O. Nalcioglu - Academia.edu (original) (raw)
Papers by O. Nalcioglu
-72.6%, -36.2%, 78.4%, and 69.2% (p = 0.003, p = 0.097, p = 0.073, and p = 0.180 in Figure 2), wh... more -72.6%, -36.2%, 78.4%, and 69.2% (p = 0.003, p = 0.097, p = 0.073, and p = 0.180 in Figure 2), while the mean percentage change in lesion size in FU-1 study was -9.7% (+8.8% ~ -32.5%) (p = 0.042). There were no significant correlation between change in tCho in FU-1 and the change in lesion size in FU-2 (r 2 = 0.06, p = 0.536). After completing the F/U-2 study, 3 (27%) of 11 patients did have positive tCho based on the criterion (i.e., tCho CRLB < 30%). The mean percentage change tCho, H2O, CH2, and CH3 after FU-2 study was -96.6%, 76.9%, 119.6%, and 119.5% (p = 0.004, p = 0.044, p = 0.008, and p = 0.005 in Figure 2), while the mean percentage change in lesion size in FU-2 study was 56.7% (-22.7% ~ -100%) (p = 0.007). Discussion The measured tCho levels at the baseline from 9 spectra were in a range of 0.19 – 5.29 (mean ± SD, 1.94 ± 1.76 mmol/kg). Our study showed the reduction in tCho at the first and second follow-up was significantly higher compared with the reduction in the tumor size (mean percentage change -72.6% vs. -9.7%, p < 0.0001; -96.6% vs. -56.7%, p < 0.003). The result demonstrates that the metabolic changes were greater than the tumor size changes, suggesting that they might have occurred before gross morphological changes. An early reduction of tCho can be interpreted as reflecting the inhibition of cellular proliferation and the cytotoxic effect of chemotherapy. In addition, the reduction in H2O and H2O/CH3 were also significantly higher than the reduction in tumor size at FU-1 (-36.2% vs. -9.7%, p = 0.028; -43.2% vs. -9.7%, p = 0.033), but not significant at FU-2 ((-76.9% vs. -61.1%, p = 0.125; -82.3% vs. -61.1%, p = 0.120). Our finding suggests that a greater reduction in tCho and H2O/CH3 at the FU-1 may help to predict a final (or, pathological) complete response. Therefore, we demonstrates that in vivo quantitative 1 H-MRS without water–fat
Medical Imaging II, 1988
The determination of percent stenosis of coronary arteries is an important task in medicine. In t... more The determination of percent stenosis of coronary arteries is an important task in medicine. In this paper we discuss three different algorithms which can be used in conjunction with videodensitometry to measure this quantity. These algorithms may be used in subtracting the background under a vessel segment thus eliminating the need for a preinjection mask. Mathematical details of the algorithms and experimental results are presented. 1. INTRODUCTION Recent advances in the digital x-ray video imaging systems has made the visualization and measurement of small amounts of radiopaque contrast agents within the vasculature a reality. The components of a typical digital radiographic system are the x-ray generator, x-ray tube, intensifier (II), television (TV) camera, video digitizer, display and recording devices. Two general classes of measurements one can perform on the digital video imaging are: (a) geometrical8 and (b) videodensitometric quantification7,5,6. Here, we will only be concerned with the latter. Videodensitometric measurements) are based on the linear relationship between the intensity of the video signal and the thickness of the tissue transversed by x-rays causing that signal. Many physical problems, some of which are intrinsic to such imaging systems and others due to the nature of interaction of x-rays with an object, usually cause a deviation from this desired linear relationship4. Thus, it is quite essential to determine the response of the imaging chain prior to making measurements on images obtained with such systems. In this paper, we will focus on the videodensitometric measurement of coronary stenosis. The most common technique used for this purpose is the "mask subtraction" 3. In this technique, a mask image of the patient is taken prior to the injection of iodinated contrast material into the coronary vessels. Then, a pixel by pixel subtraction of the logarithmically amplified mask image from the post-injection image results in an image which "ideally" has all the noniodinated parts of the object cancelled. The net iodine signal intensity is linearly related to the thickness of the vessel containing it. Thus, a correct measurement requires, among other things, a total cancellation of the noniodinated overlaying structures. If the patient moves in between the time mask and post-injection images are acquired, then the difference images may be degraded due to motion artifacts. The measurement of coronary stenosis using such images would give rise to different degrees of error depending on the magnitude and location of motion artifacts. Since the physiological motions which occur in a patient are not simple translational motion, one can not remedy the situation by simply shifting the mask to obtain an acceptable registration with the iodinated image. Attempts to alleviate this problem by means of rubber sheet algorithms have proven to be difficult and at best, approximate. In this paper, we discuss several different algorithms to estimate the background under the iodinated vessel. Since the background is derived from the iodinated images, one does not have to use any preinjection mask images. Section 2 covers the methods. The results are presented in Section 3. The conclusions are given in Section 4. 2. METHODS 2.1 Basic Formalism The expression for a two dimensional video image Q(x,y) obtained with a TV based x-ray imaging system is given by Kruger2,
Biomedical Optics and 3-D Imaging, 2012
ABSTRACT We have introduced a NIR swept source based diffuse optical tomography (DOT) system. We ... more ABSTRACT We have introduced a NIR swept source based diffuse optical tomography (DOT) system. We also demonstrate the capabilities of the NIR swept laser for multi-spectral DOT application with a turbid gelatin phantom measurement.
Journal of Computer Assisted Tomography, 1978
Technology in cancer research & treatment, 2006
A significant increase in electrical conductivity of neoplasticities compared to healthy tissues ... more A significant increase in electrical conductivity of neoplasticities compared to healthy tissues and benign formations has been reported in several studies. We previously reported preliminary results with MR based Electrical Impedance Tomography (MREIT) on several phantoms and a single animal. In the presented study, we applied the technique on ten tumor-bearing rats and collected MREIT images to investigate the potential of MREIT for characterizing malignant tumors. Results show that the tumors had significantly higher mean conductivity compared to the mean of conductivity in the rest of the body. Although heterogeneity of conductivity was observed in the tumor, the mean was still higher than the background.
Medical Imaging II, 1988
A new technique for generating spatially resolved pressure-gradient images of flow fields is intr... more A new technique for generating spatially resolved pressure-gradient images of flow fields is introduced.
Lettere Al Nuovo Cimento Series 2, 1976
Physical Review C, 1970
The bootstrap theory is applied to the case of pairing vibrations; an approximation used by Dang ... more The bootstrap theory is applied to the case of pairing vibrations; an approximation used by Dang and Klein in their treatment of pairing is shown to be consistent with the bootstrap theory. A modified Tamm-Dancoff approximation is described. The numerical results for Ni58,60,62 are compared with the exact solutions and with the results of Dang and Klein.
Medical Imaging II, 1988
ABSTRACT
Physics in Medicine and Biology, 1984
In recent years the contrast ratio (CR) has played an important role in the quantitation of imagi... more In recent years the contrast ratio (CR) has played an important role in the quantitation of imaging performance of X-ray image intensifiers. In practice, one uses either a lead disc or strip for measurement of contrast ratios. A theoretical relationship relating contrast ratios measured by both disc and strip techniques is discussed and experimental results are presented. The theoretical analysis uses the point spread function model to describe veiling glare for an image intensifier. It has been shown that one can predict strip contrast ratios after a determination of the veiling glare point spread function from a measurement of disc contrast ratios.
Physics in Medicine and Biology, 2007
Fluorescence diffuse optical tomography (FT) is an emerging molecular imaging technique that can ... more Fluorescence diffuse optical tomography (FT) is an emerging molecular imaging technique that can spatially resolve both fluorophore concentration and lifetime parameters. In this study, we investigate the performance of a frequency-domain FT system for small inclusions that are embedded in a heterogeneous background. The results demonstrate that functional and structural a priori information is crucial to be able to recover both parameters with high accuracy. The functional a priori information is defined by the absorption and scattering maps at both excitation and emission wavelengths. Similarly, the boundaries of the small inclusion and different regions in the background are utilized as the structural a priori information. Without a priori information, the fluorophore concentration of a 5 mm inclusion in a 40 mm medium is recovered with 50% error, while the lifetime cannot be recovered at all. On the other hand, when both functional and structural information are available, the true lifetime can be recovered and the fluorophore concentration can be estimated only with 5% error. This study shows that a hybrid system that can acquire diffuse optical absorption tomography (DOT), FT and anatomical images in the same setting is essential to be able to recover the fluorophore concentration and lifetime accurately in vivo.
Neurology, 1991
The brains of patients with Alzheimer&amp;#39;s disease (AD) invariably exhibit neuropath... more The brains of patients with Alzheimer&amp;#39;s disease (AD) invariably exhibit neuropathology in the hippocampus and entorhinal cortex when examined postmortem. Magnetic resonance imaging (MRI) offers a noninvasive, high-resolution method for quantifying volumetric changes in the AD brain antemortem. Eight patients diagnosed with probable AD and 7 age-matched controls had MRI scans and were tested on a battery of cognitive and olfactory tests. The hippocampus and entorhinal cortex (parahippocampal gyrus) showed significant atrophy, with over 40% reduction in size. Areas of the brain that are not highly involved in the degenerative state of AD, such as the striatum, did not show significant volumetric changes. Hippocampal and parahippocampal gyrus volumes had the highest correlation with scores on the Mini-Mental State Examination (r = 0.89), with lower correlations for a smell identification test (r = 0.65), odor match-to-sample test (r = 0.72), and a visual match-to-sample test (r = 0.26).
Neurological Research, 2001
Behavioral studies, motivated by columnar cortical model predictions, have given evidence for mus... more Behavioral studies, motivated by columnar cortical model predictions, have given evidence for music causally enhancing spatial-temporal reasoning. A wide range of behavioral experiments showed that listening to a Mozart Sonata (K.448) gave subsequent enhancements. An EEG coherence study gave evidence for a carryover from that Mozart Sonata listening condition to the subsequent spatial-temporal task in speci c cortical regions. Here we present fMRI studies comparing cortical blood ow activation by the Mozart Sonata vs. other music. In addition to expected temporal cortex activation, we report dramatic statistically signi cant differences in activation by the Mozart Sonata (in comparison to Beethoven's Fur Elise and 19 30s piano music) in dorsolateral pre-frontal cortex, occipital cortex and cerebellum, all expected to be important for spatial-temporal reasoning. It would be of great interest to explicitly test this expectation. We propose an fMRI study comparing (subject by subject) brain areas activated in music listening conditions and in spatial-temporal tasks.
Magnetic Resonance in Medicine, 1989
A new method for spatially resolved NMR flow measurements, named differential flow imaging (DFI),... more A new method for spatially resolved NMR flow measurements, named differential flow imaging (DFI), is introduced and experimentally verified. The DFI technique is based on the fact that flow velocity in any direction may cause a pixel position shift in the phase‐encoding direction of a 2DFT NMR image. In this method two flow‐influenced magnitude images are obtained by properly encoding and/or compensating the flow velocity. A spatial map of the desired component of the flow velocity can consequently be calculated from these two images. Since the DFI technique uses only the magnitude information of the complex images, it is not sensitive to systematic phase errors in contrast to other methods which are based on the phase measurements. On the other hand, the DFI technique can be combined with the phase measurement methods to perform multidimensional flow measurements in a shorter data acquisition time when the phase errors are small or corrected. © 1989 Academic Press, Inc.
Journal of Magnetic Resonance Imaging, 2003
PurposeTo investigate the association between parameters obtained from dynamic contrast enhanced ... more PurposeTo investigate the association between parameters obtained from dynamic contrast enhanced MRI (DCE‐MRI) of breast cancer using different analysis approaches, as well as their correlation with angiogenesis biomarkers (vascular endothelial growth factor and vessel density).Materials and MethodsDCE‐MRI results were obtained from 105 patients with breast cancer (108 lesions). Three analysis methods were applied: 1) whole tumor analysis, 2) regional hot‐spot analysis, and 3) intratumor pixel‐by‐pixel analysis. Early enhancement intensities and fitted pharmacokinetic parameters were studied. Paraffin blocks of 71 surgically resected specimens were analyzed by immunohistochemical staining to measure microvessel counts (with CD31) and vascular endothelial growth factor (VEGF) expression levels.ResultsMRI parameters obtained from the three analysis methods showed significant correlations (P < 0.0001), but a substantial dispersion from the linear regression line was noted (r = 0.72–...
Investigative Radiology, 1991
IEEE Transactions on Medical Imaging, 1985
The conjugate gradient method incorporating the objectextent constraint is applied to image recon... more The conjugate gradient method incorporating the objectextent constraint is applied to image reconstruction of a three-dimensional object using an incomplete projection-data set. The missing information is recovered by constraining the solution with the knowledge of the outer boundary of the object-extent which may be a priori measured or known. The algorithm is derived from the least-squares criterion as an advanced version of conventional iterative reconstruction algorithms such as SIRT (Simultaneous Iterative Reconstruction Technique) and ILST (Iterative Least Squares Technique). In the case of reconstruction from noisy projection data, a method based on the minimum mean-square error criterion is also proposed. Computer simulated reconstruction images of a phantom using limited angle and number of views are presented. The result shows that the conjugate gradient method incorporating the object-extent constraining provides the fastest convergence and the least error.
Artificial Cells, Blood Substitutes, and Biotechnology, 1994
The purpose of this study was to confirm the relationship of T1 and T2 relaxation rate vs. pO2 in... more The purpose of this study was to confirm the relationship of T1 and T2 relaxation rate vs. pO2 in vivo of 19F MR signal measured from intracellular perflubron. Our work to date has demonstrated that 1/T2 is more sensitive to pO2 than 1/T1 in the in vitro environment. The advantage of 1/T2 vs. 1/T1 is the speed of measurement and sensitivity. Seven alternating T1 and T2 measurements were obtained during a continuous acquisition using the TTISS pulse sequence. An abscess model was used for the in vivo experiments where rabbits were infused with 5ml/kg Oxygent HT 10 days prior to scanning. The abscess model was used because it has been shown that perflubron accumulates in macrophages located in the abscess wall. This technique thus provided signal from the intracellular milieu. The results of this study proved that pO2 monitoring by measuring T2 of 19F is feasible and can be used in-lieu of the T1 measurement. Given that the T2 measurement is much more rapid than the T1 measurement and that T2 changes are more sensitive than T1 changes with alterations in pO2, T2 should prove to be practical and useful for monitoring transient rapid changes in pO2.
-72.6%, -36.2%, 78.4%, and 69.2% (p = 0.003, p = 0.097, p = 0.073, and p = 0.180 in Figure 2), wh... more -72.6%, -36.2%, 78.4%, and 69.2% (p = 0.003, p = 0.097, p = 0.073, and p = 0.180 in Figure 2), while the mean percentage change in lesion size in FU-1 study was -9.7% (+8.8% ~ -32.5%) (p = 0.042). There were no significant correlation between change in tCho in FU-1 and the change in lesion size in FU-2 (r 2 = 0.06, p = 0.536). After completing the F/U-2 study, 3 (27%) of 11 patients did have positive tCho based on the criterion (i.e., tCho CRLB < 30%). The mean percentage change tCho, H2O, CH2, and CH3 after FU-2 study was -96.6%, 76.9%, 119.6%, and 119.5% (p = 0.004, p = 0.044, p = 0.008, and p = 0.005 in Figure 2), while the mean percentage change in lesion size in FU-2 study was 56.7% (-22.7% ~ -100%) (p = 0.007). Discussion The measured tCho levels at the baseline from 9 spectra were in a range of 0.19 – 5.29 (mean ± SD, 1.94 ± 1.76 mmol/kg). Our study showed the reduction in tCho at the first and second follow-up was significantly higher compared with the reduction in the tumor size (mean percentage change -72.6% vs. -9.7%, p < 0.0001; -96.6% vs. -56.7%, p < 0.003). The result demonstrates that the metabolic changes were greater than the tumor size changes, suggesting that they might have occurred before gross morphological changes. An early reduction of tCho can be interpreted as reflecting the inhibition of cellular proliferation and the cytotoxic effect of chemotherapy. In addition, the reduction in H2O and H2O/CH3 were also significantly higher than the reduction in tumor size at FU-1 (-36.2% vs. -9.7%, p = 0.028; -43.2% vs. -9.7%, p = 0.033), but not significant at FU-2 ((-76.9% vs. -61.1%, p = 0.125; -82.3% vs. -61.1%, p = 0.120). Our finding suggests that a greater reduction in tCho and H2O/CH3 at the FU-1 may help to predict a final (or, pathological) complete response. Therefore, we demonstrates that in vivo quantitative 1 H-MRS without water–fat
Medical Imaging II, 1988
The determination of percent stenosis of coronary arteries is an important task in medicine. In t... more The determination of percent stenosis of coronary arteries is an important task in medicine. In this paper we discuss three different algorithms which can be used in conjunction with videodensitometry to measure this quantity. These algorithms may be used in subtracting the background under a vessel segment thus eliminating the need for a preinjection mask. Mathematical details of the algorithms and experimental results are presented. 1. INTRODUCTION Recent advances in the digital x-ray video imaging systems has made the visualization and measurement of small amounts of radiopaque contrast agents within the vasculature a reality. The components of a typical digital radiographic system are the x-ray generator, x-ray tube, intensifier (II), television (TV) camera, video digitizer, display and recording devices. Two general classes of measurements one can perform on the digital video imaging are: (a) geometrical8 and (b) videodensitometric quantification7,5,6. Here, we will only be concerned with the latter. Videodensitometric measurements) are based on the linear relationship between the intensity of the video signal and the thickness of the tissue transversed by x-rays causing that signal. Many physical problems, some of which are intrinsic to such imaging systems and others due to the nature of interaction of x-rays with an object, usually cause a deviation from this desired linear relationship4. Thus, it is quite essential to determine the response of the imaging chain prior to making measurements on images obtained with such systems. In this paper, we will focus on the videodensitometric measurement of coronary stenosis. The most common technique used for this purpose is the "mask subtraction" 3. In this technique, a mask image of the patient is taken prior to the injection of iodinated contrast material into the coronary vessels. Then, a pixel by pixel subtraction of the logarithmically amplified mask image from the post-injection image results in an image which "ideally" has all the noniodinated parts of the object cancelled. The net iodine signal intensity is linearly related to the thickness of the vessel containing it. Thus, a correct measurement requires, among other things, a total cancellation of the noniodinated overlaying structures. If the patient moves in between the time mask and post-injection images are acquired, then the difference images may be degraded due to motion artifacts. The measurement of coronary stenosis using such images would give rise to different degrees of error depending on the magnitude and location of motion artifacts. Since the physiological motions which occur in a patient are not simple translational motion, one can not remedy the situation by simply shifting the mask to obtain an acceptable registration with the iodinated image. Attempts to alleviate this problem by means of rubber sheet algorithms have proven to be difficult and at best, approximate. In this paper, we discuss several different algorithms to estimate the background under the iodinated vessel. Since the background is derived from the iodinated images, one does not have to use any preinjection mask images. Section 2 covers the methods. The results are presented in Section 3. The conclusions are given in Section 4. 2. METHODS 2.1 Basic Formalism The expression for a two dimensional video image Q(x,y) obtained with a TV based x-ray imaging system is given by Kruger2,
Biomedical Optics and 3-D Imaging, 2012
ABSTRACT We have introduced a NIR swept source based diffuse optical tomography (DOT) system. We ... more ABSTRACT We have introduced a NIR swept source based diffuse optical tomography (DOT) system. We also demonstrate the capabilities of the NIR swept laser for multi-spectral DOT application with a turbid gelatin phantom measurement.
Journal of Computer Assisted Tomography, 1978
Technology in cancer research & treatment, 2006
A significant increase in electrical conductivity of neoplasticities compared to healthy tissues ... more A significant increase in electrical conductivity of neoplasticities compared to healthy tissues and benign formations has been reported in several studies. We previously reported preliminary results with MR based Electrical Impedance Tomography (MREIT) on several phantoms and a single animal. In the presented study, we applied the technique on ten tumor-bearing rats and collected MREIT images to investigate the potential of MREIT for characterizing malignant tumors. Results show that the tumors had significantly higher mean conductivity compared to the mean of conductivity in the rest of the body. Although heterogeneity of conductivity was observed in the tumor, the mean was still higher than the background.
Medical Imaging II, 1988
A new technique for generating spatially resolved pressure-gradient images of flow fields is intr... more A new technique for generating spatially resolved pressure-gradient images of flow fields is introduced.
Lettere Al Nuovo Cimento Series 2, 1976
Physical Review C, 1970
The bootstrap theory is applied to the case of pairing vibrations; an approximation used by Dang ... more The bootstrap theory is applied to the case of pairing vibrations; an approximation used by Dang and Klein in their treatment of pairing is shown to be consistent with the bootstrap theory. A modified Tamm-Dancoff approximation is described. The numerical results for Ni58,60,62 are compared with the exact solutions and with the results of Dang and Klein.
Medical Imaging II, 1988
ABSTRACT
Physics in Medicine and Biology, 1984
In recent years the contrast ratio (CR) has played an important role in the quantitation of imagi... more In recent years the contrast ratio (CR) has played an important role in the quantitation of imaging performance of X-ray image intensifiers. In practice, one uses either a lead disc or strip for measurement of contrast ratios. A theoretical relationship relating contrast ratios measured by both disc and strip techniques is discussed and experimental results are presented. The theoretical analysis uses the point spread function model to describe veiling glare for an image intensifier. It has been shown that one can predict strip contrast ratios after a determination of the veiling glare point spread function from a measurement of disc contrast ratios.
Physics in Medicine and Biology, 2007
Fluorescence diffuse optical tomography (FT) is an emerging molecular imaging technique that can ... more Fluorescence diffuse optical tomography (FT) is an emerging molecular imaging technique that can spatially resolve both fluorophore concentration and lifetime parameters. In this study, we investigate the performance of a frequency-domain FT system for small inclusions that are embedded in a heterogeneous background. The results demonstrate that functional and structural a priori information is crucial to be able to recover both parameters with high accuracy. The functional a priori information is defined by the absorption and scattering maps at both excitation and emission wavelengths. Similarly, the boundaries of the small inclusion and different regions in the background are utilized as the structural a priori information. Without a priori information, the fluorophore concentration of a 5 mm inclusion in a 40 mm medium is recovered with 50% error, while the lifetime cannot be recovered at all. On the other hand, when both functional and structural information are available, the true lifetime can be recovered and the fluorophore concentration can be estimated only with 5% error. This study shows that a hybrid system that can acquire diffuse optical absorption tomography (DOT), FT and anatomical images in the same setting is essential to be able to recover the fluorophore concentration and lifetime accurately in vivo.
Neurology, 1991
The brains of patients with Alzheimer&amp;#39;s disease (AD) invariably exhibit neuropath... more The brains of patients with Alzheimer&amp;#39;s disease (AD) invariably exhibit neuropathology in the hippocampus and entorhinal cortex when examined postmortem. Magnetic resonance imaging (MRI) offers a noninvasive, high-resolution method for quantifying volumetric changes in the AD brain antemortem. Eight patients diagnosed with probable AD and 7 age-matched controls had MRI scans and were tested on a battery of cognitive and olfactory tests. The hippocampus and entorhinal cortex (parahippocampal gyrus) showed significant atrophy, with over 40% reduction in size. Areas of the brain that are not highly involved in the degenerative state of AD, such as the striatum, did not show significant volumetric changes. Hippocampal and parahippocampal gyrus volumes had the highest correlation with scores on the Mini-Mental State Examination (r = 0.89), with lower correlations for a smell identification test (r = 0.65), odor match-to-sample test (r = 0.72), and a visual match-to-sample test (r = 0.26).
Neurological Research, 2001
Behavioral studies, motivated by columnar cortical model predictions, have given evidence for mus... more Behavioral studies, motivated by columnar cortical model predictions, have given evidence for music causally enhancing spatial-temporal reasoning. A wide range of behavioral experiments showed that listening to a Mozart Sonata (K.448) gave subsequent enhancements. An EEG coherence study gave evidence for a carryover from that Mozart Sonata listening condition to the subsequent spatial-temporal task in speci c cortical regions. Here we present fMRI studies comparing cortical blood ow activation by the Mozart Sonata vs. other music. In addition to expected temporal cortex activation, we report dramatic statistically signi cant differences in activation by the Mozart Sonata (in comparison to Beethoven's Fur Elise and 19 30s piano music) in dorsolateral pre-frontal cortex, occipital cortex and cerebellum, all expected to be important for spatial-temporal reasoning. It would be of great interest to explicitly test this expectation. We propose an fMRI study comparing (subject by subject) brain areas activated in music listening conditions and in spatial-temporal tasks.
Magnetic Resonance in Medicine, 1989
A new method for spatially resolved NMR flow measurements, named differential flow imaging (DFI),... more A new method for spatially resolved NMR flow measurements, named differential flow imaging (DFI), is introduced and experimentally verified. The DFI technique is based on the fact that flow velocity in any direction may cause a pixel position shift in the phase‐encoding direction of a 2DFT NMR image. In this method two flow‐influenced magnitude images are obtained by properly encoding and/or compensating the flow velocity. A spatial map of the desired component of the flow velocity can consequently be calculated from these two images. Since the DFI technique uses only the magnitude information of the complex images, it is not sensitive to systematic phase errors in contrast to other methods which are based on the phase measurements. On the other hand, the DFI technique can be combined with the phase measurement methods to perform multidimensional flow measurements in a shorter data acquisition time when the phase errors are small or corrected. © 1989 Academic Press, Inc.
Journal of Magnetic Resonance Imaging, 2003
PurposeTo investigate the association between parameters obtained from dynamic contrast enhanced ... more PurposeTo investigate the association between parameters obtained from dynamic contrast enhanced MRI (DCE‐MRI) of breast cancer using different analysis approaches, as well as their correlation with angiogenesis biomarkers (vascular endothelial growth factor and vessel density).Materials and MethodsDCE‐MRI results were obtained from 105 patients with breast cancer (108 lesions). Three analysis methods were applied: 1) whole tumor analysis, 2) regional hot‐spot analysis, and 3) intratumor pixel‐by‐pixel analysis. Early enhancement intensities and fitted pharmacokinetic parameters were studied. Paraffin blocks of 71 surgically resected specimens were analyzed by immunohistochemical staining to measure microvessel counts (with CD31) and vascular endothelial growth factor (VEGF) expression levels.ResultsMRI parameters obtained from the three analysis methods showed significant correlations (P < 0.0001), but a substantial dispersion from the linear regression line was noted (r = 0.72–...
Investigative Radiology, 1991
IEEE Transactions on Medical Imaging, 1985
The conjugate gradient method incorporating the objectextent constraint is applied to image recon... more The conjugate gradient method incorporating the objectextent constraint is applied to image reconstruction of a three-dimensional object using an incomplete projection-data set. The missing information is recovered by constraining the solution with the knowledge of the outer boundary of the object-extent which may be a priori measured or known. The algorithm is derived from the least-squares criterion as an advanced version of conventional iterative reconstruction algorithms such as SIRT (Simultaneous Iterative Reconstruction Technique) and ILST (Iterative Least Squares Technique). In the case of reconstruction from noisy projection data, a method based on the minimum mean-square error criterion is also proposed. Computer simulated reconstruction images of a phantom using limited angle and number of views are presented. The result shows that the conjugate gradient method incorporating the object-extent constraining provides the fastest convergence and the least error.
Artificial Cells, Blood Substitutes, and Biotechnology, 1994
The purpose of this study was to confirm the relationship of T1 and T2 relaxation rate vs. pO2 in... more The purpose of this study was to confirm the relationship of T1 and T2 relaxation rate vs. pO2 in vivo of 19F MR signal measured from intracellular perflubron. Our work to date has demonstrated that 1/T2 is more sensitive to pO2 than 1/T1 in the in vitro environment. The advantage of 1/T2 vs. 1/T1 is the speed of measurement and sensitivity. Seven alternating T1 and T2 measurements were obtained during a continuous acquisition using the TTISS pulse sequence. An abscess model was used for the in vivo experiments where rabbits were infused with 5ml/kg Oxygent HT 10 days prior to scanning. The abscess model was used because it has been shown that perflubron accumulates in macrophages located in the abscess wall. This technique thus provided signal from the intracellular milieu. The results of this study proved that pO2 monitoring by measuring T2 of 19F is feasible and can be used in-lieu of the T1 measurement. Given that the T2 measurement is much more rapid than the T1 measurement and that T2 changes are more sensitive than T1 changes with alterations in pO2, T2 should prove to be practical and useful for monitoring transient rapid changes in pO2.