• Progress in Medical Physics
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• v.24 no.3
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• pp.198-203
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• 2013

Generally, to evaluate gated radiation therapy, moving phantoms are used to simulate organ motion. Since the target moves in every direction, we need to take into account motion in each direction. This study proposes methods to evaluate gated radiation therapy using gamma index analysis and to visualize adequate gating window sizes according to motion ranges. The moving phantom was fabricated to simulate motion in the craniocaudal direction. This phantom consisted of a moving platform, the I'm MatriXX, and solid water phantoms. A 6 MV photon filed with a field size of $4{\times}4cm^2$ was delivered to the phantom using the gating system, while the phantom moved in the 1-, 2-, 3-, 4-, and 5-cm motion ranges. The gating windows were set at 40~60%, 30~40%, and 0~90%, respectively. The I'm MatriXX acquired the dose distributions for each scenario and the dose distributions were compared with a $4{\times}4cm^2$ static filed. The tolerance of the gamma index was set at 3%/3 mm. The greater the gating window, the lower the pass rate, and the greater the motion range, the lower the pass rate in this study. In case treatment without gated radiation therapy for the target with motion of 2 cm, the pass rate was less than 96%. But it was greater than 99% when gated radiation therapy was used. However gated radiation therapy was used for the target with motion greater than 4 cm, the pass rate could not be greater than 97% when gating window was set as 30~70%. But when the gating window set as 40~60%, the pass rate was greater than 99%.

• Investigative Magnetic Resonance Imaging
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• v.16 no.2
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• pp.115-123
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• 2012

Purpose : To evaluate white matter abnormalities on diffusion tensor imaging (DTI) in patients with mild Alzheimer disease (AD) and mild cognitive impairment (MCI), using tract-based spatial statistics (TBSS) and voxel-based morphometry (VBM). Materials and Methods: DTI was performed in 21 patients with mild AD, in 13 with MCI and in 16 old healthy subjects. A fractional anisotropy (FA) map was generated for each participant and processed for voxel-based comparisons among the three groups using TBSS. For comparison, DTI data was processed using the VBM method, also. Results: TBSS showed that FA was significantly lower in the AD than in the old healthy group in the bilateral anterior and right posterior corona radiata, the posterior thalamic radiation, the right superior longitudinal fasciculus, the body of the corpus callosum, and the right precuneus gyrus. VBM identified additional areas of reduced FA, including both uncinates, the left parahippocampal white matter, and the right cingulum. There were no significant differences in FA between the AD and MCI groups, or between the MCI and old healthy groups. Conclusion: TBSS showed multifocal abnormalities in white matter integrity in patients with AD compared with old healthy group. VBM could detect more white matter lesions than TBSS, but with increased artifacts.

• Investigative Magnetic Resonance Imaging
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• v.18 no.4
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• pp.303-313
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• 2014

Purpose : In-vivo conductivity reconstruction using transmit field ($B_1{^+}$) information of MRI was proposed. We assessed the accuracy of conductivity reconstruction in the presence of statistical noise in complex $B_1{^+}$ map and provided a parametric model of the conductivity-to-noise ratio value. Materials and Methods: The $B_1{^+}$ distribution was simulated for a cylindrical phantom model. By adding complex Gaussian noise to the simulated $B_1{^+}$ map, quantitative conductivity estimation error was evaluated. The quantitative evaluation process was repeated over several different parameters such as Larmor frequency, object radius and SNR of $B_1{^+}$ map. A parametric model for the conductivity-to-noise ratio was developed according to these various parameters. Results: According to the simulation results, conductivity estimation is more sensitive to statistical noise in $B_1{^+}$ phase than to noise in $B_1{^+}$ magnitude. The conductivity estimate of the object of interest does not depend on the external object surrounding it. The conductivity-to-noise ratio is proportional to the signal-to-noise ratio of the $B_1{^+}$ map, Larmor frequency, the conductivity value itself and the number of averaged pixels. To estimate accurate conductivity value of the targeted tissue, SNR of $B_1{^+}$ map and adequate filtering size have to be taken into account for conductivity reconstruction process. In addition, the simulation result was verified at 3T conventional MRI scanner. Conclusion: Through all these relationships, quantitative conductivity estimation error due to statistical noise in $B_1{^+}$ map is modeled. By using this model, further issues regarding filtering and reconstruction algorithms can be investigated for MREPT.

• Investigative Magnetic Resonance Imaging
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• v.18 no.4
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• pp.323-331
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• 2014

Purpose : To assess the usefulness of rectal filling using ultrasonographic gel in patients with lower rectal cancer. Materials and Methods: Twenty five patients with lower rectal cancer were enrolled. High resolution pelvic MR was performed twice before and after gel filling. Independently and retrospectively, two radiologists reviewed each set of MR images using five-grade scales for sphincter involvement, CRM (circumferential resection margin) involvement and depiction of the tumor. Same two radiologists retrospectively performed consensus review of each set of MR images for tumor distance from the anal verge and T&N staging. Results: Tumor depiction scores from MR with gel filling were significantly higher than those of MR without distention (p<0.001). Compared to MR without distension, MR with gel filling had no significant differences in prediction of CRM or sphincter involvement (p>0.05). Distance from the anal verge was significantly different between MR with gel filling and rigid endoscopy ($6.8{\pm}1.6cm$ vs. $5.8{\pm}1.6cm$, p=0.001). There were no significant differences between pathological staging and MR staging with or without gel filling. Conclusion: MR with gel filling improved tumor depiction. And also MR with gel filling revealed same ability for the predictions of CRM or sphincter invasion in patients with lower rectal cancer, comparing with MR without gel filling.

• Investigative Magnetic Resonance Imaging
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• v.18 no.4
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• pp.314-322
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• 2014

Purpose: Diastolic dysfunction is a common problem in patients with hypertrophic cardiomyopathy (HCM). The purpose of this study was to assess the role of MRI in the assessment of diastolic function using mitral valve and pulmonary vein flow velocities in HCM patients. Methods and Results: Phase-contrast MRI (mitral valve and pulmonary vein) and transthoracic echocardiography was successfully performed for 59 HCM patients (44 men and 15 women; mean age, 51 years). Forty-nine patients had a diastolic dysfunction; grade 1 (n = 20), grade 2 (n = 27), and grade 3 (n = 2) using echocardiography, and ten patients had normal diastolic function. The transmitral inflow parameters (E, A, and E/A ratios) obtained by MRI showed positive correlation with the same parameters measured by echocardiography (Pearson's r values were 0.47, 0.60, and 0.75 for E, A, E/A, respectively, all P < 0.001). With the flow information of the pulmonary vein from cardiac MRI, pseudo-normalized pattern (n = 8) could be distinguished from true normal filling pattern (n = 17), and the diastolic function grades by cardiac MRI showed moderate agreement with those of echocardiography (kappa value = 0.45, P < 0.001). Conclusions: Assessment of left ventricle diastolic function is feasible using phase-contrast MRI in HCM patients. Analysis of pulmonary vein flow velocity on MRI is useful for differentiating pseudo-normal from normal diastolic function in HCM patients.

• Nuclear Medicine and Molecular Imaging
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• v.40 no.6
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• pp.302-308
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• 2006

Purpose: Although several neuroanatomical models of panic disorder have been proposed, little is known regarding the neurological mechanisms underlying cognitive-behavioral therapy (CBT) in patients with panic disorder. This study was performed to identify the brain structures that show changes of regnioal cerebral blood flow (rCBF) after CBT in patients with panic disorder. Materials and Methods: Seven patients who were diagnosed as panic disorder by DSM-IV were treated with CBT for 8 weeks and twelve healthy volunteers joined in this study. Serial $^{99m}Tc-ECD$ brain perfusion SPECT images were acquisited and PDSS-SR (Self-Report version of Panic Disorder Severity Scale) and ACQ (Agoraphobic Cognitive Question) scores were measured just before and after CBT in all patients. Data were analyzed using SPM2. Results: Subjective symptoms were improved, and PDSS-SR and ACQ scores were significantly reduced ($14.9{\pm}3.9\;vs.\;7.0{\pm}1.8$, p<0.05; $30.3{\pm}8.5\;vs.\;21.6{\pm}3.4$, p<0.05, respectively) after CBT in panic patients. Before CBT, a significant increase of rCBF was found in the cingulate gylus, thalamus, midbrain, both medial frontal and temporal lobes of the panic patients compared to the normal volunteers. After CBT, we observed a significant rCBF decrease in the left parahippocamus, right insula and cingulate gyrus, both frontal and temporal lobes, and a significant rCBF increase in both the occipital lobes, left insula, both frontal and left parietal lobes. Conclusion: These data suggested that CBT is effective for panic disorder and diminish the activity of the brain areas associated with fear in panic disorder.

• Nuclear Medicine and Molecular Imaging
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• v.40 no.6
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• pp.309-315
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• 2006

Purpose: Accurate evaluation of cervical lymph node (LN) metastasis of head and neck squamous cell canter (SCC) is important to treatment planning. We evaluated the diagnostic accuracy of F-18 fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) for the detection of cervical LN metastasis of head and neck SCC and performed a retrospective comparison with CT/MRI findings. Materials & Methods: Seventeen patients with pathologically proven head and neck SCC underwent F-18 FDG PET/CT and CT/MRI within 4 week before surgery. We recorded lymph node metastases according to the neck level system of imaging-based nodal classification. F-18 FDG PET/CT images were analyzed visually for assessment of regional tracer uptake in LN. We analyzed the differences in sensitivity and specificity between F-18 FDG PET/CT and CT/MRI using the Chi-square test. Results: Among the 17 patients, a total of 123 LN levels were dissected, 29 of which showed metastatic involvement. The sensitivity and specificity of F-18 FDG PET/CT for detecting cervical LN metastasis on a level-by-level basis were 69% (20/29) and 99% (93/94). The sensitivity and specificity of CT/MRI were 62% (18/29) and 96% (90/94). There was no significant difference in diagnostic accuracy between F-18 FDG PET/CT and CT/MRI. Interestingly, F-18 FDG PET/CT detected double primary tumor (hepatocellular carcinoma) and rib metastasis, respectively. Conclusion: There was not statistically significant difference of diagnostic accuracy between F-18 FDG PET/CT and CT/MRI for the detection of cervical LN metastasis of head and neck SCC. The low sensitivity of F-18 FDG PET/CT was due to limited resolution for small metastatic deposits.

• Clinical and Experimental Pediatrics
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• v.48 no.12
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• pp.1324-1329
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• 2005

Purpose : The aim of this study was to evaluate recent improvements in the survival rate of extremely low birth weight (ELBW) infants and to identify perinatal and management factors that are associated with improved survival. Methods : Two groups of ELBW infants who were admitted to our neonatal intensive care unit (NICU) during two distinct eras : November 1994-December 1999 (Period 1 : n=100) and January 2000-April 2004 (Period 2 : n=166) were retrospectively reviewed. Results : Despite the younger gestational age and smaller birth weight of the ELBW infants in period 2, not only did their survival rate increased to 75 percent from 60 percent in period 1, but their incidence of morbidities such as bronchopulmonary dysplasia, confimed sepsis and intraventricular hemorrhage (${\geq}$Grade III) also declined. Factors significantly associated with improved survival included the use of antenatal steroids, a longer duration of nasal continuous positive airway pressure and the absence of intraventricular hemorrhage (${\geq}$Grade III). Conclusion : We believe that optimized clinical practice, that emphasized less invasive care, contributed to the recent improvements in the survival rate of ELBW infants.

• Clinical and Experimental Pediatrics
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• v.53 no.2
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• pp.195-202
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• 2010

Purpose : Despite recent advances in pulmonary hypertension management and surgery, appropriate guidelines remain to be developed for operability in congenital heart disease with pulmonary artery hypertension (PAH). Our aim was to evaluate clinical outcomes of patients with severe PAH who underwent surgical closure of left-to-right shunt lesions (LRSL) on the basis of pulmonary reactivity. Methods : We retrospectively reviewed 21 patients who underwent surgical closure of LRSL with severe PAH (${\geq}8$ Wood unit) from January 1995 to April 2009. The median age at operation was 26 years. Atrial septal defect, ventricular septal defect (VSD), VSD and patent ductus arteriosus (PDA), and PDA was present in 11, 4, 4, and 2 patients, respectively. Results : Operability was based on vasoreactivity of PAH. Of the 21 patients, 5 showed response to pulmonary vasodilator therapy and 8 showed vasoreactivity after balloon occlusion of defects. The remaining 8 patients were considered operable because of significant left-to-right shunt (Qp/Qs ${\geq}1.5$). Five patients underwent total closure of defects and 16 were left with small residual shunts. The median follow-up duration was 32 months. There was no significant postoperative mortality or morbidity. Systolic pulmonary artery pressure (PAP) decreased in all but 2 patients. All patients except 1 showed improvement of New York Heart Association functional class. Conclusion : Closure of LRSL in patients with severe PAH on the basis of pulmonary vasoreactivity seems reasonable. PAP and clinical symptoms improved in most patients. Further research is needed for the evaluation of long-term results.

• Clinical and Experimental Pediatrics
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• v.52 no.3
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• pp.303-309
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• 2009

Purpose : To identify the short-term clinical outcomes of late preterm infants and to test the hypothesis that late preterm infants have more clinical problems during the early postnatal period than term infants. Methods : One hundred late preterm infants [gestational age (GA) $34^{+0}$-$36^{+6}$ weeks] and the same number of term infants (GA $37^{+0}$-$41^{+6}$ weeks) were randomly selected from 289 late preterm infants and 825 term infants born in the Seoul National University Bundang Hospital between January 2007 and December 2007, and their electronic medical records were reviewed and analyzed. Results : Compared to term infants, late preterm infants had significantly more medical problems such as temperature instability (odds ratio [OR] 8.7), hypoglycemia (OR 17.5), intravenous fluid infusion (OR 10.2), evaluation for sepsis (OR 9.4), respiratory problems (OR 7.5), apnea and bradycardia (OR 8.6), phototherapy for jaundice (OR 3.6), and feeding intolerance (OR 10.0). Hospital stay was also significantly longer in late preterm infants. Conclusion : Late preterm infants had significantly more medical problems and increased length of hospital stay compared to term infants. More attention should be given to caring for these late preterm infants in newborn nursery during the early postnatal period.