0233209. Epub 2020 Jun 4.

Erwin L. Hahn Institute for Magnetic Resonance Imaging, University of Duisburg Essen, Essen, Germany.

The impact of a method for MR-based respiratory motion correction of PET data on lesion visibility and quantification in patients with oncologic findings in the lung was evaluated. Twenty patients with one or more lesions in the lung were included. Hybrid imaging was performed on an integrated PET/MR system using 18F-FDG as radiotracer. The standard thoracic imaging protocol was extended by a free-breathing self-gated acquisition of MR data for motion modelling. PET data was acquired simultaneously in list-mode for 5-10 mins. One experienced radiologist and one experienced nuclear medicine specialist evaluated and compared the post-processed data in consensus regarding lesion visibility (scores 1-4, 4 being best), image noise levels (scores 1-3, 3 being lowest noise), SUVmean and SUVmax. Motion-corrected (MoCo) images were additionally compared with gated images. Non-motion-corrected free-breathing data served as standard of reference in this study. Motion correction generally improved lesion visibility (3.19 ± 0.63) and noise ratings (2.95 ± 0.22) compared to uncorrected (2.81 ± 0.66 and 2.95 ± 0.22, respectively) or gated PET data (2.47 ± 0.93 and 1.30 ± 0.47, respectively). Furthermore, SUVs (mean and max) were compared for all methods to estimate their respective impact on the quantification. Deviations of SUVmax were smallest between the uncorrected and the MoCo lesion data (average increase of 9.1% of MoCo SUVs), while SUVmean agreed best for gated and MoCo reconstructions (MoCo SUVs increased by 1.2%). The studied method for MR-based respiratory motion correction of PET data combines increased lesion sharpness and improved lesion activity quantification with high signal-to-noise ratio in a clinical setting. In particular, the detection of small lesions in moving organs such as the lung and liver may thus be facilitated. These advantages justify the extension of the PET/MR imaging protocol by 5-10 minutes for motion correction.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0233209PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7272064PMC
August 2020

Comparison of two elastic motion correction approaches for whole-body PET/CT: motion deblurring vs gate-to-gate motion correction.

EJNMMI Phys 2020 Mar 30;7(1):19. Epub 2020 Mar 30.

European Institute for Molecular Imaging, University of Münster, Waldeyerstr. 15, Münster, 48149, Germany.

Background: Respiratory motion in PET/CT leads to well-known image degrading effects commonly compensated using elastic motion correction approaches. Gate-to-gate motion correction techniques are promising tools for improving clinical PET data but suffer from relatively long reconstruction times. In this study, the performance of a fast elastic motion compensation approach based on motion deblurring (DEB-MC) was evaluated on patient and phantom data and compared to an EM-based fully 3D gate-to-gate motion correction method (G2G-MC) which was considered the gold standard.

Methods: Twenty-eight patients were included in this study with suspected or confirmed malignancies in the thorax or abdomen. All patients underwent whole-body [F]FDG PET/CT examinations applying hardware-based respiratory gating. In addition, a dynamic anthropomorphic thorax phantom was studied with PET/CT simulating tumour motion under controlled but realistic conditions. PET signal recovery values were calculated from phantom scans by comparing lesion activities after motion correction to static ground truth data. Differences in standardized uptake values (SUV) and metabolic volume (MV) between both reconstruction methods as well as between motion-corrected (MC) and non motion-corrected (NOMC) results were statistically analyzed using a Wilcoxon signed-rank test.

Results: Phantom data analysis showed high lesion recovery values of 91% (2 cm motion) and 98% (1 cm) for G2G-MC and 83% (2 cm) and 90% (1 cm) for DEB-MC. The statistical analysis of patient data found significant differences between NOMC and MC reconstructions for SUV , SUV , MV, and contrast-to-noise ratio (CNR) for both reconstruction algorithms. Furthermore, both methods showed similar increases of 11-12% in SUV and SUV after MC. The statistical analysis of the MC/NOMC ratio found no significant differences between the methods.

Conclusion: Both motion correction techniques deliver comparable improvements of SUV , SUV , and CNR after MC on clinical and phantom data. The fast elastic motion compensation technique DEB-MC may thereby be a valuable alternative to state-of-the art motion correction techniques.
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http://dx.doi.org/10.1186/s40658-020-0285-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7105551PMC
March 2020

Coronary artery 18F-NaF PET analysis with the use of an elastic motion correction software.

J Nucl Cardiol 2020 06 25;27(3):952-961. Epub 2019 Jan 25.

Cardiology Department, Royal Perth Hospital, 197 Wellington St, Perth, WA, 6000, Australia.

Introduction: 18F-Sodium Fluoride Positron Emission Tomography (18F-NaF PET) is a novel molecular imaging modality with promise for use as a risk stratification tool in cardiovascular disease. There are limitations in the analysis of small and rapidly moving coronary arteries using traditional PET technology. We aimed to validate the use of a motion correction algorithm (eMoco) on coronary 18F-NaF PET outcome parameters.

Methods: Patients admitted with an acute coronary syndrome underwent 18F-NaF PET and computed tomography coronary angiography. 18F-NaF PET data were analyzed using a diastolic reconstruction, an ungated reconstruction and the eMoco reconstruction.

Results: Twenty patients underwent 18F-NaF PET imaging and 17 patients had at least one positive lesion that could be used to compare PET reconstruction datasets. eMoco improved noise (the coefficient of variation of the blood pool radiotracer activity) compared to the diastolic dataset (0.09 [0.07 to 0.12] vs 0.14[0.11 to 0.17], p < .001) and marginally improved coronary lesion maximum tissue-to-background ratios compared to the ungated dataset (1.33 [1.05 to 1.48]vs 1.29 [1.04 to 1.40], p = .011).

Conclusion: In this pilot dataset, the eMoco reconstruction algorithm for motion correction appears to have potential in improving coronary analysis of 18F-NaF PET by reducing noise and increasing maximum counts. Further testing in a larger patient dataset is warranted.
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http://dx.doi.org/10.1007/s12350-018-01587-7DOI Listing
June 2020

Ascending Aortic Endoballoon Occlusion Feasible Despite Moderately Enlarged Aorta to Facilitate Robotic Mitral Valve Surgery.

Innovations (Phila) 2016 Sep/Oct;11(5):355-359

From the *Temple University School of Medicine, Philadelphia, PA USA; †Division of Cardiovascular Surgery, Temple University School of Medicine, Philadelphia, PA USA; ‡Department of Surgery, Dwight D. Eisenhower Army Medical Center, Augusta, GA USA; and §Department of Cardiothoracic Surgery, Weill Cornell School of Medicine, New York Presbyterian Hospital, New York, NY USA.

Objective: Aortic occlusion with an endoballoon is a well-established technique to facilitate robotic and minimally invasive mitral valve surgery. Use of the endoballoon has several relative contraindications including ascending aortic dilatation greater than 38 mm in size. We sought to review our experience using the endoballoon in cases of totally endoscopic mitral valve surgery with aortic diameters greater than 38 mm.

Methods: A retrospective review of our single-site database was conducted to identify patients undergoing totally endoscopic mitral valve surgery by a single surgeon using an endoballoon and who had ascending aortic dilation. We defined aortic dilation as greater than 38 mm. Computed tomography was done preoperatively on all patients to evaluate the aortic anatomy as well as iliofemoral access vessels. Femoral artery cannulation was done in a standardized fashion to advance and position the endoballoon, to occlude the ascending aorta, and to deliver cardioplegia.

Results: From October 2011 through June 2015, 196 patients underwent totally endoscopic mitral valve surgery using an endoballoon at our institution. Twenty-two patients (11.2%) had ascending aortic diameters greater than 38 mm (range, 38.1-46.6 mm; mean, 40.5 ± 2.5 mm). In these cases, there were no instances of aortic dissection or other injury due to balloon rupture, balloon migration, device movement leading to loss of occlusion, or inability to complete planned surgery due to occlusion failure.

Conclusions: Our experience suggests that it is possible to successfully use endoaortic balloon occlusion in patients with ascending aortic dilation with proper preoperative imaging and planning.
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http://dx.doi.org/10.1097/IMI.0000000000000291DOI Listing
May 2017

Motion correction strategies for integrated PET/MR.

J Nucl Med 2015 Feb 8;56(2):261-9. Epub 2015 Jan 8.

Department of Nuclear Medicine, Technische Universität München, Munich, Germany.

Unlabelled: Integrated whole-body PET/MR facilitates the implementation of a broad variety of respiratory motion correction strategies, taking advantage of the strengths of both modalities. The goal of this study was the quantitative evaluation with clinical data of different MR- and PET-data-based motion correction strategies for integrated PET/MR.

Methods: The PET and MR data of 20 patients were simultaneously acquired for 10 min on an integrated PET/MR system after administration of (18)F-FDG or (68)Ga-DOTANOC. Respiratory traces recorded with a bellows were compared against MR self-gating signals and signals extracted from PET raw data with the sensitivity method, by applying principal component analysis (PCA) or Laplacian eigenmaps and by using a novel variation combining the former and either of the latter two. Gated sinograms and MR images were generated accordingly, followed by image registration to derive MR motion models. Corrected PET images were reconstructed by incorporating this information into the reconstruction. An optical flow algorithm was applied for PET-based motion correction. Gating and motion correction were evaluated by quantitative analysis of apparent tracer uptake, lesion volume, displacement, contrast, and signal-to-noise ratio.

Results: The correlation between bellows- and MR-based signals was 0.63 ± 0.19, and that between MR and the sensitivity method was 0.52 ± 0.26. Depending on the PET raw-data compression, the average correlation between MR and PCA ranged from 0.25 ± 0.30 to 0.58 ± 0.33, and the range was 0.25 ± 0.30 to 0.42 ± 0.34 if Laplacian eigenmaps were applied. By combining the sensitivity method and PCA or Laplacian eigenmaps, the maximum average correlation to MR could be increased to 0.74 ± 0.21 and 0.70 ± 0.19, respectively. The selection of the best PET-based signal for each patient yielded an average correlation of 0.80 ± 0.13 with MR. Using the best PET-based respiratory signal for gating, mean tracer uptake increased by 17 ± 19% for gating, 13 ± 10% for MR-based motion correction, and 18 ± 15% for PET-based motion correction, compared with the static images. Lesion volumes were 76 ± 31%, 83 ± 18%, and 74 ± 22% of the sizes in the static images for gating, MR-based motion correction, and PET-based motion correction, respectively.

Conclusion: Respiratory traces extracted from MR and PET data are comparable to those based on external sensors. The proposed PET-driven gating method improved respiratory signals and overall stability. Consistent results from MR- and PET-based correction methods enable more flexible PET/MR scan protocols while achieving higher PET image quality.
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http://dx.doi.org/10.2967/jnumed.114.146787DOI Listing
February 2015

Complementary frame reconstruction: a low-biased dynamic PET technique for low count density data in projection space.

Phys Med Biol 2014 Sep 28;59(18):5441-55. Epub 2014 Aug 28.

Siemens Medical Solutions, 810 Innovation Drive, Knoxville, TN 37919, USA.

A new data handling method is presented for improving the image noise distribution and reducing bias when reconstructing very short frames from low count dynamic PET acquisition. The new method termed 'Complementary Frame Reconstruction' (CFR) involves the indirect formation of a count-limited emission image in a short frame through subtraction of two frames with longer acquisition time, where the short time frame data is excluded from the second long frame data before the reconstruction. This approach can be regarded as an alternative to the AML algorithm recently proposed by Nuyts et al, as a method to reduce the bias for the maximum likelihood expectation maximization (MLEM) reconstruction of count limited data. CFR uses long scan emission data to stabilize the reconstruction and avoids modification of algorithms such as MLEM. The subtraction between two long frame images, naturally allows negative voxel values and significantly reduces bias introduced in the final image. Simulations based on phantom and clinical data were used to evaluate the accuracy of the reconstructed images to represent the true activity distribution. Applicability to determine the arterial input function in human and small animal studies is also explored. In situations with limited count rate, e.g. pediatric applications, gated abdominal, cardiac studies, etc., or when using limited doses of short-lived isotopes such as 15O-water, the proposed method will likely be preferred over independent frame reconstruction to address bias and noise issues.
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http://dx.doi.org/10.1088/0031-9155/59/18/5441DOI Listing
September 2014

LSO background radiation as a transmission source using time of flight.

Phys Med Biol 2014 Sep 28;59(18):5483-500. Epub 2014 Aug 28.

Siemens Molecular Imaging, 810 Innovation Dr, Knoxville, TN 37932, USA.

LSO scintillators (Lu2Sio5:Ce) have a background radiation which originates from the isotope Lu-176 that is present in natural occurring lutetium. The decay that occurs in this isotope is a beta decay that is in coincidence with cascade gamma emissions with energies of 307,202 and 88 keV. The coincidental nature of the beta decay with the gamma emissions allow for separation of emission data originating from a positron annihilation event from transmission type data from the Lu-176 beta decay. By using the time of flight information, and information of the chord length between two LSO pixels in coincidence as a result of a beta emission and emitted gamma, a second time window can be set to observe transmission events simultaneously to emission events. Using the time when the PET scanner is not actively acquiring positron emission data, a continuous blank can be acquired and used to reconstruct a transmission image. With this blank and the measured transmission data, a transmission image can be reconstructed. This reconstructed transmission image can be used to perform emission data corrections such as attenuation correction and scatter corrections or starting images for algorithms that estimate emission and attenuation simultaneously. It is observed that the flux of the background activity is high enough to create useful transmission images with an acquisition time of 10 min.
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http://dx.doi.org/10.1088/0031-9155/59/18/5483DOI Listing
September 2014

Reconstruction of scattered and unscattered PET coincidences using TOF and energy information.

Phys Med Biol 2012 Aug 17;57(15):N307-17. Epub 2012 Jul 17.

Siemens Healthcare, Molecular Imaging, 810 Innovation Drive, Knoxville, TN 37919, USA.

In positron emission tomography (PET), a typical reconstruction algorithm relies on a method to estimate and subtract the scatter from the net trues coincidences. The remaining unscattered coincidences are then used to reconstruct an image of the original activity distribution. The introduction of time-of-flight (TOF) PET opens the possibility to change this scheme, and use the spatial information carried by the scattered events for the reconstruction. The combined knowledge of TOF difference and detected photon energy provides spatial information on the position of the source even after single scattering, and can be used for the reconstruction of scattered photons, using a 'scatter back projector' in addition to the conventional 'trues back projector'. In the scatter back projector, the scattering angle is derived from the energy of the scattered photon through Compton kinematics, and this identifies a set of possible scattering trajectories, or 'broken' line of response (LOR). The TOF information localizes the position of the source along the set of broken LOR. The advantages of this proposed method are twofold: including the spatial information about the origin of the scattered pairs could improve the image quality particularly in low count datasets; and the threshold of the energy window can be lowered to include more scatter, thus increasing sensitivity. In this work, this novel approach to scatter in PET is introduced, different implementations are discussed, and the performance of a preliminary version of the 'scatter back projector' is presented.
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http://dx.doi.org/10.1088/0031-9155/57/15/N307DOI Listing
August 2012
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