Objective and Quantitative Evaluation of Image Quality Using Fuzzy Integral: Phantom Study / 의학물리

Physical evaluations provide the basis for an objective and quantitative analysis of the image quality. Nonetheless, there are limitations in using physical evaluations to judge the utility of the image quality if the observer's subjectivity plays a key role despite its imprecise and variable nature. This study proposes a new method for objective and quantitative evaluation of image quality to compensate for the demerits of both physical and subjective image quality and combine the merits of them. The images of chest phantom were acquired from four digital radiography systems on clinic sites. The physical image quality was derived from an image analysis algorithm in terms of the contrast-to-noise ratio (CNR) of the low-contrast objects in three regions (lung, heart, and diaphragm) of a digital chest phantom radiograph. For image analysis, various image processing techniques were used such as segmentation, and registration, etc. The subjective image quality was assessed by the ability of the human observer to detect low-contrast objects. Fuzzy integral was used to integrate them. The findings of this study showed that the physical evaluation did not agree with the subjective evaluation. The system with the better performance in physical measurement showed the worse result in subjective evaluation compared to the other system. The proposed protocol is an integral evaluation method of image quality, which includes the properties of both physical and subjective measurement. It may be used as a useful tool in image evaluation of various modalities.

Contrast Enhancement for X-ray Images Based on Combined Enhancement of Scaling and Wavelet Coefficients / 의학물리

An applied technique of contrast enhancement for X-ray image is proposed which is based on combined enhancement of scaling and wavelet coefficients in discrete wavelet transform space. Conventional contrast enhancement methods such as contrast limited adaptive histogram equalization (CLAHE), multi-scale image contrast amplification (MUSICA) and gamma correction were applied on scaling coefficients to enhance the contrast of an original. In order to enhance the detail as well as reduce the blurring caused by up scaling of contrast modified scale coefficients from lower resolution, the sigmoid manipulation function was used to manipulate wavelet coefficients. The contrast detail mammography (CDMAM) phantom was imaged and processed to measure the image line profile of results and contrast to noise ratio (CNR) comparatively. The proposed technique produced better results than direct application of various contrast enhancement methods on image itself. The proposed method can enhance contrast, and also suppress the amplification of noise components in a single process. It could be useful for various applications in medical, industrial and graphical images where contrast and detail are of importance.

Image Enhancement and Clinical Evaluation in Digital Chest Radiography / 의학물리

The aim of this study is to suggest the method for image enhancement of digital chest radiograph and evaluate clinically the quality of the resultant image. A nonlinear iterative filter was developed in order to reduce quantum noise preserving edge. Dynamic range was adjusted and adaptive image enhancement was performed based on the property of anatomic region and the degree of compatibility with neighboring pixels. The lung fields were enhanced appropriately to visualize effectively vascular tissue, bronchus and lung tissue with the desired mediastinum enhancement. Clinic evaluation was performed by three radiologists with at least 8 years experience. The anatomic regions of 11 in PA and 9 in Lateral were observed carefully in each 100 radiographs according to ITU (International Telecommunication Union) recommendation 500 protocol. The result showed the mean 3.4 between good and adequate. This means that the clinical utility of the image quality is enough. In this study, image enhancement was carried out considering image display device and human perceptual system to prevent the loss of useful anatomic information. In order to increase the diagnostic accuracy in digital radiograph, the continuous study on image enhancement is needed.

Retraction: Metabolic Alterations in Parkinson's Disease after Thalamotomy, as Revealed by 1H MR Spectroscopy

No Abstract Available.

Determination of Appropriate Sampling Frequency and Time of Multiple Blood Sampling Dual Exponential Method with 99mTc-DTPA for Calculating GFR / 핵의학분자영상

PURPOSE: To determine appropriate sampling frequency and time of multiple blood sampling dual exponential method with 99mTc-DTPA for calculating glomerular filtration rate (GFR). MATERIALS AND METHODS: Thirty four patients were included in this study. Three mCi of 99mTc-DTPA was intravenously injected and blood sampling at 9 different times, 5ml each, were done. Using the radioactivity of serum, measured by gamma counter, the GFR was calculated using dual exponential method and corrected with the body surface area. Using spontaneously chosen 2 data points of serum radioactivity, 15 collections of 2-sample GFR were calculated. And 10 collections of 3-sample GFR and 12 collections of 4-sample GFR were also calculated. Using the 9-sample GFR as a reference value, degree of agreement was analyzed with Kendall's tau correlation coefficients, mean difference and standard deviation. RESULTS: Although some of the 2-sample GFR showed high correlation coefficient, over or underestimation had evolved as the renal function change. The 10-120-240 min 3-sample GFR showed a high correlation coefficient (tau=0.93), minimal difference (Mean+/-SD=-1.784+/-3.972), and no over or underestimation as the renal function changed. The 4-sample GFR showed no better accuracy than the 3-sample GFR. CONCLUSIONS: In the wide spectrum of renal function, the 10-120-240 min 3-sample GFR could be the best choice for estimating the patients' renal function.

Quantitative Evaluation of Regional Cerebral Blood Flow by Visual Stimulation in 99mTc - HMPAO Brain SPECT / 대한핵의학회잡지

No abstract available.

Metabolic Alterations in Parkinson's Disease after Thalamotomy, as Revealed by 1H MR Spectroscopy

OBJECTIVE: To determine, using proton magnetic resonance spectroscopy (1H MRS) whether thalamotomy in patients with Parkinson's disease gives rise to significant changes in regional brain metabolism. MATERIALS AND METHODS: Fifteen patients each underwent stereotactic thalamotomy for the control of medically refractory parkinsonian tremor. Single-voxel 1H MRS was performed on a 1.5T unit using a STEAM sequence (TR/TM/TE, 2000/14/20 msec), and spectra were obtained from substantia nigra, thalamus and putamen areas, with volumes of interest of 7-8ml, before and after thalamotomy. NAA/Cho, NAA/Cr and Cho/Cr metabolite ratios were calculated from relative peak area measurements, and any changes were recorded and assessed. RESULTS: In the substantia nigra and thalamus, NAA/Cho ratios were generally low. In the substantia nigra of 80% of patients (12/15) who showed clinical improvement, decreased NAA/Cho ratios were observed in selected voxels after thalamic surgery (p < 0.05). In the thalamus of 67% of such patients (10/15), significant decreases were also noted (p < 0.05). CONCLUSION: Our results suggest that the NAA/Cho ratio may be a valuable criterion for the evaluation of Parkinson's disease patients who show clinical improvement following surgery. By highlighting variations in this ratio, 1H MRS may help lead to a better understanding of the pathophysiologic processes occurring in those with Parkinson's disease.

Transmission Dose Estimation Algorithm for Irregularly Shaped Radiation Field / 대한방사선종양학회지

PURPOSE: Measurement of transmission dose is useful for in vivo dosimetry. In this study, the algorithm for estimating the transmission dose for open radiation fields was modified for application to partially blocked radiation fields. MATERIALS AND METHODS: The beam data was measured with a flat solid phantom with various blocked fields. A new correction algorithm for partially blocked radiation field was developed from the measured data. This algorithm was tested in some settings simulating clinical treatment with an irregular field shape. RESULTS: The correction algorithm for the beam block could accurately reflect the effect of the beam block, with an error within +/-1.0%, with both square fields and irregularly shaped fields. CONCLUSION: This algorithm can accurately estimate the transmission dose in most radiation treatment settings, including irregularly shaped field.

Transmission Dose Estimation Algorithm for Tissue Deficit / 대한방사선종양학회지

PURPOSE: Measurement of transmission dose is useful for in vivo dosimetry. In this study, previous algorithm for estimation of transmission dose was modified for use in cases with tissue deficit. MATERIALS AND METHODS: The beam data was measured with flat solid phantom in various conditions of tissue deficit. New algorithm for correction of transmission dose for tissue deficit was developed by physical reasoning. The algorithm was tested in experimental settings with irregular contours mimicking breast cancer patients using multiple sheets of solid phantoms. RESULTS: The correction algorithm for tissue deficit could accurately reflect the effect of tissue deficit with errors within +-1.0% in most situations and within +-3.0% in experimental settings with irregular contours mimicking breast cancer treatment set-up. CONCLUSION: Developed algorithm could accurately reflect the effect of tissue deficit and irregularly shaped body contour on transmission dosimetry.

Development of Program for Renal Function Study with Quantification Analysis of Nuclear Medicine Image / 대한핵의학회잡지

PURPOSE: In this study, we developed a new software tool for the analysis of renal scintigraphy which can be modified more easily by a user who needs to study new clinical applications, and the appropriateness of the results from our program was studied. MATERIALS AND METHODS: The analysis tool was programmed with IDL5.2 and designed for use on a personal computer running Windows. For testing the developed tool and studying the appropriateness of the calculated glomerular filtration rate (GFR), 99mTc-DTPA was administered to 10 adults in normal condition. In order to study the appropriateness of the calculated mean transit time (MTT), 99mTc-DTPA and 99mTc-MAG3 were administered to 11 adults in normal condition and 22 kidneys were analyzed. All the images were acquired with ORBITOR, the Siemens gamma camera. RESULTS: With the developed tool, we could show dynamic renal images and time activity curve (TAC) in each ROI and calculate clinical parameters of renal function. The results calculated by the developed tool were not different statistically from the results obtained by the Siemens application program (Tmax: p=0.68, Relative Renal Function: p=1.0, GFR: p=0.25) and the developed program proved reasonable. The MTT calculation tool proved to be reasonable by the evaluation of the influence of hydration status on MTT. CONCLUSION: We have obtained reasonable clinical parameters for the evaluation of renal function with the software tool developed in this study. The developed tool could prove more practical than conventional, commercial programs.

Calculation of Renal Depth by Conjugate - View Method Using Dual - head Gamma Camera / 대한핵의학회잡지

No abstract available.

High Resolution MR Images from 3T Active-Shield Whole-Body MRI System

PURPOSE: Within a clinically acceptable time frame, we obtained the high resolution MR images of the human brain, knee, foot and wrist from 3T whole-body MRI system which was equipped with the world first 3T active shield magnet. MATERIALS AND METHODS: Spin echo (SE) and Fast Spin Echo (FSE) images were obtained from the human brain, knee, foot and wrist of normal subjects using a homemade birdcage and transverse electromagnetic (TEM) resonators operating in quadrature and tuned to 128 MHz. For acquisition of MR images of knee, foot and wrist, we employed a homemade saddle shaped RF coil. Typical common acquisition parameters were as follows: matrix= 512x512, field of view (FOV) = 20 cm, slice thickness = 3 mm, number of excitations (NEX) = 1. For T1-weighted MR images, we used TR= 500 ms, TE = 10 or 17.4 ms. For T2-weighted MR images, we used TR=4000 ms, TE = 108 ms. RESULTS: Signal to noise ratio (SNR) of 3T system was measured 2.7 times greater than that of prevalent 1.5T system. MR images obtained from 3T system revealed numerous small venous structures throughout the image plane and provided reasonable delineation between gray and white matter. CONCLUSION: The present results demonstrate that the MR images from 3T system could provide better diagnostic quality of resolution and sensitivity than those of 1.5T system. The elevated SNR observed in the 3T high field magnetic resonance imaging can be utilized to acquire images with a level of resolution approaching the microscopic structural level under in vivo conditions. These images represent a significant advance in our ability to examine small anatomical features with noninvasive imaging methods.

Neuronal Dysfunction in Patients with Chronic Alcoholism Evaluated by In Vivo 1H Magnetic Resonance Spectroscopy

PURPOSE: With the use of localized, water-suppressed in vivo 1H magnetic resonance spectroscopy (MRS), we evaluated the proton metabolic alterations in patients with chronic alcoholism and healthy normal controls. MATERIALS AND METHODS: Patients with chronic alcoholism (N=10) and normal control subjects (N=10) underwent MRS examinations using a stimulated echo acquisition mode (STEAM) pulse sequence with 2X2X2 cm3 volume of interest (VOI) in the left cerebellum and basal ganglia. Proton metabolite ratios relative to creatine (Cr) were obtained using a Marquart algorithm. RESULTS: The specific feature in patients with chronic alcoholism was a significant decrease of N-acetylaspartate (NAA)/Cr ratio in the left cerebellum, compared with normal controls. No clear correlation of other metabolite ratios such as choline (Cho)/Cr and inositols (Ins)/Cr was established. CONCLUSION: Our preliminary study suggests that the reduction of NAA/Cr ratio may indicate neuronal loss in patients with chronic alcoholism. Thus, in vivo 1H MRS may be a useful modality in the clinical evaluation of patients with chronic alcoholism based on the proton metabolite ratios.

Metabolic Abnormalities in Patients with Mitochondrial Myopathy Evaluated by In Vivo 31P Magnetic Resonance Spectroscopy

PURPOSE: To investigate the phosphorus metabolic abnormalities in skeletal muscle of patients with mitochondrial myopathy using in vivo 31P magnetic resonance spectroscopy(MRS). MATERIAL AND METHODS: Patients with mitochondrial myopathy(N=10) and normal control subjects (N=10) participated. All in vivo 31P MRS examinations were performed on 1.5T whole-body MRI/MRS system by using an image selected in vivo spectroscopy (ISIS) pulse sequence that provided a 4 X 4 X 4 cm3 volume of interest (VOI) in the right thigh muscle tissue. Peak areas for each phophorus methabolite were measured using a Marquart algorithm. RESULTS: The specific features in patients with mitochondrial myopathy were a significant increase of Pi/PCr ratio (p=0.003) and a significant decrease of ATP/PCr ratio (p=0.004) as compared with normal controls. In particular, the beta-ATP/PCr ratio between controls and patients with mitochondrial myopathy was predominantly altered. CONCLUSIONS: In vivo 31P MRS may be a useful modality in the clinical evaluation of patients with mitochondrial myopathy based on ATP/PCr and Pi/PCr ratios in skeletal muscle tissue and provides a valuable information in further understanding disorders of muscle metabolism.